Available via license: CC BY-NC-ND 4.0
Content may be subject to copyright.
1
Date of publication xxxx 00, 0000, date of current version xxxx 00, 0000.
Digital Object Identifier ……………
Review of Electric Vehicle Charging
Technologies, Standards, Architectures, and
Converter Configurations
SITHARA S. G. ACHARIGE1, Student Member, IEEE,
MD ENAMUL HAQUE1, Senior Member, IEEE,
MOHAMMAD TAUFIQUL ARIF1, Member, IEEE,
NASSER HOSSEINZADEH1, Senior Member, IEEE,
KAZI N. HASAN2, Member, IEEE
AMAN MAUNG THAN OO1, Senior Member, IEEE,
1School of Engineering, Deakin University, Waurn Ponds, VIC 3216, Australia
2School of Engineering, RMIT University, Melbourne, VIC 3000, Australia
Corresponding author: Sithara S. G. Acharige (sgalwaduacharig@deakin.edu.au).
ABSTRACT Electric Vehicles (EVs) are projected to be one of the major contributors to energy transition
in global transportation due to their rapid expansion. High-level of EVs integration into the electricity grid
will introduce many challenges for the power grid planning, operation, stability, standards, and safety.
Therefore, the wide-scale adoption of EVs imposes research and development of charging systems and EV
supply equipment (EVSE) to achieve expected charging solutions for EV batteries as well as to improve
ancillary services. Analysis of the status of EV charging technologies is important to accelerate EV adoption
with advanced control strategies to discover a remedial solution for negative impacts and to enhance desired
charging efficiency and grid support. This paper presents a comprehensive review of EV charging
technologies, international standards, the architecture of EV charging stations, and the power converter
configurations of EV charging systems. The charging systems require a dedicated converter topology, a
control strategy, compatibility with standards, and grid codes for charging and discharging to ensure optimum
operation and enhance grid support. An overview of different charging systems in terms of onboard and off-
board chargers, AC-DC and DC-DC converter configuration, and AC and DC-based charging station
architectures are evaluated. In addition, recent charging systems which are integrated with renewable energy
sources are presented to identify the power train of modern charging stations. Finally, future trends and
challenges in EV charging and grid integration issues are summarized as the future direction of the research.
INDEX TERMS Electric vehicle, charging configuration, grid integration, international standards, onboard
and offboard charger, power converters.
I. INTRODUCTION
Electrification has become a major factor in social
development, economic growth, and environmental
contribution. Accordingly, electrification is projected to
increase further into the transport sector focusing on the
energy transition towards a zero-carbon emission economy.
Electrified transportation is considered a desirable solution
to reduce fossil fuel dependence and environmental impacts
such as reducing greenhouse gas (GHG) emissions, climate
change, and improving air quality. Electric vehicles (EVs)
offer zero-emission, highly reliable, efficient, and low-
maintenance vehicles compared to conventional internal
combustion engine (ICE) vehicles [1]. Moreover, EVs will
open the possibility of using alternative energy systems such
as renewable energy sources (RESs) and energy storage
systems (ESSs) to secure mobility and make road transport
more independent from fossil fuels. The deployment of EVs
will depend on a driving range, model, performance, costs of
batteries, the convenience of re-charging, safety perception,
and possible implied driving habits [2]. The charging time
needs to be matched to the time required to refuel conventional
ICE vehicles, and EV supply equipment (EVSE) needs to
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
2
extend with higher power levels for ultra-fast charging. Smart
charging coordinated control techniques, and high-power
converters can be used to reduce the charging time. Therefore,
many research studies have established advanced control
strategies, architectures, and converter topologies for EV
charging systems.
EV charging technologies can be evaluated based on the
charging method of battery, power flow direction, onboard or
offboard chargers, or power supply technique depending on
requirement and location. The basic units of EV charging
system are EV supply equipment (EVSE) which accesses
power between EV and local electricity supply. Onboard or
offboard chargers are used for grid integration of EVs via AC
or DC power. Furthermore, EV charging systems have
designed unidirectional or bidirectional power flow. Most
commercial onboard chargers are equipped with
unidirectional power flow, which is grid-to-vehicle (G2V)
capabilities due to simplicity, reliability, low cost, and simple
control strategy. In contrast, bidirectional chargers can inject
power into the utility grid through vehicle-to-grid (V2G)
mode. Hence, bidirectional chargers are considered active
distributed resources with specific control modes to support
load leveling, RES integration, and reduce power losses in the
utility grid. Therefore, academics are becoming more
interested in bidirectional chargers as a potential option for
EVs in the future.
Modern EV chargers are integrated with smart charging
algorithms to enable optimum charging/discharging and
dynamic power sharing by communicating with EVs and the
utility grid to improve the energy efficiency of chargers and
decrease pressure on the local power grid. EV charging
systems have been designed according to specific international
standards to be compatible on both sides of the EV and the
utility grid. Recently, many international standards and codes
regarding EV charging and utility interface have been
introduced to achieve widespread EV acceptance and reliable
grid operation. International organizations have established
various standards and codes, universal structures, associated
peripheral devices, and user-friendly software for EV charging
systems. Charging systems can be categorized into four groups
based on the power level and four modes based on the
application. Moreover, electrical, and physical parameters and
communication protocol standards are defined by IEC and
SAE organizations [3]. Fast-charging standards for AC and
DC charging have recently been improved significantly by
IEEE, IEC, and SAE organizations [4]. Generally preferred
standards in the field of EV charging are described in the
technical report in [5]. Moreover, government policies and
standards for EVs have been introduced internationally to
ensure reliable grid operation and mitigate negative impacts
on the distribution grid [6].
The architecture of charging stations rapidly improves as
the range of BEVs increases. Charging methods can be
classified as conductive, inductive, or wireless and battery
swapping. Onboard and offboard chargers have developed
with conductive charging either using AC or DC power.
Charging of EV battery packs depends on the rate of transfer
power from the charging station. Therefore, fast and ultra-fast
charging stations gain attention as they can charge the battery
in less time at high power levels [7]. EV charging units are
connected to the AC bus through separate rectifiers in
common AC bus-based architecture. In contrast, common DC
bus-based charging systems are flexible structures and
comprise with single rectifier with high power levels on the
grid side. Moreover, hybrid AC/DC and micro-grid charging
architectures with RES have been designed to maximize RES
energy use and improve micro-grid performance other than
EV applications. Consequently, researchers have focused on
improving charging stations with advanced converters and
smart control techniques to manage public charging
constraints.
The EV charging systems are comprised of several AC/DC
power converters and control strategies to safely charge the
battery with high efficiency. The AC-DC and DC-DC
converters are employed to deliver power either unidirectional
or bidirectional in the charging systems. The cost, size,
performance, and efficiency of the charging system depend on
the corresponding converter topology. High-power converters
can be used to reduce the charging time which enhances
ancillary services to the power grid. However, the increasing
fleet of EVs and renewable energy sources (RES) in the
distribution grid inject harmonics and deteriorates power
quality and may cause an impact on grid operation, safety, and
reliability. Therefore, different power converters, charging
strategies, and grid integration techniques are being developed
to strengthen the advantages of EVs. Integrated challenges of
plug-in hybrid electric vehicles (PHEV) and EV charging
infrastructures are assessed through the various optimization
techniques in [8]. Various optimization techniques have been
evaluated in [9] for charging infrastructures with the aim of
power loss, peak load and cost of electricity minimization.
Authors in [10] discussed the performances of various bio-
inspired computational intelligence techniques for EV
charging optimization.
Therefore, a comprehensive review of EV charging
technologies, standards, architectures, and converter
configurations is important to identify prevailing challenges
and propose remedial solutions. Most EV charging stations are
AC power-based configurations as they have mature
technology and direct usage of local loads when compared to
the DC power-based fast charging stations. On the other hand,
DC power-based architectures are becoming popular in recent
years due to their high efficiency, low cost, and flexibility to
integrate RESs and ESS in the distribution grid. However,
complexity is increased with additional energy sources in DC
power-based charging stations. Hence, EV charging
technologies, configurations, and architectures need to be
analyzed comprehensively to identify the current state of EV
charging systems, technical development, and challenges to
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
3
identify a remedial solution. The following contributions are
made in this paper.
• The Overview of the current state of EV charging
technologies and requirements including different types
of EVs, charging levels, modes, and connectors.
• Standards of EV charging, grid integration codes and
safety standards.
• Architectures of EV charging stations based on AC and
DC power-driven, and RES-based systems.
• Configurations of converter topology including onboard
and offboard, AC-DC converters and DC-DC converters
are reviewed comprehensively with the associated
powertrain.
The rest of the paper is organized as follows. The overview of
EV charging technologies is presented in section 2 including
the status of charging technologies and requirements such as
different types of EVs, charging levels, modes, connectors,
and types of EV batteries. The international standards of EV
charging and grid integration are reviewed in section 3. In
section 4, different architectures of EV charging stations are
elaborated with conventional, and RES-based charging
stations. EV charging topologies are reviewed in section 5
including G2V and V2G operation and onboards and offboard
chargers. Power converter configurations of EV chargers are
presented in section 6 based on the AC-DC and DC-DC
converters and isolated and non-isolated converters. Finally,
future trends and challenges of EV are discussed in section 6,
and the conclusion is drawn in section 7.
II. ELECTRIC VEHICLE CHARGING TECHNOLOGIES
Electrified transportation is achieving momentum in the
current industry due to many factors, including clean
environmental concepts, fossil fuel depletion, government
subsidies, increasing charging infrastructures, and smart
control propulsion strategies. Moreover, the widespread
availability of fast charging stations will start a movement
where EV charging will become as common as refueling ICE
vehicles at existing service stations. This section explains an
overview of EV charging technologies including the current
state of EV charging technologies, different types of EVs,
charging levels, modes, and different connector types and
types of EV batteries.
A. CURRENT STATE OF EV CHARGING TECHNOLOGY
In 2021, global EV sales doubled from the previous year to
a record of 6.6 million. The global electric car sales were 2
million in the first quarter of 2022, up 75% from the same
duration in 2021 [12]. The projections indicate that the global
EV fleet will reach 230 million vehicles in 2030 and 58% of
vehicles are expected to be EVs in 2040 [13]. The global EV
stock is significantly increased in 2021 when compared to the
previous years and the total number of battery electric cars on
road to over 16.5 million. As shown in Fig. 1, the largest EV
market belongs to China where cumulative EV sales reached
9.4 million in 2021, which represented 50% of global EV
stock [14]. The second largest EV market belongs to Europe
with 2.3 million annual sales of light duty EVs and the United
States has the third largest EV market [12], [15]. Currently,
electrified transportation has attracted much attention from
governments and private stakeholders to move towards carbon
neutrality in 2040 through consistent policy support,
incentives, and subsidies from the governments.
Several major automobile manufacturers are preparing for
a shift to EVs and some jurisdictions and countries, including
Europe and China, are planning to restrict fossil fuel-powered
vehicle sales in the future [16]. The exponential growth of EV
sales will be expected along with the facilitation of increasing
high-charging equipment accessibility, public fast charging
stations, and the development of RES-based EV charging.
Most of the projects and developments are focused on the RES
power changing infrastructures to make further advantages
from EVs while supporting grid operations [17]. As a result,
the carbon footprint declines, and additional grid support is
provided by EVs through charging systems. The adoption of
EVs is the consequence of much regulatory assistance in the
present day, such as purchase incentives, subsidies for home
charging insulation, benefits for drivers and parking,
orchestration of international standards, and expanded access
to public charging infrastructure [18].
Battery technology has a significant impact on the growth
of EVs because the price, weight, volume, charging time,
driving range and lifetime depend on the EV battery pack [19].
Extensive studies and funding have been dedicated to
developing superior battery technologies that are appropriate
for EVs at present. The cost of EV batteries has decreased
significantly from over $1000/kWh in 2010 to about
$132/kWh in 2021 [20]. Most analysts predict that the cost of
battery packs will keep declining, reaching $100/kWh
between 2023 and 2025 and $61–72/kWh by 2030 [21]. The
average capacity of a lithium-ion EV battery is around 40kWh,
and some models have 100kWh capacity. The investments in
FIGURE 1. Electric passenger car stock, 2012-2021 [11].
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
4
EVs have drastically increased to explore electrification
strategies and battery life-cycle management to increase
driving range, efficiency, and reliable charging and
discharging capabilities for an affordable price.
