Control method of inverter circuit and power conversion device

Abstract

The invention provides a control method of an inverter circuit and a power conversion device. Wherein the inverter circuit comprises an inverter unit and a switch unit, the switch unit is used for conducting connection among the inverter unit, a power grid and a load, and the inverter unit is used for being connected with a photovoltaic module or energy storage equipment. The control method comprises the steps that when an output instruction is received, the switch unit is controlled to conduct connection between a power grid and a load so that the power grid can supply power to the load, then the working state of each switch tube in the inversion unit is controlled so that fault detection can be carried out on the inversion unit, and under the condition that it is determined that the inversion unit does not have a fault, demand information of the load is obtained; and the inverter unit is driven according to the output and demand information of the inverter unit, and the switch unit is controlled to conduct connection among the inverter unit, the power grid and the load. According to the control method, the use safety of the inverter circuit can be improved, and timely, reliable and stable power supply of the load can be ensured.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a control method for an inverter circuit and a power conversion device. Background Art

[0002] Some photovoltaic energy storage systems are often connected to photovoltaic equipment, energy storage equipment and the power grid through inverter circuits to meet the needs of the connected loads. In the specific use process, it is necessary to ensure timely, reliable and stable power supply to the loads. Summary of the invention

[0003] In view of this, the present application provides a control method for an inverter circuit and a power conversion device, which can improve the safety of the inverter circuit and help ensure timely, reliable and stable power supply to the load.

[0004] The first aspect of the present application provides a control method for an inverter circuit. The inverter circuit includes an inverter unit and a switch unit, the switch unit is used to respectively conduct the connection between the inverter unit, the power grid and the load, and the inverter unit is used to connect to a photovoltaic module or an energy storage device. The control method includes: when receiving an output instruction, controlling the switch unit to conduct the connection between the power grid and the load so that the power grid supplies power to the load; controlling the working state of each switch tube in the inverter unit to perform fault detection on the inverter unit; obtaining the demand information of the load when it is determined that there is no fault in the inverter unit; driving the inverter unit according to the output and demand information of the inverter unit, and controlling the switch unit to conduct the connection between the inverter unit, the power grid and the load.

[0005] In the control method of the inverter circuit of the present application, when receiving the output instruction, the switch unit is controlled to conduct the connection between the power grid and the load so that the power grid supplies power to the load, and then the working state of each switch tube in the inverter unit is controlled to detect the fault of the inverter unit, and then when it is determined that there is no fault in the inverter unit, the demand information of the load is obtained, and the inverter unit is driven and the switch unit is controlled to conduct the connection between the inverter unit, the power grid and the load according to the output and demand information of the inverter unit. That is to say, in the method of the present application, when the output instruction is received, the load is first powered by the bypass to ensure the power supply demand of the load in time, and the inverter circuit is driven only when the inverter circuit is self-checked and there is no hardware fault, so as to avoid directly starting the inverter unit with a fault to supply power to the load. Therefore, the method of the present application can improve the safety performance of the inverter circuit, avoid the generation of circuit safety risks and avoid load power failure, and ensure timely, reliable and stable power supply to the load.

[0006] In one embodiment, the inverter unit includes a first bridge arm, a second bridge arm, a freewheeling bridge arm and an output capacitor, the first bridge arm and the second bridge arm are both connected to a DC bus, the midpoint of the first bridge arm and the midpoint of the second bridge arm serve as output ends of the inverter unit and are connected to a switch unit, the output capacitor and the freewheeling bridge arm are connected in parallel between the midpoint of the first bridge arm and the midpoint of the second bridge arm, and the first bridge arm, the second bridge arm and the freewheeling bridge arm are all provided with a switch tube; the working state of each switch tube in the inverter unit is controlled to perform fault detection on the inverter unit, including: obtaining the capacitor voltage of the output capacitor and the bus voltage of the DC bus; when the capacitor voltage is less than or equal to a first preset value and the bus voltage is greater than a second preset value, controlling the target switch tubes in the first bridge arm and the second bridge arm to turn on, wherein the first preset value is less than the second preset value; after the first preset conduction time, determining the fault detection result of the inverter circuit according to the capacitor voltage.

[0007] In one embodiment, the first bridge arm includes a first upper switch tube and a first lower switch tube connected in series, and the second bridge arm includes a second upper switch tube and a second lower switch tube connected in series; controlling the target switch tubes in the first bridge arm and the second bridge arm to be turned on includes: controlling the first upper switch tube and the second lower switch tube to be turned on; or controlling the first lower switch tube and the second upper switch tube to be turned on.

[0008] In one embodiment, after a first preset conduction time, a fault detection result of the inverter circuit is determined based on the capacitor voltage, including: after the first preset conduction time, if the capacitor voltage is greater than a first preset value, the switch tube in the freewheeling bridge arm is controlled to be turned on; after a second preset conduction time, if the capacitor voltage is greater than the first preset value, it is confirmed that there is a fault in the freewheeling bridge arm.

[0009] In one embodiment, the freewheeling bridge arm includes a first freewheeling switch tube and a second freewheeling switch tube connected in reverse series; after a first preset conduction time, the fault detection result of the inverter circuit is determined according to the capacitor voltage, including: after controlling the first upper switch tube and the second lower switch tube to be turned on for the first preset conduction time, if the capacitor voltage is of the first polarity, then controlling the second freewheeling switch tube to be turned on; after controlling the second freewheeling switch tube to be turned on for the second preset conduction time, if the capacitor voltage is still of the first polarity, then confirming that the second freewheeling switch tube has a fault; or, after controlling the first lower switch tube and the second upper switch tube to be turned on for the first preset conduction time, if the capacitor voltage is of the second polarity, then controlling the first freewheeling switch tube to be turned on; after controlling the first freewheeling switch tube to be turned on for the second preset conduction time, if the capacitor voltage is still of the second polarity, then confirming that the first freewheeling switch tube has a fault; wherein the first polarity and the second polarity are opposite.

[0010] In one embodiment, after obtaining the capacitor voltage of the output capacitor and the bus voltage of the DC bus, the control method also includes: when the capacitor voltage is greater than a first preset value, controlling the switch tube in the freewheeling bridge arm to turn on; if after a third preset conduction time, the capacitor voltage is still greater than the first preset value, it is confirmed that there is a fault in the freewheeling bridge arm.

[0011] In one embodiment, the inverter circuit also includes a pre-charging unit, a first end of the pre-charging unit is connected to the power grid, and a second end of the pre-charging unit is connected to the DC bus; after obtaining the capacitor voltage of the output capacitor and the bus voltage of the DC bus, the control method also includes: when the bus voltage is less than or equal to a second preset value, controlling the pre-charging unit to charge the DC bus; if after a preset charging time, the bus voltage of the DC bus is still less than or equal to the second preset value, it is confirmed that there is a fault in the pre-charging unit or the inverter unit.

[0012] In one embodiment, the inverter unit is driven according to the output of the inverter unit and demand information, and the switch unit is controlled to conduct the connection between the inverter unit, the power grid and the load, including: driving the inverter unit according to the demand information, and when the output of the inverter unit meets the demand information, controlling the switch unit to conduct the connection between the inverter unit and the load, and disconnecting the connection between the power grid and the load.

[0013] In one embodiment, the switch unit includes an off-grid switch, a grid-connected switch and a bypass switch; when the output of the inverter unit meets the demand information, the switch unit is controlled to connect the inverter unit and the load, and disconnect the grid and the load, including: obtaining the voltage information of the grid; obtaining the closing time required for the off-grid switch between the inverter unit and the load to close, and the disconnection time required for the bypass switch between the grid and the load to disconnect; determining the output parameters of the inverter unit according to the voltage information and the demand information, the output parameters including the inverter voltage and the inverter current; obtaining the zero-crossing point information of the grid; issuing a closing instruction to the off-grid switch in advance according to the zero-crossing point information and the closing time, and issuing a disconnection instruction to the bypass switch in advance according to the zero-crossing point information and the disconnection time, the closing instruction is used to drive the off-grid switch to complete the closing when the grid crosses the zero point, and the disconnection instruction is used to drive the bypass switch to disconnect when the grid crosses the zero point; when the grid crosses the zero point, the inverter unit is driven according to the output parameters.

[0014] A second aspect of the present application provides a power conversion device, including an inverter circuit and a controller, wherein the inverter circuit includes an inverter unit and a switch unit, the switch unit is used to respectively conduct the connection between the inverter unit, the power grid and the load, and the inverter unit is used to connect to a photovoltaic component or an energy storage device; the controller is used to execute the control method of the inverter circuit described in the first aspect or any one of the embodiments of the first aspect.

[0015] A third aspect of the present application provides an energy storage system, comprising an inverter circuit, an energy storage device and a controller, wherein the inverter circuit comprises an inverter unit and a switch unit, the inverter unit is connected to the energy storage device, and the switch unit is used to respectively conduct the connection between the inverter unit, the power grid and the load; the controller is used to execute the control method of the inverter circuit described in the first aspect or any one of the embodiments of the first aspect.

[0016] The fourth aspect of the present application provides an electronic device, including a processor and a memory, the memory is used to store programs, instructions or codes, and the processor is used to execute the programs, instructions or codes in the memory to complete the control method of the inverter circuit described in the first aspect or any one of the embodiments of the first aspect.

[0017] In a fifth aspect, the present application provides a control device for an inverter circuit, wherein the inverter circuit includes an inverter unit and a switch unit, the switch unit is used to respectively conduct the connection between the inverter unit, the power grid and the load, and the inverter unit is used to connect to a photovoltaic module or an energy storage device; the control device includes a first control module, a fault detection module, an acquisition module and a second control module, the first control module is used to control the switch unit to conduct the connection between the power grid and the load when receiving an output instruction, so that the power grid supplies power to the load; the fault detection module is used to control the working state of each switch tube in the inverter unit to perform fault detection on the inverter unit; the acquisition module is used to obtain the load demand information when it is determined that there is no fault in the inverter unit; the second control module is used to drive the inverter unit according to the demand information and the output of the inverter unit, and control the switch unit to conduct the connection between the inverter unit, the power grid and the load.

[0018] A sixth aspect of the present application provides a computer-readable storage medium storing a computer program, which is loaded by a processor to execute the control method of the inverter circuit described in the first aspect or any one of the embodiments of the first aspect.

[0019] In addition, the technical effects brought about by any embodiment of the second to sixth aspects can refer to the technical effects brought about by different embodiments of the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is an application schematic diagram of a control method for an inverter circuit provided in an embodiment of the present application.

