A power converter, power supply system, control method, and related devices

Abstract

The application discloses a power converter, a power supply system, a control method and related devices. The power converter comprises a three-phase power conversion circuit and a controller, each phase of the three-phase power conversion circuit comprising a four-switch Buck-Boost circuit; a direct current side of the three-phase power conversion circuit is connected with a direct current source, an alternating current side of the three-phase power conversion circuit is connected with a power grid through an alternating current side switch, a direct current side capacitor is connected between a positive electrode of the direct current source and a negative electrode of the direct current source, and an alternating current side capacitor is connected between an alternating current side output end of the power conversion circuit and the negative electrode of the direct current source; the controller is configured to control the three-phase power conversion circuit under the condition that the alternating current side switch is turned off, so that a voltage across the direct current side capacitor is less than a first preset threshold value, and a voltage across the alternating current side capacitor is less than a second preset threshold value. In the embodiment of the application, the discharging of the alternating current side capacitor and the direct current side capacitor can be realized without using an additional discharging circuit, thereby reducing the cost of the power converter.

Description

Technical Field

[0001] This application relates to the field of current resistance technology, and in particular to a power converter, power supply system, control method and related device. Background Technology

[0002] Currently, in industrial and commercial sectors, voltage conversion generally employs a two-stage topology, consisting of a first-stage DC / DC circuit and a second-stage DC / AC circuit. The hardware structure of a two-stage topology is relatively complex, resulting in lower power density. Furthermore, control requires balancing the control objectives of both stages, leading to complex software control. Additionally, each stage of the two-stage topology incurs power conversion losses, thus resulting in lower efficiency. Summary of the Invention

[0003] To address the aforementioned issues, this application provides a power converter, power supply system, control method, and related apparatus that enable the discharge of AC-side capacitors and / or DC-side capacitors without the use of additional discharge circuits, thereby reducing the cost of the power converter.

[0004] The embodiments of this application disclose the following technical solutions:

[0005] In a first aspect, embodiments of this application provide a power converter, including: a three-phase power conversion circuit and a controller, wherein each phase of the three-phase power conversion circuit includes a four-switch Buck-Boost circuit;

[0006] The DC side of the three-phase power conversion circuit is used to connect to the DC source, and the AC side of the three-phase power conversion circuit is connected to the power grid through the AC side switch. The power grid adopts a star connection. The DC side capacitor is connected in parallel to the DC side of the three-phase power conversion circuit, and the AC side capacitor is connected between the AC side output terminal of the four-switch Buck-Boost circuit and the negative terminal of the DC source.

[0007] The controller is used to control the three-phase power conversion circuit when the AC side switch is turned off, so that the voltage across the DC side capacitor is less than a first preset threshold and the voltage across the AC side capacitor is less than a second preset threshold.

[0008] In one possible implementation, the four-switch Buck-Boost circuit includes: a first switch, a second switch, a third switch, a fourth switch, and an inductor; the first and second switches are connected in series to form a first bridge arm, and the two ends of the first bridge arm are respectively connected to the first and second ends of a DC-side capacitor; the third and fourth switches are connected in series to form a second bridge arm, the first end of the first inductor is connected to the midpoint of the first bridge arm, and the second end of the first inductor is connected to the midpoint of the second bridge arm; the first end of the second bridge arm serves as the AC output terminal of the four-switch Buck-Boost circuit, and the second end of the second bridge arm is connected to the negative terminal of the DC source.

[0009] In one possible implementation, the controller is specifically configured to control the three-phase power conversion circuit when the AC side switch is off, to transfer at least a portion of the energy of the AC side capacitor to an inductor and / or to a DC side capacitor via an inductor, to transfer at least a portion of the energy of the DC side capacitor to an inductor and / or to an AC side capacitor via an inductor, and to transfer energy back and forth between the AC side capacitor, the inductor, and the DC side capacitor, until the voltage across the DC side capacitor is less than a first preset threshold and the voltage across the AC side capacitor is less than a second preset threshold.

[0010] In one possible implementation, the controller, specifically for controlling the second and third switches to turn on and the first and fourth switches to turn off, transfers at least a portion of the energy in the AC side capacitor to the inductor.

[0011] Controlling the second and third switches to turn off transfers at least a portion of the energy in the inductor to the DC-side capacitor; or controlling the third switch to turn on and the second and fourth switches to turn off transfers at least a portion of the energy in the inductor and at least a portion of the energy in the AC-side capacitor to the DC-side capacitor; or controlling the second switch to turn on and the first and third switches to turn off retains the energy in the inductor.

[0012] In one possible implementation, the controller is specifically used to control the third switch to turn on and the second and fourth switches to turn off when the voltage across the AC side capacitor is greater than the voltage across the DC side capacitor, thereby transferring at least a portion of the energy in the AC side capacitor to the inductor and / or the DC side capacitor.

[0013] Controlling the second and third switches to turn off transfers at least a portion of the energy in the inductor to the DC-side capacitor; or controlling the fourth switch to turn on turns the first and third switches off, retaining the energy in the inductor.

[0014] In one possible implementation, the controller, specifically used to control the first and fourth switches to turn on and the second and third switches to turn off, transfers at least a portion of the energy in the DC-side capacitor to the inductor.

[0015] Controlling the first and fourth switches to turn off transfers at least a portion of the energy in the inductor to the AC side capacitor; or controlling the first switch to turn on and the second and fourth switches to turn off transfers the energy in the inductor and at least a portion of the energy in the DC side capacitor to the AC side capacitor; or controlling the fourth switch to turn on and the first and third switches to turn off retains the energy in the inductor.

[0016] In one possible implementation, the controller is specifically used to turn on the first switch and turn off the second and fourth switches when the voltage across the DC-side capacitor is greater than the voltage across the AC-side capacitor, thereby transferring at least a portion of the energy in the DC-side capacitor to the inductor and the AC-side capacitor.

[0017] Controlling the first and fourth switches to turn off transfers at least a portion of the energy in the inductor to the AC side capacitor; or controlling the second switch to turn on and the first and third switches to turn off retains the energy in the inductor.

[0018] In one possible implementation, the controller is also used to control any one of the DC-side voltage, DC-side current, and DC-side power of the three-phase power conversion circuit when the voltage across the DC-side capacitor is greater than a corresponding preset threshold, so that the energy in the DC-side capacitor is transferred to the DC source.

[0019] Secondly, embodiments of this application provide a controller method for a power converter. The power converter includes a three-phase power conversion circuit, each phase of which includes a four-switch Buck-Boost circuit. The DC side of the three-phase power conversion circuit is connected to a DC source via an AC side switch, and the AC side of the four-switch Buck-Boost circuit is used to connect to the power grid, which is connected in a star configuration. A DC side capacitor is connected in parallel to the DC side of the three-phase power conversion circuit, and an AC side capacitor is connected between the AC side output terminal of the four-switch Buck-Boost circuit and the negative terminal of the DC source.