Technological innovations in EVs have provided new
concepts for EV grid integration, offering attractive and
competitive regulated charging/discharging techniques. [22].
The vehicle-to-grid (V2G) application is an emerging research
area, EV batteries can be used to store surplus energy and
supply energy to the utility grid using coordinated control
strategies [23]. The EVs will play a new role in the emerging
concept of smart charging technologies by exchanging energy
with microgrids and the power grid via a bidirectional power
flow with ancillary support [24]. The smart EV fleets program
encourages the integration of EVs into their transportation
system via RESs [25]. However, the rapid growth in EVs is
expected to have further negative impacts on the distribution
grid including power quality impacts, increasing peak
demand, voltage instability, harmonic distortion, and
overloading distribution grid [26]. The increased EV charging
station may change the distribution network's load patterns,
characteristics, and safety requirements. Therefore, extensive
research studies have been progressing to identify the power
network and environmental and economic impacts of EVs
[27].
B. TYPES OF ELECTRIC VEHICLES
The EV comprises one or more electric motors and a high-
voltage battery pack with a charging system. The electric
motor either assists completely via electric power or ICE
depending on the EV type. Additionally, the electric motor
functions as a generator and provides power to charge the
battery using a bidirectional DC-AC converter during the
braking and deceleration of the vehicle. Conversely, the
converter enables power to flow from the battery to the motor
during driving mode [28]. The battery pack is recharged from
electric energy through a charging system. Based on the
current phase of development, EVs are categorized into two
types: hybrid vehicles and all-electric vehicles (AEVs) by
considering the degree of use of electricity as shown in Fig. 2.
The hybrid vehicle has a conventional ICE vehicle design
and a battery to power the vehicle using fuel and electric
energy. The capacity of the battery defines the driving range
of the vehicle in electric mode. Hybrid EVs (HEVs) and plug-
in hybrid EVs (PHEVs) are two types of hybrid vehicles in the
market. The hybrid vehicle comprises ICE, an oversized
electric motor, and a battery to reduce fossil fuel consumption.
The HEVs have similar drive features to normal ICE vehicles
and can make the vehicle move using stored battery power for
short distances. The battery pack automatically chargers
through regenerative braking by turning kinetic energy into
electric energy when ICE is at a light load in HEVs [29],[30].
The propulsion mechanism of the PHEV is like the HEV, and
it differs from the HEV by having a large battery pack being
able to charge from the regenerative braking and plugs into the
power grid. The PHEV has a more powerful electric motor
than HEV, which is enabled to be operated in entirely electric
mode by turning off the ICE [31],[32]. The all-electric driving
range is about 25 km to 80+ km in PHEV depending on the
model.
AEV uses electric power as fuel to recharge the battery pack
and consists of electric motors for propulsion. AEVs produce
zero pipeline emissions as they are driven via electric power
without any fuel combustion. There are three types of AEVs
including battery EV (BEV), fuel cell EV (FCEV) and
extended-range EV (E-REV). The AEVs use a large onboard
battery pack to provide acceptable propulsion to the vehicle.
BEVs are frequently called EVs which are driven by electric
motors powered via a battery pack. The BEV is exclusively
powered by electricity and thus tends to have a large battery
capacity (kWh) when compared to hybrid vehicles as they are
relying only on electric power. The battery pack chargers by
plugging the vehicle into the power grid or electric source and
regenerative braking. The main challenges of BEV are shorter
driving range per charge, limitation of public charging
stations, and long charging period [33],[34]. Moreover, the
deployment of BEVs can support the power grid via smart
charging technologies and V2G functionality to increase
variable renewable energy and interplay with communication
technologies to minimize operational costs and maximize the
technical features of power systems.
The FCEVs are powered by hydrogen gas and the
propulsion system is the same as EVs. The FCEV uses
hydrogen gas to power an electric motor entirely by electric
power. The FCEV is refueled with hydrogen gas and the fuel
cell uses to transform the chemical power into electric energy
which drives the electric motor. The FCEV has a short
refueling time and the driving range is comparable to ICE
vehicles. Moreover, they are noise-free, very energy efficient,
and have zero tailpipe emission vehicles which produced pure
water as a waste [20]. The E-REVs comprise an electric motor
and small ICE to produce additional power which is used to
keep the battery charging for long distances. E-REVs are
categorized as AEVs with many of the benefits of purely
electric models. An E-REV comprises with electrical
drivetrain (one or more electric motors and battery pack) and
ICE to charge the battery pack. Therefore, E-REV needs to be
both recharged from the power grid and refueled at a petrol
station. The E-REV helps combat range anxiety, lower fuel
costs, and are highly efficient and maximize the use of their
vehicles by operating their engine constantly [35].
FIGURE 2. Types of electric vehicles.
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
5
The specifications of distinct types of popular EVs are
presented in Table 1 in terms of the type of vehicle, battery
capacity, driving range and connector type. The driving range
of an EV depends on the battery capacity, measured in kWh.
Hence, modern BEVs have higher battery capacity and a
driving range from 200 to 490 km on a single charge [36].
Fast and extremely fast charging stations are growing to meet
high power requirements with EVSE. On average, a usual
BEV takes about 8 hours to charge a 60kWh battery pack from
empty to full, which can cover up to 320 km of distance [37].
BEVs have comparatively less driving range than FCEVs and
E-REVs. The overall energy efficiency of EVs has been
continuously improved by manufacturers, resulting in lower
energy consumption per kilometer and longer range on a
single charge.
C.
CHARGING LEVELS AND MODES
EVs are designed with various charging technologies,
capacities, and charging and discharging strategies to fulfil
their unique requirements. Therefore, standardized charging
levels and models are established to drive EV adoption
forward in the industry. The electric powertrain of modern
plug-in EV is similar and is designed with a high-power
battery pack (to maintain voltage and current), a battery
management system, various converters to supply appropriate
voltage levels, controllers and drive inverters [43], [44]. EV
chargers can be classified as onboard and offboard chargers as
well as unidirectional and bidirectional chargers. Charging
methods can be classified as conductive charging, battery
swapping, wireless charging or inductive charging as shown
in Fig. 3. The majority of commercial EVs use a conductive
charging technique where the battery is connected to the
power grid via a cable. Conductive chargers can be
categorized into three charging levels as Level 1-3 according
to SAE J1772 and four modes as Mode 1- 4 according to the
IEC 61851-1 standards [45], [46]. Time-varying magnetic
fields are used in wireless charging methods to transmit power
from the grid to EV battery. Wireless charging can be divided
into three types such as capacitive, inductive and resonant
inductive [47]. Three types of charging levels, four charging
modes and different connectors and ports will be described in
the following subsections.
1) CHARGING LEVELS
Conductive charging involved an electric connection
between the charging inlet and the vehicle which follows three
charging levels such as Level 1, Level 2, and Level 3
depending on the power level as shown in Table 2. Level 1
and Level 2 charging are used in onboard chargers with AC
power and follow the same set of standards. The Level 1
charger uses a 120 V single-phase AC power supply and has
the slowest charging speed which is generally used in
domestic with low power levels (up to 1.92 kW) without any
additional infrastructure [48], [49]. Therefore, Level 1
charging is appropriate for long-time or overnight charging.
Level 1 chargers generally required about 11-36 hours for 1.9
kW charging power for a 16-50 kWh EV battery [50]. The
primary charging method for private and public facilities is
Level 2 charger, as they have comparatively fast charging
abilities. The charging time of Level 2 is 3 to 5 times faster
TABLE 1. Specifications of commercial electric vehicles [38],
[39], [40], [41], [42].
Vehicle Model
Type
Battery
Capacity
(kWh)
Driving
Range
(km)
Connector
Type
Chevrolet Volt
PHEV
18.4
85-Battery
Type 1 J1772
Mitsubishi
Outlander
PHEV
20
84-Battery
CCS, Type 2
Volvo XC40
PHEV
10.7
43-Battery
CCS, Type 2
Toyota Prius
Prime
PHEV
8.8
40-Battery
SAE J1772
Nissan Leaf Plus
BEV
64
480
CHAdeMO,
Type 2
Tesla Model S
BEV
100
620
Supercharger
Tesla Model X
BEV
100
500
Supercharger
Tesla Model 3
BEV
82
580
Supercharger
Kia Niro- SUV
BEV
64
460
CCS, Type 2
Lexus UX 300e
BEV
54.3
320
CHAdeMO,
Type 2
Ford Mustang
BEV
70
400
CCS, Type 2
Jaguar ev400
BEV
90
450
CCS, Type 2
Renault Zoe
BEV
52
390
CCS, Type 2
BMW i3
BEV
37.9
310
CCS, Type 2
Chevrolet Bolt
BEV
65
402
CCS, Type 2
Honda e
BEV
28.5
220
CCS, Type 2
Porsche Taycan
BEV
93
410
CCS, Type 2
Volkswagen e-
Golf
BEV
35.8
230
CCS, Type 2
Mercedes-EQA
BEV
66.5
420
CCS, Type 2
Audi e-tron
BEV
95
400
CCS, Type 2
BMW iX3
BEV
80
460
CCS, Type 2
Toyota Mirai
FCEV
1.6
647
-
Hyundai Nexo
FCEV
40
570
-
Honda Clarity
FCEV
25.5
550
-
BYD Atto 3
E-REV
60.4
420-Battery
CCS, Type 2
Hyundai Kona
E-REV
64
577-Battery
CCS, Type 2
FIGURE 3. Electric vehicle charging methods.
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
6
than Level 1 chargers due to high power usage [51]. Level 2
charging can provide power up to 19.2 kW for both single-
phase and split-phase with 208 Vac or 240 Vac voltage.
Dedicated components and installations are required in Level
2 chargers for high power transfer through the onboard
charger. The charging time range is 2 - 3 hours for 19.2 kW
with an EV battery capacity of 30 -50 kWh [3]. Level 1 and 2
charging connectors follow the IEC62196-2 standard in
Europe, SAEJ1772 and Tesla superchargers in the USA
[52],[53].
The DC fast charging or Level 3 charging uses AC and DC
power to deliver high voltage DC power to the EV battery. The
Level 2 chargers can handle a high-power range between 20
kW to 350 kW to supply DC voltage of around 300 Vdc to 800
Vdc in offboard chargers. DC fast chargers are directly
connected to the vehicle via off-board chargers to the three-
phase power grid. Charging time of 90 kW or larger Level 3
charger is range 0.2 - 0.5 hours which is faster than Level 1
and 2 [50]. CHAdeMO, Tesla superchargers and CCS combo
1, 3 connectors are considered for level 3 fast charging.
However, low-power chargers including Level 1 and Level 2
have the lowest negative impact on the power network during
peak time. The local distribution grid may become overloaded
by the level 3 chargers due to high power usage during peak
times [54].
Extrema fast charging (XFC) systems can deliver a
refueling experience like ICE vehicles. The XFC systems can
manage more than 350 kW power with 800 Vdc internal DC
bus voltage and battery recharging time is approximately 5
min. The XFC stations are designed with power electronic
components focusing on solid-state transformers (SST),
isolated DC-DC converters, and front-end AC-DC converter
stages and controllers. The installation cost of the XFC is very
high and required dedicated EVSE to deliver high power. The
XFC station can be designed by combining several XFC
systems to provide a chance to lower operational and capital
investment to make it economically feasible. Additionally,
SST provides advantages over conventional line-frequency
transformers for converting medium voltage levels into low
voltage levels and providing galvanic isolation in XFC
stations [55].
2) CHARGING MODES
The International Electrotechnical Commission (IEC)
defines 4 charging modes (IEC-62196 and 61851) for AC and
DC charging systems and provides the general attributes of the
safe charging process and energy supply requirements [56]. A
comparison of charging modes is presented in Table 3 with
specifications and charging configurations. The slow charging
applications follow mode 1 which comprises with earthing
system and circuit breaker for protection against leakage and
overloading conditions. The current limit of mode 1 varies
from 8 A to 16 A depending on the country. The EV is directly
connected to the AC grid either 480 V in three-phase or 240 V
in single-phase via a regular socket in mode 1. The charging
cable is integrated with a specific EV protection device (In-
cable control and protection device (IC-CPD) in mode 2 to
enable control and protection. Mode 2 charger offers a
moderate safety level and utilizes minimum standards. This
mode delivers slow charging from a regular power socket
which is ideally suited for home installation [57]. Single-phase
or three-phase AC power can be used in this mode with a
maximum power of 15.3 kW and 32 A current flow [5]. The
mode 2 cable provides over-current, overheat protection, and
protective earth detection. Therefore, mode 2 charging cables
are more expensive than mode 1 due to high current flow and
provide moderate safety for modern EVs [58].