[0021] Figure 2 yes Figure 1 A circuit diagram of an inverter circuit in FIG.

[0022] Figure 3 This is another application schematic diagram of the control method of the inverter circuit provided in one embodiment of the present application.

[0023] Figure 4 It is a flow chart of a control method of an inverter circuit provided in one embodiment of the present application.

[0024] Figure 5 yes Figure 4 A detailed flowchart of step S12 in FIG.

[0025] Figure 6 yes Figure 4 Another detailed flowchart of step S12 in FIG.

[0026] Figure 7 yes Figure 4 A detailed flowchart of step S14 in FIG.

[0027] Figure 8 It is a schematic diagram of a power conversion device provided in one embodiment of the present application.

[0028] Fig. 9 It is a schematic diagram of an energy storage system provided in one embodiment of the present application.

[0029] Fig.10 This is a schematic diagram of an electronic device provided by an embodiment of the present application.

[0030] Fig.11 It is a schematic diagram of a control device for an inverter circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0031] It should be noted that the terms "first" and "second" in the specification, claims and drawings of the present application are used to distinguish similar objects rather than to describe a specific order or sequence.

[0032] It should also be noted that the method disclosed in the embodiments of the present application or the method shown in the flowchart includes one or more steps for implementing the method. Without departing from the scope of the claims, the execution order of multiple steps can be interchangeable with each other, and some of the steps can also be deleted.

[0033] Some embodiments will be described below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0034] Some photovoltaic energy storage systems are often connected to photovoltaic equipment, energy storage equipment and the power grid through inverter circuits to meet the needs of the connected loads. In the specific use process, it is necessary to ensure timely, reliable and stable power supply to the loads.

[0035] To this end, an embodiment of the present application provides a control method for an inverter circuit, which can ensure that the inverter circuit is used without hardware failure, improve the safety of use of the inverter circuit, and help ensure timely, reliable and stable power supply to the load.

[0036] See also Figure 1 , shows an application scenario of the control method of the inverter circuit provided in the embodiment of the present application. This scenario includes an inverter circuit 100, an energy storage device 200, a photovoltaic module 300, a load 400 and a power grid 500.

[0037] The inverter circuit 100 includes an inverter unit 10 and a switch unit 20. The input end of the inverter unit 10, the energy storage device 200, and the photovoltaic module 300 are respectively connected to the DC bus (BUS+, BUS-). The output end of the inverter unit 10 is connected to the connection terminals (l, n) of the load 400 and the phase line L and the neutral line N of the power grid 500 through the switch unit 20, and the connection terminal n of the load 400 can also be connected to the protective earth (protecting earthing, PE). The switch unit 20 is used to conduct the connection between the inverter unit 10, the power grid 500 and the load 400.

[0038] Specifically, the photovoltaic module 300 can be used to convert solar energy into direct current and then output it to the inverter unit 10, and the switch unit 20 can be used to conduct the connection between the inverter unit 10 and the load 400. Then, the inverter unit 10 can convert direct current into alternating current and then output it to the load 400, so that the load 400 can be powered on and work. Among them, when the output power of the photovoltaic module 300 is greater than the required power of the load 400, a part of the output power of the photovoltaic module 300 is supplied to the load 400, and the other part of the power can charge the energy storage device 200. When the output power of the photovoltaic module 300 is less than the required power of the load 400, the energy storage device 200 discharges to supplement the load 400, so that self-generation and self-use can be achieved, and the load 400 does not need to take electricity from the power grid 500. Of course, the switch unit 20 can also be used to conduct the connection between the load 400 and the power grid 500. When the energy storage device 200 cannot supplement the load 400, the power grid 500 can also supply power to the load 400 together.

[0039] Among them, the inverter circuit 100 can be in a grid-connected operation state or an off-grid operation state according to actual conditions. For example, when the inverter circuit 100 operates normally and there is no hardware failure, if the power grid 500 operates normally, the switch unit 20 can be used to conduct the connection between the inverter unit 10 and the power grid 500, and the inverter unit 10 can be in a grid-connected operation state. At this time, if the photovoltaic component 300 has excess power in addition to supplying output power to the load 400, or to the load 400 and the energy storage device 200, the excess output power can be fed into the power grid 500 through the inverter circuit 100. For another example, if the power grid 500 loses power or the power supply is unstable, the switch unit 20 can be used to disconnect the connection between the inverter unit 10 and the power grid 500, and the inverter unit 10 can be in an off-grid operation state.

[0040] In the embodiment of the present application, the inverter unit 10 includes a plurality of switch tubes, and the DC to AC conversion function can be realized by switching the plurality of switch tubes on and off. Among them, the plurality of switch tubes can be connected to form at least two inverter bridge arms and a freewheeling bridge arm, and these bridge arms can form a corresponding topological structure. Figure 2 The Heric (Highly Efficient Reliable Inverter Concept) topology shown is used as an example for explanation.

[0041] Please also read Figure 2 The inverter unit 10 includes a first bridge arm 11, a second bridge arm 12, a freewheeling bridge arm 13 and an output capacitor C2. Both ends of the first bridge arm 11 and both ends of the second bridge arm 12 serve as input ends of the inverter unit 10 and are connected to the DC bus BUS+ and BUS-, respectively. The midpoint a of the first bridge arm 11 and the midpoint b of the second bridge arm 12 serve as output ends of the inverter unit 10 and are connected to the switch unit 20. The freewheeling bridge arm 13 and the output capacitor C2 are connected in parallel between the midpoint a of the first bridge arm 11 and the midpoint b of the second bridge arm 12. The output capacitor C2 can play the role of output filtering and energy storage.

[0042] The first bridge arm 11, the second bridge arm 12 and the freewheeling bridge arm 13 are all provided with switch tubes. Each switch tube can adopt a corresponding semiconductor switch according to actual conditions, such as a metal oxide semiconductor field effect transistor (metal-oxide-semiconductor field-effect transistor, MOSFET), an insulated gate bipolar transistor (insulatedgate bipolar transistor, IGBT) or a gallium nitride high electron mobility transistor (GaN HEMT), etc. For the convenience of description, the embodiment of the present application is shown as an example in which each switch tube is a MOSFET.

[0043] Specifically, the first bridge arm 11 includes a first upper switch tube Q1 and a first lower switch tube Q2 connected in series, the first end of the first upper switch tube Q1 and the second end of the first lower switch tube Q2 serve as the two ends of the first bridge arm 11, and the connection point between the second end of the first upper switch tube Q1 and the first end of the first lower switch tube Q2 is the midpoint a of the first bridge arm 11. The second bridge arm 12 includes a second upper switch tube Q3 and a second lower switch tube Q4 connected in series, the first end of the second upper switch tube Q3 and the second end of the second lower switch tube Q4 serve as the two ends of the second bridge arm 12, and the connection point between the second end of the second upper switch tube Q3 and the first end of the second lower switch tube Q4 is the midpoint b of the second bridge arm 12. The freewheeling bridge arm 13 includes a first freewheeling switch tube Q5 and a second freewheeling switch tube Q6 which are connected in reverse series, wherein the second end of the first freewheeling switch tube Q5 is connected to the midpoint a of the first bridge arm 11, the first end of the first freewheeling switch tube Q5 is connected to the first end of the second freewheeling switch tube Q6, and the second end of the second freewheeling switch tube Q6 is connected to the midpoint b of the second bridge arm 12.

[0044] like Figure 2 As shown, the inverter unit 10 may further include at least one of a first output inductor L1 and a second output inductor L2. The first output inductor L1 may be connected between the midpoint a of the first bridge arm 11 and the power grid 500, and the second output inductor L2 may be connected between the midpoint b of the second bridge arm 12 and the power grid 500, which may play the role of output filtering and energy storage. In addition, a DC bus capacitor C1 is also connected between the DC bus BUS+ and BUS-, which may play the role of input filtering and energy storage.

[0045] It can be understood that the first bridge arm 11 and the second bridge arm 12 are both inverter bridge arms, and can together constitute an inverter full-bridge circuit. In the positive half cycle of the alternating current, the first upper switch tube Q1 and the second lower switch tube Q4 are synchronously switched on and off at high frequency, the second freewheeling switch tube Q6 remains on, and the first freewheeling switch tube Q5 is complementary to the first upper switch tube Q1 and the second lower switch tube Q4. When the first upper switch tube Q1 and the second lower switch tube Q4 are both disconnected and the first freewheeling switch tube Q5 is turned on, the first freewheeling switch tube Q5 and the second freewheeling switch tube Q6 can be connected to form a freewheeling branch. In the negative half cycle of the alternating current, the second upper switch tube Q3 and the first lower switch tube Q2 are synchronously switched on and off at high frequency, the first freewheeling switch tube Q5 remains on, and the second freewheeling switch tube Q6 is complementary to the second upper switch tube Q3 and the first lower switch tube Q2. When the second upper switch tube Q3 and the first lower switch tube Q2 are both turned off and the second freewheeling switch tube Q6 is turned on, the second freewheeling switch tube Q6 and the first freewheeling switch tube Q5 can be connected to form a freewheeling branch. The voltage of the freewheeling branch is shared by the first freewheeling switch tube Q5 and the second freewheeling switch tube Q6, so the stress of each switch tube is small, and the load 400 can be isolated from the inverter full-bridge circuit.

[0046] It should be understood that the topology and control logic of the inverter unit 10 described above are merely illustrative examples provided in this application, and may be adjusted accordingly according to actual conditions, and are not limited to the implementation methods mentioned in this application.

[0047] In the embodiment of the present application, the switch unit 20 may include an off-grid switch 21, a grid-connected switch 22, and a bypass switch 23. The off-grid switch 21, the grid-connected switch 22, and the bypass switch 23 are all normally open switches. The off-grid switch 21, the grid-connected switch 22, and the bypass switch 23 may all adopt corresponding types of switch elements according to actual conditions, for example, at least one of a mechanical switch and a semiconductor switch may be adopted, wherein the mechanical switch includes but is not limited to a relay, a contactor, etc., and the semiconductor switch includes but is not limited to a triode, a MOSFET, an IGBT, etc.

[0048] Specifically, the off-grid switch 21 is connected between the output end of the inverter unit 10 and the load 400. The off-grid switch 21 can be used to conduct the connection between the inverter unit 10 and the load 400. Specifically, once the off-grid switch 21 is turned on, the inverter unit 10 and the load 400 are connected. Conversely, once the off-grid switch 21 is turned off, the inverter unit 10 and the load 400 are disconnected.

