A power converter, power supply system, control method, and related devices
By combining a single-stage three-phase four-switch Buck-Boost circuit with an impedance network, the complexity of the two-stage topology and the problem of switch device damage are solved, achieving efficient power conversion and switch device protection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SUNGROW POWER SUPPLY CO LTD
- Filing Date
- 2024-12-03
- Publication Date
- 2026-06-05
AI Technical Summary
Existing two-stage topology power converters have complex hardware structures, low power density, low efficiency, and complex control. Furthermore, when switching from a three-phase three-wire system to a three-phase four-wire system, the switching devices are easily damaged by the inrush current in the neutral line circuit.
A single-stage three-phase four-switch Buck-Boost circuit is adopted, and an impedance network is inserted in series in the N-line loop. Combined with the controller to adjust the difference between the DC side and the bias voltage, the risk of inrush current is reduced, and the power loss is reduced through the impedance network.
It improves the power density and energy conversion efficiency of the power converter, reduces the risk of damage to switching devices, simplifies the control logic, and adapts to a wider range of DC source voltages.
Smart Images
Figure CN122159700A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power electronics technology, specifically to a power converter, power supply system, control method, and related devices. 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 reduce the risk of damage to switching devices in the power converter due to inrush current in the neutral (N) line circuit when switching from a three-phase three-wire system to a three-phase four-wire system.
[0004] The embodiments of this application disclose the following technical solutions:
[0005] In a first aspect, embodiments of this application provide a power converter, which includes: an impedance network and a three-phase power conversion circuit, 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 a DC source, and the AC side is used to connect to the load or the power grid; the load is connected in a star configuration, and the power grid is connected in a star configuration.
[0007] The first end of the impedance network is connected to the positive DC side of the three-phase power conversion circuit, and the second end of the impedance network is used to connect to the neutral point of the load or the neutral point of the power grid.
[0008] Optionally, the power converter may also include: a controller;
[0009] The controller is used to control the DC side voltage and / or DC bias voltage when the absolute difference between the AC side voltage of the three-phase power conversion circuit and the DC bias voltage of the DC source negative terminal is greater than a preset threshold, so that the absolute difference between the DC side voltage and the DC bias voltage is less than the preset threshold.
[0010] Optionally, the power converter further includes: a controller and a first switching device;
[0011] The first switching device is connected in parallel across the impedance network;
[0012] The controller is used to control the first switching device to turn on when the absolute difference between the AC side voltage of the three-phase power conversion circuit and the DC bias voltage of the DC source negative terminal is greater than a preset threshold.
[0013] Optionally, the impedance network includes at least one of a resistor, an inductor, and a capacitor.
[0014] Optionally, each of the four-switch Buck-Boost circuits includes: a first switch, a second switch, a third switch, a fourth switch, an inductor, and an AC-side capacitor;
[0015] The first and second switching transistors are connected in series to form the first bridge arm, and the two ends of the first bridge arm are connected to the positive and negative terminals of the DC source, respectively. 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 output terminal of the power conversion 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 connected to the first end of the second bridge arm and the negative terminal of the DC source, respectively.
[0016] Optionally, the power converter further includes: a second switching device;
[0017] The second switching device is connected in series with the impedance network;
[0018] The controller is also used to control the switching action of the second switching device to switch the operating mode of the power converter; wherein, when the second switching device is off, the power converter operates in a three-phase three-wire system, and when the second switching device is on, the power converter operates in a three-phase four-wire system.
[0019] Secondly, embodiments of this application provide a power supply system, which includes: a DC source and a power converter according to any embodiment of the first aspect; wherein the DC source includes a photovoltaic module or a battery module;
[0020] The DC side of the power converter is connected to a DC source.
[0021] Thirdly, embodiments of this application provide a control method for a power converter. The power converter includes an impedance network and a three-phase power conversion circuit. 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 used to connect to a load or a power grid. The first end of the impedance network is connected to the positive terminal of the DC side of the three-phase power conversion circuit, and the second end of the impedance network is used to connect to the neutral point of the load or the neutral point of the power grid. The load and the power grid are both connected in a star configuration.
[0022] The methods include:
[0023] Obtain the DC side voltage of the three-phase power conversion circuit, and the DC bias voltage of the AC side voltage relative to the negative terminal of the DC source;
[0024] If the absolute difference between the DC-side voltage and the DC bias voltage is greater than a preset threshold, the DC-side voltage and / or the DC bias voltage are controlled so that the absolute difference between the DC-side voltage and the DC bias voltage is less than the preset threshold.
