According to the type of entering the car current, the charging pile can be divided into AC charging pile and DC charging pile. The DC charging pile is a power supply device that is fixedly installed outside the electric vehicle and connected to the AC power grid to provide a high-power DC power supply for the electric vehicle power battery.

Electrical structure and working principle of DC charging pile

The input voltage of the DC charging pile adopts three-phase four-wire 380VAC (±15%), the frequency is 50Hz, and the output adjustable DC power directly charges the power battery of the electric vehicle.

The DC charging pile is powered by three-phase four-wire system, which can provide enough power, and the output voltage and current adjustment range is large (applicable to the voltage requirements of passenger cars and buses), which can achieve fast charging. The DC charging pile is similar to the metering and communication and expansion billing functions of the AC charging pile. The electrical structure diagram is shown in Figure 1 below:

Working principle of DC charging pile: Three-phase 380V AC power enters the three-phase four-wire meter after EMC lightning protection filter module, and the three-phase four-wire meter monitors the actual charging power of the whole charger. Moreover, according to the actual charging current and the magnitude of the charging voltage, the charger often needs to be used in parallel, so the charger is required to have a function of current sharing output, and the charger output directly charges the power battery through the charging gun.

When the DC charging pile is working, the auxiliary power supply supplies power to the control system such as the main control unit, the display module, the protection control unit, the signal acquisition unit, and the card swipe module. In addition, during the charging process of the power battery, the auxiliary power supply supplies power to the BMS system, and the BMS system monitors the state of the power battery in real time.

DC charging pile typical power solution

The following is a typical power supply solution for DC charging piles, which simply draws the application of a charger. In practical applications, the power of more than ten kilowatts output by one charger is not enough. It is often necessary to connect three or so chargers in parallel to meet the requirements of high current output. As shown in Figure 2 below:

Power supply instructions:

In the power supply section, first consider the auxiliary power supply of the BMS under high current charging. In the latest national standard, this power supply is uniformly calibrated to 12V10A power supply, and in the BMS management, the BMS power supply system for passenger cars and buses will be unified. Therefore, it is recommended to select the LI120-10B12 with active PFC function to output 12V to power the BMS system.

For the power supply part of the main control system, the LH40-10B24 is recommended to supply power to the HMI display and relays. Then, the K7812-500R3 and K7805-500R3 are converted to 12V and 5V to supply power to the monitoring security unit and the MCU.

In the communication part, the scheme applies three kinds of communication, CAN communication, 485 communication and 232 communication. CAN communication is connected to the car BMS, off-board charger and main control system; 485 communication is connected to the card module, electric meter, etc.; the serial port of the display usually adopts 232 communication mode. Based on internal point-to-point communication, non-isolated communication methods can sometimes be used.

Power recommendation and description:

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