Power conversion apparatus, uninterruptible power supply, and photovoltaic inverter

Abstract

The embodiments of the present application relate to the technical field of power electronics. Disclosed are a power conversion apparatus, an uninterruptible power supply and a photovoltaic inverter, which solve the problems of low efficiency and high device costs of existing inverters. The specific solution comprises: providing a power conversion apparatus, the power conversion apparatus comprising at least one inverter circuit, which inverter circuit comprises a switch tube bridge arm, a first switch tube and an inductor, wherein the switch tube bridge arm comprises at least three switch tubes connected in series between a positive direct-current bus and a negative direct-current 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.

Description

A power conversion device, an uninterruptible power supply, and a photovoltaic inverter

[0001] This application claims priority to Chinese patent application No. 202410686012.8, filed with the State Intellectual Property Office of China on May 29, 2024, entitled "A Power Conversion Device, Uninterruptible Power Supply and Photovoltaic Inverter", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of power electronics technology, and more particularly to a power conversion device, an uninterruptible power supply, and a photovoltaic inverter. Background Technology

[0003] An inverter (INV) is used to convert direct current (DC) to alternating current (AC). Types of inverters include I-type and T-type inverters. Currently, I-type and T-type inverters are widely used in various devices and systems, such as frequency converters and uninterruptible power supplies (UPS).

[0004] However, the efficiency of inverters is currently low and the cost of components is high. How to improve the efficiency of inverters and reduce the cost of their components has become an urgent problem to be solved. Summary of the Invention

[0005] This application provides a power conversion device, an uninterruptible power supply, and a photovoltaic inverter, which solves the problems of low efficiency and high device cost of current inverters.

[0006] To achieve the above objectives, the embodiments of this application adopt the following technical solutions:

[0007] A first aspect of this application provides a power conversion device, which includes at least one inverter circuit. The inverter circuit includes a switching bridge arm, a first switching transistor, and an inductor. The switching bridge arm includes at least three switching transistors connected in series between a positive DC bus and a negative DC bus. The first switching transistor is connected between a first node of the switching bridge arm and the connection point of the positive and negative bus capacitors. The inductor is connected to a second node of the switching bridge arm. The first node and the second node are located at different positions in the switching bridge arm.

[0008] Based on this scheme, the inverter circuit includes at least four switching transistors. Compared with the existing I-type inverter which uses four switching transistors and two diodes, this inverter circuit uses fewer components, which can reduce board area, cost, and losses, and improve efficiency. Meanwhile, the first switching transistor is connected between the first node of the switching transistor 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 switching transistor bridge arm. The first and second nodes are located at different positions within the switching transistor bridge arm. The other end of the inductor is the AC output terminal. Compared with the existing I-type and T-type inverters, the switching transistor bridge arm has an asymmetrical structure relative to the inductor. Therefore, the voltage ratings of the switching transistors in the switching transistor bridge arm can be different, allowing the use of switching transistors with lower voltage ratings. This results in lower component costs, lower switching losses, and higher efficiency in the inverter circuit.

[0009] In conjunction with the first aspect, in one possible implementation, the switch bridge arm includes a second switch, a third switch, and a fourth switch connected in series. The series connection point of the second and third switches is the first node, and the series connection point of the third and fourth switches is the second node. The withstand voltage of the fourth switch is greater than or equal to the bus voltage, and the withstand voltage of each switch except the fourth switch is greater than or equal to half of the bus voltage.

[0010] Based on this scheme, the switching bridge arm includes a second, third, and fourth switching transistor connected in series. The series connection point of the second and third switching transistors is the first node, and the series connection point of the third and fourth switching transistors is the second node. The fourth switching transistor is connected between the inductor and the positive DC bus, and the second and third switching transistors are connected between the inductor and the negative DC bus; alternatively, the second and third switching transistors are connected between the inductor and the positive DC bus, and the fourth switching transistor is connected between the inductor and the negative DC bus. Therefore, the withstand voltage of the fourth switching transistor Q4 needs to be greater than or equal to the bus voltage, and the withstand voltage of each switching transistor other than Q4 needs to be greater than or equal to half of the bus voltage. Compared to a T-type inverter where both switching transistors between the positive and negative DC buses must have high withstand voltages, in this power conversion device's inverter circuit, the withstand voltage of the fourth switching transistor is greater than or equal to the bus voltage, while the withstand voltages of the remaining switching transistors are greater than or equal to half of the bus voltage. This results in lower component costs, lower switching losses, and higher efficiency in the inverter circuit.

[0011] In conjunction with the first aspect, in one possible implementation, the second switch is connected to the positive DC bus, the fourth switch is connected to the negative DC bus, and the drain or collector of the first switch is connected to the drain or collector of the third switch. When the third switch is on, and the second and first switches are alternately on, the voltage of the AC output from the inductor is greater than zero. When the third and first switches are simultaneously on or off, and alternately on with the fourth switch, the voltage of the AC output from the inductor is less than zero.

[0012] Based on this scheme, in each inverter circuit, when the third switch is turned on and the second and first switches are turned on alternately, the voltage of the AC output from the inductor is greater than zero. When the third and first switches are turned on or off simultaneously and are turned on alternately with the fourth switch, the voltage of the AC output from the inductor is less than zero. Thus, each inverter circuit can convert DC power into AC power.

[0013] In conjunction with the first aspect, in one possible implementation, the third switch includes a first transistor and a first diode connected in anti-parallel to the first transistor. The first switch includes a second transistor and a second diode connected in anti-parallel to the second transistor, with the cathode of the first diode connected to the cathode of the second diode. When the voltage of the AC output current from the inductor is greater than zero, the second transistor is in the off state; when the voltage of the AC output current from the inductor is less than zero, the first transistor is in the off state.

[0014] Based on this scheme, when the voltage of the AC output from the inductor is greater than zero, the second transistor is in the off state, and when the voltage of the AC output from the inductor is less than zero, the first transistor is in the off state. This reduces the switching losses of the first and third switching transistors, thereby reducing the losses of each inverter circuit and thus reducing the losses of the power conversion device.

[0015] In conjunction with the first aspect, in one possible implementation, the second switch is connected to the negative DC bus, and the fourth switch is connected to the positive DC bus. The drain or collector of the first switch is connected to the drain or collector of the third switch, or the source or emitter of the first switch is connected to the source or emitter of the third switch. When the third switch and the first switch are simultaneously turned on or off, and alternately turned on with the fourth switch, the voltage of the AC output current from the inductor is greater than zero. When the third switch is turned on, and the second switch and the first switch are alternately turned on, the voltage of the AC output current from the inductor is less than zero.

[0016] Based on this scheme, when the third switch and the first switch are simultaneously turned on or off, and alternately turned on with the fourth switch, the voltage of the AC output from the inductor is greater than zero. When the third switch is turned on, and the second switch and the first switch are alternately turned on, the voltage of the AC output from the inductor is less than zero. Thus, each inverter circuit can convert DC power into AC power.

