Digital control system of energy storage converter based on SiC power device

Abstract

The invention provides an energy storage converter digital control system based on a SiC power device. The energy storage converter digital control system comprises an energy storage converter, an MCU control system and a control circuit. The control circuit comprises an ultrahigh frequency switch driving module, a sampling feedback module, a comprehensive protection module and a system communication module; the energy storage converter is based on a SiC power device; the energy storage converter comprises a DC / AC main circuit, a DC / DC main circuit and a battery pack module. The sampling feedback module collects current and voltage values of the battery pack module and current and voltage values of a direct current bus between the DC / DC main circuit and the DC / AC main circuit. And the MCU control system adopts a PID algorithm to adjust and output a control signal according to the collected current and voltage values, and the working states of the SiC power devices of the energy storage converter are respectively controlled through the ultrahigh frequency switch driving module. The control system integrates ultrahigh frequency switch driving capability, excellent equipment protection performance and full digital control, and has good control precision and response speed.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage equipment, and more specifically, to a digital control system for an energy storage converter based on SiC power devices. Background Art

[0002] As one of the core components of the energy storage system, the energy storage inverter undertakes the key task of power conversion. The high-quality development of new energy in the new era has put forward high-efficiency, advanced and energy-saving requirements for the energy conversion efficiency of the energy storage inverter.

[0003] Almost all existing energy storage converters use Si-based power devices, and their switching performance is close to the theoretical limit determined by their material properties. Relying on power devices to further increase the operating frequency of energy storage converters, reduce temperature rise, and improve losses is extremely limited, which seriously restricts the improvement of power density and energy efficiency of energy storage converters. The use of SiC power devices (wide bandgap power devices) can break through the bottleneck of the power density and efficiency of existing energy storage converters that are difficult to further improve due to the constraints of Si-based power devices. However, energy storage converters based on SiC power devices have the characteristics of high-frequency and high-voltage working conditions and fast response speeds. There are many interference factors and it is difficult to control. High-performance digital control systems are required for refined control. Summary of the invention

[0004] In order to overcome the shortcomings and deficiencies in the prior art, the purpose of the present invention is to provide a digital control system for an energy storage converter based on SiC power devices; the control system integrates ultra-high frequency switch driving capability, excellent equipment protection performance, and fully digital control and has good control accuracy and response speed.

[0005] In order to achieve the above object, the present invention is implemented by the following technical solutions: a digital control system of an energy storage converter based on SiC power devices, including an energy storage converter, an MCU control system and a control circuit; The control circuit includes an ultra-high frequency switch driving module, a sampling feedback module, a comprehensive protection module for implementing protection when a fault occurs, and a system communication module for communicating with the EMS system and the BMS system; The energy storage converter refers to an energy storage converter based on SiC power devices; the energy storage converter includes a DC / AC main circuit for converting current between direct current and alternating current, two or more DC / DC main circuits for transforming and isolating direct current, and a battery pack module; the DC / AC main circuit is connected to the DC / DC main circuit through a DC bus; each DC / DC main circuit is connected to the battery pack module respectively; The sampling feedback module respectively collects the current and voltage values ​​of the battery pack module, as well as the current and voltage values ​​of the DC bus between the DC / DC main circuit and the DC / AC main circuit, and sends the collected current and voltage values ​​to the MCU control system; the MCU control system uses the PID algorithm to adjust the output control signal according to the collected current and voltage values, and controls the working state of the SiC power device of the energy storage converter through the ultra-high frequency switch drive module.

[0006] Preferably, each DC / DC main circuit includes a SiC full-bridge primary module, a high-frequency transformer T201 and a SiC full-bridge secondary module connected in sequence; wherein the SiC full-bridge primary module is connected to the DC / AC main circuit via a DC bus; the SiC full-bridge primary module and the SiC full-bridge secondary module respectively adopt a full-bridge topology structure formed by SiC MOSFET; Bidirectional energy transfer is achieved between the three-phase AC grid and the battery module through the connected DC / AC main circuit and DC / DC main circuit; When energy is transferred from the three-phase AC grid to the battery pack module, the DC bus between the SiC full-bridge primary module and the DC / AC main circuit is the input side, the battery pack module is the output side, the SiC full-bridge primary module forms an inverter circuit, and the SiC full-bridge secondary module forms a rectifier circuit; when energy is transferred from the battery pack module to the three-phase AC grid, the battery pack module is the input side, the DC bus between the SiC full-bridge primary module and the DC / AC main circuit is the output side, the SiC full-bridge secondary module forms an inverter circuit, and the SiC full-bridge primary module forms a rectifier circuit; For the inverter circuit, the ultra-high frequency switch driver module outputs two complementary PWM signals with dead zones to control the two SiC MOSFETs at the diagonal of the inverter circuit to turn on or off at high frequency at the same time, converting DC power into high-frequency AC power. For the rectification circuit, the ultra-high frequency switch driving module turns off all SiC MOSFETs; the high-frequency AC is rectified through the rectification circuit formed by the body diode of SiC MOSFET.

