Vrf energy storage system

Abstract

The application provides a VRF energy storage system, comprising: a power supply for supplying power to the VRF energy storage system; a rectifier circuit for converting alternating current of the power supply into direct current; an inverter circuit, an input end of which is connected with the rectifier circuit, and an output end of which is configured to be connected with a load; an isolated DC-DC conversion circuit, a first end of which is connected with a direct current voltage output end of the inverter circuit; and a battery, which is connected with a second end of the isolated DC-DC conversion circuit. In this way, the VRF energy storage system separates the VRF main control panel side from the battery side, reduces the electrical risk and safety risk in the circuit, and improves the safety of the VRF energy storage system during use.

Description

Technical Field

[0001] This application relates to the field of energy storage system technology, and specifically to a VRF (Variable Refrigerant Flow) energy storage system. Background Technology

[0002] In air conditioning systems, traditional energy storage solutions employ non-isolated bidirectional buck and boost circuits, meaning both voltage boosting and bucking occur within the same circuit. This topology offers advantages such as circuit simplicity and ease of control. The VRF main control board of the air conditioning system is connected to the battery via a DC-DC converter. However, due to the non-isolated nature of the energy storage circuit, there are electrical safety risks between the VRF main control board and the DC-DC converter, and this topology also results in low energy storage efficiency. Summary of the Invention

[0003] To address the above issues, this application provides a VRF energy storage system that can at least solve some of the problems of the prior art.

[0004] This application provides a VRF energy storage system, including: a power supply for supplying power to the VRF energy storage system; a rectifier circuit for converting AC power from the power supply into DC power; an inverter circuit with its input terminal connected to the rectifier circuit and its output terminal configured for connecting a load; an isolated DC-DC conversion circuit with its first terminal connected to the DC voltage output terminal of the inverter circuit; and a battery connected to the second terminal of the isolated DC-DC conversion circuit.

[0005] By using the above methods, the isolated DC-DC conversion circuit separates the VRF main control board side from the battery side, reducing the electrical and safety risks of the circuit and improving the safety of the VRF energy storage system during use.

[0006] Optionally, the isolated DC-DC converter circuit includes: a first switching circuit, with its first terminal connected to the DC voltage output terminal, its second terminal connected to the first terminal of the LLC resonant circuit, the second terminal of the LLC resonant circuit connected to the first terminal of the second switching circuit, and the second terminal of the second switching circuit connected to the battery.

[0007] By means of the above method, an LLC resonant circuit is set between the first and second switching circuits. When the VRF energy storage system is in power output mode, the voltage output from the DC voltage output terminal is used as the charging voltage on the battery side. That is, power is supplied to the battery side through the first switching circuit and LLC resonant circuit connected to the DC voltage output terminal. When the VRF energy storage system is in energy feedback mode, the energy of the battery is fed back to the DC voltage output terminal. The battery side supplies power to the DC voltage output terminal through the second switching circuit and LLC resonant circuit. The design of the isolated DC-DC conversion circuit is realized through a simple circuit structure, and electrical isolation between the battery side and the VRF main control board is achieved in a way that is easy to implement and has low manufacturing cost.

[0008] Optionally, the first switching circuit includes a first H-bridge IGBT composed of a first IGBT (Insulated Gate Bipolar Transistor), a second IGBT, a third IGBT, and a fourth IGBT.

[0009] By employing the above method, four IGBT switching elements are configured to form the first H-bridge IGBT. Through high-frequency switching of these four switching elements, the DC voltage output from the DC voltage terminal is converted into a high-frequency AC voltage. Simultaneously, the low conduction losses of the IGBT switching elements are beneficial for improving the operating efficiency of the VRF energy storage system in power output mode.

[0010] Optionally, the second switching circuit includes a second H-bridge IGBT composed of a fifth IGBT, a sixth IGBT, a seventh IGBT, and an eighth IGBT.

[0011] By employing the above method, four IGBT switching elements are configured to form a second H-bridge IGBT. Through high-frequency switching of these four elements, the DC voltage output from the battery side is converted into a high-frequency AC voltage. Simultaneously, the low conduction losses of the IGBT switching elements are beneficial for improving the operating efficiency of the VRF energy storage system in energy feedback mode.

