Photovoltaic inverter and insulation resistance detection method and circuit thereof

Abstract

The invention relates to a photovoltaic inverter and an insulation resistance detection method and circuit thereof, and the method comprises the steps: determining a target input channel from a plurality of input channels of the photovoltaic inverter when single-channel insulation resistance detection needs to be carried out, controlling the anodes and cathodes of other input channels to be short-circuited, and then carrying out the insulation resistance detection of the photovoltaic inverter, obtaining the resistance value of the insulation positive impedance of the target input channel; determining a to-be-detected input channel from the plurality of input channels as a current detection input channel; controlling the positive electrodes and the negative electrodes of the target input channel and the current detection input channel to be disconnected, and controlling the positive electrodes and the negative electrodes of other input channels except the target input channel and the current detection input channel to be short-circuited; and obtaining a resistance value after the insulation positive impedance of the target input channel and the insulation positive impedance of the current detection input channel are connected in parallel, so that the insulation impedance of a single input channel of the photovoltaic inverter can be detected, and fault positioning and troubleshooting are facilitated.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic power generation, and in particular, to a photovoltaic inverter and an insulation impedance detection method and circuit thereof. Background Art

[0002] With the popularization of photovoltaic grid-connected power generation applications, the safety of photovoltaic grid-connected power generation systems has received increasing attention. Currently, in the photovoltaic grid-connected standards of many countries, there are regulations on the insulation impedance of non-isolated photovoltaic grid-connected inverters, such as VDE-0126, UL1741, etc. It is required that the insulation impedance of the positive and negative terminals of the photovoltaic input of the photovoltaic inverter to the chassis (ground wire) is not less than the specified value before grid-connected power generation can be carried out. Therefore, in corresponding non-isolated grid-connected inverter products, it is necessary to detect the insulation impedance of the photovoltaic inverter before grid connection.

[0003] Currently, the market demand for multi-channel input of inverter products is increasing. However, the existing insulation impedance detection methods are not well applicable to multi-channel input inverters. When an insulation impedance fault occurs in a multi-channel input inverter, the existing insulation impedance detection methods cannot locate the specific fault location, which is not conducive to on-site troubleshooting of insulation faults. Summary of the Invention

[0004] Embodiments of the present application provide a photovoltaic inverter and an insulation impedance detection method and circuit thereof, so as to solve the problem that the existing insulation impedance detection methods cannot locate the specific fault location when an insulation impedance fault occurs in a multi-channel input photovoltaic inverter.

[0005] An embodiment of the present application provides an insulation impedance detection method for a photovoltaic inverter. The photovoltaic inverter has multiple input channels, and the multiple input channels are respectively connected to multiple photovoltaic modules in a corresponding manner. The insulation impedance detection method includes: when single-channel insulation impedance detection is required, determining a target input channel from the multiple input channels; controlling the positive and negative poles of the target input channel to be open-circuited, and controlling the positive and negative poles of the other input channels except the target input channel among the multiple input channels to be short-circuited, and then performing insulation impedance detection on the photovoltaic inverter to obtain a detection result including the resistance value of the insulation positive impedance of the target input channel, so as to complete the detection of the insulation positive impedance of the target input channel; determining the input channel to be detected from the multiple input channels as the current detection input channel; controlling the positive and negative poles of the target input channel and the current detection input channel to be open-circuited, and controlling the positive and negative poles of the other input channels except the target input channel and the current detection input channel among the multiple input channels to be short-circuited, and then performing insulation impedance detection on the photovoltaic inverter to obtain a detection result including the resistance value after the parallel connection of the insulation positive impedance of the target input channel and the insulation positive impedance of the current detection input channel, so as to complete the detection of the insulation positive impedance of the current detection input channel, and returning to execute the step of determining the input channel to be detected from the multiple input channels as the current detection input channel until the detection of the insulation positive impedance of all the input channels to be tested is completed.

[0006] Wherein, the photovoltaic inverter includes multiple boost circuits. The multiple boost circuits correspond to the multiple input channels respectively, and each boost circuit includes a switch. The two ends of the switch are respectively connected to the positive and negative poles of the corresponding input channel. Controlling the positive and negative poles of the target input channel to be open-circuited, and controlling the positive and negative poles of the other input channels except the target input channel among the multiple input channels to be short-circuited includes: controlling the switch of the boost circuit corresponding to the target input channel to be turned off, and controlling the switches of the boost circuits corresponding to the other input channels except the target input channel among the multiple input channels to be turned on; controlling the positive and negative poles of the target input channel and the current detection input channel to be open-circuited, and controlling the positive and negative poles of the other input channels except the target input channel and the current detection input channel among the multiple input channels to be short-circuited includes: turning off the switches of the boost circuits corresponding to the target input channel and the current detection input channel, and turning on the switches of the boost circuits corresponding to the other input channels except the target input channel and the current detection input channel among the multiple input channels.

[0007] Among them, the photovoltaic inverter includes a positive bus and a negative bus; the insulation impedance detection method is applied to an insulation impedance detection circuit, and the insulation impedance detection circuit is respectively connected to the positive bus, the negative bus and the common ground terminal; the insulation impedance detection circuit has a first detection state and a second detection state; and, when the insulation impedance detection circuit is in the first detection state, the impedance between the positive bus and the common ground terminal is a first impedance, and the impedance between the negative bus and the common ground terminal is a second impedance; when the insulation impedance detection circuit is in the second detection state, the impedance between the positive bus and the common ground terminal is a third impedance, and the impedance between the negative bus and the common ground terminal is a fourth impedance; the insulation impedance detection of the photovoltaic inverter includes: controlling the insulation impedance detection circuit to be in the first detection state, and when the insulation impedance detection circuit is in the first detection state, collecting the voltage between the common ground terminal and the negative bus to obtain a first voltage; controlling the insulation impedance detection circuit to be in the second detection state, and when the insulation impedance detection circuit is in the second detection state, collecting the voltage between the common ground terminal and the negative bus to obtain a second voltage; calculating the resistance value of the insulation impedance according to the first voltage and the second voltage, and the insulation impedance includes the insulation positive impedance of all input channels where the positive and negative poles are open-circuited.

[0008] Among them, the insulation impedance detection circuit includes a first detection resistor, a second detection resistor, a third detection resistor, a fourth detection resistor, a first controllable switch and a second controllable switch. Among them, the first detection resistor, the second detection resistor, the third detection resistor and the fourth detection resistor are connected in series in sequence. The non-series connection end of the first detection resistor is connected to the positive bus. The connection end between the first detection resistor and the second detection resistor is connected to the first end of the first controllable switch. The connection end between the second detection resistor and the third detection resistor and the second end of the first controllable switch are both connected to the common ground terminal. The connection end between the third detection resistor and the fourth detection resistor is connected to the first end of the second controllable switch. The non-series connection end of the fourth detection resistor and the second end of the second controllable switch are both connected to the negative bus; controlling the insulation impedance detection circuit to be in the first detection state includes: controlling the first controllable switch to conduct and controlling the second controllable switch to turn off, and the resistance value of the first impedance is equal to the resistance value of the first detection resistor, and the resistance value of the second impedance is equal to the sum of the resistance values of the third detection resistor and the fourth detection resistor; controlling the insulation impedance detection circuit to be in the second detection state includes: controlling the first controllable switch to turn off and controlling the second controllable switch to conduct, and the resistance value of the third impedance is equal to the sum of the resistance values of the first detection resistor and the second detection resistor, and the resistance value of the fourth impedance is equal to the resistance value of the third detection resistor.