[0007] Preferably, the MCU control system uses a PID algorithm to adjust the output control signal according to the collected current and voltage values, which means: according to the collected measured current value and measured voltage value on the output side; performing difference operations with the preset current setting value and voltage setting value of the output side, respectively, and performing PID operations on several average differences to obtain current fluctuation values ​​and voltage fluctuation values; according to the current fluctuation value and voltage fluctuation value, changing the on and off time of the SiC MOSFET of the inverter circuit to achieve duty cycle adjustment, so that the current value and voltage value on the output side are close to the current setting value and voltage setting value, respectively.

[0008] Preferably, the SiC full-bridge primary module, the SiC MOSFET includes SiC MOSFETs M201 to M204; the SiC full-bridge primary module also includes a capacitor C200; After SiC MOSFET M201 and SiC MOSFET M203 are connected in series, they are connected in parallel to the DC / AC main circuit through the DC bus together with the circuit formed by SiC MOSFET M202 and SiC MOSFET M204 in series; the connection point of SiC MOSFET M201 and SiC MOSFET M203 is connected to the primary first input terminal of the high-frequency transformer T201 through the capacitor C200; the connection point of SiC MOSFET M202 and SiC MOSFET M204 is connected to the primary second input terminal of the high-frequency transformer T201; The SiC full-bridge secondary module, the SiC MOSFET includes SiC MOSFETs M205 to M208; the SiC full-bridge secondary module also includes a capacitor C209; After SiC MOSFET M205 and SiC MOSFET M207 are connected in series, they are connected in parallel to the battery pack module together with a circuit formed by SiC MOSFET M206 and SiC MOSFET M208 in series; the connection between SiC MOSFET M205 and SiC MOSFET M207 is connected to the secondary first output terminal of the high-frequency transformer T201 through capacitor C209; the connection between SiC MOSFET M206 and SiC MOSFET M208 is connected to the secondary second output terminal of the high-frequency transformer T201.

[0009] Preferably, the SiC full-bridge secondary module further includes an inductor L201 and an inductor L202; the connection point of SiC MOSFET M201 and SiC MOSFET M203 is connected to the primary first input terminal of the high-frequency transformer T201 through a capacitor C200 and an inductor L201 connected in series; the inductor L202 is connected in parallel to the primary of the high-frequency transformer T201; The SiC full-bridge secondary module also includes an inductor L203; a circuit formed by connecting SiC MOSFET M205 and SiCMOSFET M207 in series, which is connected in parallel with a circuit formed by connecting SiC MOSFET M206 and SiCMOSFET M208 in series, and then connected in series with the high-frequency inductor L203, and then connected in parallel to the battery pack module. This method uses LLC series resonant soft switching technology to avoid the sharp increase in switching losses caused by increasing the inverter frequency to ultra-high frequency, greatly improving the energy efficiency of the energy storage converter.

[0010] Preferably, the SiC full-bridge primary module further includes capacitors C201-C204 and resistors R201-R204; capacitor C201 and resistor R201 are connected in series and then connected in parallel to SiC MOSFET M201; capacitor C202 and resistor R202 are connected in series and then connected in parallel to SiC MOSFET M202; capacitor C203 and resistor R203 are connected in series and then connected in parallel to SiC MOSFET M203; capacitor C204 and resistor R204 are connected in series and then connected in parallel to SiC MOSFET M204; The SiC full-bridge secondary module also includes capacitors C205-C208 and resistors R205-R208; capacitor C205 and resistor R205 are connected in series and then connected in parallel to SiC MOSFET M205; capacitor C206 and resistor R206 are connected in series and then connected in parallel to SiC MOSFET M206; capacitor C207 and resistor R207 are connected in series and then connected in parallel to SiC MOSFET M207; capacitor C208 and resistor R208 are connected in series and then connected in parallel to SiC MOSFET M208.

[0011] Preferably, the sampling feedback module includes a current sampling circuit and a voltage sampling circuit; The current sampling circuit includes a Hall current sensor, an integrated differential amplifier circuit 1 composed of a differential amplifier 1 and a peripheral circuit of the differential amplifier 1, a low-pass filter circuit composed of an operational amplifier 1 and a peripheral circuit of the operational amplifier 1, and an absolute value circuit 1 composed of an operational amplifier 2 and a peripheral circuit of the operational amplifier 2; The voltage sampling circuit includes a Hall voltage sensor, an integrated differential amplifier circuit 2 consisting of a differential amplifier 2 and a peripheral circuit of the differential amplifier 2, and an absolute value circuit 2 consisting of an operational amplifier 3 and a peripheral circuit of the operational amplifier 3.