[0020] The methods include:

[0021] When the AC side switch is off, the three-phase power conversion circuit is controlled to make the voltage across the DC side capacitor less than the first preset threshold and the voltage across the AC side capacitor less than the second preset threshold.

[0022] In one possible implementation, the four-switch Buck-Boost circuit includes: a first switch, a second switch, a third switch, a fourth switch, and an inductor; the first and second switches are connected in series to form a first bridge arm, and the two ends of the first bridge arm are respectively connected to the first and second ends of a DC-side capacitor; the third and fourth switches are connected in series to form a second bridge arm, the first end of the first inductor is connected to the midpoint of the first bridge arm, and the second end of the first inductor is connected to the midpoint of the second bridge arm; the first end of the second bridge arm serves as the AC output terminal of the four-switch Buck-Boost circuit, and the second end of the second bridge arm is connected to the negative terminal of the DC source; the two ends of the AC-side capacitor are respectively connected to the AC output terminal of the four-switch Buck-Boost circuit and the negative terminal of the DC source.

[0023] When the AC side switch is off, control the three-phase power conversion circuit to ensure that the voltage across the DC side capacitor is less than a first preset threshold and the voltage across the AC side capacitor is less than a second preset threshold, including:

[0024] When the AC side switch is off, the three-phase power conversion circuit is controlled to transfer at least a portion of the energy of the AC side capacitor to the inductor and / or to the DC side capacitor via the inductor, transfer at least a portion of the energy of the DC side capacitor to the inductor and / or to the AC side capacitor via the inductor, and transfer energy back and forth between the AC side capacitor, the inductor, and the DC side capacitor, until the voltage across the DC side capacitor is less than a first preset threshold and the voltage across the AC side capacitor is less than a second preset threshold.

[0025] In one possible implementation, the second and third switches are turned on while the first and fourth switches are turned off, transferring at least a portion of the energy in the AC-side capacitor to the inductor.

[0026] Controlling the second and third switches to turn off transfers at least a portion of the energy in the inductor to the DC-side capacitor; or controlling the third switch to turn on and the second and fourth switches to turn off transfers at least a portion of the energy in the inductor and at least a portion of the energy in the AC-side capacitor to the DC-side capacitor; or controlling the second switch to turn on and the first and third switches to turn off retains the energy in the inductor.

[0027] In one possible implementation, when the voltage across the AC side capacitor is greater than the voltage across the DC side capacitor, the third switch is turned on while the second and fourth switches are turned off, transferring at least a portion of the energy in the AC side capacitor to the inductor and the DC side capacitor.

[0028] The second and third switches are turned off to transfer at least a portion of the energy in the inductor to the DC-side capacitor, or the second switch is turned on while the first and third switches are turned off to retain the energy in the inductor.

[0029] In one possible implementation, the first and fourth switches are turned on while the second and third switches are turned off, transferring at least a portion of the energy in the DC-side capacitor to the inductor.

[0030] Controlling the first and fourth switches to turn off transfers at least a portion of the energy in the inductor to the AC side capacitor; or controlling the first switch to turn on and the second and fourth switches to turn off transfers the energy in the inductor and at least a portion of the energy in the DC side capacitor to the AC side capacitor; or controlling the fourth switch to turn on and the first and third switches to turn off retains the energy in the inductor.

[0031] In one possible implementation, when the voltage across the DC-side capacitor is greater than the voltage across the AC-side capacitor, the first switch is turned on and the second and fourth switches are turned off, transferring at least a portion of the energy in the DC-side capacitor to the inductor and the AC-side capacitor.

[0032] The first and fourth switching transistors are turned off to transfer the energy in the inductor to the AC side capacitor; or, the fourth switching transistor is turned on while the first and third switching transistors are turned off to retain the energy in the inductor.

[0033] In one possible implementation, when the voltage across the DC-side capacitor is greater than a corresponding preset threshold, any one of the DC-side voltage, DC-side current, and DC-side power of the three-phase power conversion circuit is controlled to cause the DC source to consume the energy in the DC-side capacitor.

[0034] Thirdly, embodiments of this application provide a control device, including a processor and a memory, wherein the memory is used to store programs, instructions or code, and the processor is used to execute the programs, instructions or code in the memory to perform the control method as described in any embodiment of the second aspect.

[0035] Fourthly, embodiments of this application provide a computer-readable storage medium storing a computer program, which is loaded by a processor to execute the control method as described in any embodiment of the second aspect.

[0036] Discharging capacitors in power converters typically requires a discharge circuit, increasing the cost of the power converter. Therefore, in this embodiment, the discharge of both the DC-side and AC-side capacitors can be achieved by controlling the three-phase power conversion circuit, ensuring that the voltage across the DC-side capacitor is less than a first preset threshold and the voltage across the AC-side capacitor is less than a second preset threshold. Thus, this embodiment eliminates the need for an additional discharge circuit to discharge the AC-side and / or DC-side capacitors, reducing the cost of the power converter. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of a power converter;

[0039] Figure 2 A schematic diagram of a power converter provided in an embodiment of this application;

[0040] Figure 3 A schematic diagram of energy transfer provided in an embodiment of this application;

[0041] Figure 4 Another schematic diagram of energy transfer provided in this application embodiment;

[0042] Figure 5 This is yet another schematic diagram of energy transfer provided in an embodiment of this application;

[0043] Figure 6 This is another schematic diagram of energy transfer provided in the embodiments of this application;

[0044] Figure 7 This application provides an embodiment of an energy transfer scheme.

[0045] Figure 8 Another schematic diagram of energy transfer provided in this application embodiment;

[0046] Figure 9 A flowchart of a control method for a power converter provided in an embodiment of this application;

[0047] Figure 10 This is a schematic diagram of a control device provided in an embodiment of this application. Detailed Implementation

[0048] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0049] The terms "first" and "second," etc., used in the specification and claims of this application are used to distinguish different objects, not to describe a specific order of objects. For example, "first switching device" and "second switching device," etc., are used to distinguish different switching devices, not to describe a specific order of switching devices.

[0050] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0051] To enable those skilled in the art to understand and implement the technical solutions provided in the embodiments of this application, the architecture of the power converter will be described below in conjunction with the accompanying drawings.

[0052] See Figure 1 The figure shows a schematic diagram of a power converter.

[0053] The power converter includes a three-phase four-switch Buck-Boost circuit. This circuit comprises three independent four-switch Buck-Boost circuits. The inputs of these three circuits are connected in parallel, while their outputs are independent, each serving as a separate three-phase AC output. The DC side of the power converter can be connected to a DC source (not shown in the diagram). A DC-side capacitor, Cdc, is connected in parallel to the DC side of the power converter. The AC side of the power converter is connected to the power grid via a grid-connected switch, Kac. The grid is a three-phase grid with phases A, B, and C, and the three-phase voltages are ua, ub, and uc, respectively. ua, ub, and uc all represent the phase voltages of the grid.