[0017] In conjunction with the first aspect, in one possible implementation, the drain or collector of the first switching transistor and the drain or collector of the third switching transistor are connected. The third switching transistor includes a first transistor and a first diode connected in anti-parallel to the first transistor. The first switching transistor includes a second transistor and a second diode connected in anti-parallel to the second transistor, with the cathode of the first diode connected to the cathode of the second diode. When the voltage of the AC output current from the inductor is greater than zero, the second transistor is in the off state; when the voltage of the AC output current from the inductor is less than zero, the first transistor is in the off state.

[0018] Based on this scheme, when the voltage of the AC output from the inductor is greater than zero, the second transistor is in the off state, and when the voltage of the AC output from the inductor is less than zero, the first transistor is in the off state. This reduces the switching losses of the first and third switching transistors, thereby reducing the losses of each inverter circuit and thus reducing the losses of the power conversion device.

[0019] In conjunction with the first aspect, in one possible implementation, the source or emitter of the first switching transistor and the source or emitter of the third switching transistor are connected. The third switching transistor includes a first transistor and a first diode connected in anti-parallel to the first transistor. The first switching transistor includes a second transistor and a second diode connected in anti-parallel to the second transistor, with the anode of the first diode connected to the anode of the second diode. When the voltage of the AC output current from the inductor is greater than zero, the first transistor is in the off state; when the voltage of the AC output current from the inductor is less than zero, the second transistor is in the off state.

[0020] Based on this scheme, when the voltage of the AC output from the inductor is greater than zero, the first transistor is in the off state, and when the voltage of the AC output from the inductor is less than zero, the second transistor is in the off state. This reduces the switching losses of the first and third switching transistors, thereby reducing the losses of each inverter circuit and thus reducing the losses of the power conversion device.

[0021] In conjunction with the first aspect, in one possible implementation, each inverter circuit also includes a capacitor, one end of which is connected to the AC output terminal of the inductor, and the other end of which is used to connect to the neutral wire.

[0022] Based on this scheme, in each inverter circuit, the AC output from the inductor is filtered by a capacitor, thereby reducing harmonics and noise in the AC, reducing ineffective losses, improving the quality of the AC output from the inverter circuit, and improving the efficiency of the inverter circuit. Therefore, the power conversion device provided in this application embodiment has lower losses and higher efficiency.

[0023] In conjunction with the first aspect, in one possible implementation, each inverter circuit further includes a heat-conducting component, with the fourth, third, second, and first switching transistors sequentially located away from the air inlet and in contact with the heat-conducting component.

[0024] Optionally, the types of heat-conducting components mentioned above include heat pipes, heat sinks, and metal radiators. This application does not limit the specific type of heat-conducting component.

[0025] Based on this scheme, each inverter circuit also includes a heat-conducting component. The fourth, third, second, and first switching transistors are sequentially moved away from the air inlet and come into contact with the heat-conducting component, which can effectively reduce the temperature of each switching transistor. At the same time, it is not necessary for each switching transistor to correspond to a separate air inlet, which can reduce the volume of the heat-conducting component and improve the power density of the inverter circuit. This can reduce the volume of the power conversion device and improve the power density of the power conversion device.

[0026] In conjunction with the first aspect, in one possible implementation, the power conversion device includes multiple inverter circuits, with the AC output terminals of the inductors in the multiple inverter circuits connected.

[0027] Based on this scheme, the power conversion device includes multiple inverter circuits, in which the AC output terminals of the inductors are connected, thereby increasing the output power of the inverter.

[0028] In conjunction with the first aspect, in one possible implementation, the power conversion device includes three inverter circuits, each of which has an AC output terminal of an inductor for outputting a single phase of AC power.

[0029] Based on this scheme, the power conversion device includes three inverter circuits. The AC output terminals of the inductors in the three inverter circuits are used to output one phase of 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.

[0030] In conjunction with the first aspect, in one possible implementation, the power conversion device further includes a rectifier circuit. The input terminal of the rectifier circuit is connected to the input terminal of the power conversion device, the positive output terminal of the rectifier circuit is connected to the positive DC bus, and the negative output terminal 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 terminal 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 back into alternating current and output it to the output terminal of the power conversion device.

[0031] A second aspect of this application provides an uninterruptible power supply (UPS) including at least one power conversion device. The input terminal of each power conversion device is connected to the input terminal of the UPS, and the output terminal of each power conversion device is connected to the output terminal of the UPS. The output terminal of the UPS is used to connect a load. The power conversion device is the power conversion device described in the first aspect or any possible implementation thereof.

[0032] Optionally, the uninterruptible power supply can be a single-phase uninterruptible power supply or a three-phase uninterruptible power supply; the embodiments of this application do not limit this.

[0033] A third aspect of this application provides a photovoltaic inverter, which includes a DC-DC converter circuit and a power conversion device. The power conversion device is used to convert the DC power output by the DC-DC converter circuit into AC power. The power conversion device is the power conversion device described in the first aspect or any possible implementation of the first aspect.

[0034] The descriptions of the second and third aspects in this application can be referenced to the detailed description of the first aspect; and the beneficial effects of the second and third aspects can be referenced to the analysis of the beneficial effects of the first aspect, which will not be repeated here. Attached Figure Description

[0035] Figure 1 is a schematic diagram of the circuit topology of an I-shaped inverter;

[0036] Figure 2 is a schematic diagram of the circuit topology of a T-type inverter;

[0037] Figure 3 is a schematic diagram of the circuit topology of an inverter provided in an embodiment of this application;

[0038] Figure 4 is a schematic diagram of the circuit topology of an inverter provided in an embodiment of this application;

[0039] Figure 5 is a schematic diagram of the circuit topology of an inverter provided in an embodiment of this application;

[0040] Figure 6 is a schematic diagram of the circuit topology of an inverter provided in an embodiment of this application;

[0041] Figure 7 is a schematic diagram of the circuit topology of an inverter provided in an embodiment of this application;

[0042] Figure 8 is a schematic diagram of the circuit topology of an inverter provided in an embodiment of this application;

[0043] Figure 9 is a schematic diagram of the circuit topology of an inverter provided in an embodiment of this application;

[0044] Figure 10 is a schematic diagram of the circuit topology of an inverter provided in an embodiment of this application;

[0045] Figure 11 is a schematic diagram of the circuit topology of an inverter provided in an embodiment of this application;

[0046] Figure 12 is a schematic diagram of the circuit topology of a photovoltaic inverter provided in an embodiment of this application. Detailed Implementation

[0047] The following sections will discuss the fabrication and use of various embodiments in detail. However, it should be understood that many applicable inventive concepts provided in this application can be implemented in a variety of specific environments. The specific embodiments discussed are merely illustrative of specific ways of implementing and using this description and technology, and do not limit the scope of this application.

[0048] Unless otherwise defined, all technical terms used herein have the same meaning as commonly known to one of ordinary skill in the art.

