High-efficiency direct-current charging pile based on SiC device

Abstract

The invention relates to the technical field of direct current charging piles, and discloses a high-efficiency direct current charging pile based on a SiC device, which comprises a rectifier module, a DC-DC conversion module, an output filtering and battery interface module, a control and communication module, an auxiliary power supply and heat dissipation module and a safety and protection module. According to the invention, the Vienna rectifier is utilized to carry out efficient rectification on three-phase alternating current input, a power factor correction (PFC) mechanism is introduced to realize power factor correction, and the SiC MOSFET device is introduced to support high-frequency and high-efficiency switching operation, so that the conduction and switching loss is obviously reduced, and the power factor correction is realized. And the phase-shift full-bridge converter is matched to realize efficient and isolated conversion from the DC bus voltage to the output voltage of the charging end, so that electric vehicle batteries with different voltage levels are adapted, and the problems of low efficiency and low power factor in the traditional scheme are effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current (DC) charging piles, and in particular to a high-efficiency DC charging pile based on SiC devices. Background Art

[0002] With the rapid development of the new energy vehicle industry, performance requirements for electric vehicle charging systems are constantly increasing. DC fast chargers, due to their fast charging speed and suitability for high-power scenarios, are becoming one of the mainstream charging methods in the future. However, existing DC chargers still have significant deficiencies in conversion efficiency, volume control, electromagnetic compatibility, and heat dissipation performance. In traditional solutions, AC input is directly converted into DC voltage through a diode rectifier, and then output through a boost or isolated DC-DC converter. Although this structure is simple to implement, it still has the following problems: 1. Low efficiency: Traditional silicon-based power devices have large switching losses and conduction losses, making it difficult to support high-frequency and high-efficiency operation; 2. Low power factor and serious grid pollution: Without an effective power factor correction (PFC) mechanism, the grid-side current is distorted and the harmonic content is high. Summary of the Invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a high-efficiency DC charging pile based on SiC devices.

[0004] The present invention proposes a high-efficiency DC charging pile based on SiC devices, including a rectifier module, a DC-DC conversion module, an output filter and battery interface module, a control and communication module, an auxiliary power supply and heat dissipation module, and a safety and protection module; The rectifier module includes a Vienna rectifier and a PFC module; The DC-DC conversion module includes a DC-DC conversion unit and a phase-shifted full-bridge converter; The output filtering and battery interface module includes an LC filtering circuit and a charging connector; The control and communication module includes a communication interface, an A / D sampling unit, a PWM controller and a main control unit.

[0005] Preferably, the Vienna rectifier is used to convert the three-phase AC power supply into a DC voltage and perform power factor correction through the PFC module to ensure that the grid-side current is a sine wave with a high power factor; The Vienna rectifier includes SiC MOSFET tubes SIC1, SiC MOSFET tubes SIC2, SiC MOSFET tubes SIC3 and SiC MOSFET tubes SIC4, wherein pin 2 of SiC MOSFET tube SIC1 is electrically connected to one end of capacitor C2, the other end of capacitor C2 is electrically connected to pin 1 of SiC MOSFET tube SIC2, pin 1 of SiC MOSFET tube SIC1 is electrically connected to pin 1 of SiC MOSFET tube SIC3, pin 2 of SiC MOSFET tube SIC3 is electrically connected to pin 1 of SiC MOSFET tube SIC4, pin 2 of SiC MOSFET tube SIC2 and pin 2 of SiC MOSFET tube SIC4 are both grounded, pin 2 of SiC MOSFET tube SIC1 is also electrically connected to one end of inductor L1, one end of inductor L1 and pin 2 of SiC MOSFET tube SIC1 are both electrically connected to one end of capacitor C1, the other end of capacitor C1 is grounded, and SiC Pin 2 of MOSFET tube SIC3 is electrically connected to one end of capacitor C3, the other end of capacitor C3 is electrically connected to one end of resistor R1, the other end of resistor R1 is electrically connected to one end of inductor L2, and pin 1 of SiC MOSFET tube SIC4 is electrically connected to one end of resistor R2, the other end of resistor R2 is electrically connected to one end of inductor L3.