[0012] Preferably, the ultra-high frequency switch driving module includes a PWM signal isolation amplifier circuit and an ultra-high frequency switch driving circuit; The PWM signal isolation amplifier circuit comprises an optocoupler isolation circuit 1 composed of a high-speed optocoupler 1; The ultra-high frequency switch driving circuit includes a power supply circuit composed of a DC-DC power supply and a DC-DC power supply peripheral circuit, a magnetic isolation gate driving integrated circuit composed of an isolation driving chip and an isolation driving chip peripheral circuit, and a gate driving protection circuit.

[0013] Preferably, the comprehensive protection module includes an overcurrent detection protection circuit and an undervoltage and overvoltage protection circuit; the overcurrent detection protection circuit includes a dual voltage comparator 1 and an optocoupler isolation circuit 2 composed of a high-speed optocoupler 2; the undervoltage and overvoltage protection circuit includes two dual voltage comparators 2 and a resistor voltage divider circuit.

[0014] Preferably, the system communication module includes a CAN isolation communication circuit and an RS485 isolation communication circuit; the CAN isolation communication circuit includes an optocoupler isolation circuit three composed of a high-speed optocoupler three and a CAN signal generating circuit composed of a CAN transceiver; the RS485 isolation communication circuit includes an optocoupler isolation circuit four composed of a high-speed optocoupler four and an RS485 signal generating circuit composed of a 485 converter.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The present invention not only has excellent control accuracy and instantaneous response capability, but also can effectively cope with complex working conditions and ensure stable operation of the system. Supported by this digital control system, ultra-high frequency inverter technology can significantly improve the dynamic characteristics of the power hardware platform of the energy storage converter, giving full play to the advantages of the energy storage converter based on SiC power devices; 2. The present invention is applicable to energy storage converters using SiC devices as main power devices, and integrates advanced drive control technology, which can effectively prevent SiC power devices from being damaged, suppress the problems of excessive transient voltage and transient current and electromagnetic interference during the driving process of SiC power devices, prevent false triggering caused by voltage spikes, and accurately manage the switching action of SiC devices; 3. The present invention has a more excellent equipment protection capability. It integrates a variety of advanced fault detection and protection circuits, which can comprehensively monitor the key faults that may occur in various working links of the energy storage converter. After detecting a fault, the MCU control system will shut down the primary and secondary inverter drive circuits to prevent the fault from spreading further. The comprehensive protection strategy improves the stability and durability of the energy storage converter. 4. The present invention adopts high-speed and high-precision fully digital control technology, which has higher control accuracy and faster response speed, realizes closed-loop control, and is easier to realize refined design and control of energy storage converters, thereby improving power quality and power conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the overall system block diagram of the digital control system of the energy storage converter based on SiC power devices of the present invention; Figure 2 It is a schematic diagram of an energy storage converter of a digital control system of an energy storage converter based on SiC power devices of the present invention; Figure 3 It is a schematic diagram of a PWM signal isolation amplifier circuit of a digital control system of an energy storage converter based on SiC power devices of the present invention; Figure 4 It is a schematic diagram of an ultra-high frequency switch driving circuit of a SiC power device of a digital control system of an energy storage converter based on SiC power devices of the present invention; Figure 5 It is a schematic diagram of a current sampling circuit of a digital control system of an energy storage converter based on SiC power devices of the present invention; Figure 6 It is a schematic diagram of a voltage sampling circuit of a digital control system of an energy storage converter based on SiC power devices of the present invention; Figure 7 It is a schematic diagram of an overcurrent detection protection circuit of a digital control system of an energy storage converter based on SiC power devices of the present invention; Figure 8 It is a schematic diagram of an undervoltage and overvoltage protection circuit of a digital control system of an energy storage converter based on SiC power devices of the present invention; Fig. 9 It is a schematic diagram of the RS485 isolation communication circuit of the digital control system of the energy storage converter based on SiC power devices of the present invention; Fig.10 It is a schematic diagram of a CAN isolation communication circuit of a digital control system of an energy storage converter based on SiC power devices of the present invention. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0018] Embodiment 1 This embodiment is a digital control system for an energy storage converter based on SiC power devices, and its overall block diagram is as follows: Figure 1 As shown, it includes an energy storage converter, an MCU control system and a control circuit.

[0019] The control circuit includes an ultra-high frequency switch driving module, a sampling feedback module, an integrated protection module for implementing protection when a fault occurs, and a system communication module for communicating with the EMS system and the BMS system.

[0020] like Figure 2 As shown, the energy storage converter refers to an energy storage converter based on SiC power devices; the energy storage converter includes a DC / AC main circuit for converting current between direct current and alternating current, two or more DC / DC main circuits for transforming and isolating direct current, and a battery pack module. In this embodiment, the DC / DC main circuit is two-way, and in actual applications, the DC / DC main circuit can be three-way, four-way, five-way, or even more.

