Energy-saving multi-stage energy storage converter based on SiC power device

Abstract

The invention provides an energy-saving multi-stage energy storage converter based on a SiC power device. The energy-saving multi-stage energy storage converter comprises a DC / AC main circuit, more than two DC / DC main circuits, a battery pack module and a digital control circuit, the DC / AC main circuit comprises a filtering module, an inductance energy storage module, an inversion rectification module, a filtering voltage stabilization module and a DC bus. Each DC / DC main circuit comprises a full-bridge primary circuit and a full-bridge secondary circuit; the full-bridge primary circuit comprises a high-frequency inversion module, a resonant tank module and a high-frequency transformer module; the full-bridge secondary circuit comprises a high-frequency rectification module and a reactance filtering module; the inversion rectification module adopts a three-phase full-bridge rectification topological structure formed by SiC IGBTs; and the high-frequency inversion module and the high-frequency rectification module respectively adopt a full-bridge topological structure formed by SiC MOSFETs. According to the energy storage converter, the energy loss in the conduction process is reduced, the wide output voltage working range is achieved, and meanwhile the good energy conversion efficiency can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage equipment, and more specifically to an energy-saving multi-level energy storage converter based on SiC power devices. Background Art

[0002] In the field of power system technology, it is necessary to accelerate the construction of a new power system that adapts to the increasing proportion of new energy, and energy storage is one of the main means to solve the challenges of energy transformation. The power storage converter (PCS) is the core component of the energy storage system and undertakes the key task of power conversion; power density and efficiency are the two key indicators to measure the comprehensive performance of PCS.

[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 improve 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. On the other hand, compared with ordinary energy storage converters, multi-stage energy storage converters will add a bidirectional DC / DC module. Although it can broaden the wide voltage operating range of the battery, the additional bidirectional DC / DC modules will also have energy loss, causing further aggravation of the energy loss of the energy storage converter and further reduction of the energy conversion efficiency of the energy storage converter. In the energy storage system where the battery module is distributed, multiple groups of bidirectional DC / DC modules will be equipped. The more bidirectional DC / DC modules, the more the technical problem of energy loss will be aggravated. Since the energy conversion efficiency of existing energy storage converters using Si-based power devices is low, the more bidirectional DC / DC modules are added, the more the technical problems of large energy loss and low energy conversion efficiency will be highlighted.

[0004] Therefore, it is urgent to design an energy storage converter using better power devices to improve energy conversion efficiency. Summary of the invention

[0005] In order to overcome the shortcomings and deficiencies in the prior art, the purpose of the present invention is to provide an energy-saving multi-stage energy storage inverter based on SiC power devices; the energy storage inverter adopts a new type of SiC power device, and utilizes the advantages of SiC power devices such as ultra-high operating frequency and extremely low on-resistance characteristics to fundamentally reduce the energy loss during the conduction process, and can have good energy conversion efficiency while achieving a wide output voltage operating range.

[0006] In order to achieve the above object, the present invention is implemented by the following technical solutions: an energy-saving multi-level energy storage converter based on SiC power devices, including a DC / AC main circuit, two or more DC / DC main circuits and a battery module matching the number of DC / DC main circuits, and a digital control circuit; The DC / AC main circuit includes a filter module, an inductor energy storage module, an inverter rectifier module, a filter voltage stabilization module and a DC bus which are connected in sequence; Each DC / DC main circuit includes a full-bridge primary circuit and a full-bridge secondary circuit connected to each other; the full-bridge primary circuit includes a high-frequency inverter module, a resonant tank module and a high-frequency transformer module T201 connected in sequence; the full-bridge secondary circuit includes a high-frequency rectifier module and a reactance filter module connected in sequence; The three-phase AC grid and the battery module are bidirectionally connected through the connected DC / AC main circuit and DC / DC main circuit to realize the energy transfer of industrial frequency AC-DC-high frequency AC-DC from the three-phase AC grid to the battery module, or the energy transfer of DC-high frequency AC-DC-industrial frequency AC from the battery module to the three-phase AC grid; Among them, the inverter rectifier module of the DC / AC main circuit adopts a three-phase full-bridge rectifier topology structure formed by SiC IGBT; the high-frequency inverter module and high-frequency rectifier module of the DC / DC main circuit respectively adopt a full-bridge topology structure formed by SiC MOSFET; The digital control circuit includes an MCU control system, a digital interactive system, a SiC high-frequency drive circuit and a power supply circuit for power supply; the MCU control system is connected to the inverter rectifier module of the DC / AC main circuit and the high-frequency inverter module and high-frequency rectifier module of the DC / DC main circuit through the SiC high-frequency drive circuit to control the direction of energy transfer between the three-phase AC power grid and the battery pack module.

