Sharing the basic working principle of electric vehicle charging piles

Sharing the basic working principle of electric vehicle charging piles

The basic configuration of electric vehicle charging piles is power unit, control unit, metering unit, charging interface, power supply interface and human-machine interface, etc., of which the power unit refers to the DC charging module and the control unit refers to the charging pile controller. The DC charging pile itself is a system integration product. In addition to the two major components of "DC charging module" and "charging pile controller" that form the core of the technology, structural design is also one of the keys to the overall reliability design. "Charging pile controller" belongs to the field of embedded software and hardware technology, and "DC charging module" represents the high achievement of power electronics technology in the field of AC/DC. So, let's take a look at the basic working principle of electric vehicle charging piles!

The basic process of charging is to apply DC voltage to both ends of the battery to charge the battery with a certain high current. The battery voltage rises slowly, and when it reaches a certain level, the battery voltage reaches the nominal value and the SoC reaches more than 95% (varies depending on the battery), continuing with constant voltage and small charging current. In order to realize the charging process, the charging pile needs a "DC charging module" to provide DC power; A "charging pile controller" is needed to control the "power-on, power-off, output voltage, and output current" of the charging module; It requires a "touch screen" as a human-machine interface to send instructions such as "power on, shutdown, voltage output, current output" to the charging module through the controller. The simple charging pile learned from the electrical side only needs to have a charging module, control panel and touch screen; With just a few keyboards, you can enter commands such as power on, shutdown, output voltage, output current, etc. on the charging module, and one charging module can charge the battery. Charges.

The electrical part of the EV charging pile consists of the main circuit and the secondary circuit. The main circuit input is three-phase alternating current, which converts three-phase alternating current into DC power received by the battery through the input circuit breaker, AC smart energy meter, and charging module (rectifier module), and connects the fuse and charging gun to charge the electric vehicle. The secondary circuit consists of a charging pile controller, a card reader, a display, a DC meter, etc. The secondary circuit also provides "start-stop" control and "emergency stop" operation; The signal provides "standby", "charge" and "fully charged" status indications, and the display provides kanban, charging mode setting and start-stop control operation as an interactive device.

The electrical principles of electric vehicle charging piles are summarized below.

1. A single charging module is currently only 15kW, which cannot meet the power demand. Multiple charging modules need to work in parallel, and one bus needs to achieve multiple module current sharing;

2. The charging module input comes from the power grid and is a high-power power supply. It is related to the power grid and personal safety, especially when it comes to personal safety. An air switch should be installed at the input end, and the lightning protection switch should be a leakage switch.

3. The output is high voltage and high current, and the battery is an electrochemical substance that is explosive. In order to prevent safety problems caused by misoperation, a fuse needs to be added to the output end;

4. Security is a top priority. In addition to the measures at the input end, mechanical lock and electronic lock, insulation check, discharge resistance;

5. Whether the battery can be charged depends on the battery's brain and BMS, not the charging pile. The BMS sends instructions to the controller "whether to allow charging, whether to pause charging, and how high the voltage current can be charged", and the controller sends it to the charging module.

6. Monitoring and management. The controller background should be connected to WiFi or 3G/4G network communication modules;

7. The electricity bill is not free, you need to install a meter, and the card reader needs to realize the billing function;

8. The shell should have clear indicator lights, generally three indicator lights, indicating charge, fault and power supply respectively;

9. The air duct design of the EV charging pile is key. In addition to the structural knowledge of air duct design, it is also necessary to install a fan in the charging pile, with one fan in each charging module.