[0006] Preferably, the DC-DC conversion unit includes a high-frequency transformer T1, wherein pin 1 of the high-frequency transformer T1 is electrically connected to one end of a resistor R3, the other end of the resistor R3 is electrically connected to pin 1 of a SiC MOSFET tube SIC5 and the cathode of a diode D1, pin 2 of the SiC MOSFET tube SIC5 is electrically connected to pin 1 of a SiC MOSFET tube SIC6, the anode of the diode D1 is electrically connected to the cathode of a diode D2, the anode of the diode D2 is electrically connected to pin 2 of the SiC MOSFET tube SIC6, pin 2 of the high-frequency transformer T1 is electrically connected to one end of a resistor R4, the other end of the resistor R4 is electrically connected to pin 2 of the SiC MOSFET tube SIC6, pin 3 of the high-frequency transformer T1 is electrically connected to one end of a capacitor C4 and one end of a capacitor C5, pin 4 of the high-frequency transformer T1 is electrically connected to one end of a resistor R5, and the other end of the resistor R5, the other end of the capacitor C4, and the other end of the capacitor C5 are all grounded.

[0007] Preferably, the output filter and battery interface module is used to filter out high-frequency ripples at the output of the DC-DC converter, providing a smooth, low-noise DC output to communicate with the BMS system of the electric vehicle battery; The LC filter circuit includes a capacitor C6 and a resistor R6, the capacitor C6 and the resistor R6 are connected in parallel, and the charging connector is connected to the electric vehicle battery management system; The phase-shifted full-bridge converter is used to convert the high-voltage DC bus voltage into a DC voltage suitable for charging the electric vehicle battery, supports soft switching, and achieves electrical isolation between the grid and the vehicle through a high-frequency transformer; The phase-shift full-bridge converter includes a transistor Q1 and a transistor Q2. Pins 1 and 2 of the transistor Q1 are connected in parallel with a diode D3. Pins 1 and 2 of the transistor Q2 are connected in parallel with a diode D4. The anode of the diode D3 is electrically connected to the cathode of the diode D4. Pin 1 of the transistor Q1 is also electrically connected to pin 1 of the SiC MOSFET tube SIC7, pin 1 of the SiC MOSFET tube SIC9, and pin 1 of the high-frequency transformer T2. Pin 2 of the SiC MOSFET tube SIC7 is electrically connected to pin 1 of the SiC MOSFET tube SIC8 and one end of the capacitor C7. The other end of the capacitor C7 is electrically connected to pin 2 of the SiC MOSFET tube SIC9. Pin 2 of the SiC MOSFET tube SIC9 is electrically connected to pin 1 of the SiC MOSFET tube SIC10. Pin 2 of the SiC MOSFET tube SIC10 and the SiC Pin 2 of the MOSFET tube SIC8 and pin 2 of the transistor Q2 are both electrically connected to pin 2 of the high-frequency transformer T2, and pins 4 and 3 of the high-frequency transformer T2 are connected in parallel with the capacitor C6; The transistor Q1, SiC MOSFET tube SIC7 and SiC MOSFET tube SIC8 form a main bridge arm, and the transistor Q2, SiC MOSFET tube SIC9 and SiC MOSFET tube SIC10 form a secondary bridge arm.

[0008] Preferably, the control and communication module is used to control the operation of the entire charging pile, including voltage, current regulation, protection and status monitoring, to achieve communication with electric vehicles and background systems. The main control unit includes a main control chip U1, pin 1 of the main control chip U1 is connected to the communication interface, pin 2 of the main control chip U1 is connected to the A / D sampling unit, pin 3 of the main control chip U1 is connected to the PWM controller, and pin 4 of the main control chip U1 is electrically connected to one end of the resistor R6.

[0009] Preferably, the specific steps of performing power factor correction by the PFC module are as follows: S101: Real-time sampling of the three-phase input (L1, L2, L3), input voltage V in (t), input current I in (t); S102: Generate target current waveform: Sampled input voltage V in (t) is normalized and used as the current reference waveform using the following formula: , where Pout is the output power, ensuring I ref (t) vs. V in (t) Same phase, same frequency, and proportional; S103: Perform error calculation to obtain the current current error e(t). The formula used is: e(t)=I ref (t)-I in (t); S104: The error e(t) is sent to the PWM controller, and the output is the voltage control variable u(t), which is used to adjust the PWM duty cycle. The formula used is: ; S105: Using the control output u(t), the switching duty cycle of the SiC MOSFET tubes SIC1 to SiC MOSFET tubes SIC4 is controlled, and a high-frequency modulation method is used to accurately modulate the input current waveform to match the voltage waveform; S106: As the current inner loop is closed, the input current waveform approaches the target waveform I ref (t), and the input current and voltage waveforms have the same frequency and phase, the waveform is close to sinusoidal, and the power factor PF reaches 1; S107: Detect input voltage drop and current overcurrent in real time. Once abnormal, turn off PWM output and execute soft shutdown or fault protection process.

