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A Comprehensive Review of DC Fast-Charging Stations With Energy Storage: Architectures, Power Converters, and Analysis
Abstract
Electric vehicle (EV) adoption continues to rise, yet EV sales still represent a small portion of vehicle sales in most countries. An expansion of the DC fast charging (DCFC) network is likely to accelerate this revolution towards sustainable transportation, giving drivers more flexible options for charging on longer trips. However, DCFC presents a large load on the grid which can lead to costly grid reinforcements and high monthly operating costs – adding energy storage to the DCFC station can help mitigate these challenges. This paper performs a comprehensive review of DCFC stations with energy storage, including motivation, architectures, power electronic converters, and a detailed simulation analysis for various charging scenarios. The review is closely tied to current state-of-the-art technologies and covers both academic research contributions and real energy storage projects in operation around the world.
... In on-grid operation, the MCS, despite being mobile and capable of being transported to the electric vehicle, operates connected to the power grid. In this situation, the energy storage system of the MCS operates as an interface that enables the use of fast or ultra-fast charging, even if its connection to the grid is made through a slow-charging converter (such as the AC charger block in Figure 2), similar to DC fast-charging architectures that use ESSs [35,36]. On the other hand, its distinguishing feature is its off-grid operation, where the electric vehicle connected to the MCS is directly charged from the energy storage system. ...
... The PSFB converter (Figure 10a) features ZVS capability at the turn-on of the primary switches, which allows it to operate at a high switching frequency, resulting in a good power density. Despite having some dependence on the load to achieve ZVS, this topology has proven suitable for fast EV charging applications, as the ZVS switching range can be adjusted by the designer [36,99]. However, the PSFB converter has certain drawbacks, such as losses during primary switch blocking and conduction losses in the secondary diodes. ...
... For this converter, voltage regulation is usually performed by varying the switching frequency, making the design of passive components more complex. In cases where large variations in voltage gain are not required, the switching frequency remains within a narrower operating range, improving operational efficiency [36]. However, for the application in question, this is not the case, as the battery voltage varies over a wide range. ...
The adoption of electric vehicles (EVs) has shown exponential growth in recent years, with expectations for further development in the years to come. With such significant expansion, efforts and incentives are shifting from EV sales to projects aimed at expanding charging station infrastructure. In order to sustain this growing trend, a reliable and robust charging infrastructure is needed. However, the entire process of planning, designing, and constructing fixed charging stations (FCSs) is time-consuming and expensive. In this scenario, mobile charging stations (MCSs) offer a complementary solution to ensure the necessary reliability for the improvement of EV owners’ experiences in the electrified transportation sector, as they help reduce range anxiety, peak-hour costs, and waiting times. In this sense, this paper aims to disseminate the state-of-the-art research and studies on MCSs, covering topics such as architectures, standards, converter topologies, and market solutions.
... The ESS can be charged when electricity demand is high, and prices are low, and EVs could be charged with more electricity from the ESS without overloading the Grid at a fixed flat rate. In rural places with low grid capacity, building an ESS-based charging point may be cheaper and more straightforward than improving the grid infrastructure [121]. 6.2.1.2. ...
... Fig. 46 depicts the topology of an individual ESS. The different storage options for EVCS are addressed in Table 15 [121]. Table 16 represents the comparison of different one-system energy storage topologies. ...
... A typical DC-bus BESS DCFC architecture has to provide AC-DC conversion, PFC, voltage regulation, and battery-grid isolation [121]. In the event of damaged battery housing, the battery-grid isolation prevents ground problems. ...
Electric vehicles (EVs) are popular now due to zero carbon emissions. Hence, with the advancement of EVs, charging station (CS) design also plays a vital role. CS is generally called a charge or power supply point and delivers power to the EVs. Usually, CSs are either of the direct current (DC) type, as the EVs need a DC supply or in some cases of the alternating current (AC) type, as the traditional power grid delivers AC power. Usually, on-board chargers (on-BCs) and off-board chargers (off-BCs) are used to charge the EV batteries. Due to heavy loads, size, and budget constraints, many on-BC facilities have power limits, which can be overcome by designing the on-BC with an electrical motor. In different types of off- and on-BCs, the power flow can be in one or two directions. Uni-directional power flow reduces hardware needs and makes connecting problems easier, whereas bi-directional power flow allows battery energy to be injected back into the grid. The primary issue with EVs is the charging time as well as the need for charging infrastructure. The infrastructure for fast charging makes on-board energy storage less expensive and more essential. This paper details various charging technologies, including wired and wireless methods. Also, numerous on-board and off-board charging topologies are summarized in the literature. Different EV battery charging standards and levels are also discussed. The paper also delineates several alternative CS topologies based on architecture, energy storage, and renewable energy sources. Considering the present scenario, having a sophisticated quick EV charging network is crucial to ensure maximum EV charging with renewable power and reduce grid strain.
... The grid impact of DC fast charging stations was examined in [17]. Energy storage systems for DC fast charging stations were discussed in [18]. Even though these reviews covered numerous power converters adopted in DC fast charging stations and are milestones in this field, the arrival of new EV models with 800 V powertrains on the market creates the need for low-cost single-stage DC-DC converter topologies capable of interfacing both the traditional 400 V and the new 800 V powertrains. ...
... This subsection aims to show the benefits provided by the adoption of BESSs in DC fast charging stations, which are, respectively, savings of grid reinforcement costs and opera-tional cost as well as better on-site utilization of RESs [18], [26]. Moreover, some examples of architecture employing BESSs will be described. ...
... BESSs are advantageous solutions where the grid infrastructure is weaker, like in highway and countryside settings, where DC fast charging stations are needed for long-distance trips. In such cases, in fact, the improvement of the grid infrastructure would be much more expensive than the installation of BESSs [18], [26]. The installation of BESS for avoiding grid reinforcement costs has been evaluated in [152]. ...
This paper aims to review the main research points regarding DC fast charging stations. At the beginning, the paper addresses an overview of DC fast charging standards, galvanic isolation, EV powertrain, and some examples of real DC fast chargers. This part highlights that DC fast chargers are usually connected to an AC network or microgrid, whereas DC microgrids would be a better choice to increase the charging efficiency and reduce the costs. However, the lack of standards in terms of protection and metering made their spread limited for the moment. Moreover, the paper describes the power converter topologies typically adopted in DC fast charging stations and emerging solutions to interface EVs with both 400 V and 800 V powertrains. Then, the paper explains the main architectural features of DC fast charging stations connected to DC networks or microgrids because of their potential to become the standard infrastructure in this field. Furthermore, the energy management strategies for DC fast charging stations are discussed, taking into account their relevant goals. Finally, cybersecurity issues of charging stations are covered, also considering their impact on grid and electric vehicle supply equipment, and providing a particular discussion regarding DC fast charging stations
... This has sparked an increased interest in bidirectional chargers among researchers as a growing option for future EV applications. Charging units in AC busbased architectures use separate rectifiers, enabling efficient and independent charging of multiple vehicles [25]. In contrast, systems with a common DC bus provide versatility and high-power operation [26,27]. ...
... EV charging systems utilize multiple AC-DC and DC-DC converters and control strategies for safe and efficient battery charging, with the converter topology choice affecting the cost, size, performance, and efficiency of the system [31][32][33][34]. High-power converters can reduce charging time and provide additional grid services [25,35]. The increasing number of EVs and the incorporating renewable energy sources into the grid pose challenges to power quality, grid operation, safety, and reliability [36][37][38]. ...
... Tesla Superchargers are exclusively designed for Tesla vehicles and offer fast DC charging capabilities. These chargers are unique to Tesla and cannot be used with other electric vehicle brands [25]. Superchargers possess the ability to generate power outputs reaching a maximum of 250 kW, possibly adding up to 200 miles of range in just 15 min [72]. ...
Electric vehicle (EV) fast charging systems are rapidly evolving to meet the demands of a growing electric mobility landscape. This paper provides a comprehensive overview of various fast charging techniques, advanced infrastructure, control strategies, and emerging challenges and future trends in EV fast charging. It discusses various fast charging techniques, including inductive charging, ultra-fast charging (UFC), DC fast charging (DCFC), Tesla Superchargers, bidirectional charging integration, and battery swapping, analysing their advantages and limitations. Advanced infrastructure for DC fast charging is explored, covering charging standards, connector types, communication protocols, power levels, and charging modes control strategies. Electric vehicle battery chargers are categorized into on-board and off-board systems, with detailed functionalities provided. The status of DC fast charging station DC-DC converters classification is presented, emphasizing their role in optimizing charging efficiency. Control strategies for EV systems are analysed, focusing on effective charging management while ensuring safety and performance. Challenges and future trends in EV fast charging are thoroughly explored, highlighting infrastructure limitations, standardization efforts, battery technology advancements, and energy optimization through smart grid solutions and bidirectional chargers. The paper advocates for global collaboration to establish universal standards and interoperability among charging systems to facilitate widespread EV adoption. Future research areas include faster charging, infrastructure improvements, standardization, and energy optimization. Encouragement is given for advancements in battery technology, wireless charging, battery swapping, and user experience enhancement to further advance the EV fast charging ecosystem. In summary, this paper offers valuable insights into the current state, challenges, and future directions of EV fast charging, providing a comprehensive examination of technological advancements and emerging trends in the field.
... The widespread usage and rise in the EV charging demand will affect the electric grid (Negarestani et al., 2016;Rafi and Bauman, 2021). The EV charging stations can affect the electric grid stability and overload the distribution system (Khalid et al., 2019). ...
... The study considered different types of ESS technologies which include Li-ion battery, lead-acid, redox flow battery, sodium-sulfur, sodium metal halide, zinc-hybride cathode, sodium-ion battery, flywheels (Beacon Power, 2021;Kane, 2021;Mongird et al., 2019;Patel, 2021;Rafi and Bauman, 2021). The Li-ion batteries are deployed across various industries due to their high power density, high energy density, and performance (Mongird et al., 2019). ...
