Photovoltaic power station energy storage type DC power grid conversion system

Abstract

The invention discloses a photovoltaic power station energy storage type direct-current power grid conversion system, and relates to the technical field of power grid conversion systems, the photovoltaic power station energy storage type direct-current power grid conversion system comprises a PV assembly + MPPT super capacitor energy storage direct-current grid-connected converter, a DC-DC boosting transformer module and a PV-850V-10KV / 10MW photovoltaic power station system, the PV assembly + MPPT super capacitor energy storage direct-current grid-connected converter comprises a main circuit and a grid-connected controller, the main circuit comprises a PV assembly, a Boost converter, a super capacitor SC, a bidirectional full-bridge converter, a first high-frequency transformer, a cyclic resonance commutation bidirectional converter and a first output filter circuit. The grid-connected control comprises PV voltage and current sampling and MPPT control. The problem that the use efficiency of the lead-acid battery is greatly reduced under the outdoor cold condition is solved, the system reliability and the overall efficiency are improved, the number of switches is reduced, and complete soft switching is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid conversion systems, and in particular to a photovoltaic power station energy storage type direct current power grid conversion system. Background Art

[0002] The development of flexible power electronics technology has made it an inevitable trend to establish a DC grid conversion system for photovoltaic power stations. The capacitive impedance and inductive impedance of the traditional AC access system are large, and the problems of harmonic resonance and reactive power transmission are particularly prominent. The DC access system has no transmission reactance, a high degree of modularization, higher stability, no need for reactive power compensation, and a stronger transmission capacity and lower loss at the same voltage level; the DC grid conversion system has a simple control method and a high photovoltaic utilization rate, so the DC grid conversion system of the photovoltaic power station can be used to resolve the constraints of AC aggregation on large-scale photovoltaic power stations, which is expected to solve the current stability problems and overall low efficiency problems of photovoltaic power stations. The document "Research on Voltage Level Sequence of DC Collection System of Photovoltaic Power Station" (Acta Energiae Solaris Sinica, Vol. 41, No. 10) concludes that different voltages are suitable for different scenarios based on the different characteristics of the loads: when the end of the medium voltage collection system is directly connected to the load network, such as subway traction, industrial parks, large data centers, and urban distribution systems, a voltage level sequence of 800-850V boosted to 10kV is selected; when the medium voltage collection system is connected to a high voltage DC system (such as ±110kV), a voltage level sequence of 800-850V boosted to ±35kV is selected.

[0003] Lithium-ion, nickel-metal hydride and other battery technologies have made great progress in providing reliable energy storage solutions. All of these technologies are based on chemical reactions, have limited service life and are limited by temperature. Supercapacitors have the characteristics of high power density and energy density, long service life and compact size. The best supercapacitors are ultra-high power devices with a power density of up to 20kW / kg, and can discharge very quickly or very slowly. Supercapacitor modules are a new type of energy pack composed of multiple supercapacitor cells in series, with voltage balancing and discharge voltage stabilization systems, and an aluminum alloy shell. The birth of supercapacitor modules makes up for the defects of energy storage devices such as lead-acid batteries. The operating temperature range of supercapacitor modules is -40 to 65°C, which solves the problem that the efficiency of lead-acid batteries is greatly reduced under cold outdoor conditions. In addition, supercapacitor modules not only have all the characteristics of supercapacitor cells, but also have status monitoring functions, which can better achieve maintenance-free and easy maintenance.

[0004] The DC grid-connected converter converts the voltage of the solar photovoltaic cell module to the low-voltage DC transmission network. At present, for the DC grid-connected converter including energy storage device, a three-port DC-DC converter is proposed, in which the voltage of the solar photovoltaic cell module is the first port and the voltage of the energy storage battery is the second port. Usually, according to whether there is electrical isolation, the three-port DC-DC DC grid-connected converter topology is divided into three types: non-isolated, partially isolated and fully isolated. The non-isolated three-port DC-DC converter generally adopts the Buck-Boost parallel topology. The grid-connected converter does not have the electrical isolation function, so it is only suitable for low power and occasions where the grid voltage and the voltage of the solar photovoltaic cell module are relatively small; the first and second ports of the partially isolated three-port DC-DC direct current grid-connected converter are not electrically isolated, and the first and second ports are isolated from the third port by a transformer, including half-bridge and full-bridge types. The half-bridge type is a step-down type, and the full-bridge type requires four switch tubes; the fully isolated three-port DC-DC direct current grid-connected converter realizes electrical isolation of all ports through a three-winding transformer. Each bridge unit can realize bidirectional power flow, and all switch tubes can be soft-switched with the assistance of the transformer leakage inductance. However, this type of converter has a voltage matching problem, that is, the voltage ratio between different windings of the transformer needs to be consistent with the corresponding transformer ratio. When the input voltage changes in a large range, the current stress on the switch tube is also large, and the soft switching range will become smaller.

[0005] The DC transformer boosts the low-voltage DC transmission voltage to a medium-voltage DC voltage. It can be divided into two categories: isolated and non-isolated, depending on whether an AC transformer is used. The isolated DC transformer goes through the DC-AC and AC-DC links, and uses the AC transformer in the middle to achieve the transformation ratio. Non-isolated DC transformers can be divided into voltage-dividing, resonant, and DC chopper types according to the voltage-dividing principle. The isolated DC transformer has the advantage of fault isolation. The use of medium-frequency or high-frequency transformers can reduce the size of the AC transformer and the size of related passive components, and is suitable for large-capacity and high-ratio occasions. Non-isolated DC transformers have low losses and high efficiency because they lack the AC transformation link in the middle. However, due to the direct electrical connection between the high and low voltage sides, it is difficult to control when the DC voltage at both ends is relatively large. Therefore, this type of topology is suitable for large-capacity, medium-low ratio occasions. Summary of the invention

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a photovoltaic power station energy storage type DC grid conversion system, which can be applied to the grid-connected converter, DC transformer and its derivative products of the DC grid.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A photovoltaic power station energy storage type DC grid conversion system includes a PV component + MPPT supercapacitor energy storage DC grid-connected converter, a DC-DC boost transformer module, and a PV-850V-10KV / 10MW photovoltaic power station system.