[0010] Preferably, the specific logical steps of the phase-shifted full-bridge converter operation are as follows: S201: When the high-voltage DC bus voltage output by the PFC module stabilizes, the bus voltage is sampled to confirm that the voltage is within the allowable range, the main control unit is started, the main control unit is initialized, the PWM duty cycle is set to the minimum value, and the soft start mechanism is started; S202: The PWM controller turns on the bridge arms and drives the two bridge arms in a phase-shift control mode; S203: Apply a square wave PWM signal with a frequency of 50kHz-150kHz to the two bridge arms, and change the effective conduction time of the primary side of the transformer by adjusting the phase difference between the two bridge arms. The formula used is: The larger the phase shift angle, the greater the output power, and when the phase shift angle is 0, there is no power output; S204: Utilizes the leakage inductance energy of high-frequency transformer T2 to generate a "voltage swing" after each SiC MOSFET is turned off, reducing Vds to 0 before the next MOSFET is turned on, achieving ZVS, reducing switching losses, and improving efficiency. This is particularly suitable for the high-frequency and high-speed switching characteristics of SiC devices. S205: The primary side of high-frequency transformer T2 converts the PWM-modulated high-frequency DC signal into isolated high-frequency AC. The secondary side, after rectification and filtering, outputs a stable and suitable DC voltage, thus achieving electrical isolation and ensuring the safety of both the driver and the vehicle. S206: The secondary side of high-frequency transformer T2 is equipped with a rectifier circuit, which is smoothed by an LC filter and connected to the battery interface of the electric vehicle. S207: The main control unit collects output voltage and current signals, compares them with target values, calculates errors, and uses a PWM controller to adjust the phase shift angle Δφ to adjust the output.

[0011] Preferably, the specific logical steps of the Vienna rectifier are as follows: S301: A three-phase AC power source is connected to the input of the Vienna rectifier, connected to inductors L1, L2, and L3, and a boost power unit is connected to each phase. S302: The control unit starts and drives each SiC MOSFET tube in a continuous current mode, so that each SiC MOSFET tube is turned on in a corresponding phase sequence; S303: The three-phase input current flows through the corresponding inductor, and the SiC MOSFET is turned on to form a boost path. At the same time, the PWM controller adjusts the duty cycle to achieve constant output voltage and sinusoidal input current. S304: Capacitors C1, C2, and C3 form a DC bus center potential clamping network to maintain symmetrical voltage division between the two capacitors on the DC side, ensuring output stability. Simultaneously, the PWM controller monitors midpoint voltage deviation in real time and adjusts device conduction to maintain voltage balance. S305: Resistors R1 and R2, inductors L2 and L3 form a sampling current channel. The PWM controller performs closed-loop regulation on the PWM of each phase according to the sampling value to achieve sinusoidalization of the grid current and harmonic suppression, and output a stable voltage.

[0012] Preferably, the auxiliary power supply and heat dissipation module is used to provide stable low-voltage power supply to the main control unit, PWM driver, A / D sampling module, and communication interface, and forcedly dissipate heat for SiC devices, rectifier module, DC-DC module, output filter and battery interface module, and control and communication module through air cooling. At the same time, it is equipped with a temperature sensor to monitor the temperature of key components in real time. When the temperature exceeds the set threshold, it can trigger power reduction output or forced shutdown protection; The safety and protection module is used for overvoltage / undervoltage protection, reverse connection protection, overcurrent protection and short circuit protection.

[0013] Compared with the existing technology, the beneficial effects of the present invention are: The present invention utilizes a Vienna rectifier to efficiently rectify three-phase AC input and introduces a power factor correction (PFC) mechanism to achieve power factor correction. Furthermore, by introducing SiC MOSFET tube devices, it supports high-frequency, high-efficiency switching operations, significantly reducing conduction and switching losses. Furthermore, it cooperates with a phase-shifted full-bridge converter to achieve efficient, isolated conversion from the DC bus voltage to the charging-end output voltage, making it suitable for electric vehicle batteries of different voltage levels, effectively solving the problems of low efficiency and low power factor in traditional solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a system block diagram of a high-efficiency DC charging pile based on SiC devices proposed in the present invention; Figure 2 This is a circuit diagram of the connection between the Vienna rectifier and the DC-DC conversion unit in a high-efficiency DC charging pile based on SiC devices proposed by the present invention; Figure 3 This is a circuit diagram of the connection between the phase-shifted full-bridge converter, output filter and battery interface module, and control and communication module in a high-efficiency DC charging pile based on SiC devices proposed by the present invention. DETAILED DESCRIPTION