... The flywheels have longer life cycles and fast response time, making them suitable for frequency regulations and renewable smoothing (Mongird et al., 2019). The data related to different types of ESS, their characteristics, and their feasibility to serve at the DCFC locations is obtained from various studies in the literature (Beacon Power, 2021;Cole et al., 2021;Kane, 2021;Mongird et al., 2019;Patel, 2021;Rafi and Bauman, 2021). The following table represents the characteristics and project costs of different ESS: ...
This report provides a framework to develop policies and infrastructure for supporting plug-in electric vehicles (EV) charging demand and grid integration through distributed energy resources (DER). The developed comprehensive approach is funded and supported by the Michigan Department of Environment, Great Lakes, and Energy (EGLE). Researchers at Michigan State University lead the modeling framework development and execution. The EV charging demand is predicted to increase the load on the electric grid. Hence, a modeling framework is required to predict the optimum investment technology supporting EV fast-charging demand and reducing the load on the grid. This study estimates the optimum size, type, and location of the DER to support the direct current fast charging (DCFC) demand in 2030. The study captures the existing load on the grid, and the capacity constraints of the grid network, while predicting the optimum investment technology. The potential load from DCFC is derived from the previous study on DCFC station locations for supporting urban trips across Michigan for the year 2030, conducted by the same research team at Michigan State University and supported by EGLE.
... Electric vehicle (EV) DC fast-charging (DCFC) stations have the benefit of providing faster charging times to EV customers and reducing range anxiety [1][2][3][4]. However, the integration of DCFC stations into the electric grid brings a number of challenges, including rising energy demand and peak power requests, the need for grid upgrades, the potential decline in grid reliability, the degradation of power quality and increased losses [4][5][6][7]. ...
... Traditional DCFCs are often interconnected to the grid at the medium-voltage (MV) level due to high power requests; this requires distribution-level transformers to convert MV to low voltage (LV) for the DCFC equipment [1,4]. In various reports and studies, it is shown that high load requirements from simultaneous charging of EVs might not be supplied by the available distribution-level transformers, and it is most likely that upgrades are required to accommodate DCFC stations [9]. ...
The growing demand for high-power DC fast-charging (DCFC) stations for electric vehicles (EVs) is expected to lead to increased peak power demand and a reduction in grid power quality. To maximize the economic benefits and station utilization under practical constraints set by regulatory authorities, utilities and DCFC station operators, this study explores and provides methods for connecting DCFC stations to the grid, employing low-power interconnection rules and distributed energy resources (DERs). The system uses automotive second-life batteries (SLBs) and photovoltaic (PV) systems as energy buffer and local energy resources to support EV charging and improve the station techno-economic feasibility through load shifting and charge sustaining. The optimal sizing of the DERs and the selection of the grid interconnection topology is achieved by means of a design space exploration (DSE) and exhaustive search approach to maximize the economic benefits of the charging station and to mitigate high-power demand to the grid. Without losing generality, this study considers a 150 kW DCFC station with a range of DER sizes, grid interconnection specifications and related electricity tariffs of American Electric Power (AEP) Ohio and the Public Utility Commission of Ohio (PUCO). Various realistic scenarios and strategies are defined to account for the interconnection requirements of the grid to the DCFC with DERs. The system’s techno-economic performance over a ten-year period for different scenarios is analyzed and compared using a multitude of metrics. The results of the analysis show that the the integration of DERs in DCFC stations has a positive impact on the economic value of the investment when compared to traditional installations.
... Electric Vehicles (EVs) DC Fast Charging (DCFC) stations have the benefit of providing faster charging times to EV customers and reducing range anxiety [1][2][3][4]. However, the integration of DCFC stations into the electric grid brings a number of challenges, including rising energy demand and peak power request, needs for grid upgrades, potential decline in grid reliability, power quality degradation, and increased losses [4][5][6][7]. ...
... Traditional DCFCs are coupled to the grid at the Medium Voltage (MV) level due to the high power connection, this requires distribution level transformers to convert MV to Low Voltage (LV) for the DCFC equipment [1,4]. In various reports and studies, it is shown that high load requirements from simultaneous charging of EVs might not be supplied by the currently installed distribution level transformers on the utility levels and most likely require an upgrade to accommodate DCFC stations [9]. ...
The growing demand for high-power DC Fast Charging (DCFC) stations for Electric Vehicles (EVs) is expected to lead to increased peak power demand and reduction of grid power quality. To maximize the economic benefits and station utilization under practical constraints set by regulatory authorities and DCFC station operators, this study explores and provides methods for connecting DCFC stations to the grid employing low power interconnection rules and Distributed Energy Resources (DERs). The system uses automotive Second Life Batteries (SLBs) and Photovoltaic (PV) systems as energy buffers and local energy resource to support EV charging and improve the station techno-economic feasibility through load shifting and charge sustaining. The optimal sizing of the DERs and the selection of the grid interconnection topology is achieved by means of a Design Space Exploration (DSE) by means of exhaustive search approach to maximize the economic benefits of the charging station and to mitigate high-power demand to the grid. Without loosing of generality, this study considers a range of DER sizes, grid interconnection specifications, and related electricity tariffs of American Electric Power (AEP) Ohio and the Public Utility Commission of Ohio (PUCO). Various scenarios and strategies have been defined to account for the interconnection requirements of the grid to the DCFC with DERs. The system’s techno-economic performance of different scenarios has been analyzed and compared using a multitude of metrics.
... Among several factors such as optimized structural design with fewer components, safety measures, high efficiency, fast charging, etc., charging technology stands out as one of the most attractive research topics [6]. These technologies are typically classified into two main categories: wired charging technologies (or contact charging) [7] and wireless charging technologies (or contactless charging) [8,9]. ...
... The Fourier series of the three-pulse rectifier can be derived according to Equation (6). ...
To minimize the recharge time of EVs, Level 3 charging stations utilizing DC fast charging systems have become increasingly prevalent. Additionally, these systems offer bidirectional functionality, aiding in stabilizing the DC grid during peak hour. As a result, the DC–DC converters utilized in such systems must be capable of bidirectional energy transfer. Among existing typologies, DAB converters are preferred due to their simplicity and sustainability. The three-phase DAB (DAB3) is favored because the output ripple is lower compared to the single-phase structure. This characteristic assists in mitigating the negative effects on the battery caused by high-frequency current ripple. However, the input to DAB3 converters typically originates from AC–DC stages, leading to the inclusion of low harmonic frequency ripples (e.g., multiples of 360 Hz). These ripples are then transferred to the battery, increasing its temperature. To address this issue, this paper proposes a technique to mitigate negative effects by attenuating these low frequencies in the charging current. Simulations were conducted to demonstrate the effectiveness of the proposed technique. Scaled-down experiments utilizing a DAB3 prototype were conducted to corroborate the simulations. The findings demonstrated a reduction in ripple from 8.66% to below 2.67% when compared to the original controller. This reduction enabled the solution to meet the limiting current ripple criteria outlined in the CHAdeMO standard.
... Charging units in AC bus-based architectures use separate rectifiers, enabling efficient and independent charging for multiple vehicles [25]. In contrast, systems with a common DC bus provide versatility and high-power operation [26,27]. Hybrid charging architectures, integrating AC and DC technologies alongside micro-grid systems, aim to optimize renewable energy use and enhance micro-grid performance beyond electric vehicle applications [28,29,30]. ...
... To minimize switching losses, soft-switching power electronic switches are being introduced [153,154]. These converters, used in both on-board and off-board chargers, include buck, boost, buckboost, SEPIC, Cuk, Zeta, and Super-lift Luo converters [25,26,27]. ...
The electric vehicle (EV) industry is experiencing rapid growth, accompanied by continuous advancements in charging infrastructure to satisfy the rising need for fast and reliable charging. Particularly, the focus has shifted towards EV fast charging (EVFC) and its impact on the power grid. This paper presents a comprehensive analysis and survey of scholarly literature and projects conducted in this field over the past decade. The findings highlight the rising demand for EVFC and the need to address its potential adverse effects on the power grid. However, there is a noticeable lack of clear research guidance regarding charging time. To tackle these challenges and pave the way for future solutions, extensive research on DC fast charging, ultra-fast charging, and the integration of vehicle-to-grid (V2G) systems is required. This review paper thoroughly investigates the development of fast charging technology for electric vehicles (EVs), including its advantages and comparative analyses from various perspectives. Furthermore, it delves into the advancements in DC fast charging infrastructure, emphasizing charging standards and control modes. The study also investigates different categories of battery chargers for both on-board and off-board charging. Additionally, it explores the classification of DC-DC converters in the context of DC fast charging stations, discusses control strategies for EV systems, identifies existing challenges, and outlines future trends in EV fast charging.
... EV batteries are typically charged using wired or wireless chargers [3]. Owing to their high efficiency, simplicity of use, and lower cost, wired chargers are widely used [3]- [5]. Wired chargers are classified into dedicated onboard chargers (OBCs), integrated OBCs, and offboard chargers. ...
... Wired chargers are classified into dedicated onboard chargers (OBCs), integrated OBCs, and offboard chargers. The dedicated OBCs have an exclusive converter on the vehicle side for charging purposes, whereas integrated OBCs use a traction converter/motor for charging purposes [5], [6]. Conversely, offboard chargers are placed outside the vehicle, which delivers dc power to the battery. ...
The electric vehicle (EV) battery pack voltages typically range from 120 to 450 V; however, the traditional battery charger's operating voltage range is limited. The existing wide voltage range battery chargers employ a front-end diode bridge rectifier followed by a buck-boost derived converter as an ac-dc conversion stage and coupled to an isolated dc-dc converter, resulting in a discontinuous input current and higher power losses due to more semiconductor devices in the conduction path. Furthermore, the utilization of traditional controllers to control these battery chargers produces current transients during mode transitions. This article proposes an isolated bridgeless wide output voltage range battery charger for universal EV charging applications. The proposed charger's operation principles, modeling, and design considerations are discussed in detail. A dual-loop controller for boost and buck operations with a smooth transition logic is designed to accomplish a seamless mode transition. The presented analysis and the design are verified through MATLAB simulations and experimental studies from a 1.3-kW field programmable gate array (FPGA)-controlled silicon carbide laboratory prototype. Finally, the superiority of the proposed charger is demonstrated by comparing it with existing wide-voltage range battery chargers.