TABLE 2. Comparison of different electric vehicle charging levels [48], [50].
Specification
Level 1
Level 2
Level 3
Extreme Fast Charging
(XFC)
Charging Power
1.44 kW - 1.9 kW
3.1 kW – 19.2 kW
20 kW – 350 kW
>350 kW
Charger Type
Onboard - Slow charging
Onboard - Semi-fast charging
Offboard - Fast charging
Offboard – Ultra-fast
charging
Charge Location
Residential
Private and commercial
Commercial
Commercial
Charging time
200 km: +/- 20 hours
200 km: +/- 5 hours
80% of 200 km: +/- 30 min
Approximately 5 min with
high energy density
Power Supply
120/230 Vac, 12 A – 16 A,
Single phase
208/240 Vac, 12A - 80A,
Single phase/Split phase
208/240 Vac & 300-800Vdc,
250-500A
Three phase
1000Vdc and above, 400A
and higher Polyphase
Supply Interface
and Protection
Type
Convenience outlet (Breaker
in cable)
Dedicated EV supply
equipment (Breaker in the
cable and pilot function)
Dedicated EV supply
equipment (communication
& event monitoring between
EV and charging station)
Dedicated EV supply
equipment (communication &
event monitoring between EV
and charging station)
Standards
SAE J1772, IEC 62196-2, IEC 61851-22/23,
GB/T 20234-2
IEC 61851-23/24
IEC 62196-3
IEC 62196
SAE J2836/2 & J2847/2
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
7
Mode 3 is used for slow or semi-fast charging via a specific
outlet with the controller. The dedicated circuit is permanently
installed (on the wall) for protection, communication, and
control in this mode. Public charging stations are commonly
built with mode 2 and are able to facilitate integration with
smart grids. Mode 3 allows a higher power level with a
maximum current of 250 A which is used by fixed EVSE for
single-phase or three-phase grid integration. The connection
cable includes an earth and control pilot to enable proper
communication between the EV and the utility grid. Fast
charging station uses mode 4 via fixed EVSE to deliver DC to
the vehicle which is utilized in public charging stations. The
installation includes control, communication and protection
features [59]. Mode 4 chargers are more expensive than mode
3 and the connection includes earth and a control pilot to
control a maximum of 400 A current. Off-board chargers
follow mode 4 specifications with a wide range of charging
capabilities over 150 kW power [5].
D.
ELECTRIC VEHICLE CHARGING CONNECTORS
EV charger components (including power outlets, connectors,
cords, and attached plugs) are the main components of EVSE
which provide reliable charging, discharging and protection
for the charging system. The configuration of the peripheral
devices, power ratings, and standards of EV chargers are
various in different jurisdictions. However, governing bodies
and manufacturers are attempting to ensure compatibility by
developing international standards, protocols, and couplers for
slow and fast charging systems to avoid conflicts and
difficulties [61]. Commercially available different AC and DC
connectors are shown in Tables 4 and 5 respectively by
following their specifications and standards. AC chargers are
slow chargers which take 6 - 8 hours to fully charge EV. DC
chargers use for fast charging with a higher power range of up
to 400 kW. The various connectors can be categorized into
three groups according to the IEC 62196 - 2 standards.
Type 1 connectors are widely used in Japan and USA for
AC single-phase charging and follow SAE J1772 standards.
They have low power charging capability (maximum capacity
of 19.2 kW) with a voltage of 120 V or 240 V with a maximum
current of 80 A [62]. The charging cable of Type 1 connector
is permanently installed to the station. Type 2 connectors are
considered as standard type in all countries which support
single-phase and three-phase charging by following IEC
61851-1 standards [63]. Type 2 - Mennekes connectors are
utilized in Europe and Type 2 - GB/T are used in China. This
connector supports mode 2 and 3 charging with high power
(22 kW) than Type 1. The detachable charging cable of the
Type 2 station allows to charger of Type 1 vehicles with the
correct cable [64],[65]. Type 3 connectors are used in France
and Italy that includes Type 3A and 3C depending on the
physical formats. Type 3 connectors or SCAME plugs allow
both single-phase and three-phase charging with shutters to
prevent and follow IEC 62196-2 standards.
The DC chargers or superchargers deliver the fastest
charging rate which follows the combined current system
(CCS) and IEC 62196 standards. The IEC 62196-3 standard
specifies four types of coupler configurations for DC fast
chargers. They are configuration AA (CHAdeMO),
configuration BB (GB/T), configuration EE (CCS-Combo 1),
and configuration FF (CCS-Combo 2) [66]. The Combo 1 and
Combo 2 connectors are extended versions of Type 1 and 2
connectors with two added DC contacts to allow high-power
charging. The CCS - Combo 1 connector is based on Type 1
chargers and is used in the USA. Europe preferred CCS -
Combo 2 connectors which have a Type 1 coupler
configuration. CCS connectors can withstand a high-power
range of up to 350 kW. The GB/T fast charging DC connectors
used in China follow GB/T 20234-3 standards. It is capable to
operate higher power ratings up to 237 kW with a maximum
voltage of 1000 V and 400 A current. CHAdeMO fast
charging systems developed in Japan, and it competes with the
TABLE 3. Comparison of different charging modes [5], [60].
Charge Mode
Phase
Current
Voltage
Power
(Max)
Specific
Connector
Charging Configuration
Mode 1
AC - 1
AC - 3
16A
230-250V
480V
3.8 kW
7.6 kW
No
Mode 2
AC - 1
AC -3
32A
230-250V
480V
7.6 kW
15.3 kW
No
Mode 3
AC - 1
AC - 3
32-250A
230-250V
480V
60 kW
120 kW
Yes
Mode 4
DC
250-400A
600-1000V
>150kW
Yes
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
8
supercharger network, CCS and GB/T standards. CHAdeMO
connectors have ultra-fast charging and V2G integration
ability for 400 kW with 1000 V maximum voltage and 400 A
current. [70]. Tesla offers a connector for both AC and DC
charging for all the charging levels. Tesla superchargers offer
excellent fast charging speeds via their own designed charging
stations and connectors can supply 72 kW, 150 kW, or 250
kW electric power [71]. Type 2 connector required for AC
charging with Tesla station which allowed power up to 11.5
kW and an AC voltage of 250 V single phase. Tesla
superchargers are built for Tesla cars and version 3 models
have a maximin power of 250 kW. The Australian standard
TABLE 4. Specifications of different AC charging connectors [13],[67],[68],[63].
Specifications
Japan
USA
Europe
China
ALL Markets
Charger type
Type 1 (SAE J1772)
Type 2 (Mennekes)
Type 2 (GB/T)
Tesla
Level 1
Level 2
Mode 1
Mode 2-3
Mode 2
Mode 3
Mobile
connection
Wall
connection
Maximum
Capacity
1.9 kW
19.2 kW
4 kW
22 kW
7 kW
27.7 kW
7.7 kW
11.5 kW
Input voltage
120 V
Single phase
240 V
Split phase
250 V
Single
phase
480 V
Three
phase
250 V
Single
phase
400 V
Three
phase
120/240 V
Single
phase
208/250V
single
phase
Current rating
16 A
80 A
16 A
32 A
16 A
32 A
16/32 A
48 A
Standards
SAE J1772-2017
IEC 62196-2, IEC 61851-22/23
IEC 62196-2
IEC 61851-22/23
GB/T 20234-2
IEC 62196-2
IEC 62196-2
TABLE 5. Specifications of different DC charging connectors [13],[67],[69].
Specifications
Japan
USA
Europe
China
ALL Markets
Charger type
CHAdeMO
CCS - Combo 1
CCS - Combo 2
GB/T
Tesla
Supercharger
CHAdeMO
Capacity
50 - 400 kW
150 - 350 kW
350 kW
60 - 237 kW
250 - 350 kW
50 - 400 kW
Input voltage
50 - 1000 V
200 - 1000 V
200 - 1000 V
250 – 950 V
300 - 480 V
50 - 1000 V
Maximum
Current
400 A
500 A
500 A
250 – 400 A
800 A
400 A
Standards
IEC 61851-23/4
IEC 62196-3
JEVS G105
SAE J1772
IEC 61851-23/24
IEC 62196-3
IEC 61851-23/24
IEC 62196-3
DIN EN 62196-3
GB/T 20234-3
IEC 62196-3
IEC 62196-3
IEC 61851-23/4
IEC 62196-3
JEVS G105
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
9
for EV charging plugs and connectors (IEC 62196)
encourages the adoption of both US and EU connector
standards rather than imposing a single standard [72].
E.
ELECTRIC VEHICLE BATTERY TECHNOLOGY
The EVs represent the largest share of the global battery
market which is expected to the continuous growth of energy
density, fast charging capabilities with long cycle life, and
compliance with safety and environmental standards [73],
[74]. The battery is a key component of an EV that is capable
to handle high energy capacity (kWh), and high power (kW)
within limited weight, and space at an affordable price [75].
EV battery is connected to the DC-link via a DC-DC converter
and the state of charge (SoC) demonstrates the control
mechanisms of the battery. EV battery is capable to store
electrical energy in the form of chemical energy when
charging (G2V) and regenerative braking and feeding back to
the power grid when discharging (V2G). Moreover, EV
batteries can deliver power for long and sustainable periods of
10-15 years. The cost and driving range of the vehicle is
determined by the energy density of the EV battery pack.
Significant research studies and funding have been dedicated
to developing advanced battery technologies that are
appropriate for EVs. Various types of EV batteries are
available in the market and the main types are lead acid,
nickel-based, and lithium-ion batteries as shown in Fig. 4 [76].
Characteristics and specifications of commonly used EV
battery types are presented in Table 6.
Lead-acid batteries are inexpensive (cell cost is 50-600
$/kWh), reliable, efficient, safe, and employed for high-power
applications [80], However, they have low specific energy
density (30 - 40 Wh/kg), a short lifetime (< 1000 cycles), and
weak performance in cold temperatures [81]. Nickel-based
batteries have been widely used in EV batteries such as nickel
metal hydride (NiMH), nickel-cadmium (NiCd) and nickel
Zinc (NiZn), nickel ion (NiFe). NiMH battery is commonly
employed in HEV and EV due to their longer life cycle ( 2000
cycles) than lead acid batteries, abuse tolerant and safe [82].
The maximum energy density of the NiMH battery is 120
Wh/kg, the power density (1000 W/kg) and highest
charge/discharge efficiency is 92% [83]. The main challenges
in Ni-based batteries are high self-discharging, cost, heat
generation at high temperatures, and required additional
control systems to control losses.
Lithium-ion (Li-ion) batteries are the dominant power
storage in EVs due to their improved performances, high
energy efficiency, energy storage, low self-discharge rate, and
TABLE 6. Electric Vehicle Batteries with specifications [77], [78], [79].
Battery Type
Vehicle Model
Specific
energy
(Wh/kg)
Energy
density
(Wh/L)
Cycle life
Safety
Specifications
Lithium Nickel
Cobalt Aluminum
Oxide (NCA)
Tesla X, S, 3, Y
200-260
600
500
Good
• Provide good energy yield and is inexpensive
• Extensively used in both portable electronics
and EVs
Lithium Nickel
Manganese Cobalt
Oxide (NMC)
Nissan Leaf, Kia e-
Soul, Volkswagen
e-Golf, BMW i3,
I3s Peugeot e-208
150-220
580
1000-2000
Good
• Stable chemistry, and low-cost materials
• Provide a high energy density and is able to
charge rapidly compared to other batteries
Lithium Manganese
Oxide (LMO)
Chevy-Volt,
Escape PHEV
100-150
420
300-700
Good
• Good energy performance and low cost of
materials
• Short life cycle
Lithium Iron
Phosphate (LFP)
EVs, especially in
e-bikes, e-rikshaw,
90-120
330
1000-2000
Excellent
• Stable, long lifecycle, and significant safety
• High energy density and low rate of self-
discharge make it ideal for larger EVs such as
vans, buses, or trucks
Lithium Titanate
(LTO)
Mitsubishi, Honda
50-80
130
3000-7000
Excellent
• Long life, fast charge using advanced
Nanotechnology
• very high rate of charging and discharging
possible without compromising on safety
FIGURE 4. Types of electric vehicle batteries.
