CN107742917A - Three-phase PFC rectifier device and control method for electric vehicle high-power charging pile with buck-boost function - Google Patents

Abstract

The invention relates to a three-phase PFC rectification device and a control method of a high-power charging pile for an electric vehicle with a voltage-boosting function. The device includes a rectification module, a voltage-boosting module, a sampling module, a hardware voltage and current detection module, and a comparator module. , DSP processor module, switch tube drive module with protection; wherein: the three-phase grid voltage is connected to the rectifier module through the pin output terminals U _A , U _B , U _C , and the rectifier module and the buck-boost module form a three-phase eight-switch Buck‑Boost rectifier. The present invention adopts a three-phase eight-switch Buck-Boost rectifier as the main topology of the circuit, adopts double closed-loop control, makes its input current close to a sine wave, and has the same phase as the input voltage, the power factor is approximately 1, the structure is simple, the volume is small, and the network The side power factor is high, the charging efficiency is high, and the DC side is connected to the Buck-Boost topology. The output voltage can be flexibly adjusted according to the type of electric vehicle at the output end to meet different requirements for the output voltage, and it can quickly charge different types of electric vehicles. Charge.

Description

Three-phase PFC rectifier device for electric vehicle high-power charging pile with buck-boost function and control method

technical field

The invention relates to the technical field of electric vehicle battery charging, in particular to a three-phase PFC rectifier and a control method of a high-power charging pile for electric vehicles with voltage-boosting functions.

technical background

With the development of human beings, people have to pay attention to the increasingly prominent energy and environmental issues, and electric vehicles are powered by electric energy, which can not only solve the pollution problem of fuel vehicle exhaust emissions, but also reduce the consumption of fossil energy. Therefore, it is gradually favored. Now the number of electric vehicles in my country only accounts for 0.2% of the total number of vehicles, which has great development prospects, and convenient and fast charging facilities can greatly promote the popularization and promotion of electric vehicles.

At present, the charging facilities of electric vehicles can be roughly divided into four categories according to the application occasions: (1) vehicle emergency charging (2) household or public place charging (3) charging pile charging (4) charging station charging. Vehicle emergency charging is usually a contact charger with simple structure and convenient control, or it can be an induction charger. It is completely designed according to the type of car charger, and it is highly targeted. The other three types can be collectively referred to as off-board charging, that is, ground charging. Off-board charging devices are equivalent to car gas stations, and should be able to charge any kind of electric vehicle that needs to be charged. According to the charging voltage, charging facilities can be divided into AC charging and DC charging. Compared with AC charging, DC charging has higher efficiency and will become the first choice for public charging facilities in the future. However, this charging method has higher requirements for equipment and safety, and now it seems more controversial. In comparison, the standard formulation of DC charging is relatively complicated. In terms of DC charging, there are more problems with distance standardization, which involves the problem of high-voltage charging.

High-power DC charging piles have great development prospects because of their high charging efficiency and short charging time. Although the rectification device and control method of the high-power DC charging pile have made great progress with the development of power electronics technology, there are still many problems that need to be further solved. For example, traditional high-power DC charging piles have the following defects:

(1) The volume is too large. The traditional DC charging pile adjusts the output voltage through a transformer or a full-bridge DC/DC circuit. The structure is heavy, the volume is large, and the cost is high.

(2) The output voltage cannot be adjusted flexibly. The charging voltage of electric cars is generally 300V ~ 400V, while the charging voltage of electric buses is generally above 600V. Traditional DC charging piles cannot simultaneously charge different types of electric vehicles. , which reduces the utilization rate of DC charging piles, is not conducive to the promotion of electric vehicles, and reduces the economy of DC charging piles.

(3) Low charging efficiency. Traditional DC charging piles have abundant harmonic current at the input end, low power factor on the grid side, heavy pollution to the grid, and failure to meet electromagnetic compatibility, which greatly reduces charging efficiency.