[0009] Among them, calculating the resistance value of the insulation impedance according to the first voltage and the second voltage includes: calculating the resistance value of the insulation positive impedance of all input channels where the positive and negative poles are open-circuited through a first calculation formula. Among them, the first calculation formula is:

[0010]

[0011] Among them, U a and U b are the first voltage and the second voltage respectively, V2 is the voltage between the positive bus and the negative bus, R aP and R bP are the resistance values of the first impedance and the third impedance respectively, R aN and R bN are the resistance values of the second impedance and the fourth impedance respectively; R eqP is the resistance value of the insulation positive impedance of all input channels with the positive and negative poles open, V eq is the equivalent voltage on the positive pole of all input channels with the positive and negative poles open.

[0012] Among them, the resistance value of the insulation impedance also includes the resistance value after the parallel connection of the insulation positive impedance of all input channels with the positive and negative poles short-circuited and the insulation negative impedance of the overall multiple input channels; according to the first voltage and the second voltage, the resistance value of the insulation impedance is calculated, including: calculating the resistance value after the parallel connection of the insulation positive impedance of all input channels with the positive and negative poles short-circuited and the insulation negative impedance of the overall multiple input channels through the second calculation formula, where the second calculation formula is:

[0013]

[0014] Among them, U a and U b are the first voltage and the second voltage respectively, V2 is the voltage between the positive bus and the negative bus, R aP and R bP are the resistance values of the first impedance and the third impedance respectively, R aN and R bN are the resistance values of the second impedance and the fourth impedance respectively; R eqN is the resistance value after the parallel connection of the insulation positive impedance of all input channels with the positive and negative poles short-circuited and the insulation negative impedance of the overall multiple input channels, V eq is the equivalent voltage on the positive pole of all input channels with the positive and negative poles open.

[0015] Among them, before determining the target input channel from multiple input channels, the insulation impedance detection method of the photovoltaic inverter further includes: when at least one input channel among the multiple input channels reaches the wake-up voltage of the photovoltaic inverter, detecting the resistance value of the insulation impedance of the overall multiple input channels, and when the resistance value of the insulation impedance of the overall multiple input channels is less than a preset threshold, determining that single-channel insulation impedance detection needs to be performed; or, when receiving a single-channel insulation impedance detection instruction, determining that single-channel insulation impedance detection needs to be performed.

[0016] Among them, determining a target input channel from multiple input channels includes: determining, from the multiple input channels, the input channel with the highest voltage on the positive electrode as the target input channel; determining, from the multiple input channels, the input channel to be detected as the current detection input channel; and determining, from the multiple input channels, the input channel to be detected with the highest voltage on the positive electrode as the current detection input channel.

[0017] An embodiment of the present application also provides an insulation impedance detection circuit for a photovoltaic inverter. The insulation impedance detection circuit for the photovoltaic inverter includes a control processing unit, and the control processing unit is used to execute the steps in any one of the above insulation impedance detection methods.

[0018] An embodiment of the present application also provides a photovoltaic inverter, and the photovoltaic inverter includes the insulation impedance detection circuit in any one of the above.

[0019] The photovoltaic inverter, its insulation impedance detection method and circuit provided by the present application, when it is necessary to perform single-channel insulation impedance detection, determine a target input channel from multiple input channels of the photovoltaic inverter, then control the positive and negative electrodes of the target input channel to be open-circuited, and control the positive and negative electrodes of other input channels except the target input channel among the multiple input channels to be short-circuited. Then, perform insulation impedance detection on the photovoltaic inverter to obtain a detection result including the resistance value of the insulation positive impedance of the target input channel, so as to complete the detection of the insulation positive impedance of the target input channel. Then, determine the input channel to be detected from the multiple input channels as the current detection input channel. Then, control the positive and negative electrodes of the target input channel and the current detection input channel to be open-circuited, and control the positive and negative electrodes of other input channels except the target input channel and the current detection input channel among the multiple input channels to be short-circuited. Then, perform insulation impedance detection on the photovoltaic inverter to obtain a detection result including the resistance value after the parallel connection of the insulation positive impedance of the target input channel and the insulation positive impedance of the current detection input channel, so as to complete the detection of the insulation positive impedance of the current detection input channel, and return to execute the step of determining the input channel to be detected from the multiple input channels as the current detection input channel until the detection of the insulation positive impedance of all input channels to be tested is completed. Thus, through the short-circuit method, the parallel transfer of the insulation positive impedance of some input channels is realized, and thus the insulation impedance of a single input channel of the photovoltaic inverter can be detected, which is convenient for fault location and troubleshooting. Description of the Drawings

[0020] The following will combine the drawings and describe in detail the specific implementation manners of the present application, and the technical solutions and other beneficial effects of the present application will be obvious.

[0021] Figure 1 It is a schematic circuit diagram of the photovoltaic inverter provided by the embodiment of the present application;

[0022] Figure 2Schematic diagram of the circuit structure of the voltage detection circuit provided by the embodiment of the present application;

[0023] Figure 3 Schematic diagram of the structure of the control processing unit provided by the embodiment of the present application;

[0024] Figure 4 Schematic flow chart of the insulation impedance detection method for the photovoltaic inverter provided by the embodiment of the present application;

[0025] Figure 5 Another schematic flow chart of the insulation impedance detection method for the photovoltaic inverter provided by the embodiment of the present application;

[0026] Figure 6 Schematic flow chart of the insulation impedance detection for the photovoltaic inverter provided by the embodiment of the present application;

[0027] Figure 7 Equivalent circuit diagram after the positive and negative poles of the control target input channel are open-circuited and the positive and negative poles of other input channels are short-circuited provided by the embodiment of the present application. Detailed implementation manners

[0028] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0029] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present application. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the described features. In the description of the present application, "a plurality" means two or more unless otherwise specifically defined.

[0030] In the description of the present application, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a connection that allows mutual communication; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0031] In the present application, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over", and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "beneath", and "underneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the horizontal height of the first feature is lower than that of the second feature.

[0032] The following disclosure provides many different embodiments or examples for implementing different structures of the present application. To simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present application. In addition, the present application may repeat reference numerals and / or reference letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0033] The following is a detailed description in conjunction with specific embodiments. It should be noted that the serial numbers of the following embodiments do not limit the preferred order of the embodiments.

[0034] Please refer to Figure 1 , Figure 1 , which is a schematic circuit structure diagram of a photovoltaic inverter provided by an embodiment of the present application. As Figure 1 shown, the photovoltaic inverter 100 includes a positive bus BUS+ and a negative bus BUS-. Among them, the positive bus BUS+ and the negative bus BUS- are respectively wires for power supply and grounding in the circuit. In a DC circuit, the positive bus BUS+ and the negative bus BUS- play the role of transmitting positive and negative charges.