[0054] The first Buck-Boost circuit includes a first switch S1, a first switch S2, a first inductor L1, a second switch S2, and a third switch S3. S1 and S2 are connected in series to form the first bridge arm, and S3 and S4 are connected in series to form the second bridge arm. The first end of the first inductor L1 is connected to the midpoint of the first bridge arm, and the second end of the first inductor L1 is connected to the midpoint of the second bridge arm. The first end of the second bridge arm serves as the output terminal a of the power conversion circuit, and the second end of the second bridge arm is connected to the negative terminal m of the DC source. The two ends of the AC-side capacitor Cfa are connected to the first end of the second bridge arm and the negative terminal m of the DC source, respectively.

[0055] The second Buck-Boost circuit includes a fifth switch S5, a sixth switch S6, a second inductor L2, a seventh switch S7, and an eighth switch S8. S5 and S6 are connected in series to form the third bridge arm, and S7 and S8 are connected in series to form the fourth bridge arm. The first end of the second inductor L2 is connected to the midpoint of the third bridge arm, and the second end of the second inductor L2 is connected to the midpoint of the fourth bridge arm. The first end of the fourth bridge arm serves as the output terminal b of the power conversion circuit, and the second end of the fourth bridge arm is connected to the negative terminal m of the DC source. The two ends of the AC-side capacitor Cfb are connected to the first end of the fourth bridge arm and the negative terminal m of the DC source, respectively.

[0056] The third Buck-Boost circuit includes a ninth switch S9, a tenth switch S10, a third inductor L3, an eleventh switch S11, and a twelfth switch S12. S9 and S10 are connected in series to form the fifth bridge arm, and S11 and S12 are connected in series to form the sixth bridge arm. The first terminal of the third inductor L3 is connected to the midpoint of the fifth bridge arm, and the second terminal of the third inductor L3 is connected to the midpoint of the sixth bridge arm. The first terminal of the sixth bridge arm serves as the output terminal b of the power conversion circuit, and the second terminal of the sixth bridge arm is connected to the negative terminal m of the DC source. The two ends of the AC-side capacitor Cfc are connected to the first terminal of the sixth bridge arm and the negative terminal m of the DC source, respectively.

[0057] This application does not specifically limit the types of the first switch S1 to the twelfth switch S12 in the embodiments. For example, the first switch S1 to the twelfth switch S12 can all be any one of semiconductor switching devices such as metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), and bipolar junction transistors (BJTs). For ease of understanding, the following embodiments will use MOSFETs as an example for relevant descriptions.

[0058] It should be understood that after the power converter is shut down (AC side switch turned off), in order to comply with electrical safety regulations, the voltage across all capacitors in the equipment must drop below the safe voltage within a certain period of time. For example, the voltage across DC side capacitor Cdc, AC side capacitor Cfa, AC side capacitor Cfb, and AC side capacitor Cfc must all drop below the safe voltage.

[0059] The power converter provided in this application embodiment controls the three-phase power conversion circuit to ensure that the voltage across the DC-side capacitor is less than a first preset threshold and the voltage across the AC-side capacitor is less than a second preset threshold when the AC-side switch is open. In this application embodiment, the AC-side and DC-side capacitors can be discharged without using a discharge circuit, thereby reducing the cost of the power converter.

[0060] See Figure 2 This figure is a schematic diagram of a power converter provided in an embodiment of this application.

[0061] like Figure 2 As shown, the power converter provided in this application embodiment includes: a three-phase power conversion circuit and a controller, wherein each phase of the three-phase power conversion circuit includes a four-switch Buck-Boost circuit;

[0062] The DC side of the three-phase power conversion circuit is used to connect to the DC source, and the AC side of the three-phase power conversion circuit is connected to the power grid through the AC side switch. The power grid adopts a star connection. The DC side capacitor Cdc is connected in parallel on the DC side of the three-phase power conversion circuit, and the AC side capacitor is connected between the AC side output terminal of the four-switch Buck-Boost circuit and the negative terminal m of the DC source.

[0063] The AC-side capacitors include Cfa, Cfb, and Cfc. Specifically, AC-side capacitor Cfa is connected between the AC-side output terminal a of the first Buck-Boost circuit and the negative terminal m of the DC source; AC-side capacitor Cfb is connected between the AC-side output terminal b of the second Buck-Boost circuit and the negative terminal m of the DC source; and AC-side capacitor Cfc is connected between the AC-side output terminal c of the third Buck-Boost circuit and the negative terminal m of the DC source.

[0064] For detailed internal connections of the power converter, please refer to [link / reference]. Figure 1 The description will not be repeated here.

[0065] The controller (not shown in the figure) is used to control the three-phase power conversion circuit when the AC side switch Kac is turned off, so that the voltage across the DC side capacitor is less than a first preset threshold and the voltage across the AC side capacitor is less than a second preset threshold.

[0066] In this embodiment of the application, the type of controller is not specifically limited. For example, the controller may be a digital signal processor (DSP) or a field programmable gate array (FPGA).

[0067] The embodiments of this application will be described in detail below in conjunction with the following three situations: First, at least a portion of the energy in the AC-side capacitor Cfa is transferred to the inductor L1, and / or, at least a portion of the energy in the AC-side capacitor Cfa is transferred to the DC-side capacitor Cdc via the inductor L1; Second, at least a portion of the energy in the DC-side capacitor Cdc is transferred to the inductor L1, and / or, at least a portion of the energy in the DC-side capacitor Cdc is transferred to the AC-side capacitor Cfa via the inductor L1; Third, a portion of the energy in the AC-side capacitor Cfa and a portion of the energy in the DC-side capacitor Cdc are transferred back and forth between the AC-side capacitor Cfa, the inductor L1, and the DC-side capacitor Cdc, such that during the back and forth transfer process, at least a portion of the energy is consumed by semiconductor switching devices, capacitors, inductors, and line impedance in the transfer path.

[0068] In the first scenario, the controller controls the three-phase power conversion circuit to transfer at least a portion of the energy in the AC-side capacitor Cfa to the inductor L1, and / or to transfer at least a portion of the energy in the AC-side capacitor Cfa to the DC-side capacitor Cdc via the inductor L1, such that the voltage across the AC-side capacitor Cfa is less than a first preset threshold, and the voltage across the DC-side capacitor Cdc is less than a second preset threshold. The energy transfer diagram is shown below. Figure 3 As shown.

[0069] like Figure 3 As shown in (a), at least a portion of the energy in the AC-side capacitor Cfa is transferred to the inductor L1.

