Power conversion device, uninterruptible power supply and photovoltaic inverter

Abstract

The embodiment of the invention discloses a power conversion device, an uninterruptible power supply and a photovoltaic inverter, relates to the technical field of power electronics, and solves the problems that an existing inverter is relatively low in efficiency and relatively high in device cost. According to the specific scheme, the power conversion device comprises at least one inverter circuit, each inverter circuit comprises a switching tube bridge arm, a first switching tube and an inductor, and each switching tube bridge arm comprises at least three switching tubes connected between a positive direct current bus and a negative direct current bus in series; the first switch tube is connected between a first node of the switch tube bridge arm and a connection point of the positive and negative bus capacitors, the inductor is connected with a second node of the switch tube bridge arm, and the first node and the second node are different in position in the switch tube bridge arm.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a power conversion device, an uninterruptible power supply and a photovoltaic inverter. Background Art

[0002] An inverter (INV) is used to convert direct current into alternating current. The types of the inverter include an I-shaped inverter and a T-shaped inverter. Currently, the I-shaped inverter and the T-shaped inverter have been widely used in various devices and systems, such as frequency converters and uninterruptible power supplies (UPS).

[0003] However, the current inverter efficiency is low and the device cost is high. How to improve the efficiency of the inverter and reduce the device cost of the inverter has become an urgent problem to be solved. Summary of the invention

[0004] The embodiments of the present application provide a power conversion device, an uninterruptible power supply and a photovoltaic inverter, which solve the problems of low efficiency and high device cost of current inverters.

[0005] In order to achieve the above purpose, the embodiment of the present application adopts the following technical solution:

[0006] According to a first aspect of an embodiment of the present application, a power conversion device is provided, which includes at least one inverter circuit, the inverter circuit including a switch tube bridge arm, a first switch tube and an inductor, the switch tube bridge arm including at least three switch tubes connected in series between a positive DC bus and a negative DC bus, the first switch tube is connected between a first node of the switch tube bridge arm and a connection point between positive and negative bus capacitors, the inductor is connected to a second node of the switch tube bridge arm, and the first node and the second node are at different positions in the switch tube bridge arm.

[0007] Based on this solution, the inverter circuit includes at least 4 switch tubes. Compared with the I-shaped inverter in the prior art that uses 4 switch tubes and 2 diodes, the inverter circuit uses fewer devices, which can reduce the board area, reduce costs, reduce losses, and improve efficiency. At the same time, the first switch tube is connected between the first node of the switch tube bridge arm and the connection point of the positive and negative bus capacitors, one end of the inductor is connected to the second node of the switch tube bridge arm, the first node and the second node are in different positions in the switch tube bridge arm, and the other end of the inductor is the AC output end. Compared with the I-shaped inverter and the T-shaped inverter in the prior art, the switch tube bridge arm is an asymmetric structure relative to the inductor, so that the withstand voltage value of the switch tube in the switch tube bridge arm can be different, and a switch tube with a smaller withstand voltage value can be used, and the device cost of the inverter circuit is lower, the switching loss is smaller, and the efficiency is higher.

[0008] In combination with the first aspect, in a possible implementation, the switch tube bridge arm includes a second switch tube, a third switch tube and a fourth switch tube connected in series, the series connection point of the second switch tube and the third switch tube is a first node, the series connection point of the third switch tube and the fourth switch tube is a second node, the withstand voltage of the fourth switch tube is greater than or equal to the bus voltage, and the withstand voltage of each switch tube except the fourth switch tube is greater than or equal to half of the bus voltage.

[0009] Based on this solution, the switch tube bridge arm includes a second switch tube, a third switch tube and a fourth switch tube connected in series, the series connection point of the second switch tube and the third switch tube is a first node, the series connection point of the third switch tube and the fourth switch tube is a second node, the fourth switch tube is included between the inductor and the positive DC bus, and the second switch tube and the third switch tube are included between the inductor and the negative DC bus, or the second switch tube and the third switch tube are included between the inductor and the positive DC bus, and the fourth switch is included between the inductor and the negative DC bus, so that the withstand voltage value of the fourth switch tube Q4 needs to be greater than or equal to the bus voltage, and the withstand voltage value of each switch tube except the fourth switch tube Q4 needs to be greater than or equal to half of the bus voltage. Compared with the two switch tubes set between the positive and negative DC buses in the T-shaped inverter, which both need to use switch tubes with higher withstand voltage values, the withstand voltage value of the fourth switch tube in the inverter circuit of the power conversion device is greater than or equal to the bus voltage, and the withstand voltage values ​​of the remaining switch tubes are greater than or equal to half of the bus voltage, and the device cost of the inverter circuit is lower, the switching loss is smaller, and the efficiency is higher.

[0010] In combination with the first aspect, in a possible implementation, the second switch tube is used to connect the positive DC bus, the fourth switch tube is used to connect the negative DC bus, and the drain or collector of the first switch tube is connected to the drain or collector of the third switch tube. When the third switch tube is turned on, and the second switch tube and the first switch tube are alternately turned on, the voltage of the AC power output by the inductor is greater than zero, and when the third switch tube and the first switch tube are turned on or off at the same time, and are alternately turned on with the fourth switch tube, the voltage of the AC power output by the inductor is less than zero.

[0011] Based on this solution, in each inverter circuit, when the third switch tube is turned on and the second switch tube and the first switch tube are turned on alternately, the voltage of the AC power output by the inductor is greater than zero; when the third switch tube and the first switch tube are turned on or off at the same time and are turned on alternately with the fourth switch tube, the voltage of the AC power output by the inductor is less than zero, so that each inverter circuit can convert direct current into alternating current.

[0012] In combination with the first aspect, in a possible implementation, the third switch tube includes a first transistor and a first diode connected in reverse parallel to the first transistor, the first switch tube includes a second transistor and a second diode connected in reverse parallel to the second transistor, and the cathode of the first diode is connected to the cathode of the second diode. When the voltage of the inductor outputting the alternating current is greater than zero, the second transistor is in an off state, and when the voltage of the inductor outputting the alternating current is less than zero, the first transistor is in an off state.

[0013] Based on this solution, when the voltage of the inductor outputting the alternating current is greater than zero, the second transistor is in the off state, and when the voltage of the inductor outputting the alternating current is less than zero, the first transistor is in the off state, thereby reducing the switching losses of the first switching tube and the third switching tube, and reducing the loss of each inverter circuit to reduce the loss of the power conversion device.

[0014] In combination with the first aspect, in a possible implementation, the second switch tube is used to connect the negative DC bus, the fourth switch tube is used to connect the positive DC bus, the drain or collector of the first switch tube is connected to the drain or collector of the third switch tube, or the source or emitter of the first switch tube is connected to the source or emitter of the third switch tube. When the third switch tube and the first switch tube are turned on or off at the same time, and are turned on alternately with the fourth switch tube, the voltage of the AC power output by the inductor is greater than zero, and when the third switch tube is turned on and the second switch tube and the first switch tube are turned on alternately, the voltage of the AC power output by the inductor is less than zero.

[0015] Based on this solution, when the third switch tube and the first switch tube are turned on or off at the same time, and are alternately turned on with the fourth switch tube, the voltage of the AC power output by the inductor is greater than zero; when the third switch tube is turned on and the second switch tube and the first switch tube are alternately turned on, the voltage of the AC power output by the inductor is less than zero, so that each inverter circuit can convert DC power into AC power.

[0016] In combination with the first aspect, in a possible implementation, the drain or collector of the first switch tube is connected to the drain or collector of the third switch tube, the third switch tube includes a first transistor and a first diode connected in reverse parallel to the first transistor, the first switch tube includes a second transistor and a second diode connected in reverse parallel to the second transistor, and the cathode of the first diode is connected to the cathode of the second diode. When the voltage of the inductor outputting the alternating current is greater than zero, the second transistor is in an off state, and when the voltage of the inductor outputting the alternating current is less than zero, the first transistor is in an off state.

[0017] Based on this solution, when the voltage of the inductor outputting the alternating current is greater than zero, the second transistor is in the off state, and when the voltage of the inductor outputting the alternating current is less than zero, the first transistor is in the off state, thereby reducing the switching losses of the first switching tube and the third switching tube, and reducing the loss of each inverter circuit to reduce the loss of the power conversion device.