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
10
great performance in high temperatures. Commonly used Li-
ion batteries are Lithium Nickel Manganese Cobalt Oxide
(NMC), Lithium Nickel Cobalt Aluminum Oxide (NCA),
Lithium Iron Phosphate (LFP), Lithium Manganese Oxide
(LMO) and Lithium Titanate (LTO). The Li-ion battery is very
efficient (90%) and can charge regularly at any SoC. The rapid
charging capability, high specific energy (180 Wh/kg), power
density (5000 W/kg), longer lifespans are recent achievements
of Li-ion batteries. Most of EV manufacturers use LMO
batteries due to their high specific power and energy. Tesla
cars have high power density NCA battery capacity (Tesla
Model 3 has 80.5 kWh). A total capacity of 62 kWh NCM is
used in Nissan Leaf and the new generation Chevrolet Bolt EV
(2020) consists of a 68 kWh total battery capacity [84]. In [85],
an extensive study of various control schemes for battery
performance is evaluated under different conditions including
stability, multi-power resources, distributed network, and the
different size of ESS in EVs.
The battery management system (BMS) is responsible for
the energy management of the battery to ensure reliable,
efficient and safety performance of the vehicle. The BMS
includes sensors, a power delivery unit, and communication
protocols to reduce the stress of the battery charging and
discharging and prevent sudden abruption current to avoid
high discharging rates. Moreover, cell balancing, calculating
the state of charge (SoC), computing the driving range, and
other auxiliary are powered via the BMS. The energy
management system (EMS) is critical to address the driving
range, battery life, efficiency, and reliable operation the EVs
[86]. The SoC and state of health (SoH) reflect battery
performance and deliver essential data for energy
management and optimal control design for the vehicle
[87],[88]. The accurate estimation of battery states is complex
due to its non-linear and high time-varying behaviors. SoC
estimation is a key method used to maintain battery status,
which displays the remaining capacity of the battery via
advanced algorithms with measurements [89]. The SoC is the
proportion of the remaining capacity of the battery to its rated
capacity under a specific discharge rate.
The primary function of the SoC is to communicate
between the vehicle and the instinctive battery state to avoid
overcharging and discharging the battery [90] [91].
Furthermore, it provides critical information on available
power, and battery usage until the next recharge, and executes
a control system to improve the performance and life of the
battery [92]. Numerous techniques have been proposed for
real-time SoC estimation which can be categorized into five
groups model-based estimation, lookup table-based, coulomb
counting, data-driven estimation method, and hybrid method
[91]. Model-based SoC estimate techniques such as equivalent
circuit models, electrochemical models, and electrochemical
impedance models are frequently used in EV charging [93].
The model based SoC estimation techniques is accurate and
powerful due to the reliance on the deep analysis of electrical,
chemical, and combination of both characteristics. The
comprehensive review of SoC estimation methods is
presented in [94] by highlighting algorithm/control design,
advantages, disadvantages, and challenges to selecting
appropriate SoC methods for EVs. The comparison of existing
SoC estimation methods and robust SoC estimation
techniques are proposed in [95] based on the non-linear model
and experimentally. In [96], a novel adaptive Kalman filter
algorithm is designed for the SoC estimation of Li-ion
batteries used in EVs. The improved deep neural network
approach has been used in [97] to implement a new SoC
estimation method for Li-ion batteries in EV applications.
III. STANDARDS OF ELECTRIC VEHICLE CHARGING
AND GRID INTEGRATION
Standards play a key role in the deployment and development
of EV technology in society which serve as a crucial
foundation for broad market penetration and customer
satisfaction. The high level of EV charging integration has
created new challenges and requirements in the automotive
industry and electric networks. Standards and grid codes are
designed to ensure reliable and safe EV integration with the
power grid and other energy resources. Charging standards are
applied to EVs to provide accurate functionality, protection,
interoperability, and integration with various parameters and
conditions [98],[99]. Many EV charging standards are
employed around the world to interact with charging
infrastructure. The Society of Automotive Engineers (SAE)
and the Institute of Electrical and Electronics Engineers
(IEEE) are two main contributors to charging and grid
integration standardizations. The SAE and International
Electrotechnical Commission (IEC) standards are widely used
for EV conductive charging systems. Table 7 lists the
TABLE 7. Major standards of EV charging systems.
Standard
Description
SAE J1772
Conductive charger coupling of AEVs and HEV
SAE J2344
Guidelines for EV safety
SAE J2894/2
Power quality requirements
SAE J2953
Standards for interoperability of EV and charger
SAE J2847/1
Communication between EV and the grid
SAE J3068
EV power transfer system using a three-phase AC
capable coupling
SAE J2931/7
Security for PEV communication
IEC 60038
Standards for the voltage for charging applications
IEC 62196
Standards for EV conductive charging components
(outlets, plugs, connectors, and inlets)
IEC 60664-1
Installation coordination for charging equipment in
low-voltage supply
IEC 62752
Standards for cable control and protection devices
IEC 61851
Covering safety-related specifications on the
charging station
ISO 15118
Standards for V2G communication protocols and
interfaces
ISO 17409
Specifications for the connection of EV with an
external energy source
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
11
preferred international standards for EV charging systems
including conductive charging, safety, and grid integration
regulations.
Charging standards and regulations can be categorized as
charging components, grid integration, and safety [100]. The
specifications of EV conductive charging components
including connectors, plugs, outlet-socket, and inlets are
provided by SAE J1772 and IEC 62196 standards. series of
standards in IEC 62196 and IEC 61851 provided the
specification for EV connectors in AC and DC charging
systems. Inductive charging standards are SAE J1772, and
IEC 61980, and battery swapping charging systems used IEC
62840 standards [101]. AC charging systems comprises SAE
J1772 standards with 100V domestic power in US and Japan
and 220V power in Europe. GB/T 20234 standards are
employed in AC charging systems in China. Connectors and
ports in DC charging systems are designed by using a set of
IEC 61851 standards, CHAdeMO which is described in GB/T
20234, and CCS Combo standards [102],[103].
Internationally established standards, which supervise
different characteristics of EVs are presented in Table 8.
Charging and discharging of EVs through the grid is
controlled by grid integration standards and codes. The EV is
considered a distributed energy resource in V2G operation
mode which is applied power grid integration EV standards.
Grid integration standards include power regulations, safety,
and power quality requirements, and important grid codes to
ensure reliable integration of EVs. Grid interconnection
standards and regulations are established by the Institute of
Electrical and Electronics Engineers (IEEE), and
Underwriters’ Laboratories (UL) organizations. Standards for
the interconnection of distributed resource in the power grid is
included in IEEE 1547 which explains the performance,
maintenance, testing, and safety requirements of all DER on
TABLE 8. International EV charging standards and grid codes.
Organization
Standards
Description
The Institute of Electrical
and Electronics Engineers
(IEEE) [17]
IEEE 519-1992
Harmonic control in electrical power system
IEEE 1159-1995
Monitoring electric power quality
IEEE 1100-1999
Powering and grounding sensitive electronic equipment
IEEE 1366-2012
Electric power distribution reliability indices
IEEE1547
Standards for interconnecting distributed resources with electric power systems (10MVA or
less PCC)
P1547, P2100.1
Standards of different aspects of grid connection of DERs, charging system standardization
Society of Automotive
Engineers (SAE, United
States)
SAEJ2293
- Standards for on-board and off-board charging equipment (Conductive AC and DC,
inductive charging)
- Power requirement, system architecture for conductive AC, DC, and inductive charging
- Communication and network requirements of EV charging [67]
SAEJ1772
Ratings for all the equipment for EV charging- (voltage and current ratings of circuit breakers
and AC and DC charging levels 1 & 2)
SAEJ1773
Standards for inductively coupled charging systems
SAEJ2847
Communication requirements between EV charging system interfaces
International Electro-
technical Commission
(IEC, Britain) [21]
IEC61851
- Standards for EV conductive charging system operation-Cable, plug setups
- Onboard and offboard EMC requirements for conductive charging.
- Onboard and offboard charging equipment for EVs /PHEVs with 1000V AC and 1500V DC
supply voltage [104]
- Digital communication of DC charging control between EV charging controller and supply
equipment
- DC fast charging requirements
IEC61980
Standards for wireless power transfer for 1000V AC and 1500V DC supply voltage
IEC62196
Standards for connectors, plugs, and socket outlets used for conductive charging
IEC61000-2, 3, 4
Compatibility levels of low-frequency conductance, harmonic emission, EMC, flicker limits of
voltage
National Electric Code
(NEC) [19]
NEC625, NEC 626
Safety measures in the off-board EV charging system (conductors, connecting plugs, inductive
charging devices)
Underwriters’ Laboratories
(UL) [24]
UL2231, UL2251,
UL2202
Requirements for protection devices for EV charging circuits and charging system equipment
UL2594, UL1741
Requirements for EV supply equipment (inverter, converter, charge controller, and output
controllers used in power system)
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
12
distribution systems [105]. Power converters, controllers, and
safety specifications of DERs are presented in UL 1741
standards [106]. Communication standards in IEEE 2030.5
and ISO 15118 provide interoperable control for EVs via
information exchange, test procedures, response specification,
and security requirements [107].
The EVSEs are used to communicate with the EV to ensure
a safe and appropriate power supply other than delivering
energy between the EV battery and energy source. Therefore,
some standards are developed for signaling and
communication with multiple devices. The primary objective
of communication standards is to regulate the amount of
current provided and manage the current flow of different
devices. Moreover, the SoC of the battery also monitors and
allows to use of EVSEs. Communication specifications of the
DC off-board fast charger are designed with SAE J2847/2
standards [101] and PLC communication requirements can be
observed in SAE J2931/4. International Organization for
Standardization (ISO) is also developed many safety-related
standards and technical regulations for lithium-ion battery
packs (ISO 64691-3) and EVs in high voltage systems
(ISO/DIS 21498) [108].
IV. ARCHITECTURES OF ELECTRIC VEHICLE
CHARGING STATION
The primary purpose of the EV charging infrastructure is to
offer convenient, efficient, and reliable charging and
discharging of the EV battery. Charging station architecture
relies on the power source such as grid, RES or ESS, and AC
and DC bus configurations. The fast-charging stations are
connected to the medium voltage network to supply high
power from the grid. Therefore, they required high capital
investments to design additional control techniques to
maintain power requirements and standards on both sides of
the fast-charging station. RES and ESS are widely preferred in
the present EV charging station architecture to minimize
impacts on the grid while providing additional network
services. Moreover, charging stations with V2G capabilities
are currently being extensively researched to enhance grid
support. The architecture of EV charging stations can be
classified as AC bus, DC bus, and a combination of AC and
DC bus structures.
A.
CONVENTIONAL CHARGING STATIONS
The three-phase AC bus operated between the 250V- 480V
line-to-line voltage in the common AC bus-connected
charging stations [48]. The EV side of this architecture
consists of a DC-DC converter and AC-DC rectifier in each
EV charging point as shown in Fig. 5(a). Therefore, the AC
bus system causes an increase in cost, complexity, power
conversion stages, and reduced efficiency of the charging
system. The grid side comprises with a step-down transformer
that serves to supply appropriate voltage to the common AC
bus. In contrast, the grid side of the common DC bus
connected system has a single AC-DC converter to provide
DC power to the common bus as shown in Fig. 5(b). Each EV
load is employed with an independent DC-DC converter.
Hence, common DC bus architectures are more efficient, cost-
effective, small, and more flexible structures with greater
dynamic performance when compared to the AC bus-based
architecture. The DC bus system also offers a more adaptable
structure with the possibility to connect ESS and RES.
However, low operating PF of common DC bus charging
stations can generate undesirable harmonic impacts on the
utility grid.
AC charging stations are preferred as public charging
stations due to their low manufacturing cost and they consist
of matured AC technology and standard charging components
in the market. The slow charging application in AC bus-
connected systems has a maximum of 19.2 kW power [109].
The AC bus connected to fast, and ultra-fast charging stations
necessary to be equipped with advanced components and
controllers to maintain grid codes and EV charging standers.