[0070] In one possible implementation, the controller controls the second switch S2 and the third switch S3 to be turned on, and the first switch S1 and the fourth switch S4 to be turned off, so that at least part of the energy in the AC side capacitor is transferred to the inductor L1 through the loop formed by the second switch S2 and the third switch S3; and controls the second switch S2 to be turned on, and the first switch S1 and the third switch S3 to be turned off, so that the energy in the inductor L1 is retained in the inductor L1.

[0071] In another possible implementation, when the voltage across the AC-side capacitor Cfa is greater than the voltage across the DC-side capacitor Cdc, the controller controls the third switch S3 to turn on and the second switch S2 and the fourth switch S4 to turn off, transferring at least a portion of the energy in the AC-side capacitor Cfa to the inductor L1 and the DC-side capacitor Cdc through the loop formed by the first switch S1 (MOSFET or anti-parallel diode) and the third switch S3; and controls the second switch S2 to turn on and the first switch S1 and S3 and the third switch S4 to turn off, retaining the energy in the inductor L1.

[0072] like Figure 3 As shown in (b), at least a portion of the energy in the AC-side capacitor Cfa is transferred to the DC-side capacitor Cdc via the inductor L1.

[0073] In one possible implementation, the controller controls the second switch S2 and the third switch S3 to turn on, and the first switch S1 and the fourth switch S4 to turn off, so that at least part of the energy in the AC side capacitor is transferred to the inductor L1 through the loop formed by the second switch S2 and the third switch S3; the controller controls the second switch S2 and the third switch S3 to turn off, so that the energy in the inductor L1 is transferred to the DC side capacitor Cdc through the loop formed by the first switch S1 (MOSFET or anti-parallel diode) and the fourth switch S4 (MOSFET or anti-parallel diode).

[0074] It should be noted that, in the process of transferring energy from inductor L1 to DC-side capacitor Cdc, the states of the first switch S1 and the fourth switch S4 are not specifically limited in this embodiment. When both the first switch S1 and the fourth switch S4 are on, an energy transfer loop is formed through the first switch S1 and the fourth switch S4; when the first switch S1 is on and the fourth switch S4 is off, an energy transfer loop is formed through the anti-parallel diodes of the first switch S1 and the fourth switch S4; when the first switch S1 is off and the fourth switch S4 is on, an energy transfer loop is formed through the anti-parallel diodes of the first switch S1 and the fourth switch S4; when both the first switch S1 and the fourth switch S4 are off, an energy transfer loop is formed through the anti-parallel diodes of the first switch S1 and the fourth switch S4.

[0075] In one possible implementation, the controller controls the second switch S2 and the third switch S3 to turn on, and the first switch S1 and the fourth switch S4 to turn off, so that at least part of the energy in the AC side capacitor is transferred to the inductor L1 through the loop formed by the second switch S2 and the third switch S3; the controller controls the third switch S3 to turn on, and the second switch S2 and the fourth switch S4 to turn off, so that the energy in the inductor L1 and at least part of the energy in the AC side capacitor Cfa are transferred to the DC side capacitor Cdc through the loop formed by the first switch S1 (MOS transistor or anti-parallel diode) and the third switch S3.

[0076] It should be noted that, in the process of transferring energy from inductor L1 and at least a portion of the energy from AC-side capacitor Cfa to DC-side capacitor Cdc, the embodiments of this application do not specifically limit the state of the first switch S1. When the first switch S1 is turned on, an energy transfer loop is formed through the first switch S1 and the third switch S3; when the first switch S1 is turned off, an energy transfer loop is formed through the anti-parallel diode of the first switch S1 and the third switch S3.

[0077] In one possible implementation, when the voltage across the AC-side capacitor Cfa is greater than the voltage across the DC-side capacitor Cdc, the controller controls the third switch S3 to turn on, and the second switch S2 and the fourth switch S4 to turn off, transferring at least a portion of the energy in the AC-side capacitor Cfa to the inductor L1 and the DC-side capacitor Cdc through the loop formed by the first switch S1 (MOSFET or anti-parallel diode) and the third switch S3; the controller controls the second switch S2 and the third switch S3 to turn off, transferring the energy in the inductor L1 to the DC-side capacitor Cdc through the loop formed by the first switch S1 (MOSFET or anti-parallel diode) and the fourth switch S4 (MOSFET or anti-parallel diode).

[0078] It should be noted that, in the embodiments of this application, the state of the first switch S1 is not specifically limited during the process of transferring energy from the AC-side capacitor Cfa to the inductor L1 and the DC-side capacitor Cdc. When the first switch S1 is turned on, an energy transfer loop is formed through the first switch S1 and the third switch S3; when the first switch S1 is turned off, an energy transfer loop is formed through the anti-parallel diode of the first switch S1 and the third switch S3.

[0079] In this embodiment, by controlling the three-phase power conversion circuit, at least a portion of the energy in the AC-side capacitor Cfa is transferred to the inductor L1, and / or at least a portion of the energy in the AC-side capacitor Cfa is transferred to the DC-side capacitor Cdc via the inductor L1, so that the voltage across the AC-side capacitor Cfa is less than a first preset threshold, and the voltage across the DC-side capacitor Cdc is less than a second preset threshold. Discharging the AC-side capacitor can be achieved without using a discharge circuit, reducing the cost of the power converter.

[0080] To further ensure that the voltage across the AC-side capacitor Cfa is less than a first preset threshold, and the voltage across the DC-side capacitor Cdc is less than a second preset threshold, in this embodiment, when the DC-side switch Kdc is turned on, the controller can also control at least one of the DC-side voltage udc, DC-side current idc, and DC-side power wdc of the three-phase power conversion circuit, so that at least a portion of the energy in the DC-side capacitor Cdc is transferred to the DC source. The energy transfer schematic diagram is shown below. Figure 4 As shown.

[0081] Specifically, when the DC-side switch Kdc is turned on, the DC-side voltage udc of the three-phase power conversion circuit is controlled to be greater than or equal to uin; the DC-side current idc of the three-phase power conversion circuit is controlled to be less than or equal to 0 (the direction of the DC current flowing into the three-phase power conversion circuit is defined as positive); and the DC-side power wdc of the three-phase power conversion circuit is controlled to be less than or equal to 0 (the direction of the DC current flowing into the three-phase power conversion circuit is defined as positive).

[0082] For example, when the DC source includes an energy storage battery, by controlling at least one of the DC-side voltage udc, DC-side current idc, and DC-side power wdc, the DC-side capacitor Cdc charges the energy storage battery, thereby consuming the energy in the DC-side capacitor Cdc; when the DC source includes a photovoltaic module, by controlling at least one of the DC-side voltage udc, DC-side current idc, and DC-side power wdc, the photovoltaic module reverse charges and consumes the energy in the DC-side capacitor Cdc. For example, the photovoltaic module uses the energy in the DC-side capacitor Cdc for operations such as snow melting.