[0018] In combination with the first aspect, in a possible implementation, the source or emitter of the first switch tube is connected to the source or emitter of the third switch tube, the third switch tube includes a first transistor and a first diode connected in reverse parallel to the first transistor, the first switch tube includes a second transistor and a second diode connected in reverse parallel to the second transistor, and the anode of the first diode is connected to the anode of the second diode. When the voltage of the inductor outputting the alternating current is greater than zero, the first transistor is in an off state, and when the voltage of the inductor outputting the alternating current is less than zero, the second transistor is in an off state.

[0019] Based on this solution, when the voltage of the inductor outputting the alternating current is greater than zero, the first transistor is in the off state, and when the voltage of the inductor outputting the alternating current is less than zero, the second transistor is in the off state, thereby reducing the switching losses of the first switch tube and the third switch tube, and reducing the loss of each inverter circuit to reduce the loss of the power conversion device.

[0020] In combination with the first aspect, in a possible implementation manner, each inverter circuit further includes a capacitor, one end of the capacitor is connected to the AC power output end of the inductor, and the other end of the capacitor is used to be connected to the neutral line.

[0021] Based on this solution, in each inverter circuit, the AC power output by the inductor is filtered by a capacitor, thereby reducing harmonics and noise in the AC power, reducing invalid losses, improving the quality of the AC power output by the inverter circuit, and improving the efficiency of the inverter circuit. Therefore, the power conversion device provided in the embodiment of the present application has lower losses and higher efficiency.

[0022] In combination with the first aspect, in a possible implementation, each inverter circuit further includes a heat-conducting component, and the fourth switch tube, the third switch tube, the second switch tube and the first switch tube are sequentially away from the air inlet and in contact with the heat-conducting component.

[0023] Optionally, types of the thermally conductive components include heat pipes, heat sinks, and metal heat sinks. The embodiments of the present application do not limit the specific types of the thermally conductive components.

[0024] Based on this solution, each inverter circuit also includes a heat-conducting component. The fourth switch tube, the third switch tube, the second switch tube and the first switch tube are successively away from the air inlet and in contact with the heat-conducting component, so that the temperature of each switch tube can be effectively reduced. At the same time, there is no need for each switch tube to correspond to an air inlet respectively, which can reduce the volume of the heat-conducting component, which is beneficial to improving the power density of the inverter circuit, thereby reducing the volume of the power conversion device, which is beneficial to improving the power density of the power conversion device.

[0025] In combination with the first aspect, in a possible implementation manner, the power conversion device includes a plurality of inverter circuits, and the AC power output ends of the inductors in the plurality of inverter circuits are connected.

[0026] Based on this solution, the power conversion device includes a plurality of inverter circuits, and the AC output ends of the inductors in the plurality of inverter circuits are connected, thereby increasing the output power of the inverter.

[0027] In combination with the first aspect, in a possible implementation manner, the power conversion device includes three inverter circuits, and the AC power output ends of the inductors in the three inverter circuits are respectively used to output one-phase AC power.

[0028] Based on this solution, the power conversion device includes three inverter circuits, and the AC output ends of the inductors in the three inverter circuits are respectively used to output one-phase AC power, thereby reducing the ripple of the AC power output by the three inverter circuits and improving the reliability of the power conversion device.

[0029] In combination with the first aspect, in a possible implementation, the power conversion device further includes a rectifier circuit, the input end of the rectifier circuit is connected to the input end of the power conversion device, the positive output end of the rectifier circuit is connected to the positive DC bus, and the negative output end of the rectifier circuit is connected to the negative DC bus. The rectifier circuit is used to convert the alternating current input from the input end of the power conversion device into direct current, and output the direct current to the inverter circuit, and the inverter circuit is used to convert the direct current into alternating current and output it to the output end of the power conversion device.

[0030] According to a second aspect of an embodiment of the present application, an uninterruptible power supply is provided, comprising at least one power conversion device, wherein the input end of each power conversion device is connected to the input end of the uninterruptible power supply, the output end of each power conversion device is connected to the output end of the uninterruptible power supply, and the output end of the uninterruptible power supply is used to connect to a load. The power conversion device is a power conversion device as described in the first aspect or any possible implementation of the first aspect.

[0031] Optionally, the uninterruptible power supply may be a single-phase uninterruptible power supply, or may be a three-phase uninterruptible power supply, which is not limited in the embodiments of the present application.

[0032] According to a third aspect of an embodiment of the present application, a photovoltaic inverter is provided, which includes a DCDC conversion circuit and a power conversion device, the power conversion device is used to convert the direct current output by the DCDC conversion circuit into alternating current, and the power conversion device is a power conversion device as described in the first aspect or any possible implementation of the first aspect.

[0033] The description of the second to third aspects in this application can refer to the detailed description of the first aspect; and the beneficial effects of the second to third aspects can refer to the analysis of the beneficial effects of the first aspect, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of a circuit topology of an I-shaped inverter;

[0035] Figure 2 It is a circuit topology diagram of a T-shaped inverter;

[0036] Figure 3 A schematic diagram of a circuit topology of an inverter provided in an embodiment of the present application;

[0037] Figure 4 A schematic diagram of a circuit topology of an inverter provided in an embodiment of the present application;

[0038] Figure 5 A schematic diagram of a circuit topology of an inverter provided in an embodiment of the present application;

[0039] Figure 6 A schematic diagram of a circuit topology of an inverter provided in an embodiment of the present application;

[0040] Figure 7 A schematic diagram of a circuit topology of an inverter provided in an embodiment of the present application;

[0041] Figure 8 A schematic diagram of a circuit topology of an inverter provided in an embodiment of the present application;

[0042] Fig. 9 A schematic diagram of a circuit topology of an inverter provided in an embodiment of the present application;

[0043] Fig.10 A schematic diagram of a circuit topology of an inverter provided in an embodiment of the present application;

[0044] Fig.11 A schematic diagram of a circuit topology of an inverter provided in an embodiment of the present application;

[0045] Fig.12 A schematic diagram of a circuit topology of a photovoltaic inverter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0046] The following will discuss the making and use of each embodiment in detail. However, it should be understood that many applicable inventive concepts provided by this application can be implemented in a variety of specific environments. The specific embodiments discussed are only used to illustrate the specific ways to implement and use this description and this technology, and do not limit the scope of this application.

[0047] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.

[0048] Various circuits or other components may be described or referred to as being "configured to" perform one or more tasks. In this case, "configured to" is used to imply structure by indicating that the circuit / component includes structure (e.g., circuitry) that performs the one or more tasks during operation. Thus, even when the specified circuit / component is not currently operational (e.g., not turned on), the circuit / component may be referred to as being configured to perform the task. Circuits / components used with the phrase "configured to" include hardware, such as circuits that perform an operation, etc.

[0049] The technical scheme in the embodiment of the present application will be described below in conjunction with the accompanying drawings in the embodiment of the present application. In the present application, "at least one" refers to one or more, and "multiple" refers to two or more. "And / or" describes the association relationship of the associated objects, indicating that there may be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following" or its similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b or c can represent: a, b, c, a and b, a and c, b and c or a, b and c, where a, b and c can be single or multiple. In addition, in the embodiment of the present application, the words "first", "second" and the like do not limit the quantity and order.

[0050] In this application, the words "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the words "exemplary" or "for example" is intended to present the related concepts in a concrete way.

[0051] Before introducing the embodiments of the present application, the technical terms and background technologies involved in the present application are first introduced.

[0052] Alternating conduction: refers to the conduction states of two or more switches being opposite to each other. For example, taking two switches being alternately conducted, when one switch is conducted, the other switch is in the off state.

[0053] Heat dissipation gradient distribution: refers to a continuous or discontinuous sequence of temperature changes inside or on the surface of an object, formed by the change of temperature with position.

[0054] like Figure 1 As shown in (a), it is a schematic diagram of a circuit topology of an I-shaped inverter 100. The two input terminals of the I-shaped inverter 100 are respectively used to connect a positive DC bus +BUS and a negative DC bus -BUS, and a positive and negative bus capacitor is connected between the positive DC bus +BUS and the negative DC bus -BUS, and the positive and negative bus capacitors include a first capacitor C1 and a second capacitor C2 connected in series, and the connection point of the positive and negative bus capacitors is connected to a neutral wire (N).