[0049] Each circuit or other component may be described or referred to as "for" performing one or more tasks. In this context, "for" is used to imply a structure by indicating that the circuit / component includes a structure (e.g., a circuit system) that performs one or more tasks during operation. Therefore, even when the specified circuit / component is currently inoperable (e.g., not turned on), it can still be referred to as "for performing that task." Circuits / components used with the term "for" include hardware, such as circuits that perform operations.

[0050] The technical solutions in the embodiments of this application will be described below with reference to the accompanying drawings. In this application, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, or B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the related objects before and after are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can mean: 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 embodiments of this application, the words "first," "second," etc., do not limit the quantity or order.

[0051] In this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or illustration. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0052] Before introducing the embodiments of this application, the technical terms and background technology involved in this application will be introduced first.

[0053] Alternating conduction: This refers to the conduction states of two or more switching transistors being opposite to each other. For example, taking two switching transistors alternating conduction as an example, when one switching transistor is on, the other switching transistor is in the off state.

[0054] Heat dissipation gradient distribution: refers to the continuous or discontinuous temperature change sequence formed by temperature variation with position inside or on the surface of an object.

[0055] Figure 1(a) shows a circuit topology diagram of an I-shaped inverter 100. The two input terminals of the I-shaped inverter 100 are used to connect to the positive DC bus +BUS and the negative DC bus -BUS, respectively. Positive and negative bus capacitors are connected between the positive DC bus +BUS and the negative DC bus -BUS. 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 wire (N).

[0056] As shown in Figure 1(a), the I-shaped inverter 100 includes an inductor L, an upper bridge arm disposed between the positive DC bus +BUS and the first end of the inductor L, and a lower bridge arm disposed between the negative DC bus -BUS and the first end of the inductor L. The upper bridge arm includes a first switch Q1 and a second switch Q2 connected in series, and the lower bridge arm includes a third switch Q3 and a fourth switch Q4 connected in series. Taking the first switch Q1 as an example, each switch includes an insulated-gate bipolar transistor (IGBT) and a first diode D1. The collector of the IGBT is connected to the negative terminal of the first diode D1, and the emitter of the IGBT is connected to the positive terminal of the first diode D1. The I-shaped inverter also includes a second diode D2 and a third diode D3. The negative terminal of the second diode D2 is connected to the midpoint of the upper bridge arm, and the positive terminal of the third diode D3 is connected to the midpoint of the lower bridge arm. The positive terminals of the second diode D2 and the negative terminals of the third diode D3 are connected to the neutral wire. The second end of the inductor L in the I-shaped inverter 100 is used to output AC power. 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 AC power output from the second end of the inductor L.

[0057] Figure 1(b) shows a schematic diagram of the switching transistors in the I-shaped inverter 100. Combining Figure 1(a) and Figure 1(b), when the second switch Q2 is turned on and the first switch Q1 and the third switch Q3 are turned on alternately, the AC voltage output from the second terminal of the inductor L will be greater than or equal to zero. When the third switch Q3 is turned on and the second switch Q2 and the fourth switch Q4 are turned on alternately, the AC voltage output from the second terminal of the inductor L will be less than or equal to zero. Thus, the I-shaped inverter 100 can convert DC power into AC power.

[0058] Figure 2(a) shows a circuit topology diagram of a T-type inverter 200. The two input terminals of the T-type inverter 200 are used to connect the positive DC bus +BUS and the negative DC bus -BUS, respectively. Positive and negative bus capacitors are connected between the positive DC bus +BUS and the negative DC bus -BUS. 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.

[0059] As shown in Figure 2(a), the T-shaped inverter 200 includes an inductor L, a first switch Q1 disposed between the positive DC bus +BUS and the first end of the inductor L, a second switch Q2 disposed between the negative DC bus -BUS and the first end of the inductor L, and a switch bridge arm disposed between the connection point of the positive and negative bus capacitors and the first end of the inductor L. This switch bridge arm includes a third switch Q3 and a fourth switch Q4 connected in series. The drain or collector of the third switch Q3 is connected to the drain or collector of the fourth switch Q4, thus allowing the switch bridge arm to be completely turned off. Taking the first switch Q1 as an example, each switch includes an IGBT and a diode D. The collector of the IGBT is connected to the cathode of the diode D, and the emitter of the IGBT is connected to the anode of the diode D. The cathode of the diode D in the third switch Q3 is connected to the cathode of the diode D in the fourth switch, thus allowing the switch bridge arm to be completely turned off. The second end of the inductor L in the T-type inverter 200 is used to output AC power. The T-type 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 AC power output from the second end of the inductor L.

[0060] Figure 2(b) shows a schematic diagram of the switching transistors in the T-type inverter 200. Combining Figure 2(a) and Figure 2(b), when the fourth switch Q4 is turned on and the first switch Q1 and the third switch Q3 are turned on alternately, the AC voltage output from the second terminal of the inductor L will be greater than zero. When the third switch Q3 is turned on and the second switch Q2 and the fourth switch Q4 are turned on alternately, the AC voltage output from the second terminal of the inductor L will be less than zero. Thus, the T-type inverter 200 can convert DC power into AC power.

[0061] Compared to the T-type inverter 200, which uses 4 switching transistors, the I-type inverter 100 requires 4 switching transistors and 2 diodes. The I-type inverter 100 uses more components, which will result in a larger board area, higher cost, higher losses, and lower efficiency. Although the T-type inverter 200 uses four switching transistors and occupies a small board area, the withstand voltage values ​​of the first switching transistor Q1 and the second switching transistor Q2 in the T-type inverter 200 must both be greater than or equal to the bus voltage. This bus voltage is the voltage difference between the positive DC bus +BUS and the negative DC bus -BUS. Both the first switching transistor Q1 and the second switching transistor Q2 need to be switching transistors with high withstand voltage values. For example, taking the bus voltage as 800V as an example, both the first switching transistor Q1 and the second switching transistor Q2 need to be switching transistors with a withstand voltage value of 1200V. The higher the withstand voltage value of the switching transistor, the higher the price of the switching transistor and the higher the switching loss, which will result in higher cost and loss and lower efficiency of the T-type inverter 200.

[0062] In summary, both the I-shaped inverter 100 and the T-shaped inverter 200 suffer from high losses, low efficiency, and high costs. Therefore, this application provides a power conversion device in which each inverter circuit employs at least four switching transistors, thereby reducing board area, lowering costs, reducing losses, and improving efficiency.

[0063] Figure 3(a) shows a circuit topology diagram of a power conversion device 300 provided in an embodiment of this application. The power conversion device 300 includes at least one inverter circuit. This embodiment of the application does not limit the specific number of inverter circuits included in the power conversion device 300. Figure 3(a) illustrates the example of the power conversion device 300 including a first inverter circuit 310.