[0049] The grid-connected switch 22 is connected between the output end of the inverter unit 10 and the power grid 500. The grid-connected switch 22 can be used to conduct the connection between the inverter unit 10 and the power grid 500. Specifically, once the grid-connected switch 22 is turned on, the inverter unit 10 and the power grid 500 are connected. Then, the inverter unit 10 can be operated in grid connection. On the contrary, once the grid-connected switch 22 is turned off, the connection between the inverter unit 10 and the power grid 500 is disconnected. Then, the inverter unit 10 can be operated off-grid.

[0050] The bypass switch 23 is connected between the power grid 500 and the load 400. The bypass switch 23 can be used to conduct the connection between the power grid 500 and the load 400. Specifically, once the bypass switch 23 is turned on, the power grid 500 and the load 400 are connected. On the contrary, once the bypass switch 23 is turned off, the power grid 500 and the load 400 are disconnected.

[0051] In one embodiment, the off-grid switch 21, the grid-connected switch 22 and the bypass switch 23 may each include at least two groups of switch elements to prevent the failure of the circuit breaker function due to adhesion of one group of switch elements. Figure 1The off-grid switch 21 includes switch elements K1, K1', K2, K2', K1 and K2 form a group of switch elements, and K1' and K2' form another group of switch elements. The grid-connected switch 22 includes switch elements K3, K3', K4, K4', K3 and K4 form a group of switch elements, and K3' and K4' form another group of switch elements. The bypass switch 23 includes switch elements K5, K5', K6, K6', K5 and K6 form a group of switch elements, and K5' and K6' form another group of switch elements. Switch elements of different groups can be controlled independently.

[0052] In the embodiment of the present application, the energy storage device 200 includes a rechargeable energy storage battery. The photovoltaic assembly 300 may include a photovoltaic panel, or may include a plurality of photovoltaic panels connected in series, in parallel, or in series and in parallel, which is not limited here. In some embodiments, in order to improve the photovoltaic utilization rate, a maximum power point tracking (MPPT) circuit ( Figure 1 The MPPT circuit can be used to achieve maximum power tracking of the photovoltaic assembly 300, so that the inverter unit 10 is connected to the maximum output power of the photovoltaic assembly 300. The power grid 500 can be, for example, a microgrid, a municipal power grid or other local power grids. The load 400 can be, for example, various AC loads in a home.

[0053] In the embodiments of the present application, Figure 1 Scenes can also include controllers ( Figure 1 ). The controller may adopt a microcontroller unit (MCU) or other control circuit, and may be independently arranged or integrated into the energy storage device 200 or the inverter circuit 100, which is not limited here. The controller may be used as an energy management system (EMS). The controller is connected to the control end of each switch tube in the inverter unit 10 and each switch element in the switch unit 20. The controller may be used to execute the control method of the inverter circuit provided in the embodiment of the present application to control the inverter circuit 100 to ensure timely, reliable and stable power supply to the load 400. In some embodiments, the controller may also be connected to the energy storage device 200 and used to control the charging and discharging of the energy storage device 200. The controller may also be connected to the device end or the APP end in communication, so as to receive instructions sent by the device end or the APP end and feedback information to the device end or the APP end. Among them, the device end may be, for example, a terminal device such as a mobile phone, a tablet, a remote control, a computer or an industrial control computer.

[0054] It should be noted that the application scenarios of the methods described above are only illustrative examples provided by this application, and can be adjusted accordingly according to actual conditions, all within the scope of protection of this application. For example, the scenario may include more or fewer parts than shown in the figure (such as providing an MPPT circuit, or omitting at least one of the photovoltaic module 300 and the energy storage device 200). The inverter circuit 100 may also include more components than shown in the figure, or combine certain components, or split certain components, or arrange the components differently. For example, refer to Figure 3 In addition to the inverter unit 10 and the switch unit 20, the inverter circuit 100 may also include a pre-charging unit 30. The pre-charging unit 30 may be any circuit that can realize the pre-charging function, and it may draw power from the power grid 500 or other power sources. The pre-charging unit 30 may be connected to the DC bus to pre-charge the DC bus capacitor C1, which may reduce the current impact between the inverter unit 10 and the energy storage device 200 / photovoltaic module 300, and may also provide a certain input for the inverter unit 10.

[0055] Next, the control method of the inverter circuit provided in the embodiment of the present application is introduced.

[0056] See also Figure 4 , the control method of the inverter circuit includes:

[0057] Step S11: upon receiving the output instruction, controlling the switch unit to conduct the connection between the grid and the load, so that the grid supplies power to the load.

[0058] In step S11 , the controller may receive an output instruction from the device end or the APP end, where the output instruction is used to instruct the inverter circuit 100 to output power to the load 400 .

[0059] It can be understood that the inverter unit 10 is not started at this time. This is mainly because the inverter unit 10 requires a certain amount of startup time, and after startup, it cannot immediately output the power required by the load 400. Therefore, in order to ensure timely and stable power supply to the load 400, the power grid 500 provides power to the load 400 at this time. Therefore, the controller can control the bypass switch 23 in the inverter circuit 100 to conduct the connection between the grid 500 and the load 400, and the conducted bypass switch 23 can transmit the power of the grid 500 to the load 400.

[0060] Since the inverter unit 10 does not supply power to the load 400 at this time, the off-grid switch 21 in the switch unit 20 is in a normally open state at this time, that is, there is no conduction between the inverter unit 10 and the load 400. In order to prevent the current of the power grid 500 from impacting the inverter unit 10, the grid-connected switch 22 in the switch unit 20 is in a normally open state at this time, that is, there is no conduction between the inverter unit 10 and the power grid 500.

[0061] Step S12: Control the working state of each switch tube in the inverter unit to perform fault detection on the inverter unit.

[0062] It can be understood that when the inverter unit 10 operates normally, the inverter unit 10 can switch the working state of each switch tube (i.e., on or off) so that the inverter unit 10 generates an expected electrical signal. When there is a fault in the inverter unit 10, the inverter unit 10 cannot normally control the faulty switch tube, and the working state of the faulty switch tube is abnormal, resulting in the failure of the inverter unit 10 to generate an expected electrical signal, which will affect the functions of the front and rear circuits and even cause a bombing accident. Therefore, in order to ensure the normal operation and safety of the circuit, it is necessary to perform fault detection on the inverter unit 10 through step S12, and put the inverter unit 10 into use when there is no fault.

[0063] Step S13: when it is determined that there is no fault in the inverter unit, obtain load demand information.

[0064] In step S13, the demand information of the load 400 may be pre-stored in the internal memory of the controller or in an external memory, and the controller may obtain the demand information of the load 400 from the memory. Alternatively, the controller may also communicate with the device end or the APP end to obtain the demand information of the load 400. Alternatively, the controller may also directly interact with the load 400 to obtain the demand information of the load 400.

[0065] The demand information of the load 400 refers to an electrical signal required for the normal operation of the load 400, such as at least one of the required voltage, required current, and required power of the load 400. In one embodiment, the demand information may be a rated working electrical signal of the load 400, so the required voltage of the load 400 may be the rated voltage of the load 400, the required current of the load 400 may be the rated current of the load 400, and the required power of the load 400 may be the rated power of the load 400.

[0066] Step S14: driving the inverter unit according to the output and demand information of the inverter unit, and controlling the switch unit to conduct the connection between the inverter unit, the power grid and the load.

[0067] In one embodiment, the output of the inverter unit 10 may refer to the rated output of the inverter unit 10 .

[0068] For example, it is assumed that the power demand of the load 400 is 1600W, and the rated output power of the inverter unit 10 is 2000W. Since the rated output power of the inverter unit 10 of 2000W is greater than the power demand of the load 400 of 1600W, the inverter unit 10 at this time is sufficient to meet the demand of the load 400, and there is no need to use the power grid 500. Therefore, in step S14, the inverter unit 10 can be driven to output 1600W of power according to the power demand of the load 400 and the rated output power of the inverter unit 10, and at the same time, the off-grid switch 21 is controlled to conduct the connection between the inverter unit 10 and the load 400, and the bypass switch 23 is controlled to disconnect the connection between the power grid 500 and the load 400, so that the inverter unit 10 provides 1600W of power to the load 400. The on and off of the grid-connected switch 22 can be controlled accordingly according to the actual situation, that is, the inverter unit 10 can be grid-connected or off-grid, which is not limited here.

[0069] As a further example, when the photovoltaic component 300 has sufficient energy, in step S14, the inverter unit 10 can also be driven to output 2000W of power according to the required power of the load 400 and the rated output power of the inverter unit 10, and the off-grid switch 21 can be controlled to turn on the connection between the inverter unit 10 and the load 400, and the grid-connected switch 22 can be controlled to turn on the connection between the inverter unit 10 and the power grid 500, and the bypass switch 23 can be controlled to disconnect the connection between the power grid 500 and the load 400, so that the inverter unit 10 provides 1600W of power to the load 400 while the inverter unit 10 can also be connected to the grid to feed 400W of power into the power grid 500.

[0070] For another example, assume that the power demand of the load 400 is 1600W, and the rated output power of the inverter unit 10 is 1500W. Since the rated output power of the inverter unit 10 of 1500W is less than the power demand of the load 400 of 1600W, the power grid 500 needs to output 100W of power to supplement the power demand of the load 400. Therefore, in step S14, the inverter unit 10 can be driven to output 1500W of power according to the power demand of the load 400 and the rated output power of the inverter unit 10, and the off-grid switch 21 can be controlled to conduct the connection between the inverter unit 10 and the load 400, and the bypass switch 23 can be controlled to conduct the connection between the power grid 500 and the load 400, so that the load 400 obtains the 1600W power provided by the inverter unit 10 and the power grid 500. The on and off of the grid-connected switch 22 can be controlled accordingly according to the actual situation, which is not limited here.

[0071] In another embodiment, the output of the inverter unit 10 may also include a rated output and an actual output of the inverter unit 10 .

[0072] For example, assuming that the power demand of the load 400 is 1600W, the rated output power of the inverter unit 10 is 2000W, but the photovoltaic module 300 and the energy storage device 200 can only provide 1000W of power for the inverter unit 10. At this time, the inverter unit 10 can only output 1000W of power, and the power grid 500 needs to supplement 600W of power. Therefore, in step S14, the inverter unit 10 can be driven to output 1000W of power, the off-grid switch 21 is controlled to conduct the connection between the inverter unit 10 and the load 400, and the bypass switch 23 is controlled to conduct the connection between the power grid 500 and the load 400, so that the load 400 obtains the 1600W power provided by the inverter unit 10 and the power grid 500. The on and off of the grid-connected switch 22 can be controlled accordingly according to actual conditions, and is not limited here.