Contents of the invention

The main purpose of the present invention is to provide a three-phase PFC rectifier and control device for a high-power charging pile of an electric vehicle with a buck-boost function in order to solve the defects of the prior art that the volume is too large, the output voltage cannot be flexibly adjusted, and the charging efficiency is low. method, to overcome the deficiencies of the above-mentioned prior art. The three-phase PFC rectification system of a high-power charging pile for electric vehicles with integrated buck-boosting adopts a three-phase eight-switch Buck-Boost rectifier as the main topology of the circuit, and adopts double closed-loop control to make its input current close to a sine wave, and The same phase as the input voltage, the power factor is approximately 1, the structure is simple, the volume is small, the power factor of the grid side is high, and the charging efficiency is high. The DC side is connected to a Buck-Boost topology, and the output can be flexibly adjusted according to the type of electric vehicle at the output end. Voltage, to meet the different demands on the output voltage, can fast charge different types of electric vehicles.

In order to achieve the above object, the present invention provides a three-phase PFC rectifier device of a high-power charging pile for electric vehicles with a buck-boost function, which includes a rectifier module, a buck-boost module, a sampling module, a hardware voltage and current detection module, a comparison Inverter module, DSP processor module, switch tube drive module with protection; among them: the three-phase grid voltage is connected to the rectifier module through the pin output terminals U _A , U _B , U _C , and the rectifier module and the buck-boost module form a three-phase Eight-switch Buck-Boost rectifier, its circuit structure is:

One end of the first inductor L _f1 is connected to the first input port a of the three-phase rectifier, one end of the second inductor L _f2 is connected to the second input port b of the three-phase rectifier, and one end of the third inductor L _f3 is connected to the third input port of the three-phase rectifier. input port c;

The first capacitor C _f1 and the first inductor L _f1 constitute the low-pass filter of the first input port a, the second capacitor C _f2 and the second inductor L _f2 constitute the low-pass filter of the second input port b, and the third capacitor C _f3 and the third inductance L _f3 constitute the low-pass filter of the third input port c; the other end of the first inductance L _f1 is connected with the anode of the first diode and the cathode of the fourth diode, and the second inductance L _f2 The other end of the second diode is connected to the anode of the second diode and the cathode of the fifth diode, and the other end of the third inductance L _f3 is connected to the anode of the third diode and the cathode of the sixth diode;

The first inductance L _f1 is connected to the source of the switch S _ap and the drain of the switch _San , the second inductance L _f2 is connected to the source of the switch S _bp and the drain of the switch S _bn , and the third inductance L _f3 is connected with the source of the switching tube S _cp and the drain of the switching tube S _cn ; the drain of the switching tube S _p is connected with the cathodes of the first diode, the second diode and the third diode, and the switching tube The source of S _p is connected with the cathodes of the seventh diode, the eighth diode and the ninth diode; the source of the switching tube S _n is connected with the fourth diode, the fifth diode, the sixth diode The anode of the pole tube is connected, and the drain of the switching tube _Sn is connected with the anodes of the tenth diode, the eleventh diode, and the twelfth diode;

One end of the inductor L1 is connected to the cathodes of the seventh diode, the eighth diode, the ninth diode, and the thirteenth diode and the source of the switch S _p , and one end is connected to the drain of the switch S _n . The anodes of the tenth diode, the eleventh diode, and the twelfth diode are connected to the capacitor C1; the capacitor C1 is connected to the output end; the capacitor C1, the discharge resistor R1, and the switch K1 form a discharge circuit.

The three-phase PFC rectifier device of the present invention is used to charge the high-power DC charging pile of electric vehicles with constant current and constant voltage. The first stage is charged with a constant current; when the voltage reaches a predetermined value, it is transferred to the second stage for constant voltage charging. When overvoltage, undervoltage, overcurrent, or overtemperature occur at the output terminal, the DSP processor module immediately sets the duty ratio to zero, and the switch tube drive module with protection immediately outputs a negative pressure drive signal to turn off eight switch tubes. The three-phase Buck-Boost rectifier stops working, and at the same time, the control switch K1 is closed, and the capacitor C1 is discharged through the discharge circuit formed by C1 and R1.