[0007] Preferably, in the DC / AC main circuit, the filter module includes an inductor L101i and a capacitor C101i, i=a, b, c; the inductor energy storage module includes an inductor L102i; the inverter rectifier module includes SiC IGBT M101i, SiC IGBT M102i, a diode D101i and a diode D102i; the filter voltage stabilization module includes a filter voltage stabilization capacitor; SiC IGBT M101i and diode D101i are connected in parallel to form an upper arm of a three-phase full-bridge rectifier topology structure; SiC IGBT M102i and diode D102i are connected in parallel to form a lower arm of a three-phase full-bridge rectifier topology structure; the upper arm and the lower arm are connected in series; and the filter stabilizing capacitor is connected in parallel between the upper arm and the lower arm of the three-phase full-bridge rectifier topology structure; The three phases a, b and c of the three-phase AC power grid are respectively connected in series with the upper bridge arm and the lower bridge arm of the three-phase full-bridge rectifier topology structure through the same-phase and sequentially connected inductors L101i and L102i; the high-frequency inverter module of the DC / DC main circuit is connected in parallel between the upper bridge arm and the lower bridge arm of the three-phase full-bridge rectifier topology structure through the DC bus.

[0008] Preferably, when the energy transfer from the three-phase AC grid to the battery module is performed in the direction of industrial frequency AC-DC-high frequency AC-DC, the turn-on sequence of the SiC IGBT M101i and the SiC IGBT M102i is as follows: each SiC IGBT M101i is turned on in turn; When SiC IGBT M101i is turned on, one SiC IGBT M102i which is not in phase with the turned-on SiC IGBT M101i is turned on, and the other SiC IGBTs are turned off; then another SiC IGBTM102i which is not in phase with the turned-on SiC IGBT M101i is turned on, and the other SiC IGBTs are turned off, so as to realize the conversion of industrial frequency AC power into DC power; When energy is transferred from the battery pack module to the three-phase AC power grid in the direction of DC-high-frequency AC-DC-industrial frequency AC, the upper bridge arm and the lower bridge arm of the same phase in the three-phase full-bridge rectifier topology are alternately turned on, and the conduction angles of the upper bridge arm and the lower bridge arm are both 180°. The time when each phase starts conducting differs by 120° in sequence, so as to realize the conversion of DC power into industrial frequency AC power.

[0009] Preferably, in the full-bridge primary main circuit of the DC / DC main circuit, the high-frequency inverter module includes SiC MOSFETs M201 to M204; the resonant tank module includes a capacitor C200, an inductor L201 and an inductor L202; After SiC MOSFET M201 and SiC MOSFET M203 are connected in series, they are connected in parallel at both ends of the inverter rectifier module of the DC / AC main circuit together with the circuit formed in series with SiC MOSFET M202 and SiC MOSFET M204 through the DC bus; SiCMOSFET M201~M204 are respectively connected in parallel with RC series circuit one and body diode one; the series connection of SiC MOSFET M201 and SiCMOSFET M203 is connected to the series connection of SiCMOSFET M202 and SiCMOSFET M204 through the series connection of capacitor C200, inductor L201 and the primary of high-frequency transformer module T201; inductor L202 is connected in parallel to the primary of high-frequency transformer module T201.

[0010] Preferably, when the energy transfer from the three-phase AC grid to the battery module is carried out in the direction of industrial frequency AC-DC-high frequency AC-DC, SiC MOSFETs M201 to M204 realize high frequency inversion to convert DC into high frequency AC. When the energy transfer from the battery pack module to the three-phase AC power grid is carried out in the direction of DC-high-frequency AC-DC-industrial frequency AC, all SiC MOSFETs M201 to M204 are turned off, and the parallel body diodes of SiC MOSFETs M201 to M204 form a rectification circuit to realize high-frequency rectification, thereby converting high-frequency AC into DC.