[0035] Among them, the photovoltaic inverter 100 is an inverter that takes the output voltage of the photovoltaic module as the input voltage. The photovoltaic module is a device that converts solar energy into electrical energy.

[0036] The photovoltaic inverter 100 may further include an insulation impedance detection circuit 10. The insulation impedance detection circuit 10 is respectively connected to the positive bus bar BUS+, the negative bus bar BUS-, and the common ground terminal PE.

[0037] The insulation impedance detection circuit 10 can be configured into a first detection state and a second detection state, that is, it can have a first detection state and a second detection state. And, in different detection states, the resistance value of the impedance of the positive bus bar BUS+ to the common ground terminal PE (that is, the impedance between the positive bus bar BUS+ and the common ground terminal PE) and the resistance value of the impedance of the negative bus bar BUS- to the common ground terminal PE (that is, the impedance between the negative bus bar BUS- and the common ground terminal PE) can be different in magnitude.

[0038] Specifically, when the insulation impedance detection circuit 10 is in the first detection state, the impedance between the positive bus bar BUS+ and the common ground terminal PE is the first impedance, and the impedance between the negative bus bar BUS- and the common ground terminal PE is the second impedance; when the insulation impedance detection circuit 10 is in the second detection state, the impedance between the positive bus bar BUS+ and the common ground terminal PE is the third impedance, and the impedance between the negative bus bar BUS- and the common ground terminal PE is the fourth impedance. And, the resistance values of the first impedance, the second impedance, the third impedance, and the fourth impedance are different.

[0039] It should be noted that, in this embodiment, the insulation impedance detection circuit 10 can be built into the photovoltaic inverter 100 (as Figure 1 shown), or can be external to the photovoltaic inverter 100. And, for the sake of easy understanding, the following takes the insulation impedance detection circuit 10 built into the photovoltaic inverter 100 as an example for specific description. As Figure 1 shown, the insulation impedance detection circuit 10 may include a first detection resistor R1, a second detection resistor R2, a third detection resistor R3, a fourth detection resistor R4, a first controllable switch S1, and a second controllable switch S2.

[0040] Among them, the first detection resistor R1, the second detection resistor R2, the third detection resistor R3, and the fourth detection resistor R4 are connected in series in sequence. The non-series connection end of the first detection resistor R1 is connected to the positive bus bar BUS+. The connection end between the first detection resistor R1 and the second detection resistor R2 is connected to the first end of the first controllable switch S1. The connection end between the second detection resistor R2 and the third detection resistor R3 and the second end of the first controllable switch S1 are both connected to the common ground terminal PE. The connection end between the third detection resistor R3 and the fourth detection resistor R4 is connected to the first end of the second controllable switch S2. The non-series connection end of the fourth detection resistor R4 and the second end of the second controllable switch S2 are both connected to the negative bus bar BUS-. Exemplarily, both the first controllable switch S1 and the second controllable switch S2 can specifically be relays.

[0041] Specifically, by controlling the conduction and cutoff of the first controllable switch S1 and the second controllable switch S2, the insulation impedance detection circuit 10 can be configured into a first detection state and a second detection state.

[0042] For example, by controlling the first controllable switch S1 to conduct and controlling the second controllable switch S2 to cutoff, the insulation impedance detection circuit 10 can be controlled to be in the first detection state. By controlling the first controllable switch S1 to cutoff and controlling the second controllable switch S2 to conduct, the insulation impedance detection circuit 10 can be controlled to be in the second detection state. Thus, when the insulation impedance detection circuit 10 is in the first detection state, the impedance between the positive bus bar BUS+ and the common ground terminal PE is the first detection resistor R1. That is, the resistance value of the first impedance is equal to the resistance value of the first detection resistor R1, and the impedance between the negative bus bar BUS- and the common ground terminal PE is the series-connected third detection resistor R3 and fourth detection resistor R4. That is, the resistance value of the second impedance is equal to the sum of the resistance values of the third detection resistor R3 and the fourth detection resistor R4. When the insulation impedance detection circuit 10 is in the second detection state, the impedance between the positive bus bar BUS+ and the common ground terminal PE is the resistor after the series connection of the first detection resistor R1 and the second detection resistor R2 in series. That is, the resistance value of the third impedance is equal to the sum of the resistance values of the first detection resistor R1 and the second detection resistor R2, and the impedance between the negative bus bar BUS- and the common ground terminal PE is the third detection resistor R3. That is, the resistance value of the fourth impedance is equal to the resistance value of the third detection resistor R3.

[0043] In some embodiments, as Figure 1 shown, the insulation impedance detection circuit 10 may further include a control processing unit 11 and a voltage detection circuit 12. Among them, the control processing unit 11 can be used to control the conduction and cutoff of any switch (for example, the first controllable switch S1 and the second controllable switch S2) in the photovoltaic inverter 100. The voltage detection circuit 12 can be used to detect the voltage between the common ground terminal PE and the negative bus bar BUS- and transmit this voltage to the control processing unit 11.

[0044] Exemplarily, as Figure 2 shown, the voltage detection circuit 12 may include a first voltage detection resistor Ra, a second voltage detection resistor Rb, and an amplifier U1. Wherein, one end of the first voltage detection resistor Ra and one end of the second voltage detection resistor Rb are respectively connected to two input ends of the amplifier U1, the other end of the first voltage detection resistor Ra and the other end of the second voltage detection resistor Rb are respectively connected to the common ground terminal PE and the negative bus bar BUS-, and the output end of the amplifier U1 is connected to the control processing unit 11, so that the voltage between the common ground terminal PE and the negative bus bar BUS- detected by the voltage detection circuit 12 can be transmitted to the control processing unit 11 through the output end of the amplifier U1.

[0045] Specifically, the control processing unit 11 may adopt a microcontroller unit (MCU) or a digital signal processing (DSP) controller, etc.

[0046] Exemplarily, as Figure 3 shown, the control processing unit 11 includes at least one processor 111 and a memory 112. Wherein, the memory 112 may be built in the control processing unit 11, or may be external to the control processing unit 11. The memory 112 may also be a remotely provided memory, and is connected to the control processing unit 11 through a network.

[0047] The memory 112, as a non-volatile computer-readable storage medium, can be used to store non-volatile software programs, non-volatile computer-executable programs, and modules. The memory 112 may include a program storage area and a data storage area. Wherein, the program storage area may store an operating system and application programs required for at least one function; the data storage area may store data created according to the use of the terminal, etc. In addition, the memory 112 may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one magnetic disk storage device, a flash memory device, or other non-volatile solid-state storage devices. In some embodiments, the memory 112 may optionally include a memory remotely provided with respect to the processor 111, and these remote memories may be connected to the terminal through a network. Examples of the above network include but are not limited to the Internet, an enterprise internal network, a local area network, a mobile communication network, and combinations thereof.

[0048] The processor 111 executes various functions of the terminal and processes data by running or executing software programs and / or modules stored in the memory 112, and by calling data stored in the memory 112, so as to perform overall monitoring of the terminal, for example, implementing the insulation impedance detection method described in any embodiment of the present application.