[0025] Optionally, the converter further includes a first switching device connected in parallel across the impedance network, and the method further includes:
[0026] When the absolute difference between the DC side voltage and the DC bias voltage is greater than a preset threshold, the first switching device is controlled to turn on.
[0027] Fourthly, 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 first aspect.
[0028] Fifthly, 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 first aspect.
[0029] When the power converter switches from a three-phase four-wire system to a three-phase four-wire system, and the DC bias voltage of the AC side of the power converter relative to the negative terminal of the DC source is not equal to the DC side voltage of the power converter, an inrush current will be generated on the N-line of the power converter, which can damage the switching devices inside the power converter. Therefore, the power converter provided in this application incorporates an impedance network in series in the N-line loop (the first end of the N-line is connected to the DC side of the three-phase power conversion circuit, and the second end of the N-line is connected to the neutral point of the load or the neutral point of the power grid) to reduce the inrush current in the N-line loop, thereby reducing the risk of damage to the switching devices inside the power converter due to the N-line inrush current. Attached Figure Description
[0030] 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.
[0031] Figure 1 This is a schematic diagram of a power converter;
[0032] Figure 2 A schematic diagram of a power converter provided in an embodiment of this application;
[0033] Figure 3 A schematic diagram of the impedance network provided in an embodiment of this application;
[0034] Figure 4 A schematic diagram of another power converter provided in an embodiment of this application;
[0035] Figure 5 A schematic diagram of yet another power converter provided in the embodiments of this application;
[0036] Figure 6 A schematic diagram of a power supply system provided in an embodiment of this application;
[0037] Figure 7 A flowchart illustrating a control method for a power converter provided in an embodiment of this application;
[0038] Figure 8 This is a schematic diagram of a control device provided in an embodiment of this application. Detailed Implementation
[0039] 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.
[0040] 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.
[0041] 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.
[0042] To facilitate understanding of the technical solutions of this application, the application scenarios of the embodiments of this application will be introduced below.
[0043] Power converters can operate in various modes, such as three-phase three-wire and three-phase four-wire systems. When switching from a three-phase three-wire system to a three-phase four-wire system, and the AC side voltage of the three-phase power conversion circuit is not equal to the bias voltage of the DC source negative terminal, an inrush current will be generated in the neutral (N) circuit of the power converter, which may damage the switching devices in the power converter.
[0044] Therefore, the power converter provided in this application embodiment inserts an impedance network in series in the N-line (the first end of the N-line is connected to the DC side of the three-phase power conversion circuit, and the second end of the N-line is connected to the neutral point of the load or the neutral point of the power grid) loop to reduce the inrush current in the N-line loop, thereby reducing the risk of damage to the switching devices in the power converter due to the N-line inrush current.
[0045] 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.
[0046] See Figure 1 This figure is a schematic diagram of a power converter provided in an embodiment of this application.
[0047] like Figure 1 As shown, the power converter provided in this application embodiment includes a three-phase four-switch Buck-Boost circuit. The power converter provided in this application embodiment is a single-stage AC / DC converter, which can improve power density compared to a two-stage power converter. Furthermore, since the power converter is single-stage, it can reduce power consumption and improve energy conversion efficiency compared to a two-stage power converter. Moreover, the power converter provided in this application embodiment can be applied to DC sources with a wide voltage range, such as photovoltaic panels or energy storage batteries. For example, in one possible implementation, the AC side voltage is 311V, corresponding to a DC side voltage range of 280V-380V.
[0048] The first terminals of the three-phase four-switch Buck-Boost circuit are connected in parallel to a DC source. The second terminals of each circuit are independent and connected to the three AC phases of the power converter, respectively. The DC side voltage of the DC source is denoted by Uin. The AC side of the power converter is connected to the power grid or load Rd. The power grid is a three-phase grid, with phases A, B, and C, and the three-phase voltages are ua, ub, and uc, where ua, ub, and uc represent the phase voltages of the power grid.
[0049] The first Buck-Boost circuit includes a first switch S1, a second switch S2, a first inductor L1, a third switch S3, and a fourth switch S4. The first switch S1 and the second switch S2 are connected in series to form the first bridge arm, and the third switch S3 and the fourth switch 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.
