Charging control strategy and charging principle of DC fast charging

火辣西米秀

Charging control strategy and charging principle of DC fast charging [Copy link]

This article mainly analyzes the working principle of DC charging (fast charging) so that readers can understand the entire process of charging new energy vehicles.

The charging system is divided into two modes: conventional charging (commonly known as slow charging) and fast charging (commonly known as fast charging). Slow charging system: The slow charging system uses AC 220V single-phase civilian electricity, and through rectification and transformation, converts the AC power into high-voltage DC power to power the power battery. The main components of the slow charging system: power supply equipment (cable protection box, charging pile & charging cable, etc.), slow charging interface, in-vehicle high-voltage wiring harness, high-voltage distribution box, on-board charger, power battery, etc. Fast charging system: The fast charging system generally uses industrial 380V three-phase electricity. After power conversion, the high voltage and high current are directly charged to the power battery through the bus.

The main components of the fast charging system: power supply equipment (fast charging pile), fast charging interface, high-voltage wiring harness in the vehicle, high-voltage distribution box, power battery, etc. If we want to charge the vehicle, we need to go through a series of operations to complete it. Below we mainly analyze the charging principle of the fast charging system.

0 1 The process of removing and inserting the gun

Press the mechanical lock button of the charging gun, remove the gun from the charging pile, and then insert it into the DC charging port of the vehicle. (Analyze according to the circuit schematic diagram Figure 1) When the charging gun is placed on the charging pile, the mechanical lock is locked, S is closed, and the voltage at detection point 1 is 6V, as shown in Figure 2; when the mechanical lock of the charging gun is pressed, S is disconnected, and the voltage at detection point 1 is 12V (battery voltage), as shown in Figure 3.

When the charging gun is inserted into the charging dock, S is still disconnected, R1 and R4 form a circuit, and the voltage at monitoring point 1 is 6V, as shown in Figure 4; but when the mechanical lock button is released, R1, R4 and R2 form a circuit, and the voltage at monitoring point 1 is 4V, as shown in Figure 5. At the same time, monitoring point 2 (CC2) also receives a plug-in confirmation voltage, which is an auxiliary confirmation signal; the electronic lock is locked at the same time.

Based on the changes in the above detection point signals, the off-board charger controller receives the completion of the charging gun's operation from unplugging to plugging.

0 2 Charging pile voltage supply to vehicle and charging pile self-test process

After completing the above operations, the off-board charger control system receives the completion signal of the gun insertion. At this time, the control system controls the connection of the low-voltage power supply system for the electric vehicle to ensure smooth charging of the vehicle to prevent the charging operation from being interrupted or failed due to insufficient battery voltage (because the charging process takes a long time, generally 4-6 hours); after supplying low-voltage power to the vehicle, the charging pile performs a self-check on the charging circuit, as shown in Figure 6; and outputs the insulation monitoring voltage, as shown in Figure 7; and the pressure relief process, as shown in Figure 8.

0 3 Self-test process of charging controller

When the detection on the charging side is completed, K1 and K2 are disconnected and the charging controller sends a charging identification matching message.

0 4 The vehicle completes the charging preparation process

When the vehicle receives the charging identification matching message sent by the charging controller, it detects the charging side of the vehicle. At this time, K5 and K6 are closed to monitor the charging circuit. After the monitoring is completed, the vehicle controller sends a charging ready message to the charging controller, as shown in Figure 9.

0 5 The charging controller is ready to charge

At this time, the charging controller receives the message sent by the vehicle controller, closes K1 and K2, and sends a charging ready message at the same time.

0 6Charging process

The charging controller sends a charging status message and outputs a charging current to the vehicle (power battery) at the same time; the vehicle also sends power battery status information at the same time, as shown in Figure 10.

0 7 Abort the charging process (full stop)

When the battery is fully charged or the charging controller stops charging, the charging controller sends a charging stop message and disconnects K1 and K2 at the same time; when the vehicle receives the stop message, it disconnects K5 and K6, as shown in Figure 11.

0 8 Stop phase, energy release process

After the charging terminal and the battery terminal are disconnected, the circuit energy needs to be released, as shown in Figure 12.

09Disconnect the auxiliary power supply and electronic lock

After completing the above operations, the charging controller disconnects the auxiliary power supplies K3 and K4 of the vehicle and releases the electronic lock at the same time. After the above steps, the DC fast charging of the vehicle is completed and the vehicle is replenished with energy.

10 Conclusion

This article mainly describes and analyzes the charging principle of DC fast charging for vehicles, and analyzes the entire charging process step by step and layer by layer.