In addition, the present invention provides a method for controlling the three-phase PFC rectifier device of the electric vehicle charging pile with the above-mentioned voltage-boosting function, and the specific control steps include:

S1, the DSP processor module judges whether precharging is required, if necessary, then go to step S2, if not, then go directly to step S3;

S2. The DSP processor module outputs eight channels of PWM waves, making S _p and S _n conductive, S _ap , S _an , S _bp , S _bn , S _cp , and S _cn are disconnected, and the rectification module performs uncontrolled rectification to output The capacitor C1 is pre-charged, and when the set value is reached, step S4 is entered;

S3, the sampling module inputs the voltage and current collected by the AC side into the DSP processor module;

S4. The DSP processor module calculates the voltage value and current value of the AC side collected by the AC side into a three-phase stationary coordinate system/two-phase rotating coordinate system, and obtains the grid voltage angular frequency ω(k) through the digital phase-locked loop function and phase θ(k);

S5, performing constant current charging mode;

S5.1, in the constant current control mode, the comparator module calculates the output current I _out and the reference current I _ref to obtain the output value E2, which is input to the DSP processor module through the input terminal I-14;

S5.2, calculate the duty cycle through space vector pulse width modulation, and generate eight PWM waves;

S5.3, input the eight-way PWM wave into the switch tube drive module with protection, generate eight-way drive signals, and act on the on-off of the three-phase eight-switch Buck-Boost rectifier switch tube, and perform constant current mode charging;

S5.4, input the output terminal voltage and current to the hardware voltage and current detection module, judge the working mode at this time, and input the judgment result into the comparator module, when it is detected that the output terminal voltage reaches the predetermined value, the system transfers to the first step Constant voltage charging in the second stage;

S6, performing a constant voltage charging mode;

S6.1. In the constant voltage control mode, the comparator module calculates the output voltage U _out and the reference voltage U _ref to obtain the output value E1, which is input to the DSP processor module through the input terminal I-15;

S6.2. Through space vector pulse width modulation, the duty ratio is calculated to generate eight channels of PWM waves;

S6.3. Input the eight-way PWM wave into the switch tube drive module with protection to generate eight-way drive signals, which act on the on-off of the three-phase eight-switch Buck-Boost rectifier switch tube, and perform constant voltage mode charging;

S6.4, the DSP processor module judges whether to end the work, when the device needs to continue to work, turn to step S5.3; when the work is finished, enter the next step;

S6.5. The DSP processor module sets the duty cycle to zero, and the switch tube drive module with protection immediately outputs a negative pressure drive signal, turns off eight switch tubes, the three-phase Buck-Boost rectifier stops working, and the control switch K1 is closed at the same time , The capacitor C1 is discharged through the discharge circuit composed of C1 and R1.

Compared with the prior art, the present invention has the following advantages:

1. The traditional three-phase Buck-Boost rectifier has been improved, and the eight switching tubes are controlled by switching power supply technology, which effectively reduces the power loss of the switching tubes and has a high power factor;

2. The use of semiconductor diodes with low forward voltage drop and low reverse leakage current reduces the loss of the switch tube;

3. Simple structure, small size, convenient operation, high charging efficiency, low harmonic interference, high working stability and reliability, strong practicability, and easy promotion and use;

4. The output terminal adopts Buck-Boost topology, which can realize the flexible step-up and step-down output of the output DC voltage, which can meet a wide range of car charging voltages, and can quickly charge different types of electric cars, improving the utilization rate of charging piles , greatly improving the economy of charging piles.

Description of drawings

Fig. 1 is a schematic structural diagram of a three-phase PFC rectifier device of a high-power charging pile for an electric vehicle with a buck-boost function according to the present invention.

Fig. 2 is a flowchart of a control method of the three-phase PFC rectifier device of the present invention.

In the figure, 100-rectifier module, 110-boost-boost module, 120-sampling module, 130-hardware voltage and current detection module, 140-comparator module, 150-DSP processor module, 160-switch tube drive module with protection .

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. Below in conjunction with accompanying drawing, technical scheme of the present invention is specifically described:

As shown in Figure 1, a three-phase PFC rectification system of a high-power charging pile for electric vehicles with a buck-boost function according to an embodiment of the present invention includes a rectifier module 100, a buck-boost module 110, a sampling module 120, a hardware voltage and current A detection module 130 , a comparator module 140 , a DSP processor module 150 , and a protected switching tube drive module 160 .