[0050] 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. Switches S5 and S6 are connected in series to form the third bridge arm, and switches S7 and S8 are connected in series to form the fourth bridge arm. The first terminal of the second inductor L2 is connected to the midpoint of the third bridge arm, and the second terminal of the second inductor L2 is connected to the midpoint of the fourth bridge arm. The first terminal of the fourth bridge arm serves as the output terminal b of the power conversion circuit, and the second terminal 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 terminal of the fourth bridge arm and the negative terminal m of the DC source, respectively.
[0051] 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. Switches S9 and S10 are connected in series to form the fifth bridge arm, and switches 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.
[0052] The three-phase output terminals a, b, and c are connected to the negative terminal m of the DC source via corresponding AC-side capacitors Cfa, Cfb, and Cfc, respectively.
[0053] In the case of switching the power converter from a three-phase three-wire system to a three-phase four-wire system, the DC side of the three-phase power conversion circuit is connected to the neutral point of the load Rd or the neutral point of the power grid via the N line. For example... Figure 1 As shown, the AC side voltage of the three-phase power converter circuit has a DC bias Vo relative to the negative terminal m of the DC source. If the DC bias voltage Vo is greater than the DC side voltage Vin of the three-phase power converter circuit, an inrush current will occur in the N-line circuit. This inrush current may damage the switching devices inside the power converter.
[0054] Therefore, the power converter provided in this application embodiment inserts an impedance network in series in the N-line (the first end of the N-line is connected to the DC side of the three-phase power conversion circuit, and the second end of the N-line is connected to the neutral point of the load or the neutral point of the power grid) loop to reduce the inrush current in the N-line loop, thereby reducing the risk of damage to the switching devices in the power converter due to the N-line inrush current.
[0055] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.
[0056] See Figure 2 This figure is a schematic diagram of a power converter provided in an embodiment of this application.
[0057] like Figure 2 As shown, the power converter provided in this embodiment includes an impedance network 200 and a three-phase power conversion circuit 100. Each phase of the three-phase power conversion circuit 100 includes a four-switch Buck-Boost circuit. For details, please refer to... Figure 1 The connections shown will not be elaborated further here.
[0058] The first end of the impedance network 200 is connected to the positive DC side of the three-phase power conversion circuit 100, and the second end of the impedance network 200 is connected to the neutral point of the load Rd or the neutral point of the power grid.
[0059] When the power converter switches from a three-phase three-wire system to a three-phase four-wire system, the impedance network 200 reduces the inrush current on the N line, thereby reducing the risk of damage to the switching devices inside the power converter.
[0060] In this embodiment of the application, the form of the impedance network 200 is not specifically limited. For example, the impedance network 200 may include any one of a resistor, a capacitor, or an inductor, or at least one of a resistor, a capacitor, or an inductor.
[0061] In this embodiment, when the impedance network 200 includes a resistor, the voltage difference between the DC bias voltage Vo and the DC side voltage vin acts directly on the resistor, thereby reducing the inrush current on the N-line by limiting the current; when the impedance network 200 includes a capacitor, the voltage difference between the DC bias voltage Vo and the DC side voltage vin acts directly on the capacitor, thereby reducing the inrush current on the N-line by isolating the DC current; when the impedance network 200 includes an inductor, the voltage difference between the DC bias voltage Vo and the DC side voltage vin acts directly on the inductor, thereby reducing the inrush current on the N-line by suppressing the DC current conversion rate.
[0062] For example, some combinations of impedance networks such as Figure 3As shown. Figure 3 As shown in (a), the impedance network includes a capacitor and an inductor connected in series, such as... Figure 3 As shown in (b), the impedance network includes capacitors and resistors connected in series, such as... Figure 3 As shown in (c), the impedance network includes an inductor and a resistor connected in series, such as... Figure 3 As shown in (d), the impedance network includes a capacitor, a resistor, and an inductor connected in series, as follows: Figure 3 As shown in (e), the impedance network includes capacitors and resistors connected in parallel, such as... Figure 3 As shown in (f), the impedance network includes parallel capacitors and inductors, such as... Figure 3 As shown in (g), the impedance network consists of a capacitor and a resistor connected in parallel, followed by an inductor in series, as shown in Figure (g). Figure 3 As shown in (h), the impedance network consists of a capacitor and a resistor connected in parallel and then a capacitor connected in series.