Therefore, common DC bus architecture is commonly
preferred for fast and ultra-fast EV charging stations as they
have a low impact on the utility grid, a simple control strategy,
and high efficiency. The DC and fast charging (22 kW - 200
kW) and ultra-fast EV charging ( > 300 kW) capabilities are
commonly designed in off-board chargers with high power
flow and galvanic isolation is mandated between the EV
battery and the grid according to the IEC standards [110]. The
advantages and disadvantages of AC and DC bus-based
charging systems are summarized in Table 9. The comparative
analysis of AC and DC bus architectures is presented in [111]
(a)
(b)
FIGURE 5. Architecture of conventional EV charging station:
(a) Common AC bus-based system, and (b) Common DC bus-
based system.
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
13
for grid-connected fact EV charging systems. The power
quality of both AC and DC charging systems is evaluated
under dynamic and steady-state conditions and different
transformer configurations and concluded that common DC
bus architecture has better performance than common AC bus
architecture.
B.
AC AND DC BUS-BASED CHARGING STATIONS
The AC and DC bus-based architectures are considered as
a DC grid and AC microgrid which are particularly employed
with DC power sources. This hybrid architecture of EV
charging stations includes a power grid and different energy
sources which are connected to the AC and DC busses via
separate converters as shown in Fig. 6. This configuration
provides simultaneous operation of both AC and DC charging
by preventing additional power conversion states [112]. A
single bidirectional converter is employed to connect AC and
DC buses in the system which is called an interlinked power
converter and the corresponding buses can be used to connect
AC and DC loads. The interlink converter can maintain an
energy balance between both sides and operate according to
the load requirements. This architecture is very reliable,
flexible, and more efficient than AC and DC bus
configurations. The bidirectional DC-DC converter is
connected between the EV and the DC bus to achieve fast DC
charging and discharging via V2G operation. The AC and DC
bus-based structure is used to investigate microgrids and ESS
[113]. The stand-alone V2G control technique is proposed in
[114] to examine charging and discharging performance and
RES power characteristics in hybrid AC-DC charging
architecture.
C. RENEWABLE ENERGY INTEGRATED CHARGING
STATION
The RES-integrated EV charging systems have gained
interest in the industry as a cost-effective, clean, and
sustainable technique to charge EV batteries. RESs are
capable to provide services to the power grid by reducing peak
demand, energy efficiency, and reliability. EV charging
systems have been introduced with solar PV, wind power,
energy storage systems (ESSs), supercapacitors, and fuel cell
in recent days. RES integrated architectures enable low
emission, highly flexible, and economic EV charging as well
as provide ancillary grid services [115],[116],[117]. Among
different RESs, solar PV-powered EV charging stations are
widely established due to their technological advancement.
The ESSs are becoming an integral part of EV charging
systems along with the RESs in microgrid and smart grid
frameworks. The authors in [116] proposed a hybrid
optimization algorithm for ESS and solar PV integrated EV
charging stations to reduce the EV charging cost. In [118], a
grid-based EV charging system is designed with multiple
sources including solar PV, ESS, and diesel generators to
provide constant charging in grid-connected and islanded
modes. The decentralized EV charging optimization technique
FIGURE 6. Architecture of AC and DC bus-based EV charging
stations.
TABLE 9. Comparison of AC and DC bus-based charging stations architectures.
Architecture
Advantages
Disadvantages
AC bus-based EV charging
systems
• Highly available and mature technology with
standards.
• The complexity of the protection devices is low.
• Able to direct usage for local loads
• Stability and scalability are high
• Reliable switching and control techniques
• Ability to control active and reactive power
• A large number of converters reduce rated power and
efficiency.
• High cost due to multiple converters.
• Additional conversion stages are required for fast
chargers to avoid harmonics.
• Difficult to achieve high power quality and stability
• Complex to integrate RESs and required additional
DC/DC stage.
DC bus-based EV charging
systems
• Provide high efficiency and power density due to
low components.
• The control strategy is simple
• Low cost and flexible configuration which can
integrate ESS and RES easily.
• Helps to reduce the impacts of high penetration of
EV loads on the power grid
• Reduction in frequency fluctuation
• Complexity may increase with the additional energy
sources.
• Required protection devices to withstand sudden
changes
• The central converter needs server conditions due to
an increase in nominal power.
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
14
for building integrated wind energy is presented in [119] with
real-time coordination. Smart coordination with maximum
RES of charging systems can reduce the power load on the
grid and ensure cleaner energy [120].
The EV charging station may be supported by the power
grid, standalone RESs, or combined grid-connected RESs
depending on the power grid’s availability to prevent local
power network overload and ensure a higher proportion of
clean energy usage in RES-integrated architectures. Most
researchers attempt to enable high renewable energy-based
power generation on EV charging stations to decrease the
power demand during the charging period by managing their
charging patterns. The architecture of RES-connected
common AC bus-connected EV charging station is shown in
Fig. 7 (a) and DC bus-based architecture is shown in Fig 7(b)
respectively. RES integrated architectures include a power
grid, solar PV, wind power, ESS and bidirectional EV loads
with relevant converters and control units. The AC bus
architecture can be changed by using a common DC bus with
reduced converter stages.
RES-based charging systems is increasingly developed due
to various factors. The implementation of RESs and EVs
deliver an exceptional opportunity for sustainable charging of
EVs which can be directly utilized to charge EVs during peak
time [121]. Solar PV-integrated EV charging systems can be
employed to reduce peak demand by decreasing EV reliance
on grid power. Solar PV panels have been installed rapidly,
are more affordable at low cost, and EV batteries can be used
to store energy for solar PV as they can consume a large
amount of Solar PV energy [122], [123]. Many researchers
have discovered that coordinate operation of PVs and EVs can
decrease impacts encountered by individual PV and EV
integration on the power grid [124]. However, the integration
of EVs and RESs into the grid is a challenge due to the
additional planning stages, converters, and control strategies
needed to be considered in this type of charging station. The
uncontrolled or uncoordinated effect on system consistency
can be compromised and introduced many negative impacts
on the distribution grid [125],[126]. The RESs connected to
common DC bus-based EV charging architecture are
extensively researched over other structures due to efficiency
and flexibility to integrate different energy resources, and
smart control capabilities [112].
V. ELECTRIC VEHICLE CHARGING TOPOLOGIES
The expanding popularity of EVs results in various types of
charging topologies, control strategies, converters, power
requirements, and charging stations to maximize energy
efficiency while satisfying the constraint of both EVs and the
utility grid. Several articles have summarized EV structure and
charging configuration [105],[127],[128]. Modern PEVs share
a similar powertrain, which is comprised of a high-voltage
battery pack to sustain moderate currents, an onboard charger,
battery management system, drive inverters, DC-DC
converters, and high voltage loads such as cooling system, and
heaters [13]. EVs are highly dependent on the energy storage
technique including high-voltage battery packs,
supercapacitors, and fuel cells. Therefore, charging
technology provides an essential link between the EV and
energy supply resources. BEVs can be charged from AC and
DC power via EVSE by communicating with the EV and the
charger to ensure an efficient and safe energy supply [101].
For EV charging systems, three charging methods are
employed including conductive, inductive charging, and
battery swapping as shown in Fig. 8 [129]. Both conductive
and inductive or wireless charging have advantages over each
other in terms of convenience, reliability, and efficiency, thus
it is anticipated that both types of chargers will exist at the
same time in the future EV market [130], [131].
A comprehensive review of conductive charging
technology is presented in this paper. Many automakers equip
their vehicles with both AC and DC chargers, giving
customers great flexibility in charging their vehicles at home
or in public charging stations [132]. Level 1 or level 2 chargers
are designed used for charging EVs at home, whereas level 2
(a)
(b)
FIGURE 7. Architecture of renewable energy sources and
energy storage systems connected (a) Common AC bus based,
and (b) Common DC bus-based EV charging stations.
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
15
and level 3 or DC fast chargers are found at public charging
stations [133]. Most EV chargers are compatible with a wide
range of EV models [101]. EV manufacturers include both AC
and DC chargers in the same vehicle to enable either onboard
or offboard charging capabilities as shown in Fig. 9.
Furthermore, EV battery chargers have various AC and DC
power converters to provide high efficiency, reliability, and
power density and either through coordinated or
uncoordinated control [134]. EV chargers use either AC or DC
power supplies to recharge the battery pack with specific
power ratings, standards, and components. AC charging is the
common method used in EVs which is converted AC-DC
inside the EV in the onboard charger and then charge the
battery [135]. The charging speeds depend on the converter
capability and output power level of the charging point.
Conventional AC chargers have limited power, less than
22kW, and required longer charging time. The DC charging
used in fast chargers uses an off-board circuit to generate a
high voltage (300 - 1000 V) [136].
The DC chargers convert power before entering the EV in
the dedicated offboard charger and then directly charge the
battery from DC power bypassing the in-built converter inside
the vehicle. DC charging requires high power (20 kW - 350
kW), specific components, safety protocols, and large power
control circuits to control high power levels. EV charging
control systems can be classified as uncoordinated and
coordinated or smart chargers. The battery starts to recharge
instantly when plugged in or after a user-fixed delay in
uncoordinated charging systems [137]. Therefore,
uncoordinated chargers can cause a significant impact on the
power grid when unpredictable EV charging loads arrive and
lead to high peak demand loading, and power quality impacts
[138]. Hence, well-synchronized charging coordination
between EVs and grid operators is essential to maximize the
load factor and minimize the power losses while enabling grid
support [139].
A.
GRID-TO-VEHICLE AND VEHICLE-TO-GRID MODE
The power flow direction of an EV can be either
unidirectional or bidirectional according to the charging
configuration built into the EV. The unidirectional charging
system uses an AC-DC rectifier on the grid side and a
unidirectional DC-DC converter in the onboard charger with a
less complex control system. In contrast, bidirectional EV
chargers can transfer power to the utility grid (discharging) as
well as EV battery (charging) through off-board chargers
using a bidirectional AC-DC converter and bidirectional DC-
DC converter [140]. Most of the charger fleet operates in G2V
mode which uses limited hardware and a simple control
system to charge the battery from grid-supplied or locally
generated electricity. A unidirectional charging system has
simple structure which simplifies interconnection problems
and tends to minimize battery degradation [141].
Unidirectional converters are executed in a single stage to
reduce weight, volume, cost, and losses [142]. Moreover,
active front-end unidirectional converters can offer reactive
power support by controlling the phase angle of the current
without discharging a battery. High penetration of
unidirectional chargers can achieve power grid requirements
while avoiding the cost, safety, and performance issues
associated with bidirectional chargers. The comparison of
unidirectional and bidirectional chargers of EV presents in
Table 10.
V2G mode has bidirectional energy transfer capability
between EV and the electrical grid through a communication
strategy in charging infrastructure [143]. The bidirectional
mode of EV acts as distributed generation, storage, and load
for the power grid. Many researchers have recently indicated
that the application of V2G in the ancillary market is more
essential to voltage controlling and spinning reserve other than
reducing peak load. The spinning reserve refers to the excess
generation that could provide immediate backup power to the
power grid. Many studies have explored EV deployment in
ancillary services providing many cost-effective services and
generating revenue for utilities via V2G operation. The main
duties of V2G include:
• Regulate battery charging operation to enhance battery
life and reduce overcharging circumstances,
• Track the SoC of the battery to ensure proper charging
and discharging operations and provide appropriate
values of SoC and depth of discharge (DOD) to the user
FIGURE 8. Classification of charging technologies used in
electric vehicles.
FIGURE 9. Onboard and offboard charging systems of electric
vehicle.
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
16
• Control the EV battery SoC
The V2G can provide ancillary services including voltage
and frequency regulations, improved system stability, load
following, peak load shaving, energy supply, reactive power
support, and RES integration. Technology improvements in
EVs have introduced new energy transmission modes,
vehicle-to-house/building (V2H, V2B), vehicle-to-load
(V2L), and vehicle-to-vehicle (V2V). therefore, bi-directional
energy transfer from EVs can be categorized as below [146].