[0083] In this embodiment, by transferring at least a portion of the energy in the DC-side capacitor to the DC source, energy loss can be reduced. Furthermore, by transferring at least a portion of the energy in the DC-side capacitor to the DC source, allowing the DC source to utilize the energy in the DC-side capacitor, the discharge rate of both the DC-side and AC-side capacitors can be increased.

[0084] In the second scenario, the controller controls the three-phase power conversion circuit to transfer at least a portion of the energy in the DC-side capacitor Cdc to the inductor L1, and / or, transfers at least a portion of the energy in the DC-side capacitor Cdc through the AC-side capacitor Cfa of the inductor L1, such that the voltage across the AC-side capacitor Cfa is less than a first preset threshold, and the voltage across the DC-side capacitor Cdc is less than a second preset threshold. The energy transfer diagram is shown below. Figure 5 As shown.

[0085] like Figure 5 As shown in (a), at least a portion of the energy in the DC-side capacitor Cdc is transferred to the inductor L1.

[0086] In one possible implementation, the controller controls the first switch S1 and the fourth switch S4 to be turned on, and the second switch S2 and the third switch S3 to be turned off, so that at least part of the energy in the DC-side capacitor Cdc is transferred to the inductor L1 through the loop formed by the first switch S1 and the fourth switch S8; and controls the fourth switch S4 to be turned on, and the first switch S1, S3 and the third switch S8 to be turned off, so that the energy in the inductor L1 is retained in the inductor L1.

[0087] In another possible implementation, when the voltage across the DC-side capacitor Cdc is greater than the voltage across the AC-side capacitor Cfa, the controller turns on the first switch S1 and turns off the second switch S2 and the fourth switch S4, transferring at least a portion of the energy in the DC-side capacitor Cdc to the inductor L1 and the AC-side capacitor Cfa through the first switch S1 and the third switch S3 (a MOSFET or its anti-parallel diode); and turns on the fourth switch S4 and turns off the first switch S1 and the third switch S3, retaining the energy in the inductor L1.

[0088] like Figure 5 As shown in (b), at least a portion of the energy in the DC-side capacitor Cdc is transferred to the AC-side capacitor Cfa via the inductor L1.

[0089] In one possible implementation, the controller controls the first switch S1 and the fourth switch S4 to be turned on, and the second switch S2 and the third switch S3 to be turned off, so that at least part of the energy in the DC-side capacitor Cdc is transferred to the inductor L1 through the loop formed by the first switch S1 and the fourth switch S8; the controller controls the first switch S1 and the fourth switch S4 to be turned off, so that the energy in the inductor L1 is transferred to the AC-side capacitor Cfa through the loop formed by the second switch S2 (MOSFET or anti-parallel diode) and the third switch S3 (MOSFET or anti-parallel diode).

[0090] It should be noted that in this embodiment, the states of the second switch S2 and the third switch S3 are not specifically limited during the process of transferring energy from inductor L1 to AC-side capacitor Cfa. When both the first switch S1 and the third switch S3 are on, an energy transfer loop is formed through the first switch S1 and the third switch S3; when the first switch S1 is on and the third switch S3 is off, an energy transfer loop is formed through the anti-parallel diodes of the first switch S1 and the third switch S3; when the first switch S1 is off and the third switch S3 is on, an energy transfer loop is formed through the anti-parallel diodes of the first switch S1 and the third switch S3; when both the first switch S1 and the third switch S3 are off, an energy transfer loop is formed through the anti-parallel diodes of the first switch S1 and the anti-parallel diodes of the third switch S3.

[0091] In one possible implementation, the controller controls the first switch S1 and the fourth switch S4 to turn on, and the second switch S2 and the third switch S3 to turn off, so that at least part of the energy in the DC-side capacitor Cdc is transferred to the inductor L1 through the loop formed by the first switch S1 and the fourth switch S8; the controller controls the first switch S1 to turn on, and the second switch S2 and the fourth switch S4 to turn off, so that the energy in the inductor L1 and at least part of the energy in the DC-side capacitor Cdc are transferred to the AC-side capacitor Cfa through the first switch S1 and the third switch S3 (MOSFET or its anti-parallel diode).

[0092] It should be noted that, in the embodiments of this application, the state of the third switch S3 is not specifically limited during the process of transferring energy from inductor L1 and at least a portion of the energy from DC-side capacitor Cdc to AC-side capacitor Cfa. When the third switch S3 is on, an energy transfer loop is formed through the third switch S3 and the first switch S1; when the third switch S3 is off, an energy transfer loop is formed through the anti-parallel diode of the third switch S3 and the first switch S1.

[0093] In one possible implementation, when the voltage across the DC-side capacitor Cdc is greater than the voltage across the AC-side capacitor Cfa, the controller controls the first switch S1 to turn on and the second switch S2 and the fourth switch S4 to turn off, transferring at least a portion of the energy in the DC-side capacitor Cdc to the inductor L1 and the AC-side capacitor Cfa through the first switch S1 and the third switch S3 (a MOSFET or its anti-parallel diode); the controller then controls the first switch S1 and the fourth switch S4 to turn off, transferring the energy in the inductor L1 to the AC-side capacitor Cfa through the loop formed by the second switch S2 (a MOSFET or its anti-parallel diode) and the third switch S3 (a MOSFET or its anti-parallel diode).

[0094] It should be noted that, in the embodiments of this application, the state of the third switch S3 is not specifically limited during the process of transferring at least a portion of the energy in the DC-side capacitor Cdc to the inductor L1 and the AC-side capacitor Cfa. When the third switch S3 is turned on, an energy transfer loop is formed through the third switch S3 and the first switch S1; when the third switch S3 is turned off, an energy transfer loop is formed through the anti-parallel diode of the third switch S3 and the first switch S1.

[0095] In this embodiment, by controlling the three-phase power conversion circuit, at least a portion of the energy in the DC-side capacitor Cdc is transferred to the inductor L1, and / or at least a portion of the energy in the DC-side capacitor Cdc is transferred to the AC-side capacitor Cfa via the inductor L1, so that the voltage across the AC-side capacitor Cfa is less than a first preset threshold, and the voltage across the DC-side capacitor Cdc is less than a second preset threshold. Discharging the DC-side capacitor can be achieved without using a discharge circuit, reducing the cost of the power converter.

[0096] To further ensure that the voltage across the AC-side capacitor Cfa is less than a first preset threshold and the voltage across the DC-side capacitor Cdc is less than a second preset threshold, in this embodiment, when the DC-side switch Kdc is on, the controller can also control at least one of the DC-side voltage udc, DC-side current idc, and DC-side power wdc of the three-phase power conversion circuit to transfer at least a portion of the energy in the DC-side capacitor to the DC source. The specific scheme is as described in the aforementioned embodiments and will not be repeated here. The energy transfer schematic diagram is shown below. Figure 6 As shown.