[0055] like Figure 1 As shown in (a), the I-shaped inverter 100 includes an inductor L, an upper bridge arm arranged between the positive DC bus +BUS and the first end of the inductor L, and a lower bridge arm arranged between the negative DC bus -BUS and the first end of the inductor L, wherein the upper bridge arm includes a first switch tube Q1 and a second switch tube Q2 connected in series, and the lower bridge arm includes a third switch tube Q3 and a fourth switch tube Q4 connected in series. Taking the first switch tube Q1 as an example, each switch tube includes an insulate-gate bipolar transistor (IGBT) and a first diode D1, the collector of the IGBT is connected to the cathode of the first diode D1, and the emitter of the IGBT is connected to the anode of the first diode D1. The I-shaped inverter also includes a second diode D2 and a third diode D3, the cathode of the second diode D2 is connected to the midpoint of the upper bridge arm, the anode of the third diode D3 is connected to the midpoint of the lower bridge arm, and the anode of the second diode D2 and the cathode of the third diode D3 are connected to the neutral line. The second end of the inductor L in the I-shaped inverter 100 is used to output alternating current. The I-shaped inverter 100 also includes a third capacitor C3 and a resistor R connected in parallel between the second end of the inductor L and the neutral line. The third capacitor C3 and the resistor R are used to filter the alternating current output from the second end of the inductor L.

[0056] like Figure 1 (b) is a schematic diagram of the conduction of the switch tube in the I-shaped inverter 100. Figure 1 (a) and Figure 1In (b), when the second switch tube Q2 is turned on and the first switch tube Q1 and the third switch tube Q3 are turned on alternately, the voltage of the AC power output from the second end of the inductor L will be greater than or equal to zero. When the third switch tube Q3 is turned on and the second switch tube Q2 and the fourth switch tube Q4 are turned on alternately, the voltage of the AC power output from the second end of the inductor L will be less than or equal to zero, so that the I-type inverter 100 can convert DC power into AC power.

[0057] like Figure 2 As shown in (a), it is a circuit topology diagram of a T-shaped inverter 200. The two input terminals of the T-shaped inverter 200 are respectively used to connect the positive DC bus +BUS and the negative DC bus -BUS. The positive DC bus +BUS and the negative DC bus -BUS are connected with positive and negative bus capacitors, and the positive and negative bus capacitors include a first capacitor C1 and a second capacitor C2 connected in series. The connection point of the positive and negative bus capacitors is connected to the neutral line.

[0058] like Figure 2 As shown in (a), the T-shaped inverter 200 includes an inductor L, a first switch tube Q1 arranged between the positive DC bus +BUS and the first end of the inductor L, a second switch tube Q2 arranged between the negative DC bus -BUS and the first end of the inductor L, and a switch tube bridge arm arranged between the connection point of the positive and negative bus capacitors and the first end of the inductor L, the switch tube bridge arm includes a third switch tube Q3 and a fourth switch tube Q4 connected in series, the drain or collector of the third switch tube Q3 is connected to the drain or collector of the fourth switch tube Q4, so that the switch tube bridge arm can be completely turned off. Taking the first switch tube Q1 as an example, each switch tube includes an IGBT and a diode D, the collector of the IGBT is connected to the negative electrode of the diode D, and the emitter of the IGBT is connected to the positive electrode of the diode D. Among them, the negative electrode of the diode D in the third switch tube Q3 is connected to the negative electrode of the diode D in the fourth switch tube, so that the switch tube bridge arm can be completely turned off. The second end of the inductor L in the T-shaped inverter 200 is used to output alternating current. The T-shaped inverter 200 also includes a third capacitor C3 and a resistor R connected in parallel between the second end of the inductor L and the neutral line. The third capacitor C3 and the resistor R are used to filter the alternating current output from the second end of the inductor L.

[0059] like Figure 2 (b) is a schematic diagram of the conduction of the switch tube in the T-shaped inverter 200. Figure 2 (a) and Figure 2In (b), when the fourth switch tube Q4 is turned on and the first switch tube Q1 and the third switch tube Q3 are turned on alternately, the voltage of the AC power output from the second end of the inductor L will be greater than zero; when the third switch tube Q3 is turned on and the second switch tube Q2 and the fourth switch tube Q4 are turned on alternately, the voltage of the AC power output from the second end of the inductor L will be less than zero, so that the T-type inverter 200 can convert DC power into AC power.

[0060] Compared with the T-shaped inverter 200 using 4 switching tubes, the I-shaped inverter 100 needs to use 4 switching tubes and 2 diodes. The I-shaped inverter 100 uses more devices, which will result in a large board area, higher cost, higher loss and lower efficiency. Although the T-shaped inverter 200 uses four switch tubes and occupies a small board area, the withstand voltage value of the first switch tube Q1 and the withstand voltage value of the second switch tube Q2 in the T-shaped inverter 200 must be greater than or equal to the bus voltage, which is the voltage difference between the positive DC bus +BUS and the negative DC bus -BUS. The first switch tube Q1 and the second switch tube Q2 must both use switch tubes with higher withstand voltage values. For example, taking the bus voltage as 800V, the first switch tube Q1 and the second switch tube Q2 must both use switch tubes with a withstand voltage value of 1200V. The higher the withstand voltage value of the switch tube, the higher the price and switching loss of the switch tube will be, which will result in higher cost and loss and lower efficiency of the T-shaped inverter 200.

[0061] In summary, both the I-shaped inverter 100 and the T-shaped inverter 200 have the problems of high loss, low efficiency and high cost. Based on this, the embodiment of the present application provides a power conversion device, in which each inverter circuit of the power conversion device uses at least 4 switch tubes, thereby reducing the board area, reducing the cost, reducing the loss and improving the efficiency.

[0062] like Figure 3 (a) is a schematic diagram of a circuit topology of a power conversion device 300 provided in an embodiment of the present application. The power conversion device 300 includes at least one inverter circuit. The embodiment of the present application does not limit the specific number of inverter circuits included in the power conversion device 300. Figure 3 (a) in the figure is exemplified by taking the power conversion device 300 including the first inverter circuit 310 as an example.

[0063] Reference Figure 3In (a), the first inverter circuit 310 includes a switch tube bridge arm 311, a first switch tube Q1 and an inductor L. The switch tube bridge arm 311 includes at least three switch tubes connected in series between a positive DC bus +BUS and a negative DC bus -BUS. The embodiment of the present application does not limit the specific number of switch tubes included in the switch tube bridge arm 311. In the following embodiment of the present application, the switch tube bridge arm 311 includes a second switch tube Q2, a third switch tube Q3 and a fourth switch tube Q4 connected in series as an example for exemplary description.

[0064] Among them, refer to Figure 3 As shown in (a), positive and negative bus capacitors are connected between the positive DC bus +BUS and the negative DC bus -BUS, and the positive and negative bus capacitors include a first capacitor C1 and a second capacitor C2 connected in series, and the connection point of the positive and negative bus capacitors is connected to the neutral line. In the switch tube bridge arm 311, the series connection point of the second switch tube Q2 and the third switch tube Q3 is the first node A of the switch tube bridge arm 311, and the series connection point of the third switch tube Q3 and the fourth switch tube Q4 is the second node B of the switch tube bridge arm 311. The first node A and the second node B are in different positions in the switch tube bridge arm 311. The first switch tube Q1 is connected between the first node A of the switch tube bridge arm 311 and the connection point of the positive and negative bus capacitors, and the inductor L is connected to the second node B of the switch tube bridge arm 311. Compared with the above-mentioned I-shaped inverter 100 using 4 switching tubes and 2 diodes, the first inverter circuit 310 includes 4 switching tubes and uses fewer devices, which can reduce the board area, reduce costs, reduce losses, and improve efficiency.

[0065] Optionally, the second switch tube Q2 can be used to connect the positive DC bus +BUS, and the fourth switch tube Q4 can be used to connect the negative DC bus -BUS, or the second switch tube Q2 can be used to connect the negative DC bus -BUS, and the fourth switch tube Q4 can be used to connect the positive DC bus +BUS. This embodiment of the present application is not limited to this. Figure 3 (a) is described by taking the example that the second switch tube Q2 is connected to the positive DC bus +BUS and the fourth switch tube Q4 is connected to the negative DC bus -BUS.