[0064] Referring to Figure 3(a), the first inverter circuit 310 includes a switching bridge arm 311, a first switching transistor Q1, and an inductor L. The switching bridge arm 311 includes at least three switching transistors connected in series between the positive DC bus +BUS and the negative DC bus -BUS. In this embodiment, the specific number of switching transistors included in the switching bridge arm 311 is not limited. In the following embodiments of this application, the switching bridge arm 311 includes a second switching transistor Q2, a third switching transistor Q3, and a fourth switching transistor Q4 connected in series as an example for illustrative purposes.

[0065] Referring to Figure 3(a), positive and negative bus capacitors are connected between the positive DC bus +BUS and the negative DC bus -BUS. These positive and negative bus capacitors include a first capacitor C1 and a second capacitor C2 connected in series. The connection point of these positive and negative bus capacitors is connected to the neutral line. In the switching transistor bridge arm 311, the series connection point of the second switch Q2 and the third switch Q3 is the first node A of the switching transistor bridge arm 311, and the series connection point of the third switch Q3 and the fourth switch Q4 is the second node B of the switching transistor bridge arm 311. The positions of the first node A and the second node B in the switching transistor bridge arm 311 are different. The first switch Q1 is connected between the first node A of the switching transistor 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 switching transistor bridge arm 311. Compared to the I-shaped inverter 100 mentioned above, which uses 4 switching transistors and 2 diodes, the first inverter circuit 310 includes 4 switching transistors, using fewer components, which can reduce board area, reduce cost, reduce losses and improve efficiency.

[0066] Optionally, the second switch Q2 can be used to connect to the positive DC bus +BUS, and the fourth switch Q4 can be used to connect to the negative DC bus -BUS. Alternatively, the second switch Q2 can be used to connect to the negative DC bus -BUS, and the fourth switch Q4 can be used to connect to the positive DC bus +BUS. This application does not limit the specifics of this embodiment. Figure 3(a) illustrates this example with the second switch Q2 connected to the positive DC bus +BUS and the fourth switch Q4 connected to the negative DC bus -BUS.

[0067] Among them, the withstand voltage of the fourth switch Q4 is greater than or equal to the bus voltage, and the withstand voltage of each switch except the fourth switch Q4 is greater than or equal to half of the bus voltage. The bus voltage is the voltage difference between the positive DC bus +BUS and the negative DC bus -BUS.

[0068] Referring to Figure 3(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 terminal of the first inverter circuit 310, the switching transistors between the second node B and the connection points of the positive DC bus +BUS, the negative DC bus -BUS, or the positive and negative bus capacitors need 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 a second switching transistor Q2 and a third switching transistor Q3 connected in series; the connection points of the positive and negative bus capacitors and the second node B include a first switching transistor Q1 and a third switching transistor Q3 connected in series; and the negative DC bus -BUS and the second node B include a fourth switching transistor Q4. Therefore, the withstand voltage of the fourth switching transistor Q4 needs to be greater than or equal to the bus voltage, and the withstand voltage of each switching transistor other than the fourth switching transistor Q4 needs to be greater than or equal to half of the bus voltage. Compared to the T-type inverter 200 mentioned above, where the first switch Q1 and the second switch Q2 both require high voltage ratings, the fourth switch Q4 in this first inverter circuit 310 has a voltage rating greater than or equal to the bus voltage, while the voltage ratings of the remaining switches are greater than or equal to half the bus voltage. This first inverter circuit 310 has lower component costs, lower switching losses, and higher efficiency.

[0069] For example, taking a bus voltage of 800V as an example, the withstand voltage of the fourth switch Q4 can be 1200V. In addition to the fourth switch Q4, the withstand voltage of each of the first switch Q1, the second switch Q2 and the third switch Q3 can be 650V.

[0070] In one possible embodiment, the drain or collector of the first switch Q1 is connected to the drain or collector of the third switch Q3, so that the first switch Q1 and the third switch Q3 can completely cut off the path between the inductor L and the neutral line. Figure 3(b) shows a schematic diagram of the waveform curve of the AC output of the inductor L in the power conversion device 300, and Figure 3(c) shows a schematic diagram of the switching transistors in the power conversion device 300 being turned on. Combining Figure 3(a), Figure 3(b) and Figure 3(c), when the third switch Q3 is turned on and the second switch Q2 and the first switch Q1 are turned on alternately, the voltage of the AC output of the inductor L is greater than zero. When the third switch Q3 and the first switch Q1 are turned on or off simultaneously, and are turned on alternately with the fourth switch Q4, the voltage of the AC output of the inductor L is less than zero. Thus, the first inverter circuit 310 can convert DC power into AC power.

[0071] Optionally, each switching transistor may include a transistor or a transistor and a diode. Specifically, each switching transistor may include an IGBT and a diode, with the collector of the IGBT connected to the negative terminal of the diode and the emitter of the IGBT connected to the positive terminal of the diode. Alternatively, each switching transistor may include a metal-oxide-semiconductor field-effect transistor (MOSFET), also simply referred to as a MOS transistor, with each MOS transistor including a reverse-biased body diode. This application does not limit the scope of the embodiments, and the following embodiments of this application use an example of each switching transistor including an IGBT and a diode for illustrative purposes.

[0072] In one possible embodiment, referring to Figure 3(a), taking an example where each switch includes an IGBT and a diode, Figure 4(a) shows another circuit topology schematic diagram of the power conversion device 300. Referring to Figure 4(a), the third switch Q3 includes a first transistor IGBT1 and a first diode D1 connected in antiparallel to the first transistor IGBT1. The first switch Q1 includes a second transistor IGBT2 and a second diode D2 connected in antiparallel to the second transistor IGBT2. The collectors of the first transistor IGBT1 and the second transistor IGBT2 are connected together, and the cathodes of the first diode D1 and the second diode D2 are connected together. The second switch Q2 includes a third transistor IGBT3 and a third diode D3 connected in antiparallel to the third transistor IGBT3. The fourth switch Q4 includes a fourth transistor IGBT4 and a fourth diode D4 connected in antiparallel to the fourth transistor IGBT4.

[0073] Figure 4(b) shows a waveform curve of the AC output from inductor L in the power conversion device 300, and Figure 4(c) shows a conduction diagram of the switching transistor in the power conversion device 300. Combining Figure 4(a) and Figure 4(b), and as shown in Figure 4(c), compared to the conduction diagram of the switching transistor in the power conversion device 300 shown in Figure 3(c) above, when the voltage of the AC output from inductor L is greater than zero, the second transistor IGBT2 in the first switching transistor Q1 is always in the off state, and the second diode D2 is used for freewheeling. When the voltage of the AC output from inductor L is less than zero, the first transistor IGBT1 in the third switching transistor Q3 is always in the off state, and the first diode D1 is used for freewheeling. This reduces the switching losses of the first switching transistor Q1 and the third switching transistor Q3, and reduces the losses of the first inverter circuit 310.