[0021] The DC / AC main circuit includes a filter module, an inductor energy storage module, an inverter rectifier module, a filter voltage regulator module and a DC bus connected in sequence. Specifically, in the DC / AC main circuit, the filter module includes inductors L104~L106 and capacitors C101~C103; the inductor energy storage module includes inductors L101~L103. The inverter rectifier module adopts a three-phase full-bridge rectifier topology structure formed by SiC IGBT; the inverter rectifier module includes SiC IGBT M101~M106, diodes D101~D106; the filter voltage regulator module includes filter voltage regulator capacitors C104~C107.

[0022] Each DC / DC main circuit includes a SiC full-bridge primary module, a high-frequency transformer T201 and a SiC full-bridge secondary module connected in sequence; wherein, the SiC full-bridge primary module is connected to the DC / AC main circuit through a DC bus; the SiC full-bridge primary module and the SiC full-bridge secondary module respectively adopt a full-bridge topology structure formed by SiC MOSFET.

[0023] Specifically, the SiC full-bridge primary module, the SiC MOSFET includes SiC MOSFETs M201 to M204; the SiC full-bridge primary module also includes a capacitor C200, capacitors C201 to C204 and resistors R201 to R204; After SiC MOSFET M201 and SiC MOSFET M203 are connected in series, they are connected in parallel to the DC / AC main circuit through the DC bus together with the circuit formed by SiC MOSFET M202 and SiC MOSFET M204 in series; the connection point of SiC MOSFET M201 and SiC MOSFET M203 is connected to the primary first input terminal of the high-frequency transformer T201 through the capacitor C200; the connection point of SiC MOSFET M202 and SiC MOSFET M204 is connected to the primary second input terminal of the high-frequency transformer T201; the capacitor C201 and the resistor R201 are connected in series and then connected in parallel to the SiC MOSFET M201; the capacitor C202 and the resistor R202 are connected in series and then connected in parallel to the SiC MOSFET M202; the capacitor C203 and the resistor R203 are connected in series and then connected in parallel to the SiC MOSFET M203; the capacitor C204 and the resistor R204 are connected in series and then connected in parallel to the SiC MOSFET M204.

[0024] The SiC full-bridge secondary module, the SiC MOSFET includes SiC MOSFETs M205 to M208; the SiC full-bridge secondary module also includes a capacitor C209, capacitors C205 to C208 and resistors R205 to R208; After SiC MOSFET M205 and SiC MOSFET M207 are connected in series, they are connected in parallel to the battery pack module together with the circuit formed by SiC MOSFET M206 and SiC MOSFET M208 in series; the connection point of SiC MOSFET M205 and SiC MOSFET M207 is connected to the secondary first output terminal of the high-frequency transformer T201 through capacitor C209; the connection point of SiC MOSFET M206 and SiC MOSFET M208 is connected to the secondary second output terminal of the high-frequency transformer T201; capacitor C205 and resistor R205 are connected in series and then connected in parallel to SiC MOSFET M205; capacitor C206 and resistor R206 are connected in series and then connected in parallel to SiC MOSFET M206; capacitor C207 and resistor R207 are connected in series and then connected in parallel to SiC MOSFET M207; capacitor C208 and resistor R208 are connected in series and then connected in parallel to SiC MOSFET M208.

[0025] The three-phase AC grid and the battery pack module are bidirectionally connected through the connected DC / AC main circuit and DC / DC main circuit; the SiC power devices in the energy storage inverter are quickly turned on and off according to the preset timing to realize the energy transfer of industrial frequency AC-DC-high frequency AC-DC from the three-phase AC grid to the battery pack module, or the energy transfer of DC-high frequency AC-DC-industrial frequency AC from the battery pack module to the three-phase AC grid.

[0026] When energy is transferred from the three-phase AC grid to the battery pack module, the DC bus between the SiC full-bridge primary module and the DC / AC main circuit is the input side, the battery pack module is the output side, the SiC full-bridge primary module forms an inverter circuit, and the SiC full-bridge secondary module forms a rectifier circuit; when energy is transferred from the battery pack module to the three-phase AC grid, the battery pack module is the input side, the DC bus between the SiC full-bridge primary module and the DC / AC main circuit is the output side, the SiC full-bridge secondary module forms an inverter circuit, and the SiC full-bridge primary module forms a rectifier circuit; For the inverter circuit, the ultra-high frequency switch driver module outputs two complementary PWM signals with dead zones to control the two SiC MOSFETs at the diagonal of the inverter circuit to turn on or off at high frequency at the same time, converting DC power into high-frequency AC power. For the rectification circuit, the ultra-high frequency switch driving module turns off all SiC MOSFETs; the high-frequency AC is rectified through the rectification circuit formed by the body diode of SiC MOSFET.

[0027] The MCU control system uses the PID algorithm to adjust the output control signal according to the collected current and voltage values, and controls the working status of the SiC full-bridge primary module and the SiC full-bridge secondary module respectively through the ultra-high frequency switch drive module. Specifically, according to the measured current value and measured voltage value collected on the output side; the difference operation is performed with the preset current setting value and voltage setting value of the output side respectively, and the average difference is PID operated for several times to obtain the current fluctuation value and voltage fluctuation value; according to the current fluctuation value and voltage fluctuation value, the on and off time of the SiC MOSFET of the inverter circuit is changed to realize the duty cycle adjustment, so that the current value and voltage value of the output side are close to the current setting value and voltage setting value respectively.

