Some background information on EV charging Standards
Electric Vehicle (EV) Combined Charging System (CCS )
The Combined Charging System Type 2 (CCS2) connector is the ‘standard’ alternating current (AC) connector for charging electric vehicles from one, or optionally two or three phase 230 volt power each at up to 32 amps for cars usually manufactured in Europe. In this way an EV can be connected and charged from a suitably equipped Electric Vehicle Supply Equipment (EVSE) charger albeit considered to be ‘Slow’ AC charging.
It has a ‘Protective Earth’, ‘Negative’, one or more ‘Live’ plus two control connections.
To ensure the current rating of an untethered cable is not exceeded a resistor is connected between its Proximity Signal (PS) pin and the Protective Earth pin within the connectors at each end of the cable. This can be interrogated by the EV and the EVSE thereby ensuring excessive current is not passed through the CCS Type 2 cable.
The other connection is for the Control Pilot (CP) Signal for data transmission bi- directionally between the EV and the EVSE which started out providing pitifully limited low level information using combinations of 1 kHz pulse width modulated signal switching between -12V and several positive up to +12V. The signals indicate for example if the EV is connected or not and various basic control and safety checks and AC current levels. I hope the limited vision of those who evolved the standard are suitably embarrassed.
To address the need for higher level data communication and data speed capability is provided using Power Line Communication (PLC) utilising high frequencies injected on the original line essential for the use when DC charging.
Today, vehicles are mainly charged with alternating current in domestic situations . As a rule, one phase with 230V and max. 16A is available, which corresponds to approx. 3.3kW. A charging process therefore takes several hours. For this type of charging, only a little signalling using a PWM signal is necessary. When charging an electric vehicle with direct current (DC), the alternating current is already converted into a direct current of high voltage, e.g. to 700V, at the charging station. The vehicle battery is thus charged directly with very high currents, so that charging stations with 25kW to 350kW are no longer uncommon. Such high-power charging makes it possible to shorten the charging time to just a few minutes.
In contrast to AC charging, however, DC charging requires determining the battery's charging level, its temperature and its charging capacity and transmitting this information from the vehicle to the charging station. This requires secure and functioning communication between the two.
A Review of Some Charging Standards
Electric vehicles (EVs), such as battery electric vehicles or plug-in hybrid electric vehicles, are expected to take over a major part of the transportation sector. As a result, the demand for Electric Vehicle Supply Equipment (EVSE), also known as Charging Stations, is growing. An EVSE should be able to handle the charging process for different types of EVs. In addition, different EVs might have different charging requirements, in terms of charging power, charging time, AC/DC charging, etc. Therefore, several standards have been created to regulate the EV-EVSE interface and the charging process requirements.
DIN 70121 is one of the first standards that was developed to regulate the EV-EVSE interface. However, it lacked some features such as Transport Layer Security. Later, other standards, such as ISO 15118 and SAE standards were developed based on DIN 70121 to regulate secure charging requirements in an EV-EVSE interface. Whereas SAE standards are more favourable in North America, ISO 15118 is the preferred standard in Europe. Both SAE J2847-2 and ISO 15118-2 have adopted the Power-Line Communication (PLC) physical layer for communications between EV and EVSE, however, there are some differences in the datalink layers of these two protocols.
EVSEs are capable of both DC and AC charging, as shown in Figure 1. In AC charging, the EV must be equipped with an onboard rectifier. The communication between EV and EVSE in AC charging is through a PWM signal over the Control Pilot signal. DC charging, however, has some benefits over AC charging. In DC charging, the onboard rectifier is no longer needed. In addition, much more electric power can be transferred in one DC charging session which reduces the charging session time in comparison with AC charging. However, due to the complexity of a DC charging session and billing requirements, a more advanced communication protocol than PWM communication is needed.
A standard handshaking protocol is required by the Pilot and Proximity signals in the EV-EVSE interface. In addition, digital communication may take place between the EV and EVSE to initiate or terminate the electric energy transfer to the EV. This communication happens over the Control Pilot signal using the PLC protocol outlined in HomePlug Green PHY specifications. Although PLC for AC charging is optional, it is required for DC charging. SAE and ISO 15118 have both adopted the HomePlug Green PHY specification for PLC and have developed several standards to manage the digital communication in an EV-EVSE interface. Dana’s OpenECU M560 and M580 controllers support these standards and are compatible with HomePlug Green PHY specifications. To achieve this goal, the M560 and M580 are equipped with the Qualcomm Powerline Communication (PLC) chipset to support digital communication between the EV and EVSE over the Control Pilot signal. Furthermore, a library of supported Simulink blocks based on SAE J2847-2 and ISO 15118-2 are offered in the OpenECU development toolchain to manage the PLC communication in Simulink environment.
In AC charging, typically the onboard charger controller handles the EVSE interface. However, for DC charging, no onboard charger (rectifier) is required to be installed in the vehicle. Hence, the task of handling the EVSE interface and managing the charging session is assigned to another ECU in the vehicle, such as the supervisory controller.
According to HomePlug Green PHY PEV-EVS, once an EV is connected to the EVSE, an association protocol assigns that EVSE to the EV. This procedure is handled via SLAC Association on Pilot signal as described in Green PHY PEV-EVS and SAE J2931-4 (or ISO 15118). Currently in Europe ISO 15118 is the dominant standard. Once an EVSE is associated with the EV with SLAC protocol, several sequential stages must take place over PLC communication for configuring the charging parameters, and managing the energy flow to the EV:
- Initialization of the charging session
- Isolation monitoring and pre-charge
- Energy transfer
- Shutdown and disconnect
OCPP – Open Charge Point Protocol
The Open Charge Point Protocol (OCPP) is an application protocol for communication between electric vehicle charging stations and a central management system. It is an international, open-source, vendor-independent standard which is available for free.13 Jul 2022
Standardisation of UK Electric Vehicle Charging Protocol ...
https://mdpi-res.com › wevj › wevj-12-00063-v2
PDF
by K Chamberlain · 2021 · Cited by 9 —
Power Line Communication (PLC) is a standard used for communication between EVs and chargers. CCS uses the PLC protocol. All connector types ...
https://mdpi-res.com/d_attachment/wevj/wevj-12-00063/article_deploy/wevj-12-00063-v2.pdf
What is ISO 15118? - Switch EV
https://www.switch-ev.com › blog › what-is-iso-15118
As part of the Combined Charging System (CCS),
ISO 15118 is a communication protocol covering all use cases for charging electric vehicles across the globe.
Home Plug Green PHY The Standard For In-Home Smart Grid Powerline Communications
https://openecu.com/case_study/inte...g-green-phy/homeplug_green_phy_whitepaper.pdf
The IEEE Std 1901-2010 is a standard for high speed communication devices via electric power lines, often called broadband over power lines (BPL). The standard uses transmission frequencies below 100 MHz.
Implementation of HomePlug Green Phy standard (ISO15118 ...
https://ltu.diva-portal.org › get › FULLTEXT01
PDF
The HomePlug
Green PHY standard was developed to allow more advanced communication between
electric vehicles and electric vehicle supply equipment.
https://ltu.diva-portal.org/smash/get/diva2:1546405/FULLTEXT01.pdf
HomePlug Green Phy for Electric Vehicles