[0015] Example Reference Figure 1-3 ,This embodiment proposes a high-efficiency DC charging pile based on SiC devices, including a rectifier module, a DC-DC conversion module, an output filter and battery interface module, a control and communication module, an auxiliary power supply and heat dissipation module, and a safety and protection module; The rectifier module includes Vienna rectifier and PFC module; The Vienna rectifier is used to convert the three-phase AC power supply into a DC voltage and perform power factor correction through the PFC module to ensure that the grid-side current is a sine wave with a high power factor. The Vienna rectifier includes SiC MOSFET tubes SIC1, SiC MOSFET tubes SIC2, SiC MOSFET tubes SIC3 and SiC MOSFET tubes SIC4. Pin 2 of SiC MOSFET tube SIC1 is electrically connected to one end of capacitor C2, the other end of capacitor C2 is electrically connected to pin 1 of SiC MOSFET tube SIC2, pin 1 of SiC MOSFET tube SIC1 is electrically connected to pin 1 of SiC MOSFET tube SIC3, pin 2 of SiC MOSFET tube SIC3 is electrically connected to pin 1 of SiC MOSFET tube SIC4, pin 2 of SiC MOSFET tube SIC2 and pin 2 of SiC MOSFET tube SIC4 are both grounded, pin 2 of SiC MOSFET tube SIC1 is also electrically connected to one end of inductor L1, one end of inductor L1 and pin 2 of SiC MOSFET tube SIC1 are both electrically connected to one end of capacitor C1, the other end of capacitor C1 is grounded, and SiC Pin 2 of MOSFET tube SIC3 is electrically connected to one end of capacitor C3, the other end of capacitor C3 is electrically connected to one end of resistor R1, the other end of resistor R1 is electrically connected to one end of inductor L2, and pin 1 of SiC MOSFET tube SIC4 is electrically connected to one end of resistor R2, the other end of resistor R2 is electrically connected to one end of inductor L3; The specific logical steps of the Vienna rectifier are as follows: S301: A three-phase AC power source is connected to the input of the Vienna rectifier, connected to inductors L1, L2, and L3, and a boost power unit is connected to each phase. S302: The control unit starts and drives each SiC MOSFET tube in a continuous current mode, so that each SiC MOSFET tube is turned on in a corresponding phase sequence; S303: The three-phase input current flows through the corresponding inductor, and the SiC MOSFET is turned on to form a boost path. At the same time, the PWM controller adjusts the duty cycle to achieve constant output voltage and sinusoidal input current. S304: Capacitors C1, C2, and C3 form a DC bus center potential clamping network to maintain symmetrical voltage division between the two capacitors on the DC side, ensuring output stability. Simultaneously, the PWM controller monitors midpoint voltage deviation in real time and adjusts device conduction to maintain voltage balance. S305: Resistors R1 and R2, inductors L2 and L3 form a sampling current channel. The PWM controller performs closed-loop regulation on the PWM of each phase based on the sampled values to achieve sinusoidalization of the grid current and harmonic suppression, and output a stable voltage. The specific steps for power factor correction through the PFC module are as follows: S101: Real-time sampling of the three-phase input (L1, L2, L3), input voltage V in (t), input current I in (t); S102: Generate target current waveform: Sampled input voltage V in (t) is normalized and used as the current reference waveform using the following formula: , where P out is the output power, ensuring I ref (t) vs. V in (t) Same phase, same frequency, and proportional; S103: Perform error calculation to obtain the current current error e(t). The formula used is: e(t)=I ref (t)-I in (t); S104: The error e(t) is sent to the PWM controller, and the output is the voltage control variable u(t), which is used to adjust the PWM duty cycle. The formula used is: ; S105: Using the control output u(t), the switching duty cycle of the SiC MOSFET tubes SIC1 to SiC MOSFET tubes SIC4 is controlled, and a high-frequency modulation method is used to accurately modulate the input current waveform to match the voltage waveform; S106: As the current inner loop is closed, the input current waveform approaches the target waveform I ref (t), and the input current and voltage waveforms have the same frequency and phase, the waveform is close to sinusoidal, and the power factor PF reaches 1; S107: Real-time detection of input voltage drop and current overcurrent. Once an abnormality occurs, the PWM output is turned off and a soft shutdown or fault protection process is executed; The DC-DC conversion module includes a DC-DC conversion unit and a phase-shifted full-bridge converter; The DC-DC conversion unit includes a high-frequency transformer T1, wherein pin 1 of the high-frequency transformer T1 is electrically connected to one end of a resistor R3, the other end of the resistor R3 is electrically connected to pin 1 of a SiC MOSFET tube SIC5 and the cathode of a diode D1, pin 2 of the SiC MOSFET tube SIC5 is electrically connected to pin 1 of a SiC MOSFET tube SIC6, the anode of the diode D1 is electrically connected to the cathode of a diode D2, the anode of the diode D2 is electrically connected to pin 2 of the SiC MOSFET tube SIC6, pin 2 of the high-frequency transformer T1 is electrically connected to one end of a resistor R4, the other end of the resistor R4 is electrically connected to pin 2 of the SiC MOSFET tube SIC6, pin 3 of the high-frequency transformer T1 is electrically connected to one end of a capacitor C4 and one end of a capacitor C5, pin 4 of the high-frequency transformer T1 is electrically connected to one end of a resistor R5, and the other end of the resistor R5, the other end of the capacitor C4, and the other end of the capacitor C5 are all grounded; The phase-shifted full-bridge converter is used to convert the high-voltage DC bus voltage into a DC voltage suitable for charging electric vehicle batteries. It supports soft switching and achieves electrical isolation between the grid and the vehicle through a high-frequency transformer. The phase-shifted full-bridge converter includes a transistor Q1 and a transistor Q2. Pins 1 and 2 of the transistor Q1 are connected in parallel with a diode D3. Pins 1 and 2 of the transistor Q2 are connected in parallel with a diode D4. The positive electrode of the diode D3 is electrically connected to the negative electrode of the diode D4. Pin 1 of the transistor Q1 is also electrically connected to pin 1 of the SiC MOSFET tube SIC7 and pin 1 of the SiC MOSFET tube SIC9 and pin 1 of the high-frequency transformer T2. Pin 2 of the SiC MOSFET tube SIC7 is electrically connected to pin 1 of the SiC MOSFET tube SIC8 and one end of the capacitor C7. The other end of the capacitor C7 is electrically connected to pin 2 of the SiC MOSFET tube SIC9. Pin 2 of the SiC MOSFET tube SIC9 is electrically connected to pin 1 of the SiC MOSFET tube SIC10. Pin 2 of the SiC MOSFET tube SIC10 and the SiC Pin 2 of the MOSFET tube SIC8 and pin 2 of the transistor Q2 are both electrically connected to pin 2 of the high-frequency transformer T2, and pins 4 and 3 of the high-frequency transformer T2 are connected in parallel with the capacitor C6; Transistor Q1, SiC MOSFET tube SIC7 and SiC MOSFET tube SIC8 form the main bridge arm, and transistor Q2, SiC MOSFET tube SIC9 and SiC MOSFET tube SIC10 form the secondary bridge arm; The specific logical steps of the phase-shifted full-bridge converter operation are as follows: S201: When the high-voltage DC bus voltage output by the PFC module stabilizes, the bus voltage is sampled to confirm that the voltage is within the allowable range, the main control unit is started, the main control unit is initialized, the PWM duty cycle is set to the minimum value, and the soft start mechanism is started; S202: The PWM controller turns on the bridge arms and drives the two bridge arms in a phase-shift control mode; S203: Apply a square wave PWM signal with a frequency of 50kHz-150kHz to the two bridge arms, and change the effective conduction time of the primary side of the transformer by adjusting the phase difference between the two bridge arms. The formula used is: The larger the phase shift angle, the greater the output power, and when the phase shift angle is 0, there is no power output; S204: Utilizes the leakage inductance energy of high-frequency transformer T2 to generate a "voltage swing" after each SiC MOSFET is turned off, reducing Vds to 0 before the next MOSFET is turned on, achieving ZVS, reducing switching losses, and improving efficiency. This is particularly suitable for the high-frequency and high-speed switching characteristics of SiC devices. S205: The primary side of high-frequency transformer T2 converts the PWM-modulated high-frequency DC signal into isolated high-frequency AC. The secondary side, after rectification and filtering, outputs a stable and suitable DC voltage, thus achieving electrical isolation and ensuring the safety of both the driver and the vehicle. S206: The secondary side of high-frequency transformer T2 is equipped with a rectifier circuit, which is smoothed by an LC filter and connected to the battery interface of the electric vehicle. S207: The main control unit collects output voltage and current signals, compares them with target values, calculates errors, and uses a PWM controller to adjust the phase shift angle Δφ to adjust the output; The output filtering and battery interface module includes an LC filter circuit and a charging connector; The output filter and battery interface module are used to filter out high-frequency ripple at the output of the DC-DC converter, providing a smooth, low-noise DC output to communicate with the BMS system of the electric vehicle battery. The LC filter circuit includes a capacitor C6 and a resistor R6, the capacitor C6 and the resistor R6 are connected in parallel, and the charging connector is connected to the electric vehicle battery management system; The control and communication module includes a communication interface, an A / D sampling unit, a PWM controller and a main control unit; The control and communication module is used to control the operation of the entire charging pile, including voltage and current regulation, protection and status monitoring, and to achieve communication with electric vehicles and background systems. The main control unit includes a main control chip U1. Pin 1 of the main control chip U1 is connected to the communication interface, pin 2 of the main control chip U1 is connected to the A / D sampling unit, pin 3 of the main control chip U1 is connected to the PWM controller, and pin 4 of the main control chip U1 is electrically connected to one end of the resistor R6; The auxiliary power supply and heat dissipation module is used to provide stable low-voltage power supply to the main control unit, PWM driver, A / D sampling module, and communication interface. It also uses air cooling to force heat dissipation of SiC devices, rectifier modules, DC-DC modules, output filter and battery interface modules, as well as control and communication modules. It also has a temperature sensor to monitor the temperature of key components in real time. When the temperature exceeds the set threshold, it can trigger power reduction or forced shutdown protection. The safety and protection module is used for overvoltage / undervoltage protection, reverse connection protection, overcurrent protection and short circuit protection; This embodiment uses a Vienna rectifier to efficiently rectify the three-phase AC input and introduces a power factor correction (PFC) mechanism to achieve power factor correction. The introduction of SiC MOSFETs supports high-frequency, high-efficiency switching operations, significantly reducing conduction and switching losses. Furthermore, a phase-shifted full-bridge converter is used to achieve efficient, isolated conversion from the DC bus voltage to the charging output voltage, making it suitable for electric vehicle batteries of different voltage levels. This effectively addresses the low efficiency and low power factor issues of traditional solutions. It should be noted that: when the safety and protection module is specifically protected, it can be protected by combining the overvoltage / undervoltage protection circuit, reverse connection protection circuit, overcurrent protection circuit and short circuit protection circuit in the technology of this field. The principle is the existing technology and will not be elaborated here. The power supply and heat dissipation principles of the auxiliary power supply and the heat dissipation module are all conventional technologies in this field and will not be elaborated here.