[0074] Specifically, referring to Figures 4(a), 4(b), and 4(c), during the positive half-cycle of the AC output from inductor L: when the third switch Q3 and the second switch Q2 are turned on, the current output from the positive DC bus + BUS charges inductor L sequentially through the second switch Q2 and the third switch Q3, resulting in an AC output voltage greater than zero. When the third switch Q3 is turned on and the second switch Q2 is turned off, inductor L discharges, and current flows from the neutral line sequentially through the second diode D2 in the first switch Q1 and the third switch Q3 to inductor L, resulting in an AC output voltage greater than zero. Understandably, compared with the power conversion device 300 shown in Figure 3(c) above, when the second switch Q2 is turned off and the inductor L is discharged, the second transistor IGBT2 in the first switch Q1 is always in the off state. It can freewheel through the second diode D2 in the first switch Q1. The second transistor IGBT2 in the first switch Q1 is always in the off state. The first switch Q1 does not need to alternate with the second switch Q2, thereby reducing the switching loss of the first switch Q1 and reducing the loss of the first inverter circuit 310.

[0075] Continuing with Figures 4(a), 4(b), and 4(c), during the negative half-cycle of the AC output from inductor L: when the fourth switch Q4 is on, current flows from inductor L through the fourth switch Q4 to the negative DC bus -BUS, charging inductor L, and the voltage of the AC output from inductor L will be less than zero. When the fourth switch Q4 is off and the first switch Q1 is on, inductor L discharges, and current flows from inductor L through the first diode D1 in the third switch Q3 and then through the third switch Q3 to the neutral line, and the voltage of the AC output from inductor L will be less than zero. It can be understood that during the negative half-cycle of the AC output from inductor L, the first switch Q1 and the fourth switch Q4 are alternately on. Compared with the drive signal curve shown in Figure 3(c) above, when the fourth switch Q4 is turned off and the inductor L is discharged, the first transistor IGBT1 in the third switch Q3 is always in the off state. The current can be freed by the first diode D1 in the third switch Q3. Since the first transistor IGBT1 in the third switch Q3 is always in the off state, the third switch Q3 does not need to alternate with the fourth switch Q4, thereby reducing the switching loss of the third switch Q3 and reducing the loss of the first inverter circuit 310.

[0076] In one possible embodiment, Figure 5(a) shows another circuit topology of the power conversion device 300. Referring to Figure 5(a), the second switch Q2 is connected to the negative DC bus -BUS, the fourth switch Q4 is connected to the positive DC bus +BUS, the drain or collector of the first switch Q1 is connected to the drain or collector of the third switch Q3, or the source or emitter of the first switch Q1 is connected to the source or emitter of the third switch Q3. This embodiment does not limit this, so that the first switch Q1 and the third switch Q3 can completely cut off the path between the inductor L and the neutral line. Figure 5(b) shows a waveform curve of the AC output of the inductor L in the power conversion device 300, and Figure 5(c) shows a schematic diagram of the switching transistors in the power conversion device 300 being turned on. Combining Figure 5(a), Figure 5(b), and Figure 5(c), when the third switch Q3 and the first switch Q1 are simultaneously turned on or off, and are alternately turned on with the fourth switch Q4, the voltage of the AC output from the inductor L will be greater than zero. When the third switch Q3 is turned on, and the second switch Q2 and the first switch Q1 are alternately turned on, the voltage of the AC output from the inductor L will be less than zero. Thus, the first inverter circuit 310 can convert DC power into AC power.

[0077] In one possible embodiment, referring to Figure 5(a), taking an example where each switch includes an IGBT and a diode, Figure 6(a) shows another circuit topology schematic diagram of the power conversion device 300. Referring to Figure 6(a), the third switch Q3 includes a first transistor IGBT1 and a first diode D1 connected in anti-parallel to the first transistor IGBT1. The first switch Q1 includes a second transistor IGBT2 and a second diode D2. The collectors of the first transistor IGBT1 and the second transistor IGBT2 are connected together, and the cathodes of the first diode D1 and the second diode D2 are connected together. The second switch Q2 includes a third transistor IGBT3 and a third diode D3 connected in anti-parallel to the third transistor IGBT3. The fourth switch Q4 includes a fourth transistor IGBT4 and a fourth diode D4 connected in anti-parallel to the fourth transistor IGBT4.

[0078] Figure 6(b) shows a waveform curve of the AC output from inductor L in the power conversion device 300, and Figure 6(c) shows a conduction diagram of the switching transistors in the power conversion device 300. Combining Figure 6(a) and Figure 6(b), and as shown in Figure 6(c), compared to the conduction diagram of the switching transistors in the power conversion device 300 shown in Figure 5(c) above, when the voltage of the AC output from inductor L is greater than zero, the second transistor IGBT2 in the first switching transistor Q1 is always in the off state, and the second diode D2 is used for freewheeling. When the voltage of the AC output from inductor L is less than zero, the first transistor IGBT1 in the third switching transistor Q3 is always in the off state, and the first diode D1 is used for freewheeling. This reduces the switching losses of the first switching transistor Q1 and the third switching transistor Q3, and reduces the losses of the first inverter circuit 310.

[0079] Specifically, referring to Figures 6(a), 6(b), and 6(c), during the positive half-cycle of the AC output from inductor L: when the fourth switch Q4 is turned on, the current output from the positive DC bus + BUS charges inductor L through the fourth switch Q4, and the voltage of the AC output from inductor L will be greater than zero. When the fourth switch Q4 is turned off and the third switch Q3 is turned on, inductor L discharges, and the current flows from the zero line through the second diode D2 in the first switch Q1 and the third switch Q3 to inductor L, and the voltage of the AC output from inductor L will be greater than zero. Understandably, compared with the power conversion device 300 shown in Figure 5(c) above, when the fourth switch Q4 is turned off and the inductor L is discharged, the second transistor IGBT2 in the first switch Q1 is always in the off state. It can freewheel through the second diode D2 in the first switch Q1. The first switch Q1 does not need to alternate with the fourth switch Q4, thereby reducing the switching loss of the first switch Q1 and reducing the loss of the first inverter circuit 310.

[0080] Continuing with Figures 6(a), 6(b), and 6(c), during the negative half-cycle of the AC output from inductor L: when the second switch Q2 is on, current flows from inductor L through the first diode D1 in the third switch Q3 and the second switch Q2 to the negative DC bus -BUS, charging inductor L, and the voltage of the AC output from inductor L will be less than zero. When the second switch Q2 is off and the first switch Q1 is on, inductor L discharges, and current flows from inductor L through the first diode D1 in the third switch Q3 and the first switch Q1 to the neutral line, and the voltage of the AC output from inductor L will be less than zero. It can be understood that during the negative half-cycle of the AC output from inductor L, the second switch Q2 and the first switch Q1 are alternately on. Compared with the power conversion device 300 power transistor conduction schematic diagram shown in Figure 5(c) above, when the second switch Q2 and the first switch Q1 are alternately turned on and the inductor L is charging and discharging, the clock of the first transistor IGBT1 in the third switch Q3 is in the off state, and the current can be freed by the first diode D1 in the third switch Q3. The third switch Q3 does not need to be in the on state all the time, thereby reducing the switching loss of the third switch Q3 and reducing the loss of the first inverter circuit 310.