... Perovskite solar cells (PSCs), a type of PV device, are one example, and their photovoltaic modules can only be used in specific environmental situations (such as when there is moving fog, shade, bird faces, etc.). A thorough, critical, and in-depth analysis of the popular and recently created global maximum power point tracking (GMPPT) algorithms for photovoltaic (PV) systems is provided in the proposed study [8]. The four main classes of algorithms are (1) optimization algorithms; (2) hybrid techniques of two separate optimization algorithms; (3) hybrid techniques of optimization algorithm with the conventional algorithms; and (4) other GMPPT algorithms. ...
... With an increase in the number of electric vehicles on the road, charging the vehicles will become more difficult if grid electricity is used [8]. The functioning and control of the grid would inevitably degrade when it was used by a large number of electrically powered vehicles. ...
The deployment of renewable energy sources has become more frequent in power system networks over the last few years. The prevalence of global warming and some catastrophic climate changes is rising, along with the demand for intricate transport systems, as a result of rapid growth in civilization and modernization in culture. To fight this environmental issue associated with vehicle transmission, almost every nation is promoting electric vehicles (EV). In this article, a novel method for developing a sliding mode maximum power point tracking (MPPT) controller for photovoltaic (PV) systems operating in rapidly varying atmospheric circumstances is put forward. Further, the standard Perturb and observe (Pb&O) algorithm’s variable step is driven by the best sliding mode controller (SLMC) gains, which are determined using the Genetic Algorithm (GAO). Additionally, a PI controller, a grid employing current controlling topology, and an effective charging station constructed with GAO-optimized Sliding Mode-based reconfigurable step size Pb&O as an MPPT controller are executed and tested in MATLAB/Simulink for optimal control of power in the EV charging station. The main contribution of this study is to enhance the created controller’s tracking performance to reach the maximum power point (MPP) with negligible oscillation, low overshoot, minimum ripple, and excellent speed in conditions of air turbulence that change quickly, as well as ensure continuity in supply to the EV. Furthermore, the developed system as a whole shows good efficacy compared with other existing systems reviewed in the literature. Finally, this proposed strategy ensures continuity of power supply to the charging station even in uncertain weather conditions, as grid integration also plays a vital role in the overall demand.
... This prolonged charging time is among the foremost challenges facing the EV sector. Nevertheless, research shows that DC charging can refuel an EV in 15 minutes [102]. Implementing fast-charging infrastructure can significantly curtail charging durations, making long-distance travel more viable and alleviating concerns linked to EV usage. ...
... Particularly, the kinetic energy generated while slowing down the vehicle via regenerative braking is stored in flywheels to be injected when accelerating the vehicle if required [173]. Practicably, FESS is the best ESD among all other competitors in this application since it has higher efficiency, higher power density, longer lifespan, and smoother and quicker charging and discharging cycle [174,175]. Over and above, flywheels are currently penetrating the rail applications for both hybrid and electrical tractions [176]. ...
In recent years, the operation of the electric power grid has become more efficient and resilient due to the integration of renewable energy sources (RESs). Solar and wind energy are being incorporated aggressively into the main grid, while other RESs like biomass and geothermal energy are also on the rise. However, the intermittent nature of these RESs necessitates the use of energy storage devices (ESDs) as a backup for electricity generation such as batteries, supercapacitors, and flywheel energy storage systems (FESS). This paper provides a thorough review of the standardization, market applications, and grid integration of FESS. It examines the components of FESS, including the electric motor/generator set, power converters, bearings, and control techniques. The paper also highlights the application of modern artificial intelligence (AI) methodologies in optimizing FESS operations, referencing over 240 recent publications in reputable journals. Metaheuristic optimizers, machine learning techniques, and well-matures software's are the main AI aspects discussed in this paper. Additionally, it explores the use of FESS in commercial sectors such as marine, space, and transportation, and its integration with RESs for participating in green energy. Finally, the paper emphasizes the role of AI in enhancing the synergy between FESS and RESs to contribute to a more sustainable and secure energy future.
... Committed to environmental conservation and reducing carbon emissions, Germany views the transition to electric mobility as essential for addressing climate change and promoting cleaner transportation. [28] The government considers EVs crucial for achieving long-term goals of carbon neutrality and sustainable urban growth. ...
The shift towards sustainable transportation has accelerated the deployment of electric vehicles (EVs), demanding advancements in EV charging infrastructure. [1] This thesis, "Shaping the Future: Improvements in EV Charging Infrastructure," explores the critical role of enhancing charging networks to boost EV adoption and usage. It delves into the status, challenges, technological innovations, regulatory frameworks, and evaluates the collective impact on future mobility. In-depth investigations reveal the challenges facing the existing EV charging infrastructure, such as grid capacity limitations, interoperability issues, and regulatory complexities. [2] It also compares global strategies from countries like Germany and India to evaluate the impact of government policies, subsidies, and incentives on infrastructure deployment. The research identifies emerging trends, including wireless charging, bidirectional capabilities, and smart, connected charging stations, emphasizing their potential to revolutionize the EV charging experience. It assesses the economic and environmental sustainability of integrating renewable energy sources into charging networks, as well as the scalability and adaptability of the infrastructure to evolving demands. [3] By synthesizing these findings, the thesis provides insights into future directions for the development of EV charging infrastructure. It offers recommendations for overcoming current barriers, fostering technological innovation, and harmonizing regulations to create a seamless, sustainable, and universally accessible EV charging environment.
... The most typically used renewable sources for charging stations are solar, wind, and biogas energy systems [10]. PV solar systems are more user-friendly and efficient than wind energy systems. ...
Electric vehicle (EV) charging facilities are essential to their development and deployment. These days, autonomous microgrids that use renewable energy resources to energize charging stations for electric vehicles alleviate pressure on the public electricity grid. Nevertheless, controlling and managing such charging stations’ energy is difficult due to the nonlinearity and irregular character of renewable energy sources. The current research recommends using a Brain Emotional Learning Intelligent Control (BELBIC) controller to enhance an autonomous EV charging station’s performance and power management. The charging station uses a battery to store energy and is primarily powered by photovoltaic (PV) solar energy. The principles of BELBIC are dependent on emotional cues and sensory inputs, and they are based on an emotion processing system in the brain. Noise and parameter variations do not affect this kind of controller. In this study, the performance of a conventional proportional–integral (PI) controller and the suggested BELBIC controller is evaluated for variations in solar insolation. The various parts of an EV charging station are simulated and modelled by the MATLAB/Simulink framework. The findings show that, in comparison to the conventional PI controller, the suggested BELBIC controller greatly enhances the transient responsiveness of the EV charging station’s performance. The EV keeps charging while the storage battery perfectly saves and keeps steady variations in PV power, even in the face of any PV insolation disturbances. The suggested system’s simulation results are provided and scrutinized to confirm the concept’s suitability. The findings validate the robustness of the suggested BELBIC control versus parameter variations.
... By 2030, the International Energy Agency expects to sell 30% of all new EVs [3]. When the number of electric vehicles (EVs) increases, the process of charging them with grid electricity will become more intricate [4]. When a lot of electrically driven vehicles were using the grid, it would eventually lose control and functionality. ...
Because of the fluctuating demands for electricity and the growing awareness of the need to protect the environment from global warming and the depletion of nonrenewable natural resources, battery-powered electric vehicles, or EVs, are being used in the transportation sector as an alternative to internal combustion engine vehicles. However, charging these EVs with conventional fossil fuels is neither economically sustainable nor structurally viable. Therefore, this manuscript proposes a renewable energy-powered EV charging station featuring a combination of solar energy, standby battery systems, sophisticated control techniques such as neural network-integrated grids, the enhanced Cuckoo Search Algorithm for Maximum Power Point Tracking, and the Proportional-Integral-Derivative controller. This idea beats current methods and presents a viable way to drive the EV revolution while lessening environmental effects. It maximizes energy management and guarantees a steady power supply even in erratic weather. Grid integration ensures the consistency of power supplies at charging terminals. When compared to other algorithms that have been investigated in the literature, the designed algorithm exhibits excellent performance. Grid integration, in addition to the standby battery, is essential in ensuring that the charging station has a constant power supply, even during unpredictable weather.
... FCS feeds directly from the grid, presenting a large load on the grid. The FCS load may require electric service upgrading [4], [5]. Also, it influences the power quality of the grid. ...
... Carbon dioxide (CO 2 ) emissions have substantial environmental consequences, as they contribute to climate change and global warming. Multilevel converters are increasingly crucial in mitigating CO 2 emissions in sectors such as automotive [1,2] and electrical power [3]. In 2021, transportation and electric power sectors in the United States were responsible for 38% and 33% of energy-related emissions, respectively [4]. ...
Multiple techniques have been suggested to achieve control balance in single-phase three-level neutral-point clamped (3L-NPC) converters. Nevertheless, there is a deficiency of quantitative calculations related to the extent of balancing. Operating beyond the balancing range may result in a sequence of safety incidents. This paper presents a conceptualization of the 3L-NPC converter as two cascaded H-bridges. By employing power conservation principles, the balancing range for the NPC converter is derived, and two novel methods are investigated to broaden the balance range in accordance with the calculated balance range. A comparison is made among the balancing ranges under different balancing control methods. This study establishes a theoretical foundation to ensure the secure and stable operation of the NPC converter.
... In this context, specific microgrids for EV battery charging have been the subject of different studies in the last few years; they have in common the use of a medium voltage network (MV) as a primary energy source to satisfy the huge power demand in both fast and ultrafast charging [3,4]. Moreover, it is generally accepted to include an energy storage system in the electrical architecture of the charging station to support the EVs charging in the moments of peak power demand [5][6][7] and use a hybrid ac/dc microgrid to implement the architecture [8]. ...