• V2G – Power flows from EV to the distribution grid
• V2H/V2B – Power flows from an EV to a home or
building
• V2L - Power flows from an EV to load
• V2V– Power flows from one EV to another EV
The majority of current V2G analyses are focused on the
simpler "Smart charging" control systems that extend standard
demand response applications to PEVs [145]. The
recommended test programs for V2G operation cover three
broad areas of investigation: battery impact, network
operation, and system response. For V2G applications, BEVs
have a high battery capacity, which results in a longer range
and support for electric grid integration. For future V2G
scenarios, the major areas of attention in EV development are
the energy storage system, powertrain, and charging
infrastructure [147].
B.
ONBOARD CHARGERS
The onboard chargers have either unidirectional or
bidirectional power transfer capabilities which are compatible
with level 1 and 2 chargers due to limited size, weight, volume,
and power. Most of the onboard chargers use two-stage
converter topologies an AC-DC stage in the front end and a
DC-DC stage in the back end [148]. A grid-connected front-
end passive rectifier feeds a boost converter that operated as a
PFC in onboard chargers. Then supplies appropriate power to
the onboard DC-DC converter via a DC link to charge the
battery [149]. The front-end rectifier stage can be achieved by
a half-bridge, full-bridge, or multilevel converters. Onboard
charging offers lower power transfer and therefore required
more charging time compared to offboard chargers. The
configuration of the onboard charger is shown in Fig. 10.
Onboard charges can deliver 1.9 kW (level 1) and 19.2 kW
(level 2) AC power levels. AC power is directly fed to the AC-
DC rectifier in the onboard charger from the AC charging
station. Then DC-DC converter regulated appropriate power
levels and feeds power to the battery pack through a protection
circuit by communicating with BMS and the power control
unit [150].
Onboard chargers with advanced control techniques have
been proposed in many research studies to improve the
controllability, efficiency, and grid support of the charging. In
[151], a single-phase compact onboard charger with the
current ripple compensator technique is proposed. The
compensator consists of a zeta and boost converter which is
connected in series with the EV battery in a non-isolated
charging system without using bulky inductors or capacitors.
A comprehensive study of wide-bandgap devices is presented
in [152] for onboard chargers and demonstrated a possible
approach in the onboard application via 400V/80 A test bench
with Si MOSFET components. The multifunctional onboard
battery charger presented in [153] can operate as AC-DC
converting with PFC as well as V2G operation through
sharing inductors and switches in one system. A three-phase
onboard charger is integrated with the EV propulsion system
[154] by connecting the three-phase interface to the propulsion
system. The system is implemented with a 3.3 kW three-phase
integrated charger and unity power factor, 92.6% efficiency,
TABLE 10. Characteristics of unidirectional and
bidirectional power flow of electric vehicles.
Features
Unidirectional
Charging (G2V)
Bidirectional Charging
(both G2V and V2G)
Power flow
The charging rate of EV
control with a
unidirectional power
flow which is based on
energy scheduling of
G2V
G2V and V2G modes
enable bidirectional power
flow to achieve a range of
grid support and services
Type of
Switches
Unidirectional power
converters and diode
bridge
Low and medium-power
transistors and high-power
gate thyristors
Control
System
A simple and easy
control system, active
control of charging
current, and energy-
pricing techniques used
to manage basic control
Complex control system
with additional drive
circuit. Required extensive
measures and an accurate
communication system
Services
Ancillary services, load
leveling, load profile
management, and
frequency regulation
[144]
Voltage and frequency
regulation, backup power
support during peak time,
active and reactive power
support, PFC and helps to
integrate RESs to the gird
Safety
Isolated or non-isolated
Isolated or non-isolated,
include high safety
measures and anti-
islanding protection [145]
Advantages
- Simple power control
strategy
- Minimized operational
cost, power losses,
emission, overloading,
and interconnection
issues.
- Supply voltage and
frequency regulations
- Provide reactive power
support by controlling
the phase angle of the
current.
- Improve voltage profile,
power quality, active and
reactive power support,
load leveling,
- Volage and frequency
regulation and peak load
shaving.
- Grid power losses and
emission minimization
- Load factor improvement
and increased profit
- Enable RES integration
with grid
Limitations
- Limited services
required a power
connection.
- No extra degradation
in battery
- Required 2-way power
flow converters and
communication.
- High complexity, capital
cost, energy losses, and
stress on the devices.
- Need for smart sensors
and meters
- Fast battery degradation
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
17
and reduced harmonic restoration of 4.77%. Research in [155]
proposed an active power decoupling function for low-power
charging onboard in PEVs. The proposed onboard charger can
operate in G2V, and V2G, and the EV battery can be charged
from the high voltage ESS by sharing capacitors, switches, and
transformers in the same system.
Onboard EV charges are broadly categorized into
unidirectional or bidirectional and single-phase or three-phase
chargers. Various types of onboard chargers have been
introduced recently as an optimum solution to the high
penetration of EVs. The conventional method of EV battery
charging is achieved through a dedicated onboard charger.
Conventional or dedicated onboard chargers comprise two
converters used for battery charging and motor controlling as
shown in Fig. 11(a). Dedicated onboard chargers have limited
power transfer capabilities due to several constraints including
volume, cost, and weight of the vehicle [156]. Integrated
onboard chargers have been designed to overcome the above
limitations which are closely integrated with an electric motor
using a single AC-DC converter as shown in Fig. 11(b).
Integrated chargers can operate the existing propulsion system
for battery charging by avoiding bulky components and
dedicated configurations [157]. A review of dedicated and
integrated onboard charging systems is presented in the next
section.
1) DEDICATED CHARGERS
The conventional or dedicated charger is an independent
device with the single purpose of charging an EV battery by
providing conditional output power. Dedicated is small in size,
lightweight and is operated with single-phase or three-phase
AC power depending on the charging system by following
level 1 and 2 charging standards. The power level has been
trending upward from 3.6 kW single-phase chargers to 22 kW
three-phase chargers. A dedicated charger directly connects to
the AC wall socket (Mode 1 or 2) and relevant conversions
such as AC-DC and DC-DC power conversions are conducted
inside the onboard charger. Modern onboard chargers are
following IEC 61000 standards to reduce power quality
impacts on the grid. Commercial EVs have limited AC
charging power levels up to 22 kW (32A and 400V three
phase) due to space and weight limitations of the vehicle. The
main challenges of onboard chargers are dependence on the
charging outlet, voltage limitations of battery, DC controlled
with the AC voltage controller, and incompatibility of ground
referenced. Moreover, extensive safety requirements need to
be addressed at high power levels and the size and weight of
the vehicle may increase as increasing addition components.
Dedicated DC chargers (22 kW) are installed in houses,
workplaces, apartments, and shopping centers.
Most of the commercially available onboard chargers have
two-stage power converter topologies. The usual onboard
charging configuration includes an electromagnetic
interference filter, AC-DC converter, and isolated DC-DC
converter. Grid-side AC-DC converters are comprised of a
PFC circuit to limit harmonics and supply power to the DC
link as a first stage and then the DC-DC converter is connected
to the battery interface which is comprised of two inductors
and a capacitor (LLC) with two or four switches to supply
highly efficient power transfer. A large capacitor is required in
between two converters to filter grid frequency. Various
onboard charger topologies and control systems have been
reviewed in [158],[159],[149]. The onboard converter
topology of the 2016 Volt is shown in [160]. Most
conventional configurations of onboard chargers are
interleaved PFC boost converters and diode bridge converters.
According to General Motors’ evaluations, interleaved
topologies are widely used in front-end conversion stages for
modern onboard chargers [161]. The second-generation Volt
onboard charger is shown in Fig. 12(a) which comprises four
diode bridges and two parallel interleaved boost converters on
the grid side to enable approximately 400 V of intermediate
FIGURE 10. Configuration of conventional onboard EV
charger.
(a)
(b)
FIGURE 11. Configuration of onboard power electronic
interface: (a) Dedicated onboard charger (b) Integrated
onboard chargers.
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
18
DC link voltage. Resonant LLC full bridge converter is used
for the DC-DC conversion stage to acquire output voltage for
the battery.
The new version of the Tesla onboard charger adopted a
similar trend in the DC-DC conversion stage and three parallel
channels are integrated into the front end as shown in Fig.
12(b). The maximum charging capability of Tesla onboard
chargers is 11.5 kW and 240kW V3 superchargers are used for
EV battery charging in Tesla [162], [163]. Fig. 12(c) shows
the topology of Hyundai onboard chargers which can support
vehicle-to-device applications via bidirectional power flow.
The onboard charger is comprised of a front-end single-phase
active rectifier, and a bidirectional buck-boost converter
followed by a ducal active bridge to facilitate bidirectional
power flow as well as adjust the appropriate voltage for
different configurations [164]. Bridgeless boost-type PFC
topologies are also used in dedicated onboard chargers by
replacing passive diode rectifiers to reduce conversion stages
and power losses [165]. Matrix-type converters have been
introduced by Hella electronics by further reducing the
conversion stages. The matrix converter turns the input grid
frequency into the intermediate frequency and a larger DC
filter connects to the battery side in the Hella electronics
onboard charger shown in Fig. 12(d). The maximum
efficiency can be achieved up to 98% for a 7.2 kW single-
phase operation in this converter [166].
2) INTEGRATED CHARGERS
Integrated chargers have been designed to overcome the
limitations of conventional onboard chargers while preserving
their advantages including fast charging capability, reduced
components, cost, and volume of the charger [167]. Integrated
onboard chargers utilize a propulsion system, electric motor,
and inverter for battery charging by avoiding separate
convention stages with bulky add-on capacitors and inductors.
Therefore, they can offer bidirectional high-power levels
(Levels 1 and 3) and more space for the battery [168]. The
propulsion inverter operates as a bidirectional AC-DC
converter and motor winding provide galvanic isolation and
filter conductance [169], [170]. Split-winding AC motors are
used in non-isolated integrated chargers. However, single-
stage integrated chargers may have current ripples at the DC
side and need additional components to reduce voltage ripples.
The traction controllers may limit the charging power and the
electric motor may be operate in charging mode in integrated
chargers and technical requirements such as motor winding
limitations, and zero average torque may exist [171]. Renault
pioneered integrated charging design and Ford Motor
Company currently uses an integrated onboard charger that
combined battery charging and motor drive based on an
induction motor. Renault pioneered integrated chargers
[172],[154].
Most integrated chargers inversely use the electric drive
inverter as a boost stage with more than 50 kW power, and it
can utilize the propulsive components in the charging period.
Different types of integrated charging topologies have been
proposed in recent years using general DC-DC converters,
switched reluctance motors, or alternating motors [130]. In
[141], integrated converters are comprehensive analyses based
on the motor type either isolated or non-isolated cases. The
topology of the Renault Chameleon integrated charger is
shown in Fig. 13(a) which employs a reverse-blocking IGBT
rectifier with filtering components at the AC side for single
and three-phase AC grids [173]. As the first commercially
used first integrated charger, Chameleon chargers are
TABLE 11. Specifications of commercially available onboard chargers
MODEL AND MANUFACTURER
BATTERY
CAPACITY
(kWh)
CHARGING
POWER
(kW)
BATTERY
VOLTAGE
(V)
CHARGING TIME
(Minutes)
DRIVE RANGE
(km)
Model S, long range
- Tesla - 2022
100
200
400
24
624
Model 3 Performance
- Tesla - 2021
79.5
120
360
33
567
Bolt EUV
- Chevrolet - 2022
65
50
350
66
402
Leaf SL
- Nissan - 2019
62
100
360
35
346
Leaf S
- Nissan - 2019
40
50
350
36
378
Ioniq 5 Long Range
- Hyundai - 2022
72.6
160
800
18
412
e-208 GT
- Peugeot - 2019
50
100
400
30
450
Taycan 4S
- Porsche - 2022
79.2
225
800
21
407
MX-30
- Mazda - 2021
35.5
50
355
34
265
e-tron 55 Quattro
- Audi - 2022
95
150
396
26
441
Q4 Sportback 55
- Audi – 2022
82
110
400
38
460
i4 M50
- BMW – 2022
83.9
210
398.5
31
510
iX xDrive50
- BMW -2022
111.5
195
330
35
630
EQS 350
- Mercedes Benz - 2022
90.56
170
500
30
626
I-Pace S AWD
- Jaguar - 2020
90
100
388
43
470
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
19
currently used in Renault ZOE which is not required additional
components between operating modes as torque is not
generated in the motor [174]. The motor winding is function
as a DC link and the traction inverter is connected between the
motor and the battery to supply the required current for the
battery pack [175],[176]. The Chameleon charger is
designed to use the neutral point of the motor to turn the motor
inverter into three separate boost-type converters [149].