[0049] The processor 111 can be one or more, Figure 3 and one processor 111 is taken as an example. The processor 111 and the memory 112 can be connected through a bus or other means. The processor 111 can include a central processing unit (CPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a controller, a field programmable gate array (FPGA) device, etc. The processor 111 can also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

[0050] Please return for reference Figure 1 , the photovoltaic inverter 100 includes a plurality of input channels, and the plurality of input channels are respectively connected to a plurality of photovoltaic modules correspondingly, wherein the photovoltaic modules can specifically be photovoltaic strings. Specifically, each input channel of the photovoltaic inverter 100 is connected to a corresponding photovoltaic module to input voltage. The above-mentioned plurality of input channels can include a first input channel PV1, a second input channel PV2,..., an nth input channel PVn, where n is an integer greater than 1 and is equal to the number of input channels included in the photovoltaic inverter 100. Among them, the first input channel PV1 includes a positive electrode PV1+ and a negative electrode PV1-; the second input channel PV2 includes a positive electrode PV2+ and a negative electrode PV2-;...; the nth input channel PVn includes a positive electrode PVn+ and a negative electrode PVn-.

[0051] In the embodiment of the present application, the insulation positive impedance of a single input channel refers to the impedance of the positive electrode of a single input channel to the common ground terminal PE, and the insulation negative impedance of a single input channel refers to the impedance of the negative electrode of a single input channel to the common ground terminal PE.

[0052] In the embodiment of the present application, as Figure 1 shown, the impedance of the positive electrode PV1+ of the first input channel PV1 to the common ground terminal PE (i.e., the insulation positive impedance of the first input channel PV1) is represented as impedance RP1, the impedance of the positive electrode PV2+ of the second input channel PV2 to the common ground terminal PE (i.e., the insulation positive impedance of the second input channel PV2) is represented as impedance RP2,..., the impedance of the positive electrode PVn+ of the nth input channel PVn to the common ground terminal PE (i.e., the insulation positive impedance of the nth input channel PVn) is represented as impedance RPn.

[0053] In the embodiment of the present application, as Figure 1As shown, the impedance of the negative pole PV1- of the first input channel PV1 to the common ground terminal PE (i.e., the insulation negative impedance of the first input channel PV1) is represented as impedance RN1, the impedance of the negative pole PV2- of the second input channel PV2 to the common ground terminal PE (i.e., the insulation negative impedance of the second input channel PV2) is represented as impedance RN2, …, the impedance of the negative pole PVn- of the nth input channel PVn to the common ground terminal PE (i.e., the insulation negative impedance of the nth input channel PVn) is represented as impedance RNn.

[0054] In the embodiment of the present application, as Figure 1 shown, the negative poles PV1- of the first input channel PV1, PV2- of the second input channel PV2, …, PVn- of the nth input channel PVn share a busbar, and this busbar is the negative busbar BUS-.

[0055] In the embodiment of the present application, as Figure 1 shown, the photovoltaic inverter 100 may further include a plurality of boost circuits. The plurality of boost circuits respectively correspond to the above-mentioned plurality of input channels, and each boost circuit may include a switch, and both ends of the switch are respectively connected to the positive and negative poles of the corresponding input channel.

[0056] Specifically, the number of boost circuits in the photovoltaic inverter 100 may be equal to the number of input channels. That is to say, the number of boost circuits included in the photovoltaic inverter 100 may also be n. And each boost circuit is connected to the positive pole of a corresponding input channel, and each boost circuit may include an inductor, a switch and a diode. Among them, the switch may specifically be a switching tube.

[0057] Exemplarily, as Figure 1 shown, the ith boost circuit may be connected to the positive pole PVi+ of the ith input channel PVi, and the ith boost circuit may include an inductor Li, a switch Qi and a diode Di, where i is an integer greater than or equal to 1 and less than or equal to n. And the connection relationship between the components please refer to Figure 1 , which will not be elaborated here. Specifically, in the ith boost circuit, when the switch Qi is turned on, the inductor Li is charged; when the switch Qi is turned off, the sum of the voltage on the positive pole PVi+ of the ith input channel PVi and the voltage on the inductor Li supplies power to the subsequent circuit together, so as to achieve the purpose of boosting.

[0058] Specifically, as Figure 1 shown, the photovoltaic inverter 100 may further include a first capacitor C1, a second capacitor C2 and an inverter bridge 13. The connection relationship between the components please refer to Figure 1, which will not be elaborated here. Among them, the first capacitor C1 and the second capacitor C2 are used for filtering, and the inverter bridge 13 is used to implement the inverter function to convert direct current into alternating current.

[0059] Please refer to Figure 4 , Figure 4 FIG. is a schematic flow chart of the insulation impedance detection method for the photovoltaic inverter provided by the embodiment of the present application. The photovoltaic inverter has a plurality of input channels, and the plurality of input channels are respectively connected to a plurality of photovoltaic modules correspondingly. Moreover, the specific structure of the photovoltaic inverter can refer to the detailed description of Figure 1 above, so it will not be elaborated here. The insulation impedance detection method of the photovoltaic inverter can be applied to an insulation impedance detection circuit, and the insulation impedance detection circuit is respectively connected to the positive bus, the negative bus and the common ground terminal in the photovoltaic inverter. Moreover, the insulation impedance detection circuit can be implemented by a circuit structure as shown in Figure 1 , and the specific implementation process has been described in detail in the above embodiment, so it will not be elaborated here.

[0060] As shown in Figure 4 , the specific process of the insulation impedance detection method of the photovoltaic inverter can be as follows:

[0061] Step S101. When single-channel insulation impedance detection is required, determine a target input channel from the plurality of input channels.

[0062] Specifically, when single-channel insulation impedance detection is required, the input channel with the highest voltage on the positive electrode can be determined as the target input channel from the plurality of input channels included in the above photovoltaic inverter. In other words, the target input channel can specifically be the input channel with the highest voltage on the positive electrode among the plurality of input channels included in the above photovoltaic inverter.

[0063] Step S102. Control the positive electrode and the negative electrode of the target input channel to be open-circuited, and control the positive electrodes and the negative electrodes of the other input channels except the target input channel among the plurality of input channels to be short-circuited. Then, perform insulation impedance detection on the photovoltaic inverter to obtain a detection result including the resistance value of the insulation positive impedance of the target input channel, so as to complete the detection of the insulation positive impedance of the target input channel.

[0064] Specifically, taking Figure 1Taking the circuit structure shown as an example, the switch of the boost circuit corresponding to the target input channel can be controlled to turn off, and the switches of the boost circuits corresponding to the other input channels except the target input channel among the multiple input channels included in the photovoltaic inverter 100 can be controlled to turn on, so as to control the positive and negative poles of the target input channel to be open-circuited, and to control the positive and negative poles of the other input channels except the target input channel to be short-circuited. In this way, the positive and negative poles of the input channel are short-circuited through the switch of the boost circuit of the photovoltaic inverter, without the need to additionally add devices, which is beneficial to cost savings.

[0065] Step S103. Determine the input channel to be detected from the multiple input channels as the current detection input channel.

