Midpoint clamped inverter and photovoltaic power supply system

Abstract

This application provides a midpoint clamped inverter and a photovoltaic power supply system. The midpoint clamped inverter may include a power supply module, a switching module, and a control module. The power supply module may include a power source, and a first capacitor and a second capacitor connected in series and then in parallel across the power source. The switching module may include a first switching unit, a second switching unit, and a third switching unit. The control module may be connected to the first switching unit, the second switching unit, and the third switching unit respectively. The control module may control the on / off state of each switching unit in the first, second, and third switching units to select different switching units in the switching module to bear the conduction loss or the switching loss. Based on this application, different switching units can be flexibly selected to bear the conduction loss or the switching loss, thereby reducing the loss of the midpoint clamped inverter under all operating conditions, resulting in high efficiency and strong applicability.

Description

Technical Field

[0001] This application relates to the field of electronic circuits, and more particularly to a midpoint clamp inverter and a photovoltaic power supply system. Background Technology

[0002] Currently, three-level neutral point clamped (NPC) inverters are widely used in power supply systems that convert DC power to AC power. A typical three-level NPC inverter uses both external and internal switching transistors. Usually, a fixed internal switching transistor bears the losses (such as switching losses or conduction losses) under different operating conditions. Generally, when the three-level NPC inverter operates in the active output condition, the internal switching transistor incurs conduction losses, making low-conductivity switching devices suitable. However, when the three-level NPC inverter operates in the reactive output condition, the internal switching transistor incurs switching losses, making low-switching-loss switching devices suitable. Because the switching losses of low-conductivity switching devices are too high, it is impossible to simultaneously satisfy both low switching losses and low conduction losses for the internal switching transistor. This means that high-efficiency operation of the three-level NPC inverter cannot be guaranteed under all operating conditions, resulting in excessive losses and low efficiency. Summary of the Invention

[0003] This application provides a midpoint clamped inverter and a photovoltaic power supply system, which can flexibly select different switching units to bear the conduction loss or switching loss, thereby reducing the loss of the midpoint clamped inverter under all operating conditions, with high efficiency and strong applicability.

[0004] Firstly, this application provides a midpoint clamped inverter, which may include a power supply module, a switching module, and a control module. The power supply module may include a power source, and a first capacitor and a second capacitor connected in series and then in parallel across the power source. The switching module may include a first switching unit, a second switching unit, and a third switching unit. The first connection terminal of the first switching unit is connected to the positive terminal of the power source; the second connection terminal of the first switching unit is connected to the first connection terminal of the third switching unit; the third connection terminal of the first switching unit is connected to the first connection terminal of the second switching unit and the load; the second connection terminal of the second switching unit is connected to the second connection terminal of the third switching unit; the third connection terminal of the second switching unit is connected to the negative terminal of the power source and the load; and the third connection terminal of the third switching unit is connected to the first capacitor and the second capacitor. Each switching unit in the switching module may include at least one switch and / or a diode. The control module may be connected to the first switching unit, the second switching unit, and the third switching unit respectively. The control module can be used to control the on / off state of each switching unit in the first, second, and third switching units to select different switching units in the switching module to bear conduction losses or switching losses. In the midpoint clamp inverter provided in this application, the control module can control the conduction or cutoff of different switching units, thereby flexibly selecting different switching units to bear conduction losses or switching losses under different operating conditions, thereby reducing the inverter's losses under all operating conditions, improving the inverter's operating efficiency, and making it more flexible and adaptable.

[0005] In conjunction with the first aspect, in a first possible implementation, the midpoint clamp inverter may further include a filtering module. The filtering module may include an inductor and a third capacitor. One end of the inductor is connected to the third connection terminal of the first switching unit and the first connection terminal of the second switching unit, respectively. The other end of the inductor is connected to one end of the third capacitor and the load, respectively. The other end of the third capacitor is connected to the second connection terminal of the second switching unit and the load. In the midpoint clamp inverter provided in this application, the ripple in the inverter output voltage can be filtered out by the filtering module to obtain an AC signal with better characteristics, higher efficiency, and wider applicability.

[0006] In conjunction with the first aspect or the first possible implementation of the first aspect, in the second possible implementation, the third switching unit may include a first switch, a first diode, and a second diode. Specifically, the cathode of the first diode is connected to the first terminal of the first switch as the first connection terminal of the third switching unit; the anode of the second diode is connected to the second terminal of the first switch as the second connection terminal of the third switching unit; and the anode of the first diode is connected to the cathode of the second diode as the third connection terminal of the third switching unit. In the midpoint clamped inverter provided in this application, the first switch can be selected to bear the switching losses or conduction losses of the midpoint clamped inverter under different operating conditions (such as outputting active power or outputting reactive power), thereby reducing the inverter's losses under all operating conditions, improving the inverter's operating efficiency, and enhancing its adaptability.

[0007] In conjunction with the second possible implementation of the first aspect, in the third possible implementation, the first switching unit may include a second switch and a third switch, and the second switching unit may include a fourth switch and a fifth switch. Specifically, the first terminal of the second switch serves as the first connection terminal of the first switching unit; the second terminal of the second switch is connected to the first terminal of the third switch as the second connection terminal of the first switching unit; the second terminal of the third switch serves as the third connection terminal of the first switching unit; the first terminal of the fourth switch serves as the first connection terminal of the second switching unit; the second terminal of the fourth switch is connected to the first terminal of the fifth switch as the second connection terminal of the second switching unit; and the second terminal of the fifth switch serves as the third connection terminal of the second switching unit. The control module is connected to the third terminal of each of the first, second, third, fourth, and fifth switches to control the on / off state of each switch. It can be understood that the first terminal here can be the collector or drain of different types of switches, the second terminal can be the emitter or source of different types of switches, and the third terminal can be the base or gate of different types of switches. In the midpoint clamping inverter provided in this application, different switches (such as the first switch, the third switch, or the fourth switch) can be flexibly selected to bear the switching losses or conduction losses of the midpoint clamping inverter under different operating conditions, thereby reducing the inverter's losses under all operating conditions, improving the inverter's operating efficiency, and making it more flexible and adaptable.

[0008] In conjunction with the third possible implementation of the first aspect, in the fourth possible implementation, the control module is used to control the on / off state of each of the first, second, third, fourth, and fifth switches. This is to select the first, third, and fourth switches to bear the conduction loss based on the parallel current path when the midpoint clamped inverter outputs active power to the load; or to select the first switch to bear the switching loss and the third or fourth switch to bear the conduction loss when the midpoint clamped inverter outputs reactive power to the load, or to select the first switch to bear the conduction loss and the third or fourth switch to bear the switching loss. In the midpoint clamped inverter provided in this application, the first, third, and fourth switches can be selected to independently or jointly bear the switching or conduction losses under different operating conditions (such as outputting active power or outputting reactive power), thereby reducing the inverter's losses under all operating conditions, improving the inverter's operating efficiency, and enhancing its adaptability.