[0011] Preferably, when the energy transfer of industrial frequency AC-DC-high frequency AC-DC from the three-phase AC grid to the battery pack module is performed, the SiC MOSFETs M201-M204 realize high-frequency inversion, which means that: for the two diagonal SiC MOSFETs of the full-bridge topology structure formed by the SiC MOSFETs M201-M204, two complementary PWM signals with dead zones are used to control simultaneous high-frequency switching on or off, so as to convert DC power into high-frequency AC power; In the dead zone when all SiC MOSFETs are turned off, the current stored in the inductors L201 and L202 of the resonant tank module charges the capacitor of the RC series circuit 1 in parallel with one of the diagonal SiC MOSFETs, and discharges the capacitor of the RC series circuit 1 in parallel with the other diagonal SiC MOSFET; after complete discharge, the body diode 1 in parallel with the SiC MOSFET is turned on, clamping the drain-source voltage of the SiC MOSFET to zero voltage, thereby realizing zero-voltage soft switching.

[0012] Preferably, in the full-bridge secondary circuit of the DC / DC main circuit, the high-frequency rectifier module includes SiC MOSFETM205-M208; the reactance filter module includes a high-frequency inductor L203; The circuit formed by the series connection of SiC MOSFET M205 and SiC MOSFET M207 is connected in parallel with the circuit formed by the series connection of SiC MOSFET M206 and SiC MOSFET M208, and then connected in series with the high-frequency inductor L203, and then connected in parallel to the battery pack module; SiC MOSFET M205~M208 are respectively connected in parallel with RC series circuit 2 and body diode 2; the series connection of SiC MOSFET M205 and SiC MOSFET M207 is connected to the series connection of SiC MOSFETM206 and SiC MOSFET M208 through the series capacitor C209 and the secondary of the high-frequency transformer module T201.

[0013] Preferably, when the energy transfer from the three-phase AC grid to the battery module is carried out in the direction of industrial frequency AC-DC-high frequency AC-DC, SiC MOSFETs M205 to M208 implement high frequency rectification to convert high frequency AC into DC; When the energy transfer from the battery pack module to the three-phase AC grid is carried out in the direction of DC-high-frequency AC-DC-industrial-frequency AC, all SiC MOSFETs M205 to M208 are turned off, and the parallel body diodes of SiC MOSFETs M205 to M208 form a rectifier circuit to achieve high-frequency inversion, converting DC power into high-frequency AC power.

[0014] Preferably, when energy transfer from the battery pack module to the three-phase AC power grid is performed in the direction of DC-high-frequency AC-DC-industrial-frequency AC, the SiC MOSFETs M205 to M208 realize high-frequency inversion, which means that for the two diagonal SiC MOSFETs of the full-bridge topology structure formed by the SiC MOSFETs M205 to M208, two complementary PWM signals with dead zones are used to control simultaneous high-frequency opening or closing to convert DC power into high-frequency AC power.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The energy-saving multi-stage energy storage converter based on SiC power devices of the present invention can realize bidirectional energy transfer between the three-phase AC power grid and the battery module; it can realize both charging of the battery module and power supply of the battery module to the three-phase AC power grid; 2. Compared with the traditional energy storage converter, the energy-saving multi-stage energy storage converter based on SiC power devices of the present invention introduces the third-generation wide bandgap (Eg>2.3eV) silicon carbide (SiC) semiconductor power devices in all directions. Its extremely low on-resistance characteristic fundamentally reduces the energy loss in the conduction process and achieves a significant improvement in energy efficiency. For more DC / DC main circuits, the greater the gap in energy conversion efficiency with the traditional Si energy storage converter, the more significant the advantages brought by the technology upgrade; 3. The power switch devices of the energy-saving multi-stage energy storage converter based on SiC power devices of the present invention all adopt new SiC power devices, and the operating frequency is up to 200kHz, which is nearly ten times higher than the currently commonly used IGBT. Not only the size of the whole machine is greatly reduced, but also the dynamic response speed is more ideal; 4. The present invention 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a circuit diagram of a DC / AC main circuit and a DC / DC main circuit of an energy-saving multi-stage energy storage converter based on SiC power devices of the present invention; Figure 2 It is a system structure block diagram of the energy-saving multi-stage energy storage converter based on SiC power devices of the present invention; Figure 3 It is a system connection block diagram of the energy-saving multi-stage 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] Example like Figures 1 to 3 As shown, in this embodiment, an energy-saving multi-level energy storage converter based on SiC power devices includes a DC / AC main circuit, two or more DC / DC main circuits, a battery pack module matching the number of DC / DC main circuits, and a digital control circuit. This embodiment takes two DC / DC main circuits and a battery pack module as an example; in actual applications, the number of DC / DC main circuits and battery pack modules can be three, four, five, or even more.