[0066] In some embodiments, the input channel to be detected with the highest voltage on the positive pole among the multiple input channels included in the photovoltaic inverter can be determined as the current detection input channel. In other words, the current detection input channel can specifically be one of the input channels to be detected with the highest voltage on the positive pole among the multiple input channels included in the photovoltaic inverter.

[0067] In other embodiments, one of the input channels to be detected can also be randomly selected from the multiple input channels included in the photovoltaic inverter as the current detection input channel. In other words, the current detection input channel can specifically be any one of the input channels to be detected among the multiple input channels included in the photovoltaic inverter.

[0068] Step S104. Control the positive and negative poles of the target input channel and the current detection input channel to be open-circuited, and control the positive and negative poles of the other input channels except the target input channel and the current detection input channel among the multiple input channels to be short-circuited, and then perform an insulation impedance detection on the photovoltaic inverter to obtain a detection result including the resistance value after the insulation positive impedance of the target input channel and the insulation positive impedance of the current detection input channel are connected in parallel, so as to complete the detection of the insulation positive impedance of the current detection input channel, and return to execute the step of determining the input channel to be detected from the multiple input channels as the current detection input channel until the detection of the insulation positive impedance of all the input channels to be tested is completed.

[0069] Specifically, taking Figure 1 the circuit structure shown as an example, the switches of the boost circuits corresponding to the target input channel and the current detection input channel can be controlled to turn off, and the switches of the boost circuits corresponding to the other input channels except the target input channel and the current detection input channel among the multiple input channels included in the photovoltaic inverter 100 can be controlled to turn on, so as to control the positive and negative poles of the target input channel and the current detection input channel to be open-circuited, and to control the positive and negative poles of the other input channels except the target input channel and the current detection input channel to be short-circuited.

[0070] In some embodiments, as Figure 5 shown, the above step S104 may specifically include:

[0071] Step S1041. Control the positive and negative poles of the target input channel and the current detection input channel to be open-circuited, and control the positive and negative poles of the other input channels except the target input channel and the current detection input channel among the multiple input channels to be short-circuited. Then, perform an insulation impedance detection on the photovoltaic inverter to obtain a detection result including the resistance value after the insulation positive impedance of the target input channel and the insulation positive impedance of the current detection input channel are connected in parallel, so as to complete the detection of the insulation positive impedance of the current detection input channel.

[0072] Step S1042. Determine whether the detection of the insulation positive impedance of all input channels is completed. If not, return to execute step S103. If so, end.

[0073] In this way, after executing the above step S1042, it is possible to then return to sequentially execute the above step S103 and the above step S1041 in turn to form a loop. And when it is determined that the detection of the insulation positive impedance of all input channels is not completed, it can enter the next loop. In this way, as the number of loops increases, the number of input channels for which the insulation positive impedance detection is completed will increase successively, and the number of input channels to be detected (i.e., the input channels for which the insulation positive impedance detection is not completed) among the multiple input channels included in the photovoltaic inverter will decrease successively, and finally the detection of the insulation positive impedance of all input channels will be completed. Moreover, after the detection of the insulation positive impedance of all input channels is completed, the insulation positive impedance of each input channel can be output respectively, so as to facilitate relevant personnel to quickly locate the specific fault location based on the insulation positive impedance of each input channel, thereby helping to improve the processing efficiency of insulation faults.

[0074] In some embodiments, as Figure 5 shown, before the above step S101, the insulation impedance detection method of the above photovoltaic inverter may further include:

[0075] Step S11. When at least one of the multiple input channels reaches the wake-up voltage of the photovoltaic inverter, detect the resistance value of the overall insulation impedance of the multiple input channels.

[0076] Wherein, the wake-up voltage of the photovoltaic inverter refers to the lowest voltage level required for the photovoltaic inverter to recover from the standby state to the normal working state. When the voltage on the positive pole of an input channel reaches this specific level, the photovoltaic inverter will be activated and start to work. And the wake-up voltage of the photovoltaic inverter is usually determined by the design of the photovoltaic inverter.

[0077] Specifically, when the voltage on the positive electrode of at least one input channel among the multiple input channels included in the above photovoltaic inverter is greater than or equal to the wake-up voltage of the photovoltaic inverter, the insulation impedance detection of the photovoltaic inverter can be performed to obtain a detection result including the resistance value of the insulation impedance of the overall multiple input channels included in the above photovoltaic inverter.

[0078] Step S12. When the resistance value of the insulation impedance of the overall multiple input channels is less than a preset threshold, it is determined that single-channel insulation impedance detection needs to be performed.

[0079] Specifically, after obtaining the resistance value of the insulation impedance of the overall multiple input channels included in the above photovoltaic inverter, it can be determined whether the resistance value of the overall insulation impedance is less than a preset threshold. And when it is determined that the resistance value of the overall insulation impedance is less than the preset threshold, it can be determined that single-channel insulation impedance detection needs to be performed; when it is determined that the resistance value of the overall insulation impedance is not less than the preset threshold, it can be determined that single-channel insulation impedance detection is not required, so the next step does not need to be executed.

[0080] In some examples, taking Figure 1 the shown circuit structure as an example, the resistance value of the overall insulation impedance can be the sum of the resistance values of the positive electrodes of the multiple input channels included in the above photovoltaic inverter 100 to the ground (here, the ground refers to the earth), that is, the resistance value after the resistances RP1, RP2,..., RPn, RN1, RN2,..., RNn are connected in parallel. Correspondingly, the above step S12 can specifically include: when the sum of the resistance values of the positive electrodes of the multiple input channels included in the above photovoltaic inverter 100 to the ground is less than the preset threshold, it is determined that single-channel insulation impedance detection needs to be performed. Among them, the preset threshold can be determined according to industry standards and specifications, and it is usually set within a safe range to ensure the reliability and safety of the system. And the specific detection method for the sum of the resistance values of the positive electrodes of the multiple input channels included in the above photovoltaic inverter 100 to the ground can refer to the prior art, so it will not be elaborated here.

[0081] In other examples, taking Figure 1Taking the circuit structure shown as an example, the resistance value of the overall insulation impedance can include the resistance value of the overall insulation positive impedance and the resistance value of the overall insulation negative impedance. Among them, the overall insulation positive impedance is the sum of the resistance values of the positive poles of the multiple input channels included in the above photovoltaic inverter 100 with respect to the common ground terminal PE, that is, the resistance value after the parallel connection of impedance RP1, impedance RP2, …, impedance RPn. The resistance value of the overall insulation negative impedance is the sum of the resistance values of the negative poles of the multiple input channels included in the above photovoltaic inverter 100 with respect to the common ground terminal PE, that is, the resistance value after the parallel connection of impedance RN1, impedance RN2, …, impedance RNn. Correspondingly, the above step S12 can specifically include: when the resistance value of the overall insulation positive impedance of the multiple input channels included in the above photovoltaic inverter 100 is less than the preset threshold, or the resistance value of the overall insulation negative impedance of the multiple input channels included in the above photovoltaic inverter 100 is less than the preset threshold, it is determined that single-channel insulation impedance detection needs to be performed. Among them, the preset threshold can be determined according to industry standards and specifications, and it is usually set within a safe range to ensure the reliability and safety of the system.