This paper presents a two-level hierarchical control method for the power distribution between the hybrid energy storage system (HESS) and the main dc bus of a microgrid for ultrafast charging of electric vehicles (EVs). The HESS is composed of a supercapacitor and a battery and is an essential part to fulfill the charging demand of EVs in a microgrid made up of a 220 VRMS ac bus, two dc buses of 600 V and 1500 V, respectively, and four charging points. A state machine defines the four operating modes of the HESS and establishes the conditions for the corresponding transitions among them, namely, charging the battery and the supercapacitor from the bus, injecting the current from the HESS into the 1500 V dc bus to ensure the power balance in the microgrid, regulating the bus voltage, and establishing the disconnection mode. The primary level of the control system regulates the current and voltage of the battery, supercapacitor, and dc bus, while the secondary level establishes the operating mode of the HESS and provides the appropriate references to the primary level. In the primary level, sliding mode control (SMC) is used in both the battery and supercapacitor in the inner loop of a cascade control that implements the standard constant current–constant voltage (CC-CV) charging protocol. In the same level, linear control is applied in the CV phase of the protocol and for bus voltage regulation or the current injection into the bus. PSIM simulations of the operating modes and their corresponding transitions verify the theoretical predictions.
... Some of the commercially available DC chargers use forced air cooling of the power electronics. For example, EVBox Troniq modular (90 kW-240 kW) [199] and Blink HPC-180-480 (60 kW-360 kW) [200] use forced air cooling of the power electronics while providing optional liquid cooling for the cables. Liquid cooling has higher heat transfer efficiency [201]. ...
The escalating concerns about petroleum resources depletion and ecological issues have accelerated the technological evolution of electric mobility. Electric vehicles (EVs) promise to revolutionize future transportation by reducing fossil fuel dependence, improving air quality, integrating with renewable energies, and enhancing energy efficiency, especially when smart grids have become omnipresent. However, range anxiety and long charging times remain substantial barriers to widespread EV adoption. This review underscores the critical role of fast-charging technology in overcoming these barriers. Fast chargers (FCs) alleviate long charging times by delivering higher charging power in shorter durations, like refueling at gas stations, resulting in promoting consumer interest. Besides, the presence of a fast-charging infrastructure along travel routes is essential to provide quick access to charging points, minimizing range anxiety. The successful FC deployment necessitates careful consideration of appropriate power electronic interfaces to avoid grid issues, including voltage fluctuations, frequency deviations, and power quality disturbances through the implementation of advanced control mechanisms like voltage regulation and power factor correction. Hence, a substantial portion of research efforts has been directed towards the advancement of FCs utilizing silicon carbide (SiC) and gallium nitride (GaN) technologies. This focus highlights breakthroughs in power electronics, facilitating faster charging rates. Besides, adequate cooling is essential for FCs to prevent semiconductor component damage. The review contributes to the thorough examination of pertinent information regarding FCs, encompassing standards, architectures, power converter topologies, compatible battery chemistries, fast-charging techniques, and cooling systems. It also explores the multifaceted impacts of fast-charging on AC-grid and traction batteries, focusing on advanced solutions for grid stability, battery lifespan, and environmental sustainability, including smart grid technologies, battery management systems, and shifting towards renewable energy resources. Finally, the future research trends towards fast-charging are presented. This review provides a unique perspective on the current state of fast-charging infrastructure by synthesizing information from various sources, serving as a valuable one-stop source for researchers interested in this topic.
... Fig. 2(b) illustrates the design of a common DC bus, which offers an approach with greater efficacy for interconnecting multiple EV chargers, RES, and BESS to a single shared bus through DC/DC converters. This design incorporates a centralized DC/DC converter after a low-frequency transformer (LFT), providing several advantages compared to an AC bus design [12] and [13]. ...
... However, this charge comes at a high price. Installing a DCFC will cost between $80,000 and $120,000 (investment, infrastructure, operations, and maintenance) [58,59]. It calls for a sophisticated safety system in case of malfunction. ...
Ensuring reliable and easily accessible charging infrastructure becomes crucial as more people adopt electric vehicles. This study introduces a recommendation system designed to assist electric vehicle users in finding convenient charging stations, enhancing the charging experience, and reducing range anxiety. The system employs advanced data analysis techniques to offer personalized suggestions based on users' preferences. Real-time data on factors like charging station availability, individual preferences, and past usage patterns are collected and processed using a restricted Boltzmann machine-learning algorithm. The waterwheel plant algorithm, known for its effectiveness in solving complex optimization problems, is utilized to optimize the parameters of the restricted Boltzmann machine. The recommendation system considers various user preferences, including charging speed, cost, network compatibility, amenities, and proximity to the user's current location. The system aims to minimize user frustration, improve charging performance, and enhance customer satisfaction by addressing these aspects. Results indicate the system's efficiency in suggesting convenient charging locations. The study explores the statistical significance of the optimized waterwheel plant algorithm and restricted Boltzmann machine model through Wilcoxon rank-sum and Analysis of Variance tests.
Global expansion of the EV market has led to widespread DC charging infrastructure. Consumers prefer DC charging over AC to reduce charging time per kilometer. However, grid-connected DC chargers can cause issues such as grid instability, power quality problems, demand imbalance, and conversion losses. This paper proposes an off-grid photovoltaic (PV) fed DC charger for EVs along with a battery energy storage system (BESS) to mitigate these challenges. The work aims to increase the use of clean energy for EV charging, to ensure uninterrupted EV charging with minimum power conversion stages, and to improve PV utilization. BESS serves as a backup power source that charges or discharges based on PV availability. Additionally, the system powers the non-critical adjustable loads of domestic/industrial sites with the available PV power when both EV and BESS are fully charged. The system can be reconfigured to operate in six distinct modes using two DC-DC converters and five relays. Among six modes, four modes operate in single-stage power conversion. A buck converter is used to extract power from PV. A
bidirectional buck-boost converter is used to charge and discharge the BESS. The proposed system is validated through hardware prototype for both steady-state and transient conditions.
A direct consequence of the rapid expansion of civilization and modernization trends is the escalation in global warming and the consequential climatic upheavals. The world has actively advocated the adoption of electric vehicles (EVs) as a response to the environmental challenges posed by vehicular emissions. It is evident that conventional fuel‐based charging infrastructures are economically impractical and lack organizational cohesion in light of the proliferation of EVs. An EV charging station powered by renewable energy presents a promising opportunity for enhancing flexibility and control. It is imperative that EV charging stations be equipped with solar power and standby batteries (SBBs). Consequently, this article presents and evaluates a system that utilizes a proportional‐integral‐derivative controller, a neural network‐equipped grid and a charging station utilizing a Dragon Fly Optimization Algorithm to generate power and a maximum power point tracking controller. To achieve optimal power management within the charging station, MATLAB/Simulink is used to implement and rigorously test the proposed system. It orchestrates the interaction between the solar panel, backup battery, grid and EVs. Compared to existing systems in the literature, the comprehensive system exhibits commendable efficiency. Due to the pivotal role played by grid integration and the SBB, the system can ensure a reliable power supply to the charging station under any weather conditions.
The increased demand in transportation for plug-in electric vehicles (PEV) made the expansion of charging stations mandatory to keep up with this developing technology. The main drawback of plug-in electric vehicles (PEV) is the long charging time of the battery. The design of The DC fast-charging station (DCFCS) of electric vehicles overcomes this problem. In this proposed work different technology gaps in electric vehicle charging stations have been discussed. The control algorithms have been implemented for controlling the switching operation of the power electronic converter mitigating the harmonics in the source current. The different available multi-level power levels for charging electric vehicles are demonstrated. A DC fast charging station is implemented in power system computer-aided design and their electromagnetic transient response in DC (PSCAD)/EMTDC.
The inefficiency of solid-state transformers (SSTs) under medium (or light) loads poses a significant challenge for wide power range applications, which leads to reduced energy utilization, increased electricity costs, and potential reliability issues. To solve this problem, this paper proposes an SST efficiency improvement strategy considering full power range. The SST utilizes a full-bridge modular multilevel converter (MMC) as the front-end and an input-series-output-parallel DC-DC stage as the back-end. By dynamically adjusting the number of back-end DC-DC cells according to the load power, this strategy significantly reduces the fixed loss of SST at medium and light loads. Meanwhile, a variable intermediate DC bus voltage control is introduced by the front-end MMC. It guarantees the smooth adjustment without inrush current and high system efficiency at heavy loads. Based on the loss model of MMC-SST, a 10kV/1MW case validates that the proposed strategy can improve the SST efficiency by 3.3% at light loads while rarely impacting the efficiency at rated loads. Simulations and experiments confirmed the feasibility.
The integration of electric vehicles (EVs) with the grid has garnered significant attention due to its potential to revolutionize the transportation sector. With advancements in technology and increasing concerns about climate change, EVs have emerged as a viable alternative to internal combustion engine vehicles. EVs offer numerous advantages, including reduced greenhouse gas emissions, improved energy efficiency, and decreased dependency on fossil fuels. This chapter delves into various types of charging infrastructure, such as level 1, level 2, DC fast charging, and wireless power charging, which further enhances the convenience and accessibility of EV charging. Additionally, the establishment of charging infrastructure can occur in a variety of locations, ranging from residential areas to public spaces and commercial buildings. Furthermore, the integration of EVs with the grid has also paved the way for novel approaches in voltage regulation, such as the distributive model of predictive control, within vehicle-to-grid (V2G) systems. Overall, the integration of EVs with the grid not only facilitates the transition to a more sustainable transportation system but also unlocks opportunities for technological advancements and innovative solutions to address the challenges associated with EV adoption. This chapter reviews the use of distributed model predictive control (DMPC) for voltage regulation within V2G. All the reviews are from journals, e-books, or conference papers from 2000 to 2023.