[0073] In general, in the control method of the inverter circuit provided in the embodiment of the present application, by controlling the switch unit 20 to conduct the connection between the power grid 500 and the load 400 when receiving the output instruction, it is ensured that the load 400 can obtain fast and timely power supply even when the inverter unit 10 is not put into use, and then controlling the working state of each switch tube in the inverter unit 10 to detect the fault of the inverter unit 10. When it is determined that the inverter unit 10 does not have a fault, the inverter unit 10 is driven according to the demand information of the load 400 and the output of the inverter unit 10, and the switch unit 20 is controlled to conduct the connection between the inverter unit 10, the power grid 500 and the load 400, so that the inverter unit 10 supplies power to the load 400. That is to say, in the method of the embodiment of the present application, when receiving the output instruction, the load is first powered by the bypass to ensure the power supply demand of the load in time, and the inverter circuit is driven only when the inverter circuit is self-checked and there is no hardware fault, thereby avoiding directly starting the inverter unit with a fault to power the load. Therefore, the method of the embodiment of the present application can improve the safety performance of the inverter circuit, avoid circuit safety risks and avoid load power outages, and ensure timely, reliable and stable power supply to the load.

[0074] In the embodiment of the present application, the switch tube in the inverter unit 10 is connected to the output capacitor C2, for example Figure 2 In the Heric inverter unit 10 shown, the switch tubes Q1 to Q6 are all connected to the output capacitor C2, and the capacitor voltage of the output capacitor C2 is equivalent to the output voltage of the inverter unit 10. Therefore, if there is a fault in the inverter unit 10, the capacitor voltage of the output capacitor C2 will be abnormal. It can be seen that the fault detection of the inverter unit 10 can be achieved by detecting the capacitor voltage of the output capacitor C2. The bus voltage on the DC bus is used as the input voltage of the inverter unit 10, and the bus voltage also affects the capacitor voltage of the output capacitor C2. Therefore, in step S12, it can be confirmed whether the inverter unit 10 has a fault based on the capacitor voltage of the output capacitor C2 and the bus voltage of the DC bus.

[0075] Specifically, see Figure 5 The process of controlling the working state of each switch tube in the inverter unit in step S12 to perform fault detection on the inverter unit may include:

[0076] Step S21: obtaining the capacitor voltage of the output capacitor and the bus voltage of the DC bus.

[0077] In step S21, the controller can detect the capacitor voltage across the output capacitor C2 and the bus voltage on the DC bus respectively through different voltage detection circuits. In one embodiment, a DC bus capacitor C1 is provided on the DC bus, so the bus voltage of the DC bus is also equivalent to the capacitor voltage across the DC bus capacitor C1. Therefore, the controller can also detect the capacitor voltage across the DC bus capacitor C1 through the voltage detection circuit to obtain the bus voltage. Among them, the voltage detection circuit can be integrated into the controller or can be independently set, which is not limited here.

[0078] Step S22: confirm whether the capacitor voltage is less than or equal to a first preset value.

[0079] It is understood that here the absolute value of the capacitor voltage is compared with the first preset value, wherein the first preset value can be set accordingly according to actual conditions, for example, it can be 0V, 10V or other voltage values ​​or voltage ranges lower than 10V, etc., which are not specifically limited here.

[0080] Step S23: confirm whether the bus voltage is greater than a second preset value.

[0081] It can be understood that here the absolute value of the bus voltage is compared with the second preset value, wherein the second preset value is greater than the first preset value, and the size of the second preset value can be set accordingly according to actual conditions, for example, it can be a voltage value or voltage range greater than 10V, which is not specifically limited here.

[0082] Step S22 and step S23 may be performed simultaneously, or step S22 may be performed first and then step S23, or step S23 may be performed first and then step S22, which is not limited here.

[0083] Step S24: when the capacitor voltage is less than or equal to the first preset value and the bus voltage is greater than the second preset value, control the target switch tubes in the first bridge arm and the second bridge arm to be turned on.

[0084] In the embodiment of the present application, the target switch tube may be part of the switch tubes in the first bridge arm 11 and part of the switch tubes in the second bridge arm 12, for example, the first upper switch tube Q1 in the first bridge arm 11 and the second lower switch tube Q4 in the second bridge arm 12, or the first lower switch tube Q2 in the first bridge arm 11 and the second upper switch tube Q3 in the second bridge arm 12. It can be understood that when the inverter unit 10 is fault-free, when the target switch tube is turned on, the energy of the DC bus can be transferred from the input end to the output end of the inverter unit 10. In other words, the target switch tube is a switch tube that can cause energy transfer in the inverter unit 10 under normal circumstances.

[0085] In step S24, the controller may send a pulse signal (i.e., a high-level signal) to the control terminal of the target switch tube to control the target switch tube to be turned on. The width of the pulse signal may be determined according to actual conditions, for example, it may be a narrow pulse at the microsecond level. Moreover, the controller may continue to send the pulse signal to control the target switch tube to be continuously turned on.

[0086] Step S25: after the first preset conduction time, determining the fault detection result of the inverter circuit according to the capacitor voltage.

[0087] In the embodiment of the present application, the controller stops sending pulse signals when the duration of continuously sending pulse signals to the target switch reaches the first preset conduction duration. The first preset conduction duration can be set accordingly according to actual conditions, for example, it can be 10 milliseconds, which is not specifically limited here.

[0088] It can be understood that when there is no fault in the inverter circuit 100, in step S24, the target switch tube can be controlled to be in the on state, and the other switch tubes in the first bridge arm 11 and the second bridge arm 12 and the switch tube of the freewheeling bridge arm 13 are all in the off state. The DC bus can be connected to the output capacitor C2 through the target switch tube, so that the DC bus can transmit power to the output capacitor C2. Therefore, after the first preset on-time, the voltage of the output capacitor C2 can change accordingly.

[0089] In the case where the inverter circuit 100 has a fault, it may be that at least one switch has a hardware failure. Hardware failure includes short circuit failure or open circuit failure. For example, the target switch may fail to turn on, or other switches in the first bridge arm 11 and the second bridge arm 12 and the switch in the freewheeling bridge arm 13 may be abnormally turned on or short-circuited, resulting in abnormal power transmission. For further example, assuming Figure 2The first upper switch tube Q1 and the second lower switch tube Q4 in the circuit are target switch tubes. If the first upper switch tube Q1 is abnormally disconnected, the circuit between the DC bus and the output capacitor C2 will be broken, resulting in the inability to transmit power to the output capacitor C2. If the first lower switch tube Q2 is abnormally turned on, a direct short circuit will occur between the first upper switch tube Q1 and the first lower switch tube Q2, resulting in the inability to transmit power to the output capacitor C2. If the first freewheeling switch tube Q5 is abnormally turned on, the body diodes of the first upper switch tube Q1, the first freewheeling switch tube Q5 and the second freewheeling switch tube Q6 will be connected, resulting in the inability to transmit power to the output capacitor C2. Therefore, after the first preset conduction time, the output capacitor C2 cannot have a corresponding voltage change.

[0090] Therefore, after the first preset conduction time, it can be determined whether the inverter circuit 100 has a fault based on the change in the capacitor voltage.

[0091] It can be understood that, since different switch tubes can be used as target switch tubes, in the embodiment of the present application, steps S21 to S25 can be performed multiple times to comprehensively check the fault condition of the inverter unit 10.

[0092] In summary, the embodiment of the present application can detect the hardware fault of the switch tube of the inverter circuit 100 through steps S21 to S25, which is conducive to timely discovering the fault of the inverter circuit 100 and improving the safety of the inverter circuit 100. Moreover, the method of the embodiment of the present application can confirm whether the inverter unit 10 has a fault through the switch tube on-off control logic combined with the real-time capacitor voltage and bus voltage, and does not need to add a hardware module. Therefore, the method of the embodiment of the present application is simple, easy to implement, and low in cost.

[0093] In one embodiment, please refer to Figure 6 After the first preset conduction time, the process of determining the fault detection result of the inverter circuit according to the capacitor voltage (i.e., step S25) may include:

[0094] Step S251: after a first preset conduction time, if the capacitor voltage is greater than a first preset value, the switch tube in the freewheeling bridge arm is controlled to be turned on.

[0095] It can be understood that, when the inverter unit 10 is fault-free, after the target switch tube is turned on for the first preset turn-on time, the output capacitor C2 will store the energy transmitted by the inverter unit 10, so that the capacitor voltage is increased accordingly, and the absolute value of the capacitor voltage is greater than the first preset value. On the contrary, when the inverter unit 10 fails, the energy cannot be transmitted to the output capacitor C2, resulting in that the capacitor voltage cannot be increased accordingly, and the absolute value of the capacitor voltage cannot be greater than the first preset value.

[0096] Therefore, if the capacitor voltage after the first preset conduction time is greater than the first preset value, it can be confirmed that the target switch tube has no open circuit fault and can be turned on normally. The other switch tubes in the first bridge arm 11 and the second bridge arm 12 except the target switch tube have no short circuit fault, and the freewheeling bridge arm 13 has no direct short circuit fault. On the contrary, if the capacitor voltage after the first preset conduction time is less than or equal to the first preset value, it means that at least one target switch tube has an open circuit fault, and / or at least one of the other switch tubes in the first bridge arm 11 and the second bridge arm 12 except the target switch tube has a short circuit fault, and / or the freewheeling bridge arm 13 has a direct short circuit fault.

[0097] For example, Figure 2 The first upper switch tube Q1 and the second lower switch tube Q4 in the circuit are target switch tubes. If the capacitor voltage after the first preset conduction time is greater than the first preset value, it means that the first upper switch tube Q1 and the second lower switch tube Q4 have no open circuit faults, and the first lower switch tube Q2, the second upper switch tube Q3, and the second freewheeling switch tube Q6 have no short circuit faults. On the contrary, if the capacitor voltage after the first preset conduction time is less than or equal to the first preset value, it means that there is a fault in the inverter unit 10, specifically, at least one of the first upper switch tube Q1 and the second lower switch tube Q4 has an open circuit fault, and / or at least one of the first lower switch tube Q2, the second upper switch tube Q3, and the second freewheeling switch tube Q6 has a short circuit fault.