[0063] It is important to note that Figure 3 The combinations shown are merely exemplary. The impedance network in the embodiments of this application can also be other combinations of inductors, resistors, and capacitors, which will not be elaborated here.
[0064] The power converter provided in this application embodiment incorporates an impedance network in the N-line (the first end of the N-line is connected to the DC side of the three-phase power conversion circuit, and the second end of the N-line is connected to the neutral point of the load or the neutral point of the power grid) loop to reduce the inrush current in the N-line loop, thereby reducing the risk of damage to the switching devices in the power converter due to the N-line inrush current.
[0065] To reduce power loss on the N line, in this embodiment of the application, the DC bias voltage Vo and / or the DC side voltage Vin can also be controlled by a controller so that the absolute difference between the DC bias voltage Vo and the DC side voltage Vin is less than a preset threshold.
[0066] The controller (not shown in the figure) is used to acquire the DC side voltage Vin of the three-phase power conversion circuit and the DC bias voltage Vo of the AC side voltage of the three-phase power conversion circuit relative to the negative terminal of the DC source; when the absolute difference between the DC side voltage Vin and the DC bias voltage Vo is greater than a preset threshold, the controller controls the DC side voltage Vin and / or the DC bias voltage Vo so that the absolute difference between the DC side voltage Vin and the DC bias voltage Vo is less than the preset threshold.
[0067] 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).
[0068] When the DC bias voltage Vo is greater than the DC side voltage Vin, the absolute difference can be expressed as Vo-Vin. In the embodiments of this application, the controller can take any one of the following three approaches: first, decrease the DC bias voltage Vo; second, increase the DC side voltage Vin; third, decrease the DC bias voltage Vo and increase the DC side voltage Vin.
[0069] When the DC bias voltage Vo is less than the DC side voltage Vin, the absolute difference can be expressed as Vin-Vo. In the embodiments of this application, the controller can take any one of the following three approaches: first, decrease the DC side voltage Vin; second, increase the DC bias voltage Vo; third, decrease the DC side voltage Vin and increase the DC bias voltage Vo.
[0070] It should be understood that the preset threshold in the embodiments of this application approaches zero under ideal conditions, and can be set or adjusted according to the user's needs in practical applications.
[0071] To further reduce power loss on the N-line, this application provides a schematic diagram of another power converter, as shown in the embodiment. Figure 4 As shown.
[0072] exist Figure 4 The power converter includes an impedance network 200, a three-phase power conversion circuit 100, and a first switching device K1. Each phase of the three-phase power conversion circuit 100 includes a four-switch Buck-Boost circuit. The specific connection relationship between the three-phase power conversion circuit and the impedance network 200 can be found in the aforementioned embodiments and will not be repeated here.
[0073] The first switching device K1 is connected in parallel across the impedance network 200.
[0074] In this embodiment of the application, the type of the first switching device K1 is not specifically limited. For example, the first switching device K1 may be a mechanical switch (circuit breaker, disconnector, contactor and relay, etc.), a bidirectional semiconductor device (bidirectional thyristor, a pair of insulated-gate bipolar transistors (IGBTs) with common E or common C, a pair of metal-oxide-semiconductor field-effect transistors (MOSFETs) with common D or common S, etc.), or a switching device assembly with bidirectional current flow capability formed by combining multiple mechanical switches and semiconductor devices.
[0075] The controller (not shown in the figure) is used to control the first switching device K1 to turn on when the absolute difference between the DC side voltage Vin and the DC bias voltage Vo is less than a preset threshold.
[0076] In this embodiment, when the absolute difference between the DC side voltage Vin and the DC bias voltage Vo is less than a preset threshold, the first switching device K1 is turned on to further reduce the power loss on the N line.
[0077] In addition, such as Figure 5 As shown, the power converter in this embodiment further includes a second switching device K2, a load switching group K3, and a grid switching group K4. The first switching device K1 is connected in parallel with the impedance network before being connected to the second switching device K2.
[0078] The controller (not shown in the figure) is used to control the on and off of the second switching device K2, so that the power converter operates in a three-phase four-wire system when the second switching device K2 is on, and in a three-phase three-wire system when the second switching device K2 is off.
[0079] It should be noted that when the absolute difference between the DC side voltage Vin and the DC bias voltage Vo is less than a preset threshold, the second switching device K2 is turned on, and the on state of the first switching device K1 is not limited; when the absolute difference between the DC side voltage Vin and the DC bias voltage Vo is greater than or equal to the preset threshold, the first switching device K1 is turned off first, and then the second switching device K2 is turned on.