[0082] In some embodiments, as Figure 5 shown, before the above step S101, the insulation impedance detection method of the above photovoltaic inverter may further include:

[0083] Step S21. When receiving a single-channel insulation impedance detection instruction, it is determined that single-channel insulation impedance detection needs to be performed.

[0084] Among them, the single-channel insulation impedance detection instruction is used to indicate that single-channel insulation impedance detection needs to be performed, and this single-channel insulation impedance detection instruction can be input by the user through the virtual button or physical button of the photovoltaic inverter.

[0085] In the above embodiment, as Figure 6 shown, the above insulation impedance detection of the photovoltaic inverter may include:

[0086] Step S31. Control the insulation impedance detection circuit to be in the first detection state, and when the insulation impedance detection circuit is in the first detection state, collect the voltage between the common ground terminal and the negative bus to obtain the first voltage.

[0087] Specifically, taking the Figure 1 shown circuit structure as an example, the first controllable switch S1 can be controlled to conduct, and the second controllable switch S2 can be controlled to turn off to achieve controlling the insulation impedance detection circuit 10 to be in the first detection state. Then, when the insulation impedance detection circuit 10 is in the first detection state, the voltage between the common ground terminal PE and the negative bus BUS- can be detected through the voltage detection circuit 12 to obtain the first voltage.

[0088] Step S32. Control the insulation impedance detection circuit to be in the second detection state, and collect the voltage between the common ground terminal and the negative bus when the insulation impedance detection circuit is in the second detection state, to obtain a second voltage.

[0089] Specifically, taking Figure 1 the circuit structure shown as an example, the first controllable switch S1 can be controlled to turn off, and the second controllable switch S2 can be controlled to turn on, so as to control the insulation impedance detection circuit 10 to be in the second detection state. Then, when the insulation impedance detection circuit 10 is in the second detection state, the voltage between the common ground terminal PE and the negative bus BUS- can be detected through the voltage detection circuit 12 to obtain a second voltage.

[0090] Step S33. Calculate the resistance value of the insulation impedance according to the first voltage and the second voltage. The insulation impedance includes the insulation positive impedance of all input channels with open circuit between the positive electrode and the negative electrode.

[0091] Specifically, the above step S33 may include:

[0092] Step S1-1. Calculate the resistance value of the insulation positive impedance of all input channels with open circuit between the positive electrode and the negative electrode through a first calculation formula, where the first calculation formula is:

[0093]

[0094] where, U a and U b are the first voltage and the second voltage respectively, V2 is the voltage between the positive bus and the negative bus (i.e., the potential difference between the positive and negative buses), R aP and R bP are the resistance values of the first impedance and the third impedance respectively, R aN and R bN are the resistance values of the second impedance and the fourth impedance respectively; R eqP is the resistance value of the insulation positive impedance of all input channels with open circuit between the positive electrode and the negative electrode, and V eq is the equivalent voltage on the positive electrode of all input channels with open circuit between the positive electrode and the negative electrode.

[0095] Specifically, taking Figure 1 the circuit structure shown as an example, R aP is equal to the resistance value of the first detection resistor R1, R bP is equal to the sum of the resistance values of the first detection resistor R1 and the second detection resistor R2, R aN is equal to the sum of the resistance values of the third detection resistor R3 and the fourth detection resistor R4, R bN is equal to the resistance value of the third detection resistor R3. R eqP is the resistance value of the insulation positive impedance of all input channels with open circuit between the positive electrode and the negative electrode, and V eqThe equivalent voltage on the positive electrode of all input channels where the positive electrode is open - circuited from the negative electrode.

[0096] And, in specific implementation, V eq can specifically be the voltage on the positive electrode of the input channel with the highest voltage on the positive electrode among the multiple input channels included in the above - mentioned photovoltaic inverter 100, or can specifically be the voltage on the positive electrode of the wake - up channel with the lowest voltage on the positive electrode among the multiple input channels included in the above - mentioned photovoltaic inverter 100, where the wake - up channel is an input channel with the voltage on the positive electrode greater than or equal to the wake - up voltage of the above - mentioned photovoltaic inverter 100.

[0097] In some embodiments, in the above step S33, the resistance value of the insulation impedance calculated based on the first voltage and the second voltage can also include the value of the parallel connection of the insulation positive impedance of all input channels where the positive electrode is short - circuited to the negative electrode and the insulation negative impedance of the whole of the multiple input channels included in the photovoltaic inverter. Correspondingly, the above step S33 can also include:

[0098] Step S1 - 2. Calculate the value of the parallel connection of the insulation positive impedance of all input channels where the positive electrode is short - circuited to the negative electrode and the insulation negative impedance of the whole of the multiple input channels through a second calculation formula, where the second calculation formula is:

[0099]

[0100] where, R eqN is the value of the parallel connection of the insulation positive impedance of all input channels where the positive electrode is short - circuited to the negative electrode and the insulation negative impedance of the whole of the multiple input channels included in the photovoltaic inverter, and the explanations of other symbols in the second calculation formula except R eqN can refer to the explanations of the same symbols in the above - mentioned first calculation formula, so they will not be elaborated here.

[0101] And, for the sake of easy understanding, the following takes the Figure 1 shown circuit structure as an example to specifically illustrate the derivation processes of the above - mentioned first calculation formula and the second calculation formula. As Figure 1 shown, the first controllable switch S1 and the second controllable switch S2 have a total of four states. Taking two states (i.e., the first detection state where the first controllable switch S1 is on and the second controllable switch S2 is off and the second detection state where the first controllable switch S1 is off and the second controllable switch S2 is on), according to the node current equation, there can be the following two equalities:

[0102]

[0103] where, U a and U bThe voltages between the common ground terminal PE and the negative bus bar BUS- collected in the first detection state and the second detection state respectively; V eq The equivalent voltage on the positive poles of all input channels where the positive and negative poles are open; R eqP The resistance value of the equivalent insulation positive impedance of all input channels where the positive and negative poles are open; R eqN The resistance value of the equivalent insulation negative impedance after the parallel connection of the insulation positive impedance of all input channels where the positive and negative poles are short-circuited and the insulation negative impedance of the whole of multiple input channels included in the photovoltaic inverter; V2 is the voltage between the positive bus bar BUS+ and the negative bus bar BUS-; R aP R bP The resistance values of the impedances of the positive bus bar BUS+ to the common ground terminal PE in the first detection state and the second detection state respectively; R aN R bN The resistance values of the impedances of the negative bus bar BUS- to the common ground terminal PE in the first detection state and the second detection state respectively.

[0104] After transforming equations (1-1) and (1-2), we have:

[0105]

[0106] Subtracting equation (1-3) from equation (1-4) to eliminate V eq We have:

[0107]

[0108] After transforming equations (1-1) and (1-2) again, we have:

[0109]

[0110] Subtracting equation (1-6) from equation (1-7) to eliminate R eqN We have:

[0111]

[0112] Substituting equation (1-8) into equation (1-5), we get:

[0113]

[0114] In this way, we can obtain that equations (1-8) and (1-9) are the above-mentioned first calculation formula and the above-mentioned second calculation formula respectively.