[0066] Among them, the withstand voltage of the fourth switch tube Q4 is greater than or equal to the bus voltage, and the withstand voltage of each switch tube except the fourth switch tube Q4 is greater than or equal to half of the bus voltage, and the bus voltage is the voltage difference between the positive DC bus +BUS and the negative DC bus -BUS.

[0067] Reference Figure 3In (a), it can be understood that since the second node B is connected to one end of the inductor L, and the other end of the inductor L is the output end of the first inverter circuit 310, the switch tube between the second node B and the positive DC bus +BUS, the negative DC bus -BUS or the connection point of the positive and negative bus capacitors needs to be able to withstand the bus voltage. In the first inverter circuit 310, the positive DC bus +BUS and the second node B include the second switch tube Q2 and the third switch tube Q3 connected in series, the connection point of the positive and negative bus capacitors and the second node B include the first switch tube Q1 and the third switch tube Q3 connected in series, and the negative DC bus -BUS and the second node B include the fourth switch tube Q4, so that the withstand voltage value of the fourth switch tube Q4 needs to be greater than or equal to the bus voltage, and the withstand voltage value of each switch tube except the fourth switch tube Q4 needs to be greater than or equal to half of the bus voltage. Compared with the above-mentioned T-shaped inverter 200 in which both the first switch tube Q1 and the second switch tube Q2 need to use switch tubes with higher withstand voltage values, the withstand voltage value of the fourth switch tube Q4 in the first inverter circuit 310 is greater than or equal to the bus voltage, and the withstand voltage values ​​of the remaining switch tubes are greater than or equal to half of the bus voltage. The device cost of the first inverter circuit 310 is lower, the switching loss is smaller, and the efficiency is higher.

[0068] For example, taking the bus voltage as 800V, the withstand voltage of the fourth switch tube Q4 may be 1200V, and except for the fourth switch tube Q4, the withstand voltage of each of the first switch tube Q1, the second switch tube Q2 and the third switch tube Q3 may be 650V.

[0069] In a possible embodiment, the drain or collector of the first switch tube Q1 is connected to the drain or collector of the third switch tube Q3, so that the first switch tube Q1 and the third switch tube Q3 can completely cut off the path between the inductor L and the neutral line. Figure 3 (b) in FIG. 1 is a schematic diagram of a waveform curve of the alternating current output by the inductor L in the power conversion device 300, as shown in FIG. Figure 3 (c) in the figure shows a schematic diagram of the conduction of the switch tube in the power conversion device 300. Figure 3 (a) Figure 3 (b) and Figure 3 In (c), when the third switch tube Q3 is turned on, and the second switch tube Q2 and the first switch tube Q1 are alternately turned on, the voltage of the AC power output by the inductor L is greater than zero; when the third switch tube Q3 and the first switch tube Q1 are turned on or off at the same time, and are alternately turned on with the fourth switch tube Q4, the voltage of the AC power output by the inductor L is less than zero, so that the first inverter circuit 310 can convert DC power into AC power.

[0070] Optionally, each switch tube may include a transistor or a transistor and a diode. Specifically, each switch tube may include an IGBT and a diode, the collector of the IGBT is connected to the cathode of the diode, and the emitter of the IGBT is connected to the anode of the diode, or each switch tube may include a metal-oxide-semiconductor field-effect transistor (MOSFET), which may also be referred to as a MOS tube, and each MOS tube includes a reverse-biased body diode. The embodiments of the present application are not limited to this. The following embodiments of the present application are exemplified by taking each switch tube including an IGBT and a diode as an example.

[0071] In one possible embodiment, referring to Figure 3 In (a), each switch tube includes an IGBT and a diode as an example. Figure 4 (a) in FIG. 1 is another circuit topology diagram of the power conversion device 300. Figure 4 In (a), the third switch tube Q3 includes a first transistor IGBT1 and a first diode D1 connected in reverse parallel to the first transistor IGBT1. The first switch tube Q1 includes a second transistor IGBT2 and a second diode D2 connected in reverse parallel to the second transistor IGBT2. The collector of the first transistor IGBT1 is connected to the collector of the second transistor IGBT2, and the cathode of the first diode D1 is connected to the cathode of the second diode D2. The second switch tube Q2 includes a third transistor IGBT3 and a third diode D3 connected in reverse parallel to the third transistor IGBT3. The fourth switch tube Q4 includes a fourth transistor IGBT4 and a fourth diode D4 connected in reverse parallel to the fourth transistor IGBT4.

[0072] like Figure 4 (b) in FIG. 1 is a schematic diagram of a waveform curve of the alternating current output by the inductor L in the power conversion device 300, as shown in FIG. Figure 4 (c) in FIG. 1 is a schematic diagram showing the conduction of the switch tube in the power conversion device 300. Figure 4 (a) and Figure 4 (b) in Figure 4 As shown in (c) above, Figure 3Compared with the switch tube conduction schematic diagram in the power conversion device 300 shown in (c) in FIG, when the voltage of the AC power output by the inductor L is greater than zero, the second transistor IGBT2 in the first switch tube Q1 is always in the off state, and the second diode D2 is used for freewheeling; when the voltage of the AC power output by the inductor L is less than zero, the first transistor IGBT1 in the third switch tube Q3 is always in the off state, and the first diode D1 is used for freewheeling, thereby reducing the switching losses of the first switch tube Q1 and the third switch tube Q3, and reducing the loss of the first inverter circuit 310.

[0073] Specific, combined Figure 4 (a) Figure 4 (b) and Figure 4 (c) in the positive half cycle of the inductor L outputting AC power: when the third switch tube Q3 and the second switch tube Q2 are turned on, the current output by the positive DC bus +BUS charges the inductor L through the second switch tube Q2 and the third switch tube Q3 in turn, and the voltage of the AC power output by the inductor L will be greater than zero. When the third switch tube Q3 is turned on and the second switch tube Q2 is turned off, the inductor L discharges, and the current flows from the zero line through the second diode D2 in the first switch tube Q1 and the third switch tube Q3 to the inductor L in turn, and the voltage of the AC power output by the inductor L will be greater than zero. It can be understood that, as mentioned above Figure 3 Compared with the schematic diagram of switch tube conduction in the power conversion device 300 shown in (c), when the second switch tube Q2 is disconnected and the inductor L is discharged, the second transistor IGBT2 in the first switch tube Q1 is always in the off state, and can be continued through the second diode D2 in the first switch tube Q1. The second transistor IGBT2 in the first switch tube Q1 is always in the off state, and the first switch tube Q1 does not need to be turned on alternately with the second switch tube Q2, thereby reducing the switching loss of the first switch tube Q1 and reducing the loss of the first inverter circuit 310.

[0074] Continue to combine Figure 4 (a) Figure 4 (b) and Figure 4 (c) in the figure, in the negative half cycle of the inductor L outputting the alternating current: when the fourth switch tube Q4 is turned on, the current flows from the inductor L through the fourth switch tube Q4 to the negative DC bus -BUS, the inductor L is charged, and the voltage of the alternating current output by the inductor L will be less than zero. When the fourth switch tube Q4 is turned off and the first switch tube Q1 is turned on, the inductor L discharges, and the current flows from the inductor L to the neutral line through the first diode D1 in the third switch tube Q3 and the third switch tube Q3 in turn, and the voltage of the alternating current output by the inductor L will be less than zero. It can be understood that in the negative half cycle of the inductor L outputting the alternating current, the first switch tube Q1 and the fourth switch tube Q4 are turned on alternately. As mentioned above Figure 3Compared with the driving signal curve shown in (c) in FIG, when the fourth switch tube Q4 is disconnected and the inductor L is discharged, the first transistor IGBT1 in the third switch tube Q3 is always in the disconnected state, and the first diode D1 in the third switch tube Q3 can be used for freewheeling. The first transistor IGBT1 in the third switch tube Q3 is always in the disconnected state, and the third switch tube Q3 does not need to be turned on alternately with the fourth switch tube Q4, thereby reducing the switching loss of the third switch tube Q3 and reducing the loss of the first inverter circuit 310.