[0019] The DC / AC main circuit includes a filter module, an inductor energy storage module, an inverter rectifier module, a filter voltage stabilization module and a DC bus which are connected in sequence.

[0020] Each DC / DC main circuit includes a full-bridge primary circuit and a full-bridge secondary circuit connected to each other; the full-bridge primary circuit includes a high-frequency inverter module, a resonant tank module and a high-frequency transformer module T201 connected in sequence; the full-bridge secondary circuit includes a high-frequency rectifier module and an inductive filter module connected in sequence.

[0021] 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 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.

[0022] The digital control circuit includes an MCU control system, a digital interaction system, a SiC high-frequency drive circuit and a power supply circuit for power supply; the MCU control system is connected to the inverter rectifier module of the DC / AC main circuit and the high-frequency inverter module and high-frequency rectifier module of the DC / DC main circuit through the SiC high-frequency drive circuit to control the direction of energy transfer between the three-phase AC power grid and the battery pack module.

[0023] Specifically, in the DC / AC main circuit, the filter module includes an inductor L101i and a capacitor C101i, i=a, b, c; the inductor energy storage module includes an inductor L102i. The inverter rectifier module adopts a three-phase full-bridge rectifier topology structure formed by SiC IGBT; the inverter rectifier module includes SiC IGBT M101i, SiC IGBT M102i, a diode D101i and a diode D102i; the filter voltage regulator module includes filter voltage regulator capacitors C104 to C107.

[0024] SiC IGBT M101i and diode D101i are connected in parallel to form an upper arm of a three-phase full-bridge rectifier topology; SiC IGBT M102i and diode D102i are connected in parallel to form a lower arm of a three-phase full-bridge rectifier topology; the upper arm and the lower arm are connected in series; filtering and stabilizing capacitors C104 and C106 are connected in series, and then connected in parallel with a series circuit composed of C105 and C107 in series between the upper arm and the lower arm of the three-phase full-bridge rectifier topology.

[0025] The three phases a, b and c of the three-phase AC power grid are respectively connected in series with the upper bridge arm and the lower bridge arm of the three-phase full-bridge rectifier topology structure through the same-phase and sequentially connected inductors L101i and L102i; the high-frequency inverter module of the DC / DC main circuit is connected in parallel between the upper bridge arm and the lower bridge arm of the three-phase full-bridge rectifier topology structure through the DC bus.

[0026] In the DC / DC main circuit, the high-frequency inverter module and the high-frequency rectifier module respectively adopt a full-bridge topology structure formed by SiC MOSFET.

[0027] The high-frequency inverter module includes SiC MOSFET M201-M204; the resonant tank module includes capacitor C200, inductor L201 and inductor L202; after SiC MOSFET M201 and SiC MOSFET M203 are connected in series, they are connected in parallel with the circuit formed by SiC MOSFET M202 and SiC MOSFET M204 in series through a DC bus at both ends of the inverter rectifier module of the DC / AC main circuit; SiC MOSFET M201-M204 are respectively connected in parallel with an RC series circuit one and a body diode one; the series connection of SiC MOSFET M201 and SiC MOSFET M203 is connected to the series connection of SiC MOSFET M202 and SiC MOSFET M204 through the series capacitor C200, inductor L201 and the primary of the high-frequency transformer module T201; the inductor L202 is connected in parallel to the primary of the high-frequency transformer module T201.