[0081] In one possible embodiment, referring to Figure 5(a), taking an example where each switch includes an IGBT and a diode, Figure 7(a) shows another circuit topology schematic diagram of the power conversion device 300. Referring to Figure 7(a), the third switch Q3 includes a first transistor IGBT1 and a first diode D1 connected in anti-parallel to the first transistor IGBT1. The first switch Q1 includes a second transistor IGBT2 and a second diode D2 connected in anti-parallel to the second transistor IGBT2. The emitter of the first transistor IGBT1 and the emitter of the second transistor IGBT2 are connected together, and the anode of the first diode D1 and the anode of the second diode D2 are connected together. The second switch Q2 includes a third transistor IGBT3 and a third diode D3 connected in anti-parallel to the third transistor IGBT3. The fourth switch Q4 includes a fourth transistor IGBT4 and a fourth diode D4 connected in anti-parallel to the fourth transistor IGBT4.

[0082] Figure 7(b) shows a waveform curve of the AC output from inductor L in the power conversion device 300, and Figure 7(c) shows a conduction diagram of the switching transistor in the power conversion device 300. Combining Figure 7(a) and Figure 7(b), and as shown in Figure 7(c), compared to the conduction diagram of the switching transistor in the power conversion device 300 shown in Figure 5(c) above, when the voltage of the AC output from inductor L is greater than zero, the first transistor IGBT1 in the third switching transistor Q3 is always in the off state, and the first diode D1 is used for freewheeling. When the voltage of the AC output from inductor L is less than zero, the second transistor IGBT2 in the first switching transistor Q1 is always in the off state, and the second diode D2 is used for freewheeling. This reduces the switching losses of the third switching transistor Q3 and the first switching transistor Q1, and reduces the losses of the first inverter circuit 310.

[0083] Specifically, referring to Figures 7(a), 7(b), and 7(c), during the positive half-cycle of the AC output from inductor L: when the fourth switch Q4 is turned on, the current output from the positive DC bus + BUS charges inductor L through the fourth switch Q4, and the voltage of the AC output from inductor L will be greater than zero. When the fourth switch Q4 is turned off and the first switch Q1 is turned on, inductor L discharges, and the current flows from the neutral line through the first diode D1 in the first switch Q1 and the third switch Q3 to inductor L, and the voltage of the AC output from inductor L will be greater than zero. As can be understood, compared with the power conversion device 300 shown in Figure 5(c) above, when the fourth switch Q4 is turned off and the inductor L is discharged, the first transistor IGBT1 in the third switch Q3 is always in the off state, and the current can be freed through the first diode D1 in the third switch Q3. The third switch Q3 does not need to be turned on alternately with the fourth switch Q4, thereby reducing the switching loss of the third switch Q3 and reducing the loss of the first inverter circuit 310.

[0084] Continuing with Figures 7(a), 7(b), and 7(c), during the negative half-cycle of the AC output from inductor L: when the second switch Q2 and the third switch Q3 are on, current flows from inductor L through the third switch Q3 and the second switch Q2 to the negative DC bus -BUS, charging inductor L, and the output AC voltage of inductor L will be less than zero. When the second switch Q2 is off and the third switch Q3 is on, inductor L discharges, and current flows from inductor L through the third switch Q3 and the second diode D2 in the first switch Q1 to the neutral line, and the output AC voltage of inductor L will be less than zero. Understandably, compared with the power conversion device 300 shown in Figure 5(c) above, when the second switch Q2 is turned off and the inductor L is discharged, the second transistor IGBT2 in the first switch Q1 is always in the off state, and the current can be freed through the second diode D2 in the first switch Q1. The first switch Q1 does not need to be turned on alternately with the second switch Q2, thereby reducing the switching loss of the third switch Q3 and reducing the loss of the first inverter circuit 310.

[0085] In one possible embodiment, when the power conversion device 300 is applied to a solar power generation system, the power conversion device 300 may also be referred to as a solar single-phase inverter.

[0086] In the power conversion device 300 provided in this application embodiment, the first inverter circuit 310 uses four switching transistors. Compared with the I-shaped inverter 100 described above, which uses four switching transistors and two diodes, the first inverter circuit 310 uses fewer components, thus reducing board area, cost, losses, and efficiency. Compared with the T-shaped inverter 200 described above, where the first switching transistor Q1 and the second switching transistor Q2 both require high voltage ratings, the fourth switching transistor Q4 in the first inverter circuit 310 has a voltage rating greater than or equal to the bus voltage, while the voltage ratings of the remaining switching transistors are greater than or equal to half the bus voltage. This results in lower component cost, lower switching losses, and higher efficiency in the first inverter circuit 310. Therefore, the power conversion device 300 provided in this application embodiment has a smaller board area, lower cost, lower losses, and higher efficiency.

[0087] In one possible embodiment, taking the circuit topology of the power conversion device 300 as shown in Figure 4(a) as an example, the first inverter circuit 310 further includes a capacitor C. One end of the capacitor C is connected to the AC output terminal of the inductor L, and the other end of the capacitor C is used to connect to the neutral line. The capacitor C is used to filter the AC output of the inductor L, thereby reducing harmonics and noise in the AC, reducing ineffective losses, improving the quality of the AC output of the first inverter circuit 310, and improving the efficiency of the first inverter circuit 310.

[0088] In the power conversion device 300 provided in this application embodiment, the first inverter circuit 310 further includes a capacitor C. The AC power output from the inductor L is filtered by the capacitor C, thereby reducing harmonics and noise in the AC power, reducing ineffective losses, improving the quality of the AC power output from the first inverter circuit 310, and improving the efficiency of the first inverter circuit 310. Therefore, the power conversion device 300 provided in this application embodiment has lower losses and higher efficiency.

[0089] In one possible embodiment, each inverter circuit further includes a heat-conducting component, as shown in FIG8. Taking the first inverter circuit 310 as an example, the first inverter circuit 310 further includes a heat-conducting component 312. The fourth switch Q4, the third switch Q3, the second switch Q2 and the first switch Q1 are sequentially moved away from the air inlet and in contact with the heat-conducting component 312. Since the withstand voltage of the fourth switch Q4 is greater than or equal to the bus voltage, and the withstand voltage of each switch except the fourth switch Q4 is greater than or equal to half of the bus voltage, the fourth switch Q4 has a higher withstand voltage, while the other switches have lower withstand voltages. The fourth switch Q4 has higher switching losses and conduction losses and generates more heat, while the other switches have lower switching losses and conduction losses and generate less heat. Combined with the gradient heat dissipation distribution, the fourth switch Q4 is placed on the heat-conducting component 312 near the air inlet, and the other switches are placed sequentially on the heat-conducting component 312 away from the air inlet. This can effectively reduce the temperature of each switch, and at the same time, it is not necessary for each switch to correspond to an air inlet, which can reduce the volume of the heat-conducting component 312 and help improve the power density of the first inverter circuit 310.