In this embodiment, the output power of the device can reach 66KW, the three-phase AC voltage is 380V, and the frequency is 50HZ. It is charged with constant current and constant voltage. The first stage is charged with a constant current; when the voltage reaches a predetermined value, it is transferred to the second stage. Constant voltage charging, at this time the current gradually decreases; when the charging current reaches zero, the battery is fully charged.

In this embodiment, the three-phase grid voltage is connected to the three-phase Buck-Boost rectifier through the pin output terminals U _A , U _B , and U _C. The circuit structure of the three-phase Buck-Boost rectifier is:

One end of the first inductor L _f1 is connected to the first input port a of the three-phase rectifier, one end of the second inductor L _f2 is connected to the second input port b of the three-phase rectifier, and one end of the third inductor L _f3 is connected to the third input port of the three-phase rectifier. input port c;

The first capacitor C _f1 and the first inductor L _f1 constitute the low-pass filter of the first input port a, the second capacitor C _f2 and the second inductor L _f2 constitute the low-pass filter of the second input port b, and the third capacitor C _f3 and the third inductance L _f3 form a low-pass filter of the third input port c;

The other end of the first inductance L _f1 is connected to the anode of the first diode and the cathode of the fourth diode, and the other end of the second inductance L _f2 is connected to the anode of the second diode and the cathode of the fifth diode The other end of the third inductance L _f3 is connected to the anode of the third diode and the cathode of the sixth diode; the first inductance L _f1 is connected to the source of the switch S _ap and the drain of the switch S _an , the second inductance L _f2 is connected with the source of the switch S _bp and the drain of the switch S _bn , and the third inductance L _f3 is connected with the source of the switch S _cp and the drain of the switch S _cn ;

The drain of the switch tube S _p is connected to the cathodes of the first diode, the second diode, and the third diode, and the source of the switch tube S _p is connected to the seventh diode, the eighth diode, and the third diode. The cathodes of the nine diodes are connected. The source of the switch tube S _n is connected to the anodes of the fourth diode, the fifth diode, and the sixth diode, and the drain of the switch tube S _n is connected to the tenth diode, the eleventh diode, The anode of the twelfth diode is connected;

One end of the inductor L1 is connected to the cathodes of the seventh diode, the eighth diode, the ninth diode, and the thirteenth diode and the source of the switch S _p , and one end is connected to the drain of the switch S _n . The anodes of the tenth diode, the eleventh diode, and the twelfth diode are connected to the capacitor C1; the capacitor C1 is connected to the output terminal, and the capacitor C1, the discharge resistor R1, and the switch K1 form a discharge circuit.

In this embodiment, the other end of the first inductance L _f1 is also respectively connected to the first voltage detector and the first current detector, and the other end of the second inductance L _f2 is also respectively connected to the second voltage detector and the second A current detector, the other end of the third inductance L _f3 is also respectively connected to a third voltage detector and a third current detector; the voltage values U _A , U _B , and _UC and the first, second and third current detectors detect the current values I _A , I _B , and I _C through the input terminals I-1, I-2, I-3, I-4, and I of the sampling module 120 respectively. -5, I-6 is input to the sampling module, and the output sampling values U _A (k), U _B (k), U _C (k), I _A (k), I _B (k), I _C ( k) respectively through the output terminals O-1, O-2, O-3, O-4, O-5, O-6 through the input terminals I-7, I-8, I-9, I-6 of the DSP processor 10. I-11 and I-12 are input to the DSP processor module, and the calculation of the three-phase stationary coordinate system/two-phase rotating coordinate system is performed through the DSP processor, and the grid voltage angular frequency ω(k is obtained through the digital phase-locked loop function ) and phase θ(k), the output terminal current, output terminal voltage, reference current and reference voltage are respectively input to the comparator module 120 through the input terminals I-20, I-21, I-22 and I-23 of the comparator module Among them, the output terminal current and the output terminal voltage are respectively input into the hardware voltage and current detection module 130 through the input terminals I-18 and I-19, and the voltage and current detection result J1 is input into the DSP processor module 150 through the input terminal I-16 , when overvoltage, undervoltage, or overcurrent occurs, the DSP processor module immediately sets the duty ratio to zero, and the switch tube drive module with protection immediately outputs a negative pressure drive signal to turn off eight switch tubes, three-phase The Buck-Boost rectifier stops working, and at the same time, the control switch K1 is closed, and the capacitor C1 is discharged through the discharge circuit formed by C1 and R1.