[0009] The PV component + MPPT supercapacitor energy storage DC grid-connected converter includes a main circuit and grid-connected control. The main circuit includes a PV component, a Boost converter, a supercapacitor SC, a bidirectional full-bridge converter, a high-frequency transformer and a cyclic resonant commutation bidirectional converter, and an output filter circuit. The grid-connected control includes PV voltage and current sampling, MPPT control, grid voltage and current sampling, PWM phase shift control, synchronous control, bidirectional full-bridge converter control, and cyclic resonant commutation bidirectional converter control.

[0010] The Boost converter includes a switch tube nine, a diode, a boost inductor, and a filter capacitor one, wherein the switch tube nine, the diode, and the boost inductor form a Boost boost DC / DC converter; the supercapacitor SC is composed of a supercapacitor module for energy storage and voltage stabilization; the bidirectional full-bridge converter includes a MOSFET switch tube one, a MOSFET switch tube two, a MOSFET switch tube three, and a MOSFET switch tube four to form a bidirectional full-bridge conversion circuit; the high-frequency transformer one and the circulating resonant commutation bidirectional converter include a high-frequency transformer one, a resonant inductor, a circulating commutation resonant capacitor one, a circulating commutation resonant capacitor two, a silicon carbide switch tube one, and a silicon carbide switch tube two, wherein the circulating commutation resonant capacitor one, the circulating commutation resonant capacitor two and the resonant inductor participate in resonance, and the circulating commutation resonant capacitor one, the circulating commutation resonant capacitor two and the silicon carbide switch tube one, and the silicon carbide switch tube two form a circulating converter; the output filter circuit one includes a filter capacitor two, a filter capacitor three, and a common-mode filter inductor.

[0011] The high-frequency transformer 1 and the circulating resonant commutation bidirectional converter are composed of a resonant inductor, a circulating commutation resonant capacitor 1, a circulating commutation resonant capacitor 2 and a silicon carbide switch tube 1 and a silicon carbide switch tube 2 to form a circulating resonant circuit. The sum of the voltages on the circulating commutation resonant capacitor 1 and the circulating commutation resonant capacitor 2 in the circulating commutation resonance does not exceed the low-voltage DC grid voltage. The connection polarities of the silicon carbide switch tube 1 and the silicon carbide switch tube 2 are opposite, wherein the S pole of the silicon carbide switch tube 1 is connected to the resonant inductor, and the D pole is connected to the circulating commutation resonant capacitor 1 and the output filter inductor; the D pole of the silicon carbide switch tube 2 is connected to the resonant inductor, and the S pole is connected to the circulating commutation resonant capacitor 2 and the output port U850-.

[0012] The grid-connected control of the MPPT supercapacitor energy storage DC grid-connected converter includes PV voltage and current sampling, which is used to collect the voltage of the PV photovoltaic module and the current during the working process; MPPT control, which performs maximum power tracking control according to the voltage of the PV photovoltaic module and the current during the working process; grid voltage and current sampling, which is used to collect the voltage of the DC grid and the output current of the grid-connected converter; PWM phase shift control, which performs PWM phase shift control calculation according to the MPPT control and the grid voltage and current sampling values; and synchronous control, which synchronously controls two units of bidirectional full-bridge converter control and cyclic resonant commutation bidirectional converter control according to the PWM phase shift control calculation result, so as to realize synchronous resonant cyclic commutation of the bidirectional full-bridge converter and the cyclic resonant commutation bidirectional converter.

[0013] The MPPT supercapacitor energy storage DC grid-connected converter has three working modes: PV module power grid-connected working mode, supercapacitor SC power grid-connected working mode, and grid charging supercapacitor SC working mode.

[0014] The MPPT supercapacitor energy storage DC grid-connected converter and the PV component energy grid-connected working mode are as follows: the Boost converter is controlled by the MPPT, when the switch tube nine is turned on, the boost inductor stores energy, and the current loop of this process is as follows: PV component UPV+→boost inductor→switch tube nine→PV component UPV-; when the switch tube nine is turned off, the diode is turned on, the supercapacitor SC is charged, and the DC bus Usc is powered at the same time, and the transformer primary current loop of this process is as follows: photovoltaic cell component UPV+→boost inductor→diode→Usc→bidirectional full-bridge converter→transformer primary winding→PV component PV-; transformer secondary current loop: high-frequency transformer one and cyclic resonant commutation bidirectional converter→output filter circuit one; the role of the supercapacitor SC in this process is energy storage, filtering and voltage stabilization.

[0015] The MPPT supercapacitor energy storage DC grid-connected converter, the supercapacitor SC power grid-connected working mode: when the PV has no power output, the supercapacitor SC discharges and supplies power to the DC bus Usc. The transformer primary current loop in this process: Usc→bidirectional full-bridge converter→transformer primary winding→PV-; transformer secondary current loop: high-frequency transformer-circuit resonant commutation bidirectional converter→output filter circuit; the role of the supercapacitor SC in this process is to release energy.

[0016] The MPPT supercapacitor energy storage DC grid-connected converter, the grid charges the supercapacitor SC working mode: when the PV and the supercapacitor SC have no electrical energy, the grid charges the supercapacitor SC, the transformer secondary circuit: the grid voltage U850 passes through the output filter circuit 1 → high-frequency transformer and cyclic resonant commutation bidirectional converter → transformer secondary; the transformer primary current circuit: transformer primary winding → bidirectional full-bridge converter → supercapacitor SC; the supercapacitor SC is charged in this process.

[0017] The bidirectional full-bridge converter and the high-frequency transformer and the cyclic resonant commutation bidirectional converter have two control modes for grid connection:

[0018] Grid-connected control mode 1, resonant current positive half-wave, MOSFET switch tube 1 and MOSFET switch tube 4 of the bidirectional full-bridge converter are turned on, high-frequency transformer 1 and silicon carbide switch tube 1 of the cyclic resonant commutation bidirectional converter are turned on, the resonant inductor and the cyclic commutation resonant capacitor 1 and the cyclic commutation resonant capacitor 2 resonate, and the circuit of the transformer primary current i1 is: DC voltage Usc→MOSFET switch tube 1→transformer primary→MOSFET switch tube 4→Upv-; there are two circuits for the transformer secondary current ic1+ic2=i2, among which C1 is the cyclic commutation resonant capacitor and C2 is the cyclic commutation resonant capacitor, and the circuit of the current ic1 is: high-frequency transformer primary positive→resonant inductor→switch tube→cyclic commutation resonant capacitor→high-frequency transformer primary negative; the circuit of the current ic2 is: high-frequency transformer primary positive→resonant inductor→silicon carbide switch tube 1→output filter inductor→DC grid U850→cyclic commutation resonant capacitor 2→high-frequency transformer primary negative.