[0028] The control circuit of the present invention takes the MCU control system as the core, and realizes the functions of energy storage converter process task control, hardware circuit switch control and electrical signal feedback regulation, equipment protection, human-computer communication, etc. in combination with the peripheral circuit. The early PWM signal output by the MCU control system enters the ultra-high frequency switch drive circuit through the signal isolation amplifier circuit, and finally outputs the PWM signal that drives the SiC power device, realizes the drive control of the SiC power device in the DC / AC main circuit and the DC / DC main circuit of the energy storage converter, and regulates the output characteristics of the energy storage converter. The sampling feedback module mainly includes current and voltage sampling circuits, and the electrical signal fed back by the sampling is input into the ADC module for digital filtering and PID control processing. The comprehensive protection module includes an overcurrent detection protection circuit and an undervoltage and overvoltage protection circuit. When an overcurrent fault, an over-undervoltage of the power grid, a three-phase phase loss, etc. occur, the fault signal is sent to the GPIO pin of the MCU control system. The control system jumps out of the workflow program through the GPIO interrupt, stops the PWM output, closes the primary and secondary inverter drive circuits, and sends the fault signal to the digital interactive interface, prompts the fault and displays the fault type. The system communication module is mainly used for communication between the energy storage inverter and the EMS system and BMS system. It is composed of CAN and RS485 isolated communication circuits. The digital interactive interface is used to adjust the inverter parameters and display the output current, voltage and charge and discharge status in real time.

[0029] The ultra-high frequency switch driving module includes a PWM signal isolation amplifier circuit and an ultra-high frequency switch driving circuit. Figure 3As shown, the PWM signal isolation amplifier circuit includes an optocoupler isolation circuit 1 composed of a high-speed optocoupler 1. The task of the PWM signal isolation amplifier circuit is to improve the load capacity of the PWM signal and isolate it from the driver circuit board. Since the internal GPIO output load capacity of the MCU chip is limited, in order to reduce the output current of the MCU chip and avoid external current injection, the GPIO pin of the MCU chip is directly connected to the battery pack charge and discharge switching circuit; the battery pack charge and discharge switching circuit controls the battery pack module to cut in and out of the circuit. When the battery pack module is charged to 100%, the GPIO sends a signal to the relay to cut the battery pack module out of the circuit to avoid overcharging, while waiting for the discharge signal, and then cut the battery pack module into the circuit when the discharge starts; the back stage is isolated and output through a high-speed optocoupler to prevent the electromagnetic interference of the gate drive circuit from coupling to the digital control circuit, which can protect the power control system and improve the anti-interference ability of the system, and ensure the reliability and stability of the power supply.

[0030] like Figure 4 As shown, the ultra-high frequency switch drive circuit includes a power supply circuit composed of a DC-DC power supply and a DC-DC power supply peripheral circuit, a magnetic isolation gate drive integrated circuit composed of an isolation drive chip and an isolation drive chip peripheral circuit, and a gate drive protection circuit. In the power supply circuit, the secondary side voltage is provided by an integrated DC / DC isolated from the primary side power supply to provide a drive voltage for the PWM signal; the PWM signal output by the MCU chip is amplified and magnetically isolated through the PWM output circuit, and then output to the Miller clamp circuit and the short-circuit protection circuit, and finally output to the SiC power device; the CLAMP pin in the Miller clamp circuit inputs the gate voltage of the SiC power device into the logic clamp circuit after logic comparison and discharges the crosstalk charge; in the short-circuit protection circuit, the drain of the SiC power device is connected to the desaturation detection circuit through the fast recovery diode D2 to detect the drain voltage, and when overcurrent occurs, the gate outputs a negative voltage through the logic circuit to softly shut down the SiC power device to prevent device damage; in addition, the fault signal in the PWM output circuit can be output to the MCU chip through pull-up to realize software monitoring, and the Reset pin level can be controlled to reset and exit the protection state.

[0031] The sampling feedback module collects the current and voltage values ​​of the battery pack module and the current and voltage values ​​of the DC bus between the SiC full-bridge primary module and the DC / AC main circuit, and sends the collected current and voltage values ​​to the MCU control system. The sampling feedback module includes a current sampling circuit and a voltage sampling circuit.

[0032] like Figure 5As shown, the current sampling circuit includes a Hall current sensor, an integrated differential amplifier circuit 1 composed of a differential amplifier 1 and a peripheral circuit of the differential amplifier 1, a low-pass filter circuit composed of an operational amplifier 1 and a peripheral circuit of the operational amplifier 1, and an absolute value circuit 1 composed of an operational amplifier 2 and a peripheral circuit of the operational amplifier 2.

