The electric vehicle charging system is the energy supply facility of the power battery, and is a power conversion device that extracts energy from the power supply to charge the power battery. The charging system includes AC (slow) charging system and DC (fast) charging system.
On the market, the new energy vehicles are mostly charged by floor mounted charging posts or wall mounted charging boxes. This article will mainly introduce the floor mounted charging post. Among them, the floor charging piles are mainly divided into integrated charging piles and distributed charging piles.
The main difference between them is that the main control and modules of the integrated charging pile are integrated in this machine, which can be distributed according to the needs of the electric vehicle, and the charging speed is relatively fast. Because the power distribution equipment of the integrated charging pile is integrated into one, and the power is fixed and cannot be upgraded, when a part of the charging pile fails, It is difficult to repair and replace. The split charging post does not contain the main control board module, but only an input of information. All its main control modules are integrated in the centralized control box. Its advantages are very obvious, that is, its power is flexible and can be shared with other charging piles. Because its charging equipment and distribution equipment are operated independently, it is more convenient to repair and replace, and its maintenance cost is low, but its charging speed is not as fast as that of the integrated charging pile. New energy vehicle charging pile
1、 Composition of AC charging pile
AC charging pile is mainly used for AC slow charging of electric vehicles, integrating power conversion, charging control, human-computer interaction control, communication, billing and metering. It is mainly composed of human-computer interaction touch screen, card reader, electric energy metering module, charging module, communication module, charging interface, control module and pile. Its charging power mainly includes 2KW, 3.3KW, 7KW, 11KW, 21KW and 40KW.
1. LCD screen LCD screen is mainly used to display the relevant information of the charging pile, send and present the real-time status information of the charging process to the display screen. It can be operated by touch, allowing users to select different charging modes, namely "time mode", "power mode", "amount mode" and "auto charging mode". It can also be used for information inquiry, parameter setting, record clearing, etc. by the maintenance personnel of the charging pile. The harness plug is mainly composed of two working power lines (power+12V and power negative) and two communication lines (serial port RS232).
2. Card reader
The card reader is mainly used to start charging and charge settlement. Put the valid charging card close to the card swiping area, and a sound of "drip" indicates that the card swiping is successful. The system starts charging, and the page jumps to the information display interface in charging, displaying the information in charging in real time. The harness plug is mainly composed of two working power lines (power supply+5V and power supply negative) and two communication lines (serial port RS232). The swiping unit uses RFID to interact with the user card, with a frequency of 13.56MHz. The card reading information is read by the card reader, and then communicates with the main control board through the RS232 serial interface.
3. Main control module (AC control module)
The main control module is the core part of the whole charging pile and plays a very important role in the whole charging pile. The main control board communicates with the touch screen LED, receives the operation instructions and parameter configuration instructions from the user, and sends the real-time status information of the charging process to the display screen; The main control board communicates with the vehicle mounted charger through the charging gun interface, and starts charging after obtaining the parameter configuration of vehicle charging; The main control board communicates with the card reader, and the charging pile reads the user account information in wireless mode after the user swipes the card; After reading the account information, the main control board communicates with the background monitor/server through Ethernet, uploads the user account, bill and charging pile status to the background, and receives the charging control information sent from the background; The main control module also provides 5V working power supply for the card reader and 12V working power supply for the relay module to control the operation of the relay module; The main control module receives emergency stop switch information, access control switch information, charging gun temperature information, intelligent ammeter information, charging gun CP signal, etc. to control the entire charging process. Electric vehicle charging pile
4. Wiring block
The terminal block is mainly used as the interface of 220V input power supply, so as to distribute the input 220V AC power to the single-phase circuit breaker.
5. Single phase circuit breaker (air switch)
Single phase circuit breaker, also known as air switch, is a switch that will automatically disconnect as long as the current in the circuit exceeds the rated current. Air switch is a very important electrical appliance in low-voltage distribution network and electric drive system. It integrates control and multiple protection functions. In addition to touching and breaking the circuit, it can also protect the short circuit, serious overload and undervoltage of the circuit or electrical equipment. It mainly distributes the 220V voltage transmitted from the wiring bank to the surge protective device (lightning protector) and smart meter after closing. The downstream of the single-phase circuit breaker is connected in parallel with the surge protective device (lightning protector) and connected in series with the smart meter.