[0075] In a possible embodiment, Figure 5 (a) in FIG. 1 is another circuit topology diagram of the power conversion device 300. Figure 5 In (a), the second switch tube Q2 is used to connect the negative DC bus -BUS, the fourth switch tube Q4 is used to connect the positive DC bus +BUS, the drain or collector of the first switch tube Q1 is connected to the drain or collector of the third switch tube Q3, or the source or emitter of the first switch tube Q1 is connected to the source or emitter of the third switch tube Q3, and the embodiment of the present application does not limit this, so that the first switch tube Q1 and the third switch tube Q3 can completely shut off the path between the inductor L and the neutral line. Figure 5 (b) in FIG. 1 is a schematic diagram of a waveform curve of the alternating current output by the inductor L in the power conversion device 300, as shown in FIG. Figure 5 (c) in FIG. 1 is a schematic diagram showing the conduction of the switch tube in the power conversion device 300. Figure 5 (a) Figure 5 (b) and Figure 5 In (c), when the third switch tube Q3 and the first switch tube Q1 are turned on or off at the same time, and are alternately turned on with the fourth switch tube Q4, the voltage of the AC power output by the inductor L will be greater than zero. When the third switch tube Q3 is turned on and the second switch tube Q2 and the first switch tube Q1 are alternately turned on, the voltage of the AC power output by the inductor L will be less than zero, so that the first inverter circuit 310 can convert DC power into AC power.

[0076] In one possible embodiment, referring to Figure 5 In (a), each switch tube includes an IGBT and a diode as an example. Figure 6 (a) in FIG. 1 is another circuit topology diagram of the power conversion device 300. Figure 6In (a), the third switch tube Q3 includes a first transistor IGBT1 and a first diode D1 connected in reverse parallel to the first transistor IGBT1. The first switch tube Q1 includes a second transistor IGBT2 and a second diode D2. The collector of the first transistor IGBT1 is connected to the collector of the second transistor IGBT2, and the cathode of the first diode D1 is connected to the cathode of the second diode D2. The second switch tube Q2 includes a third transistor IGBT3 and a third diode D3 connected in reverse parallel to the third transistor IGBT3. The fourth switch tube Q4 includes a fourth transistor IGBT4 and a fourth diode D4 connected in reverse parallel to the fourth transistor IGBT4.

[0077] like Figure 6 (b) in FIG. 1 is a schematic diagram of a waveform curve of the alternating current output by the inductor L in the power conversion device 300, as shown in FIG. Figure 6 (c) in FIG. 1 is a schematic diagram showing the conduction of the switch tube in the power conversion device 300. Figure 6 (a) and Figure 6 (b) in Figure 6 As shown in (c) above, Figure 5 Compared with the switch tube conduction schematic diagram in the power conversion device 300 shown in (c) in FIG, when the voltage of the AC power output by the inductor L is greater than zero, the second transistor IGBT2 in the first switch tube Q1 is always in the off state, and the second diode D2 is used for freewheeling; when the voltage of the AC power output by the inductor L is less than zero, the first transistor IGBT1 in the third switch tube Q3 is always in the off state, and the first diode D1 is used for freewheeling, thereby reducing the switching losses of the first switch tube Q1 and the third switch tube Q3, and reducing the loss of the first inverter circuit 310.

[0078] Specific, combined Figure 6 (a) Figure 6 (b) and Figure 6 (c) in the positive half cycle of the inductor L outputting AC power: when the fourth switch tube Q4 is turned on, the current output by the positive DC bus + BUS charges the inductor L through the fourth switch tube Q4, and the voltage of the AC power output by the inductor L will be greater than zero. When the fourth switch tube Q4 is turned off and the third switch tube Q3 is turned on, the inductor L discharges, and the current flows from the zero line through the second diode D2 in the first switch tube Q1 and the third switch tube Q3 to the inductor L, and the voltage of the AC power output by the inductor L will be greater than zero. It can be understood that, as mentioned above Figure 5Compared with the schematic diagram of switch tube conduction in the power conversion device 300 shown in (c), when the fourth switch tube Q4 is disconnected and the inductor L is discharged, the second transistor IGBT2 in the first switch tube Q1 is always in the off state, and the second diode D2 in the first switch tube Q1 can be used for continuous current flow. The first switch tube Q1 does not need to be turned on alternately with the fourth switch tube Q4, thereby reducing the switching loss of the first switch tube Q1 and reducing the loss of the first inverter circuit 310.

[0079] Continue to combine Figure 6 (a) Figure 6 (b) and Figure 6 (c) in the figure, in the negative half cycle of the inductor L outputting the alternating current: when the second switch tube Q2 is turned on, the current flows from the inductor L to the negative DC bus -BUS through the first diode D1 and the second switch tube Q2 in the third switch tube Q3 in turn, the inductor L is charged, and the voltage of the alternating current output by the inductor L will be less than zero. When the second switch tube Q2 is turned off and the first switch tube Q1 is turned on, the inductor L is discharged, and the current flows from the inductor L to the neutral line through the first diode D1 and the first switch tube Q1 in the third switch tube Q3 in turn, and the voltage of the alternating current output by the inductor L will be less than zero. It can be understood that in the negative half cycle of the inductor L outputting the alternating current, the second switch tube Q2 and the first switch tube Q1 are turned on alternately. As mentioned above Figure 5 Compared with the switch tube conduction schematic diagram in the power conversion device 300 shown in (c), when the second switch tube Q2 and the first switch tube Q1 are alternately turned on and the inductor L is charged and discharged, the first transistor IGBT1 clock in the third switch tube Q3 is in the off state, and the first diode D1 in the third switch tube Q3 can be used for continuous current flow. The third switch tube Q3 does not need to be in the on state all the time, thereby reducing the switching loss of the third switch tube Q3 and reducing the loss of the first inverter circuit 310.

[0080] In one possible embodiment, referring to Figure 5 In (a), each switch tube includes an IGBT and a diode as an example. Figure 7 (a) in FIG. 1 is another circuit topology diagram of the power conversion device 300. Figure 7In (a), the third switch tube Q3 includes a first transistor IGBT1 and a first diode D1 connected in reverse parallel to the first transistor IGBT1. The first switch tube Q1 includes a second transistor IGBT2 and a second diode D2 connected in reverse parallel to the second transistor IGBT2. The emitter of the first transistor IGBT1 is connected to the emitter of the second transistor IGBT2, and the anode of the first diode D1 is connected to the anode of the second diode D2. The second switch tube Q2 includes a third transistor IGBT3 and a third diode D3 connected in reverse parallel to the third transistor IGBT3. The fourth switch tube Q4 includes a fourth transistor IGBT4 and a fourth diode D4 connected in reverse parallel to the fourth transistor IGBT4.

[0081] like Figure 7 (b) in FIG. 1 is a schematic diagram of a waveform curve of the alternating current output by the inductor L in the power conversion device 300, as shown in FIG. Figure 7 (c) in FIG. 1 is a schematic diagram showing the conduction of the switch tube in the power conversion device 300. Figure 7 (a) and Figure 7 (b) in Figure 7 As shown in (c) above, Figure 5 Compared with the switch tube conduction schematic diagram in the power conversion device 300 shown in (c) in FIG, when the voltage of the AC power output by the inductor L is greater than zero, the first transistor IGBT1 in the third switch tube Q3 is always in the off state, and the first diode D1 is used for freewheeling; when the voltage of the AC power output by the inductor L is less than zero, the second transistor IGBT2 in the first switch tube Q1 is always in the off state, and the second diode D2 is used for freewheeling, thereby reducing the switching losses of the third switch tube Q3 and the first switch tube Q1, and reducing the loss of the first inverter circuit 310.