In this embodiment, the temperature detection is input into the DSP processor module 150 through the input terminal I-17, and when it is detected that the temperature is too high, the DSP processor module controls the cooling fan to start working through the output terminal O-7, and the DSP processes The converter module immediately sets the duty cycle to zero, and the switch tube drive module with protection immediately outputs a negative pressure drive signal, turns off eight switch tubes, and the three-phase Buck-Boost rectifier stops working. At the same time, the control switch K1 is closed, and through C1, R1 The formed discharge circuit discharges the capacitor C1.

In this embodiment, the hardware voltage and current detection module 130 inputs a signal to the comparator module 140 through the input terminal I-24, and the working state of the switching ratio module 140 is constant voltage control mode or constant current control mode. In the constant voltage control mode, the comparator module 120 operates on the output voltage U _out and the reference voltage U _ref to obtain an output value E1, which is input to the DSP processor module 150 through the input terminal I-15. In the constant current control mode, the comparator module 120 calculates the output current I _out and the reference current I _ref to obtain an output value E2 , which is input to the DSP processor module 150 through the input terminal I- 14 . When the voltage level of the output capacitor C1 reaches the set value and there is no overvoltage, undervoltage, overcurrent, or overtemperature, in the DSP processor module, according to the data input to the DSP processor module, through the space vector pulse width modulation algorithm, Calculate the duty cycle of the PWM modulation wave, generate eight strobe pulses G _pwm1 , G _pwm2 , G _pwm3 , G _pwm4 , G _pwm5 , G _pwm6 , G _pwm7 , G _pwm8 , and pass the output ports O-11, O-12 . , G5, G6, G7, and G8 respectively act on the switching tubes _{SP, S n ,} S _ap , S _an , S _bp , S _bn , S _cp , and S _cn to control their on or off time to achieve rectification regulation pressure purpose.

The specific control steps of the three-phase PFC rectifier device of the electric vehicle charging pile with the above-mentioned voltage-boosting function include:

Step S100, start;

Step S110, each module of the three-phase PFC rectification system is initialized;

Step S120, the output terminal voltage detection device detects the voltage value of the charging electric vehicle;

Step S130, the DSP processor module 150 judges whether precharging is required, if necessary, then go to step S140, if not, then go directly to step S150;

Step S140, the DSP processor module 150 outputs eight channels of PWM waves, making S _p and S _n conductive, S _ap , S _an , S _bp , S _bn , S _cp , and S _cn are disconnected, and the rectification module 100 performs uncontrolled rectification , to precharge the output capacitor C1, and when the set value is reached, proceed to step S150;

Step S150, the sampling module 120 inputs the voltage and current collected by the AC side into the DSP processor module 150;

In step S160, the DSP processor module 150 performs calculations in the three-phase stationary coordinate system/two-phase rotating coordinate system on the AC side voltage value and current value collected by the AC side, and obtains the grid voltage angular frequency ω( k) and phase θ(k);

Step S170, perform constant current charging mode;

Step S180, in the constant current control mode, the comparator module 120 calculates the output current I _out and the reference current I _ref to obtain an output value E2, which is input to the DSP processor module 150 through the input terminal I-14;

Step S190, calculate the duty ratio through space vector pulse width modulation, and generate eight channels of PWM waves;

In step S200, eight channels of PWM waves are input into the protected switch tube drive module 160 to generate eight channels of drive signals, which are used to switch on and off the switch tubes of the three-phase eight-switch Buck-Boost rectifier to perform constant current mode charging;

Step S210, input the output terminal voltage and current to the hardware voltage and current detection module 130, judge the working mode at this time, and input the judgment result into the comparator module 140, when it is detected that the output terminal voltage reaches a predetermined value, the system transfers to Constant voltage charging in the second stage;

Step S220, performing constant voltage charging mode;

Step S230, in the constant voltage control mode, the comparator module 120 calculates the output voltage U _out and the reference voltage U _ref to obtain an output value E1, which is input to the DSP processor module 150 through the input terminal I-15;

Step S240, calculate the duty ratio through space vector pulse width modulation, and generate eight channels of PWM waves;