6. Surge protective device (lightning arrester)
Surge protectors, also known as lightning protectors, are usually connected in parallel in the circuit system. When lightning occurs, lightning enters various metal pipes and lines of the building, generating high-intensity electromagnetic induction, thus generating a large amount of pulse energy. The function of surge protectors is to lead the overcurrent to the ground and reduce the potential difference at each port of the equipment. It is suitable for the transient over-voltage protection of 220/380V power supply and distribution system, which can effectively suppress the induced over-voltage caused by pipe electricity and system operation over-voltage, protect equipment safety, and ensure the normal operation of the system.
7. Smart electricity meter
Smart electricity meter is the smart terminal of smart grid. It is no longer a traditional electricity meter. In addition to the basic power consumption measurement function of traditional electricity meters, smart electricity meters also have two-way multi rate measurement function, user control function, and self two-way data communication function of multiple data transmission modes in order to adapt to the use of smart grid and new energy Smart meters represent the development direction of intelligent terminals for energy saving smart grid end users in the future. It is usually Shenlian in the circuit, and the single-phase circuit breaker, intelligent ammeter, and AC contactor are connected in series in the circuit (mainly in series with the L line in the AC circuit). It communicates with the main control module through the RS485 communication line, and the main control module calculates its current and electric energy.
8. AC contactor
The AC contactor is mainly used to output 220V AC power to the charging gun after the 220V voltage transmitted from the intelligent ammeter is controlled and closed by the relay module.
2、 Electrical schematic diagram of AC charging pile
The electrical schematic diagram of the AC charging pile takes the AC control box as the center, and connects all electrical components of the charging pile together. The door control switch, emergency stop switch, circuit breaker, contactor, etc. are connected to the input end of the AC control box, the charging gun is connected to the output end of the AC control box, and the display screen, status indicator, etc. are connected to the upper terminal of the AC control box, as shown in the figure.
3、 Charging strategy of AC charging pile
The charging plug is coded by resistance. For example, CC represents the power level of identifiable vehicle charging cable (maximum current load capacity of each phase). For this reason, it is necessary to determine the Rc resistance (as shown in the figure) between CC and PE in the charging plug. The charger uses this resistance to identify the rated charging current. CC also has connection confirmation function.
The communication is carried out through the contact CP, and there is 12V voltage between CP and PE when the operation unit is activated; In the charger, when the plug is identified and locked, the signal will be reduced to about 9V by the resistance R3; After confirming the connection, the charger further closes the resistance R2, the signal drops to about 6V, and then the charging pile closes the power contactor to start charging; At this time, the signal generator in the charging unit sends a 1000Hz PWM signal, which specifies the current maximum charging current. New energy vehicle maintenance
4、 Common faults of AC charging gun
If the AC charging gun fails, you can use a multimeter to measure whether the voltage, current and resistance values of CP - PE terminal, CC - PE terminal and PE terminal meet the set values. The voltage of CC － PE terminal is generally 5V or 12V. The maximum allowable output current and resistance of common AC charging devices are shown in the table below:
1. Plug in the AC charging gun, and after the connection is normal, the OBC is awakened by the CP/CC sent by the AC charging pile. After the OBC judges that the CC/CP is normal, it wakes up the VCU by outputting a 12V voltage signal through the hard wire.
2. After the VCU is awakened, pull on the main relay Main Power Ryy to wake up each E-CAN controller, and wake up the large screen at the same time; Control the high-voltage power on, and send charging enable to BMS after judging that it is rechargeable.
3. After receiving the charging enable sent by the VCU, the BMS sends the charging enable to the OBC, and sends the OBC the charging current and voltage request according to the battery status and the output capacity of the charging pile.
4. The OBC starts charging after receiving the charging enable from the BMS, and converts the 220V AC output from the grid into DC to charge the power battery according to the charging current and voltage requested by the BMS.