[0009] In conjunction with the third or fourth possible implementation of the first aspect, in the fifth possible implementation, the first, second, third, fourth, or fifth switch can be an insulated gate bipolar transistor (IGBT) or a metal-oxide-semiconductor field-effect transistor (MOSFET). Here, the IGBT can be a low-conduction-loss switching device, and the MOSFET can be a low-switching-loss switching device. In this application, the first, second, third, fourth, or fifth switch can be respectively set as low-conduction-loss or low-switching-loss switching devices (such as IGBTs or MOSFETs). Different types of switches (such as IGBTs or MOSFETs) can be flexibly selected to bear the conduction or switching losses of the midpoint clamped inverter under different operating conditions, thereby reducing the inverter's losses under all operating conditions, improving inverter operating efficiency, and offering greater flexibility and applicability.

[0010] In conjunction with the fifth possible implementation of the first aspect, in the sixth possible implementation, the first switch, the second switch, the third switch, the fourth switch, or the fifth switch may be made of silicon semiconductor material Si, or silicon carbide SiC, or gallium nitride GaN, or diamond, or zinc oxide ZnO, or other materials.

[0011] In a seventh possible implementation, combining any one of the third to sixth possible implementations of the first aspect, the first switch can be a MOSFET, and the second, third, fourth, and fifth switches can be IGBTs. The first, second, and third terminals of the first switch are the drain, source, and gate, respectively. The first terminal of each of the second, third, fourth, and fifth switches is the collector, the second terminal is the emitter, and the third terminal is the base. In this application, a MOSFET can be used as the first switch, and IGBTs can be used as the second, third, fourth, and fifth switches. When the midpoint clamped inverter outputs reactive power to the load, the first switch with low switching losses can be selected to bear the switching losses, while the third or fourth switch with low conduction losses can be selected to bear the conduction losses. This reduces the inverter's losses under all operating conditions, improves the inverter's operating efficiency, and enhances its adaptability.

[0012] In an eighth possible implementation, combining any one of the third to sixth possible implementations of the first aspect, the first switch, the second switch, and the fifth switch can be IGBTs, and the third switch and the fourth switch can be MOSFETs. Specifically, the first electrode of each of the first, second, and fifth switches is the collector of that switch, the second electrode of each switch is the emitter of that switch, and the third electrode of each switch is the base of that switch; the first electrode of the third and fourth switches is the drain of that switch and the second electrode of that switch and the third electrode of that switch is the source of that switch and the third electrode of that switch is the gate of that switch and the fourth switch. In this application, IGBTs can be used as the first, second, and fifth switches, and MOSFETs as the third and fourth switches. When the inverter is clamped at the midpoint and outputs active power to the load, the first, third, and fourth switches can be selected to bear the conduction losses based on the parallel current path. When the inverter is clamped at the midpoint and outputs reactive power to the load, the first switch with low conduction loss can be selected to bear the conduction losses, while the third or fourth switch with low switching loss can be selected to bear the switching losses. This reduces the inverter's losses under all operating conditions, improves the inverter's operating efficiency, and enhances its adaptability.

[0013] In a ninth possible implementation, combining any one of the third to eighth possible implementations of the first aspect, the control module can be used to generate control signals for controlling each of the first, second, third, fourth, and fifth switches. These control signals are used to control the on / off state of each switch, thereby enabling the on / off state of each switch unit. In this application, the on / off state of each switch can be controlled by the control signals generated by the control module, allowing for flexible selection of different switches to independently or jointly bear the switching or conduction losses under different operating conditions. This reduces inverter losses under all operating conditions, improves inverter operating efficiency, and enhances flexibility and adaptability.

[0014] In conjunction with the ninth possible implementation of the first aspect, in the tenth possible implementation, the control module can be used to: control the first switch to turn on, and control the fourth switch to turn on after a first preset delay time, and control the first switch to turn off after a second preset delay time after controlling the fourth switch to turn off; control the first switch to turn on, and control the third switch to turn on after a third preset delay time, and control the first switch to turn off after a fourth preset delay time after controlling the third switch to turn off. In this application, the control module can control the on / off of the first switch, the third switch, and the fourth switch based on different preset delay times, thereby allowing the first switch to bear the switching losses when the inverter outputs reactive power to the load at the midpoint clamp, and the third switch or the fourth switch to bear the conduction losses under different operating conditions. Since the first switch is a low-switching-loss switching device (such as a MOSFET), and the third and fourth switches are low-conduction-loss switching devices (such as IGBTs), the inverter losses under all operating conditions are reduced, the inverter operating efficiency is improved, and the adaptability is stronger.

[0015] In conjunction with the ninth possible implementation of the first aspect, in the eleventh possible implementation, the control module can be used to: control the fourth switch to turn on, and control the first switch to turn on after a first preset delay time, and control the fourth switch to turn off after a second preset delay time after controlling the first switch to turn off; control the third switch to turn on, and control the first switch to turn on after a third preset delay time, and control the third switch to turn off after a fourth preset delay time after controlling the first switch to turn off. In this application, the control module can control the on / off states of the first, third, and fourth switches based on different preset delay times, thereby allowing the first, third, and fourth switches to be selected to bear the conduction losses when outputting active power based on a parallel current path, while simultaneously selecting the first switch to bear the conduction losses when outputting reactive power, and selecting either the third or fourth switch to bear the switching losses when outputting reactive power. Since the first switch is a low-conduction-loss switching device (such as an IGBT), and the third and fourth switches are low-switching-loss switching devices (such as MOSFETs), the inverter losses under all operating conditions are reduced, the inverter operating efficiency is improved, and the adaptability is stronger.

[0016] In conjunction with the tenth or eleventh possible implementation of the first aspect, in the twelfth possible implementation, the control module is used to determine a first preset delay time, a second preset delay time, a third preset delay time, and a fourth preset delay time based on the junction temperature of the devices corresponding to the first, second, third, fourth, and fifth switches, and / or the load current flowing through the load. In this application, different preset delay times can be determined by the control module, and the first, third, and fourth switches can be controlled to turn on or off based on these different preset delay times. This allows the first, third, and fourth switches to be selected to independently or jointly bear the switching losses or conduction losses under different operating conditions, thereby reducing inverter losses under all operating conditions, improving inverter operating efficiency, and enhancing adaptability.

[0017] Secondly, this application provides a photovoltaic power supply system, which may include a photovoltaic array and a midpoint clamping inverter connected to the photovoltaic array, as provided in any of the first to twelfth possible embodiments described above. It is understood that the photovoltaic array can be connected to the DC side of the midpoint clamping inverter to provide a DC input voltage to the inverter, and the AC side of the midpoint clamping inverter can be connected to a load to provide AC power to the load. The photovoltaic array may include multiple photovoltaic modules (also referred to as solar panels or photovoltaic panels) and / or other photovoltaic power supply devices.