[0098] For example, Figure 2 The first lower switch tube Q2 and the second upper switch tube Q3 in the circuit are target switch tubes. If the capacitor voltage after the first preset conduction time is greater than the first preset value, it means that the first lower switch tube Q2 and the second upper switch tube Q3 have no open circuit faults, and the first upper switch tube Q1, the second lower switch tube Q4, and the first freewheeling switch tube Q5 have no short circuit faults. On the contrary, if the capacitor voltage after the first preset conduction time is less than or equal to the first preset value, it means that there is a fault in the inverter unit 10, specifically, at least one of the first lower switch tube Q2 and the second upper switch tube Q3 has an open circuit fault, and / or at least one of the first upper switch tube Q1, the second lower switch tube Q4, and the first freewheeling switch tube Q5 has a short circuit fault.

[0099] Since it has not been determined whether the freewheeling bridge arm 13 has an open circuit fault, the freewheeling switch tube will be controlled in step S251 to detect the open circuit fault of the freewheeling bridge arm 13. Specifically, in step S251, the controller can send a pulse signal to the control end of the first freewheeling switch tube Q5 or the second freewheeling switch tube Q6 to control the first freewheeling switch tube Q5 or the second freewheeling switch tube Q6 to turn on. The pulse signal can refer to the relevant description above and will not be repeated here.

[0100] Step S252: After the second preset conduction time, if the capacitor voltage is greater than the first preset value, it is confirmed that there is a fault in the freewheeling bridge arm.

[0101] In the embodiment of the present application, the controller stops sending pulse signals to the first freewheeling switch tube Q5 or the second freewheeling switch tube Q6 when the duration of the pulse signal continuously sent reaches the second preset conduction duration. The second preset conduction duration can be set accordingly according to actual conditions and is not limited here.

[0102] It can be understood that in the case where there is no open circuit fault in the first freewheeling switch tube Q5 and the second freewheeling switch tube Q6, in step S251, the first freewheeling switch tube Q5 or the second freewheeling switch tube Q6 can be controlled to be in a conducting state, so that the conducting first freewheeling switch tube Q5 is connected to the body diode of the second freewheeling switch tube Q6, or the conducting second freewheeling switch tube Q6 is connected to the body diode of the first freewheeling switch tube Q5, so the output capacitor C2 can be connected to the freewheeling bridge arm 13 and discharge. The released electric energy can be absorbed by the first output inductor L1 and the second output inductor L2 or consumed by line resistance, parasitic impedance, etc. Therefore, after the second preset conduction time, the capacitor voltage of the output capacitor C2 will drop to be equal to or less than the first preset value. In the case where the first freewheeling switch tube Q5 and the second freewheeling switch tube Q6 have an open circuit fault, in step S251, the first freewheeling switch tube Q5 or the second freewheeling switch tube Q6 cannot be controlled to be turned on and is in a disconnected state, so the output capacitor C2 cannot be connected to the freewheeling bridge arm 13 and discharge. Therefore, after the second preset conduction time, the capacitor voltage of the output capacitor C2 cannot drop, so it is still greater than the first preset value.

[0103] Therefore, in step S251, based on the capacitor voltage after the second preset conduction time being still greater than the first preset value, it can be confirmed that there is a fault in the freewheeling bridge arm 13. Specifically, the freewheeling switch tube controlled in step S251 has an open circuit fault.

[0104] On the contrary, if the capacitor voltage after the second preset conduction time is less than or equal to the first preset value, it can be confirmed that there is no fault in the freewheeling bridge arm 13. Specifically, there is no open circuit fault in the freewheeling switch tube controlled in step S251.

[0105] It is understandable that steps S24, S251 and S252 can be performed multiple times. Each time step S24 is performed, different switch tubes in the first bridge arm 11 and the second bridge arm 12 can be used as target switch tubes. When executing step S251, different switch tubes in the freewheeling bridge arm 13 can be controlled to be turned on. Furthermore, after multiple executions of steps S24, S251 and S252, the open circuit faults and direct short circuit faults of each switch tube in the first bridge arm 11 and the second bridge arm 12 can be comprehensively checked and determined, and the short circuit faults and open circuit faults of each freewheeling switch tube in the freewheeling bridge arm 13 can be comprehensively checked and determined.

[0106] In summary, the embodiment of the present application can realize the hardware fault detection of the switch tubes of the first bridge arm 11, the second bridge arm 12 and the freewheeling bridge arm 13 through steps S24, S251 and S252. The fault detection range covers all bridge arms in the inverter unit 10, and covers open circuit faults and short circuit faults. Therefore, the fault detection can be more comprehensive and reliable.

[0107] Moreover, the embodiment of the present application can detect the fault conditions of the switching tubes of the first bridge arm 11 and the second bridge arm 12, and detect the fault conditions of the switching tubes of the freewheeling bridge arm 13 by sequentially executing steps S24, S251 and S252. There is no need to design different sets of fault detection strategies for the first and second bridge arms and the freewheeling bridge arm 13 respectively. Therefore, the fault detection method of the embodiment of the present application is efficient and simple.

[0108] For a better understanding, Figure 2 The Heric inverter unit 10 shown in FIG. Figure 2 In the embodiment, the first bridge arm 11 includes a first upper switch tube Q1 and a first lower switch tube Q2, and the second bridge arm 12 includes a second upper switch tube Q3 and a second lower switch tube Q4. When the first upper switch tube Q1 and the second lower switch tube Q4 are turned on, the energy of the DC bus can be given to the output capacitor C2 to charge the output capacitor C2, so the first upper switch tube Q1 and the second lower switch tube Q4 can be used as target switches. When the first lower switch tube Q2 and the second upper switch tube Q3 are turned on, the energy of the DC bus can also be given to the output capacitor C2 to charge the output capacitor C2, so the first lower switch tube Q2 and the second upper switch tube Q3 can also be used as target switches.

[0109] Therefore, controlling the target switch tubes in the first bridge arm and the second bridge arm to be turned on in step S24 may include:

[0110] S241A: Control the first upper switch tube and the second lower switch tube to be turned on; or,

[0111] S241B: Control the first lower switch tube and the second upper switch tube to be turned on.

[0112] In some embodiments, after controlling the first upper switch tube Q1 and the second lower switch tube Q4 to be turned on for the first preset turn-on time, determining the fault detection result of the inverter circuit 100 according to the capacitor voltage (i.e., step S25) may include:

[0113] Step 251A: After controlling the first upper switch tube and the second lower switch tube to be turned on for a first preset turn-on time, if the capacitor voltage is of the first polarity, controlling the second freewheeling switch tube to be turned on.

[0114] Step 252A: After controlling the second freewheeling switch tube to be turned on for the second preset turn-on time, if the capacitor voltage is still of the first polarity, it is confirmed that the second freewheeling switch tube is faulty.

[0115] In this embodiment, the first polarity may be a positive polarity. Figure 2 , when the first upper switch tube Q1 and the second lower switch tube Q4 are both turned on and the other switch tubes Q2, Q3, Q5, and Q6 are turned off, the current of the inverter unit 10 can flow from the midpoint a to the output capacitor C2, so that the output capacitor C2 generates a capacitor voltage of positive polarity. Therefore, in step S251A, when the capacitor voltage after the first preset turn-on time is of the first polarity, it indicates that the first upper switch tube Q1 and the second lower switch tube Q4 have no open circuit faults, and the first lower switch tube Q2, the second upper switch tube Q3, and the second freewheeling switch tube Q6 have no short circuit faults.

[0116] In this case, if the second freewheeling switch tube Q6 can be turned on normally, so that the freewheeling bridge arm 13 is turned on, the output capacitor C2 can be connected to the first output inductor L1, the freewheeling bridge arm 13 and the second output inductor L2 to form a loop. The output capacitor C2 will be equivalent to the power supply, wherein the end of the output capacitor C2 connected to the phase line L is equivalent to the positive terminal, and the end of the output capacitor C2 connected to the neutral line N is equivalent to the negative terminal. The output capacitor C2 will be discharged, and the capacitor voltage will drop after discharge. Moreover, the generated current can flow from the first output inductor L1 to the freewheeling bridge arm 13, pass through the body diode of the first freewheeling switch tube Q5, and then flow to the second freewheeling switch tube Q6, and then flow to the second output inductor L2. After the second preset conduction time, the capacitor voltage will be consumed to 0, or after dropping to 0, it will be charged by the first output inductor L1 and / or the second output inductor L2 to generate a negative polarity voltage.

[0117] If the second freewheeling switch tube Q6 cannot be turned on normally, that is, there is an open circuit fault, the output capacitor C2 cannot be discharged, and the capacitor voltage after the second preset conduction time will maintain the original positive polarity.

[0118] Therefore, in step S251A, when the capacitor voltage after the first preset conduction time is the first polarity, the second freewheeling switch tube Q6 is controlled to be turned on, and then in step S252A, when the capacitor voltage after the second preset conduction time is still the first polarity, it can be determined that the second freewheeling switch tube Q6 has an open circuit fault. On the contrary, if the capacitor voltage after the second preset conduction time is 0 or the polarity is opposite to the first polarity, it can be determined that the second freewheeling switch tube Q6 has no open circuit fault. That is to say, if after the first upper switch tube Q1 and the second lower switch tube Q4 are controlled to be turned on for the first preset conduction time, the capacitor voltage is the first polarity, and after the second freewheeling switch tube Q6 is controlled to be turned on for the second preset conduction time, the capacitor voltage is 0 or the polarity is opposite to the first polarity, it can be determined that the first upper switch tube Q1 and the second lower switch tube Q4 have no open circuit faults, the first lower switch tube Q2 and the second upper switch tube Q3 have no short circuit faults, and the second freewheeling switch tube Q6 has no short circuit faults and open circuit faults.

[0119] In addition, if after controlling the first upper switch tube Q1 and the second lower switch tube Q4 to be turned on for the first preset conduction time, the capacitor voltage is 0 or the polarity is opposite to the first polarity, it means that at least one of the first upper switch tube Q1 and the second lower switch tube Q4 has an open circuit fault, and / or at least one of the first lower switch tube Q2, the second upper switch tube Q3 and the second freewheeling switch tube Q6 has a short circuit fault.

[0120] In some embodiments, after controlling the first lower switch tube Q2 and the second upper switch tube Q3 to be turned on for the first preset turn-on time, determining the fault detection result of the inverter circuit 100 according to the capacitor voltage (i.e., step S25) may include:

[0121] Step 251B: after controlling the first lower switch tube and the second upper switch tube to be turned on for the first preset turn-on time, if the capacitor voltage is of the second polarity, controlling the first freewheeling switch tube to be turned on.