[0082] Specific, combined Figure 7 (a) Figure 7 (b) and Figure 7 In (c), in the positive half cycle of the inductor L outputting AC power: when the fourth switch tube Q4 is turned on, the current output by the positive DC bus + BUS charges the inductor L through the fourth switch tube Q4, and the voltage of the AC power output by the inductor L will be greater than zero. When the fourth switch tube Q4 is turned off and the first switch tube Q1 is turned on, the inductor L discharges, and the current flows from the zero line to the inductor L through the first switch tube Q1 and the first diode D1 in the third switch tube Q3, and the voltage of the AC power output by the inductor L will be greater than zero. It can be understood that the above Figure 5Compared with the schematic diagram of switch tube conduction in the power conversion device 300 shown in (c), when the fourth switch tube Q4 is disconnected and the inductor L is discharged, the first transistor IGBT1 in the third switch tube Q3 is always in the off state, and the first diode D1 in the third switch tube Q3 can be used for freewheeling. The third switch tube Q3 does not need to be turned on alternately with the fourth switch tube Q4, thereby reducing the switching loss of the third switch tube Q3 and reducing the loss of the first inverter circuit 310.

[0083] Continue to combine Figure 7 (a) Figure 7 (b) and Figure 7 (c) in the figure, in the negative half cycle of the inductor L outputting the alternating current: when the second switch tube Q2 and the third switch tube Q3 are turned on, the current flows from the inductor L to the negative DC bus -BUS through the third switch tube Q3 and the second switch tube Q2 in sequence, the inductor L is charged, and the voltage of the alternating current output by the inductor L will be less than zero. When the second switch tube Q2 is disconnected and the third switch tube Q3 is turned on, the inductor L is discharged, and the current flows from the inductor L to the neutral line through the third switch tube Q3 and the second diode D2 in the first switch tube Q1 in sequence, and the voltage of the alternating current output by the inductor L will be less than zero. It can be understood that, similar to the above Figure 5 Compared with the schematic diagram of switch tube conduction in the power conversion device 300 shown in (c), when the second switch tube Q2 is disconnected and the inductor L is discharged, the second transistor IGBT2 in the first switch tube Q1 is always in the off state, and can be continued through the second diode D2 in the first switch tube Q1. The first switch tube Q1 does not need to be turned on alternately with the second switch tube Q2, thereby reducing the switching loss of the third switch tube Q3 and reducing the loss of the first inverter circuit 310.

[0084] In a possible embodiment, when the power conversion device 300 is applied to a solar power generation system, the power conversion device 300 may also be called a solar single-phase inverter.

[0085] In the power conversion device 300 provided in the embodiment of the present application, the first inverter circuit 310 uses 4 switch tubes. Compared with the above-mentioned I-shaped inverter 100 using 4 switch tubes and 2 diodes, the first inverter circuit 310 uses fewer devices, which can reduce the board area, reduce costs, reduce losses, and improve efficiency. Compared with the above-mentioned T-shaped inverter 200, in which both the first switch tube Q1 and the second switch tube Q2 need to use switch tubes with higher withstand voltage values, the withstand voltage value of the fourth switch tube Q4 in the first inverter circuit 310 is greater than or equal to the bus voltage, and the withstand voltage values ​​of the remaining switch tubes are greater than or equal to half of the bus voltage. The device cost of the first inverter circuit 310 is lower, the switching loss is smaller, and the efficiency is higher. Therefore, the power conversion device 300 provided in the embodiment of the present application occupies a smaller board area, has lower costs, lower losses, and higher efficiency.

[0086] In a possible embodiment, the circuit topology of the power conversion device 300 is as follows: Figure 4 Taking the circuit topology of the power conversion device 300 shown in (a) as an example, Figure 4 As shown in (a) of FIG. 3 , the first inverter circuit 310 further includes a capacitor C, one end of which is connected to the AC output end of the inductor L, and the other end of which is connected to the neutral line. The capacitor C is used to filter the AC output by the inductor L, thereby reducing harmonics and noise in the AC, reducing ineffective losses, improving the quality of the AC output by the first inverter circuit 310, and improving the efficiency of the first inverter circuit 310.

[0087] In the power conversion device 300 provided in the embodiment of the present application, the first inverter circuit 310 also includes a capacitor C, and the capacitor C is used to filter the alternating current output by the inductor L, so as to reduce harmonics and noise in the alternating current, reduce invalid losses, improve the quality of the alternating current output by the first inverter circuit 310, and improve the efficiency of the first inverter circuit 310. Therefore, the power conversion device 300 provided in the embodiment of the present application has lower losses and higher efficiency.

[0088] In a possible embodiment, each inverter circuit further includes a heat conducting component, such as Figure 8 As shown, taking the first inverter circuit 310 as an example, the first inverter circuit 310 also includes a heat-conducting component 312 , and the fourth switch tube Q4 , the third switch tube Q3 , the second switch tube Q2 and the first switch tube Q1 are sequentially away from the air inlet and in contact with the heat-conducting component 312 . Since the withstand voltage of the fourth switch tube Q4 is greater than or equal to the bus voltage, the withstand voltage of each switch tube except the fourth switch tube Q4 is greater than or equal to half of the bus voltage, the withstand voltage of the fourth switch tube Q4 is higher, and the withstand voltages of the remaining switch tubes are smaller. The switching loss and conduction loss of the fourth switch tube Q4 are higher and the heat is larger, while the switching loss and conduction loss of the remaining switch tubes are lower and the heat is smaller. Combined with the gradient heat dissipation distribution, the fourth switch tube Q4 is arranged on the side of the heat-conducting component 312 close to the air inlet, and the remaining switch tubes are arranged in sequence on the side of the heat-conducting component 312 away from the air inlet, which can effectively reduce the temperature of each switch tube. At the same time, there is no need for each switch tube to correspond to an air inlet respectively, which can reduce the volume of the heat-conducting component 312, which is beneficial to improve the power density of the first inverter circuit 310.

[0089] Optionally, types of the thermal conductive component 312 include heat pipes, heat sinks, and metal heat sinks. The embodiment of the present application does not limit the specific type of the thermal conductive component 312.

[0090] In a possible embodiment, the heat conducting component 312 and the first to fourth switch tubes Q1 to Q4 may be inserted on a printed circuit board (PCB).

[0091] In the power conversion device 300 provided in the embodiment of the present application, the first inverter circuit 310 also includes a heat-conducting component 312. The fourth switch tube Q4, the third switch tube Q3, the second switch tube Q2 and the first switch tube Q1 are successively away from the air inlet and arranged on the heat-conducting component 312, so that the temperature of each switch tube can be effectively reduced. At the same time, there is no need for each switch tube to correspond to an air inlet respectively, and the volume of the heat-conducting component 312 can be reduced, which is beneficial to improving the power density of the first inverter circuit 310, thereby reducing the volume of the power conversion device 300, which is beneficial to improving the power density of the power conversion device 300.

[0092] In a possible embodiment, the power conversion device 300 includes a plurality of inverter circuits, and the circuit topology of each inverter circuit is as follows: Figure 4 Taking the circuit topology of the first inverter circuit 310 shown in (a) as an example, Fig. 9 As shown, the power conversion device 300 may further include a second inverter circuit 320, and the AC output end of the inductor L in the first inverter circuit 310 is connected to the AC output end of the inductor L in the second inverter circuit 320, thereby increasing the output power of the power conversion device 300.

[0093] Exemplarily, when the power conversion device 300 is applied to a solar power generation system, the AC power output end of the inductor L in the first inverter circuit 310 is connected to the AC power output end of the inductor L in the second inverter circuit 320, which can increase the output power of the power conversion device 300 and the output power of the solar power generation system.

[0094] In a possible embodiment, Fig. 9 As shown, the first inverter circuit 310 and the second inverter circuit 320 can share a capacitor C, thereby reducing the cost of the power conversion device 300.

[0095] In the power conversion device 300 provided in the embodiment of the present application, the AC output end of the inductor L in the first inverter circuit 310 is connected to the AC output end of the inductor L in the second inverter circuit 320, thereby increasing the output power of the power conversion device 300.

[0096] In a possible embodiment, the power conversion device 300 includes three inverter circuits, and the circuit topology of each inverter circuit is as follows: Figure 4 Taking the circuit topology of the first inverter circuit 310 shown in (a) as an example, Fig.10As shown in (a), the power conversion device 300 also includes a second inverter circuit 320 and a third inverter circuit 330. The AC output ends of the inductors L in the three inverter circuits are respectively used to output one-phase AC power, thereby reducing the ripple of the AC power output by the three inverters and improving the reliability of the power conversion device 300.