[0033] The current sampling circuit uses a Hall current sensor, which converts the sensed current value into a low-amplitude voltage through the Hall effect and outputs it. The output voltage is processed by a sampling feedback circuit: the signal is divided by R501 and R505 and then transmitted to an integrated differential amplifier circuit with a high common-mode rejection ratio to improve the load capacity of the subsequent stage and reduce the influence of temperature drift and power supply common-mode interference; a unit-gain KRC low-pass filter circuit is designed for the subsequent stage. The filter has an attenuation slope of -40dB and has a good filtering effect; due to the bidirectional energy transfer, in order to prevent negative pressure from affecting the operation of the ADC, an absolute value circuit is designed at the output end to ensure that the feedback signal received by the ADC is between 0-3.3V, ensuring the validity of the signal, and finally input to the ADC pin of the MCU chip through a voltage regulator tube and a filter capacitor.

[0034] like Figure 6 As shown, the voltage sampling circuit includes a Hall voltage sensor, an integrated differential amplifier circuit 2 consisting of a differential amplifier 2 and a peripheral circuit of the differential amplifier 2, a second-order low-pass filter circuit, and an absolute value circuit 2 consisting of an operational amplifier 3 and a peripheral circuit of the operational amplifier 3.

[0035] For voltage sampling of the DC bus and battery pack of the energy storage inverter, the Hall voltage sensor senses the power supply output voltage as a low-amplitude current for output, and converts the input current into a low-amplitude voltage output through the kilo-ohm precision resistor R601. Similar to the current feedback sampling circuit, the signal must pass through the integrated differential amplifier circuit 2, the second-order low-pass filter circuit, and the absolute value circuit 2 before entering the ADC pin of the MCU.

[0036] The comprehensive protection module includes overcurrent detection protection circuit and undervoltage and overvoltage protection circuit. Figure 7 As shown, the overcurrent detection protection circuit includes a dual voltage comparator 1 and an optocoupler isolation circuit 2 composed of a high-speed optocoupler 2. The sampling mutual inductance coil converts the output current of the power supply through the corresponding conversion ratio and connects it to the P1 interface. After passing through the rectifier circuit, it is converted into a DC voltage signal by R701 and input to the reverse end of the dual voltage comparator. The same-direction end of the inverter is connected to the reference voltage V ref , this circuit can be adjusted V refChange the overcurrent judgment threshold of the overcurrent detection protection circuit. When the current exceeds the set protection threshold, the comparator outputs a low level, followed by the optocoupler U703 turning on, the optocoupler U704 turning on and interlocking with U703, and then the high-speed optocoupler turning on, outputting a high level, the fault indicator lights up and inputs the signal to the MCU chip GPIO, stopping the system operation through an interrupt.

[0037] like Figure 8 As shown, the undervoltage and overvoltage protection circuit includes two dual voltage comparators and a resistor voltage divider circuit. The 15V DC control power generated by the power module of the power control system is input to different comparator input terminals after voltage division and connected to the corresponding reference voltage set. V ref For comparison, when the grid voltage fluctuation exceeds the set protection threshold (±10%), a fault signal is generated to the MCU chip to prevent the power supply from outputting power under unstable voltage conditions.

[0038] The system communication module includes CAN isolation communication circuit and RS485 isolation communication circuit. Fig. 9 As shown, the RS485 isolation communication circuit includes an optocoupler isolation circuit 4 composed of a high-speed optocoupler 4 and an RS485 signal generation circuit composed of a 485 converter. The RS485 isolation communication circuit converts the TTL level output by the MCU chip into a differential signal (or reverse conversion) that can be transmitted on the 485 bus through a conversion circuit. The RE, DE, and RE / DE pins of the MCU chip are connected to the 485 converter after being isolated by a high-speed optocoupler. After converting the TTL level signal into a differential signal, it is carried on the 485 bus after passing through a terminal resistor and a filter capacitor. D1 is a TVS diode module, which can be used to suppress surge impact on the 485 bus and protect the circuit and chip.

[0039] like Fig.10 As shown, the CAN isolation communication circuit includes an optocoupler isolation circuit composed of a high-speed optocoupler and a CAN signal generation circuit composed of a CAN transceiver. The MCU chip sends or receives TTL level signals through the relevant GPIO pins, and isolates the pins of the MCU chip from the CAN transceiver through high-speed optocouplers. The CAN transceiver converts the TTL level sent by the MCU chip into a differential signal transmitted by CANL and CANH, and carries the node on the CAN bus to communicate with external devices.

[0040] Embodiment 2 The present embodiment is a digital control system for an energy storage converter based on SiC power devices, which differs from the first embodiment in that: in the present embodiment, in the DC / DC main circuit of the energy storage converter, the SiC full-bridge secondary module also includes an inductor L201 and an inductor L202; the connection point of SiC MOSFET M201 and SiC MOSFET M203 is connected to the primary first input terminal of the high-frequency transformer T201 through a capacitor C200 and an inductor L201 connected in series; and the inductor L202 is connected in parallel to the primary of the high-frequency transformer T201.

