According to the requirements of relevant regulations in China, the method of controlling the pilot circuit is used as the judging device for the connection state and rated current parameters of the charging connection device. The typical control pilot circuit is shown in Figure 1.
After the plug of the power supply equipment is connected to the socket, the power supply control device judges whether the power supply plug and the power supply socket are completely connected by detecting the voltage value of the detection point ④ as shown in Figure 1. At the same time, the electric car car control device judges whether the car plug and the car socket are fully connected by measuring the resistance value between the detection point ③ and PE. After completing the detection of the connection state between the plug and the socket, the operator completes the charging start setting for the power supply equipment, then the switch S1 switches from the +12V connection state to the PWM connection state, and the power supply control device sends a PWM signal. The power supply control device judges whether the charging connection device is fully connected by measuring the voltage value of the detection point ①. The car control terminal closes S2 after the detection is correct. The power supply control device determines whether the car is ready by measuring the voltage value of the detection point ① again. If the requirements are met, the AC power supply circuit is turned on by closing the switch K.
The charging interface refers to the charging component used to connect the active cable and the electric car. It is composed of two parts: the charging socket and the charging plug. It is an essential equipment for the conductive charging method of the electric car. The charging plug is in safe and reliable contact with the charging socket during the charging process, thereby realizing the transmission of electric energy.
There are three main types of charging interfaces for electric cars: single-phase AC charging interface, three-phase AC charging interface and DC charging interface. The single-phase AC charging interface is mainly used for domestic user charging facilities and some standard public charging facilities. This type of charging plug is relatively simple. Generally, the plug has three terminals, namely the AC live wire, the AC neutral wire and the ground wire. It is similar to the traditional power socket, but the shape and rated current are larger.
The three-phase AC charging interface and the DC charging interface are much more complicated than the single-phase AC interface. This type of charging interface is generally used in larger charging stations to charge larger electric cars, and the charging current is relatively large, the shape is large, and the function is complex.
The three-phase AC charging interface contains a total of 7 pairs of contacts, which can meet the current AC single-phase charging, and will be expanded to AC three-phase charging after development. The interface of the AC charging interface connector socket is shown in Figure 2 (a). The connector plug has a locking device to prevent accidental disconnection during connection, and has an anti-misoperation function.
In the process of industrialization of electric cars, the standardization of charging interface is very important. The charging interface should meet the following requirements:
(1) It can realize the transmission and conduction of large current, and avoid the socket heating and failure caused by excessive current.
(2) The plug can be fully bonded with the socket, and the contact resistance is small, so as to avoid spark ablation or virtual connection caused by poor contact.
(3) It can realize the necessary communication functions, which is convenient for the connection between the CAN communication or the battery management system of the electric car and the charging engine.
(4) It has the ability to prevent mis-insertion. Due to the different types and performances of charging equipment or batteries used in electric cars, the required power supply is different. At the same time, due to the different performance of each plug, the electrodes of the plug cannot be inserted wrongly, which requires different power plugs to have certain recognition ability.
(5) With a reasonable shape, it is easy to perform plugging and unplugging operations.
The control guide circuit can satisfy the connection confirmation between the power supply equipment side and the car side, and ensure the matching of the charging current with the car charger, power supply equipment and charging connection device within the allowable value range through the detection of related circuits. During the charging process, the charging current is adjusted in real time by continuously detecting the PWM duty cycle of the power supply equipment to meet the needs of intelligent scheduling on the grid side. The connection method of the charging interface is shown in Figure 3.