[0122] Step 252B: After controlling the first freewheeling switch to be turned on for the second preset turn-on time, if the capacitor voltage is still of the second polarity, it is determined that the first freewheeling switch is faulty, wherein the first polarity is opposite to the second polarity.

[0123] In this embodiment, the second polarity may be a negative polarity. Figure 2, when the first lower switch tube Q2 and the second upper switch tube Q3 are both turned on and the other switch tubes Q1, Q4, Q5, and Q6 are turned off, the current of the inverter unit 10 can flow from the midpoint b to the output capacitor C2, so that the output capacitor C2 generates a capacitor voltage of negative polarity. Therefore, in step S251B, when the capacitor voltage after the first preset turn-on time is of the second polarity, it indicates that the first lower switch tube Q2 and the second upper switch tube Q3 have no open circuit faults, and the first upper switch tube Q1, the second lower switch tube Q4, and the first freewheeling switch tube Q5 have no short circuit faults.

[0124] In this case, if the first freewheeling switch tube Q5 can be turned on normally, so that the freewheeling bridge arm 13 is turned on, the output capacitor C2 can be connected to the first output inductor L1, the freewheeling bridge arm 13 and the second output inductor L2 to form a loop. The output capacitor C2 will be equivalent to the power supply, wherein the end of the output capacitor C2 connected to the neutral line N is equivalent to the positive terminal, and the end of the output capacitor C2 connected to the phase line L is equivalent to the negative terminal. The output capacitor C2 will be discharged, and the capacitor voltage will drop after discharge. Moreover, the generated current can flow from the second output inductor L2 to the freewheeling bridge arm 13, and then flow to the first freewheeling switch tube Q5 after passing through the body diode of the second freewheeling switch tube Q6, and then flow to the first output inductor L1. After the second preset conduction time, the capacitor voltage will be consumed to 0, or after dropping to 0, it will be charged by the first output inductor L1 and / or the second output inductor L2 to generate a positive polarity voltage.

[0125] If the first freewheeling switch tube Q5 cannot be turned on normally, that is, there is an open circuit fault, the output capacitor C2 cannot be discharged, and the capacitor voltage after the second preset conduction time will maintain the original negative polarity.

[0126] Therefore, in step S251B, when the capacitor voltage after the first preset conduction time is of the second polarity, the first freewheeling switch tube Q5 is controlled to be turned on, and then in step S252B, when the capacitor voltage after the second preset conduction time is still of the second polarity, it can be determined that the first freewheeling switch tube Q5 has an open circuit fault.

[0127] On the contrary, if the capacitor voltage after the second preset conduction time is 0 or the polarity is opposite to the second polarity, it can be determined that the first freewheeling switch tube Q5 has no open circuit fault. That is to say, if after the first lower switch tube Q2 and the second upper switch tube Q3 are controlled to be turned on for the first preset conduction time, the capacitor voltage is the second polarity, and after the first freewheeling switch tube Q5 is controlled to be turned on for the second preset conduction time, the capacitor voltage is 0 or the polarity is opposite to the second polarity, it can be determined that the first lower switch tube Q2 and the second upper switch tube Q3 have no open circuit faults, the first upper switch tube Q1 and the second lower switch tube Q4 have no short circuit faults, and the first freewheeling switch tube Q5 has no short circuit faults and open circuit faults.

[0128] In addition, if after controlling the first lower switch tube Q2 and the second upper switch tube Q3 to be turned on for the first preset conduction time, the capacitor voltage is 0 or the polarity is opposite to the second polarity, it means that at least one of the first lower switch tube Q2 and the second upper switch tube Q3 has an open circuit fault, and / or, at least one of the first lower switch tube Q2 and the second upper switch tube Q3 has an open circuit fault, and / or, at least one of the first upper switch tube Q1, the second lower switch tube Q4, and the first freewheeling switch tube Q5 has a short circuit fault.

[0129] It should be understood that the method of the embodiment of the present application may first execute step S241A, step S251A and step S252A in sequence, and then execute step S241B, step S251B and step S252B in sequence. Alternatively, it is also possible to first execute step S241B, step S251B and step S252B in sequence, and then execute step S241A, step S251A and step S252A in sequence. Finally, in combination with steps S241A, S251A, S252A, S242B, S251B, S252B, it is possible to implement open circuit fault detection of the two switch tubes of the freewheeling bridge arm 13.

[0130] In addition, after obtaining the capacitor voltage of the output capacitor C2 and the bus voltage of the DC bus (i.e., step S21), since the capacitor voltage may be greater than the first preset value, if the target switch tubes of the first bridge arm 11 and the second bridge arm 12 are controlled to be turned on, the output capacitor C2 may reversely charge the DC bus because the capacitor voltage is greater than the bus voltage, which is not conducive to the device safety and fault detection of the inverter unit 10. Therefore, in this case, the output capacitor C2 needs to be discharged.

[0131] Therefore, please continue to read Figure 6 After obtaining the capacitor voltage of the output capacitor and the bus voltage of the DC bus, the control method further includes:

[0132] Step S26: When the capacitor voltage is greater than the first preset value, the switch tube in the freewheeling bridge arm is controlled to be turned on.

[0133] In step S26, the controller can control the first freewheeling switch tube Q5 and the second freewheeling switch tube Q6 to be turned on, so that the output capacitor C2 can be connected with the first output inductor L1, the freewheeling bridge arm 13 and the second output inductor L2 to form a loop and discharge.

[0134] Step S27: after the third preset conduction time, determining whether the capacitor voltage is less than or equal to the first preset value.

[0135] It can be understood that in step S26, if the switch tube of the freewheeling bridge arm 13 can be turned on normally, the output capacitor C2 can be discharged, so that the capacitor voltage gradually decreases. When the duration of controlling the first freewheeling switch tube Q5 and the second freewheeling switch tube Q6 to be turned on reaches the third preset turn-on duration, the output capacitor C2 is discharged, and the capacitor voltage will drop to less than or equal to the first preset value. If at least one of the switch tubes Q5 and Q6 of the freewheeling bridge arm 13 cannot be turned on normally, the output capacitor C2 cannot be discharged, and the capacitor voltage cannot decrease. Therefore, in step S27, the capacitor voltage after the third preset turn-on duration is compared with the first preset value, which can facilitate the judgment of whether there is a switch tube open circuit fault in the freewheeling bridge arm 13.

[0136] Among them, the third preset conduction time can be set accordingly according to actual conditions and is not limited here.

[0137] Step S28: If the capacitor voltage is still greater than the first preset value after the third preset conduction time, it is confirmed that the freewheeling bridge arm is faulty.

[0138] When the first freewheeling switch tube Q5 and the second freewheeling switch tube Q6 are controlled to be turned on, if at least one of the first freewheeling switch tube Q5 and the second freewheeling switch tube Q6 has an open circuit fault, then after the third preset conduction time, the output capacitor C2 will be unable to discharge, resulting in the capacitor voltage still being greater than the first preset value. Therefore, when the capacitor voltage after the third preset conduction time is greater than the first preset value, it can be determined that the freewheeling bridge arm 13 has a fault.

[0139] On the contrary, if the capacitor voltage is less than or equal to the first preset value after the third preset conduction time, the process proceeds to step S24 for further detection and judgment when the bus capacitance is greater than the second preset value. When the bus capacitance is less than or equal to the second preset value, the process proceeds to the following step S29.

[0140] In general, when the acquired capacitor voltage is greater than the first preset value, the control logic of the freewheeling bridge arm 13 in the method of the embodiment of the present application, combined with the real-time capacitor voltage size, can detect whether the freewheeling bridge arm 13 is faulty. The method is simple, easy to implement and low cost.

[0141] In addition, after obtaining the capacitor voltage of the output capacitor C2 and the bus voltage of the DC bus (i.e., step S21), since the bus voltage may be less than or equal to the second preset value, if the target switch tubes of the first bridge arm 11 and the second bridge arm 12 are controlled to be turned on, the bus voltage will not be sufficient to charge the output capacitor C2, which is not conducive to fault detection. Therefore, in this case, the DC bus needs to be charged.

[0142] In some embodiments, the inverter circuit 100 is provided with a pre-charging unit 30, so the DC bus can be charged by the pre-charging unit 30. Figure 6 After obtaining the capacitor voltage of the output capacitor and the bus voltage of the DC bus, the control method further includes:

[0143] Step S29: When the bus voltage is less than or equal to a second preset value, control the pre-charging unit to charge the DC bus.

[0144] In this embodiment, if Figure 3 As shown, the first end of the pre-charging unit 30 can be connected to the power grid 500, and the second end of the pre-charging unit 30 can be connected to the DC bus. Furthermore, the pre-charging unit 30 can draw power from the power grid 500 to supply power to the DC bus.

[0145] In one embodiment, the pre-charging unit 30 may include a current limiting resistor and a pre-charging switch connected in series. The pre-charging switch can be controlled by a controller to be on or off. When the pre-charging switch is turned on, the pre-charging unit 30 can draw power from the power grid 500 and supply it to the DC bus, and the DC bus capacitor C1 on the DC bus can then be charged. When charging is completed, the pre-charging switch is disconnected, and the charging of the DC bus stops. Among them, the current limiting resistor can slow down the bus voltage rise rate, so that the bus voltage gradually rises, avoids voltage shock or current shock, and reduces the fluctuation of the bus voltage.

[0146] It is understandable that the pre-charging unit 30 can also draw power from other power sources, and the structure of the pre-charging unit 30 is not limited thereto, and these can be configured accordingly according to actual conditions.

[0147] Step S30: confirm whether the bus voltage of the DC bus is greater than a second preset value after the preset charging time.

[0148] Among them, the preset charging time can be set accordingly according to actual conditions and is not limited here.

[0149] It can be understood that in step S29, if the pre-charging unit 30 can work normally, and there is no through short circuit fault in the first bridge arm 11, the second bridge arm 12 and the freewheeling bridge arm 13, then the electric energy provided by the power grid 500 will be transmitted to the DC bus through the pre-charging unit 30, so that the bus voltage gradually increases. After the DC bus is charged, the bus voltage will rise to a value greater than or equal to the second preset value.

