Models and boundaries of data exchange between electric-vehicle and charging-point. Example of a practical realisation

Abstract

In this paper the communication structure for V2G (vehicle-to-grid) technology is introduced. Further, a technical solution is shown for the communication path between EV (electric vehicle) and charging point based on the power plug standard IEC 62196-2. For efficient data exchange a communication protocol is proposed. In a laboratory setup the functionality of an electronic unit, protocol and software application is demonstrated and a functional solution of the data exchange system is created. Finally some recommendations for the future works have been pointed out.

Full text

Models and boundaries of data exchange between
electric-vehicle and charging-point.
Example of a practical realisation.
C. Wenge, P. Komarnicki
Process and Plant Engineering
Fraunhofer Institute for Factory Operation and Automation
Magdeburg, Germany
christoph.wenge@iff.fraunhofer.de,
komarn@iff.fraunhofer.de
Zbigniew A. Styczynski
Chair of Electric Power Networks and Renewable Energy
Sources
Otto-von-Guericke-University Magdeburg
Magdeburg, Germany
sty@ovgu.de
Abstract— In this paper the communication structure for V2G
(vehicle-to-grid) technology is introduced. Further, a technical
solution is shown for the communication path between EV
(electric vehicle) and charging point based on the power plug
standard IEC 62196-2. For efficient data exchange a
communication protocol is proposed. In a laboratory setup the
functionality of an electronic unit, protocol and software
application is demonstrated and a functional solution of the
data exchange system is created. Finally some
recommendations for the future works have been pointed out.
Keywords— vehicle-to-grid; CAN protocol, charging point
connection, EV data exchange, power plug standart, ICT –
information communication technology
I. INTRODUCTION
Electric mobility is a current topic accelerated by the
need for an alternative means of transportation. The
proportion of renewable energy generation is increasing and,
as a result, is causing the necessity of energy regulation. To
keep the constant balance between the generation and power
load in networks with a high ratio of energy from renewable
sources, there is the need for energy storage. This makes
electric vehicles (EVs) interesting as one of the potential
storage capacities for the power grid and, in particular, as
mobile electric energy storages. To make the electric
mobility realistic and the integration of the EVs into the grid
efficient an infrastructure of charging points and a
communication network is needed. Further, the EV has to be
“electrically” connected to the grid and a communication has
to be available to control the charging process. Benefits of
controlled charging methods are the possibility to allocate
the power consumption to off-peak periods in the grid or to
affect the charging process with renewable power generation.
To use the electric vehicle fleet as electric energy storage the
local amount of vehicles connected and their status has to be
known to identify the available electric capacity. Also a
mobility forecast is necessary because of the fluctuation of
the available capacity caused by leaving and arriving
vehicles that are currently connected or disconnected.
II. COMMUNICATION STRUCTURE IN THE FIELD OF
ELECTRIC MOBILITY
A. General remarks
The electrification of vehicles has created a couple of
challenges in different research areas, which require
reasonable and applicable solutions. In addition to the
research in vehicle construction, like traction batteries and
power electronics, communication plays an important role
and more research is needed in the fields of EV navigation to
selected charging points, the monitoring of the EV energy
need and the EV charging control. Furthermore, the
integration of EV as mobile energy storages into the
electrical grid requires a communication structure and
standardized communication protocols.
The communication structure “Fig. 1” consists of the
following communication participants: the mobility area
control room, the charging point, the EV and the user of EV.
Figure 1. Communication structure in electric mobility
The tasks of the mobility area control room are
monitoring of the energy need caused by the stationary EV
and the forecast of leaving and entering EVs in the balance
area. Also included in the services are the navigation of EV
to available charging points and control of the energy
consumption of the charging EV fleet. All of the relevant
data of the EV fleet are transferred together in the mobility