[0115] Specifically, in the above step S102, after controlling the positive and negative poles of the target input channel to be open-circuited and controlling the positive and negative poles of the other input channels except the target input channel among the multiple input channels to be short-circuited, so that only the positive and negative poles of the target input channel are open-circuited among the multiple input channels included in the above photovoltaic inverter, by respectively executing the above step S31, the above step S32, and the above step S33 once, the detection result of the insulation positive impedance value of all the input channels with open-circuited positive and negative poles can be obtained, and all the input channels with open-circuited positive and negative poles are the target input paths. Therefore, the insulation positive impedance value of all the input channels with open-circuited positive and negative poles is the insulation positive impedance value of the target input path. Further, the detection result may further include the resistance value after the insulation positive impedance of all the input channels with short-circuited positive and negative poles is connected in parallel with the insulation negative impedance of the multiple input channels included in the photovoltaic inverter, and all the input channels with short-circuited positive and negative poles are the other input channels except the target input path among the multiple input channels included in the above photovoltaic inverter. Therefore, the resistance value after the insulation positive impedance of all the input channels with short-circuited positive and negative poles is connected in parallel with the insulation negative impedance of the multiple input channels included in the photovoltaic inverter is the resistance value after the insulation positive impedance of the other input channels except the target input path is connected in parallel with the insulation negative impedance of the multiple input channels included in the photovoltaic inverter.

[0116] Thus, in the above step S102, after controlling the positive and negative poles of the target input channel to be open-circuited and controlling the positive and negative poles of the other input channels except the target input channel among the multiple input channels to be short-circuited, so that only the positive and negative poles of the target input channel are open-circuited among the multiple input channels included in the above photovoltaic inverter, by respectively executing the above step S31, the above step S32, and the above step S33 once, the resistance value of the insulation positive impedance of the target input path can be obtained, thereby completing the detection of the insulation positive impedance of the target input channel.

[0117] Moreover, for the sake of easy understanding, the following takes Figure 1 the circuit structure shown as an example. Assume that the target input channel is the first input channel PV1. Then, after controlling the positive and negative poles of the target input channel to be open-circuited and controlling the positive and negative poles of the other input channels except the target input channel among the multiple input channels included in the above photovoltaic inverter 100 to be short-circuited, so that only the positive and negative poles of the target input channel are open-circuited among the multiple input channels included in the above photovoltaic inverter 100, there can be an equivalent circuit as Figure 7 shown. Specifically, in Figure 7Among them, the impedance Rp is the impedance of the positive bus bar BUS+ to the common ground terminal PE, the impedance Rn is the impedance of the negative bus bar BUS- to the common ground terminal PE, the impedance RP1 is the positive insulation impedance of the first input channel PV1, the impedance RP2 is the positive insulation impedance of the second input channel PV2,..., the impedance RPn is the positive insulation impedance of the nth input channel PVn; the impedance RN1 is the negative insulation impedance of the first input channel PV1, the impedance RN2 is the negative insulation impedance of the second input channel PV2,..., the impedance RNn is the negative insulation impedance of the nth input channel PNn, and the impedance RN is the total impedance after the parallel connection of the negative insulation impedances of the n input channels included in the above photovoltaic inverter 100, that is, the negative insulation impedance of the n input channels included in the above photovoltaic inverter 100 as a whole.

[0118] Specifically, in the above step S104 or the above step S1041, after opening the positive and negative poles of the control target input channel and the current detection input channel, and short-circuiting the positive and negative poles of the other input channels except the target input channel and the current detection input channel among the multiple input channels, so that only the positive and negative poles of the target input channel and the current detection input channel are open among the multiple input channels included in the above photovoltaic inverter, by respectively executing the above step S31, the above step S32, and the above step S33 once, the detection result of the resistance value of the positive insulation impedance of all the input channels with open positive and negative poles can be obtained, and all the input channels with open positive and negative poles are the target input path and the current detection input channel. Therefore, the resistance value of the positive insulation impedance of all the input channels with open positive and negative poles is the resistance value after the parallel connection of the positive insulation impedance of the target input path and the positive insulation impedance of the current detection input channel. Further, the detection result may further include the resistance value after the parallel connection of the positive insulation impedance of all the input channels with short-circuited positive and negative poles and the negative insulation impedance of the multiple input channels included in the photovoltaic inverter as a whole, and all the input channels with short-circuited positive and negative poles are the other input channels except the target input path and the current detection input channel among the multiple input channels included in the above photovoltaic inverter. Therefore, the resistance value after the parallel connection of the positive insulation impedance of all the input channels with short-circuited positive and negative poles and the negative insulation impedance of the multiple input channels included in the photovoltaic inverter as a whole is the resistance value after the parallel connection of the positive insulation impedance of the other input channels except the target input path and the current detection input channel and the negative insulation impedance of the multiple input channels included in the photovoltaic inverter as a whole; then, when the resistance value after the parallel connection of the two impedances (that is, the positive insulation impedance of the target input path and the positive insulation impedance of the current detection input channel) is known, and the resistance value of one of the two impedances (that is, the positive insulation impedance of the target input path) has been calculated through the previous steps, according to the parallel resistance value calculation formula of the two impedances, the resistance value of the other of the two impedances (that is, the positive insulation impedance of the current detection input path) can be calculated.

[0119] Thus, in the above step S104 or the above step S1041, after opening the positive and negative poles of the control target input channel and the current detection input channel, and shorting the positive and negative poles of the other input channels except the target input channel and the current detection input channel among the multiple input channels, so that only the positive and negative poles of the target input channel and the current detection input channel are open among the multiple input channels included in the above photovoltaic inverter, by respectively performing the above step S31, the above step S32, and the above step S33 once, the resistance value after the parallel connection of the insulation positive impedance of the target input path and the insulation positive impedance of the current detection input channel can be obtained. Furthermore, the resistance value of the insulation positive impedance of the current detection input channel can be calculated according to the resistance value calculation formula for the parallel connection of two impedances, thereby completing the detection of the insulation positive impedance of the current detection input channel.

[0120] Specifically, in the above step S11, when at least one of the multiple input channels included in the photovoltaic inverter reaches the wake-up voltage of the photovoltaic inverter, by respectively performing the above step S31, the above step S32, and the above step S33 once, the detection result of the resistance values of the insulation positive impedances of all the input channels with open positive and negative poles can be obtained, and all the input channels with open positive and negative poles are the multiple input channels included in the photovoltaic inverter. Therefore, the resistance values of the insulation positive impedances of all the input channels with open positive and negative poles are the overall insulation positive impedance of the multiple input channels included in the photovoltaic inverter. Further, the detection result may also include the resistance value after the parallel connection of the insulation positive impedance of all the input channels with shorted positive and negative poles and the overall insulation negative impedance of the multiple input channels included in the photovoltaic inverter. And there is no input channel with shorted positive and negative poles among the multiple input channels included in the photovoltaic inverter. Therefore, the resistance value after the parallel connection of the insulation positive impedance of all the input channels with shorted positive and negative poles and the overall insulation negative impedance of the multiple input channels included in the photovoltaic inverter is the overall insulation negative impedance of the multiple input channels included in the photovoltaic inverter.