[0150] If the pre-charging unit 30 cannot work normally (for example, the pre-charging switch in the pre-charging unit 30 fails to open circuit, or the current limiting resistor fails to open circuit), the DC bus cannot be charged and the bus voltage cannot rise. Alternatively, if at least one of the first bridge arm 11, the second bridge arm 12 and the freewheeling bridge arm 13 has a direct short circuit fault, then the electric energy connected to the pre-charging unit 30 will flow to the bridge arm with the direct short circuit (because the equivalent impedance is very small), making it impossible to charge the DC bus and the bus voltage cannot rise. Therefore, in step S30, the bus voltage after the preset charging time is compared with the second preset value, which can facilitate the judgment of whether there is a fault in the pre-charging unit 30 and the inverter unit 10.

[0151] Step S31: If the bus voltage of the DC bus is still less than or equal to the second preset value after the preset charging time, it is confirmed that there is a fault in the pre-charging unit or the inverter unit.

[0152] When the pre-charging unit 30 is controlled to charge the DC bus, if at least one of the pre-charging unit 30 and the inverter unit 10 is faulty, the DC bus cannot be charged, and the bus voltage after the preset charging time is still less than or equal to the second preset value. Therefore, when the bus voltage after the preset charging time is less than or equal to the second preset value, it can be determined that the pre-charging unit 30 or the inverter unit 10 is faulty.

[0153] On the contrary, if the bus voltage of the DC bus is greater than the second preset value after the preset charging time, the process proceeds to step S24 for further detection and judgment when the capacitor voltage is less than or equal to the first preset value. When the capacitor voltage is greater than the first preset value, the process proceeds to step S26.

[0154] When the acquired bus voltage is less than or equal to the second preset value, the method in the embodiment of the present application can detect whether the pre-charging unit 30 or the inverter unit 10 has a fault by controlling the pre-charging unit 30 and combining the real-time bus voltage size. The method is simple, easy to implement and low-cost.

[0155] In the embodiment of the present application, after confirming that the inverter unit 10 has no faults through the aforementioned steps, the inverter unit 10 can be put into use to supply power to the load 400 according to the requirements of the load 400 .

[0156] Specifically, the process of driving the inverter unit according to the demand information and the output of the inverter unit, and controlling the switch unit to conduct the connection between the inverter unit, the power grid and the load (ie, step S14) may include:

[0157] The inverter unit is driven according to the demand information, and when the output of the inverter unit meets the demand information, the switch unit is controlled to connect the inverter unit and the load, and disconnect the power grid and the load.

[0158] Here, the controller can adjust the driving signal according to the demand information of the load 400 so that the inverter unit 10 can output a voltage, current or power that is consistent with the demand information. Since the output of the inverter unit 10 can only meet the demand of the load 400 after a certain working time. Therefore, when the inverter unit 10 is driven at the beginning, the bypass switch 23 keeps the connection between the power grid 500 and the load 400 turned on, so that the load 400 continues to be powered by the power grid 500. When the output of the inverter unit 10 meets the demand of the load 400, the bypass switch 23 disconnects the connection between the power grid 500 and the load 400 and the off-grid switch 21 turns on the connection between the inverter unit 10 and the load 400, so as to switch to the inverter unit 10 to power the load 400. This design can ensure that the load 400 can always obtain stable and reliable power supply.

[0159] In one embodiment, see Figure 7 When the output of the inverter unit meets the demand information, the process of controlling the switch unit to connect the inverter unit and the load and disconnect the grid and the load may include:

[0160] Step S41: Obtaining voltage information of the power grid.

[0161] The voltage information of the power grid 500 may include voltage parameters such as voltage phase, voltage amplitude, and voltage frequency of the power grid 500. The controller may be connected to the power grid 500 for communication to obtain the voltage information of the power grid 500, or the voltage information of the power grid 500 may be obtained by detecting the power grid 500 through a detection circuit. The present application does not limit the method for obtaining the voltage information of the power grid 500.

[0162] Step S42: Obtain the closing time required for closing the off-grid switch between the inverter unit and the load, and the opening time required for opening the bypass switch between the grid and the load.

[0163] Among them, the closing time required for the off-grid switch 21 to close needs to be determined according to the model parameters of the off-grid switch 21. The disconnection time required for the bypass switch 23 to disconnect needs to be determined according to the model parameters of the bypass switch 23. In one embodiment, the closing time and the disconnection time can be determined when the switch element leaves the factory, so they can be pre-recorded and stored in the memory. In step S42, the controller can obtain the closing time required for the off-grid switch 21 to close and the disconnection time required for the bypass switch 23 to disconnect from the memory. Alternatively, the controller can also communicate with the device end or the APP end to obtain the closing time required for the off-grid switch 21 to close and the disconnection time required for the bypass switch 23 to disconnect.

[0164] Step S43: Determine output parameters of the inverter unit according to the voltage information and the demand information, where the output parameters include inverter voltage and inverter current.

[0165] It can be understood that the load 400 can be powered by the power grid 500, which means that the required voltage of the load 400 is consistent with the voltage of the power grid 500. Therefore, when switching to power supply by the inverter unit 10, in order to meet the demand of the load 400, the inverter voltage output by the inverter unit 10 needs to be consistent with the voltage of the power grid 500. In addition, it is also necessary to adjust the inverter current output by the inverter unit 10 so that the inverter power output by the inverter unit 10 is consistent with the required power of the load 400. Therefore, in step S43, the inverter voltage and inverter current of the inverter unit 10 need to be determined according to the voltage information of the power grid 500 and the demand information of the load 400 to ensure that the output of the inverter unit 10 can meet the demand of the load 400.

[0166] Step S44: Obtain zero-crossing point information of the power grid.

[0167] Among them, the zero-crossing point of the power grid 500 can be understood as the position and time when the positive and negative half-waves of the alternating current of the power grid cross zero alternately, therefore, the zero-crossing point information of the power grid 500 can include the phase, frequency, time and other information when the alternating current of the power grid 500 crosses zero. In step S44, the zero-crossing point information of the power grid 500 can be obtained by detecting the detection circuit, or by performing waveform analysis and calculation on the alternating current of the power grid to obtain the zero-crossing point information of the power grid 500.

[0168] Step S45: issuing a closing instruction to the off-grid switch in advance according to the zero-crossing information and the closing duration, and issuing a disconnecting instruction to the bypass switch in advance according to the zero-crossing information and the disconnecting duration. The closing instruction is used to drive the off-grid switch to complete closing when the grid crosses zero, and the disconnecting instruction is used to drive the bypass switch to disconnect when the grid crosses zero.

[0169] Among them, the closing instruction and the opening instruction can be two different level signals. For example, the closing instruction can be a high level signal, and the opening instruction can be a low level signal. When the switching element receives a high level signal, it is turned on, and when the switching element receives a low level signal, it cannot be turned on, that is, it is disconnected.

[0170] In step S45, the controller can issue a closing instruction to the off-grid switch 21 within a first preset time before the zero crossing, so that the off-grid switch 21 can be closed before the zero crossing and complete the closing at the zero crossing. The controller can issue a disconnection instruction to the bypass switch 23 within a second preset time before the zero crossing, so that the bypass switch 23 can be switched to an open state at the zero crossing. This design can accurately control the closing of the off-grid switch 21 and the disconnection of the bypass switch 23, avoiding the bypass switch 23 being disconnected first and the off-grid switch 21 not being turned on, resulting in a situation where the load 400 is powered off.

[0171] Step S46: When the power grid passes through zero, the inverter unit is driven according to the output parameters.

[0172] Since the off-grid switch 21 has been closed and the bypass switch 23 is open when the grid 500 passes through the zero point, the inverter unit 10 is driven at this time, and the output of the inverter unit 10 can be provided to the load 400. Moreover, step S46 also uses the zero point of the grid 500 to control the inverter unit 10, which can ensure that the inverter unit 10 follows the switching of the upper switch unit 20 and supplies power to the load 400 in time.

[0173] Through the above steps S41 to S46, the off-grid switch 21, the bypass switch 23 and the inverter unit 10 can be accurately controlled to ensure that the inverter unit 10 can provide the power required by the load 400 in a timely manner.

[0174] In an embodiment of the present application, when it is determined through the aforementioned steps that the inverter unit 10 has a fault, whether it is a fault in the first bridge arm 11 or the second bridge arm 12, a fault in the freewheeling bridge arm 13, or a fault in the pre-charging unit 30, the inverter unit 10 will not be put into use, that is, the inverter unit 10 stops starting, and the load 400 continues to be powered by the power grid 500.

[0175] In addition, the control method of the embodiment of the present application can also provide corresponding prompts for the detected faults. Specifically, the control method can also include:

[0176] When it is determined that a fault exists in the inverter unit, indication information is output, where the indication information is used to indicate the fault information of the inverter unit.

[0177] The fault information may include the fault location and fault type of the inverter unit 10. For example, when it is detected that the first freewheeling switch Q5 has an open circuit fault, the indication information may be used to indicate that the first freewheeling switch Q5 in the freewheeling bridge arm 13 has an open circuit fault.

[0178] In one embodiment, Figure 1 The scene shown may also include an independent display screen (not shown), or any device in the scene may be provided with a display screen. Therefore, the controller may also output indication information to the display screen to visualize the indication information. In another embodiment, the controller may also output the indication information to the device side or the APP side via wireless communication. In this way, it is convenient for users or relevant personnel to be aware of the hardware fault of the current inverter circuit 100, and then take corresponding maintenance measures to eliminate the fault.

[0179] It should be noted that, for the aforementioned method embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations, but those skilled in the art should know that the present application is not limited by the described order of actions, because according to the present application, certain steps can be performed in other orders or simultaneously.

[0180] See also Figure 8, an embodiment of the present application also provides a power conversion device.

[0181] like Figure 8 As shown, the power conversion device 1000 includes an inverter circuit 100 and a controller 600. The inverter circuit 100 and the controller 600 can be set separately or integrally, which is not limited here. The controller 600 can be connected to the inverter circuit 100 and can be used to perform some or all steps in the control method of the inverter circuit provided in any of the previous embodiments.

[0182] It can be understood that the inverter circuit 100, the controller 600 and the control method of the inverter circuit can be specifically referred to the previous description, which will not be repeated here.

[0183] See also Fig. 9 , an embodiment of the present application also provides an energy storage system.

[0184] like Fig. 9 As shown, the energy storage system 2000 includes an inverter circuit 100, an energy storage device 200 and a controller 600. The inverter circuit 100, the energy storage device 200 and the controller 600 can be independently provided, or at least partially integrated together, which is not limited here. The controller 600 can be connected to the inverter circuit 100, and can be used to perform some or all of the steps in the control method of the inverter circuit provided in any of the previous embodiments.