[0012] Optionally, the LLC resonant circuit includes a first inductor, a second inductor, a first capacitor, a second capacitor, and a transformer. The first end of the first inductor and the first end of the first capacitor are connected to the second end of the first switching circuit. The second end of the first inductor and the second end of the first capacitor are connected to the first end of the transformer. The first end of the second inductor and the first end of the second capacitor are connected to the second end of the transformer. The second end of the second inductor and the second end of the second capacitor are connected to the first end of the second switching circuit.

[0013] In the above manner, in power output mode, the LLC resonant circuit and transformer perform energy transfer and voltage conversion on the AC voltage output after high-frequency switching of the first switching circuit, and rectify it to supply power to the battery section. In energy feedback mode, the LLC resonant circuit and transformer perform energy transfer and voltage conversion on the AC voltage output after high-frequency switching of the second switching circuit, and rectify it to supply power to the DC voltage output side.

[0014] Optionally, the rectifier circuit is a rectifier bridge.

[0015] By using the above methods, AC power is converted into DC power using a rectifier bridge, reducing energy loss, improving the overall efficiency of the system, and simplifying the circuit structure, making the circuit design of the VRF energy storage system simpler and more efficient.

[0016] Optionally, the inverter circuit includes a third inductor, a switching transistor, a diode, a third capacitor, and an inverter unit. The first end of the third inductor is connected to the first output terminal of the rectifier circuit. The switching transistor is connected between the second end of the third inductor and the second output terminal of the rectifier circuit. The anode of the diode is connected to the second end of the third inductor. The cathode of the diode is connected to the first end of the third capacitor and the first input terminal of the inverter unit. The second end of the third capacitor is connected to the second output terminal of the rectifier circuit and the second input terminal of the inverter unit. The output terminal of the inverter unit is configured to connect a load.

[0017] In this way, the inverter circuit can convert the DC voltage output by the rectifier circuit into AC voltage and then transmit it to the load, thereby supplying power to the load. Attached Figure Description

[0018] Figure 1 This is a circuit diagram of the VRF main control board side in the VRF energy storage system according to the embodiments of this application.

[0019] Figure 2 This is a circuit diagram of the battery side in the VRF energy storage system according to the embodiments of this application.

[0020] Figure label:

[0021] 100. VRF energy storage system; 1. Power supply; 2. Rectifier circuit; 3. Inverter circuit; 31. Switching transistor; 32. Diode; 33. Inverter unit; 4. Isolated DC-DC converter circuit; 41. First switching circuit; 411. First branch; 412. Second branch; 42. LLC resonant circuit; 421. First coil of transformer; 422. Second coil of transformer; 43. Second switching circuit; 431. Third branch; 432. Fourth branch; 5. Battery; 6. Load. Detailed Implementation

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present application.

[0023] <VRF energy storage system 100>

[0024] Figure 1 is a schematic circuit diagram on the VRF main control board side in the VRF energy storage system 100 in the embodiments of the present application. Figure 2 is a schematic circuit diagram on the battery 5 side in the VRF energy storage system 100 in the embodiments of the present application. Figure 1 The DC+ in Figure 2 is connected to the DC+ in Figure 1 The DC- in Figure 2 is connected to the DC- in

[0025] Referring to Figure 1 and Figure 2 , the present application provides a VRF energy storage system 100, comprising: a power supply 1, configured to supply power to the entire VRF energy storage system 100; a rectifier circuit 2, connected to the power supply 1, configured to convert alternating current of the power supply 1 into direct current; an inverter circuit 3, having an input end connected to the rectifier circuit 2, and an output end connected to a load 6, wherein the inverter circuit 3 converts the direct current output by the rectifier circuit 2 into alternating current, and outputs the alternating current through the output end to supply power to the load 6; an isolated DC-DC conversion circuit 4, having a first end connected to the direct current voltage output end of the inverter circuit 3; and a battery 5, connected to the second end of the isolated DC-DC conversion circuit 4.

[0026] When the VRF energy storage system 100 is in a power output mode, part of the direct current output by the rectifier circuit 2 passes through the inverter circuit 3, is converted into alternating current and then supplies power to the load 6, and the other part is output to the isolated DC-DC conversion circuit 4 through the direct current voltage output end to charge the battery 5. When the VRF energy storage system 100 is in an energy feedback mode, the direct current at the battery 5 side is transmitted to the direct current voltage output end through the isolated DC-DC conversion circuit 4, so that the inverter circuit 3 converts the direct current fed back from the battery 5 side into alternating current to supply power to the load 6.