Configuration of motor winding or additional grid to motor
interface helps to enable high power charging without
producing torque in
the electric motor [149]. Valeo integrated charger is developed
using a triple H-bridge inverter which is connected to s
winding in the synchronous motor as shown in Fig. 13(b). The
inverter can provide high voltage at an intermediate DC-link
and a matching DC-DC converter is implemented between the
battery and inverters to adjust the battery voltage. Passive
rectifier and filter components are additionally used in
Continental high-power onboard chargers as shown in Fig.
(a)
(b)
(c)
(d)
FIGURE 12. Configurations of dedicated onboard charger (a) Second-generation Volt, (b) Tesla Model 3/Y, (c) Hyundai
vehicle-to-device, (d) Hella electronics/GaN systems.
(a)
(b)
(c)
(d)
FIGURE 13. Configurations of integrated onboard charger (a) Renault chameleon, (b) Valeo dual-inverter charger, (c)
Continental all charge system, (d) Galvanically isolated traction integrated charger
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
20
13(c). A high power charging rate is possible with a three-
phase current (400 V) and galvanic isolation provides
additional protection in Continental onboard chargers [177].
The multiphase integrated onboard charger presented [149]
has decoupled inductors in the motor and a multiphase AC-
DC converter that is directly connected to the battery.
overview of multiphase integrated onboards chargers can be
found in [178], [169]. Another type of integrated charger is an
isolated onboard charger which is equipped with
multiterminal motors to execute traction mode as well as
galvanic isolation during battery charging. Isolated integrated
charger topology is shown in Fig. 13(d) which included two
sets of three-phase motor winding. Stator windings are
normally connected in series to form a three-phase set
depending on the charging configuration. These dedicated
chargers can be used for single-phase systems as well as
operates as a high power isolated bidirectional fast charge is
unity power factor [179]. Commercially available onboard
chargers are presented in Table 11 with specifications
including battery voltage, capacity, charging power, charging
time, and driving range. Most modern electric cars utilized
high voltage batteries (up to 800V) and hence isolated high-
voltage transmission system is added for safety.
C.
OFFBOARD CHARGERS
Offboard chargers are integrated with DC fast charging or
ultra-fast charging systems for high power flow (> 20 kW)
between the utility grid and battery based on level 3 or extreme
fast charging standards. The power conversion stage of the
offboard charger is located outside of the EV and therefore the
volume, weight, size, and cost of the charger are significantly
reduced when compared to the onboard charger [7]. As a
conductive charging process, EV offboard chargers are
incorporated with either AC bus or DC bus configuration [48].
Most fast and ultrafast charging systems prefer AC bus-
connected fast charging stations due to well-equipped
configurations and matured power converters on the AC
power grid. Offboard charges consist of two converter stages
AC-DC and DC-DC conversion to adjust the DC current
before reaching the EV as shown in Fig. 14. Central AC-DC
converter is connected to the low-frequency transformer on
the grid side in the DC bus connected to offboard charging
systems. The DC-DC converter is connected to the DC link to
provide DC power to the battery. DC bus-connected systems
are more efficient and flexible than AC bus-based fast
chargers and RESs can be connected via DC link and grid-side
impacts are simply avoided [48]. Moreover, AC and DC bus-
based configurations are also available for offboard chargers.
However, fast charging stations have some drawbacks
including high infrastructure costs, safety requirements,
complex control strategies, and communication protocols that
need to be used according to the standards [180]. A review of
offboard charger topologies and control techniques have been
presented in [181], [145], [112], [182].
Integrated EV chargers can be classified as converter-
integrated and machine-integrated which are comprehensively
reviewed in [183]. The power grid is connected to the inverter
through machine winding in single-stage integrated chargers
that behave as an input filter. In two-stage chargers, the battery
powers the traction machine through an inverter and a PFC
circuit and AC-DC converter are implemented between the
motor and the electricity grid. A comparison of different
winding configurations in EVs is presented in [184] and
hairpin winding for electric motors are evaluated in [185]. The
fast three-phase charging has been proposed in [186] which
AC three-phase mains are linked to the middle point of each
motor winding through an EMI filter and protection
component.
Modern offboard chargers can provide more than 350 kW
power to the EV battery for ultrafast charging and are
compatible with 800 V EVs in near future. Most of the
offboard charging topologies are employed with galvanic
isolation in the DC-DC converter stage using a high-frequency
transformer (50 kHz – 300 kHz) instead of a line-frequency
transformer to provide safety for the components, better
control of voltage adjustments, and compactness [141]. Most
EV manufacturers tend to design chargers by modularizing to
achieve compatibility, high efficiency, and economic benefits
from their chargers. Specifications of currently available ultra-
fast and fast charging systems are presented in Table 12. Terra
53/54 series fast charger is designed based on a power
electronic building block (PEBB) by ABB as a benchmark for
offboard chargers as shown in Fig. 15(a). The PEBB is a
widely accepted concept which incorporates several
topologies to reduce cost, size, losses, and components of the
applications [187]. The number of active power stages varies
with output requirements and an isolated DC-DC converter is
used to meet high power level and isolation requirements. The
modular system of ABB Terra 53/54 fast charger is designed
by replicating the same type of PEBB (5 × 3 PEBBs to Reach
50 kW) and efficiency is 94% [188],[189]. ABB Terra high
power charger series is shown in Fig. 15(b) which is also
configured with the modular system (three PEBB to reach 150
kW high power). An isolation transformer and LCL filter are
used to reduce grid side harmonics and an active rectifier and
interleaved buck converter are used in the modular
configuration in high-power ABB Terra offboard charger.
Porsche fast charger can manage 800V with modular fast
charging topology. Porsche Modular Park A and park B fast
charging configurations are shown in Fig. 15(c) and (d)
respectively. A phase-shifting transformer is used after the
FIGURE 14. Configuration of conventional offboard charger.
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
21
input filter to provide galvanic isolation and improve the
power quality of the AC grid side in both configurations.
Three-phase passive rectifier and boost PFC converter used
after phase shift transformer and DC-DC buck converter
utilized to lower current ripple and step-down voltage as
required for EV battery in Porsche Modular Park A fast
charger [190]. A combination of the Vienna converter and
three-level interleaved buck converter enables modifications
in the battery charging converter to provide PFC, reduce
current ripples, and be compatible with other configurations in
Park B fast charger [191], [192]. DC fast chargers are still in
the developing phase and therefore standards and protection
requirements are not well established due to specifications in
high power, complex grounding topologies, and fault types
[193]. Moreover, protection and metering requirements are
critical for bidirectional fast chargers as they are very sensitive
to grid disturbances and a review of coordination techniques
is presented [194]. Tesla superchargers have a combination
of PEBBs (13 x 3 PEBBs) to provide 150 kW power with 92%
efficiency as shown in Fig. 15(e). The simplified one-line
diagram of the Tesla supercharging station is presented in
[188].
VI. CONVERTER CONFIGURATIONS OF EV CHARGING
SYSTEMS
The power electronic converters are an integral part of
electrification to achieve efficient, and reliable operation of
EV charging systems. As advances in power electronic
techniques have made conversions possible to achieve cost-
effective and maximum power conversion. The power
converter topologies are interfacing between the EV battery
system and power network which is responsible for improving
charging performances and controllability of the charging
system [195]. Moreover, advanced power converters and
controllers are continuously developing with the increasing
integration of EV charging systems into the RESs in recent
years. The AC-DC converters and DC-DC converters are
equipped with EV charging systems to supply power to the
vehicle components and deliver power from a power grid to
an onboard high-voltage battery pack. The AC-DC converters
are used for rectification and power factor correction (PFC) of
the EV charging system and are further able to control
charging cost and complexity and improve power quality. The
(a)
(b)
(c)
(d)
(e)
FIGURE 15. Configurations of offboard chargers (a) ABB Terra 53/54 50-kW fast charger, (b) ABB Terra HP 150-kW high-
power charger, (c) Porsche modular fast charger Park A, (d) Porsche modular fast charging Park B, and (e) Tesla V2
Supercharger
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
22
front end of the charger consists of the AC-DC converter to
convert single/three-phase power to DC power and supply the
required DC link power and function as a power factor
corrector topology. The DC-DC converters are primarily
employed in an EV charging station, classified as
unidirectional or directional converters and isolated or non-
isolated power converters [159].
The significant advantages of EVs over many other
conventional clean energy applications are due to
improvements in converter topologies. The improved power
converters in EV charging systems can operate
bidirectionally concerning the power demand of the grid,
improve power quality and provide ancillary services. The
simplified diagram of a conventional EV system is shown in
Fig. 16 which comprises with DC-DC converter, AC-DC
converter, and filter in between the EV battery and grid. The
AC-DC converter rectifies AC voltage to regulated
intermediate DC link voltage and the DC-DC converter
controls the DC input voltage for the EV battery. The control
system is maintained the transient and steady-state
performance of the system by providing relevant control
signals for converters. Moreover, PFC techniques are
implemented parallelly with the AC-DC converter to achieve
a unity power factor and overcome current harmonic impacts
[206]. The PFC circuit is sensing input voltage and current and
then controls the input currents close to sinusoidal and in phase
with relevant voltages by controlling the converter switches.
The desired DC link voltage is regulated via a DC-DC
converter to charge the EV battery.
A.
AC-DC CONVERTERS
The AC-DC converter provides the interface between the
DC link and the power grid by providing high power quality
on the DC and AC sides of the charging system. They are
generally designed as single-phase H-bridge inverters or three-
phase three-leg inverters either controlled or uncontrolled
rectifiers [137]. The AC-DC conversion is the first stage of the
EV charging system, and it controls reactive power
consumption and grid-side current harmonics [207]. The PFC
technique is implemented in the AC-DC converter to supply
efficient and safe power output to protect the connected
devices, users, and the grid. The AC-DC converters can be
classified as unidirectional and bidirectional as well as single-
stage and multistage AC-DC power converters. The
unidirectional chargers deliver G2V operation (charging) with
a low-cost and simple charging structure and supply moderate
grid support with minimum power infrastructure
modernization [208]. Conversely, bidirectional converters can
offer G2V and V2G (charging and discharging) operation with
advanced and coordinated control between EV, charging
station, and grid with a high level of ancillary services.
The single-stage AC-DC converter is combined with a DC-
DC converter which reduced expensive components including
DC link capacitors and inductors in the system. However, a
single-stage converter has less output voltage range and non-
isolated converters have a limited conversion ratio [158]. The
single-stage modular three-phase AC-DC converter is
introduced in [209] to voltage regulation and PFC and single
phase isolated AC-DC converter is proposed in [210] from a
TABLE 12. Specifications of currently available ultra-fast and fast chargers.
Model
Input Voltage
(Vac)
Output
voltage
(Vdc)
Output
current
(A)
Power
(kW)
Supported Protocols
ABB Terra 54 [196]
400 Vac +/- 10 %
150-500
125
50
CHAdeMO, CCS
ABB Terra High Power GEN III [197]
400 Vac +/- 10 %
150-920
500
350
CHAdeMO, CCS1, CSS2
Tesla Supercharger V3 [198]
380 - 480 Vac
880-970
640
250
Superchargers
Signet FC100K-CC [199]
480 Vac
150-500
200
100
CHAdeMO, SAE Combo
Tritium PK350 [200]
480 Vac
200-920
200-500
350
CHAdeMO, CSS2
Blink 60kW DCFC [201]
480 Vac
150-500
140
60
CCS1
Blink 180kW High Power DCFC [202]
480 Vac
150-1000
240
180
CCS1
EVBox Troniq 100 [203]
400 Vac
50-500
200
100
CHAdeMO, CCS2
Siemens VersiCharge Ultra 175 [204]
480 Vac +/- 10 %
200-920
200-350
178
CHAdeMO, CCS
Ingeteam - INGEREV RAOID ST400 [205]
380-440 Vac
50-920
500
360
CHAdeMO, CCS
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
23
differential boost converter by using the AC decoupling
waveform technique to address reliability issues. In contrast,
multistage converter topologies are designed with two or more
converter levels and high-power levels of the converter are
provided efficient and reliable control for the charging system.