[0185] In some embodiments, the controller 600 may also be connected to the energy storage device 200 and control the operation of the energy storage device 200 .

[0186] In some embodiments, the energy storage system 2000 may further include DC bus bars BUS+ and BUS-, and the energy storage device 200 and the inverter circuit 100 may be connected via the DC bus bars BUS+ and BUS-. The DC bus bars BUS+ and BUS- may be independently provided or provided in the energy storage device 200.

[0187] It can be understood that the control method of the inverter circuit 100, the energy storage device 200, the controller 600, the DC bus and the inverter circuit can refer to the previous description and will not be repeated here.

[0188] See also Fig.10 , an embodiment of the present application also provides an electronic device.

[0189] like Fig.10 As shown, the electronic device 3000 may include a processor 3001 and a memory 3002 .

[0190] The processor 3001 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0191] The memory 3002 may be a read-only memory (ROM) or other types of static storage devices that can store static information and instructions, a random access memory (RAM) or other types of dynamic storage devices that can store information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical disc, laser disc, optical disc, digital versatile disc, Blu-ray disc, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store the desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto. The memory 3002 may exist independently and be connected to the processor 3001 via a bus. The memory 3002 may also be integrated with the processor 3001.

[0192] The memory 3002 is used to store programs, instructions or codes for executing the above control method of the inverter circuit. The processor 3001 is used to execute the programs, instructions or codes stored in the memory 3002. The programs, instructions or codes stored in the memory 3002 can execute some or all steps in the embodiment of the control method of the inverter circuit.

[0193] See also Fig.11 The present application also provides a control device for an inverter circuit. The control device 4000 for an inverter circuit can be applied to Figure 1 In the scenario shown, it can be used to implement the control method of the above-mentioned inverter circuit.

[0194] Specifically, Fig.11As shown, the control device 4000 of the inverter circuit includes a first control module 4001 , a fault detection module 4002 , an acquisition module 4003 and a second control module 4004 .

[0195] The first control module 4001 is used to control the switch unit to conduct the connection between the grid and the load when receiving the output instruction, so that the grid supplies power to the load.

[0196] The fault detection module 4002 is used to control the working state of each switch tube in the inverter unit to perform fault detection on the inverter unit.

[0197] The acquisition module 4003 is used to acquire the load demand information when it is determined that there is no fault in the inverter unit.

[0198] The second control module 4004 is used to drive the inverter unit according to the demand information and the output of the inverter unit, and control the switch unit to conduct the connection between the inverter unit, the power grid and the load.

[0199] It can be understood that the division of the various modules in the control device 4000 of the inverter circuit mentioned above is only for illustrative purposes. In other embodiments, the control device 4000 of the inverter circuit can be divided into different modules as needed to complete all or part of the functions of the control device 4000 of the inverter circuit mentioned above.

[0200] The specific implementation of each module in the embodiment of the present application can also refer to Figures 4 to 7 The corresponding description of the method embodiment is shown, so it will not be described in detail here.

[0201] The functional modules in the embodiments of the present application may be integrated into one processing module / unit, or each module may be a separate module, or two or more modules may be integrated into one module; the above-mentioned integrated modules may be implemented in the form of hardware or in the form of hardware plus software functional modules.

[0202] If the above-mentioned integrated module of the present application is implemented in the form of a software function module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the embodiment of the present application can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the methods described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as mobile storage devices, ROM, RAM, magnetic disks or optical disks.

[0203] The present application also provides a computer-readable storage medium for storing a computer program or code. When the computer program or code is loaded and executed by a processor, the above Figures 4 to 7 All or part of the steps in the control method embodiment of the inverter circuit shown. Among them, the computer-readable storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules or other data). The specific implementation of the computer-readable storage medium can be found in Fig.10 The description of memory 3002 in will not be repeated here.

[0204] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application has been described in detail with reference to the preferred embodiments, a person of ordinary skill in the art should understand that the technical solution of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present application.

Claims

1. A control method for an inverter circuit, characterized in that: The inverter circuit includes an inverter unit and a switch unit, the switch unit is used to respectively conduct the connection between the inverter unit, the power grid and the load, the inverter unit is used to connect to a photovoltaic module or an energy storage device, and the control method includes: When receiving an output instruction, controlling the switch unit to conduct the connection between the power grid and the load, so that the power grid supplies power to the load; Controlling the working state of each switch tube in the inverter unit to perform fault detection on the inverter unit; When it is determined that the inverter unit does not have a fault, obtaining demand information of the load; The inverter unit is driven according to the output of the inverter unit and the demand information, and the switch unit is controlled to conduct the connection between the inverter unit, the power grid and the load.

2. The control method according to claim 1, characterized in that: The inverter unit includes a first bridge arm, a second bridge arm, a freewheeling bridge arm and an output capacitor, the first bridge arm and the second bridge arm are both connected to a DC bus, the midpoint of the first bridge arm and the midpoint of the second bridge arm serve as output ends of the inverter unit and are connected to the switch unit, the output capacitor and the freewheeling bridge arm are connected in parallel between the midpoint of the first bridge arm and the midpoint of the second bridge arm, and the first bridge arm, the second bridge arm and the freewheeling bridge arm are all provided with switch tubes; the controlling the working state of each switch tube in the inverter unit to perform fault detection on the inverter unit includes: Acquiring a capacitor voltage of the output capacitor and a bus voltage of the DC bus; When the capacitor voltage is less than or equal to a first preset value and the bus voltage is greater than a second preset value, controlling the target switch tubes in the first bridge arm and the second bridge arm to be turned on, wherein the first preset value is less than the second preset value; After a first preset on-time, a fault detection result of the inverter circuit is determined according to the capacitor voltage.

3. The control method according to claim 2, characterized in that: The first bridge arm includes a first upper switch tube and a first lower switch tube connected in series, and the second bridge arm includes a second upper switch tube and a second lower switch tube connected in series; The controlling target switch tubes in the first bridge arm and the second bridge arm to be turned on includes: Controlling the first upper switch tube and the second lower switch tube to be turned on; or The first lower switch tube and the second upper switch tube are controlled to be turned on.

4. The control method according to claim 2 or 3, characterized in that: After the first preset conduction time, determining the fault detection result of the inverter circuit according to the capacitor voltage includes: After the first preset conduction time, if the capacitor voltage is greater than the first preset value, controlling the switch tube in the freewheeling bridge arm to be turned on; After the second preset conduction time, if the capacitor voltage is greater than the first preset value, it is confirmed that the freewheeling bridge arm has a fault.

5. The control method according to claim 3, characterized in that: The freewheeling bridge arm comprises a first freewheeling switch tube and a second freewheeling switch tube connected in series in reverse order; After the first preset conduction time, determining the fault detection result of the inverter circuit according to the capacitor voltage includes: After controlling the first upper switch tube and the second lower switch tube to be turned on for the first preset turn-on time, if the capacitor voltage is of the first polarity, controlling the second freewheeling switch tube to be turned on; after controlling the second freewheeling switch tube to be turned on for the second preset turn-on time, if the capacitor voltage is still of the first polarity, confirming that the second freewheeling switch tube has a fault; Alternatively, after controlling the first lower switch tube and the second upper switch tube to be turned on for the first preset conduction time, if the capacitor voltage is of the second polarity, the first freewheeling switch tube is controlled to be turned on; after controlling the first freewheeling switch tube to be turned on for the second preset conduction time, if the capacitor voltage is still of the second polarity, it is confirmed that the first freewheeling switch tube is faulty; wherein the first polarity and the second polarity are opposite.

6. The control method according to claim 2, characterized in that: After obtaining the capacitor voltage of the output capacitor and the bus voltage of the DC bus, the control method further includes: When the capacitor voltage is greater than the first preset value, controlling the switch tube in the freewheeling bridge arm to be turned on; If the capacitor voltage is still greater than the first preset value after the third preset conduction time, it is confirmed that the freewheeling bridge arm has a fault.

7. The control method according to claim 2, characterized in that: The inverter circuit further includes a pre-charging unit, a first end of the pre-charging unit is connected to the power grid, and a second end of the pre-charging unit is connected to the DC bus; after obtaining the capacitor voltage of the output capacitor and the bus voltage of the DC bus, the control method further includes: When the bus voltage is less than or equal to the second preset value, controlling the pre-charging unit to charge the DC bus; If, after the preset charging time, the bus voltage of the DC bus is still less than or equal to the second preset value, it is confirmed that a fault exists in the pre-charging unit or the inverter unit.

8. The control method according to claim 1, characterized in that: The driving of the inverter unit according to the output of the inverter unit and the demand information, and the controlling of the switch unit to conduct the connection between the inverter unit, the power grid and the load, comprises: The inverter unit is driven according to the demand information, and when the output of the inverter unit meets the demand information, the switch unit is controlled to conduct the connection between the inverter unit and the load, and to disconnect the connection between the power grid and the load.

9. The control method according to claim 8, characterized in that: The switch unit includes an off-grid switch, a grid-connected switch and a bypass switch; when the output of the inverter unit meets the demand information, the switch unit is controlled to conduct the connection between the inverter unit and the load, and disconnect the connection between the grid and the load, including: Acquiring voltage information of the power grid; Obtaining a closing time required for closing the off-grid switch between the inverter unit and the load, and a disconnection time required for disconnecting the bypass switch between the grid and the load; Determining output parameters of the inverter unit according to the voltage information and the demand information, wherein the output parameters include an inverter voltage and an inverter current; Obtaining zero-crossing point information of the power grid; issuing a closing instruction to the off-grid switch in advance according to the zero-crossing point information and the closing duration, and issuing a disconnection instruction to the bypass switch in advance according to the zero-crossing point information and the disconnection duration, the closing instruction being used to drive the off-grid switch to complete closing when the grid crosses zero, and the disconnection instruction being used to drive the bypass switch to disconnect when the grid crosses zero; When the power grid passes through a zero point, the inverter unit is driven according to the output parameter.

10. A power conversion device, characterized in that: The power conversion device includes an inverter circuit and a controller, wherein the inverter circuit includes an inverter unit and a switch unit, the switch unit is used to respectively conduct the connection between the inverter unit, the power grid and the load, and the inverter unit is used to connect to a photovoltaic component or an energy storage device; the controller is used to execute the control method of the inverter circuit as described in any one of claims 1 to 9.

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