[0018] In this application, the midpoint clamped inverter can flexibly select different switching units based on the control module to bear the switching losses or conduction losses under different operating conditions (such as outputting active power or outputting reactive power), thereby reducing the inverter's losses under all operating conditions, improving the inverter's operating efficiency, and making it more flexible and adaptable. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the application scenario of the midpoint clamp inverter provided in this application;

[0020] Figure 2 This is a circuit diagram of the midpoint clamp inverter provided in this application;

[0021] Figure 3 This is another circuit diagram of the midpoint clamp inverter provided in this application;

[0022] Figure 4 This is another circuit diagram of the midpoint clamp inverter provided in this application;

[0023] Figure 5 This is a switching timing diagram of the midpoint clamped inverter provided in this application;

[0024] Figure 6 This is a schematic diagram of a converter circuit when the midpoint clamped inverter outputs active power, as provided in this application.

[0025] Figure 7 This is a schematic diagram of a converter circuit when the midpoint clamped inverter outputs reactive power, as provided in this application.

[0026] Figure 8 This is another circuit diagram of the midpoint clamp inverter provided in this application;

[0027] Figure 9 This is another switching timing diagram of the midpoint clamp inverter provided in this application;

[0028] Figure 10 This is a schematic diagram of another converter circuit when the midpoint clamped inverter outputs active power as provided in this application;

[0029] Figure 11 This is a schematic diagram of another converter circuit when the midpoint clamped inverter outputs reactive power, as provided in this application.

[0030] Figure 12 This is another circuit diagram of the midpoint clamp inverter provided in this application. Detailed Implementation

[0031] An inverter is a converter that transforms direct current (DC) (such as from batteries or storage batteries) into alternating current (AC) with fixed frequency and voltage or variable frequency and voltage. Inverters (such as midpoint clamp inverters) generally consist of an inverter bridge circuit, control logic circuits, and filter circuits. They are widely used in electrical appliances (such as household appliances) and power grids. For example, an inverter can connect to a battery to power electrical appliances, or it can transmit high-power, high-voltage AC power to the power grid. The midpoint clamp inverter provided in this application can also be called an NPC inverter, a three-level midpoint clamp inverter, or a three-level NPC inverter. This midpoint clamp inverter is suitable for various applications, including photovoltaic power generation (such as supplying power to household appliances (such as refrigerators and air conditioners) or the power grid), wind power generation, and high-power converters (such as converting DC to high-power, high-voltage AC). The specific application can be determined based on the actual application scenario and is not limited here.

[0032] The midpoint clamped inverter provided in this application may include a power supply module, a switching module, and a control module. The power supply module may include a power source, and a first capacitor and a second capacitor connected in series and then in parallel across the power source. The switching module may include a first switching unit, a second switching unit, and a third switching unit. The control module may be connected to the first, second, and third switching units respectively. The control module can be used to control the on / off state of each switching unit in the first, second, and third switching units, thereby selecting different switching units in the switching module to bear the conduction loss or switching loss. The midpoint clamped inverter provided in this application can flexibly select different switching units to bear the switching loss or conduction loss under different operating conditions (such as outputting active power or outputting reactive power) based on the control module, thereby reducing the inverter's losses under all operating conditions, improving the inverter's operating efficiency, and providing greater flexibility and adaptability. The midpoint clamping inverter provided in this application can be adapted to different application scenarios, such as any application scenario that requires the conversion of DC power to AC power, such as solar power supply scenarios and wind power supply scenarios. This application will use the solar power supply scenario as an example for illustration.

[0033] See Figure 1 , Figure 1 This is a schematic diagram illustrating an application scenario for the midpoint clamped inverter provided in this application. For example... Figure 1As shown, a photovoltaic power supply system (such as photovoltaic power supply system 10) may include a photovoltaic array (such as photovoltaic array 1) and a midpoint clamping inverter (such as midpoint clamping inverter 2) connected to the photovoltaic array. The photovoltaic array 1 may include multiple photovoltaic modules (also referred to as solar panels or photovoltaic panels) and / or other photovoltaic power supply devices (such as photovoltaic combiner boxes). The photovoltaic array 1 can be connected to the DC side of the midpoint clamping inverter 2, providing a DC input voltage to the midpoint clamping inverter 2. In other words, the photovoltaic array 1 provides DC power to the midpoint clamping inverter 2. The DC input voltage value can be 12V, 24V, 36V, 48V, or other voltage values. The AC side of the midpoint clamp inverter 2 can be directly or indirectly connected to a load (such as household appliances 3 or the power grid 5). The midpoint clamp inverter 2 can convert the DC power provided by the photovoltaic array 1 into AC power (such as 220V, 50Hz sine wave AC power or other voltage values) and power household appliances 3 (such as refrigerators, air conditioners, etc.). Optionally, the midpoint clamp inverter 2 can also input AC power to the boost converter 4. The boost converter 4 can boost the AC power input by the midpoint clamp inverter 2 to high voltage (such as 32KV, 110KV, 220KV or other voltage values) and input the boosted high voltage power to the high voltage power grid (such as the power grid 5). The specific method can be determined according to the actual application scenario and is not limited here. The midpoint clamp inverter in this application (such as the midpoint clamp inverter 2 mentioned above) can reduce losses under all operating conditions, improve inverter operating efficiency, further improve power supply efficiency, and has stronger applicability.

[0034] The following will combine Figures 2 to 12 This application provides an example illustrating the midpoint clamp inverter and its working principle.

[0035] See Figure 2 , Figure 2 This is a circuit diagram of the midpoint clamped inverter provided in this application. For example... Figure 2 As shown, the midpoint clamp inverter may include a power supply module 10, a switching module 20, and a control module 30. The power supply module 10 may include a power source, and a first capacitor C1 and a second capacitor C2 connected in series and then in parallel across the power source. The power source here is a DC input power source, and the power supply voltage can be V. dc The first capacitor C1 and the second capacitor C2 can be DC bus capacitors. The voltages across the first capacitor C1 are the positive terminal voltage BUS. + (BUS + =V dc / 2) and the zero-point voltage BUSN, the voltages across the second capacitor C2 are the zero-point voltage BUSN and the negative terminal voltage BUS, respectively. - (BUS - =-Vdc / 2). The switching module 20 may include at least one switching unit, for example, it may specifically include a first switching unit 201, a second switching unit 202, and a third switching unit 203. The first connection terminal of the first switching unit 201 can be connected to the positive terminal of the power supply; the second connection terminal of the first switching unit 201 can be connected to the first connection terminal of the third switching unit 203; the third connection terminal of the first switching unit 201 can be connected to the first connection terminal of the second switching unit 202 and the load; the second connection terminal of the second switching unit 202 can be connected to the second connection terminal of the third switching unit 203; the third connection terminal of the second switching unit 202 can be connected to the negative terminal of the power supply and the load; and the third connection terminal of the third switching unit 203 can be connected to the first capacitor C1 and the second capacitor C2. The current flowing through the load can be represented as i0, and the output voltage of the midpoint clamped inverter can be represented as V. out It should be understood that any switching unit in the switching module 20 may include at least one switch and / or diode, or any switching unit may include at least one switch and / or diode and / or capacitor and / or inductor and / or other devices, which can be determined according to the actual application scenario and is not limited here. The aforementioned control module 30 can be connected to the first switching unit 201, the second switching unit 202, and the third switching unit 203 respectively. The control module 30 can control the conduction or cutoff of each switching unit in the first switching unit 201, the second switching unit 202, and the third switching unit 203, so as to select any one of the first switching unit 201, the second switching unit 202, and the third switching unit 203 to independently bear the conduction loss or the switching loss, or to select any two or three of the first switching unit 201, the second switching unit 202, and the third switching unit 203 to jointly bear the conduction loss or the switching loss. Thus, different switching units in the switch module 20 can be flexibly selected to directly or jointly bear the conduction loss or the switching loss of the midpoint clamped inverter under different operating conditions, which is more flexible and more adaptable.