[0016] In this embodiment, the three-phase AC power input first enters the rectifier module, which uses a Vienna rectifier three-level rectifier topology to achieve AC-DC conversion. In combination with an active power factor correction (PFC) mechanism, the input voltage and current are detected in real time. PWM control is used to keep the input current and voltage in phase, thereby achieving a near-sinusoidal current input and improving the power factor on the grid side. The rectified high-voltage DC bus voltage is sent to the DC-DC conversion module for voltage conversion and isolation. Phase-shift control technology is used to operate the main power transistor in a zero-voltage (ZVS) state, achieving soft switching and reducing switching losses. The voltage output by the DC-DC conversion module enters the output filter and battery interface module, where an LC filter circuit is used to further suppress high-frequency ripple and stabilize the output waveform. At the same time, the control and communication module collects voltage, current and temperature signals in real time, drives SiC MOSFET devices through the PWM controller, and realizes precise control of the rectification and DC-DC conversion process; During use, the auxiliary power supply and heat dissipation module are used to provide stable low-voltage power supply to the main control unit, PWM driver, A / D sampling module, and communication interface, and perform heat dissipation and temperature monitoring. The safety and protection module provides overvoltage / undervoltage protection, reverse connection protection, overcurrent protection, and short-circuit protection for the entire circuit.