[0028] The high-frequency rectifier module includes SiC MOSFET M205-M208; the reactance filter module includes a high-frequency inductor L203; The circuit formed by the series connection of SiC MOSFET M205 and SiC MOSFET M207 is connected in parallel with the circuit formed by the series connection of SiC MOSFET M206 and SiC MOSFET M208, and then connected in series with the high-frequency inductor L203, and then connected in parallel to the battery pack module; SiC MOSFET M205~M208 are respectively connected in parallel with RC series circuit 2 and body diode 2; the series connection of SiC MOSFET M205 and SiC MOSFET M207 is connected to the series connection of SiC MOSFETM206 and SiC MOSFET M208 through the series capacitor C209 and the secondary of the high-frequency transformer module T201.

[0029] When the energy is transferred from the three-phase AC grid to the battery module in the direction of industrial frequency AC-DC-high frequency AC-DC, the energy passes through the three-phase AC grid-DC / AC main circuit-DC / DC main circuit-battery module. The working principle of the energy-saving multi-stage energy storage converter based on SiC power devices is as follows: In the DC / AC main circuit, the turn-on sequence of SiC IGBT M101i and SiC IGBT M102i is as follows: each SiC IGBT M101i is turned on in turn; while SiC IGBT M101i is turned on, one of the SiC IGBT M102i that is not in the same phase as the turned-on SiC IGBT M101i is turned on, and the other SiC IGBTs are turned off; then another SiC IGBT M102i that is not in the same phase as the turned-on SiC IGBT M101i is turned on, and the other SiC IGBTs are turned off; for example: SiC IGBT M101a and SiC IGBT M102b are turned on and the other are turned off, SiC IGBT M101a and SiC IGBT M102c are turned on and the other are turned off, SiC IGBT M101b and SiC IGBT M102c are turned on and the other are turned off, and SiC IGBT M101b and SiC IGBT M102c are turned on and the other are turned off. M102a is turned on and the others are turned off, SiC IGBT M101c and SiCIGBT M102a are turned on and the others are turned off, SiC IGBT M101c and SiCIGBT M102b are turned on and the others are turned off; so as to realize the conversion of the industrial frequency AC power of the three-phase AC power grid into DC power; and then converted into smooth DC power through the filtering and voltage stabilizing module and transmitted to the DC bus; In the full-bridge primary circuit of the DC / DC main circuit, SiC MOSFETs M201 to M204 realize high-frequency inversion. For the two diagonal SiC MOSFETs of the full-bridge topology structure formed by SiC MOSFETs M201 to M204, two complementary PWM signals with dead zones are used to control simultaneous high-frequency switching on or off, so as to convert DC power into high-frequency AC power. In the dead zone when all SiC MOSFETs are turned off, the current stored in the inductors L201 and L202 of the resonant tank module charges the capacitor of the RC series circuit 1 in parallel with one of the diagonal SiC MOSFETs, and discharges the capacitor of the RC series circuit 1 in parallel with the other diagonal SiC MOSFET. After the discharge is complete, the body diode 1 in parallel with the SiCMOSFET is turned on, clamping the drain-source voltage of the SiCMOSFET to zero voltage, thus realizing zero-voltage soft switching. The high-frequency AC power is then electrically isolated, transformed, and the power is transferred to the full-bridge secondary circuit through the high-frequency transformer module. In the full-bridge secondary circuit, high-frequency AC power is input from the high-frequency transformer module, and all SiC MOSFETs M205 to M208 are turned off. The parallel-connected body diodes of SiC MOSFETs M205 to M208 form a rectifier circuit to achieve high-frequency rectification. The high-frequency AC power is converted into low-voltage smooth DC power through the reactance filter module and output to the battery pack module, thereby realizing the energy transfer of industrial frequency AC-DC-high-frequency AC-DC from the three-phase AC grid to the battery pack module.