[0019] Grid-connected control mode two, resonant current negative half-wave, MOSFET switch tube three and MOSFET switch tube two of the bidirectional full-bridge converter are turned on, high-frequency transformer one and silicon carbide switch tube two of the cyclic resonant commutation bidirectional converter are turned on, the resonant inductor and the cyclic commutation resonant capacitor one and the cyclic commutation resonant capacitor two resonate, and the loop of the transformer primary current i1 is: DC voltage Usc→MOSFET switch tube three→transformer primary→MOSFET switch tube two→Upv-; there are two loops for the transformer secondary current ic1+ic2=i2, the loop of current ic1 is: high-frequency transformer primary positive→cyclic commutation resonant capacitor one→output filter inductor→DC grid U850→switch tube→resonant inductor→high-frequency transformer primary negative; the loop of current ic2 is: high-frequency transformer primary positive→cyclic commutation resonant capacitor→silicon carbide switch tube two→resonant inductor→high-frequency transformer primary negative.

[0020] The bidirectional full-bridge converter and the high-frequency transformer are a cyclic resonant commutation bidirectional converter, and the grid has two control modes for charging the supercapacitor SC:

[0021] Charging control mode one, resonant current positive half-wave, high-frequency transformer one and silicon carbide switch tube one of the cyclic resonant commutation bidirectional converter are turned on, the resonant inductor and the cyclic commutation resonant capacitor one and the cyclic commutation resonant capacitor two resonate, the MOSFET switch tube one and the MOSFET switch tube four of the bidirectional full-bridge converter are turned on, and the circuit of the transformer secondary current ic2 is: DC grid U850+→silicon carbide switch tube one→resonant inductor→high-frequency transformer primary→cyclic commutation resonant capacitor two→DC grid U850-; the circuit of the current ic1 is: high-frequency transformer primary lower negative→cyclic commutation resonant capacitor one→silicon carbide switch tube one→resonant inductor→high-frequency transformer primary upper positive, and the circuit of the transformer primary current i1 is: transformer primary upper positive→MOSFET switch tube one→DC voltage Usc→Upv-→MOSFET switch tube four→transformer primary lower negative.

[0022] Charging control mode two, resonant current negative half-wave, high-frequency transformer one and silicon carbide switch tube two of the cyclic resonant commutation bidirectional converter are turned on, the resonant inductor and the cyclic commutation resonant capacitor one and the cyclic commutation resonant capacitor two resonate, the MOSFET switch tube three and the MOSFET switch tube two of the bidirectional full-bridge converter are turned on, and the circuit of the transformer secondary current ic1 is: DC grid U850+→cyclic commutation resonant capacitor one→high-frequency transformer primary→resonant inductor→silicon carbide switch tube two→DC grid U850-; the circuit of the current ic2 is: high-frequency transformer primary lower positive→cyclic commutation resonant capacitor two→silicon carbide switch tube two→resonant inductor→high-frequency transformer primary upper negative, and the circuit of the transformer primary current i1 is: transformer primary lower positive→MOSFET switch tube three→DC voltage Usc→Upv-→MOSFET switch tube two→transformer primary upper negative.

[0023] The DC-DC boost transformer module, the main circuit includes an input filter circuit, a full-bridge bidirectional resonant converter, an intermediate frequency transformer and a resonant circuit, a full-bridge bidirectional converter, and an output filter circuit 2; the control includes low-voltage side voltage and current sampling, high-voltage side voltage and current sampling, PWM phase shift control, synchronous control, full-bridge bidirectional resonant converter control, and full-bridge bidirectional grid-connected converter control. The full-bridge bidirectional resonant converter is composed of switch tube 1, switch tube 2, switch tube 3, and switch tube 4; the intermediate frequency transformer and the resonant circuit are composed of high-frequency transformer 2, a resonant inductor, and a resonant capacitor; the full-bridge bidirectional converter is composed of switch tube 5, switch tube 6, switch tube 7, and switch tube 8; m modules are combined in series and parallel through input and output to form a DC transformer with the required input and output voltage levels.

[0024] The PV-850V-10KV / 10MW photovoltaic power station system includes 25,000 unit PV modules + MPPT supercapacitor energy storage DC grid-connected converter, which is connected to the 850V DC grid, and three DC-DC step-up transformer modules, which are connected in parallel on the 850V low voltage side and in series on the 10KV high voltage side to form a DC step-up transformer.

[0025] Twenty-five thousand of the unit PV modules + MPPT supercapacitor energy storage DC grid-connected converter 1000 are connected to the 850V DC grid, the standard voltage of the PV modules is 48V / 400W, the switch tube nine, MOSFET switch tube one, MOSFET switch tube two, MOSFET switch tube three, and MOSFET switch tube four use 100V / 100A MOSFETs, and the silicon carbide switch tube one and silicon carbide switch tube two use 1700V / 3A silicon carbide transistors.

[0026] The DC transformer composed of three DC-DC step-up transformer modules has a low-voltage side of 850V, and a power of 10MW requires a current of 11765A. Three modules are connected in parallel at a low voltage, and each module has an input current of 3922A. The full-bridge bidirectional resonant converter is composed of switch tube one, switch tube two, switch tube three, switch tube four), switch tube ten, switch tube eleven, switch tube twelve and switch tube thirteen. Among them, switch tube one and switch tube two are connected in parallel, switch tube three and switch tube four are connected in parallel, switch tube ten and switch tube eleven are connected in parallel, switch tube twelve and switch tube thirteen are connected in parallel, and each switch tube requires a current of 1960A. An IGBT with a rated voltage of 1700V and a rated current of 3600A can be selected; the high-voltage side has a power of 10MW and a voltage of 10KV, which requires a current of 1000A. Three modules are connected in series, and each module requires a current of The voltage is 3.334KV and the current is 1000A. The full-bridge bidirectional converter is composed of switch tube five, switch tube six, switch tube seven, switch tube eight, switch tube fourteen, switch tube fifteen, switch tube sixteen and switch tube seventeen. Among them, switch tube five is connected in parallel with switch tube six, switch tube seven is connected in parallel with switch tube eight, switch tube fourteen is connected in parallel with switch tube fifteen, switch tube sixteen is connected in parallel with switch tube seventeen, each switch tube requires a current of 500A, and a 6.5KV / 1000A IGBT can be selected; the switching time of the 6.5KV / 1000A IGBT is 12us, the switching frequency of the full-bridge bidirectional resonant converter and the full-bridge bidirectional converter can adopt a medium frequency of 1 to 2KHz, the high-frequency transformer two can adopt a medium frequency 1 to 2KHz transformer design, and the resonant frequency of the resonant circuit composed of the resonant inductor and the resonant capacitor is 1 to 2KHz.