[0017] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A high-efficiency DC charging pile based on SiC devices, characterized in that: It includes rectifier module, DC-DC conversion module, output filter and battery interface module, control and communication module, auxiliary power supply and heat dissipation module, and safety and protection module; The rectifier module includes a Vienna rectifier and a PFC module; The DC-DC conversion module includes a DC-DC conversion unit and a phase-shifted full-bridge converter; The output filtering and battery interface module includes an LC filtering circuit and a charging connector; The control and communication module includes a communication interface, an A / D sampling unit, a PWM controller and a main control unit.

2. A high-efficiency DC charging pile based on SiC devices according to claim 1, characterized in that: The Vienna rectifier is used to convert the three-phase AC power supply into a DC voltage and perform power factor correction through the PFC module to ensure that the grid-side current is a sine wave with a high power factor; The Vienna rectifier includes SiC MOSFET tubes SIC1, SiC MOSFET tubes SIC2, SiC MOSFET tubes SIC3 and SiC MOSFET tubes SIC4, wherein pin 2 of SiC MOSFET tube SIC1 is electrically connected to one end of capacitor C2, the other end of capacitor C2 is electrically connected to pin 1 of SiC MOSFET tube SIC2, pin 1 of SiC MOSFET tube SIC1 is electrically connected to pin 1 of SiC MOSFET tube SIC3, pin 2 of SiC MOSFET tube SIC3 is electrically connected to pin 1 of SiC MOSFET tube SIC4, pin 2 of SiC MOSFET tube SIC2 and pin 2 of SiC MOSFET tube SIC4 are both grounded, pin 2 of SiC MOSFET tube SIC1 is also electrically connected to one end of inductor L1, one end of inductor L1 and pin 2 of SiC MOSFET tube SIC1 are both electrically connected to one end of capacitor C1, the other end of capacitor C1 is grounded, and SiC Pin 2 of MOSFET tube SIC3 is electrically connected to one end of capacitor C3, the other end of capacitor C3 is electrically connected to one end of resistor R1, the other end of resistor R1 is electrically connected to one end of inductor L2, and pin 1 of SiC MOSFET tube SIC4 is electrically connected to one end of resistor R2, the other end of resistor R2 is electrically connected to one end of inductor L3.