Battery Swap (BS) technology represents a promising solution to overcome the main obstacles to a widespread adoption of electric vehicles (EVs) in a urban environment, like the limited range of EVs and the long battery charging time. Furthermore, with respect to traditional charging stations, it offers higher flexibility in dynamically managing the EV electricity demand to prevent the risk of power grid overload. Nevertheless, proper scheduling of the battery charge process is crucial to offer effective e-mobility services, trading off cost, Quality of Service and feasibility constraints. In this paper we consider a renewable powered multi-socket Battery Swapping Station (BSS) and design two algorithms based on Approximate Dynamic Programming (ADP) and Reinforcement Learning (RL) to dynamically adapt the scheduling of the battery charging process to the stochastic nature of the system. Both approaches are proved to be effective in remarkably enhancing the service quality in terms of increased capability to satisfy the customer demand for EV battery charging, at a lower cost with respect to benchmark approaches, with RL outperforming ADP under any budget constraint. In particular, under RL the probability of not satisfying the EV demand can be decreased by up to more than 40% with respect to benchmark approaches, and a significant cost reduction of almost 20% can be achieved, jointly with a greener system operation. Furthermore, our results show that a fine tuning of hyper-parameters is fundamental to properly trade off cost and Quality of Service constraints according to varying business needs. Finally, we analyse how the proposed strategies may affect the battery health due to their impact on battery degradation, hence influencing the BSS management cost.
This work studies the joint electric vehicle (EV) routing and battery charging scheduling problem in a transportation network with multiple battery swapping stations (BSSs) under random EV swapping demands, renewable generation, and electricity prices. The joint scheduling problem is formulated as a decentralized partially observable Markov decision process (Dec-POMDP) with an objective to minimize the expected sum of the battery charging cost and the travel/waiting cost of EV owners. The formulated Dec-POMDP is hard to solve, due the curse of dimensionality and the unknown system dynamics. To tackle the challenges, we propose a new heterogeneous multiagent hypergraph attention actor-critic (HMA-HGAAC) framework, which integrates hypergraph attention (HGAT) networks to multiagent deep reinforcement learning (MADRL) to enhance the learning efficiency with a hypergraph where multiple nodes can be connected by a single hyperedge. Numerical experiments based on real-world data and a 180-node transportation network show that the proposed approach can save the system cost achieved by state-of-the-art benchmarks, independent proximal policy optimization (IPPO), multiagent proximal policy optimization (MAPPO), and heterogeneous multiagent graph attention proximal policy optimization (HMA-GAPPO), by 23.5%, 18.9%, and 13.3%, respectively.
In this paper, a smart machine-learning-based energy management system (MLBEMS) is developed for a hybrid energy storage system (HESS). This HBESS consists of batteries with high-energy (HE) and high-power (HP) characteristics, to provide grid-supporting services. The aim of the MLBEMS is to improve the overall battery lifetime and achieve state-of-charge (SoC) balancing for two different use cases (UC). UC1 involves enhanced frequency regulation for the Pan-European grid, while UC2 pertains to an electric vehicle (EV) charging station with photovoltaic (PV) generation. The designed MLBEMS is compared with a rule-based energy management system (RBEMS) from the literature with similar use cases. To ensure optimal power sharing between the battery modules, an optimization model is created using real battery aging data. Using a genetic algorithm, optimal power sharing is achieved for various initial SoC conditions. The generated dataset is subsequently utilized to train a machine-learning regression model, and the resulting prediction function is imported into MATLAB/Simulink. In UC1, MLBEMS achieved a 39.3% better SoC balancing compared to RBEMS, along with 36.5% and 22.6% higher battery lifetimes for HE and HP batteries, respectively. Similarly, for UC2, MLBEMS achieved a 68.5% improvement in SoC balancing, along with 53.6% and 45.8% higher battery lifetimes for HE and HP batteries, respectively.
The electrification of transport is expected to progressively replace significant shares of light duty mobility, especially in large cities. The European Alternative Fuel Infrastructure Regulation (AFIR) aims to drive the adoption of electric mobility by establishing specific targets for charging point deployment. Innovative charging concepts may complement and accelerate the uptake of this fundamental part of the urban mobility transition. In this paper, one such innovative concept is described and its potential impact is assessed. The core idea involves integrating charging points into existing city tramway infrastructures. Turin’s tramway network is taken as a representative case study. The proposed technical solution encompasses a charging hub powered by four isolated DC/DC converters of 50 kW, directly connected to the DC tramway distribution line. Three of these constitute the heart of a 150 kW charger, while the fourth acts as voltage regulator. This native DC installation greatly simplifies the architecture of the DC chargers. Using a conservative approach, it was estimated that a single recharging station could charge more than 60 vehicles daily. This highly scalable and replicable solution, with the potential for over 100 conversion substations across Italy, would enable the installation of numerous high-power chargers in urban settings. Furthermore, additional benefits could be realized through enhanced recovery of kinetic energy from trams, which is currently dissipated on-board.
The dual active bridge converter using series-connected SiC
mosfet
s (S-SiC) has attracted considerable interest in medium voltage power conversion. However, under certain operating conditions, S-SiC tends to lose zero voltage switching-
on
(ZVS-
on
), which severely impacts the converter's efficiency and S-SiC's reliability. This article proposes an enhanced phase shift segmentation modulation (EPSS) to achieve ZVS-
on
of S-SiC over a wide range of voltage ratio and transmission power. The foundation of this work lies in the analysis of the soft-switching boundary, which uncovers the auxiliary soft-switching effect linked to the magnetizing current and voltage ratio. This insight facilitates the derivation of an equivalent voltage ratio, simplifying parameter design. Furthermore, phase shift ratio combinations are expanded based on soft-switching boundaries to propose EPSS. A rigorous analysis of operational modes and characteristics reveals that EPSS can achieve a significant reduction in S-SiC loss with limited low voltage (LV) side arm loss incurred. Finally, experiments validate EPSS's effectiveness in achieving soft-switching and enhancing overall efficiency.
This paper focuses on the dc voltage control based on capacitance energy (E
C
) for a flywheel energy storage system (FESS) with the permanent magnet synchronous machine (PMSM) as the energy transformation device. For EC - based PI controller, performance degradation occurs due to the rapid speed change, potential dc-side load step and parameter mismatch. To address this, system properties containing stability, tracking performance and robustness against the aforementioned factors are revealed for E
C
-based dc voltage control methods. It is derived through illustrations of dominant poles and maximal magnitudes with respect to speed, capacitance and coefficients. Moreover, a linear-tracking-differentiator-based energy controller (LTDEC) is presented to achieve fast tracking performance and foregoing robustness of dc voltage. It includes proportional control for direct feedback of E
C
and feedforward of speed and indirectly calculated total consumed power. A selection region for coefficients of LTDEC is designed to enhance stability, tracking performance and robustness. Experiments have verified the effectiveness of the proposed control method and designed coefficient selection region.
Hydrogen has emerged as an important part of the clean energy mix needed to ensure a sustainable future. Falling costs for hydrogen produced with renewable energy, combined with the urgency of cutting greenhouse-gas emissions, has given clean hydrogen unprecedented political and business momentum.
This paper from the International Renewable Energy Agency (IRENA) examines the potential of hydrogen fuel for hard-to-decarbonise energy uses, including energy-intensive industries, trucks, aviation, shipping and heating applications. But the decarbonisation impact depends on how hydrogen is produced. Current and future sourcing options can be divided into grey (fossil fuel-based), blue (fossil fuel-based production with carbon capture, utilisation and storage) and green (renewables-based) hydrogen. Green hydrogen produced through renewable-powered electrolysis is projected to grow rapidly in the coming years.
Among other findings:
Important synergies exist between hydrogen and renewable energy. Hydrogen can boost renewable electricity market growth and broaden the reach of renewable solutions.
Electrolysers can add demand-side flexibility. In advanced European energy markets, electrolysers are growing from megawatt to gigawatt scale.
Blue hydrogen is not inherently carbon free. This type of production requires carbon-dioxide (CO2) monitoring, verification and certification.
Synergies may exist between green and blue hydrogen deployment, given the chance for economies of scale in hydrogen use or logistics.
A hydrogen-based energy transition will not happen overnight. Hydrogen use is likely to catch on for specific target applications. The need for new supply infrastructure could limit hydrogen use to countries adopting this strategy.
Dedicated hydrogen pipelines have existed for decades and could be refurbished along with existing gas pipelines. The implications of replacing gas abruptly or changing mixtures gradually should be further explored.
Trade of energy-intensive commodities produced with hydrogen, including “e-fuels” could spur faster uptake or renewables and bring wider economic benefits.
With the growing fleet of a new generation electric vehicles (EVs), it is essential to develop an adequate high power charging infrastructure that can mimic conventional gasoline fuel stations. Therefore, much research attention must be focused on the development of off-board DC fast chargers which can quickly replenish the charge in an EV battery. However, use of the service transformer in the existing fast charging architecture adds to the system cost, size and complicates the installation process while directly connected to medium-voltage (MV) line. With continual improvements in power electronics and magnetics, solid state transformer (SST) technology can be adopted to enhance power density and efficiency of the system. This paper aims to review the current state of the art architectures and challenges of fast charging infrastructure using SST technology while directly connected to the MV line. Finally, this paper discusses technical considerations, challenges and introduces future research possibilities.
Abstract Recent works have highlighted the growth of battery energy storage system (BESS) in the electrical system. In the scenario of high penetration level of renewable energy in the distributed generation, BESS plays a key role in the effort to combine a sustainable power supply with a reliable dispatched load. Several power converter topologies can be employed to connect BESS to the grid. There is no defined and standardized solution, especially for medium voltage applications. This work aims to carry out a literature review on the main converter topologies used in BESS and highlight the main advantages and disadvantages of each one. The topologies used for each conversion stage are presented and their combinations are analyzed. In addition, the different services that BESS can carry out when connected to the distribution system are analyzed in order to demonstrate all the main contributions to the electrical systems. Finally, a case study is performed to compare and analyze the converter topologies for BESS, considering some aspects such as efficiency, power quality and number of components.