[0097] In the third scenario, the controller controls the three-phase power conversion circuit to transfer at least a portion of the energy in the DC-side capacitor Cdc and at least a portion of the energy in the AC-side capacitor Cfa back and forth between the DC-side capacitor Cda, the inductor L1, and the AC-side capacitor Cfa, until the voltage across the AC-side capacitor Cfa is less than a first preset threshold and the voltage across the DC-side capacitor Cdc is less than a second preset threshold. The energy transfer diagram is shown below. Figure 7 As shown.

[0098] In this embodiment, by transferring energy back and forth between the AC-side capacitor, inductor, and DC-side capacitor, the electrical energy in the AC-side capacitor, inductor, and DC-side capacitor is consumed by semiconductor switching devices, capacitors, inductors, and line impedance in the transmission path during the energy transfer process, so that the voltage across the AC-side capacitor is less than a first preset threshold and the voltage across the DC-side capacitor is less than a second preset threshold.

[0099] It should be understood that in the first scenario, two methods for transferring at least a portion of the energy from the AC-side capacitor Cfa to the inductor L1, and three methods for transferring at least a portion of the energy from the AC-side capacitor Cfa to the DC-side capacitor Cdc via the inductor L1 were introduced. In the second scenario, two methods for transferring at least a portion of the energy from the DC-side capacitor Cdc to the inductor L1, and three methods for transferring at least a portion of the energy from the DC-side capacitor Cdc to the AC-side capacitor Cfa via the inductor L1 were introduced. Therefore, in this embodiment, the implementation methods in the first scenario and the second scenario can be combined to achieve the back-and-forth transfer of energy between the AC-side capacitor Cfa, the inductor L1, and the DC-side capacitor Cdc, which will not be elaborated further here. The schematic diagram of energy transfer is shown below. Figure 7 As shown.

[0100] In this embodiment, by controlling the three-phase power conversion circuit, at least a portion of the energy in the DC-side capacitor Cdc and at least a portion of the energy in the AC-side capacitor Cfa are transferred between the DC-side capacitor Cdc, the inductor L1, and the AC-side capacitor Cfa until the voltage across the AC-side capacitor Cfa is less than a first preset threshold and the voltage across the DC-side capacitor Cdc is less than a second preset threshold. Discharging the DC-side capacitor can be achieved without using a discharge circuit, reducing the cost of the power converter.

[0101] To further ensure that the voltage across the AC-side capacitor Cfa is less than a first preset threshold, and the voltage across the DC-side capacitor Cdc is less than a second preset threshold, in this embodiment, when the DC-side switch Kdc is turned on, the controller can also control at least one of the DC-side voltage udc, DC-side current idc, and DC-side power wdc of the three-phase power conversion circuit, so that at least a portion of the energy in the DC-side capacitor Cdc is transferred to the DC source. The energy transfer schematic diagram is shown below. Figure 8 As shown.

[0102] It should be noted that, for ease of understanding, the above embodiments all use the A-phase AC side capacitor Cfa of the three-phase power conversion circuit as an example for introduction; the control method for the B-phase AC side capacitor Cfb and the C-phase AC side capacitor of the three-phase power conversion circuit is the same as that for the A-phase AC side capacitor Cfa, and will not be described again.

[0103] The foregoing embodiments describe an embodiment in which each phase AC side capacitor discharges individually. In addition, a method in which at least two phase AC side capacitors discharge alternately is also provided. For example, AC side capacitor Cfa transfers at least a portion of its energy to inductor L1, inductor L1 transfers at least a portion of its energy to DC side capacitor Cdc, DC side capacitor Cdc transfers at least a portion of its energy to inductor L2 and / or inductor L3, inductor L2 transfers at least a portion of its energy to AC side capacitor Cfb, and inductor L3 transfers at least a portion of its energy to AC side capacitor Cfc.

[0104] In addition, embodiments of this application provide a power supply system, which includes any of the power converters in the foregoing embodiments, wherein the DC side of the power converter is used to connect to a DC source.

[0105] In this application embodiment, the DC source can be an energy storage battery or a photovoltaic module. When the DC source includes an energy storage battery, by controlling at least one of the DC-side voltage udc, DC-side current idc, and DC-side power wdc, the DC-side capacitor Cdc charges the energy storage battery, thereby consuming the energy in the DC-side capacitor Cdc. When the DC source includes a photovoltaic module, by controlling at least one of the DC-side voltage udc, DC-side current idc, and DC-side power wdc, the photovoltaic module reverse-charges, consuming the energy in the DC-side capacitor Cdc. For example, the photovoltaic module uses the energy in the DC-side capacitor Cdc for operations such as snow melting.

[0106] Based on the power converter provided in the above embodiments, this application also provides a control method for the power converter, which will be described in detail below with reference to the accompanying drawings.

[0107] See Figure 9 The figure is a flowchart of a control method for a power converter provided in an embodiment of this application.

[0108] The controller method for a power converter provided in this application includes a three-phase power conversion circuit, each phase of which includes a four-switch Buck-Boost circuit. The DC side of the three-phase power conversion circuit is connected to a DC source, and the AC side of the three-phase power conversion circuit is connected to the power grid via an AC side switch. The power grid is connected in a star configuration. A DC-side capacitor is connected in parallel to the DC side of the three-phase power conversion circuit, and an AC-side capacitor is connected between the AC-side output terminal of the four-switch Buck-Boost circuit and the negative terminal of the DC source.

[0109] The methods include:

[0110] S910: Controller AC side switch off.

[0111] S920: When the AC side switch is off, control the three-phase power conversion circuit to make the voltage across the DC side capacitor less than a first preset threshold and the voltage across the AC side capacitor less than a second preset threshold.

[0112] It should be noted that the relationship between the controller and the power converter is not specifically limited in the embodiments of this application. For example, the controller can be a controller within the power converter or a controller independent of the power converter.

[0113] In one possible implementation, the four-switch Buck-Boost circuit includes: a first switch, a second switch, a third switch, a fourth switch, and an inductor;

[0114] The first and second switching transistors are connected in series to form the first bridge arm. The two ends of the first bridge arm are respectively connected to the first and second ends of the DC-side capacitor. The third and fourth switching transistors are connected in series to form the second bridge arm. The first end of the first inductor is connected to the midpoint of the first bridge arm, and the second end of the first inductor is connected to the midpoint of the second bridge arm. The first end of the second bridge arm serves as the AC output terminal of the three-phase power conversion circuit, and the second end of the second bridge arm is connected to the second end of the DC-side capacitor. The two ends of the second bridge arm are respectively connected to the first and second ends of the AC-side capacitor.

[0115] In one possible implementation, when the AC side switch is off, the three-phase power conversion circuit is controlled to transfer at least a portion of the energy of the AC side capacitor to an inductor and / or to a DC side capacitor via an inductor, transfer at least a portion of the energy of the DC side capacitor to an inductor and / or to an AC side capacitor via an inductor, and transfer energy back and forth between the AC side capacitor, the inductor, and the DC side capacitor, until the voltage across the DC side capacitor is less than a first preset threshold and the voltage across the AC side capacitor is less than a second preset threshold.