3. A high-efficiency DC charging pile based on SiC devices according to claim 2, characterized in that: The DC-DC conversion unit includes a high-frequency transformer T1. Pin 1 of the high-frequency transformer T1 is electrically connected to one end of a resistor R3. The other end of the resistor R3 is electrically connected to pin 1 of a SiC MOSFET tube SIC5 and the cathode of a diode D1. Pin 2 of the SiC MOSFET tube SIC5 is electrically connected to pin 1 of a SiC MOSFET tube SIC6. The anode of the diode D1 is electrically connected to the cathode of a diode D2. The anode of the diode D2 is electrically connected to pin 2 of the SiC MOSFET tube SIC6. Pin 2 of the high-frequency transformer T1 is electrically connected to one end of a resistor R4. The other end of the resistor R4 is electrically connected to pin 2 of the SiC MOSFET tube SIC6. Pin 3 of the high-frequency transformer T1 is electrically connected to one end of a capacitor C4 and one end of a capacitor C5. Pin 4 of the high-frequency transformer T1 is electrically connected to one end of a resistor R5. The other end of the resistor R5, the other end of the capacitor C4, and the other end of the capacitor C5 are all grounded.

4. A high-efficiency DC charging pile based on SiC devices according to claim 1, characterized in that: The output filter and battery interface module is used to filter out high-frequency ripples at the output of the DC-DC converter, providing a smooth, low-noise DC output to communicate with the BMS system of the electric vehicle battery; The LC filter circuit includes a capacitor C6 and a resistor R6, the capacitor C6 and the resistor R6 are connected in parallel, and the charging connector is connected to the electric vehicle battery management system; The phase-shifted full-bridge converter is used to convert the high-voltage DC bus voltage into a DC voltage suitable for charging the electric vehicle battery, supports soft switching, and achieves electrical isolation between the grid and the vehicle through a high-frequency transformer; The phase-shift full-bridge converter includes a transistor Q1 and a transistor Q2. Pins 1 and 2 of the transistor Q1 are connected in parallel with a diode D3. Pins 1 and 2 of the transistor Q2 are connected in parallel with a diode D4. The anode of the diode D3 is electrically connected to the cathode of the diode D4. Pin 1 of the transistor Q1 is also electrically connected to pin 1 of the SiC MOSFET tube SIC7, pin 1 of the SiC MOSFET tube SIC9, and pin 1 of the high-frequency transformer T2. Pin 2 of the SiC MOSFET tube SIC7 is electrically connected to pin 1 of the SiC MOSFET tube SIC8 and one end of the capacitor C7. The other end of the capacitor C7 is electrically connected to pin 2 of the SiC MOSFET tube SIC9. Pin 2 of the SiC MOSFET tube SIC9 is electrically connected to pin 1 of the SiC MOSFET tube SIC10. Pin 2 of the SiC MOSFET tube SIC10 and the SiC Pin 2 of the MOSFET tube SIC8 and pin 2 of the transistor Q2 are both electrically connected to pin 2 of the high-frequency transformer T2, and pins 4 and 3 of the high-frequency transformer T2 are connected in parallel with the capacitor C6; The transistor Q1, SiC MOSFET tube SIC7 and SiC MOSFET tube SIC8 form a main bridge arm, and the transistor Q2, SiC MOSFET tube SIC9 and SiC MOSFET tube SIC10 form a secondary bridge arm.

5. A high-efficiency DC charging pile based on SiC devices according to claim 4, characterized in that: The control and communication module is used to control the operation of the entire charging pile, including voltage, current regulation, protection and status monitoring, and to realize communication with electric vehicles and background systems. The main control unit includes a main control chip U1, pin 1 of the main control chip U1 is connected to the communication interface, pin 2 of the main control chip U1 is connected to the A / D sampling unit, pin 3 of the main control chip U1 is connected to the PWM controller, and pin 4 of the main control chip U1 is electrically connected to one end of the resistor R6.