[0036] See Figure 3 , Figure 3 This is another circuit diagram of the midpoint clamped inverter provided in this application. For example... Figure 3 As shown above Figure 2 The midpoint clamped inverter shown may also include a filter module 40, which may include an inductor L and a third capacitor C3. One end of the inductor L is connected to the third connection terminal of the first switching unit 201 and the first connection terminal of the second switching unit 202, respectively. The other end of the inductor L is connected to one end of the third capacitor C3 and the load, respectively. The other end of the third capacitor C3 is connected to the second connection terminal of the second switching unit 202 and the load. Please refer to [further details omitted]. Figure 4 , Figure 4This is another circuit diagram of the midpoint clamped inverter provided in this application. For example... Figure 4 As shown above Figure 3 The first switch unit 201 shown may include a second switch S1 and a third switch S2, as described above. Figure 3 The second switch unit 202 shown may include a fourth switch S3 and a fifth switch S4, as described above. Figure 3 The third switching unit 203 shown may include a first switch Q5, a first diode D5, and a second diode D6. The second switch S1 may include a switching device Q1 and a freewheeling diode D1 connected in parallel across the switching device Q1; the third switch S2 may include a switching device Q2 and a freewheeling diode D2 connected in parallel across the switching device Q2; the fourth switch S3 may include a switching device Q3 and a freewheeling diode D3 connected in parallel across the switching device Q3; and the fifth switch S4 may include a switching device Q4 and a freewheeling diode D4 connected in parallel across the switching device Q4. For the first switching unit 201, the first terminal of the second switch S1 serves as the first connection terminal of the first switching unit 201; the second terminal of the second switch S1 is connected to the first terminal of the third switch S2 as the second connection terminal of the first switching unit 201; and the second terminal of the third switch S2 serves as the third connection terminal of the first switching unit 201. For the second switching unit 202, the first terminal of the fourth switch S3 serves as the first connection terminal of the second switching unit 202; the second terminal of the fourth switch S3 is connected to the first terminal of the fifth switch S4, serving as the second connection terminal of the second switching unit 202; and the second terminal of the fifth switch S4 serves as the third connection terminal of the second switching unit 202. For the third switching unit 203, the cathode of the first diode D5 is connected to the first terminal of the first switch Q5, serving as the first connection terminal of the third switching unit 203; the anode of the second diode D6 is connected to the second terminal of the first switch Q5, serving as the second connection terminal of the third switching unit 203; and the anode of the first diode D5 is connected to the cathode of the second diode D6, serving as the third connection terminal of the third switching unit 203. Figure 4 As shown, the control module 30 can be connected to the third terminal of each of the first switch Q5, the second switch S1, the third switch S2, the fourth switch S3, and the fifth switch S4, thereby controlling the on or off state of each switch. It can be understood that the first terminal can be the collector or drain of different types of switches, the second terminal can be the emitter or source of different types of switches, and the third terminal can be the base or gate of different types of switches.

[0037] In some feasible implementations, the first switch Q5, the second switch S1, the third switch S2, the fourth switch S3, or the fifth switch S4 can be MOSFETs, IGBTs, or diodes made of silicon semiconductor material (Si), or third-generation wide-bandgap semiconductor material silicon carbide (SiC), or gallium nitride (GaN), or diamond, or zinc oxide (ZnO), or other materials. The specific choice depends on the actual application scenario and is not limited here. For example, as... Figure 4 As shown, the first switch Q5 can be a MOSFET, and the second, third, fourth, and fifth switches S1 and S2 can be IGBTs. It can be understood that the first, second, and third terminals of the first switch Q5 are the drain, source, and gate, respectively. The first terminal of each of the second, third, fourth, and fifth switches S1, S2, S3, and S4 can be the collector of that switch; the second terminal of each of the second, third, fourth, and fifth switches S4 can be the emitter of that switch; and the third terminal of each of the second, third, fourth, and fifth switches S4 can be the base of that switch.

[0038] In some feasible implementations, the control module 30 can generate control signals for controlling the first switch Q5, the second switch S1, the third switch S2, the fourth switch S3, and the fifth switch S4. These control signals can be pulse width modulation (PWM) signals for the first switch Q5, the second switch S1, the third switch S2, the fourth switch S3, and the fifth switch S4, which can be simply referred to as PWM signals. The control signals can also be understood as PWM signals used to control the switching devices Q1, Q2, Q3, Q4, and the first switch Q5. These control signals can be used to control the on or off state of each of the first switch Q5, the second switch S1, the third switch S2, the fourth switch S3, and the fifth switch S4. For example, the control signal (0 1 1 0 1) can control the second switch S1 to be off, the third switch S2 to be on, the fourth switch S3 to be on, the fifth switch S4 to be off, and the first switch Q5 to be on. Please refer to [further details omitted]. Figure 5 , Figure 5 This is a switching timing diagram of the midpoint clamped inverter provided in this application. For example... Figure 5As shown, the output voltage V of the inverter with midpoint clamping out During the positive half-cycle (i.e., the positive half-period), the third switch S2 remains on, and the fifth switch S4 remains off (i.e., cut-off). The second switch S1, the fourth switch S3, and the first switch Q5 can operate in PWM mode. The second switch S1 and the first switch Q5 can be complementary switches. PWM mode is an effective mode that uses the digital output signal of a microprocessor (such as control module 30) to control an analog circuit. The complementary switches are a pair of push-pull switches; when one switch is closed, the other is open, such as the second switch S1 being on and the first switch Q5 being off, or the second switch S1 being off and the first switch Q5 being on. For the second switch S1 and the first switch Q5 as complementary switches, to prevent them from being on simultaneously, a dead time, such as t, needs to be added between them. d1 Or t d2 , where t d1 The dead time t can be defined as the time between the turn-off of the second switch S1 and the turn-on of the first switch Q5. d2 This can be the dead time from the moment the first switch Q5 turns off to the moment the second switch S1 turns on. The output voltage V of the inverter is clamped at the midpoint. out During the negative half-cycle, the fourth switch S3 remains on, and the second switch S1 remains off. The third switch S2, the fifth switch S4, and the first switch Q5 operate in PWM mode, with the fifth switch S4 and the first switch Q5 being complementary switches. To prevent the fifth switch S4 and the first switch Q5 from conducting simultaneously, a dead time, such as t, needs to be added between them. d3 Or t d4 , where t d3 The dead time t can be defined as the time between the turn-off of the fifth switch S4 and the turn-on of the first switch Q5. d4 It can be the dead time from the moment the first switch Q5 is turned off to the moment the fifth switch S4 is turned on.