[0027] It should be noted that the VRF energy storage system 100 in the embodiments of the present application can be applied to an air conditioning system, and the load 6 can be an air conditioning load.

[0028] Through the above manner, the isolated DC-DC conversion circuit realizes electrical isolation between the VRF main control board side (as shown in Figure 1 ) and the battery 5 side (as shown in Figure 2 The electrical isolation (as shown) reduces the electrical and safety risks of the VRF energy storage system and improves the safety of the VRF energy storage system 100 during use. Specifically, circuit faults or interference on the battery side and the VRF main control board side will not directly affect each other, resulting in a lower electrical risk for the system.

[0029] The components of the VRF energy storage system 100 are described below.

[0030] <Power Supply 1>

[0031] refer to Figure 1 Power supply 1 supplies power to the entire VRF energy storage system 100. Power supply 1 can be the power grid, etc., and output AC power.

[0032] <Rectifier Circuit 2>

[0033] refer to Figure 1 The rectifier circuit 2 can be a rectifier bridge, which is connected to the power supply 1 and can convert the AC power output by the power supply 1 into DC power.

[0034] By using the above methods, AC power is converted into DC power using a rectifier bridge, reducing energy loss during transmission and improving the overall efficiency of the VRF energy storage system 100.

[0035] In some embodiments, the rectifier circuit 2 may also be implemented using a voltage doubler rectifier circuit, a full-wave rectifier circuit, a bridge rectifier circuit, etc. This application does not limit the type of rectifier circuit 2.

[0036] <Inverter Circuit 3>

[0037] refer to Figure 1 The inverter circuit 3 includes a third inductor Lr3, a switching transistor 31, a diode 32, a third capacitor Cr3, and an inverter unit 33 arranged sequentially. The first end of the third inductor Lr3 is connected to the first output terminal of the rectifier circuit 2. The switching transistor 31 is connected between the second end of the third inductor Lr3 and the second output terminal of the rectifier circuit 2. The anode of the diode 32 is connected to the second end of the third inductor. The cathode of the diode 32 is connected to the first end of the third capacitor Cr3 and the first input terminal of the inverter unit 33. The second end of the third capacitor Cr3 is connected to the second output terminal of the rectifier circuit 2 and the second input terminal of the inverter unit 33. The output terminal of the inverter unit 33 is configured to connect to the load 6.

[0038] The inverter unit 33 in the inverter circuit 3 can be an inverter. The inverter can receive DC power from the rectifier circuit 2 at the input terminal and convert it into AC power, and output AC power to the load 6 at the output terminal to supply power to the load 6. The inverter has two input terminals and can output three-phase AC power at the output terminal, that is, the inverter is two-input and three-output. In some embodiments, the inverter can also be set to two-input and one-output or multiple-input and multiple-output, etc. This application does not limit the configuration of the inverter unit 33, as long as it can realize the above voltage transmission.

[0039] In the above manner, the inverter circuit 3 can convert the DC voltage output by the rectifier circuit 2 into AC voltage and transmit it to the load 6, thereby supplying power to the load 6.

[0040] <Isolated DC-DC Conversion Circuit 4>

[0041] refer to Figure 2 The isolated DC-DC converter circuit 4 includes: a first switching circuit 41, with its first terminal connected to the DC voltage output terminal and its second terminal connected to the first terminal of an LLC resonant circuit 42; the second terminal of the LLC resonant circuit 42 is connected to the first terminal of a second switching circuit 43; and the second terminal of the second switching circuit 43 is connected to the battery 5. That is, the first switching circuit 41, the LLC resonant circuit 42, and the second switching circuit 43 are arranged sequentially. The isolated DC-DC converter circuit 4 allows the voltage at the DC voltage output terminal and the current on the battery 5 side to be out of phase / reverse.