[0080] The controller (not shown in the figure) is also used to control the on and off of the load switch group K3 so that the AC side of the three-phase power conversion circuit is connected to the load when the load switch group K3 is on; and to control the on and off of the grid switch group K4 so that the AC side of the three-phase power conversion circuit is connected to the grid when the grid switch group K4 is on.
[0081] In this embodiment, the type of the second switching device K2 is not specifically limited. For example, the second switching device K2 can be a mechanical switch (circuit breaker, disconnector, contactor and relay, etc.), a bidirectional semiconductor device (bidirectional thyristor, a pair of insulated-gate bipolar transistors (IGBTs) with common E or common C, a pair of metal-oxide-semiconductor field-effect transistors (MOSFETs) with common D or common S, etc.), or a switching device assembly with bidirectional current flow capability formed by combining multiple mechanical switches and semiconductor devices.
[0082] Based on the power converter provided in the above embodiments, this application also provides a power supply system, which will be described in detail below with reference to the accompanying drawings.
[0083] See Figure 6 The figure is a schematic diagram of a power supply system provided in an embodiment of this application.
[0084] like Figure 6 As shown, the power supply system provided in this application embodiment includes: a DC source 2000 and a power converter 1000 in any of the foregoing embodiments. The specific structure of the power converter 1000 will not be described here.
[0085] The input terminal of the power converter 1000 is connected to the DC source 2000, that is, the input terminal of the three-phase power conversion circuit is connected to the DC source 2000.
[0086] In this embodiment, the type of DC source 2000 is not specifically limited. For example, DC source 2000 can be a photovoltaic module, a battery, or a battery pack.
[0087] In addition, the power supply system in this embodiment may also include a DC / DC circuit. The first terminal of the DC / DC circuit is connected to a DC source 2000, and the second terminal of the DC / DC circuit is connected to the DC side of a three-phase power conversion circuit. The AC side of the three-phase power conversion circuit is used to connect to a load or the power grid.
[0088] In this embodiment of the application, when the power converter in the power supply system switches from a three-phase three-wire system to a three-phase four-wire system, an impedance network is connected in series in the N-line (the first end of the N-line is connected to the DC side of the three-phase power conversion circuit, and the second end of the N-line is connected to the neutral point of the load or the neutral point of the power grid) loop to reduce the inrush current in the N-line loop, thereby reducing the risk of damage to the switching devices in the power converter due to the N-line inrush current.
[0089] 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.
[0090] See Figure 7 The figure is a flowchart of a control method for a power converter provided in an embodiment of this application.
[0091] like Figure 7As shown in the embodiment of this application, the control method for a power converter includes an impedance network and a three-phase power conversion circuit. 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 is used to connect to a load or the power grid. The load and the power grid are both connected in a star configuration. The first end of the impedance network is connected to the DC side of the three-phase power conversion circuit, and the second end of the impedance network is used to connect to the neutral point of the load or the neutral point of the power grid.
[0092] The control method includes:
[0093] S710: Obtains the DC side voltage of the three-phase power conversion circuit, and the DC bias voltage of the AC side voltage relative to the negative terminal of the DC source.
[0094] In this embodiment, the method of obtaining the DC bias voltage is not specifically limited. For example, the DC bias voltage can be obtained through a voltage sampling circuit.
[0095] S720: When the absolute difference between the DC side voltage and the DC bias voltage is greater than a preset threshold, control the DC side voltage and / or the DC bias voltage so that the absolute difference between the DC side voltage and the DC bias voltage is less than the preset threshold.
[0096] In this embodiment, if the absolute difference between the DC side voltage and the DC bias voltage is greater than a preset threshold, it indicates that the inrush current on the N line may damage the switching devices in the power converter. When the AC side of the three-phase power conversion circuit is connected to a load, an impedance network is connected in the connection between the DC side of the three-phase power conversion circuit and the neutral point of the load to reduce the inrush current on the N line. When the AC side of the three-phase power conversion circuit is connected to the power grid, an impedance network is connected in the connection between the DC side of the three-phase power conversion circuit and the neutral point of the power grid to reduce the inrush current on the N line.
[0097] In one possible implementation, the power converter further includes a first switching device connected in parallel across the impedance network; the first switching device is turned on when the absolute difference between the DC side voltage and the DC bias voltage is less than a preset threshold.