[0039] In some feasible implementations, when the first switch Q5, the second switch S1, the third switch S2, the fourth switch S3, and the fifth switch S4 are all different types of switches (such as IGBTs or MOSFETs), the control module 30 can set different first preset times, second preset times, third preset times, and fourth preset times to control the conduction or cutoff of the first switch Q5, the third switch S2, and the fourth switch S3. If the first switch Q5 is a MOSFET, and the second switch S1, the third switch S2, the fourth switch S3, and the fifth switch S4 are IGBTs, the output voltage V of the inverter is clamped at the midpoint. out During the positive half-cycle, the control module 30 can control the first switch Q5 to turn on, and after a first preset delay time (such as preset delay time t), delay1 After that, control the fourth switch S3 to turn on, and after the fourth switch S3 turns off, there is a second preset delay time (such as preset delay time t). delay2 Then, control the first switch Q5 to turn off; or clamp the inverter's output voltage V at the midpoint. out During the negative half-cycle, the control module 30 can also control the first switch Q5 to turn on, and after a third preset delay time (such as preset delay time t) delay3 After that, control the third switch S2 to turn on, and after the third switch S2 is turned off, a fourth preset delay time (such as preset delay time t) is performed. delay4 Then, control the first switch Q5 to turn off.

[0040] For ease of description, the following will combine Figures 6 to 7 The working principle of the switching module in the midpoint clamp inverter provided in this application is illustrated with an example. Please refer to [link / reference needed]. Figure 6 , Figure 6 This is a schematic diagram of a converter circuit when the midpoint clamped inverter is outputting active power, as provided in this application. Figure 6 As shown, the output voltage V of the inverter with midpoint clamping out When the inverter is in the positive half-cycle and the load current i0 is greater than 0, the midpoint clamped inverter outputs active power to the load. In other words, the midpoint clamped inverter operates under active power output conditions. Under these conditions, the second switch S1, the fourth switch S3, and the first switch Q5 operate in PWM mode. The commutation circuits with each switch in different switching states can be configured as follows: Figure 6 As shown in 6a, the switch state here can refer to either the on state or the off state (also known as the cut-off state). For example... Figure 6As shown in Figure 6a, when switching device Q1 is on, current flows through switching devices Q1 and Q2; when switching device Q1 is off and the first switch Q5 is on, there are two current paths simultaneously: one flowing through the first diode D5, the first switch Q5, and the freewheeling diode D3, and the other flowing through the first diode D5 and switching device Q2. Since the on-state voltage drop of switching device Q2 is lower, current will flow through the first diode D5 and switching device Q2; after a preset delay time t... delay1 Afterwards, switching device Q3 is turned on, and current still flows through the first diode D5 and switching device Q2. It can be seen that switching device Q1 and the first diode D5 participate in commutation and generate switching losses; switching device Q2 is always turned on and generates conduction losses, which in turn means that the third switch S2 will generate conduction losses; no current flows through switching device Q3 and the first switch Q5, so no losses are generated.

[0041] The output voltage V of the inverter is clamped at the midpoint. out During the negative half-cycle, when the load current i0 is less than 0, the midpoint clamped inverter outputs active power to the load; in other words, the midpoint clamped inverter operates under active power output conditions. Under these conditions, the third switch S2, the fifth switch S4, and the first switch Q5 operate in PWM mode. The commutation circuits with each switch in different switching states can be configured as follows: Figure 6 As shown in Figure 6b, when switch Q4 is on, current flows through switch Q3 and switch Q4; when switch Q4 is off and the first switch Q5 is on, there are two current paths simultaneously: one flowing through freewheeling diode D2, the first switch Q5, and the second diode D6, and the other flowing through switch Q3 and the second diode D6. Since the forward voltage drop of switch Q3 is lower, current flows through switch Q3 and the second diode D6; after a preset delay time t... delay3 Afterwards, switch Q2 is turned on, and current still flows through switch Q3 and the second diode D6. It can be concluded that switch Q4 and the second diode D6 participate in commutation, generating switching losses; switch Q3 is always turned on, generating conduction losses, and consequently, the fourth switch S3 will generate conduction losses; switch Q2 and the first switch Q5 have no current flowing through them and therefore generate no losses.

[0042] Please see also Figure 7 , Figure 7 This is a schematic diagram of a converter circuit when the midpoint clamped inverter is outputting reactive power, as provided in this application. Figure 7 As shown, the output voltage V of the inverter with midpoint clamping outWhen the inverter is in the positive half-cycle and the load current i0 is less than 0, the neutral-point clamped inverter outputs reactive power to the load. In other words, the neutral-point clamped inverter operates under reactive power output conditions. Under these conditions, the second switch S1, the fourth switch S3, and the first switch Q5 operate in PWM mode. The commutation circuits with each switch in different switching states can be configured as follows: Figure 7 As shown in Figure 7a, when switching device Q1 is turned on, current flows through freewheeling diode D2 and freewheeling diode D1; when switching device Q1 is turned off and first switch Q5 is turned on, current flows through freewheeling diode D2, first switch Q5, and second diode D6; after a preset delay time t... delay1 Afterwards, switching device Q3 turns on. At this time, there are two current paths: one flowing through freewheeling diode D2, the first switch Q5, and the second diode D6, and the other flowing through switching device Q3 and the second diode D6. Since the forward voltage drop of the current path flowing through switching device Q3 and the second diode D6 is lower, the current will flow through switching device Q3 and the second diode D6. It can be seen that the first switch Q5 and the freewheeling diode D1 participate in commutation and generate switching losses; the freewheeling diode D2 generates conduction losses; switching device Q3 is in a zero-voltage switching state, with no switching losses, but it generates conduction losses. Therefore, it can be concluded that the fourth switch S3 will generate conduction losses. The zero-voltage switching state here can be understood as the state in which the voltage across the switch (such as switching device Q3) is 0 when it is turned on or off.

[0043] The output voltage V of the inverter is clamped at the midpoint. out During the negative half-cycle, when the load current i0 is greater than 0, the midpoint clamped inverter outputs reactive power to the load; in other words, the midpoint clamped inverter operates under reactive power output conditions. Under these conditions, the third switch S2, the fifth switch S4, and the first switch Q5 operate in PWM mode. The commutation circuits with each switch in different switching states can be configured as follows: Figure 7 As shown in Figure 7b, when switching device Q4 is on, current flows through freewheeling diodes D4 and D3; when switching device Q4 is off and the first switch Q5 is on, current flows through the first diode D5, the first switch Q5, and the freewheeling diode D3; after a preset delay time t... delay3Afterwards, switching device Q2 turns on. At this time, there are two current paths: one flowing through the first diode D5, the first switch Q5, and the freewheeling diode D3, and the other flowing through the first diode D5 and switching device Q2. Since the forward voltage drop of the current path flowing through the first diode D5 and switching device Q2 is lower, current will flow through the first diode D5 and switching device Q2. It can be concluded that the first switch Q5 and the freewheeling diode D4 participate in commutation and generate switching losses; the freewheeling diode D3 generates conduction losses; switching device Q2 is in a zero-voltage switching state, with no switching losses, but it generates conduction losses. Therefore, it can be concluded that the third switch S2 will generate conduction losses.