The number of used batteries are increasing in quantity as time passes by, and this amount is to expand drastically as electric vehicles are getting increasingly popular. Proper disposal of the spent batteries has always been a concern, but it has also been discovered that these batteries often retain enough energy perfectly suited for other uses – which can extend the batteries’ operational lifetime into a second one. Such use of batteries has been termed as the “second-life”, and it is high time to adopt such usage in large scale to properly exploit the energy and economics that went into battery production, and reduce the environmental impacts of battery waste ending up in landfills. This paper aids in that quest by providing a complete picture of the current state of the second-life battery (SLB) technology by reviewing all the prominent work done in this field previously. The second-life background, manufacturing process of energy storage systems using SLBs, applications and impacts of this technology, required business strategies and policies, and current barriers of this technology along with potential solutions are discussed in detail in this work to act as a major stepping stone for future research in this ever-expanding field.
This article reviews the design and evaluation of different DC-DC converter topologies for Battery Electric Vehicles (BEVs) and Plug-in Hybrid Electric Vehicles (PHEVs). The design and evaluation of these converter topologies are presented, analyzed and compared in terms of output power, component count, switching frequency, electromagnetic interference (EMI), losses, effectiveness, reliability and cost. This paper also evaluates the architecture, merits and demerits of converter topologies (AC-DC and DC-DC) for Fast Charging Stations (FCHARs). On the basis of this analysis, it has found that the Multidevice Interleaved DC-DC Bidirectional Converter (MDIBC) is the most suitable topology for high-power BEVs and PHEVs (> 10kW), thanks to its low input current ripples, low output voltage ripples, low electromagnetic interference, bidirectionality, high efficiency and high reliability. In contrast, for low-power electric vehicles (<10 kW), it is tough to recommend a single candidate that is the best in all possible aspects. However, the Sinusoidal Amplitude Converter, the Z-Source DC-DC converter and the boost DC-DC converter with resonant circuit are more suitable for low-power BEVs and PHEVs because of their soft switching, noise-free operation, low switching loss and high efficiency. Finally, this paper explores the opportunity of using wide band gap semiconductors (WBGSs) in DC-DC converters for BEVs, PHEVs and converters for FCHARs. Specifically, the future roadmap of research for WBGSs, modeling of emerging topologies and design techniques of the control system for BEV and PHEV powertrains are also presented in detail, which will certainly help researchers and solution engineers of automotive industries to select the suitable converter topology to achieve the growth of projected power density.
DC microgrids have attracted significant attention over the last decade in both academia and industry. DC microgrids have demonstrated superiority over AC microgrids with respect to reliability, efficiency, control simplicity, integration of renewable energy sources, and connection of dc loads. Despite these numerous advantages, designing and implementing an appropriate protection system for dc microgrids remains a significant challenge. The challenge stems from the rapid rise of dc fault current which must be extinguished in the absence of naturally occurring zero crossings, potentially leading to sustained arcs. In this paper, the challenges of DC microgrid protection are investigated from various aspects including, dc fault current characteristics, ground systems, fault detection methods, protective devices, and fault location methods. In each part, a comprehensive review has been carried out. Finally, future trends in the protection of DC microgrids are briefly discussed.
Road transportation is heading towards electrification using Li-ion batteries to power electric vehicles offering eight or ten years' warrant. After that, batteries are considered inappropriate for traction services but they still have 80% of its original capacity. On the other hand, energy storage devices will have an important role in the electricity market. Being Li-ion batteries still too expensive to provide such services with economic profit, the idea to reuse affordable electric vehicle batteries for a 2nd life originated the Sunbatt project, connecting the automotive and electricity sectors. The battery reuse is, by itself, a path towards sustainability, but the cleanliness of energy storage also depends on the electricity generation power sources and the battery ageing or lifespan. This paper analyses the rest of useful life of 2nd life batteries on four different stationary applications, which are: Support to fast electric vehicle charges, self-consumption, area regulation and transmission deferral. To do so, it takes advantage of an equivalent electric battery-ageing model that simulates the battery capacity fade through its use. This model runs on Matlab and includes several ageing mechanisms, such as calendar ageing, C-rate, Depth-of-Discharge, temperature and voltage. Results show that 2nd life battery lifespan clearly depends on its use, going from about 30 years in fast electric vehicle charge support applications to around 6 years in area regulation grid services. Additionally, this study analyses the day-to-day emissions from electricity generation in Spain, and states that grid oriented energy storage applications will hardly offer environmental benefits in the nearby future. On the other hand, applications that go by the hand of renewable power sources, such as self-consumption applications, are much more appropriate.
One of the key parameters to properly and accurately assess an energy storage system is the energy efficiency, which has a direct impact in the system performance and an indirect impact in its cost. In this paper, a methodology for comparing Double-Layer Capacitors (EDLC) and Kinetic Energy Storage Systems (KESS) in terms of energy efficiency is proposed. This methodology, based in accurate loss models, takes real operating cycles into account, so a realistic result is obtained for each particular case. An accurate study of the losses of both technologies is accomplished during the paper, getting a complete model for EDLCs and KESSs, and obtaining Efficiency Maps for the whole range of operation points. Some conclusions about the convenience to use one or the other alternative and the best way to operate them are presented. In addition, a specific study case related to a wave energy power generation plant has been carried out in the paper, defining a methodology to select the energy storage requirements, calculating the round-trip efficiency and getting some recommendations related to the most appropriate operation strategy to take the most advantage of the energy storage system.
This report addresses the fundamental question of how much plug-in electric vehicle (PEV) charging
infrastructure—also known as electric vehicle supply equipment (EVSE)—is needed in the United States to
support both plug-in hybrid electric vehicles (PHEVs) and battery electric vehicles (BEVs). It complements
ongoing EVSE initiatives by providing a comprehensive analysis of national PEV charging infrastructure
requirements. The result is a quantitative estimate for a U.S. network of non-residential (public and workplace) EVSE that would be needed to support broader PEV adoption. The analysis provides guidance to public and private stakeholders who are seeking to provide nationwide charging coverage, improve the EVSE business case by maximizing station utilization, and promote effective use of private/public infrastructure investments.
The analysis is organized around the non-residential EVSE network required to meet consumer coverage expectations and to satisfy consumer demand in high-PEV-adoption scenarios. Coverage and charging demand estimates needed to serve growing PEV markets are made for the communities where people live and the highway corridors on which they travel (Figure ES-1) , including four specific geographic areas:
• Cities (486 Census Urban Areas, population greater than 50,000, 71% of U.S. population)
• Towns (3,087 Census Urban Clusters, population 2,500 to 50,000, 10% of U.S. population)
• Rural Areas (regions not covered by Census Urban Areas/Clusters, 19% of U.S. population)
• Interstate Highway System Corridors (28,530 miles of highway).
In recent years, the use of electrolyzers to produce cleanly and efficiently hydrogen from renewable energy sources (i.e. wind turbines, photovoltaic) has taken advantage of a growing interest from researchers and industrial. Similarly to fuel cells, DC/DC converters are needed to interface the DC bus with the electrolyzer. Usually, electrolyzers require a low DC voltage to produce hydrogen from water. For this reason, a DC/DC buck converter is generally used for this purpose. However, other DC/DC converter topologies can be used depending on the feature of the electrolyzer and electrical grid as well. The main purpose of this paper is to present the current state-of-the-art of DC/DC converter topologies which can be combined with electrolyzers. The different DC/DC converter topologies are compared in terms of output current ripple reduction, conversion ratio, energy efficiency, and power switch fault-tolerance. Besides, remarks on the state-of-the-art and remaining key issues regarding DC/DC converters are provided.
Increasing variability and uncertainty coming from both sides of the power system equilibrium equation, such as wind energy on the generation side and increasing share of new consumers such as electric vehicles on the demand side, entail higher reserve requirements. While traditional approaches of assigning conventional generation units to maintain system stability can increase operational costs, greenhouse gas emissions, or give signals for new investments, utilizing intelligent control of distributed sources might mitigate those negative effects. This can be achieved by controllable charging of domestic electric vehicles. On the other hand, increasing number of public charging stations gives final users the opportunity to fast charge, making their vehicles an additional source of uncertainty rather than a provider of flexibility. This paper brings a full system assessment of combined effect of slow home charging of electric vehicles together with fast charging stations (both with and without integrated energy storage systems), cast as mixed integer linear programming unit commitment model. The contributions of this paper look into optimal periods when fast charging is beneficial for the system operation, as well as assess the benefits of integrating battery storage into fast charging stations to mitigate the negative effects to power system operation.
This paper gives an overview of prices for components of both conventional and electric vehicles, including energy storage, drivetrain as well as interior and exterior vehicle body components. In particular, prices for electric vehicle traction battery packs are analysed, which are estimated to drop remarkably until 2030. In addition, fuel and electricity prices with projections until 2030 are given for important automotive markets. Furthermore passenger cars and commercial vehicles are taken into account. The calculation assumptions for a TCO calculation in the long haul sector are displayed in a showcase for a diesel semi-trailer tractor unit. All costs are based on data found in various literature sources, including experts' opinions. The purpose is to provide a common data basis as a reference point of discussion which is subject to continuous adjustments and improvement. The data itself can be used in order to perform calculations for passenger vehicles and to produce comparable cost estimations.