[0030] When the energy is transferred from the battery pack module to the three-phase AC grid in the direction of DC-high frequency AC-DC-power frequency AC, the energy passes through the battery pack module-DC / DC main circuit-DC / AC main circuit-three-phase AC grid. The working principle of the energy-saving multi-stage energy storage converter based on SiC power devices is as follows: In the full-bridge secondary circuit of the DC / DC main circuit, the smooth DC output by the battery pack module is input into the high-frequency rectifier module, which acts as a high-frequency inverter module. The SiC MOSFET M205-M208 realizes high-frequency inverter. For the two diagonal SiC MOSFETs of the full-bridge topology structure formed by the SiCMOSFET M205-M208, two complementary PWM signals with dead zones are used to control simultaneous high-frequency opening or closing to convert DC power into high-frequency AC power. In the full-bridge primary circuit, high-frequency AC is input from the high-frequency transformer module to the high-frequency inverter module. At this time, the high-frequency inverter module acts as a high-frequency rectifier module, and all SiC MOSFETs M201 to M204 are turned off. The parallel body diodes of SiC MOSFETs M201 to M204 form a rectifier circuit to achieve high-frequency rectification, converting the high-frequency AC into DC and then into low-voltage smooth DC, which is then output to the DC bus module. In the DC / AC main circuit, direct current is input from the DC bus module to the inverter rectifier module after passing through the filter and voltage regulator module. The three-phase full-bridge rectifier topology of the inverter rectifier module performs industrial frequency inversion. The upper bridge arm and the lower bridge arm of the same phase are alternately turned on. The conduction angles of the upper bridge arm and the lower bridge arm are both 180°, and the time when each phase starts to conduct is 120° apart, so as to realize the conversion of direct current into industrial frequency alternating current. The inverted industrial frequency alternating current is then transmitted to the three-phase AC power grid through the filter module; thereby realizing the energy transmission of DC-high frequency AC-DC-industrial frequency AC from the battery pack module to the three-phase AC power grid.

[0031] In this embodiment, the energy-saving multi-stage energy storage inverter is based on SiC power devices. The BMS system, EMS system and energy storage inverter (PCS) system are connected through the CAN bus respectively; the BMS system is connected to the battery pack module through CAN or RS485; the EMS system is connected to the three-phase AC power grid by monitoring the power grid status; the PCS system is connected to the DC / AC main circuit and the DC / DC main circuit through the RS485 serial port of the digital control circuit; the three-phase AC power grid and the battery pack module exchange energy through the DC / AC main circuit and the DC / DC main circuit.

[0032] In the digital control circuit, the SiC high-frequency drive circuit is connected to the inverter rectifier module of the DC / AC main circuit and the high-frequency inverter module and high-frequency rectifier module of the DC / DC main circuit; the MCU system adopts a 32-bit high-speed ARM microprocessor, which generates three sets of fully digital PWM control signals to drive the SiC power device; the MCU system is connected to the digital interactive interface via RS485.

[0033] The working principle of the energy-saving multi-stage energy storage inverter based on SiC power devices of the present invention is: taking grid connection as an example, first obtain the battery pack status information through the BMS system, obtain the grid status information through the EMS system, and after confirming that the grid connection operation can be carried out, determine the energy transfer direction through the digital interactive interface, and the energy storage inverter (PCS) system receives the control instructions of the background CAN bus through digital control circuit communication, and controls the energy storage inverter to discharge the battery according to the sign and size of the power instruction. The energy is transmitted through the battery pack-DC / DC main circuit-DC / AC main circuit-grid, completing the energy transfer of DC-high frequency AC-DC-industrial frequency AC.