In step S250, eight channels of PWM waves are input into the protected switching tube drive module 160 to generate eight channels of driving signals, which are used to switch on and off the switching tubes of the three-phase eight-switch Buck-Boost rectifier to perform constant voltage mode charging;

Step S260, the DSP processor module 150 judges whether to end the work, and when the device needs to continue to work, turn to step S220;

In step S270, the DSP processor module 150 sets the duty cycle to zero, and the switching tube drive module with protection immediately outputs a negative pressure driving signal, turns off eight switching tubes, stops the three-phase Buck-Boost rectifier, and simultaneously controls the switch K1 to close , the capacitor C1 is discharged through the discharge circuit composed of C1 and R1;

Step S280, end.

The technical solutions of the present invention will be described in detail below in conjunction with the examples.

Taking the charging of BAIC EV as an example, perform the following operations according to the above control steps:

First, initialize each module of the high-power DC charging pile program;

Further, it is detected that the load voltage to be output is 320V, set it as a reference voltage and input it into the DSP processor, the output power is 16KW, and the reference output current obtained according to the output voltage and output power is 50A, and input it into the DSP processor;

Further, the DSP processor judges that system charging does not require pre-charging;

Further, the voltage and current of the AC side are input into the DSP processor through the sampling module, and the DC voltage and current of the DC side of the rectifier are input into the DSP processor at the same time, and the calculation of the three-phase stationary coordinate system/two-phase rotating coordinate system is performed, And obtain grid voltage angular frequency ω(k) and phase θ(k) through digital phase-locked loop function;

Further, the output terminal voltage and current are input into the hardware voltage and current detection module, the system uses constant current and constant voltage charging, and the first stage is charged with a constant current of 50A, and at the same time the output terminal voltage, output terminal current, reference voltage, reference current Input to the comparator module, through the calculation of the comparator module, the comparison result is input to the DSP processor, and when the voltage level of the output capacitor C1 reaches the set value and there is no overvoltage, undervoltage, overcurrent, or overtemperature, it will be processed by the DSP In the device module, according to the data input to the DSP processor module, after processing and calculation, through the space vector pulse width modulation algorithm, the duty cycle is calculated, and eight PWM waves are generated and input to the switch tube drive module with protection to generate eight drives. The signal is used to switch on and off the switching tube of the three-phase eight-switch Buck-Boost rectifier to charge in constant current mode;

Further, when it is detected that the voltage at the output terminal reaches a predetermined value of 320V, it will switch to the second stage for constant voltage charging. At this time, the current will gradually decrease, and at the same time, the voltage at the output terminal, the current at the output terminal, the reference voltage, and the reference current will be input to the comparator In the module, through the calculation of the comparator module, the comparison result is input to the DSP processor, and when the voltage level of the output capacitor C1 reaches the set value and there is no overvoltage, undervoltage, overcurrent, or overtemperature in the DSP processor module, According to the data input to the DSP processor module, after processing and calculation, through the space vector pulse width modulation algorithm, the duty cycle is calculated, and eight PWM waves are generated and input to the switch tube drive module with protection to generate eight driving signals. Eight-phase switch Buck-Boost rectifier switch on and off, charging in constant voltage mode;

Further, the DSP processor module judges whether to end the work. When it is necessary to continue to work, repeat the above steps. When the charging is completed, the DSP processor module will set the duty ratio to zero, and the switch tube drive module with protection will immediately output negative pressure drive signal, turn off the eight switching tubes, the three-phase Buck-Boost rectifier stops working, and at the same time, the control switch K1 is closed, and the capacitor C1 is discharged through the discharge circuit composed of C1 and R1;

Charging is complete.