Energy storage systems (ESS) provide a means for improving the efficiency of electrical systems when there are imbalances between supply and demand. Additionally, they are a key element for improving the stability and quality of electrical networks. They add flexibility into the electrical system by mitigating the supply intermittency, recently made worse by an increased penetration of renewable generation. One energy storage technology now arousing great interest is the flywheel energy storage systems (FESS), since this technology can offer many advantages as an energy storage solution over the alternatives. Flywheels have attributes of a high cycle life, long operational life, high round-trip efficiency, high power density, low environmental impact, and can store megajoule (MJ) levels of energy with no upper limit when configured in banks. This paper presents a critical review of FESS in regards to its main components and applications, an approach not captured in earlier reviews. Additionally, earlier reviews do not include the most recent literature in this fast-moving field. A description of the flywheel structure and its main components is provided, and different types of electric machines, power electronics converter topologies, and bearing systems for use in flywheel storage systems are discussed. The main applications of FESS are explained and commercially available flywheel prototypes for each application are described. The paper concludes with recommendations for future research.
Battery energy storage system (BESS) is one of the effective technologies to deal with power fluctuation and intermittence resulting from grid integration of large renewable generations. In this paper, the system configuration of a China’s national renewable generation demonstration project combining a large-scale BESS with wind farm and photovoltaic (PV) power station, all coupled to a power transmission system, is introduced, and the key technologies including optimal control and management as well as operational status of this BESS are presented. Additionally, the technical benefits of such a large-scale BESS in dealing with power fluctuation and intermittence issues resulting from grid connection of large-scale renewable generation, and for improvement of operation characteristics of transmission grid, are discussed with relevant case studies.
To solve the problem of the mismatched voltage levels between the dynamic lower voltage of the fuel cell stack and the required constant higher voltage (400V) of the DC link bus of the inverter for fuel cell vehicles, a Boost three-level DC-DC converter with a diode rectification quasi-Z source (BTL-DRqZ) is presented in this paper, based on the conventional flying-capacitor Boost three-level DC-DC converter. The operating principle of a wide range voltage-gain for this topology is discussed according to the effective switching states of the converter and the multi-loop energy communication characteristic of the DRqZ source. The relationship between the quasi-Z source net capacitor voltages, the modulation index and the output voltage, is deduced and then the static and dynamic self-balance principle of the flying-capacitor voltage is presented. Furthermore, a Boost three-level DC-DC converter with a synchronous rectification quasi-Z source (BTL-SRqZ) is additionally proposed to improve the conversion efficiency. Finally, a scale-down 1.2 kW BTL-SRqZ prototype has been created, and the maximum efficiency is improved up to 95.66% by using synchronous rectification. The experimental results validate the feasibility of the proposed topology and the correctness of its operating principles. It is suitable for the fuel cell vehicles.
The increasing penetration of renewable energy sources (RES) poses a major challenge to the operation of the electricity grid owing to the intermittent nature of their power output. The ability of utility-scale battery energy storage systems (BESS) to provide grid support and smooth the output of RES in combination with their decrease in cost has fueled research interest in this technology over the last couple of years. Power electronics (PE) is the key enabling technology for connecting utility-scale BESS to the medium voltage grid. PE ensure energy is delivered while complying with grid codes and dispatch orders. Simultaneously, the PE must regulate the operating point of the batteries, thus for instance preventing overcharge of batteries. This paper presents a comprehensive review of PE topologies for utility BESS that have been proposed either within industry or the academic literature. Moreover, a comparison of the presently most commercially viable topologies is conducted in terms of estimated power conversion efficiency and relative cost.
To accommodate the increasing electric vehicle (EV)
penetration in distribution grid, coordinated EV charging has
been extensively studied in the literature. However, most of the
existing works optimistically consider the EV charging rate as a
continuous variable and implicitly ignore the capacity limitation
in distribution transformers, which both have great impact on
the efficiency and stability of practical grid operation. Towards a
more realistic setting, this paper formulates the EV coordinated
discrete charging problem as two successive binary programs.
The first one is designed to achieve a desired aggregate load
profile (e.g., valley-filling profile) at the distribution grid level
while taking into account the capacity constraints of distribution
transformers. Leveraging the properties of separable convex
function and total unimodularity, the problem is transformed
into an equivalent linear program, which can be solved efficiently
and optimally. The second problem aims to minimize the total
number of on-off switchings of all the EVs’ charging profiles
while preserving the optimality of the former problem. We prove
the second problem is NP-hard and propose a heuristic algorithm
to approximately achieve our target in an iterative manner.
Case studies confirm the validity of our proposed scheduling
methods and indicate our algorithm’s potential for real-time
implementations.
Changes in the electricity business environment, dictated mostly by the increasing integration of renewable energy sources characterised by variable and uncertain generation, create new challenges especially in the liberalised market environment. The role of energy storage systems (ESS) is recognised as a mean to provide additional system security, reliability and flexibility to respond to changes that are still difficult to accurately forecast. However, there are still open questions about benefits these units bring to the generation side, system operators and the consumers. This study provides a comprehensive overview of the current research on ESS allocation (ESS sizing and siting), giving a unique insight into issues and challenges of integrating ESS into distribution networks and thus giving framework guidelines for future ESS research.
With the number of electric vehicles (EVs) on the rise, there is a need for an adequate charging infrastructure to serve these vehicles. The emerging extreme fast charging (XFC) technology has the potential to provide a refueling experience similar to that of gasoline vehicles. In this paper, we review the state-of-the-art EV charging infrastructure, and focus on the XFC technology which will be necessary to support current and future EV refueling needs. We present the design considerations of the XFC stations, and review the typical power electronics converter topologies suitable to deliver XFC. We consider the benefits of using the solid-state transformers (SSTs) in XFC stations to replace the conventional line-frequency transformers and further provide a comprehensive review of medium voltage SST designs for the XFC application.
The recent introduction of affordable long-range electric vehicles (EVs) has the potential to trigger a more widespread adoption of EVs with higher charging needs. Increased EV charging can have a detrimental effect on the distribution grid, especially by causing accelerated aging of transformers. Although many EV smart-charging strategies have been proposed to mitigate this problem, centralized and distributed smart-charging strategies require numerous new infrastructure components, and thus take time and money to implement. This paper proposes the term Vehicle-Directed Smart Charging to describe strategies that individual EVs can use to charge in a more intelligent way and thus lessen grid impact. This work proposes a new Vehicle-Directed Smart Charging concept, Random-In-Window (RIW), which has fixed-rate and variable-rate variants. The RIW strategy allows for random charging start times within a specific time window after the residential peak load has reduced. The RIW strategies are compared to other strategies using the real-world logged driving data from 150 drivers for one week using long-range and short-range EV models. A transformer aging model indicates that the RIW strategies are approximately as good as a fully-controlled centralized smart-charging algorithm at EV penetration rates up to 60% for long-range EVs and 70% for short-range EVs.
The proliferation of hydrogen fueling stations as the critical infrastructure is necessary for the successful materialization of hydrogen-powered vehicles. Such fueling stations could utilize the renewable/inexpensive electricity, that would otherwise be curtailed, to generate and store hydrogen. The stored hydrogen can later be used to serve the transportation sector and straightforwardly yield profit for the operator of the stations. While hydrogen fueling stations are primarily contemplated as suppliers to hydrogen vehicles, this study shows how the storage capacity in each station can be exploited to provide operating reserve to an electricity market. To that end, this paper proposes a new supervisory-based algorithm for optimal scheduling of distributed hydrogen storage stations for (i) energy supply to hydrogen-powered vehicles and (ii) operating reserve provision to an electricity market. As such, the economic feasibility of the investment in such stations would be further intensified due to extra financial settlements for the stations via joint applications.
Recently, microgrids (MGs) have provided different advantages for electrical power systems, but they have created some challenges too. One of the most important challenges is the stability of the MG in islanded operations. To overcome this challenge, energy storage systems (ESSs) can play an effective role. On the other hand, each ESS has distinct characteristics that make them suitable for specific applications in the MG. The suitable cooperation among them can ensure reliable operation of the MG. Moreover, it affects the operation of ESSs and their lifetime. In this paper, cooperation between two types of ESSs (flywheel and battery) is studied. The flywheel ESS, which has high power density, is used during MG transient responses, and the battery ESS responds to long-term load changes. A new control method, based on droop equations, is proposed for each ESS unit. Then, the genetic algorithm is used to obtain the optimal controller coefficients. The simulation results show suitable cooperation between ESS units and stable operation of the MG. Finally, to analyze the proposed method's impact on the stability, a root locus analysis is presented.
Three-phase power factor correction rectifiers are an essential area of power electronics, supplying a direct current load with tens of kW, or more, from the public three-phase mains and achieving sinusoidal input currents. In many applications isolation is required between the mains and the load, for example due to safety reasons or different grounding schemes. This paper describes the modulation, design and realization of a buck-boost-type, unity power factor, isolated matrix-type, dual active bridge, three-phase rectifier (IMDAB3R). It uses a circuit similar to a conventional dual active bridge converter, but employs a direct matrix converter to connect the high frequency transformer's primary winding to the mains. A soft switching modulation scheme is proposed and comprehensively analyzed, deriving closed form solutions and numerical optimization problems to calculate switching times that achieve minimal conduction losses. Based on this analysis, the design of an 8kW, 400V rms three-phase ac to 400V dc prototype is discussed, striving for the highest possible efficiency. Using 900V SiC MOSFETs and a transformer with integrated inductor, a power density of 4 kW/
(66 W/
) is achieved. Measurement results confirm a ultra-high full-power efficiency of 99.0% at nominal operating conditions and 98.7% at 10% lower input voltage.
The use of stationary energy storage at fast electric vehicle charging stations can buffer the energy between the electricity grid and electric vehicles, thereby reducing the maximum required grid connection power and potentially mitigating the need for grid infrastructure upgrade. In this paper, a method is presented that sizes the stationary energy storage based on an acceptable average waiting time of drivers arriving at a fast charging station. The novelty of the paper is the focus on the relationship between size of stationary energy store and user waiting time. This relationship is often ignored, however is critical to obtaining the optimum capacity of stationary energy store. An example charging station location is chosen where there are currently eight chargers capable of 120kW charging and a 500kW grid connection. It is demonstrated that the method can be used at this location to design a charging station with stationary energy storage to support future 400kW charging without upgrading the current grid connection infrastructure. With future charging, using a stationary energy storage with a capacity of 1,000kWh reduces the maximum grid power from 1,800kW to 500kW.