[0027] Beneficial effects of the present invention:

[0028] The photovoltaic power station DC grid conversion system is used to resolve the constraints of the AC grid on large-scale photovoltaic power stations; the use of supercapacitor energy storage solves the problem of greatly reduced efficiency of lead-acid batteries under cold outdoor conditions; a PV module + MPPT supercapacitor energy storage DC grid-connected converter is used to form an independent unit to improve system reliability and overall efficiency; a circulating resonant commutation bidirectional converter composed of two switching tubes and two circulating commutation resonant capacitors is used to reduce the number of switches. At the same time, the circulating resonant commutation bidirectional converter and the bidirectional full-bridge converter on the input side realize synchronous resonance control, realizing complete soft switching. In addition, the sum of the voltages on the circulating commutation resonant capacitor 1 and the circulating commutation resonant capacitor 2 in the circulating commutation resonance does not exceed the DC grid voltage on the low-voltage side; a DC-DC step-up transformer is formed by high-voltage and high-current IGBTs and resonant working mode to reduce the number of switching tubes and realize complete soft switching. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a block diagram of the photovoltaic power station energy storage type DC grid conversion system of the present invention;

[0030] Figure 2 This is the circuit diagram of the PV module + MPPT supercapacitor energy storage DC grid-connected converter of the present invention;

[0031] Figure 3 The circuit diagram of the DC-DC boost transformer assembly of the present invention;

[0032] Figure 4 This is a block diagram of the PV-850V-10KV / 10MW photovoltaic power station system of the present invention;

[0033] Figure 5 This is the grid-connected circuit diagram of the 25,000-unit PV module + MPPT supercapacitor energy storage DC grid-connected converter of the present invention;

[0034] Figure 6 The figure is a circuit diagram of a 850V-10KV / 10MW DC / DC step-up transformer according to the present invention. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0036] A photovoltaic power station energy storage type DC grid conversion system, including a PV component + MPPT super capacitor energy storage DC grid-connected converter, the voltage of the solar photovoltaic cell PV component is connected to the low voltage DC grid through the MPPT maximum power tracking control, super capacitor energy storage, MOSFET switch tube to form a bidirectional full-bridge conversion circuit, a high-frequency transformer 1031 composed of two silicon carbide switch tubes and two circulating commutation resonant capacitors and a circulating resonant commutation bidirectional converter; a DC-DC boost transformer module 2000, the low voltage DC voltage is connected to the low voltage DC grid through the full-bridge bidirectional resonant converter, the medium The frequency transformer and resonant circuit, and the high-voltage side full-bridge bidirectional converter are used to boost the voltage to a medium-voltage DC voltage. The DC transformer with the required input and output voltage levels is composed of m modules through input and output series-parallel combination; the PV-850V-10KV / 10MW photovoltaic power station system consists of 25,000 unit PV components + MPPT supercapacitor energy storage DC grid-connected converter 1000, which is connected to the 850V DC grid. It consists of three DC-DC boost transformer modules 2000, which are connected in parallel on the 850V low-voltage side and in series on the 10KV high-voltage side to form a DC boost transformer.

[0037] like Figure 1 As shown, a photovoltaic power station energy storage type DC grid conversion system includes a PV component + MPPT super capacitor energy storage DC grid-connected converter 1000, a DC-DC boost transformer module 2000, and n units of PV components + MPPT super capacitor energy storage DC grid-connected converters 1000 are connected to the low voltage DC grid, and m modules are combined through input and output series and parallel connections to form a DC transformer with the required input and output voltage levels.

[0038] Further Figure 2 As shown, the PV component + MPPT super capacitor energy storage DC grid-connected converter 1000 includes a main circuit and grid-connected control. The main circuit includes a PV component, a Boost converter 1010, a super capacitor SC1015, a bidirectional full-bridge converter 1020, a high-frequency transformer 1031 and a cyclic resonant commutation bidirectional converter 1030, and an output filter circuit 1040; the grid-connected control includes PV voltage and current sampling 1050, MPPT control 1060, grid voltage and current sampling 1070, PWM phase shift control 1080, synchronous control 1090, bidirectional full-bridge converter control 1100, and cyclic resonant commutation bidirectional converter control 1110.

[0039] Boost converter 1010, including switch tube nine 1011, diode 1012, boost inductor 1013, filter capacitor one 1014, wherein switch tube nine 1011, diode 1012, boost inductor 1013 constitute a Boost boost DC / DC converter; super capacitor SC1015, composed of super capacitor modules for energy storage and voltage stabilization; bidirectional full-bridge converter 1020, including MOSFET switch tube one 1021, MOSFET switch tube two 1022, MOSFET switch tube three 1023, MOSFET switch tube four 1024 constitute a bidirectional full-bridge conversion circuit; high frequency transformer one 1031 and cyclic resonant commutation bidirectional The converter 1030 includes a high-frequency transformer 1 1031, a resonant inductor 1032, a circulating commutation resonant capacitor 1 1033, a circulating commutation resonant capacitor 2 1034, a silicon carbide switch tube 1 1035, and a silicon carbide switch tube 2 1036, wherein the circulating commutation resonant capacitor 1 1033, the circulating commutation resonant capacitor 2 1034 and the resonant inductor 1032 participate in resonance, and the circulating commutation resonant capacitor 1 1033, the circulating commutation resonant capacitor 2 1034 and the silicon carbide switch tube 1 1035, and the silicon carbide switch tube 2 1036 form a cyclic converter; the output filter circuit 140 includes a filter capacitor 2 1041, a filter capacitor 3 1042, and a common-mode filter inductor 1043.