6. A high-efficiency DC charging pile based on SiC devices according to claim 2, characterized in that: The specific steps for power factor correction through the PFC module are as follows: S101: Real-time sampling of the three-phase input (L1, L2, L3), input voltage V in (t), input current I in (t); S102: Generate target current waveform: Sampled input voltage V in (t) is normalized and used as the current reference waveform using the following formula: , where P out is the output power, ensuring I ref (t) vs. V in (t) Same phase, same frequency, and proportional; S103: Perform error calculation to obtain the current current error e(t). The formula used is: e(t)=I ref (t)-I in (t); S104: The error e(t) is sent to the PWM controller, and the output is the voltage control variable u(t), which is used to adjust the PWM duty cycle. The formula used is: ; S105: Using the control output u(t), the switching duty cycle of the SiC MOSFET tubes SIC1 to SiC MOSFET tubes SIC4 is controlled, and a high-frequency modulation method is used to accurately modulate the input current waveform to match the voltage waveform; S106: As the current inner loop is closed, the input current waveform approaches the target waveform I ref (t), and the input current and voltage waveforms have the same frequency and phase, the waveform is close to sinusoidal, and the power factor PF reaches 1; S107: Detect input voltage drop and current overcurrent in real time. Once an abnormality occurs, turn off the PWM output and execute a soft shutdown or fault protection process.

7. The high-efficiency DC charging pile based on SiC devices according to claim 4, characterized in that: The specific logical steps of the phase-shifted full-bridge converter operation are as follows: S201: When the high-voltage DC bus voltage output by the PFC module stabilizes, the bus voltage is sampled to confirm that the voltage is within the allowable range, the main control unit is started, the main control unit is initialized, the PWM duty cycle is set to the minimum value, and the soft start mechanism is started; S202: The PWM controller turns on the bridge arms and drives the two bridge arms in a phase-shift control mode; S203: Apply a square wave PWM signal with a frequency of 50kHz-150kHz to the two bridge arms, and change the effective conduction time of the primary side of the transformer by adjusting the phase difference between the two bridge arms. The formula used is: , the larger the phase shift angle, the greater the output power, and when the phase shift angle is 0, there is no power output; S204: Utilizes the leakage inductance energy of high-frequency transformer T2 to generate a "voltage swing" after each SiC MOSFET is turned off, reducing Vds to 0 before the next MOSFET is turned on, achieving ZVS, reducing switching losses, and improving efficiency. This is particularly suitable for the high-frequency and high-speed switching characteristics of SiC devices. S205: The primary side of high-frequency transformer T2 converts the PWM-modulated high-frequency DC signal into isolated high-frequency AC. The secondary side, after rectification and filtering, outputs a stable and suitable DC voltage, thus achieving electrical isolation and ensuring the safety of both the driver and the vehicle. S206: The secondary side of high-frequency transformer T2 is equipped with a rectifier circuit, which is smoothed by an LC filter and connected to the battery interface of the electric vehicle. S207: The main control unit collects output voltage and current signals, compares them with target values, calculates errors, and uses a PWM controller to adjust the phase shift angle Δφ to adjust the output.

8. The high-efficiency DC charging pile based on SiC devices according to claim 2, characterized in that: The specific logical steps of the Vienna rectifier are as follows: S301: A three-phase AC power source is connected to the input of the Vienna rectifier, connected to inductors L1, L2, and L3, and a boost power unit is connected to each phase. S302: The control unit starts and drives each SiC MOSFET in a continuous current mode, so that each SiC MOSFET is turned on in a corresponding phase sequence; S303: The three-phase input current flows through the corresponding inductor, and the SiC MOSFET is turned on to form a boost path. At the same time, the PWM controller adjusts the duty cycle to achieve constant output voltage and sinusoidal input current. S304: Capacitors C1, C2, and C3 form a DC bus center potential clamping network to maintain symmetrical voltage division between the two capacitors on the DC side, ensuring output stability. Simultaneously, the PWM controller monitors midpoint voltage deviation in real time and adjusts device conduction to maintain voltage balance. S305: Resistors R1 and R2, inductors L2 and L3 form a sampling current channel. The PWM controller performs closed-loop regulation on the PWM of each phase according to the sampling value to achieve sinusoidalization of the grid current and harmonic suppression, and output a stable voltage.

9. The high-efficiency DC charging pile based on SiC devices according to claim 1, characterized in that: The auxiliary power supply and heat dissipation module is used to provide stable low-voltage power supply to the main control unit, PWM driver, A / D sampling module, and communication interface, and forcedly dissipate heat for SiC devices, rectifier modules, DC-DC modules, output filter and battery interface modules, and control and communication modules through air cooling. At the same time, it is equipped with a temperature sensor to monitor the temperature of key components in real time. When the temperature exceeds the set threshold, it can trigger power reduction or forced shutdown protection; The safety and protection module is used for overvoltage / undervoltage protection, reverse connection protection, overcurrent protection and short circuit protection.

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