[0044] In combination with the above Figures 6 to 7 As described in the embodiment, when the midpoint clamped inverter outputs active power or reactive power to the load, the control module 30 can control the on or off of each switch to select either the third switch S2 or the fourth switch S3 to bear the conduction loss, while simultaneously selecting the first switch Q5 to bear the switching loss when the midpoint clamped inverter outputs reactive power to the load. Since both the third switch S2 and the fourth switch S3 are low-conduction-loss switching devices, and the first switch Q5 is a low-switching-loss switching device, the conduction loss can be borne by the low-conduction-loss third switch S2 or the fourth switch S3, and the switching loss by the low-switching-loss first switch Q5. This reduces the operating loss of the midpoint clamped inverter under all operating conditions, improves the inverter's operating efficiency, and enhances its adaptability.

[0045] Please see Figure 8 , Figure 8 This is another circuit diagram of the midpoint clamped inverter provided in this application. For example... Figure 8 As shown, in some feasible implementations, the second switch S1, the fourth switch S3, and the first switch Q5 can be IGBTs, and the third switch S2 and the fourth switch S3 can be MOSFETs. It can be understood that the first electrode of each of the second switches S1, S3, and Q5 is the collector of each of the second switches S1, S3, and Q5; the second electrode of each of the second switches S1, S3, and Q5 is the emitter of each of the second switches S1, S3, and Q5; and the third electrode of each of the second switches S1, S3, and Q5 is the base of each of the second switches S1, S3, and Q5. The first electrode of the third switches S2 and S3 is the drain of the third switches S2 and S3; the second electrode of the third switches S2 and S3 is the source of the third switches S2 and S3; and the third electrode of the third switches S2 and S3 is the gate of the third switches S2 and S3.

[0046] like Figure 8 As shown, the control module 30 can generate control signals for controlling the first switch Q5, the second switch S1, the third switch S2, the fourth switch S3, and the fifth switch S4. These control signals can be used to control the on / off states of the second switch S1, the third switch S2, the fourth switch S3, the fifth switch S4, and the first switch Q5. Please refer to [the documentation / reference]. Figure 9 , Figure 9 This is another switching timing diagram of the midpoint clamped inverter provided in this application. For example... Figure 9 As shown, the output voltage V of the inverter with midpoint clamping out During the positive half-cycle, the third switch S2 remains on, and the fifth switch S4 remains off. The second switch S1, the fourth switch S3, and the first switch Q5 can operate in PWM mode. The second switch S1 and the fourth switch S3 can be complementary switches. To prevent the second switch S1 and the fourth switch S3 from conducting simultaneously, a dead time, such as t, needs to be added between them. d5 Or t d6 , where t d5 The dead time t can be defined as the time between the turn-off of the second switch S1 and the turn-on of the fourth switch S3. d6 This can be the dead time from the moment the fourth switch S3 turns off to the moment the second switch S1 turns on. The output voltage V of the inverter is clamped at the midpoint. out During the negative half-cycle, the fourth switch S3 remains on, and the second switch S1 remains off. The third switch S2, the fifth switch S4, and the first switch Q5 operate in PWM mode, with the third switch S2 and the fifth switch S4 being complementary switches. To prevent the third switch S2 and the fifth switch S4 from conducting simultaneously, a dead time, such as t, needs to be added between them. d7 Or t d8 , where t d7 The dead time t can be defined as the time between the turn-off of the fifth switch S4 and the turn-on of the third switch S2. d8 It can be the dead time from the moment the third switch S2 is turned off to the moment the fifth switch S4 is turned on.

[0047] In some feasible implementations, if the second switch S1, the fourth switch S3, and the first switch Q5 are IGBTs, and the third switch S2 and the fourth switch S3 are MOSFETs, the output voltage V of the inverter is clamped at the midpoint. out During the positive half-cycle, the control module 30 can control the fourth switch S3 to turn on, and after a first preset delay time (such as the preset delay time t),delay5 After that, the first switch Q5 is turned on, and after the first switch Q5 is turned off, a second preset delay time (such as preset delay time t) is performed. delay6 Then, control the fourth switch S3 to turn off; or clamp the inverter's output voltage V at the midpoint. out During the negative half-cycle, the control module 30 can also control the third switch S2 to turn on, and after a third preset delay time (such as preset delay time t) delay7 After that, control the first switch Q5 to turn on, and after the first switch Q5 is turned off, there is a fourth preset delay time (such as preset delay time t). delay8 Then, control the third switch S2 to turn off.

[0048] For ease of description, the following will combine Figures 10 to 11 The working principle of the switching module in the midpoint clamp inverter provided in this application is illustrated with an example. Please refer to [link / reference needed]. Figure 10 , Figure 10 This is a schematic diagram of another converter circuit when the midpoint clamped inverter outputs active power, as provided in this application. For example... Figure 10 As shown, the output voltage V of the inverter clamped at the midpoint out When the inverter is in the positive half-cycle and the load current i0 is greater than 0, the midpoint clamped inverter outputs active power to the load. In other words, the midpoint clamped inverter operates under active power output conditions. Under these conditions, the second switch S1, the fourth switch S3, and the first switch Q5 operate in PWM mode. The commutation circuits with each switch in different switching states can be configured as follows: Figure 10 As shown in Figure 10a, when switching device Q1 is on, current flows through switching devices Q1 and Q2; when switching device Q1 is off and switching device Q3 is on, current flows through the first diode D5 and switching device Q2; after a preset delay time t... delay5 Afterwards, the first switch Q5 is turned on. At this time, there are two current paths simultaneously: one flowing through the first diode D5, the switching device Q2, and the first diode D5; and the other flowing through the first switch Q5 and the freewheeling diode D3. This parallel conduction of two current paths reduces conduction losses. It can be seen that the switching device Q1 and the first diode D5 participate in commutation and generate switching losses; the switching device Q2 is always on and generates conduction losses; consequently, the third switch S2 will generate conduction losses; the first switch Q5 only generates conduction losses; and the freewheeling diode D3 generates both conduction losses and reverse recovery losses.