The two-level and three-level voltage source converters are
widely used for charging applications including buck/boost
converters and multilevel converters. Moreover, the filter is
connected between the AC-DC converter and the power grid
to reduce harmonics, and di/dt on semiconductors, and isolate
the converter from the power grid [211]. The commonly used
filters are LC and LCL filters for AC-DC converters and more
advanced filters are used for fast and ultra-fast charging
stations.
1) BUCK-TYPE RECTIFIER
The buck type of converter is used to regulate the output
voltage which is lower than the input voltage with
unidirectional power flow. The three-phase buck converter has
a wide range of features in the AC-DC power stage when
compared to the three-phase boost-type converters. They have
a wider voltage control range, inherent inrush-free direct
startup, allow dynamic current limitation at the output, provide
overcurrent protection during short circuits, and can maintain
PFC capability at the input side [212],[213]. The buck
converter-based PFC topologies can be classified as
bridgeless, interleaved, and bridgeless interleaved buck
converters [214]. The conventional six-switch three-phase
buck converter shown in Fig. 17 (a) includes three legs that are
connected to the three phases and one freewheeling diode to
lower the conduction losses during the freewheeling
condition. The freewheeling diode is divided into a series
connected by two diodes and the common node is connected
to the input neutral point in the study [215] to reduce voltage
stress on the converter switchers. Conventional buck
converters are employed for low-power charging systems (<
300 W) due to their capability to provide improved power
quality and efficiency at different line voltages [214]. The
input filter is critical for the buck converter as shown in Fig.13
(a) to reduce the inherent input current disturbances (high
ripple) from the charging system [216].
The bidirectional five-level buck converter has been
proposed in [217] which is employed two voltage sensors with
a complex control strategy to balance voltages across the two
capacitors and high voltage side power switches ratings are
equal to twice the DC voltage output. The distributed parasitic
capacitance of the high-density three-phase buck converters is
a major challenge in high-frequency operation which lead to
input current distortion and an increase in THD under light
load condition. The modified three-phase buck converter has
been presented in [218] to reduce the impact of distributed
parasitic capacitance between the DC link output and the
system ground. Moreover, high step-down voltage gain may
appear when the multiple EVs charging due to variations in
the range of the EV battery. Furthermore, power quality
impacts and losses increase when the voltage output is less
than three quarters of input voltage due to decreasing
modulation index of less than 0.5 of the standard buck
converter. The matrix-based three-phase buck converter has
been implemented in [219],[220] to regulate the modulation
index and improve grid support.
2) BOOST-TYPE RECTIFIER
DC voltage output, low current stress and THD,
bidirectional power flow, and high efficiency with a simplified
control scheme. The boost converters are integrated with PFC
configuration for EV charging systems which are operating in
continuous conduction mode which is selected for medium
and high-power applications. The boost converter exhibits
lower conducted electromagnetic interference (EMI) than
other buck and buck-boost converters because of continuous
current flow capability [221]. The main limitation of this
converter is high conduction losses due to the current flowing
via semiconductor components and the diode recovery losses
are imposed by the high-frequency operation of the converter
[7]. The three-phase six-switch boost converter shown in Fig.
17(b) consists of six switches in the there-legs and an LC filter
to reduce input current harmonics and boost the voltage. The
switchers upper and lower are executed in complementary and
inductors are employed to boost the voltage and reduce input
current harmonics. The three-phase three-level boost
converters can balance the input AC system during
unbalanced input voltage and reduce harmonics at the DC link
voltage by employing a bulky capacitor or developing an
active control method [222]. The power losses increased in
conventional boost converter topology at a high-power rate
due to the high ripple occurs at the output capacitor.
The EV charging systems incorporate a variety of boost
converter topologies, including bridgeless, interleaved, and
bridgeless interleaved boost topologies. In addition,
asymmetrical, and symmetrical bridgeless boost rectifiers
have enhanced efficiency when compared to the regular boost
converter due to the fewer operating electronic devices. The
semi-bridgeless boost rectifier is presented in [223] for font-
end AC-DC converter of PHEV charger to minimize the
charger size, cost, and EMI and increase efficiency at light
load. The isolation approaches such as power supplier
separation or transformers are used in high-power applications
to avoid current circulating which may increase the volume,
passive components, and cost of the system. The parallel
three-phase boost converter circuit has presented in [224] with
FIGURE 16. Block diagram of conventional EV charging system.
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
24
the potential of zero-sequence current circulating capability,
modular design, and high efficiency. The harmonics of the
unbalanced ac input voltage can be mitigated by adding a
bulky capacitor and improving active control techniques to
reduce harmonics in the DC-link voltage [225]. The magnetic
circuit effects and size of the converter can be reduced by an
interleaving of boost-type two converters which doubles the
switching frequency and improved energy efficiency [142].
3) SWISS RECTIFIER
The Swiss converter is a buck-type PFC converter topology
suitable for EV charging systems with 250 - 450V DC bus
voltage and 380 V three-phase AC voltage [226]. The Swiss
converter has low common mode noise, switching losses
lower complex power circuits, control strategy, and inherent
free inrush limitation [227],[228]. The Swiss converter is
implemented with three phase unfolder circuit and two DC-
DC buck converters. The Swiss converter's three-phase
unfolder electric circuit uses two full bridge circuits to
transform the AC voltage into time-varying two positive
voltages. As a result, fewer high-frequency transistors are
required than in single-stage isolated converters. The
schematic of eight switches Swiss converter is shown in Fig.
17(c) comprises an uncontrolled three-phase converter bridge
and three sets of low-frequency bidirectional switchers Sya,
Syb, and Syc which can be defined as six voltage segments
concerning the frequency of the phase voltage. The two active
switches T+ and T- operate corresponding to the two-phase
voltage which is involved in generating output voltage [48].
The single-stage full-bridge Swiss converter is presented in
[226] and the midpoint clamper is used to integrate the PFC
method of the converter. The system achieved 95.4%
efficiency under half-rated power in a 10kW system and
showed 5% input current THD under-rated power. The higher
switching frequency or increased AC input filter is used to
decrease voltage and current ripples at the input. But those
options may increase the volume, cost, and losses of the
system. The interleaving of Swiss rectifiers can be used to
overcome the above drawbacks and offer high reliability,
power, and bandwidth, low current and voltage ripple at the
input and output as well as lowering filter requirement. The
three-phase Swiss converter with interleaved DC-DC output
has been presented in [229] and the efficiency of the system is
99.3% in the 8 kW rated power. The multilevel Swiss rectifiers
are also used for high-power applications but the control
scheme becomes complex [230]. Moreover, bidirectional
Swiss converters can be incorporated with the smart
coordinate controller to operate V2G in EV charging systems
[231].
4) VIENNA RECTIFIER
The Vienna converter is used to supply controlled DC bus
voltage in high-power applications and performs as a three-
phase boost-type PFC rectifier. Vienna converter provides
many advantages when compared to the other three-level
converters such as high-power density, efficiency, stable
voltage output, reduced number of switches, low voltage stress
of the semiconductor, lower THD, unity PF, and neutral
connection-free structure [232],[233]. Conventional control
methods of the Vienna converter are sliding mode variable
strategy, hysteresis current control, and double closes-loop
control techniques which can be used to regulate the voltage
of the DC-link and unity PF. Moreover, the dead zone is not
required to drive switches and voltage stress on the switches
appears on half of the two-level converter at the same DC link
voltage [234]. The schematic diagram of three phase Vienna
converter is shown in Fig. 17(d). The converter is consisting
of three inductors for the boost state at the input side, three
power bridges for three phases, and two series output split
capacitors on the DC link. Power flow of this converter is
unidirectional, and each power bridge comprises two fast
rectifier diodes and two reverse series connected switchers.
The Vienna converter is designed to enhance the large-scale
integration of EVs on the grid [235] using a virtual
synchronous machine control strategy. The sliding mode
control loop method is utilized in a three-phase AC-DC
Vienna rectifier in [236], which consists of loss-free resistor
behavior in each phase for PFC. The three-phase interleaved
Vienna rectifier is implemented in [237] by focusing on
switching frequency circulating current generation with
interleaving control. The efficiency of the converter is 99.98%
in a 3kW prototype at normal load conditions. Furthermore, a
comparison of power losses of different Vienna converter-
based configurations is analyzed in [237] and it was found that
the lowest power loss belongs to three phase Vienna converter.
In [48] bidirectional Vienna converter is implemented for
V2G operation by replacing six fast rectifier diodes of Fig. 17
(d) with switchers to modify it as a T-type PFC configuration.
The bidirectional T-type PFC Vienna converter has higher
efficiency, and lower conduction losses and it is suitable for
V2G operation and storage applications. Additionally, the
Vienna converter works with bipolar DC-bus structures,
which improve power flow capabilities while lowering DC-
DC power stage step-down ratio [238].
5) MULTILEVEL AC-DC CONVERTER
Multilevel converters are widely accepted for AC-DC
conversion in fast and ultra-fast charging applications over
other converters due to several reasons. The multilevel
converter concept is developed for high voltage and power
applications with the ability to unidirectional and bidirectional
power flow, transformer-less operation, and high-quality
outputs [239],[240]. The level 3 EV charging systems
comprise multilevel converters as they provide high efficiency
and power density as well as supply alternating voltages from
various lower dc voltages [241]. The functionality of the
multilevel inverter is depending on either an isolated DC
source or a series of connected split capacitors which are
connected to the single DC source to provide sub-level voltage
outputs [242]. The multilevel converter topologies can be
categorized as cascaded converters, neutral point clamped
(NPC), and flying capacitors as shown in Fig. 18. The
cascaded multilevel converters can be divided into cascaded
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
25
H-bridge (CHB) and modular multilevel converter (MMC).
The hybrid multilevel converters are designed by using two or
more of the mentioned converter topologies [243].
The neutral point clamped converter is used in low and
medium voltage operation applications which can reduce
harmonics, and dv/dt stress across converter switches, enhance
the power capability of the EV charging stations and reduce
step-down effort by DC-DC charger [244]. The three-phase 3-
level NPC multilevel AC-DC converters are shown in Fig.
17(e) and the switching loss can be reduced by blocking all
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
FIGURE17. AC-DC converter configurations (a) Three-phase six-switch buck-type converter, (b) Three-phase six-switch boost
converter, (c) Three-phase Swiss converter, (d) Vienna converter (e) Three-level neutral point clamped (NPC) converter, (f)
Three-phase three-level flying capacitor inverter, (g) Cascaded H-Bridge (CHB) multilevel active rectifier, and (h) Modular
multilevel inverter.
This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and
content may change prior to final publication. Citation information: DOI 10.1109/ACCESS.2023.3267164
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. For more information, see https://creativecommons.org/licenses/by-nc-nd/4.0/
26
switches to half of the DC-link voltage. The NPC with a
central AC-DC converter is designed for the EV charging
system in [245] via a medium voltage grid and bipolar DC bus.
However, uncertainties of random EV connections and
unbalanced problems in bipolar DC buses are unable to control
with the NPC modulation stage. Therefore, an additional
circuit was added to the NPC converters for voltage balancing
with the three legs [246]. The next multilevel type is a flying
capacity multilevel converter which required lower
component volume, used low voltage switches, and has fewer
losses than other converters [247]. The schematic of three
phases three-level flying capacitor multilevel converter is
shown in Fig. 17(f). The flying capacitor with closed-loop
control techniques is presented in [248] and six levels
interleaved flying capacitor converter is proposed in [249] to
achieve high power density and efficiency.
The cascaded H-bridge multilevel converter is comprised of
a series of connected H-bridge (full bridge) cells that are
coupled in cascade on the AC voltage side [250]. The output
waveform of the synthesized multilevel converter includes
more steps as the level count increases, which generates a
staircase wave with the intended waveform [251]. The
modular structure of the multilevel converters or modular
multilevel converters (MMC) is the most attractive AC-DC
converter used in EV and RES applications. The cascaded H-
bridge multilevel and modular multilevel converters are
shown in Fig. 17(g) and (h) respectively. The MMC is playing
a major role in the industry due to its advantages over other
converters [252]. The MMC is commonly used in RES and
EV charging systems to mitigate large-scale grid integration
and improved power quality. The large EV or HEV drives and
EV charging stations are utilized with modular multilevel AC-
DC converters [241]. A novel MMC topology was proposed
in [253] which compensates for voltage imbalances.
B. DC-DC CONVERTERS
Th