First, the charging pile structure
The charging pile mainly consists of charging pile controller, billing unit, charger and other modules, mainly using CAN bus communication. The charging controller communicates with the external BMS, mainly completing the charging process such as charging handshake.
Figure 1 Charging pile internal structure
Second, charging pile industry CAN bus test requirements
1. Protocol consistency
The CAN bus communication between the charger controller and the BMS must meet the "Agreement on Protocol Conformance Between the 34658-2017 Electric Vehicle Off-Board Conductive Charger and the Battery Management System" to verify that the charging function is normal.
If it is not tested by this project, it will cause charging failure when charging the pile, and it will not charge the power or even a greater degree of safety hazard.
Note: The specific requirements are interpreted as shown in the “Interpretation of Charging Pile Standardsâ€.
2, the national network standard physical layer test requirements
The charge controller of the charging post communicates with the BMS using the CAN bus, and must meet the physical layer and link layer test contents specified in the QGDW1591-2014 Electric Vehicle Off-Car Charger Inspection Technical Specification:
l Physical layer test items: transmission rate test, signal amplitude test, bus delay test, bus utilization test, bus error rate test, terminal resistance change test, message stress test, anti-interference test
l Link layer test items: frame format test, protocol data unit test, protocol data unit PDU format test, parameter group number PGN test, transmission protocol function test, address allocation test.
If this part of the functional test is not passed, it will not be able to pass the national network bidding, and signal quality problems at the bottom of the charging pile protocol communication, affecting the subsequent charging process.
Note: The specific requirements are interpreted as shown in the “Interpretation of Charging Pile Standardsâ€.
3. Charging pile and bottom layer debugging of charging reactor
Charging pile operation is a strong electromagnetic interference environment, causing common mode interference to crosstalk to the bus, resulting in communication errors, a large number of error frames, communication failure or the entire charging pile crash can not run. Therefore, it is necessary to pay attention to CAN bus amplitude, waveform, edge, common mode signal and other details to ensure signal stability.
The charging reactor is charged by multiple piles. The overall communication is on the same CAN bus, and attention should be paid to the load rate test.
Figure 2 charging pile test waveform screenshot
Third, CANScope test application program
1, test the connection
The charging pile controller leads the communication line through the gun head, and is connected to the external BMS. The identifier of the communication line of the gun head is S+, S-, and the communication process such as charging handshake is performed by connecting with the BMS. When testing, because the communication line of the gun head is inconvenient to pull out, CANScope is mainly connected to the output of the charging controller, S+ is connected to CAN_H, S- is connected to CAN_L, and the automation protocol conformance test is directly performed on the PC host computer.
DC+ and DC-close are used to detect the battery voltage. When the BMS (CANScope) sends a BCP message during the test:
l If it is a 2011 standard pile, it will automatically skip this stage and the test process will continue to run;
l If it is a 2015 standard pile, when the test flow is to the BCP message, the user needs to manually close the DC+ and DC- inside the pile to enable the charging pile to perform battery voltage detection and make the process run downward.
Note: The protocol conformance test does not need to connect to the BMS and the load. The architecture diagram is only to illustrate the charging stub and external device connection architecture.
Figure 3 CANScope application test connection
2, CANScope application function
1) Fully automatic protocol conformance test, which can export test reports
Users only need to follow the application test connection (load or BMS can not be connected), open the software test page, customize the necessary test items, click to start the test and complete the entire automated test process, and provide test reports.
Especially after the charging pile is installed, if there is communication problem at the scene, the charging pile test system is not portable, and CANScope can easily carry the business trip to the scene to solve the problem caused by the charging protocol error.
Figure 4 Protocol Conformance Test Page
2) State Grid standard physical layer test is better to supplement
Users only need to test the connection according to the application (load or BMS can not be connected), open the device and run the charging pile, collect the message and waveform of the charging process, and test the physical layer test test item by item, covering the national network standard in the physical layer test. Requirements. The charging pile test system generally only focuses on application layer protocol testing, so CANScope is the best complement to the underlying test, which is the current CAN bus test.
Note: For the detailed function of the underlying test, please open the ZLG Zhiyuan electronic CANScope test software for browsing.
5 Physical Layer test
3) Underlying test
CANScope is the main underlying test. It is the only CAN bus test and analysis device for waveform and message synchronization on the market. It can solve the problem of CAN bus communication error when user charging pile development, directly locate the wrong node and find out the cause of the error. Accelerate the development process.
Figure 6 CANScope underlying test plugin
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