area control room, where they are stored in a database. From
here the data are available to the charging point and the
human machine interfaces (HMI) like mobile phones,
navigation systems or internet portals. This enables the
functions of monitoring, coordinated management of the
energy demand of the EV fleet and services for the EV user.
To implement the EV into the communication system
they have to work with a compatible communication
protocol and the necessary parameters have to be available.
B. Communication in electric vehicles
The necessary parameters of an EV belong to different
units which have various interfaces. A structure like in “Fig.
2” can be assumed.
The battery management system dispenses the steady and
dynamic parameters of the battery which are necessary for
range forecast. The communication to the charger is needed
to influence the charging process. Thereby, it is possible to
affect the power flow dimension and direction while the car
is connected.
Figure 2. Example of parameter sources in an electric vehicle
Because of the lack of standards and communication
compatibility a communication unit is used to handle the
different interfaces and to convert the parameters into a
uniform protocol. As shown in “Fig. 1” the EV
communicates with the mobility area control room. This can
be realised in general through wireless or wired
communication. For vehicles on the go wireless
communication standards like GPRS (General Packet Radio
Service) and UMTS (Universal Mobile Telecommunications
System) are feasible. For the vehicles connected to the
charging point a wireless or wired data exchange is possible.
While the vehicle is driving data about available charging
points nearby or the vehicle status are exchanged through a
telecommunication unit.
The vehicle user is able to interact through various HMIs
(human machine interfaces). This is realised by a software
application, which can be installed on various devices like
mobile and smart phones, the navigation tool in the car or the
terminal at the charging point.
C. Communication between electric vehicle and charging
point
The electric vehicle can presently be connected with
various power plugs. Usually a common ~230V connector is
used. There is not a standardisation for electric vehicles yet.
The future standard power plug for EV (IEC 62196-2) “Fig.
3” is a three-phase plug with two signal pins.
Figure 3. Example of a power plug for an electric vehicle (IEC 62196-2)
One pin is for communication, and through a resistor on
the second pin the maximum current of the cable fittings is
coded. The plug is thereby compatible for both single-phase
and three-phase current. Alternative means of data transfer
are to modulate a signal on one of the three phases, as with
power line communication (PLC), or to use wireless
communication techniques.
D. Data exchange of electric vehicles
The bidirectional data exchange from and to an electric
vehicle is necessary to realise the integration of EV into the
grid. This enables the controlled and back-looped controlled
charging. The connected vehicle receives data from the
charging point and the charging point receives data from the
vehicle “Fig. 4”.
Figure 4. Example of parameter exchange of an electric vehicle connected
to a charging point
The data exchange includes technical parameters about
the specification of the charging point and EV. Besides the