[0042] By means of the above method, an LLC resonant circuit 42 is set between the first switching circuit 41 and the second switching circuit 43. When the VRF energy storage system 100 is in power output mode, the voltage output from the DC voltage output terminal serves as the charging voltage for the battery 5 side. That is, power is supplied to the battery 5 side through the first switching circuit 41 and the LLC resonant circuit 42 connected to the DC voltage output terminal. When the VRF energy storage system 100 is in energy feedback mode, the energy of the battery 5 is output and fed back to the DC voltage output terminal. The battery 5 side supplies power to the DC voltage output terminal through the second switching circuit 43 and the LLC resonant circuit 42, thereby supplying power to the load 6. Through the isolated circuit design, power is supplied to the battery 5 side and the energy fed back from the battery 5 side is used to supply power to the load 6, reducing electrical and safety risks.

[0043] like Figure 2 As shown, the DC voltage output terminals include DC+ and DC-, and the first switching circuit 41 includes a first IGBT (such as...). Figure 2 Si1 in the middle), the second IGBT (such as Si1), and the second IGBT (such as Si1). Figure 2 Si2 in the middle), the third IGBT (such as Si2), and the third IGBT (such as Si2). Figure 2 Si3) and the fourth IGBT (such as Figure 2The first H-bridge IGBT consists of Si1 and Si3 (Si4). This first H-bridge IGBT is a DC motor control circuit with an H-shaped circuit. It includes two parallel branches: Si1 and Si3 are located in the first branch 411, with Si1 connected to DC+ and Si3 connected to DC-; Si4 and Si2 are located in the second branch 412. Both the first and second branches are connected to the LLC resonant circuit 42. The two IGBTs on the same branch cannot conduct simultaneously; that is, the first switching circuit 41 can include two conduction modes: Si1 and Si2 can conduct simultaneously, or Si3 and Si4 can conduct simultaneously.

[0044] When the VRF energy storage system 100 is in power output mode, the specific current flow is as follows:

[0045] When Si1 and Si2 are turned on, the current on the first coil 421 side of the transformer flows from DC+ through Si1, Lr1, the first coil 421 of the transformer, Cr1, Si2 to DC-; the induced current on the second coil 422 side of the transformer flows from the positive terminal of battery 5 through So4, Cr2, the second coil 422 of the transformer, Lr2, So3 to the negative terminal of battery 5.

[0046] When Si3 and Si4 are conducting, the current on the first coil 421 side of the transformer flows from DC+ through Si4, Cr1, the first coil 421 of the transformer, Lr1, Si3 to DC-; the induced current on the second coil 422 side of the transformer flows from the positive terminal of battery 5 through So1, Lr2, the second coil 422 of the transformer, Cr2, So2 to the negative terminal of battery 5.

[0047] By alternately switching Si1 and Si2, or Si3 and Si4, the DC voltage is converted into a high-frequency AC voltage. Meanwhile, the low conduction loss of the IGBT switching element helps improve the operating efficiency of the VRF energy storage system 100 in power output mode.

[0048] So1-So4: In power output mode, some switching elements are only turned on to allow current to pass through and do not perform the function of high-frequency transformation, while other switching elements are turned off and are in the closed state, so there is no obvious current flowing through them. For example, So1 and So2 are turned on, while So3 and So4 are turned off.

[0049] refer to Figure 2 The second switching circuit 43 includes a fifth IGBT (such as...) Figure 2 So1 in the middle), the sixth IGBT (such as Figure 2 So2 in the middle), the seventh IGBT (such as Figure 2 So3) and the eighth IGBT (such as Figure 2The second H-bridge IGBT consists of So4 and So3. The second H-bridge IGBT is a DC motor control circuit with an H-shaped circuit. The second H-bridge IGBT is axially symmetrical to the first H-bridge IGBT. The second H-bridge IGBT includes two parallel branches: So1 and So3 are located in the third branch 431, with So1 connected to the positive terminal of battery 5 and So3 connected to the negative terminal of battery 5; So4 and So2 are located in the fourth branch 432. Both the third branch 431 and the fourth branch 432 are connected to the LLC resonant circuit 42. The two IGBTs on the same branch are configured to conduct alternately. Specifically, the second switching circuit 43 can include two conduction modes: So1 and So2 are simultaneously on, while So3 and So4 are off / turned off; or, So3 and So4 are simultaneously on, while So1 and So2 are off / turned off.