[0090] Optionally, the types of the heat-conducting components 312 mentioned above include heat pipes, heat sinks, and metal heat sinks. This application embodiment does not limit the specific type of the heat-conducting components 312.

[0091] In one possible embodiment, the heat-conducting component 312 and the first to fourth switching transistors Q1 can be inserted onto a printed circuit board (PCB).

[0092] In the power conversion device 300 provided in this application embodiment, the first inverter circuit 310 further includes a heat-conducting component 312. The fourth switch Q4, the third switch Q3, the second switch Q2, and the first switch Q1 are sequentially moved away from the air inlet and disposed on the heat-conducting component 312, thereby effectively reducing the temperature of each switch. At the same time, it is not necessary for each switch to correspond to a separate air inlet, which can reduce the volume of the heat-conducting component 312 and improve the power density of the first inverter circuit 310. This can reduce the volume of the power conversion device 300 and improve the power density of the power conversion device 300.

[0093] In one possible embodiment, the power conversion device 300 includes multiple inverter circuits. Taking the circuit topology of the first inverter circuit 310 shown in Figure 4(a) as an example, as shown in Figure 9, the power conversion device 300 may also include a second inverter circuit 320. The AC output terminal of the inductor L in the first inverter circuit 310 is connected to the AC output terminal of the inductor L in the second inverter circuit 320, thereby improving the output power of the power conversion device 300.

[0094] For example, when the power conversion device 300 is applied to a solar power generation system, the AC output terminal of the inductor L in the first inverter circuit 310 is connected to the AC output terminal 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.

[0095] In one possible embodiment, as shown in FIG9, 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.

[0096] In the power conversion device 300 provided in this application embodiment, the AC output terminal of the inductor L in the first inverter circuit 310 is connected to the AC output terminal of the inductor L in the second inverter circuit 320, thereby improving the output power of the power conversion device 300.

[0097] In one possible embodiment, the power conversion device 300 includes three inverter circuits. Taking the circuit topology of the first inverter circuit 310 shown in Figure 4(a) as an example, as shown in Figure 10(a), the power conversion device 300 also includes a second inverter circuit 320 and a third inverter circuit 330. The AC output terminals of the inductors L in the three inverter circuits are respectively used to output one phase of 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.

[0098] Figure 10(b) shows a schematic diagram of the AC output waveform of inductor L in each inverter circuit. Inductor L in the first inverter circuit 310 is used to output phase A AC, inductor L in the second inverter circuit 320 is used to output phase B AC, and inductor L in the third inverter circuit 330 is used to output phase C AC. The phase difference between the three phases of AC is 120°. Figure 10(c) shows a schematic diagram of the conduction of the switching transistors 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 switching transistors in each inverter circuit can be referred to the relevant description in Figure 4(c) above. The embodiments of this application will not be repeated here.

[0099] In one possible embodiment, taking the circuit topology of the first inverter circuit 310 shown in Figure 6(a) as an example, the circuit topology of the power conversion device 300 can be as shown in Figure 11(a). Figure 11(b) shows a schematic diagram of the 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 phase A AC power, the inductor L in the second inverter circuit 320 is used to output phase B AC power, and the inductor L in the third inverter circuit 330 is used to output phase C AC power. The phase difference between the three phase AC power is 120°. Figure 11(c) shows a schematic diagram of the conduction of the switching transistors 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 switching transistors in each inverter circuit can be referred to the relevant description in Figure 6(b) above, which will not be repeated here in this embodiment.

[0100] The power conversion device 300 provided in this application embodiment includes three inverter circuits. The AC output terminal of the inductor L in the three inverter circuits is used to output one phase of 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.

[0101] In one possible embodiment, as shown in FIG4(a) or FIG6(a), the power conversion device 300 provided in this application embodiment includes a first rectifier circuit 340. The input terminal of the first rectifier circuit 340 is connected to the input terminal of the power conversion device 300, the positive output terminal of the first rectifier circuit 340 is connected to the positive DC bus +BUS, and the negative output terminal 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 terminal of the power conversion device 300 into DC power and output DC power to the first inverter circuit 310. The first inverter circuit 310 is used to convert the DC power back into AC power and output it to the output terminal of the power conversion device 300.

[0102] Optionally, the power conversion device 300 may include one first rectifier circuit 340, or it may include multiple rectifier circuits; this application embodiment does not limit this.

[0103] For example, as shown in Figure 10(a) or Figure 11(a), 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.

[0104] In one possible embodiment, as shown in Figure 4(a), Figure 6(a), Figure 10(a), or Figure 11(a), each rectifier circuit includes an inductor La, a diode bridge arm, and a switching bridge arm. The diode bridge arm includes two diodes Da and Db connected in series, with the positive terminal of diode Da connected to the negative terminal of diode Db. The inductor La is connected between the midpoint of the diode bridge arm and the AC input terminal. The switching bridge arm is connected between the midpoint of the diode bridge arm and the neutral line. The switching bridge arm includes two switching transistors S1 and S2 connected in series. The drain or collector of switching transistor S1 is connected to the drain or collector of switching transistor S2, or the source or emitter of switching transistor S1 is connected to the source or emitter of switching transistor S2, so that the switching bridge arm can be completely turned off. In the following embodiments of this application, switching transistors S1 and S2 both include IGBTa and diode Dm as examples for illustrative purposes.

[0105] During the positive half-cycle of AC power reception in inductor La, inductor La charges when the switching bridge arm is on and discharges when the switching bridge arm is off, with diode Da used for rectification. During the negative half-cycle of AC power reception in inductor La, inductor La charges when the switching bridge arm is on and discharges when the switching bridge arm is off, with diode Db used for rectification. Thus, this rectifier circuit (e.g., the first rectifier circuit 340) can rectify and boost the received AC power and output it to the positive DC bus +BUS and the negative DC bus -BUS.

[0106] In one possible embodiment, the first rectifier circuit 340 may also be referred to as a power factor correction (PFC) circuit.

[0107] In one possible embodiment, the power conversion device 300 shown in FIG4(a) or FIG6(a) may also be referred to as a frequency converter.

[0108] In one possible embodiment, as shown in Figure 4(a), Figure 6(a), Figure 10(a) or Figure 11(a), the power conversion device 300 further includes positive and negative bus capacitors disposed between the positive DC bus +BUS and the negative DC bus -BUS. 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.

[0109] In one possible embodiment, referring to Figures 4(a), 6(a), 10(a), or 11(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 a voltage imbalance between the positive DC bus +BUS and 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 a voltage imbalance between the positive DC bus +BUS and the negative DC bus -BUS. An imbalance between the voltage of the positive DC bus +BUS and the negative DC bus -BUS will result in poor power quality and low reliability of the power conversion device 300.