[0098] It should be noted that the impedance network described in the embodiments of this application includes at least one of resistors, inductors, and capacitors.
[0099] For example, an impedance network may include individual resistors, inductors, or capacitors; an impedance network may also include capacitors and resistors in series, inductors and resistors in series, capacitors in series, resistors and inductors, capacitors and resistors in parallel, capacitors and resistors in parallel followed by an inductor, and capacitors and resistors in parallel followed by a capacitor.
[0100] See Figure 8 The figure is a schematic diagram of a control device provided in an embodiment of this application.
[0101] like Figure 8 As shown, the control device may include a memory 1011 and a processor 1012. The processor 1012 can be connected to the power converter and can drive the switches in the various power conversion circuits of the power converter. Figure 8 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.
[0102] 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 use them to execute control methods. The memory 1011 can also store data, such as preset ranges, preset thresholds, and other information involved in the above embodiments.
[0103] 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)).
[0104] 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.
[0105] 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.
[0106] 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, The power converter includes: an impedance network and a three-phase power conversion circuit, 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 used to connect to a load or a power grid; wherein the load is connected in a star configuration and the power grid is connected in a star configuration. The first end of the impedance network is connected to the positive DC side of the three-phase power conversion circuit, and the second end of the impedance network is used to connect to the neutral point of the load or the neutral point of the power grid.
2. The power converter according to claim 1, characterized in that, The power converter further includes: a controller; When the absolute difference between the AC side voltage of the three-phase power conversion circuit and the DC bias voltage of the DC source negative terminal is greater than a preset threshold, the controller controls the DC side voltage and / or the DC bias voltage so that the absolute difference between the DC side voltage and the DC bias voltage is less than the preset threshold.
3. The power converter according to claim 1, characterized in that, The power converter further includes: a controller and a first switching device; The first switching device is connected in parallel across the impedance network; The controller controls the first switching device to turn on when the absolute difference between the AC side voltage of the three-phase power conversion circuit and the DC bias voltage of the DC source negative terminal is greater than a preset threshold.
4. The power converter according to any one of claims 1-3, characterized in that, The impedance network includes at least one of resistors, inductors, and capacitors.
5. The power converter according to any one of claims 1-3, 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, an inductor, and an AC side capacitor; The first and second switching transistors are connected in series to form a first bridge arm, and the two ends of the first bridge arm are respectively connected to the positive and negative terminals of the DC source; the third and fourth switching transistors 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 output terminal of the power conversion circuit, the second end of the second bridge arm is connected to the negative terminal of the DC source, and the two ends of the AC side capacitor are respectively connected to the first end of the second bridge arm and the negative terminal of the DC source.
6. The power converter according to any one of claims 1-3, characterized in that, The power converter further includes: a second switching device; The second switching device is connected in series with the impedance network; The controller is also used to control the switching action of the second switching device to switch the operating mode of the power converter; wherein, when the second switching device is off, the power converter operates in a three-phase three-wire system, and when the second switching device is on, the power converter operates in a three-phase four-wire system.
7. A power supply system, characterized in that, The power system includes: a DC source and a power converter as described in any one of claims 1-6; wherein the DC source includes a photovoltaic module or a battery module; The DC side of the power converter is connected to the DC source.
8. A control method for a power converter, characterized in that, The power converter includes an impedance network and a three-phase power conversion circuit. 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 is used to connect to a load or the power grid. The first end of the impedance network is connected to the positive terminal of the DC side of the three-phase power conversion circuit, and the second end of the impedance network is used to connect to the neutral point of the load or the neutral point of the power grid. The load and the power grid are both connected in a star configuration. The method includes: Obtain the DC side voltage of the three-phase power conversion circuit, and the DC bias voltage of the AC side voltage relative to the negative terminal of the DC source; If the absolute difference between the DC-side voltage and the DC bias voltage is greater than a preset threshold, the DC-side voltage and / or the DC bias voltage are controlled so that the absolute difference between the DC-side voltage and the DC bias voltage is less than the preset threshold.
9. The method according to claim 8, characterized in that, The converter further includes a first switching device connected in parallel across the impedance network, and the method further includes: When the absolute difference between the DC side voltage and the DC bias voltage is greater than the preset threshold, the first switching device is controlled to turn on.
10. 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 claim 8 or 9.
11. 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 claim 8 or 9.