[0050] When the VRF energy storage system 100 is in energy feedback mode, the specific current flow is as follows:

[0051] When So1 and So2 are turned on, the current on the second coil 422 side of the transformer flows from the positive terminal of battery 5 through So1, Lr2, the second coil 422 of the transformer, Cr2, So2 to the negative terminal of battery 5; the induced current on the first coil 421 side of the transformer flows from DC+, Si4, Cr1, the first coil 421 of the transformer, Lr1, Si3 to DC-.

[0052] When So3 and So4 are turned on, the current on the second coil 422 side of the transformer flows from the positive terminal of battery 5 through So4, Cr2, the second coil 422 of the transformer, and So3 to the negative terminal of battery 5; the induced current on the first coil 421 side of the transformer flows from DC+, Si1, Lr1, the first coil 421 of the transformer, Cr1, and Si2 to DC-.

[0053] By alternately turning on So1 and So2, or alternately turning on So3 and So4, the DC voltage output by battery 5 is converted into a high-frequency AC voltage.

[0054] Si1-Si4: In energy feedback mode, some switching elements are only turned on to supply current and do not perform the function of high-frequency transformation, while other switching elements are turned off and are in the closed state, so there is no obvious current flowing through them. For example, Si1 and Si2 are turned on, while Si3 and Si4 are turned off.

[0055] like Figure 2As shown, the LLC resonant circuit 42 includes a first inductor Lr1, a second inductor Lr2, a first capacitor Cr1, a second capacitor Cr2, and a transformer Tr. The transformer includes a first transformer coil 421 and a second transformer coil 422 arranged symmetrically. The first end of the first inductor Lr1 is connected to the first branch 411 of the first switching circuit 41, the first end of the first capacitor Cr1 is connected to the second branch 412 of the first switching circuit 41, and the second ends of the first inductor Lr1 and the first capacitor Cr1 are connected to the first transformer coil 421 of the transformer Tr. The first ends of the second inductor Lr2 and the second capacitor Cr2 are connected to the second transformer coil 422 of the transformer Tr, the second end of the second inductor Lr2 is connected to the third branch 431 of the second switching circuit 43, and the second end of the second capacitor Cr2 is connected to the fourth branch 432 of the second switching circuit 43.

[0056] In the above manner, in power output mode, the LLC resonant circuit 42 and transformer Tr perform energy transfer and voltage conversion on the AC voltage output from the high-frequency switching of the first switching circuit 41, rectifying it into DC voltage to power the battery 5. In energy feedback mode, the LLC resonant circuit 42 and transformer Tr perform energy transfer and voltage conversion on the AC voltage output from the high-frequency switching of the second switching circuit 43, rectifying it into DC voltage and transmitting it to the DC voltage output terminal. This DC voltage is then transmitted to the inverter circuit 3, where it is converted into AC power by the inverter unit 33 to power the load 6. Using the LLC resonant circuit 42, zero-voltage switching (ZVS) and zero-current switching (ZCS) can be achieved in the VRF energy storage system 100, reducing IGBT switching losses. Due to the low energy loss of the isolated DC-DC conversion circuit, the overall performance and efficiency of the VRF energy storage system are improved. The LLC resonant circuit 42 controls the output voltage through frequency conversion, providing a wide voltage adjustment range. This achieves efficient energy conversion through resonant characteristics while maintaining voltage and current stability.

[0057] Specifically, in the two different operating modes of the VRF energy storage system 100, there are two resonant frequencies Fs1 and Fs2 between Lr1, Lr2 and the leakage inductance of the transformer Tr.

[0058]

[0059] By adjusting the PWM frequency between the two resonant frequencies, the boost and buck functions of the isolated DC-DC converter circuit 4 can be realized, corresponding to the power output mode and energy feedback mode of the VRF energy storage system 100. A high PWM frequency can reduce the size of the reactors (e.g., the first inductor Lr1 and the second inductor Lr2).

[0060] <Battery 5>

[0061] like Figure 2 As shown, the positive and negative terminals of battery 5 are connected to the two ends of the third branch 431 of the second switching circuit 43, respectively.

[0062] The working process of the VRF energy storage system 100 in the embodiments of this application will be described in detail below.

[0063] When the VRF energy storage system 100 is in power output mode, the AC power output by the power supply 1 is converted into DC power by the rectifier circuit 2, and the electrical energy is transmitted to the battery 5 side through the DC voltage output terminal of the inverter circuit 3.