[0097] like Fig.10 (b) in FIG. 1 is a schematic diagram of a waveform curve of the AC power output by the inductor L in each inverter circuit. The inductor L in the first inverter circuit 310 is used to output A-phase AC power, the inductor L in the second inverter circuit 320 is used to output B-phase AC power, and the inductor L in the third inverter circuit 330 is used to output C-phase AC power. The phase difference between the three-phase AC power is 120°. Fig.10 (c) in the figure shows a schematic diagram of the conduction of the switch tubes in the first inverter circuit 310, the second inverter circuit 320 and the third inverter circuit 330 in the power conversion device 300. The specific working principle of the switch tube in each inverter circuit can be referred to above. Figure 4 The related description of (c) in the present application will not be repeated here.

[0098] In a possible embodiment, the circuit topology of each inverter is as follows: Figure 6 Taking the circuit topology of the first inverter circuit 310 shown in (a) as an example, the circuit topology of the power conversion device 300 can be as follows Fig.11 As shown in (a) in Fig.11 (b) in FIG. 1 is a schematic diagram of a waveform curve of the AC power output by the inductor L in each inverter circuit. The inductor L in the first inverter circuit 310 is used to output A-phase AC power, the inductor L in the second inverter circuit 320 is used to output B-phase AC power, and the inductor L in the third inverter circuit 330 is used to output C-phase AC power. The phase difference between the three-phase AC power is 120°. Fig.11 (c) in the figure shows a schematic diagram of the conduction of the switch tubes in the first inverter circuit 310, the second inverter circuit 320 and the third inverter circuit 330 in the power conversion device 300. The specific working principle of the switch tube in each inverter circuit can be referred to above. Figure 6 The related description of (b) in the present embodiment of the application will not be repeated here.

[0099] The power conversion device 300 provided in the embodiment of the present application includes three inverter circuits, and the AC output ends of the inductors L in the three inverter circuits are respectively used to output one-phase AC power, thereby reducing the ripple of the AC power output by the three inverters and improving the reliability of the power conversion device 300.

[0100] In a possible embodiment, Figure 4 (a) or Figure 6As shown in (a), the power conversion device 300 provided in the embodiment of the present application includes a first rectifier circuit 340, the input end of the first rectifier circuit 340 is connected to the input end of the power conversion device 300, the positive output end of the first rectifier circuit 340 is connected to the positive DC bus +BUS, and the negative output end of the first rectifier circuit 340 is connected to the negative DC bus -BUS. The first rectifier circuit 340 is used to convert the AC power input from the input end of the power conversion device 300 into DC power, and output the DC power to the first inverter circuit 310, and the first inverter circuit 310 is used to convert the DC power into AC power and output it to the output end of the power conversion device 300.

[0101] Optionally, the power conversion device 300 may include one first rectifier circuit 340 , or may include multiple rectifier circuits, which is not limited in the embodiment of the present application.

[0102] For example, Fig.10 (a) or Fig.11 As shown in (a) of FIG. 8 , the power conversion device 300 may include a second rectifier circuit 350 and a third rectifier circuit 360 in addition to the first rectifier circuit 340 .

[0103] In a possible embodiment, Figure 4 (a) Figure 6 (a) Fig.10 (a) or Fig.11 As shown in (a), each rectifier circuit includes an inductor La, a diode bridge arm and a switch tube bridge arm, the diode bridge arm includes two diodes Da and Db connected in series, the positive electrode of diode Da is connected to the negative electrode of diode Db, the inductor La is connected between the midpoint of the diode bridge arm and the AC input end, the switch tube bridge arm is connected between the midpoint of the diode bridge arm and the neutral line, the switch tube bridge arm includes two switch tubes S1 and S2 connected in series, the drain or collector of switch tube S1 is connected to the drain or collector of switch tube S2, or the source or emitter of switch tube S1 is connected to the source or emitter of switch tube S1, so that the switch tube bridge arm can be completely turned off. In the following embodiments of the present application, the switch tube S1 and the switch tube S2 both include IGBTa and diode Dm as an example for exemplary description.

[0104] In the positive half cycle when the inductor La receives the alternating current, when the switch bridge arm is turned on, the inductor La is charged, and when the switch bridge arm is turned off, the inductor La is discharged, and the diode Da is used for rectification. In the negative half cycle when the inductor La receives the alternating current, when the switch bridge arm is turned on, the inductor La is charged, and when the switch bridge arm is turned off, the inductor La is discharged, and the diode Db is used for rectification. Thus, the rectifier circuit (for example, the first rectifier circuit 340) can rectify and boost the received alternating current, and output it to the positive DC bus +BUS and the negative DC bus -BUS.

[0105] In a possible embodiment, the first rectifier circuit 340 may also be called a power factor correction (PFC) circuit.

[0106] In a possible embodiment, Figure 4 (a) or Figure 6 The power conversion device 300 shown in (a) may also be referred to as a frequency converter.

[0107] In a possible embodiment, Figure 4 (a) Figure 6 (a) Fig.10 (a) or Fig.11 As shown in (a), the power conversion device 300 also includes positive and negative bus capacitors arranged between the positive DC bus +BUS and the negative DC bus -BUS, and the positive and negative bus capacitors include a first capacitor C1 and a second capacitor C2 connected in series, and the connection point of the positive and negative bus capacitors is connected to the neutral line.

[0108] In one possible embodiment, referring to Figure 4 (a) Figure 6 (a) Fig.10 (a) or Fig.11 In (a), when the inverter circuit (e.g., the first inverter circuit 310) in the power conversion device 300 obtains energy from the positive DC bus +BUS but not from the negative DC bus -BUS, the voltage of the positive DC bus +BUS will be less than the voltage of the negative DC bus -BUS, resulting in an imbalance between the voltage of the positive DC bus +BUS and the voltage of the negative DC bus -BUS. Alternatively, when the inverter circuit in the power conversion device 300 obtains energy from the negative DC bus -BUS but not from the positive DC bus +BUS, the voltage of the positive DC bus +BUS will be greater than the voltage of the negative DC bus -BUS, resulting in an imbalance between the voltage of the positive DC bus +BUS and the voltage of the negative DC bus -BUS. The imbalance between the voltage of the positive DC bus +BUS and the voltage of the negative DC bus -BUS will result in poor power quality and low reliability of the power conversion device 300.

[0109] In order to avoid the voltage imbalance between the positive DC bus + BUS and the negative DC bus - BUS, Figure 4 (a) Figure 6 (a) Fig.10 (a) or Fig.11As shown in (a), the power conversion device 300 also includes an inductor Lb, a switch tube S3 and a switch tube S4. In the following embodiments of the present application, the switch tube S3 and the switch tube S4 both include IGBTb and a diode Dn as an example for illustrative description. The collector of IGBTb in the switch tube S3 is connected to the positive DC bus +BUS, the emitter of IGBTb in the switch tube S3 and the collector of IGBTb in the switch tube S4 are connected to one end of the inductor Lb, the other end of the inductor Lb is connected to the connection point of the positive and negative bus capacitors, and the emitter of IGBTb in the switch tube S4 is connected to the negative DC bus -BUS.

[0110] by Figure 4 Taking the power conversion device 300 shown in (a) as an example, if the voltage of the positive DC bus +BUS is less than the voltage of the negative DC bus -BUS, the switch tube S3 is always in the off state. When the switch tube S4 is turned on, the negative DC bus -BUS charges the inductor Lb through the switch tube S4. When the switch tube S4 is turned off, the inductor Lb discharges and continues to flow through the diode Dn in the switch tube S3. The inductor Lb supplies power to the positive DC bus +BUS, thereby transferring the energy of the negative DC bus -BUS to the positive DC bus +BUS, achieving a balance between the voltage of the positive DC bus +BUS and the voltage of the negative DC bus -BUS, and balancing the voltages of the positive and negative bus capacitors, so as to improve the reliability of the power conversion device 300.