[0116] In one possible implementation, the second and third switches are turned on while the first and fourth switches are turned off, transferring at least a portion of the energy in the AC-side capacitor to the inductor; the second and third switches are turned off, transferring the energy in the inductor to the DC-side capacitor; or, the third switch is turned on while the second and fourth switches are turned off, transferring the energy in the inductor and at least a portion of the energy in the AC-side capacitor to the DC-side capacitor; or, the second switch is turned on while the first and third switches are turned off, retaining the energy in the inductor.

[0117] In one possible implementation, when the voltage across the AC-side capacitor is greater than the voltage across the DC-side capacitor, the third switch is turned on while the second and fourth switches are turned off, transferring at least a portion of the energy in the AC-side capacitor to the inductor and the DC-side capacitor; the second and third switches are turned off to transfer the energy in the inductor to the DC-side capacitor; or the second switch is turned on while the first and third switches are turned off, retaining the energy in the inductor.

[0118] In one possible implementation, the first and fourth switches are turned on while the second and third switches are turned off, transferring at least a portion of the energy in the DC-side capacitor to the inductor; the first and fourth switches are turned off, transferring the energy in the inductor to the AC-side capacitor; or, the first switch is turned on while the second and fourth switches are turned off, transferring the energy in the inductor and at least a portion of the energy in the DC-side capacitor to the AC-side capacitor; or, the fourth switch is turned on while the first and third switches are turned off, retaining the energy in the inductor.

[0119] In one possible implementation, when the voltage across the DC-side capacitor is greater than the voltage across the AC-side capacitor, the first switch is turned on while the second and fourth switches are turned off, transferring at least a portion of the energy in the DC-side capacitor to the inductor and the AC-side capacitor; the first and fourth switches are turned off to transfer the energy in the inductor to the AC-side capacitor; or the fourth switch is turned on while the first and third switches are turned off, retaining the energy in the inductor.

[0120] In one possible implementation, when the voltage across the DC-side capacitor is greater than a corresponding preset threshold, any one of the DC-side voltage, DC-side current, and DC-side power of the three-phase power conversion circuit is controlled to cause the DC source to consume the energy in the DC-side capacitor.

[0121] In one possible implementation, see Figure 10 The figure is a schematic diagram of a control device provided in an embodiment of this application.

[0122] The control device may include a memory 1011 and a processor 1012. The processor 1012 may be connected to the power converter and can drive the switches in the various power conversion circuits of the power converter. For example... Figure 10 As shown, the memory can be random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (Electronic Programmable ROM), registers, hard disks, removable disks, etc.

[0123] The memory 1011 can store computer instructions. When the computer instructions stored in the memory 1011 are executed by the processor 1012, the processor 1012 can be used to execute the control method of the power converter. The memory 1011 can also store data, such as information like preset ranges involved in the above embodiments.

[0124] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape) or a semiconductor medium (e.g., solid-state disk (SSD)).

[0125] This application also provides a readable storage medium for storing the methods provided in the above embodiments. Examples include random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (EPROM), registers, hard disks, removable disks, or any other form of storage medium in the art.

[0126] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the methods disclosed in the embodiments, since they correspond to the product embodiments disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the description of the product embodiments.

[0127] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power converter, characterized in that, include: A three-phase power conversion circuit and a controller, wherein each phase of the three-phase power conversion circuit includes a four-switch Buck-Boost circuit; The DC side of the three-phase power conversion circuit is used to connect to a DC source, and the AC side of the three-phase power conversion circuit is connected to the power grid through an AC side switch. The power grid is connected in a star configuration. A DC side capacitor is connected in parallel to the DC side of the three-phase power conversion circuit, and an AC side capacitor is connected between the AC side output terminal of the four-switch Buck-Boost circuit and the negative terminal of the DC source. The controller is used to control the three-phase power conversion circuit when the AC side switch is turned off, so that the voltage across the DC side capacitor is less than a first preset threshold and the voltage across the AC side capacitor is less than a second preset threshold.

2. The power converter according to claim 1, characterized in that, The four-switch Buck-Boost circuit includes: a first switch transistor, a second switch transistor, a third switch transistor, a fourth switch transistor, and an inductor; The first and second switches are connected in series to form a first bridge arm, and the two ends of the first bridge arm are respectively connected to the first and second ends of the DC-side capacitor; the third and fourth switches are connected in series to form a second bridge arm, the first end of the first inductor is connected to the midpoint of the first bridge arm, and the second end of the first inductor is connected to the midpoint of the second bridge arm; the first end of the second bridge arm serves as the AC output terminal of the four-switch Buck-Boost circuit, and the second end of the second bridge arm is connected to the negative terminal of the DC source.

3. The power converter according to claim 2, characterized in that, The controller is specifically configured to control the three-phase power conversion circuit when the AC side switch is turned off, to transfer at least a portion of the energy of the AC side capacitor to the inductor and / or to the DC side capacitor via the inductor, to transfer at least a portion of the energy of the DC side capacitor to the inductor and / or to the AC side capacitor via the inductor, and to transfer energy back and forth between the AC side capacitor, the inductor, and the DC side capacitor, until the voltage across the DC side capacitor is less than a first preset threshold and the voltage across the AC side capacitor is less than a second preset threshold.

4. The power converter according to claim 3, characterized in that, The controller is specifically used to control the second and third switching transistors to be turned on, and the first and fourth switching transistors to be turned off, so as to transfer at least a portion of the energy in the AC side capacitor to the inductor. The second and third switches are turned off to transfer at least a portion of the energy in the inductor to the DC-side capacitor; or, the third switch is turned on and the second and fourth switches are turned off to transfer at least a portion of the energy in the inductor and at least a portion of the energy in the AC-side capacitor to the DC-side capacitor; or, the second switch is turned on and the first and third switches are turned off to retain the energy in the inductor.

5. The power converter according to claim 3, characterized in that, The controller is specifically configured to, when the voltage across the AC side capacitor is greater than the voltage across the DC side capacitor, control the third switch to turn on and the second and fourth switches to turn off, so as to transfer at least a portion of the energy in the AC side capacitor to the inductor and / or the DC side capacitor. The second and third switches are turned off to transfer at least a portion of the energy in the inductor to the DC-side capacitor; or the second switch is turned on while the first and third switches are turned off to retain the energy in the inductor.

6. The power converter according to any one of claims 3-5, characterized in that, The controller is specifically used to control the first switch and the fourth switch to be turned on, and the second switch and the third switch to be turned off, so as to transfer at least part of the energy in the DC-side capacitor to the inductor; The first and fourth switches are turned off to transfer at least a portion of the energy in the inductor to the AC-side capacitor; or, the first switch is turned on and the second and fourth switches are turned off to transfer the energy in the inductor and at least a portion of the energy in the DC-side capacitor to the AC-side capacitor; or, the fourth switch is turned on and the first and third switches are turned off to retain the energy in the inductor.