Claims (7)

1. A three-phase PFC rectifier of an electric vehicle high-power charging pile with buck-boost function, characterized in that it comprises a rectifier module, a buck-boost module, a sampling module, a hardware voltage and current detection module, a comparator module, and a DSP Processor module, switch tube drive module with protection; among them: the three-phase grid voltage is connected to the rectifier module through the pin output terminals U _A , U _B , U _C , and the rectifier module and the buck-boost module form a three-phase eight-switch Buck- Boost rectifier, its circuit structure is: One end of the first inductor L _f1 is connected to the first input port a of the three-phase rectifier, one end of the second inductor L _f2 is connected to the second input port b of the three-phase rectifier, and one end of the third inductor L _f3 is connected to the third input port of the three-phase rectifier. input port c; The first capacitor C _f1 and the first inductor L _f1 constitute the low-pass filter of the first input port a, the second capacitor C _f2 and the second inductor L _f2 constitute the low-pass filter of the second input port b, and the third capacitor C _f3 and the third inductance L _f3 constitute the low-pass filter of the third input port c; the other end of the first inductance L _f1 is connected with the anode of the first diode and the cathode of the fourth diode, and the second inductance L _f2 The other end of the second diode is connected to the anode of the second diode and the cathode of the fifth diode, and the other end of the third inductance L _f3 is connected to the anode of the third diode and the cathode of the sixth diode; The first inductance L _f1 is connected to the source of the switch S _ap and the drain of the switch _San , the second inductance L _f2 is connected to the source of the switch S _bp and the drain of the switch S _bn , and the third inductance L _f3 is connected with the source of the switching tube S _cp and the drain of the switching tube S _cn ; the drain of the switching tube S _p is connected with the cathodes of the first diode, the second diode and the third diode, and the switching tube The source of S _p is connected with the cathodes of the seventh diode, the eighth diode and the ninth diode; the source of the switching tube S _n is connected with the fourth diode, the fifth diode, the sixth diode The anode of the pole tube is connected, and the drain of the switching tube _Sn is connected with the anodes of the tenth diode, the eleventh diode, and the twelfth diode; One end of the inductor L1 is connected to the cathodes of the seventh diode, the eighth diode, the ninth diode, and the thirteenth diode and the source of the switch S _p , and one end is connected to the drain of the switch S _n . The anodes of the tenth diode, the eleventh diode, and the twelfth diode are connected to the capacitor C1; the capacitor C1 is connected to the output end; the capacitor C1, the discharge resistor R1, and the switch K1 form a discharge circuit. 2. According to claim 1, the three-phase PFC rectifier device of the electric vehicle high-power charging pile with buck-boost function, characterized in that: the switching tubes S _P , S _n , S _ap , S _an , S _bp , S _bn , S _cp , and S _cn are MOS tubes or IGBT tubes; the first to thirteenth diodes are semiconductor diodes with low forward conduction voltage drop and low reverse leakage current. 3. The three-phase PFC rectifier device of the high-power charging pile for electric vehicles with buck-boost function according to claim 1, characterized in that: the other end of the first inductance L _f1 is also respectively connected to the first voltage detector and the second A current detector, the other end of the second inductance L _f2 is also respectively connected with the second voltage detector and the second current detector, and the other end of the third inductance L _f3 is also respectively connected with the third voltage detector and the third current detector Detector; The voltage values U _A , U _B , and U _C detected by the first, second, and third voltage detectors and the current values I _A , I _B , and I _C detected by the first, second, and third current detectors are respectively related to the sampling The input terminals I-1, I-2, I-3, I-4, I-5, and I-6 of the module are connected, and the output sampling values U _A (k), U _B (k), U _C of the sampling module (k), I _A (k), I _B (k), and I _C (k) communicate with DSP respectively through output terminals O-1, O-2, O-3, O-4, O-5, and O-6 The input terminals I-7, I-8, I-9, I-10, I-11, I-12 of the processor module 150 are connected. 4. according to claim 1, the three-phase PFC rectifier of the electric vehicle high-power charging pile with buck-boost function is characterized in that: the temperature detection module is connected with the input terminal I-17 of the DSP processor module, and the DSP processes The controller module is connected to the cooling fan through the output port O-7; the actual output current and output voltage are respectively connected to the input terminals I-18 and I-19 of the hardware voltage and current detection module, and are respectively connected to the input terminal I of the comparator module. -20 and I-21 are connected, and the reference voltage and reference current are respectively connected to the ports I-22 and I-23 of the comparator module; the output result of the hardware voltage and current detection module is passed through the output terminal O-10 and the output port O-11 It is connected with the input terminal I-16 of the DSP processor module and the input terminal I-24 of the comparator module. The output result of the comparator module is connected with the I-14 and I-14 of the DSP processor module through the output terminals O-8 and O-9. 