[0040] The high-frequency transformer 1031 and the circulating resonant commutation bidirectional converter 1030 are composed of a resonant inductor 1032, a circulating commutation resonant capacitor 1033, a circulating commutation resonant capacitor 2 1034 and two silicon carbide switch tubes 1 1035 and 1036 to form a circulating resonant circuit. In the circulating commutation resonance, the sum of the voltages on the circulating commutation resonant capacitor 1 1033 and the circulating commutation resonant capacitor 2 1034 does not exceed the voltage of the low-voltage DC grid. The connection polarities of the silicon carbide switch tube 1 1035 and the silicon carbide switch tube 2 1036 are opposite, wherein the S pole of the silicon carbide switch tube 1 1035 is connected to the resonant inductor 1032, and the D pole is connected to the circulating commutation resonant capacitor 1 1033 and the output filter inductor 1043; the D pole of the silicon carbide switch tube 2 1036 is connected to the resonant inductor 1032, and the S pole is connected to the circulating commutation resonant capacitor 2 1034 and the output port U850-.

[0041] The grid-connected control of the MPPT supercapacitor energy storage DC grid-connected converter includes PV voltage and current sampling 1050, which is used to collect the voltage of the PV photovoltaic module and the current during the working process, MPPT control 1060, which performs maximum power tracking control according to the voltage of the PV photovoltaic module and the current during the working process, grid voltage and current sampling 1070, which is used to collect the voltage of the DC grid and the output current of the grid-connected converter, PWM phase shift control 1080, which performs PWM phase shift control calculation according to the MPPT control 1060 and the grid voltage and current sampling 1070 values, and synchronous control 1090, which synchronously controls the two units of the bidirectional full-bridge converter control 1100 and the cyclic resonant commutation bidirectional converter control 1110 according to the PWM phase shift control calculation result, so as to realize the synchronous resonant cyclic commutation of the bidirectional full-bridge converter 1020 and the cyclic resonant commutation bidirectional converter 1030.

[0042] The MPPT supercapacitor energy storage DC grid-connected converter 1000 has three working modes: PV module power grid-connected working mode, supercapacitor SC1015 power grid-connected working mode, and grid charging supercapacitor SC1015 working mode.

[0043] PV module power grid-connected working mode: Boost converter 1010 is controlled by MPPT. When switch tube nine 1011 is turned on, boost inductor 1013 stores energy. The current loop of this process is: PV module UPV+→boost inductor 113→switch tube nine 1011→PV module UPV-; when switch tube switch tube nine is turned off, diode 1012 is turned on to charge super capacitor SC1015 and supply power to DC bus Usc. The primary current loop of high-frequency transformer 1031 in this process is: photovoltaic cell module UPV+→boost inductor 1013→diode 1012→Usc→bidirectional full-bridge converter 1020→primary winding of high-frequency transformer 1031→PV module PV-; secondary current loop of high-frequency transformer 1031: high-frequency transformer 1031 and cyclic resonant commutation bidirectional converter 1030→output filter circuit 1040; the role of super capacitor SC1015 in this process is energy storage, filtering and voltage stabilization.

[0044] The grid-connected working mode of supercapacitor SC1015: When PV has no power output, supercapacitor SC1015 discharges and supplies power to the DC bus Usc. In this process, the primary current loop of high-frequency transformer 1031 is: Usc→bidirectional full-bridge converter 1020→primary winding of high-frequency transformer 1031→PV-; secondary current loop of high-frequency transformer 1031 is: high-frequency transformer 1031 and cyclic resonant commutation bidirectional converter 1030→output filter circuit 1040; the role of supercapacitor SC1015 in this process is to release energy.

[0045] The grid charges the supercapacitor SC in working mode: when there is no power in PV and supercapacitor SC1015, the grid charges the supercapacitor SC, transformer secondary circuit: grid voltage U850 passes through output filter circuit 1040 → high-frequency transformer and circulating resonant commutation bidirectional converter 1030 → high-frequency transformer 1031 secondary; high-frequency transformer 1031 primary current circuit: high-frequency transformer 1031 primary winding → bidirectional full-bridge converter 1020 → supercapacitor SC1015; supercapacitor SC1015 is charged in this process.

[0046] The bidirectional full-bridge converter 1020, the high-frequency transformer 1031 and the cyclic resonant commutation bidirectional converter 1030 have two control modes for grid connection:

[0047] Grid-connected control mode 1, resonant current positive half-wave, MOSFET switch tube 1 1021 and MOSFET switch tube 4 1024 of bidirectional full-bridge converter 1020 are turned on, high-frequency transformer 1 1031 and switch tube silicon carbide switch tube 1 of cyclic resonant commutation bidirectional converter 1030 are turned on, resonant inductor 1032 and cyclic commutation resonant capacitor 1 1033 and cyclic commutation resonant capacitor 2 1034 resonate, and the loop of transformer primary current i1 is: DC voltage Usc→MOSFET switch tube 1 1021→transformer primary→MOSFET switch tube 4 1024→Upv-; transformer secondary current ic1+ There are two circuits of ic2=i2, among which C1 is the circulating commutation resonant capacitor 1033, C2 is the circulating commutation resonant capacitor 1034, and the circuit of current ic1 is: positive on the secondary of high-frequency transformer → resonant inductor 1032 → silicon carbide switch tube 1035 → circulating commutation resonant capacitor 1033 → negative on the secondary of high-frequency transformer 1031; the circuit of current ic2 is: positive on the secondary of high-frequency transformer 1031 → resonant inductor 1032 → silicon carbide switch tube 1035 → output filter inductor 1043 → DC grid U850 → circulating commutation resonant capacitor 1034 → negative on the secondary of high-frequency transformer 1031.

[0048] In the grid-connected control mode 2, the resonant current has a negative half-wave. The MOSFET switch tube 3 1023 and the MOSFET switch tube 2 1022 of the bidirectional full-bridge converter 1020 are turned on. The high-frequency transformer 1 1031 and the switch tube silicon carbide switch tube 2 of the cyclic resonant commutation bidirectional converter 1030 are turned on. The resonant inductor 1032 resonates with the cyclic commutation resonant capacitor 1 1033 and the cyclic commutation resonant capacitor 2 1034. The circuit of the transformer primary current i1 is: DC voltage Usc→MOSFET switch tube 3 1023→transformer primary→MOSFET switch tube 2 1022→U pv-; There are two circuits for the transformer secondary current ic1+ic2=i2. The circuit of the current ic1 is: the positive side of the secondary of the high-frequency transformer 1031 → the circulating commutation resonant capacitor 1033 → the output filter inductor 1043 → the DC power grid U850 → the silicon carbide switching tube 1036 → the resonant inductor 1032 → the negative side of the secondary of the high-frequency transformer 1031; the circuit of the current ic2 is: the positive side of the secondary of the high-frequency transformer 1031 → the circulating commutation resonant capacitor 1034 → the silicon carbide switching tube 1036 → the resonant inductor 1032 → the negative side of the secondary of the high-frequency transformer 1031.

