With the popularity of electric vehicles, EV charging connectors and charging technology has become one of the core elements to promote the development of electric transportation. Among them, the CCS charging standard, as a global charging standard, is widely used inthe fast charging system of electric vehicles in the European and American markets. As Chinese companies gradually enter the European and American markets, the CCS charging standard has gradually attracted the attention of more engineers.
The development history and interface design of the CCS charging standard:
The history of the CCS charging standard can be traced back to 2011. At that time, different charging standards appeared in the electric vehicle markets in Europe, North America and Asia, which brought problems of interoperability and charging convenience to the development of electric vehicles worldwide.
To solve this problem, the European Automobile Manufacturers Association (ACEA) proposed a CCS charging standard proposal, which aims to integrate AC and DC charging into a unified system. The physical interface of the connector is designed as a combined socket with integrated AC and DC interfaces, which is compatible with 3 charging modes: single-phase AC charging, three-phase AC charging and DC charging. It can provide more flexible charging options for electric vehicles. The CCS Combo 1.0 standard was officially released in 2012.
In 2014, CCS Combo 2.0 was released, which is an important upgrade to the previous version, further improving the charging power and supporting faster DC charging. This version of the CCS standard has also been widely adopted in the European and North American markets. Since then, the CCS standard has been iterated twice in 2017 and 2020 (CCS Combo 2.0.1 and CCS Combo 2.0.2), further improving the charging power and improving safety.
For historical reasons, CCS includes two physical plug designs. The left side of the picture above is the CCS Type 2 plug (CCS2 for short), which is mainly used in the European market. The right side is CCS Type 1 (CCS1 for short), which is mainly used in the North American market, including the United States and Canada.
The first letter C in CCS is the first letter of Combined. It is called "combined" because the charging port integrates the AC part (upper part) and the DC part (lower part). Only the upper half of the interface is used during AC charging, and the lower DC interface is used for energy transmission during DC charging, and some pins of the upper plug are used for communication.
It is worth mentioning that, unlike the CAN communication used in national standard DC charging, the communication between electric vehicles (EVs) and charging piles (EVSE) in CCS AC and DC charging is achieved through the Control Pilot (CP) interface. The pins related to charging control are:
CP - Control Pilot:
Transmits PWM signals for AC charging control and modulated signals based on power linecommunication (PLC) for establishing high-level communication in AC or DC charging.
PP - Proximity Pilot:
There is a preset resistor between this pin and PE, which allows the EV to recognize that the charging gun head has been connected and the maximum current carrying capacity of the cable.
PE - Protective Earth:
Used for EV grounding protection, and also as a reference ground for CP and PP.
International standards involved in CCS:
The standards related to charging are large and complex. Due to space limitations, this article will briefly explain several standards closely related to CCS AC and DC charging.
IEC 61851-1
The IEC 61851 series of standards is the earliest international charging system standard developed by the IEC organization, and can be called the cornerstone of charging standards. It has important reference significance for the development of charging system standards in other countries or the development of subsequent charging standards such as DIN70121 or ISO15118.
Among them, IEC61851-1 stipulates the general requirements of the charging system, especially the specifications of AC charging. Including my country's AC charging standard GB/T18487.1-2015, it also draws on the same control guidance method.
In simple terms, AC charging control guidance is to achieve the change of the detection point voltage on the CP line by connecting the charging gun head and controlling the opening and closing of the S2 switch on the vehicle end, so as to realize the identification and switching of the charging state between the vehicle and the pile. In addition, the charging pile informs the vehicle of the maximum current that can be provided by generating PWM signals with different duty cycles.
Since the actual charging strategy during AC charging is implemented by the on-board charger OBC. Therefore, the requirements for information interaction between the vehicle and the pile can be met only by the change of the detection point voltage and duty cycle.
When it comes to DC charging, the demand for information interaction between the car and the charging pile has increased significantly, and simple analog signals can no longer meet the demand. Therefore, IEC 61851-1 defines in mode 4 that high-level communication (HLC) is achieved through the CP line to transmit the DC charging protocol defined in IEC 61851-23.
The high-level digital communication of CCS adopts Power Line Communication (PLC) based on HomePlug GreenPHY as the data link layer protocol. In simple terms, the OFDM modulatedhigh-frequency signal is coupled to the CP signal line through a modem installed on the charging pile or the vehicle CP signal circuit, and demodulated by the modem at the other end.
In this way, a communication rate of up to 10 Mbit/s can be achieved without adding additional communication pins, providing a high-bandwidth information interaction channel for DC charging information interaction and advanced functions such as plug-and-play charging and even vehicle-network interaction.
As mentioned above, the introduction of PLC communication can achieve high-level communication while keeping the physical interface of the AC part of CCS unchanged, and can highly integrate the AC and DC electrical interfaces while maintaining compatibility.
However, the disadvantages are also obvious: first, the modulation and demodulation circuit must be added to the CP pilot circuit, and the HomePlug GreenPHY chip is expensive, which indirectly increases the application cost of CCS;
in addition, because PLC communication is based on high-frequency signals, it places high requirements on the quality of the transmission medium, that is, the charging cable. In our daily assistance to customers in testing, we occasionally encounter situations where the signal attenuation is too large due to cable or plug-in terminal problems,making it impossible to establish a charging handshake.
DIN SPEC 70121
The DIN 70121 standard is a normative standard for digital communication between electric vehicles and DC charging piles issued by the German Institute for Standardization in 2012. As early as 2011, the BMW Group had already released the pure electric concept cars i3 and i8 and announced that they would be listed in 2013.
However, at this time, the ISO/IEC 15118 standard was still being drafted and formulated, and the German automotive industry urgently needed a standard to regulate the market and launch products. Therefore, DIN 70121 was born with the mission of revitalizing the electrification transformation of German automobiles.
It is based on the early unreleased versions of IEC 61851-23 and ISO 15118, and defines the digital communication specifications in the DC charging process. In layman's terms, the DIN 70121 standard stipulates the use of CP signal lines as transmission media, PLC as data links, MAC and TCP/IP as communication modes for the network transmission layer, and standardizes the handshake, interaction process and message content of high-level communications, thus solving the urgent problem of the lack of standards in the DC charging industry at that time.
In 2014, the German Institute for Standardization released DIN 70121:2014 Ed.2, which corrected some problems. In 2018, the consistency test specification DIN 70122:2018 for DIN 70121 was officially released. So far, CCS charging has a relatively complete set of standards and consistency test systems.
Due to the tight release time, DIN 70121 has found many defects or problems that cannot be implemented in actual use. Here we have to mention an organization that is very active in the European charging industry - the Electric Vehicle Charging Interface Initiative (CharIN e.V .).
This organization was initiated by several leading European automobile companies in 2015 and currently has 164 core members and 139 members. The CharIN organization aims to unite theindustry to improve the CCS charging standard.
The most representative of these is the annual test meeting (CharIN Testival): through the test meeting, they organize car companies and charging companies in the industry to conduct interoperability tests and collect the problems encountered in the test, and then publish the application guide (CharIN Implementation Guide for DIN 70121:2014) and consistency test cases (CharIN Test Cases for DIN 70121:2014 Implementation Guide) for the problems in DIN 70121 and DIN 70122.
These two guidance documents, as supplements and amendments to the DIN standard, will also be adopted in future DIN versions. At present, with the continuous growth of the CharIN organization, they are no longer limited to the CCS standard and are looking at global charging standards.
The CharIN organization also defines three stages of CCS charging standards, and DIN 70121 belongs to the Basic stage.