[0034] 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. An energy-saving multi-stage energy storage converter based on SiC power devices, characterized in that: It includes a DC / AC main circuit, two or more DC / DC main circuits, a battery pack module matching the number of DC / DC main circuits, and a digital control circuit; The DC / AC main circuit includes a filter module, an inductor energy storage module, an inverter rectifier module, a filter voltage stabilization module and a DC bus which are connected in sequence; Each DC / DC main circuit includes a full-bridge primary circuit and a full-bridge secondary circuit connected to each other; the full-bridge primary circuit includes a high-frequency inverter module, a resonant tank module and a high-frequency transformer module T201 connected in sequence; the full-bridge secondary circuit includes a high-frequency rectifier module and a reactance filter module connected in sequence; The three-phase AC grid and the battery module are bidirectionally connected through the connected DC / AC main circuit and DC / DC main circuit to realize the energy transfer of industrial frequency AC-DC-high frequency AC-DC from the three-phase AC grid to the battery module, or the energy transfer of DC-high frequency AC-DC-industrial frequency AC from the battery module to the three-phase AC grid; Among them, the inverter rectifier module of the DC / AC main circuit adopts a three-phase full-bridge rectifier topology structure formed by SiC IGBT; the high-frequency inverter module and high-frequency rectifier module of the DC / DC main circuit respectively adopt a full-bridge topology structure formed by SiC MOSFET; The digital control circuit includes an MCU control system, a digital interactive system, a SiC high-frequency drive circuit and a power supply circuit for power supply; the MCU control system is connected to the inverter rectifier module of the DC / AC main circuit and the high-frequency inverter module and high-frequency rectifier module of the DC / DC main circuit through the SiC high-frequency drive circuit to control the direction of energy transfer between the three-phase AC power grid and the battery pack module.

2. The energy-saving multi-stage energy storage converter based on SiC power devices according to claim 1, characterized in that: In the DC / AC main circuit, the filter module includes an inductor L101i and a capacitor C101i, i=a, b, c; the inductor energy storage module includes an inductor L102i; the inverter rectifier module includes SiC IGBT M101i, SiC IGBT M102i, a diode D101i and a diode D102i; the filter voltage stabilization module includes a filter voltage stabilization capacitor; SiC IGBT M101i and diode D101i are connected in parallel to form an upper arm of a three-phase full-bridge rectifier topology structure; SiC IGBT M102i and diode D102i are connected in parallel to form a lower arm of a three-phase full-bridge rectifier topology structure; the upper arm and the lower arm are connected in series; and the filter stabilizing capacitor is connected in parallel between the upper arm and the lower arm of the three-phase full-bridge rectifier topology structure; The three phases a, b and c of the three-phase AC power grid are respectively connected in series with the upper bridge arm and the lower bridge arm of the three-phase full-bridge rectifier topology structure through the same-phase and sequentially connected inductors L101i and L102i; the high-frequency inverter module of the DC / DC main circuit is connected in parallel between the upper bridge arm and the lower bridge arm of the three-phase full-bridge rectifier topology structure through the DC bus.

3. The energy-saving multi-stage energy storage converter based on SiC power devices according to claim 2, characterized in that: When the energy transfer from the three-phase AC grid to the battery module is performed in the direction of industrial frequency AC-DC-high frequency AC-DC, the turn-on sequence of the SiC IGBT M101i and the SiC IGBT M102i is as follows: each SiC IGBT M101i is turned on in turn; When the SiC IGBT M101i is turned on, one of the SiC IGBTM102i that is not in phase with the turned-on SiC IGBT M101i is turned on, and the other SiC IGBTs are turned off; then another SiC IGBTM102i that is not in phase with the turned-on SiC IGBT M101i is turned on, and the other SiC IGBTs are turned off, so as to convert the industrial frequency AC power into DC power; When energy is transferred from the battery pack module to the three-phase AC power grid in the direction of DC-high-frequency AC-DC-industrial frequency AC, the upper bridge arm and the lower bridge arm of the same phase in the three-phase full-bridge rectifier topology are alternately turned on, and the conduction angles of the upper bridge arm and the lower bridge arm are both 180°. The time when each phase starts conducting differs by 120° in sequence, so as to realize the conversion of DC power into industrial frequency AC power.

4. The energy-saving multi-stage energy storage converter based on SiC power devices according to claim 1, characterized in that: In the full-bridge primary main circuit of the DC / DC main circuit, the high-frequency inverter module includes SiC MOSFETs M201 to M204; the resonant tank module includes a capacitor C200, an inductor L201 and an inductor L202; After SiC MOSFET M201 and SiC MOSFET M203 are connected in series, they are connected in parallel at both ends of the inverter rectifier module of the DC / AC main circuit together with the circuit formed by SiC MOSFET M202 and SiC MOSFET M204 in series through the DC bus; SiC MOSFETM201~M204 are respectively connected in parallel with an RC series circuit one and a body diode one; the series connection of SiC MOSFET M201 and SiC MOSFET M203 is connected to the series connection of SiC MOSFET M202 and SiC MOSFET M204 through a series capacitor C200, an inductor L201 and a primary of a high-frequency transformer module T201; and the inductor L202 is connected in parallel to the primary of the high-frequency transformer module T201.