[0049] There are two control modes for the grid to charge the supercapacitor SC:

[0050] Charging control mode one, resonant current positive half-wave, high-frequency transformer one 1031 and silicon carbide switch tube one 1035 of the circulating resonant commutation bidirectional converter 1030 are turned on, the resonant inductor 1032 and the circulating commutation resonant capacitor one 1033 and the circulating commutation resonant capacitor two 1034 resonate, the MOSFET switch tube one 1021 and the MOSFET switch tube four 1024 of the bidirectional full-bridge converter 1020 are turned on, and the circuit of the transformer secondary current ic2 is: DC grid U850+→silicon carbide switch tube one 1035→resonant inductor 1032→secondary of high-frequency transformer one 1031→circulating commutation resonant capacitor two 1034→DC grid U850-; the circuit of the current ic1 is: negative lower side of the secondary of high-frequency transformer one 1031→circulating commutation resonant capacitor one 1033→silicon carbide switch tube one 1035→resonant inductor 1032→positive upper side of the secondary of high-frequency transformer one 1031. The circuit of the transformer primary current i1 is: the upper positive of the transformer primary → MOSFET switch tube 1 1021 → DC voltage Usc → Upv- → MOSFET switch tube 4 1024 → the lower negative of the transformer primary.

[0051] In charging control mode two, the resonant current is in the negative half-wave. The high-frequency transformer 1031 and the silicon carbide switch tube 2 1036 of the circulating resonant commutation bidirectional converter 1030 are turned on. The resonant inductor 1032 resonates with the circulating commutation resonant capacitor 1033 and the circulating commutation resonant capacitor 2 1034. The MOSFET switch tube 3 1023 and the MOSFET switch tube 2 1022 of the bidirectional full-bridge converter 1020 are turned on. The loop of the transformer secondary current ic1 is: DC grid U850+→circulating commutation resonant capacitor 1033→secondary of high-frequency transformer 1031→resonant inductor 1032→silicon carbide switch tube 2 1036→DC grid U850-; the loop of the current ic2 is: positive at the lower secondary of high-frequency transformer 1031→circulating commutation resonant capacitor 1034→silicon carbide switch tube 2 1036→resonant inductor 1032→negative at the upper secondary of high-frequency transformer 1031. The circuit of the transformer primary current i1 is: transformer primary lower positive → MOSFET switch tube three 1023 → DC voltage Usc → Upv- → MOSFET switch tube two 1022 → transformer primary upper negative.

[0052] Further Figure 3 As shown, the DC-DC boost transformer module 2000, the main circuit includes an input filter circuit 2010, a full-bridge bidirectional resonant converter 2020, a medium frequency transformer and a resonant circuit 2030, a full-bridge bidirectional converter 2040, and an output filter circuit 2050; the control includes low-voltage side voltage and current sampling 2060, high-voltage side voltage and current sampling 2070, PWM phase shift control 2080, synchronous control 2090, full-bridge bidirectional resonant converter control 2100, and full-bridge bidirectional grid-connected converter control 2110. The full-bridge bidirectional resonant converter 2020 is composed of a switch tube 1 2021, a switch tube 2 2022, a switch tube 3 2023, and a switch tube 4 2024; the intermediate frequency transformer and resonant circuit 2030 is composed of a high frequency transformer 2 2031, a resonant inductor 2032, and a resonant capacitor 2033; the full-bridge bidirectional converter 2040 is composed of a switch tube 5 2041, a switch tube 6 2042, a switch tube 7 2043, and a switch tube 8 2044.

[0053] Further Figure 4 As shown, the PV-850V-10KV / 10MW photovoltaic power station system, 25,000 unit PV panels + MPPT supercapacitor energy storage DC grid-connected converter 1000, connected to the 850V DC grid, three DC-DC step-up transformer modules 2000, connected in parallel on the 850V low voltage side and in series on the 10KV high voltage side, form a DC step-up transformer.

[0054] Further Figure 5As shown, 25,000 PV modules + MPPT supercapacitor energy storage DC grid-connected converter 1000 is connected to 850V DC grid. The standard voltage of PV modules is 48V / 400W, switch tube nine 1011, MOSFET switch tube one 1021, MOSFET switch tube two 1022, MOSFET switch tube three 1023, MOSFET switch tube four 1024 use 100V / 100A MOSFET, and silicon carbide switch tube one 1035 and silicon carbide switch tube two 1036 use 1700V / 3A silicon carbide transistors.

[0055] Further Figure 6 As shown, the 10MW DC / DC step-up transformer is composed of three DC-DC step-up transformer modules 2000, 850V low voltage measurement, 10MW power requires 11765A current, three modules are connected in parallel at low voltage measurement, each module has an input current of 3922A, and the full-bridge bidirectional resonant converter 2020 is composed of switch tube 1 2021, switch tube 2 2022, switch tube 3 2023, switch tube 4 2024, switch tube 10 2025, switch tube 11 2026, switch tube 12 2027 and switch tube 13 2028, wherein the switch Switch tube 1 2021 and switch tube 2 2022 are connected in parallel, switch tube 3 2023 and switch tube 4 2024 are connected in parallel, switch tube 10 2025 and switch tube 11 2026 are connected in parallel, switch tube 12 2027 and switch tube 13 2028 are connected in parallel, each switch tube requires 1960A current, and IGBT manufacturers such as Infineon with rated voltage of 1700V and rated current of 3600A can be selected; 10MW power on the high-voltage side, voltage of 10KV requires 1000A current, three modules are connected in series, and each module requires a voltage of 3.334 KV, current 1000A, full-bridge bidirectional converter 2040 is composed of switch tube 5 2041, switch tube 6 2042, switch tube 7 2043, switch tube 8 2044, switch tube 14 2045, switch tube 15 2046, switch tube 16 2047 and switch tube 17 2048, wherein switch tube 5 2041 and switch tube 6 2042 are connected in parallel, switch tube 7 2043 and switch tube 8 2044 are connected in parallel, switch tube 14 2045 and switch tube 15 2046 are connected in parallel, switch tube 16 2047 and switch tube 10 are connected in parallel, Seven 2048 are connected in parallel, each switch tube requires 500A current, and 6.5KV / 1000A IGBT manufacturers such as Infineon can be selected; the switching time of 6.5KV / 1000A IGBT is 12us, the switching frequency of the full-bridge bidirectional resonant converter 2020 and the full-bridge bidirectional converter 2040 can be 1~2KHz, the high-frequency transformer 2031 can be designed with a medium frequency 1~2KHz transformer, and the resonant frequency of the resonant circuit composed of the resonant inductor 2032 and the resonant capacitor 2033 is 1~2KHz.