[0064] The first switching circuit 41, i.e., the first H-bridge IGBT, is in the working state, and the second switching circuit 43, i.e., the second H-bridge IGBT, is in the off state. The DC power from the rectifier circuit 2 is output through the DC voltage output terminal of the inverter circuit 3. The DC power is then generated by the four switching elements Si1-Si4 of the first H-bridge IGBT, which generate high-frequency AC power. This AC power is then transmitted to the transformer of the LLC resonant circuit 42. The electrical energy is converted from the first coil 421 of the transformer Tr through magnetic field coupling and transmitted to the second coil 422 of the transformer. After rectification, the DC power is transmitted to the battery 5 to charge the battery 5.

[0065] When the VRF energy storage system 100 is in energy feedback mode, electrical energy is transmitted to the DC voltage output terminal through the battery 5 via the isolated DC-DC conversion circuit.

[0066] The second switching circuit 43, i.e. the second H-bridge IGBT, is in the working state, while the first switching circuit 41, i.e. the first H-bridge IGBT, is in the off state. The energy at the battery 5 terminal is converted into high-frequency AC power by the four switching elements So1-So4 of the second H-bridge IGBT and transmitted to the transformer of the LLC resonant circuit 42. The electrical energy is converted from the second coil 422 of the transformer Tr through magnetic field coupling and transmitted to the first coil 421 of the transformer. After rectification, the DC voltage is transmitted to the DC voltage output terminal, so that the inverter circuit 3 connected to the DC voltage output terminal can supply power to the load 6 through the output terminal.

[0067] The technical solution of this application has now been described in conjunction with the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of this application is obviously not limited to the specific embodiments described above. Without departing from the principles of this application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions resulting from these changes or substitutions will all fall within the scope of protection of this application.

Claims

1. A VRF energy storage system, characterized in that, include: A power supply for powering the VRF energy storage system; A rectifier circuit is used to convert the alternating current (AC) of the power supply into direct current (DC). The inverter circuit has its input terminal connected to the rectifier circuit and its output terminal configured for connecting a load. An isolated DC-DC converter circuit, the first terminal of which is connected to the DC voltage output terminal of the inverter circuit; and The battery is connected to the second terminal of the isolated DC-DC converter circuit.

2. The VRF energy storage system according to claim 1, characterized in that, The isolated DC-DC converter circuit includes: The first switching circuit has a first terminal connected to the DC voltage output terminal and a second terminal connected to the first terminal of the LLC resonant circuit. The second terminal of the LLC resonant circuit is connected to the first terminal of the second switching circuit, and the second terminal of the second switching circuit is connected to the battery.

3. The VRF energy storage system according to claim 2, characterized in that, The first switching circuit includes a first H-bridge IGBT composed of a first IGBT, a second IGBT, a third IGBT, and a fourth IGBT.

4. The VRF energy storage system according to claim 2, characterized in that, The second switching circuit includes a second H-bridge IGBT composed of a fifth IGBT, a sixth IGBT, a seventh IGBT, and an eighth IGBT.

5. The VRF energy storage system according to claim 2, characterized in that, The LLC resonant circuit includes a first inductor, a second inductor, a first capacitor, a second capacitor, and a transformer. The first end of the first inductor and the first end of the first capacitor are connected to the second end of the first switching circuit. The second end of the first inductor and the second end of the first capacitor are connected to the first end of the transformer. The first end of the second inductor and the first end of the second capacitor are connected to the second end of the transformer. The second end of the second inductor and the second end of the second capacitor are connected to the first end of the second switching circuit.

6. The VRF energy storage system according to any one of claims 1-5, characterized in that, The rectifier circuit is a rectifier bridge.

7. The VRF energy storage system according to any one of claims 1-5, characterized in that, The inverter circuit includes a third inductor, a switching transistor, a diode, a third capacitor, and an inverter unit. The first end of the third inductor is connected to the first output terminal of the rectifier circuit. The switching transistor is connected between the second end of the third inductor and the second output terminal of the rectifier circuit. The anode of the diode is connected to the second end of the third inductor. The cathode of the diode is connected to the first end of the third capacitor and the first input terminal of the inverter unit. The second end of the third capacitor is connected to the second output terminal of the rectifier circuit and the second input terminal of the inverter unit. The output terminal of the inverter unit is configured to connect a load.

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