[0110] To avoid voltage imbalance between the positive DC bus +BUS and the negative DC bus -BUS, as shown in Figure 4(a), Figure 6(a), Figure 10(a), or Figure 11(a), the power conversion device 300 further includes an inductor Lb, a switching transistor S3, and a switching transistor S4. In the following embodiments of this application, the switching transistors S3 and S4 are both IGBTb and diode Dn, which are used as examples for illustrative purposes. The collector of IGBTb in switching transistor S3 is connected to the positive DC bus +BUS. The emitter of IGBTb in switching transistor S3 and the collector of IGBTb in switching transistor 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. The emitter of IGBTb in switching transistor S4 is connected to the negative DC bus -BUS.

[0111] Taking the power conversion device 300 shown in Figure 4(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 S3 is always in the off state. When the switch S4 is turned on, the negative DC bus -BUS charges the inductor Lb through the switch S4. When the switch S4 is turned off, the inductor Lb discharges and freewheels through the diode Dn in the switch 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, realizing the balance between the voltage of the positive DC bus +BUS and the voltage of the negative DC bus -BUS, balancing the voltage of the positive and negative bus capacitors, and improving the reliability of the power conversion device 300.

[0112] Continuing with the example of the power conversion device 300 shown in Figure 4(a), if the voltage of the positive DC bus +BUS is greater than the voltage of the negative DC bus -BUS, the switch S4 is always in the off state. When the switch S3 is turned on, the positive DC bus +BUS charges the inductor Lb through the switch S3. When the switch S3 is turned off, the inductor Lb discharges and freewheels through the diode Dn in the switch 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, balancing the voltage of the positive and negative bus capacitors, and improving the reliability of the power conversion device 300.

[0113] This application embodiment also provides an uninterruptible power supply (UPS), which includes at least one power conversion device 300. The input terminal of each power conversion device 300 is connected to the input terminal of the UPS, and the output terminal of each power conversion device 300 is connected to the output terminal of the UPS. The output terminal of the UPS is used to connect a load. The circuit topology diagram of the power conversion device 300 is as shown in any of the figures 3 to 11 above.

[0114] Optionally, the uninterruptible power supply can be a single-phase uninterruptible power supply or a three-phase uninterruptible power supply; the embodiments of this application do not limit this.

[0115] For example, when the uninterruptible power supply is a single-phase uninterruptible power supply, the circuit topology diagram of the uninterruptible power supply is the circuit topology diagram of uninterruptible power supply 400 shown in Figure 4(a) or Figure 6(a).

[0116] For example, when the uninterruptible power supply is a three-phase uninterruptible power supply, the circuit topology diagram of the uninterruptible power supply is the circuit topology diagram of the uninterruptible power supply 400 shown in Figure 10(a) or Figure 11(a).

[0117] As shown in Figure 12, this application embodiment also provides a photovoltaic inverter 500, which 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 in any of the figures 3 to 11 above. The power conversion device 300 is used to convert the direct current output by the DCDC conversion circuit 510 into alternating current.

[0118] The above detailed description of the power conversion device 300 and the analysis of its beneficial effects can be applied to the uninterruptible power supply 400 and the photovoltaic inverter 500, and will not be repeated here in the embodiments of this application.

[0119] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

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

2. The power conversion device according to claim 1, characterized in that, The switch bridge arm includes a second switch, a third switch, and a fourth switch connected in series. The series connection point of the second switch and the third switch is the first node, and the series connection point of the third switch and the fourth switch is the second node. The withstand voltage of the fourth switching transistor is greater than or equal to the bus voltage, and the withstand voltage of each switching transistor other than the fourth switching transistor 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 is used to connect to the positive DC bus, the fourth switch is used to connect to the negative DC bus, and the drain or collector of the first switch is connected to the drain or collector of the third switch. When the third switch is turned on, and the second and first switches are turned on alternately, the voltage of the AC output from the inductor is greater than zero. When the third switch and the first switch are simultaneously turned on or off, and are alternately turned on with the fourth switch, the voltage of the AC output from the inductor is less than zero.

4. The power conversion device according to claim 3, characterized in that, The third switching transistor includes a first transistor and a first diode connected in reverse parallel with the first transistor. The first switching transistor includes a second transistor and a second diode connected in reverse parallel with the second transistor. The cathode of the first diode is connected to the cathode of the second diode. When the voltage of the AC output from the inductor is greater than zero, the second transistor is in the off state; When the voltage of the AC output from the inductor is less than zero, the first transistor is in the off state.

5. The power conversion device according to claim 2, characterized in that, The second switch is used to connect to the negative DC bus, and the fourth switch is used to connect to the positive DC bus. The drain or collector of the first switch is connected to the drain or collector of the third switch, or the source or emitter of the first switch is connected to the source or emitter of the third switch. When the third switch and the first switch are simultaneously turned on or off, and are alternately turned on with the fourth switch, the voltage of the AC output from the inductor is greater than zero. When the third switch is turned on, and the second and first switches are turned on alternately, the voltage of the AC output from 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 switching transistor is connected to the drain or collector of the third switching transistor. The third switching transistor includes a first transistor and a first diode connected in reverse parallel with the first transistor. The first switching transistor includes a second transistor and a second diode connected in reverse parallel with the second transistor. The cathode of the first diode is connected to the cathode of the second diode. When the voltage of the AC output from the inductor is greater than zero, the second transistor is in the off state; When the voltage of the AC output from the inductor is less than zero, the first transistor is in the off state.

7. The power conversion device according to claim 5, characterized in that, The source or emitter of the first switching transistor is connected to the source or emitter of the third switching transistor. The third switching transistor includes a first transistor and a first diode connected in reverse parallel with the first transistor. The first switching transistor includes a second transistor and a second diode connected in reverse parallel with the second transistor. The anode of the first diode is connected to the anode of the second diode. When the voltage of the AC output from the inductor is greater than zero, the first transistor is in the off state; When the voltage of the AC output from the inductor is less than zero, the second transistor is in the off state.

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

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

10. The power conversion device according to any one of claims 2-9, characterized in that, The power conversion device includes multiple inverter circuits, and the AC output terminals of the inductors in the multiple inverter circuits are connected.

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

12. The power conversion device according to any one of claims 1-11, characterized in that, The power conversion device further includes a rectifier circuit, the input terminal of which is connected to the input terminal of the power conversion device, the positive output terminal of which is connected to the positive DC bus, and the negative output terminal of which is connected to the negative DC bus. The rectifier circuit is used to convert the AC power input from the input terminal of the power conversion device into DC power and output DC power to the inverter circuit. The inverter circuit is used to convert DC power into AC power and output it to the output terminal 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 terminal of each power conversion device is connected to the input terminal of the uninterruptible power supply, the output terminal of each power conversion device is connected to the output terminal of the uninterruptible power supply, the output terminal of the uninterruptible power supply is used to connect a load, and the power conversion device is the power conversion device as described in any one of claims 1-12.

14. A photovoltaic inverter, characterized in that, The photovoltaic inverter includes a DC-DC converter circuit and a power conversion device as described in any one of claims 1-12, wherein the power conversion device is used to convert the DC power output by the DC-DC converter circuit into AC power.

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