[0049] The output voltage V of the inverter is clamped at the midpoint. outDuring the negative half-cycle, when the load current i0 is less than 0, the midpoint clamped inverter outputs active power to the load; in other words, the midpoint clamped inverter operates under active power output conditions. Under these conditions, the third switch S2, the fifth switch S4, and the first switch Q5 operate in PWM mode. The commutation circuits with each switch in different switching states can be configured as follows: Figure 10 As shown in 10b, when switching device Q4 is on, current flows through switching devices Q3 and Q4; when switching device Q4 is off and switching device Q2 is on, current flows through switching device Q3 and the second diode D6; after a preset delay time t... delay7 Afterwards, the first switch Q5 is turned on. At this time, there are two current paths simultaneously: one flowing through the switching device Q3, the second diode D6, and the freewheeling diode D2, and the other flowing through the first switch Q5 and the second diode D6. This parallel conduction of two current paths reduces conduction losses. It can be seen that the switching device Q4 and the second diode D6 participate in commutation, generating switching losses; the switching device Q3 is always on, generating conduction losses; consequently, the fourth switch S3 will generate conduction losses; the first switch Q5 will generate conduction losses; and the freewheeling diode D2 will generate both conduction losses and reverse recovery losses.

[0050] Please see also Figure 11 , Figure 11 This is a schematic diagram of another converter circuit when the midpoint clamped inverter outputs reactive power, as provided in this application. For example... Figure 11 As shown, the output voltage V of the inverter with midpoint clamping out When the inverter is in the positive half-cycle and the load current i0 is less than 0, the neutral-point clamped inverter outputs reactive power to the load. In other words, the neutral-point clamped inverter operates under reactive power output conditions. Under these conditions, the second switch S1, the fourth switch S3, and the first switch Q5 operate in PWM mode. The commutation circuits with each switch in different switching states can be configured as follows: Figure 11 As shown in 11a, when switching device Q1 is on, current flows through freewheeling diode D2 and freewheeling diode D1; when switching device Q1 is off and switching device Q3 is on, current flows through switching device Q3 and the second diode D6; after a preset delay time t... delay5When the first switch Q5 is turned on, two current paths exist simultaneously: one flowing through the freewheeling diode D2, the first switch Q5, and the second diode D6; and the other flowing through the switching device Q3 and the second diode D6. This parallel conduction of current paths reduces conduction losses. It can be deduced that the switching device Q3 and the freewheeling diode D1 participate in commutation, generating switching losses, which in turn leads to switching losses in the fourth switch S3; the freewheeling diode D2 and the second diode D6 generate conduction losses; and the first switch Q5, being in a zero-voltage switching state, experiences no switching losses but still generates conduction losses.

[0051] The output voltage V of the inverter is clamped at the midpoint. out During the negative half-cycle, when the load current i0 is greater than 0, the midpoint clamped inverter outputs reactive power to the load; in other words, the midpoint clamped inverter operates under reactive power output conditions. Under these conditions, the third switch S2, the fifth switch S4, and the first switch Q5 operate in PWM mode. The commutation circuits with each switch in different switching states can be configured as follows: Figure 11 As shown in 11b, when switching device Q4 is on, current flows through freewheeling diodes D4 and D3; when switching device Q4 is off and switching device Q2 is on, current flows through the first diode D5 and switching device Q2; after a preset delay time t... delay7 Afterwards, the first switch Q5 is turned on. At this time, there are two current paths simultaneously: one flowing through the first diode D5, the first switch Q5, and the freewheeling diode D3, and the other flowing through the first diode D5 and the switching device Q2. This parallel conduction of two current paths reduces conduction losses. It can be deduced that the switching device Q2 and the freewheeling diode D4 participate in commutation, generating switching losses. Consequently, the third switch S2 will also generate switching losses; the freewheeling diode D3 and the first diode D5 will generate conduction losses; and the first switch Q5, being in a zero-voltage switching state, will generate conduction losses despite having no switching losses.

[0052] In combination with the above Figures 10 to 11As described in the embodiment, when the midpoint clamped inverter outputs active power to the load, the control module 30 can control the on or off of each switch to select the third switch S2, the fourth switch S3, and the first switch Q5 based on parallel conduction current paths to reduce conduction losses. When the midpoint clamped inverter outputs reactive power to the load, the control module 30 can control the on or off of each switch to select the first switch Q5 to bear the conduction losses, while selecting either the third switch S2 or the fourth switch S3 to primarily bear the switching losses under reactive power output conditions. Since the third switch S2 and the fourth switch S3 are low-switching-loss switching devices, and the first switch Q5 is a low-conduction-loss switching device, the switching losses are mainly borne by the low-switching-loss third switch S2 and the fourth switch S3, and the conduction losses are borne by the low-conduction-loss first switch Q5. This reduces the operating losses of the inverter under all operating conditions, improves the inverter's operating efficiency, and enhances its adaptability.

[0053] Please see Figure 12 , Figure 12 This is another circuit diagram of the midpoint clamped inverter provided in this application. For example... Figure 12 As shown, in some feasible implementations, the second switch S1, the third switch S2, the fourth switch S3, the fifth switch S4, and the first switch Q5 can be controllable power switching devices, such as IGBTs or MOSFETs. The output voltage V of the inverter is clamped at the midpoint. out During the positive half-cycle, the third switch S2 remains on, and the fifth switch S4 remains off. The second switch S1, the fourth switch S3, and the first switch Q5 can operate in PWM mode; the second switch S1 and the fourth switch S3 can be complementary switches. The output voltage V of the inverter is clamped at the midpoint. out During the positive half-cycle, the fourth switch S3 remains on, and the second switch S1 remains off. The third switch S2, the fifth switch S4, and the first switch Q5 operate in PWM mode, with the third switch S2 and the fifth switch S4 being complementary switches.

[0054] In some feasible implementations, the control module 30 can also determine a first preset delay time, a second preset delay time, a third preset delay time, and a fourth preset delay time based on the junction temperature of the devices corresponding to each of the first switch Q5, the second switch S1, the third switch S2, the fourth switch S3, and the fifth switch S4, and / or the load current i0 flowing through the load. The junction temperature of the devices of the second switch S1, the third switch S2, the fourth switch S3, the fifth switch S4, and the first switch Q5 can be expressed as T. j j is a positive integer greater than 0 and less than or equal to the number of switches (e.g., 5) in switch module 20. Assume the first preset delay time is the aforementioned preset delay time t. delay1The second preset delay time is the aforementioned preset delay time t. delay2 The third preset delay time is the aforementioned preset delay time t. delay3 The fourth preset delay time is the aforementioned preset delay time t. delay4 The switching timing diagram of the midpoint clamp inverter can be as described above. Figure 5 As shown, the converter circuit diagram of the midpoint clamp inverter can be as described above. Figures 6-7 As shown. Assume the first preset delay time is the aforementioned preset delay time t. delay5 The second preset delay time is the aforementioned preset delay time t. delay6 The third preset delay time is the aforementioned preset delay time t. delay7 The fourth preset delay time is the aforementioned preset delay time t. delay8 The switching timing diagram of the midpoint clamp inverter can be as described above. Figure 9 As shown, the converter circuit diagram of the midpoint clamp inverter can be as described above. Figures 10-11 As shown. For more details on the operations performed by the midpoint clamp inverter provided in this application, please refer to [link / reference]. Figures 2 to 11 The implementation method of the midpoint clamp inverter shown in the diagram and its working principle will not be elaborated here. It can be seen that the control module can adjust the control based on the junction temperature T of switch j. j The first preset delay time, the second preset delay time, the third preset delay time, and the fourth preset delay time are adjusted according to the load current i0, thereby realizing the adaptive control of the inverter according to the operating conditions, which reduces the inverter losses under all operating conditions, improves the inverter operating efficiency, and makes it more flexible and adaptable.