[0056] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A photovoltaic power station energy storage type DC grid conversion system, characterized in that: include: PV module + MPPT supercapacitor energy storage DC grid-connected converter (1000), DC-DC step-up transformer module (2000), PV-850V-10KV / 10MW photovoltaic power station system; The PV component + MPPT super capacitor energy storage DC grid-connected converter (1000) comprises a main circuit and grid-connected control, wherein the main circuit comprises a PV component, a Boost converter (1010), a super capacitor SC (1015), a bidirectional full-bridge converter (1020), a high-frequency transformer (1031) and a cyclic resonant commutation bidirectional converter (1030), and an output filter circuit (1040); the grid-connected control comprises PV voltage and current sampling (1050), MPPT control (1060), grid voltage and current sampling (1070), PWM phase shift control (1080), synchronization control (1090), bidirectional full-bridge converter control (1100), and cyclic resonant commutation bidirectional converter control (1110); The MPPT supercapacitor energy storage DC grid-connected converter grid-connected control includes PV voltage and current sampling (1050), MPPT control (1060), PWM phase shift control (1080), synchronization control (1090), bidirectional full-bridge converter control (1100) and cyclic resonant commutation bidirectional converter control; The DC-DC boost transformer module (2000) has a main circuit including an input filter circuit (2010), a full-bridge bidirectional resonant converter (2020), an intermediate frequency transformer and a resonant circuit (2030), a full-bridge bidirectional converter (2040), and an output filter circuit 2 (2050); the control includes low-voltage side voltage and current sampling (2060), high-voltage side voltage and current sampling (2070), PWM phase shift control (2080), synchronization control (2090), full-bridge bidirectional resonant converter control (2100), full-bridge bidirectional grid-connected converter control (2110), and the full-bridge bidirectional resonant converter (2110) is connected to the inverter. 2020), which is composed of switch tube one (2021), switch tube two (2022), switch tube three (2023), and switch tube four (2024); the intermediate frequency transformer and resonant circuit (2030), which is composed of high frequency transformer two (2031), resonant inductor (2032), and resonant capacitor (2033); the full-bridge bidirectional converter (2040), which is composed of switch tube five (2041), switch tube six (2042), switch tube seven (2043), and switch tube eight (2044); and a DC transformer with required input and output voltage levels is formed by combining m modules in series and parallel through input and output.

2. A photovoltaic power station energy storage type DC grid conversion system according to claim 1, characterized in that: The Boost converter (1010) comprises a switch tube nine (1011), a diode (1012), a boost inductor (1013), and a filter capacitor one (1014), wherein the switch tube nine (1011), the diode (1012), and the boost inductor (1013) form a Boost boost DC / DC converter; the super capacitor SC (1015) is composed of a super capacitor module and is used for energy storage and voltage stabilization; the bidirectional full-bridge converter (1020) comprises a MOSFET switch tube one (1021), a MOSFET switch tube two (1022), a MOSFET switch tube three (1023), and a MOSFET switch tube four (1024) to form a bidirectional full-bridge conversion circuit; the high-frequency transformer one (1031) and the cyclic resonant commutation bidirectional transformer The converter (1030) comprises a high frequency transformer 1 (1031), a resonant inductor (1032), a circulating commutation resonant capacitor 1 (1033), a circulating commutation resonant capacitor 2 (1034), a silicon carbide switch tube 1 (1035), and a silicon carbide switch tube 2 (1036), wherein the circulating commutation resonant capacitor 1 (1033), the circulating commutation resonant capacitor 2 (1034) and the resonant inductor (1032) participate in resonance, and the circulating commutation resonant capacitor 1 (1033), the circulating commutation resonant capacitor 2 (1034) and the silicon carbide switch tube 1 (1035), and the silicon carbide switch tube 2 (1036) form a circulating converter; the output filter circuit 1 (1040) comprises a filter capacitor 2 (1041), a filter capacitor 3 (1042), and a common mode filter inductor (1043); The high-frequency transformer 1 (1031) and the circulating resonant commutation bidirectional converter (1030) are composed of a resonant inductor (1032), a circulating commutation resonant capacitor 1 (1033), a circulating commutation resonant capacitor 2 (1034), a silicon carbide switch tube 1 (1035), and a silicon carbide switch tube 2 (1036) to form a circulating resonant circuit. The sum of the voltages on the circulating commutation resonant capacitor 1 (1033) and the circulating commutation resonant capacitor 2 (1034) in the circulating commutation resonance does not exceed the low voltage DC measurement voltage. The grid voltage, the connection polarities of silicon carbide switch tube 1 (1035) and silicon carbide switch tube 2 (1036) are opposite, wherein the S pole of silicon carbide switch tube 1 (1035) is connected to the resonant inductor (1032), and the D pole is connected to the circulating commutation resonant capacitor 1 (1033) and the output filter inductor (1043); the D pole of silicon carbide switch tube 2 (1036) is connected to the resonant inductor (1032), and the S pole is connected to the circulating commutation resonant capacitor 2 (1034) and the output port U850-.