[0041] The SiC full-bridge secondary module also includes an inductor L203; a circuit formed by connecting SiC MOSFET M205 and SiC MOSFET M207 in series, connected in parallel with a circuit formed by connecting SiC MOSFET M206 and SiC MOSFET M208 in series, connected in series with the high-frequency inductor L203, and then connected in parallel to the battery pack module.

[0042] This embodiment uses LLC series resonant soft switching technology to avoid the sharp increase in switching losses caused by increasing the inverter frequency to an ultra-high frequency, thereby greatly improving the energy efficiency of the energy storage converter.

[0043] The rest of the structure of this embodiment is the same as that of the first embodiment.

[0044] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A digital control system for energy storage converter based on SiC power devices, characterized in that: Including energy storage converter, MCU control system and control circuit; The control circuit includes an ultra-high frequency switch driving module, a sampling feedback module, a comprehensive protection module for implementing protection when a fault occurs, and a system communication module for communicating with the EMS system and the BMS system; The energy storage converter refers to an energy storage converter based on SiC power devices; the energy storage converter includes a DC / AC main circuit for converting current between direct current and alternating current, two or more DC / DC main circuits for transforming and isolating direct current, and a battery pack module; the DC / AC main circuit is connected to the DC / DC main circuit through a DC bus; each DC / DC main circuit is connected to the battery pack module respectively; The sampling feedback module collects the current and voltage values ​​of the battery pack module and the current and voltage values ​​of the DC bus between the DC / DC main circuit and the DC / AC main circuit, and sends the collected current and voltage values ​​to the MCU control system; The MCU control system uses the PID algorithm to adjust the output control signal according to the collected current and voltage values, and controls the working status of the SiC power devices of the energy storage converter through the ultra-high frequency switch drive module.

2. The digital control system for energy storage converter based on SiC power devices according to claim 1, characterized in that: Each DC / DC main circuit includes a SiC full-bridge primary module, a high-frequency transformer T201 and a SiC full-bridge secondary module connected in sequence; wherein the SiC full-bridge primary module is connected to the DC / AC main circuit through a DC bus; the SiC full-bridge primary module and the SiC full-bridge secondary module respectively adopt a full-bridge topology structure formed by SiC MOSFET; Bidirectional energy transfer is achieved between the three-phase AC grid and the battery module through the connected DC / AC main circuit and DC / DC main circuit; When energy is transferred from the three-phase AC grid to the battery pack module, the DC bus between the SiC full-bridge primary module and the DC / AC main circuit is the input side, the battery pack module is the output side, the SiC full-bridge primary module forms an inverter circuit, and the SiC full-bridge secondary module forms a rectifier circuit; when energy is transferred from the battery pack module to the three-phase AC grid, the battery pack module is the input side, the DC bus between the SiC full-bridge primary module and the DC / AC main circuit is the output side, the SiC full-bridge secondary module forms an inverter circuit, and the SiC full-bridge primary module forms a rectifier circuit; For the inverter circuit, the ultra-high frequency switch driver module outputs two complementary PWM signals with dead zones to control the two SiC MOSFETs at the diagonal of the inverter circuit to turn on or off at high frequency at the same time, converting DC power into high-frequency AC power. For the rectification circuit, the ultra-high frequency switch driving module turns off all SiC MOSFETs; the high-frequency AC is rectified through the rectification circuit formed by the body diode of SiC MOSFET.

3. The digital control system for energy storage converter based on SiC power devices according to claim 2 is characterized in that: The MCU control system uses a PID algorithm to adjust the output control signal according to the collected current and voltage values, which means: according to the collected measured current value and measured voltage value of the output side; The difference operation is performed with the preset current setting value and voltage setting value of the output side respectively, and the average difference is subjected to PID operation for several times to obtain the current fluctuation value and the voltage fluctuation value; according to the current fluctuation value and the voltage fluctuation value, the on-time and off-time of the SiC MOSFET of the inverter circuit are changed to realize the duty cycle adjustment, so that the current value and the voltage value of the output side are close to the current setting value and the voltage setting value respectively.

4. The digital control system for energy storage converter based on SiC power devices according to claim 2 is characterized in that: The SiC full-bridge primary module, the SiC MOSFET includes SiC MOSFETs M201 to M204; the SiC full-bridge primary module also includes a capacitor C200; After SiC MOSFET M201 and SiC MOSFET M203 are connected in series, they are connected in parallel to the DC / AC main circuit through the DC bus together with the circuit formed by SiC MOSFET M202 and SiC MOSFET M204 in series; the connection point of SiC MOSFET M201 and SiC MOSFET M203 is connected to the primary first input terminal of the high-frequency transformer T201 through the capacitor C200; the connection point of SiC MOSFET M202 and SiC MOSFET M204 is connected to the primary second input terminal of the high-frequency transformer T201; The SiC full-bridge secondary module, the SiC MOSFET includes SiC MOSFETs M205 to M208; the SiC full-bridge secondary module also includes a capacitor C209; After SiC MOSFET M205 and SiC MOSFET M207 are connected in series, they are connected in parallel to the battery pack module together with a circuit formed by SiC MOSFET M206 and SiC MOSFET M208 in series; the connection between SiC MOSFET M205 and SiC MOSFET M207 is connected to the secondary first output terminal of the high-frequency transformer T201 through capacitor C209; the connection between SiC MOSFET M206 and SiC MOSFET M208 is connected to the secondary second output terminal of the high-frequency transformer T201.