With an increasing awareness of the detrimental effects of the fossil fuel?based transportation sector, which accounts for 14% of human-made greenhousegas emissions globally, individuals, companies, and government entities have made a concerted push to develop solutions to provide modes of transportation that are less carbon intensive. Importantly, several countries, including Norway, India, France, and Britain, have decided to end the sale of internal combustion engine cars in the near future, further accelerating the shift to electric transportation.
As the emerging technology offers more economic and efficient mechanisms for hydrogen production, fuel cell electric vehicles (FCEVs) are expected to be deployed more extensively in the near future. Proliferation of hydrogen fueling stations throughout the transportation network and justifying their economic viability are key factors to the success of the FCEVs. On the other hand, in today’s deregulated market environment, many governments are encouraging private investors to invest in key infrastructures including the hydrogen fueling stations. To that end, this paper presents a new model for optimal scheduling of privately owned hydrogen storage stations to both serve the transport sector and the electricity market operator. The model mainly aims to (i) exploit the lower electricity market prices to reduce the power purchase cost and (ii) contribute to the capacity–based demand response program to further enhance the economic feasibility of the investment. The profitability constraints and dynamic hydrogen pricing mechanisms are incorporated into the optimization process to guarantee the economic feasibility of the investment. Through such constraints, hydrogen sale prices would dynamically change to maintain the system profitable at the lowest possible hydrogen price. Numerical studies reveal that the stacked profit from the two aforementioned sources of profit under the proposed model would lead to a stronger rate of return.
The transition from fossil fuel-based transportation to clean, electric mobility has to be considered one of the crucial steps towards decarbonization. However, along with the strong projected increase of electric vehicles, a number of new challenges arise. Especially the continuously rising charge power in combination with an increasing supply by volatile sources result in high loads on the grid, which may cause instabilities and-in the worst case-even blackouts. Within this paper, the possibility of integrating a flywheel energy storage system (FESS) into a photovoltaic-assisted fast-charging station to stabilize the grid is discussed and compared to competing technologies. By introducing energy storage, even with only a low-voltage distribution grid at hand, high charge-power can be provided while at the same time stabilizing the grid. Superior cycle life of the flywheel energy storage, the ability to feed power back into the grid as well as easy transportability are further advantages of FESS for EV fast charging. Several use-cases ranging from the private home user to public transportation are evaluated based on analytical calculations. Characterization of FESS was performed based on real prototype measurements and field tests.
Widespread use of electric vehicles (EVs) requires investigating impacts of vehicles' charging on power systems. This study focuses on the design of a new DC fast-charging station (DCFCS) for EVs combined with local battery energy storages (BESs). Owing to the BESs, the DCFCS is able to decouple the peak load demand caused by multiple EVs and decrease the installation costs as well as the connection fees. The charging system is equipped with a bidirectional alternating current/direct current (DC) converter, two lithium-ion batteries and a DC/DC converter. The introduction of BES within the DCFCSs is investigated with regard to operational costs of the CSs as well as the ability of a BES to mitigate negative impacts on the power grid during congestion hours. The proposed solution is shown to reduce not only the installation costs, but also the charging time and it facilitates the integration of fast chargers in existing low-voltage grids. A cost-benefit analysis is performed to evaluate the financial feasibility of BES within the DCFCSs by considering the installation costs, grid connection costs and battery life cycle costs.
In this paper, analysis and design of a three phase isolated Cuk based power factor correction (PFC) converter has been proposed. The proposed converter is operated in discontinuous output inductor current mode (DOICM) to achieve PFC at ac input. This avoids the inner current control loop which further eliminates the sensing of current. This makes the system more reliable and robust. The converter requires only one simple voltage control loop for output voltage regulation and all the power switches are driven by the same gate signal which simplifies the gate driver circuit. The detailed operation of the converter and design calculations are presented. And also a small signal model of the converter by using CIECE approach is presented to aid the controller design. The experimental results from a 2-kW laboratory prototype with 208-V line-to-line input voltage, 400-V output voltage are presented to confirm the operation of the proposed converter. An input power factor of 0.999, an input current total harmonic distortion of as low as 4.06% and a high conversion efficiency of 95.1% are achieved from laboratory prototype.
The anticipated usage and power requirements of future fast charging points is critical information for organisations planning the rollout of electric vehicle charging infrastructure. This paper presents two novel methods to assist in such planning, one method to predict the time of day fast charging points will be used and one method to estimate the fast charging power required to satisfy electric vehicle driver requirements. The methods involve taking data from instrumented gasoline vehicles and assuming that all the journeys are instead conducted using full battery electric vehicles. The methods can be applied to any dataset of gasoline vehicle journeys that have key data, namely journey start and end times and distance travelled. The methods are demonstrated using a dataset from the United States. It is predicted that for long distance journeys, when the electric vehicle range is exceeded, fast charging point usage will peak in the evening, with 45% of daily fast charges occurring between the hours of 3pm and 7pm. It is also estimated that to satisfy 80% of long distance journeys a charging rate of 20 miles/minute is required, equating to a charging power of 400kW assuming the electric vehicles achieve a driving efficiency of 3 miles/kWh.
To achieve a successful increase in the plug-in battery electric vehicle (BEV) market, it is anticipated that a significant improvement in battery performance is required to increase the range that BEVs can travel and the rate at which they can be recharged. While the range that BEVs can travel on a single recharge is improving, the recharge rate is still much slower than the refueling rate of conventional internal combustion engine vehicles. To achieve comparable recharge times, we explore the vehicle considerations of charge rates of at least 400 kW. Faster recharge is expected to significantly mitigate the perceived deficiencies for long-distance transportation, to provide alternative charging in densely populated areas where overnight charging at home may not be possible, and to reduce range anxiety for travel within a city when unplanned charging may be required. This substantial increase in charging rate is expected to create technical issues in the design of the battery system and the vehicle's electrical architecture that must be resolved. This work focuses on vehicle system design and total recharge time to meet the goals of implementing improved charge rates and the impacts of these expected increases on system voltage and vehicle components.
In a battery-electric vehicle, the powertrain and different auxiliary components are powered by a high-voltage (HV) battery. Most of today's battery-electric vehicles use battery configurations, resulting in the 150-450-Vdc link voltage range, and this highvoltage configuration is often called the 400-V system. In contrast, in electrified truck and construction vehicles, the maximum dc link voltage can reach 870 V, and this configuration is often called the 800-V system. Currently, there are several high-end electric passenger vehicles under development utilizing the 800-V system. This article discusses the benefits and challenges of using the 800-V system in passenger vehicles. For example, the availability of the automotive qualified components for the 800-V system is limited. Therefore, automotive original-equipment manufacturers must assume additional development effort, time, and cost impact when applying the 800-V system to passenger vehicles.
In China, where air pollution has become a major threat to public health, public awareness of the detrimental effects of air pollution on respiratory health is increasing—particularly in relation to haze days. Air pollutant emission levels in China remain substantially higher than are those in developed countries. Moreover, industry, traffic, and household biomass combustion have become major sources of air pollutant emissions, with substantial spatial and temporal variations. In this Review, we focus on the major constituents of air pollutants and their impacts on chronic respiratory diseases. We highlight targets for interventions and recommendations for pollution reduction through industrial upgrading, vehicle and fuel renovation, improvements in public transportation, lowering of personal exposure, mitigation of the direct effects of air pollution through healthy city development, intervention at population-based level (systematic health education, intensive and individualised intervention, pre-emptive measures, and rehabilitation), and improvement in air quality. The implementation of a national environmental protection policy has become urgent.
The most important impact of power electronics on our society in the last 50 years has been the elimination of the 60-Hz ac power delivery system for consumer electronic products. Central to this achievement is the use of silicon (Si) power devices and pulsewidth modulation (PWM) techniques in delivering regulated ac and dc powers to low-voltage (LV) loads such as light-emitting diodes and computers. These solid-state power electronic converters have provided our society numerous benefits, including high-quality power and substantial energy savings. They also form the core technology for integrating renewable energies such as wind and solar into our power grid. Figure 1 shows a typical power delivery architecture commonly found in computer supplies and data centers. The incoming universal ac grid power is converted by a power factor correction circuit to 400 V dc before it is stepped down to a lower voltage dc intermediate bus, such as 12 V, and then it powers the digital loads at voltages as low as 1 V by a point-of-load converter. Si power metal-oxide-semiconductor field-effective transistor (MOSFET) transistors from 20 V to 700 V are almost exclusively used in this application with switching frequencies from tens of kilohertz to one megahertz. Emerging devices based on gallium nitride (GaN) heterojunction field effect transistors reduce the switching and conduction losses when compared with Si power MOSFETs and are, therefore, poised to compete in these applications, driven by the need for higher energy efficiency and higher power density.
For the conventional PFC rectifiers, the high efficiency cannot be achieved over a wide input range, and the efficiency will be greatly decreased at low-input voltages. In order to overcome the efficiency bottleneck under low-line input, a flexible mode bridgeless boost power factor correction (PFC) rectifier is proposed in this paper. According to the input voltage, the proposed rectifier can be flexibly adapted to the suitable operating mode to obtain the maximum efficiency. Meanwhile, the circuit components can be reused by different operating modes, so the extra cost is low. In the proposed rectifier, a back-to-back bridgeless boost PFC topology is adopted at high-line conditions and a three-level bridgeless boost PFC topology is rebuilt to reduce the switching losses at low-line conditions. Compared with the traditional bridgeless boost PFC rectifier, an extra low-voltage bidirectional switch (usually composed of two switches) is added, so the increased cost is low. In addition, the low common-mode noise can be achieved at both high-and low-line conditions due to the direct connection between the input mains and the output electrolytic capacitor. The detailed principle analysis about the proposed rectifier is presented in this paper. Finally, an experimental prototype is built to verify the feasibility and the effectiveness of the proposed topology.