High voltage interlocking - one of the high voltage safety technologies for electric vehicles

火辣西米秀

High voltage interlocking - one of the high voltage safety technologies for electric vehicles [Copy link]

What kind of role does the high-voltage interlock of new energy vehicles play? It is mainly for safety. It can prevent short circuit and leakage risks when the high-voltage connector falls off and avoid arcing when plugging and unplugging the high-voltage connector. Today, let's learn about the high-voltage interlock of new energy vehicles with the editor.

1. What is high voltage interlock

High-voltage interlocking refers to the use of low-voltage signals to check the connection integrity of all branches connected to the high-voltage bus on electric vehicles, including power battery packs, controllers, high-voltage distribution boxes, etc. The lock pin is usually in the middle of the high-voltage plug. When the high-voltage plug falls off, the whole vehicle can be powered off at the moment the plug falls off without making any pins.

2. High voltage interlocking features

1. The HVIL circuit must be able to effectively, in real time and continuously monitor the on/off status of the entire high-voltage circuit.

2. All high-voltage connectors cannot be connected or disconnected without human intervention.

3. All connectors should be equipped with mechanical interlocking devices, and the HVIL should be disconnected first when the high-voltage connector is disconnected and connected last when it is connected.

4. The high voltage interlock circuit should be able to detect the HVIL circuit directly through the BMS under special circumstances.

Directly disconnect the high-voltage circuit.

5. When an abnormality is detected in the HVIL, the vehicle must give an alarm indication to alert the driver.

2. Classification of high voltage interlocking lines

(1) Series

Through a low-voltage line, the high-voltage connector at the unit end of the main high-voltage unit and the high-voltage connector at the wiring harness end are short-circuited and connected. The VCU can know the integrity of the high-voltage component connection by detecting the signal on this line.

(2) Parallel

The high-voltage interlock circuit is integrated inside the high-voltage control unit, and there is no external connection harness. Each high-voltage connector interlock circuit is detected by the unit separately. If a high-voltage connector connection fails, the unit will immediately determine the fault location, which is convenient for detection and maintenance.

3. Geely EV series high voltage interlocking circuit

The Geely EV series high-voltage interlocking circuit adopts the method of series connection and waveform detection. The main high-voltage components involved in the high-voltage interlocking are MCU and high-voltage wiring harness, OBC and high-voltage wiring harness, PTC heater and high-voltage wiring harness, air-conditioning compressor and high-voltage wiring harness.

The VCU outputs a PWM duty cycle signal with an amplitude of about 3.3V through the CA67/76 terminal. The waveform signal enters the BV11/1 terminal of the MCU through the high-voltage interlock wire, short-circuits (conducts) through the internal high-voltage connector of the MCU, and is output from the BV11/4 terminal of the MCU; then enters the BV10/26 terminal of the on-board charger, short-circuits (conducts) through the internal high-voltage connector of the on-board charger, and is output from the BV10/27 of the on-board charger; then enters the BV08/6 terminal of the air-conditioning compressor controller, short-circuits (conducts) through the internal high-voltage connector of the air-conditioning compressor controller, and is output from the BV08/7 terminal of the air-conditioning compressor controller; then enters the CA61/5 terminal of the PTC heating controller, short-circuits (conducts) through the internal high-voltage connector of the PTC heating controller, and is output from the CA61/7 terminal of the PTC heating controller, and enters the VCUCA66/58 terminal, The VCU pulls the PWM duty cycle signal with an amplitude of about 3.3V to a PWM duty cycle signal with an amplitude of about 12V through the internal pull-up circuit.

4. High voltage interlock detection

If the high-voltage interlock fails, will it cause a short circuit or open circuit and then report a fault? When repairing, we can start from two aspects:

First, external inspection

External inspection is relatively simple: 1. Check whether the interlock plug has any pins removed; 2. Check whether the contacts of the interlock device are dirty; 3. Check whether the power connection of the interlock device is normal. These can be judged by the naked eye. If there are no problems with the above, then internal inspection should be carried out to see if there is any problem with the circuit.

Second, internal testing

Method 1: Measure the voltage using the DC voltage of an outsider meter. If the two pin angles of the interlock line are normal, the voltage at test point A is about 9 volts when the cover is opened, and the voltage at test point A is about 0 volts when the cover is opened.

Method 2: Detect PWM waveform, introduce a switch controlled by PWM signal, measure with external meter, measure the waveform signal on this terminal inside VCU and compare it with the stored normal waveform signal. If the amplitude and frequency of the waveform signal are normal, VCU confirms that the high voltage system circuit is complete. If the amplitude and frequency of the waveform signal are abnormal, or if there is a fault, in order to prevent safety accidents, the vehicle system will prohibit high voltage power-on and generate a fault code.

Unit output waveform after the loop is disconnected

Line waveform when the circuit is normal

chejm

The technical content shared by the host is very valuable. I hope to refer to these guidance suggestions in future projects. Thank you very much