[0111] Continue with Figure 4 Taking the power conversion device 300 shown in (a) as an example, if the voltage of the positive DC bus +BUS is greater than the voltage of the negative DC bus -BUS, the switch tube S4 is always in the off state. When the switch tube S3 is turned on, the positive DC bus +BUS charges the inductor Lb through the switch tube S3. When the switch tube S3 is turned off, the inductor Lb discharges and continues to flow through the diode Dn in the switch tube S4. The inductor Lb supplies power to the negative DC bus -BUS, thereby transferring the energy of the positive DC bus +BUS to the negative DC bus -BUS, achieving a balance between the voltage of the positive DC bus +BUS and the voltage of the negative DC bus -BUS, and balancing the voltages of the positive and negative bus capacitors, so as to improve the reliability of the power conversion device 300.

[0112] The embodiment of the present application also provides an uninterruptible power supply, which includes at least one power conversion device 300, the input end of each power conversion device 300 is connected to the input end of the uninterruptible power supply, the output end of each power conversion device 300 is connected to the output end of the uninterruptible power supply, and the output end of the uninterruptible power supply is used to connect to the load. The circuit topology diagram of the power conversion device 300 is as shown above Figures 3 to 11 A circuit topology diagram of the power conversion device 300 shown in any of the accompanying drawings.

[0113] Optionally, the uninterruptible power supply may be a single-phase uninterruptible power supply, or may be a three-phase uninterruptible power supply, which is not limited in the embodiments of the present application.

[0114] Exemplarily, when the uninterruptible power supply is a single-phase uninterruptible power supply, the circuit topology diagram of the uninterruptible power supply is as follows: Figure 4 (a) or Figure 6 (a) is a schematic diagram of the circuit topology of the uninterruptible power supply 400.

[0115] Exemplarily, when the uninterruptible power supply is a three-phase uninterruptible power supply, the circuit topology diagram of the uninterruptible power supply is as follows: Fig.10 (a) or Fig.11 (a) is a schematic diagram of the circuit topology of the uninterruptible power supply 400.

[0116] like Fig.12 As shown, the embodiment of the present application also provides a photovoltaic inverter 500, the photovoltaic inverter 500 includes a direct current direct current (DCDC) conversion circuit 510, and a power conversion device 300 connected to the DCDC conversion circuit, the circuit topology diagram of the power conversion device 300 is as shown above Figures 3 to 11 A circuit topology diagram of a power conversion device 300 is shown in any of the accompanying drawings. The power conversion device 300 is used to convert the direct current output by the DCDC conversion circuit 510 into alternating current.

[0117] The above detailed description of the power conversion device 300 and the analysis of the beneficial effects can be correspondingly referred to the uninterruptible power supply 400 and the photovoltaic inverter 500, and the embodiments of the present application will not be repeated here.

[0118] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A power conversion device, characterized in that: The power conversion device comprises at least one inverter circuit, wherein the inverter circuit comprises a switch tube bridge arm, a first switch tube and an inductor; The switch tube bridge arm includes at least three switch tubes connected in series between a positive DC bus and a negative DC bus; The first switch tube is connected between a first node of the switch tube bridge arm and a connection point of positive and negative bus capacitors, the inductor is connected to a second node of the switch tube bridge arm, and the first node and the second node are located at different positions in the switch tube bridge arm.

2. The power conversion device according to claim 1, characterized in that: The switch tube bridge arm comprises a second switch tube, a third switch tube and a fourth switch tube connected in series, the series connection point of the second switch tube and the third switch tube is the first node, and the series connection point of the third switch tube and the fourth switch tube is the second node; The withstand voltage of the fourth switch tube is greater than or equal to the bus voltage, and the withstand voltage of each switch tube except the fourth switch tube is greater than or equal to half of the bus voltage.

3. The power conversion device according to claim 2, characterized in that: The second switch tube is used to connect the positive DC bus, the fourth switch tube is used to connect the negative DC bus, and the drain or collector of the first switch tube is connected to the drain or collector of the third switch tube; When the third switch tube is turned on, and the second switch tube and the first switch tube are turned on alternately, the voltage of the alternating current output by the inductor is greater than zero; When the third switch tube and the first switch tube are turned on or off at the same time, and are turned on alternately with the fourth switch tube, the voltage of the alternating current output by the inductor is less than zero.

4. The power conversion device according to claim 3, characterized in that: The third switch tube includes a first transistor and a first diode connected in reverse parallel to the first transistor, the first switch tube includes a second transistor and a second diode connected in reverse parallel to the second transistor, and the cathode of the first diode is connected to the cathode of the second diode; When the voltage of the alternating current output by the inductor is greater than zero, the second transistor is in an off state; When the voltage of the alternating current output by the inductor is less than zero, the first transistor is in a disconnected state.

5. The power conversion device according to claim 2, characterized in that: The second switch tube is used to connect the negative DC bus, the fourth switch tube is used to connect the positive DC bus, the drain or collector of the first switch tube is connected to the drain or collector of the third switch tube, or the source or emitter of the first switch tube is connected to the source or emitter of the third switch tube; When the third switch tube and the first switch tube are turned on or off at the same time, and are turned on alternately with the fourth switch tube, the voltage of the AC power output by the inductor is greater than zero; When the third switch tube is turned on, and the second switch tube and the first switch tube are turned on alternately, the voltage of the alternating current output by the inductor is less than zero.

6. The power conversion device according to claim 5, characterized in that: The drain or collector of the first switch tube is connected to the drain or collector of the third switch tube, the third switch tube includes a first transistor and a first diode connected in reverse parallel to the first transistor, the first switch tube includes a second transistor and a second diode connected in reverse parallel to the second transistor, and the cathode of the first diode is connected to the cathode of the second diode; When the voltage of the alternating current output by the inductor is greater than zero, the second transistor is in an off state; When the voltage of the alternating current output by the inductor is less than zero, the first transistor is in a disconnected state.

7. The power conversion device according to claim 5, characterized in that: The source or emitter of the first switch tube is connected to the source or emitter of the third switch tube, the third switch tube includes a first transistor and a first diode connected in reverse parallel to the first transistor, the first switch tube includes a second transistor and a second diode connected in reverse parallel to the second transistor, and the anode of the first diode is connected to the anode of the second diode; When the voltage of the alternating current output by the inductor is greater than zero, the first transistor is in a disconnected state; When the voltage of the alternating current output by the inductor is less than zero, the second transistor is in a disconnected state.

8. The power conversion device according to any one of claims 2 to 7, characterized in that: Each of the inverter circuits further includes a capacitor, one end of which is connected to the AC power output end of the inductor, and the other end of which is used to be connected to the neutral line.

9. The power conversion device according to any one of claims 2 to 8, characterized in that: Each of the inverter circuits further includes a heat-conducting component. The fourth switch tube, the third switch tube, the second switch tube and the first switch tube are sequentially away from the air inlet and in contact with the heat-conducting component.

10. The power conversion device according to any one of claims 2 to 9, characterized in that: The power conversion device comprises a plurality of inverter circuits, and the AC power output ends of the inductors in the plurality of inverter circuits are connected.

11. The power conversion device according to any one of claims 2 to 10, characterized in that: The power conversion device comprises three inverter circuits, and the AC power output ends of the inductors in the three inverter circuits are respectively used to output one-phase AC power.

12. The power conversion device according to any one of claims 1 to 11, characterized in that: The power conversion device further comprises a rectifier circuit, wherein an input end of the rectifier circuit is connected to an input end of the power conversion device, a positive output end of the rectifier circuit is connected to the positive DC bus, and a negative output end of the rectifier circuit is connected to the negative DC bus; The rectifier circuit is used to convert the alternating current input from the input end of the power conversion device into direct current, and output the direct current to the inverter circuit. The inverter circuit is used to convert the direct current into alternating current and output it to the output end of the power conversion device.

13. An uninterruptible power supply, characterized in that: The uninterruptible power supply includes at least one power conversion device, the input end of each power conversion device is connected to the input end of the uninterruptible power supply, the output end of each power conversion device is connected to the output end of the uninterruptible power supply, the output end of the uninterruptible power supply is used to connect to a load, and the power conversion device is a power conversion device as described in any one of claims 1-12.

14. A photovoltaic inverter, characterized in that: The photovoltaic inverter comprises a DCDC conversion circuit and a power conversion device as described in any one of claims 1 to 12, wherein the power conversion device is used to convert direct current output by the DCDC conversion circuit into alternating current.

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