3. A photovoltaic power station energy storage type DC grid conversion system according to claim 2, characterized in that: The MPPT supercapacitor energy storage DC grid-connected converter (1000) has three working modes: a PV module power grid-connected working mode, a supercapacitor SC (1015) power grid-connected working mode, and a grid charging supercapacitor SC (1015) working mode; PV module power grid-connected working mode: Boost converter (1010) is controlled by MPPT. When switch tube nine (1011) is turned on, boost inductor (1013) stores energy. When switch tube nine (1011) is turned off, diode (1012) is turned on to charge super capacitor SC (1015) and supply power to DC bus Usc. The role of super capacitor SC (1015) in this process is energy storage, filtering and voltage stabilization. The supercapacitor SC (1015) power grid-connected working mode: when the PV has no power output, the supercapacitor SC (1015) discharges and supplies power to the DC bus Usc. The role of the supercapacitor SC (1015) in this process is to release energy; The grid charges the supercapacitor SC (1015) in working mode: when neither the PV nor the supercapacitor SC (1015) has power, the grid charges the supercapacitor SC (1015), and the supercapacitor SC (1015) is charged in this process.

4. A photovoltaic power station energy storage type DC grid conversion system according to claim 2, characterized in that: The bidirectional full-bridge converter (1020), the high-frequency transformer 1 (1031), and the cyclic resonant commutation bidirectional converter (1030) have two control modes for grid connection: Grid-connected control mode 1, resonant current positive half-wave, MOSFET switch tube 1 (1021) and MOSFET switch tube 4 (1024) of the bidirectional full-bridge converter (1020) are turned on, high-frequency transformer 1 (1031) and silicon carbide switch tube 1 (1035) of the circulating resonant commutation bidirectional converter (1030) are turned on, and the resonant inductor (1032) and the circulating commutation resonant capacitor 1 (1033) and the circulating commutation resonant capacitor 2 (1034) resonate; In the grid-connected control mode 2, the resonant current has a negative half-wave, the MOSFET switch tube 3 (1023) and the MOSFET switch tube 2 (1022) of the bidirectional full-bridge converter (1020) are turned on, the high-frequency transformer 1 (1031) and the silicon carbide switch tube 2 (1036) of the circulating resonant commutation bidirectional converter (1030) are turned on, and the resonant inductor (1032) resonates with the circulating commutation resonant capacitor 1 (1033) and the circulating commutation resonant capacitor 2 (1034).

5. A photovoltaic power station energy storage type DC grid conversion system according to claim 2, characterized in that: The bidirectional full-bridge converter (1020), the high-frequency transformer 1 (1031), and the cyclic resonant commutation bidirectional converter (1030) have two control modes for the power grid to charge the super capacitor SC (1015); Charging control mode 1, resonant current positive half wave, high frequency transformer 1 (1031) and silicon carbide switch tube 1 (1035) of the circulating resonant commutation bidirectional converter (1030) are turned on, the resonant inductor (1032) and the circulating commutation resonant capacitor 1 (1033) and the circulating commutation resonant capacitor 2 (1034) resonate, the MOSFET switch tube 1 (1021) and MOSFET switch tube 4 (1024) of the bidirectional full-bridge converter (1020) are turned on, and the low voltage DC grid charges the super capacitor SC (1015); In charging control mode 2, the resonant current has a negative half-wave, the high-frequency transformer 1 (1031) and the silicon carbide switch tube 2 (1036) of the circulating resonant commutation bidirectional converter (1030) are turned on, the resonant inductor (1032) and the circulating commutation resonant capacitor 1 (1033) and the circulating commutation resonant capacitor 2 (1034) resonate, the MOSFET switch tube 3 (1023) and the MOSFET switch tube 2 (1022) of the bidirectional full-bridge converter (1020) are turned on, and the low-voltage DC power grid charges the supercapacitor SC (1015).

6. A photovoltaic power station energy storage type DC grid conversion system according to claim 1, characterized in that the PV-850V-10KV / 10MW photovoltaic power station system comprises 25,000 unit PV components + MPPT supercapacitor energy storage DC grid-connected converter (1000), which is grid-connected to the 850V DC grid, and three DC-DC step-up transformer modules (2000), which are connected in parallel at the 850V low voltage side and in series at the 10KV high voltage side to form a DC transformer; Twenty-five thousand of the unit PV modules + MPPT supercapacitor energy storage DC grid-connected converters (1000) are connected to an 850V DC grid, the standard voltage of the PV modules is 48V / 400W, the switch tube nine (1011), the MOSFET switch tube one (1021), the MOSFET switch tube two (1022), the MOSFET switch tube three (1023), and the MOSFET switch tube four (1024) are 100V / 100A MOSFETs, and the silicon carbide switch tube one (1035) and the silicon carbide switch tube two (1036) are 1700V / 3A silicon carbide transistors; The DC transformer composed of three DC-DC step-up transformer modules (2000) has an 850V low-voltage side, and 10MW power requires 11765A current. Three modules are connected in parallel at a low voltage, and each module has an input current of 3922A. The full-bridge bidirectional resonant converter (2020) is composed of a switch tube 1 (2021), a switch tube 2 (2022), a switch tube 3 (2023), a switch tube 4 (2024), a switch tube 10 (2025), and a switch tube 11. The invention is composed of switch tube 1 (2021) and switch tube 2 (2022) in parallel, switch tube 3 (2023) and switch tube 4 (2024) in parallel, switch tube 10 (2025) and switch tube 11 (2026) in parallel, switch tube 12 (2027) and switch tube 13 (2028) in parallel, each switch tube requires 1960A current, and the rated voltage can be 1700A. V IGBT with a rated current of 3600A; 10MW power on the high-voltage side, a voltage of 10KV requires a current of 1000A, three modules are connected in series, each module requires a voltage of 3.334KV and a current of 1000A, and the full-bridge bidirectional converter (2040) consists of switch tube five (2041), switch tube six (2042), switch tube seven (2043), switch tube eight (2044), switch tube fourteen (2045), switch tube fifteen (2046), switch The switch tube 16 (2047) and the switch tube 17 (2048) are composed of switch tube 5 (2041) and switch tube 6 (2042) in parallel, switch tube 7 (2043) and switch tube 8 (2044) in parallel, switch tube 14 (2045) and switch tube 15 (2046) in parallel, switch tube 16 (2047) and switch tube 17 (2048) in parallel, each switch tube requires 500A current, and a 6.5KV / 1000A IGBT can be selected; The switching time of the 6.5KV / 1000A IGBT is 12us, and the switching frequency of the full-bridge bidirectional resonant converter (2020) and the full-bridge bidirectional converter (2040) can adopt a medium frequency of 1 to 2KHz.

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