15 connected. 5. The three-phase PFC rectifier of the electric vehicle high-power charging pile with buck-boost function according to claim 1, characterized in that: the DSP processor module outputs eight PWM waves G _pwm1 , G _pwm2 , G _pwm3 , G _pwm4 , G _pwm5 , G _pwm6 , G _pwm7 , G _pwm8 respectively output to the belt The input terminal I-25, I-26, I-27, I-28, I-29, I-30, I-31, I-32 of the switching tube drive module 160 of protection; DSP processor module passes output terminal O -19 is connected to switch K1; the drive signal generated by the protected switch tube drive module acts on the switch tubes S _p , S _n , S _ap , respectively through the output terminals G1, G2, G3, G4, G5, G6, G7, and G8 S _an , S _bp , S _bn , S _cp , S _cn . 6. According to claim 1, the three-phase PFC rectifier device of the electric vehicle high-power charging pile with buck-boost function, characterized in that: the DSP processor module 150 controls the switch tubes S _p , S _n , S _ap , S _an , S _bp , S _bn , S _cp , S _cn and K1 are turned on and off. When overvoltage, overcurrent and overtemperature are detected in the system, the switch tubes S _p , S _n , S _ap and S _an , S _bp , S _bn , S _cp , S _cn , the three-phase eight-switch Buck-Boost rectifier stops working, and at the same time the control switch K1 is closed, and the capacitor C1 is discharged through the discharge circuit composed of C1 and R1; the DSP processor module according to The result of the temperature detection controls the start and stop of the cooling fan. 7. The control method of the three-phase PFC rectifier according to claim 1, is characterized in that, comprising: S1, the DSP processor module judges whether precharging is required, if necessary, then go to step S2, if not, then go directly to step S3; S2. The DSP processor module outputs eight channels of PWM waves, making S _p and S _n conductive, S _ap , S _an , S _bp , S _bn , S _cp , and S _cn are disconnected, and the rectification module performs uncontrolled rectification to output The capacitor C1 is pre-charged, and when the set value is reached, step S4 is entered; S3, the sampling module inputs the voltage and current collected by the AC side into the DSP processor module; S4. The DSP processor module calculates the voltage value and current value of the AC side collected by the AC side into a three-phase stationary coordinate system/two-phase rotating coordinate system, and obtains the grid voltage angular frequency ω(k) through the digital phase-locked loop function and phase θ(k); S5, performing constant current charging mode; S5.1, in the constant current control mode, the comparator module calculates the output current I _out and the reference current I _ref to obtain the output value E2, which is input to the DSP processor module through the input terminal I-14; S5.2, calculate the duty cycle through space vector pulse width modulation, and generate eight PWM waves; S5.3, input the eight-way PWM wave into the switch tube drive module with protection, generate eight-way drive signals, and act on the on-off of the three-phase eight-switch Buck-Boost rectifier switch tube, and perform constant current mode charging; S5.4, input the output terminal voltage and current to the hardware voltage and current detection module, judge the working mode at this time, and input the judgment result into the comparator module, when it is detected that the output terminal voltage reaches the predetermined value, the system transfers to the first step Constant voltage charging in the second stage; S6, performing constant voltage charging mode; S6.1. In the constant voltage control mode, the comparator module calculates the output voltage U _out and the reference voltage U _ref to obtain the output value E1, which is input to the DSP processor module through the input terminal I-15; S6.2. Through space vector pulse width modulation, the duty ratio is calculated to generate eight channels of PWM waves; S6.3. Input the eight-way PWM wave into the switch tube drive module with protection to generate eight-way drive signals, which act on the on-off of the three-phase eight-switch Buck-Boost rectifier switch tube, and perform constant voltage mode charging; S6.4, the DSP processor module judges whether to end the work, when the device needs to continue to work, turn to step S5.3; when the work is finished, enter the next step; S6.5. The DSP processor module sets the duty cycle to zero, and the switch tube drive module with protection immediately outputs a negative pressure drive signal, turns off eight switch tubes, the three-phase Buck-Boost rectifier stops working, and the control switch K1 is closed at the same time , The capacitor C1 is discharged through the discharge circuit composed of C1 and R1.