5. The energy-saving multi-stage energy storage converter based on SiC power devices according to claim 4, characterized in that: When the energy transfer from the three-phase AC grid to the battery module is carried out in the direction of industrial frequency AC-DC-high frequency AC-DC, all SiC MOSFETs M201-M204 are turned off, and the parallel body diodes of SiC MOSFETs M201-M204 form a rectifier circuit to achieve high-frequency inversion, converting DC power into high-frequency AC power. When the energy transfer from the battery pack module to the three-phase AC grid is carried out in the direction of DC-high-frequency AC-DC-industrial-frequency AC, SiC MOSFETs M201 to M204 realize high-frequency rectification to convert the high-frequency AC into DC.

6. The energy-saving multi-stage energy storage converter based on SiC power devices according to claim 5, characterized in that: When the energy transfer from the three-phase AC grid to the battery module is carried out in the direction of industrial frequency AC-DC-high frequency AC-DC, SiC MOSFET M201-M204 realizes high frequency inversion, which means that two SiC MOSFETs at the diagonal of the full-bridge topology structure formed by SiC MOSFET M201-M204 are simultaneously turned on or off at high frequency using two complementary PWM signals with dead zones to convert DC power into high frequency AC power. In the dead zone when all SiC MOSFETs are turned off, the current stored in the inductors L201 and L202 of the resonant tank module charges the capacitor of the RC series circuit 1 in parallel with one of the diagonal SiC MOSFETs, and discharges the capacitor of the RC series circuit 1 in parallel with the other diagonal SiC MOSFET; after complete discharge, the body diode 1 in parallel with the SiC MOSFET is turned on, clamping the drain-source voltage of the SiC MOSFET to zero voltage, thereby realizing zero-voltage soft switching.

7. The energy-saving multi-stage energy storage converter based on SiC power devices according to claim 1, characterized in that: In the full-bridge secondary circuit of the DC / DC main circuit, the high-frequency rectifier module includes SiC MOSFETs M205 to M208; the reactance filter module includes a high-frequency inductor L203; The circuit formed by the series connection of SiC MOSFET M205 and SiC MOSFET M207 is connected in parallel with the circuit formed by the series connection of SiC MOSFET M206 and SiC MOSFET M208, and then connected in series with the high-frequency inductor L203, and then connected in parallel to the battery pack module; SiC MOSFET M205~M208 are respectively connected in parallel with RC series circuit 2 and body diode 2; the series connection of SiC MOSFET M205 and SiC MOSFET M207 is connected to the series connection of SiC MOSFETM206 and SiC MOSFET M208 through the series capacitor C209 and the secondary of the high-frequency transformer module T201.

8. The energy-saving multi-stage energy storage converter based on SiC power devices according to claim 7, characterized in that: When the energy transfer from the three-phase AC grid to the battery module is carried out in the direction of industrial frequency AC-DC-high frequency AC-DC, all SiC MOSFETs M205-M208 are turned off, and the parallel body diodes of SiC MOSFETs M205-M208 form a rectifier circuit to realize high-frequency rectification, converting high-frequency AC into DC. When the energy transfer from the battery pack module to the three-phase AC grid is from DC to high-frequency AC, DC to industrial frequency AC, SiC MOSFETs M205 to M208 realize high-frequency inversion and convert DC power into high-frequency AC power.

9. The energy-saving multi-stage energy storage converter based on SiC power devices according to claim 8, characterized in that: When the energy transfer from the battery pack module to the three-phase AC grid is DC-high-frequency AC-DC-industrial-frequency AC, the SiC MOSFETs M205 to M208 realize high-frequency inversion, which means that two SiC MOSFETs at the diagonal of the full-bridge topology structure formed by the SiC MOSFETs M205 to M208 are simultaneously turned on or off at high frequency using two complementary PWM signals with dead zones to convert DC power into high-frequency AC power.

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