steady parameters (charger-/ battery characteristics, etc.)
variable parameters such as SOC (state of charge), SOH
(state of health), maximum charging current, etc. are
communicated.
The EV user enters, for example, the time s/he is going to
be connected to the charging station and the minimum range
of distance that needs to be available after the charging
process. The data are transferred to the charging point and,
based on this data and the data given from the mobility area
control room, a charging driving plan is negotiated with the
vehicle. The power transfer depends on the limits of the
battery, charger, charging point and the connection time. The
resulting scope enables the space for controlled charging and
grid services.
The simplest operation for influencing the charging
process is to interrupt or start the charging procedure. More
complex methods could be a capacity limitation for the
charging process or bidirectional energy flow for grid
support services. With increasing control of the charging
process and service done for the vehicle, the complexity of
the control and communication structure also accelerates and
the amount of data that have to be exchanged increases.
III. REALISATION OF COMMUNICATION
A. Introduction
For a solution to a communication system between an EV
and a charging point a hardware apparatus in the form of an
electronic device and a protocol that fulfils the requirements
were designed. To realise the communication, the
communication pin of the power plug is used with a CAN
(controller area network) bus as wired communication. The
benefits are the simple realisation, connection stability and
presence in the automobile sector.
B. Protocol for EV communication
The communication protocol was construed considering
the CAN bus specification. The structure of a CAN2.0A
message has an identifier of 11bit (CAN2.0B 29bit) length
and a data package of maximum 64bit.
TABLE I. CAN DATA FRAME (CAN 2.0A)
1 (29) 11+1 6 0… 64 15+1 2 7 3…bit
arbitration control data CRC ACK EOF
bus
idle
SOF
Identifier
RTR
IDE, R1, DLC
0 to 8bytes
CRC
CRC delimiter
ACK-Slot
ACK-delimiter
End-Of-Frame
Inter-frame-
space
With the 11bit identifier a protocol structure was defined,
see “Fig. 5”. The first three bits are used to identify the
source of the message, the following 4 bits define the
component group and the last four bits the exact parameter.
In “Fig. 5” a hexadecimal view of the ID was chosen to
show the categorization.
Figure 5. Structure of the communication protocol considered on the
CAN bus
In “Table II” an example is shown for the parameter
SOC, which is also marked in “Fig. 5”.
TABLE II. PARAMETER DISCRIBED IN PROTOCOL
Example of a pa
r
ameter fro
m
the
p
rotoco
l
CAN-ID
in dec
Para-
meter
S
p
ecificatio
n
Unit Facto
r
Format
8 byte
565 SOC state of charge
(EV - BMS
SOC)
[%] 10-
2
HEX
Example
CAN-ID
in hex
DATA
in hex
DATA
in dec
DATA
in dec *
factor
End
V
alue
with Unit
235 26AC 9900 99,00 99,00 %
In the protocol all parameters of the communication
participants are described and have a unique ID. Also, the
protocol gives enough space for future parameters that can be
implemented in the structure. The protocol itself is
independent of the communication technologies. The
message includes the identifier and the data package. The
identifier includes the information to interpret the data
package.
C. Test construction for EV communication
Test communication lines were built to construct the
communication unit with the implemented protocol. The
sketch of the test setup can be seen in “Fig. 5”. The
communication path is a battery with a monitoring electronic
unit, two communication units which represent the EV and
the charging point, and two computers that are each
connected to one of the communication units.

Figure 6. Structure of the communication protocol considered on the
CAN bus
Components in “Fig. 5”and “Fig. 6”are:
• (1) PC 1 with terminal software to display the
received data
• (2) PC 2 with software application for user
interaction
• (3) battery with integrated monitoring electronic
unit
• (4) designed electronic unit with an 8bit micro
controller and various interfaces to read data
from battery monitoring electronic unit,
convert data in protocol and transmit through
CAN bus through EV power plug
• (5) second electronic unit with 8bit micro
controller to receive data and communicate
with PC 2 via software
• (6)-(7) communication path through cable fittings of
standard IEC-62196-2
Figure 7. Structure of the communication protocol considered on the
CAN bus
The communication unit (4) reads the data from the
battery management system and the implemented software in
the microcontroller converts the values into the protocol. The
communication unit sends the data to PC 1 (1) and via CAN
bus through the EV power cable (6) to (7) to the second
communication board. PC 2 has a user application installed
that works with the transferred values.
The communication unit has to be configured once for
the specification of the EV. Once installed the unit converts
the needed parameters and provides them for further tasks or
communication.
IV. CONCLUSIONS
There is no standard defined for the communication
between electric mobility participants. This paper presents
one of the possible solutions for data exchange between the
electric vehicle and charging point based on existing
communication technologies. The example realization of the
connection structure as well as the implementation of
information flow between the units is proposed. In the
context of V2G (vehicle to grid) the communication among
the participants is necessary and can be realised by an extra
device that would convert the needed values into a
communication protocol. During the development of the
system the main task of EV which is essentially to ensure
mobility of the users can not be forgotten.
The presented solution for a physical connection and
protocol proposal for data exchange between electric vehicle
and charging point was realized in the laboratory
environment. A prototype of the realization in the field,
installation of the devices in an available electric car and
charging point, as well as tests and analyses are planned.
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