[0055] It should be noted that the midpoint clamping inverter provided in this application can also be applied to single-phase inverter circuits, three-level circuits, rectifier circuits, three-phase circuits, or it can also be applied to circuits based on the midpoint clamping inverter provided in this application, by using multi-level technology to increase the number of circuit levels or to realize the series and parallel connection of power devices. The specific application scenario can be determined according to the actual application scenario, and no restrictions are imposed here.

[0056] The midpoint clamping inverter provided in this application can flexibly select different switching units based on the control module to bear the switching losses or conduction losses under different operating conditions (such as outputting active power or outputting reactive power), thereby reducing the inverter's losses under all operating conditions, improving the inverter's operating efficiency, and making it more flexible and adaptable.

[0057] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A midpoint clamped inverter, characterized in that, The midpoint clamp inverter includes a power module, a switching module, and a control module; The power module includes a power supply, and a first capacitor and a second capacitor connected in series and then in parallel across the two ends of the power supply. The switching module includes a first switching unit, a second switching unit, a first switch, a first diode, and a second diode. The first connection terminal of the first switching unit is connected to the positive terminal of the power supply. The second connection terminal of the first switching unit is connected to the cathode of the first diode and the first terminal of the first switch. The third connection terminal of the first switching unit is connected to the first connection terminal of the second switching unit and the load. The second connection terminal of the second switching unit is connected to the anode of the second diode and the second terminal of the first switch. The third connection terminal of the second switching unit is connected to the negative terminal of the power supply and the load. The anode of the first diode and the cathode of the second diode are connected to the first capacitor and the second capacitor. The control module is connected to the first switch unit, the second switch unit, and the first switch, respectively. The control module is used to control the first switch unit, the second switch unit, and the first switch to be turned on or off, so as to select the first switch unit, the second switch unit, and the first switch to jointly bear the conduction loss, or to select the first switch unit or the second switch unit to bear the conduction loss and the first switch to bear the switching loss, or to select the first switch unit or the second switch unit to bear the switching loss and the first switch to bear the conduction loss.

2. The midpoint clamped inverter according to claim 1, characterized in that, The midpoint clamp inverter also includes a filtering module; The filtering module includes an inductor and a third capacitor. One end of the inductor is connected to the third connection terminal of the first switching unit and the first connection terminal of the second switching unit, respectively. The other end of the inductor is connected to one end of the third capacitor and the load, respectively. The other end of the third capacitor is connected to the second connection terminal of the second switching unit and the load.

3. The midpoint clamped inverter according to claim 1 or 2, characterized in that, The first switching unit includes a second switch and a third switch, and the second switching unit includes a fourth switch and a fifth switch. The first pole of the second switch serves as the first connection terminal of the first switching unit; the second pole of the second switch is connected to the first pole of the third switch as the second connection terminal of the first switching unit; the second pole of the third switch serves as the third connection terminal of the first switching unit; the first pole of the fourth switch serves as the first connection terminal of the second switching unit; the second pole of the fourth switch is connected to the first pole of the fifth switch as the second connection terminal of the second switching unit; and the second pole of the fifth switch serves as the third connection terminal of the second switching unit. The control module is connected to the third pole of each of the first switch, the second switch, the third switch, the fourth switch, and the fifth switch.

4. The midpoint clamped inverter according to claim 3, characterized in that, The control module is used to control the conduction or cutoff of each of the first switch, the second switch, the third switch, the fourth switch, and the fifth switch, so as to select the first switch, the third switch, and the fourth switch to bear the conduction loss based on the parallel current path, or to select the first switch to bear the switching loss and the third switch or the fourth switch to bear the conduction loss, or to select the first switch to bear the conduction loss and the third switch or the fourth switch to bear the switching loss.

5. The midpoint clamped inverter according to claim 3 or 4, characterized in that, The first switch, the second switch, the third switch, the fourth switch, or the fifth switch are insulated gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs).

6. The midpoint clamped inverter according to claim 5, characterized in that, The first switch, the second switch, the third switch, the fourth switch, or the fifth switch are made of silicon semiconductor material Si, or silicon carbide SiC, or gallium nitride GaN, a third-generation wide bandgap semiconductor material.

7. The midpoint clamped inverter according to any one of claims 3-6, characterized in that, The first switch is a MOSFET, and the second, third, fourth, and fifth switches are IGBTs. The first, second, and third terminals of the first switch are the drain, source, and gate of the first switch, respectively. The first terminal of each of the second, third, fourth, and fifth switches is the collector of the switch, the second terminal of each switch is the emitter of the switch, and the third terminal of each switch is the base of the switch.

8. The midpoint clamped inverter according to any one of claims 3-6, characterized in that, The first switch, the second switch, and the fifth switch are IGBTs, and the third switch and the fourth switch are MOSFETs; The first electrode of each of the first, second, and fifth switches is the collector of the respective switch; the second electrode of each of the switches is the emitter of the respective switch; and the third electrode of each of the switches is the base of the respective switch. The first electrode of the third and fourth switches is the drain of the respective switches; the second electrode of the third and fourth switches is the source of the respective switches; and the third electrode of the third and fourth switches is the gate of the respective switches.

9. The midpoint clamped inverter according to any one of claims 3-8, characterized in that, The control module is also used to generate control signals for controlling each of the first switch, the second switch, the third switch, the fourth switch and the fifth switch, the control signals being used to control the switching on or off of each switch.

10. The midpoint clamped inverter according to claim 9, characterized in that, The control module is used for: The first switch is turned on, and the fourth switch is turned on after a first preset delay time. The first switch is turned off after a second preset delay time following the control of the fourth switch to turn off. The first switch is turned on, and the third switch is turned on after a third preset delay time. After the third switch is turned off, the first switch is turned off after a fourth preset delay time.

11. The midpoint clamped inverter according to claim 9, characterized in that, The control module is used for: The fourth switch is controlled to be turned on, and the first switch is controlled to be turned on after a first preset delay time, and the fourth switch is controlled to be turned off after a second preset delay time after the first switch is turned off. The third switch is turned on, and the first switch is turned on after a third preset delay time. The third switch is turned off after a fourth preset delay time following the first switch being turned off.

12. The midpoint clamped inverter according to claim 10 or 11, characterized in that, The control module is further configured to determine the first preset delay time, the second preset delay time, the third preset delay time, and the fourth preset delay time based on the junction temperature of the device corresponding to each of the first switch, the second switch, the third switch, the fourth switch, and the fifth switch, and / or the load current flowing through the load.

13. A photovoltaic power supply system, characterized in that, The photovoltaic power supply system includes a photovoltaic array and a midpoint clamping inverter as described in any one of claims 1-12 connected to the photovoltaic array.

Images