5. The digital control system for energy storage converter based on SiC power devices according to claim 4 is characterized in that: The SiC full-bridge secondary module also includes an inductor L201 and an inductor L202; the connection point of SiC MOSFET M201 and SiC MOSFET M203 is connected to the primary first input terminal of the high-frequency transformer T201 through a capacitor C200 and an inductor L201 connected in series; the inductor L202 is connected in parallel to the primary of the high-frequency transformer T201; The SiC full-bridge secondary module also includes an inductor L203; a circuit formed by connecting SiC MOSFET M205 and SiC MOSFET M207 in series, connected in parallel with a circuit formed by connecting SiC MOSFET M206 and SiC MOSFET M208 in series, connected in series with the high-frequency inductor L203, and then connected in parallel to the battery pack module.

6. The digital control system for energy storage converter based on SiC power devices according to claim 4 is characterized in that: The SiC full-bridge primary module further includes capacitors C201-C204 and resistors R201-R204; capacitor C201 and resistor R201 are connected in series and then connected in parallel to SiC MOSFET M201; capacitor C202 and resistor R202 are connected in series and then connected in parallel to SiC MOSFET M202; capacitor C203 and resistor R203 are connected in series and then connected in parallel to SiC MOSFET M203; capacitor C204 and resistor R204 are connected in series and then connected in parallel to SiC MOSFET M204; The SiC full-bridge secondary module also includes capacitors C205-C208 and resistors R205-R208; capacitor C205 and resistor R205 are connected in series and then connected in parallel to SiC MOSFET M205; capacitor C206 and resistor R206 are connected in series and then connected in parallel to SiC MOSFET M206; capacitor C207 and resistor R207 are connected in series and then connected in parallel to SiC MOSFET M207; capacitor C208 and resistor R208 are connected in series and then connected in parallel to SiC MOSFET M208.

7. The digital control system for energy storage converter based on SiC power devices according to any one of claims 1 to 6, characterized in that: The sampling feedback module includes a current sampling circuit and a voltage sampling circuit; The current sampling circuit includes a Hall current sensor, an integrated differential amplifier circuit 1 composed of a differential amplifier 1 and a peripheral circuit of the differential amplifier 1, a low-pass filter circuit composed of an operational amplifier 1 and a peripheral circuit of the operational amplifier 1, and an absolute value circuit 1 composed of an operational amplifier 2 and a peripheral circuit of the operational amplifier 2; The voltage sampling circuit includes a Hall voltage sensor, an integrated differential amplifier circuit 2 consisting of a differential amplifier 2 and a peripheral circuit of the differential amplifier 2, and an absolute value circuit 2 consisting of an operational amplifier 3 and a peripheral circuit of the operational amplifier 3.

8. The digital control system for energy storage converter based on SiC power devices according to any one of claims 1 to 6, characterized in that: The ultra-high frequency switch driving module includes a PWM signal isolation amplifier circuit and an ultra-high frequency switch driving circuit; The PWM signal isolation amplifier circuit comprises an optocoupler isolation circuit 1 composed of a high-speed optocoupler 1; The ultra-high frequency switch driving circuit includes a power supply circuit composed of a DC-DC power supply and a DC-DC power supply peripheral circuit, a magnetic isolation gate driving integrated circuit composed of an isolation driving chip and an isolation driving chip peripheral circuit, and a gate driving protection circuit.

9. The digital control system for energy storage converter based on SiC power devices according to any one of claims 1 to 6, characterized in that: The comprehensive protection module includes an overcurrent detection protection circuit and an undervoltage and overvoltage protection circuit; the overcurrent detection protection circuit includes a dual voltage comparator 1 and an optocoupler isolation circuit 2 composed of a high-speed optocoupler 2; the undervoltage and overvoltage protection circuit includes two dual voltage comparators 2 and a resistor voltage divider circuit.

10. The digital control system for energy storage converter based on SiC power devices according to any one of claims 1 to 6, characterized in that: The system communication module includes a CAN isolation communication circuit and an RS485 isolation communication circuit; the CAN isolation communication circuit includes an optocoupler isolation circuit three composed of a high-speed optocoupler three and a CAN signal generating circuit composed of a CAN transceiver; the RS485 isolation communication circuit includes an optocoupler isolation circuit four composed of a high-speed optocoupler four and an RS485 signal generating circuit composed of a 485 converter.

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