7. The power converter according to any one of claims 3-5, characterized in that, The controller is specifically used to control the first switch to turn on and the second and fourth switches to turn off when the voltage across the DC-side capacitor is greater than the voltage across the AC-side capacitor, so as to transfer at least a portion of the energy in the DC-side capacitor to the inductor and the AC-side capacitor. The first and fourth switches are turned off to transfer at least a portion of the energy in the inductor to the AC side capacitor; or the fourth switch is turned on while the first and third switches are turned off to retain the energy in the inductor.

8. The power converter according to any one of claims 3-5, characterized in that, The controller is also used to control any one of the DC-side voltage, DC-side current and DC-side power of the three-phase power conversion circuit when the voltage across the DC-side capacitor is greater than the corresponding preset threshold, so that the energy in the DC-side capacitor is transferred to the DC source.

9. A power supply system, characterized in that, Includes the power converter and DC source as described in any one of claims 1-8; The DC side of the power converter is connected to the DC source.

10. A controller method for a power converter, characterized in that, The power converter includes a three-phase power conversion circuit, each phase of which includes a four-switch Buck-Boost circuit. The DC side of the three-phase power conversion circuit is connected to a DC source via an AC side switch. The AC side of the four-switch Buck-Boost circuit is connected to the power grid, which is in a star configuration. A DC-side capacitor is connected in parallel to the DC side of the three-phase power conversion circuit, and an AC-side capacitor is connected between the AC-side output terminal of the four-switch Buck-Boost circuit and the negative terminal of the DC source. The method includes: When the AC side switch is turned off, the three-phase power conversion circuit is controlled to make the voltage across the DC side capacitor less than a first preset threshold and the voltage across the AC side capacitor less than a second preset threshold.

11. The method according to claim 10, characterized in that, The four-switch Buck-Boost circuit includes: a first switch, a second switch, a third switch, a fourth switch, and an inductor; the first switch and the second switch are connected in series to form a first bridge arm, and the two ends of the first bridge arm are respectively connected to the first end and the second end of the DC-side capacitor; the third switch and the fourth switch are connected in series to form a second bridge arm, the first end of the first inductor is connected to the midpoint of the first bridge arm, and the second end of the first inductor is connected to the midpoint of the second bridge arm; the first end of the second bridge arm serves as the AC output terminal of the four-switch Buck-Boost circuit, and the second end of the second bridge arm is connected to the negative terminal of the DC source; the two ends of the AC-side capacitor are respectively connected to the AC output terminal of the four-switch Buck-Boost circuit and the negative terminal of the DC source; The step of controlling the three-phase power conversion circuit to make the voltage across the DC-side capacitor less than a first preset threshold and the voltage across the AC-side capacitor less than a second preset threshold when the AC-side switch is turned off includes: When the AC side switch is off, the three-phase power conversion circuit is controlled to transfer at least a portion of the energy of the AC side capacitor to the inductor and / or through the inductor to the DC side capacitor, transfer at least a portion of the energy of the DC side capacitor to the inductor and / or through the inductor to the AC side capacitor, and transfer energy back and forth between the AC side capacitor, the inductor, and the DC side capacitor, until the voltage across the DC side capacitor is less than a first preset threshold and the voltage across the AC side capacitor is less than a second preset threshold.

12. The method according to claim 11, characterized in that, Controlling the three-phase power conversion circuit to transfer at least a portion of the energy from the AC-side capacitor to the inductor and / or via the inductor to the DC-side capacitor includes: The second and third switches are turned on, while the first and fourth switches are turned off, transferring at least a portion of the energy in the AC side capacitor to the inductor. The second and third switches are turned off to transfer at least a portion of the energy in the inductor to the DC-side capacitor; or, the third switch is turned on and the second and fourth switches are turned off to transfer at least a portion of the energy in the inductor and at least a portion of the energy in the AC-side capacitor to the DC-side capacitor; or, the second switch is turned on and the first and third switches are turned off to retain the energy in the inductor.

13. The method according to claim 11, characterized in that, Controlling the three-phase power conversion circuit to transfer at least a portion of the energy from the AC-side capacitor to the inductor and / or via the inductor to the DC-side capacitor includes: When the voltage across the AC side capacitor is greater than the voltage across the DC side capacitor, the third switch is turned on, and the second and fourth switches are turned off, transferring at least a portion of the energy in the AC side capacitor to the inductor and the DC side capacitor. The second and third switches are turned off to transfer at least a portion of the energy in the inductor to the DC-side capacitor; or the second switch is turned on while the first and third switches are turned off to retain the energy in the inductor.

14. The method according to any one of claims 11-13, characterized in that, Controlling the three-phase power conversion circuit to transfer at least a portion of the energy from the DC-side capacitor to the inductor and / or via the inductor to the AC-side capacitor includes: The first and fourth switching transistors are turned on, while the second and third switching transistors are turned off, so that at least a portion of the energy in the DC-side capacitor is transferred to the inductor. The first and fourth switches are turned off to transfer at least a portion of the energy in the inductor to the AC-side capacitor; or, the first switch is turned on and the second and fourth switches are turned off to transfer the energy in the inductor and at least a portion of the energy in the DC-side capacitor to the AC-side capacitor; or, the fourth switch is turned on and the first and third switches are turned off to retain the energy in the inductor.

15. The method according to any one of claims 11-13, characterized in that, Controlling the three-phase power conversion circuit to transfer at least a portion of the energy from the DC-side capacitor to the inductor and / or via the inductor to the AC-side capacitor includes: When the voltage across the DC-side capacitor is greater than the voltage across the AC-side capacitor, the first switch is turned on, and the second and fourth switches are turned off, transferring at least a portion of the energy in the DC-side capacitor to the inductor and the AC-side capacitor. The first and fourth switches are turned off to transfer the energy in the inductor to the AC side capacitor; or the fourth switch is turned on while the first and third switches are turned off to retain the energy in the inductor.

16. The method according to any one of claims 11-13, characterized in that, The method further includes: When the voltage across the DC-side capacitor is greater than the corresponding preset threshold, any one of the DC-side voltage, DC-side current, and DC-side power of the three-phase power conversion circuit is controlled to cause the DC source to consume the energy in the DC-side capacitor.

17. A control device, characterized in that, It includes a processor and a memory, the memory being used to store programs, instructions, or code, and the processor being used to execute the programs, instructions, or code in the memory to perform the control method as described in any one of claims 10-16.

18. A computer-readable storage medium, characterized in that, The system contains a computer program that is loaded by a processor to execute the control method as described in any one of claims 10-16.

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