[0121] Moreover, it should be noted that after completing the detection of the insulation positive impedance of each input channel among the multiple input channels included in the above photovoltaic inverter, when the resistance value after the parallel connection of the insulation positive impedance of the other input channels except the target input path and the overall insulation negative impedance of the multiple input channels included in the above photovoltaic inverter has been calculated through the previous steps, the overall insulation negative impedance of the multiple input channels included in the above photovoltaic inverter can be calculated according to the resistance value calculation formula for the parallel connection of multiple impedances, and the overall insulation negative impedance can be output to facilitate more accurate positioning of insulation faults.

[0122] As can be seen from the above, in the insulation impedance detection method of the photovoltaic inverter provided in this embodiment, when single-channel insulation impedance detection is required, the target input channel is determined from multiple input channels of the photovoltaic inverter. Then, the positive and negative poles of the target input channel are opened, and the positive and negative poles of the other input channels except the target input channel among the multiple input channels are short-circuited. Then, the insulation impedance of the photovoltaic inverter is detected to obtain a detection result including the value of the insulation positive impedance of the target input channel, so as to complete the detection of the insulation positive impedance of the target input channel. Next, the input channel to be detected among the multiple input channels is determined as the current detection input channel. Then, the positive and negative poles of the target input channel and the current detection input channel are opened, and the positive and negative poles of the other input channels except the target input channel and the current detection input channel among the multiple input channels are short-circuited. Then, the insulation impedance of the photovoltaic inverter is detected to obtain a detection result including the value of the parallel resistance of the insulation positive impedance of the target input channel and the insulation positive impedance of the current detection input channel, so as to complete the detection of the insulation positive impedance of the current detection input channel, and return to execute the step of determining the input channel to be detected among the multiple input channels as the current detection input channel until the detection of the insulation positive impedance of all the input channels to be tested is completed. Thus, the parallel transfer of the insulation positive impedance of some input channels is realized by the short-circuit method, and therefore, the insulation impedance of a single input channel of the photovoltaic inverter can be detected to facilitate the location and troubleshooting of faults.

[0123] This document provides various operations of the embodiments. In one embodiment, the one or more operations may constitute computer-readable instructions stored on one or more computer-readable media, which when executed by a computer device will cause the computing device to perform the operations. The order of describing some or all of the operations should not be construed as implying that these operations must be order-related. Those skilled in the art will understand alternative orderings that have the benefits of this specification. Moreover, it should be understood that not all operations are required to be present in each embodiment provided herein.

[0124] Moreover, although the present disclosure has been shown and described with respect to one or more implementations, equivalent variations and modifications will occur to those skilled in the art based on a reading and understanding of this specification and the drawings. The present disclosure includes all such modifications and variations and is limited only by the scope of the appended claims. In particular with respect to the various functions performed by the above-described components (e.g., elements, resources, etc.), the terms used to describe such components are intended to correspond to any component that performs the specified function of the component (e.g., it is functionally equivalent), unless otherwise indicated, even if it is not structurally equivalent to the disclosed structure that performs the functions in the exemplary implementations of the present disclosure shown herein. In addition, although a particular feature of the present disclosure has been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of other implementations as may be desired and advantageous for a given or particular application. Moreover, insofar as the terms "comprise", "have", "contain" or variations thereof are used in the detailed description or claims, such terms are intended to include in a manner similar to the term "include".

[0125] Each functional unit in the embodiments of the present invention may be integrated into a processing module, or each unit may exist physically alone, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. When the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium. The above-mentioned storage medium may be a read-only memory, a magnetic disk or an optical disc, etc. The above-mentioned various devices or systems may execute the methods in the corresponding method embodiments.

[0126] In summary, although the present invention has been disclosed as above with embodiments, the serial numbers before the embodiments are only used for convenience of description and do not limit the order of the embodiments of the present invention. Moreover, the above embodiments are not intended to limit the present invention, and those of ordinary skill in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention is subject to the scope defined by the claims.

Claims

1. A method for detecting insulation impedance of a photovoltaic inverter, characterized in that: The photovoltaic inverter has a plurality of input channels, and the plurality of input channels are respectively connected to a plurality of photovoltaic modules; The insulation impedance detection method comprises: When single-channel insulation impedance detection is required, determining a target input channel from the multiple input channels; Controlling the positive and negative poles of the target input channel to be disconnected, and controlling the positive and negative poles of other input channels except the target input channel among the multiple input channels to be short-circuited, and then performing insulation impedance detection on the photovoltaic inverter to obtain a detection result including the resistance value of the insulation positive impedance of the target input channel, so as to complete the detection of the insulation positive impedance of the target input channel; Determine an input channel to be detected from the multiple input channels as a current detection input channel; The positive and negative poles of the target input channel and the current detection input channel are controlled to be disconnected, and the positive and negative poles of other input channels except the target input channel and the current detection input channel among the multiple input channels are controlled to be short-circuited, and then the insulation impedance detection is performed on the photovoltaic inverter to obtain a detection result including the resistance value of the insulation positive impedance of the target input channel and the insulation positive impedance of the current detection input channel in parallel, so as to complete the detection of the insulation positive impedance of the current detection input channel, and return to execute the step of determining the input channel to be detected from the multiple input channels as the current detection input channel, until the detection of the insulation positive impedance of all input channels to be tested is completed.

2. The insulation impedance detection method according to claim 1, characterized in that: The photovoltaic inverter comprises a plurality of boost circuits, the plurality of boost circuits respectively corresponding to the plurality of input channels, and each of the boost circuits comprises a switch, and two ends of the switch are respectively connected to the positive electrode and the negative electrode of the corresponding input channel; The controlling of disconnecting the positive and negative electrodes of the target input channel, and controlling the short circuiting of the positive and negative electrodes of other input channels among the multiple input channels except the target input channel, includes: Controlling the switch of the boost circuit corresponding to the target input channel to be turned off, and controlling the switches of the boost circuit corresponding to other input channels among the multiple input channels except the target input channel to be turned on; The controlling of disconnecting the positive and negative electrodes of the target input channel and the current detection input channel, and controlling the short circuiting of the positive and negative electrodes of other input channels among the multiple input channels except the target input channel and the current detection input channel, comprises: The switches of the boost circuit corresponding to the target input channel and the current detection input channel are turned off, and the switches of the boost circuit corresponding to other input channels among the multiple input channels except the target input channel and the current detection input channel are turned on.

3. The insulation impedance detection method according to claim 1, characterized in that: The photovoltaic inverter comprises a positive bus and a negative bus; the insulation impedance detection method is applied to an insulation impedance detection circuit, the insulation impedance detection circuit is respectively connected to the positive bus, the negative bus and a common ground terminal; the insulation impedance detection circuit has a first detection state and a second detection state; Furthermore, when the insulation impedance detection circuit is in the first detection state, the impedance between the positive bus and the common ground terminal is a first impedance, and the impedance between the negative bus and the common ground terminal is a second impedance; when the insulation impedance detection circuit is in the second detection state, the impedance between the positive bus and the common ground terminal is a third impedance, and the impedance between the negative bus and the common ground terminal is a fourth impedance; The performing insulation impedance detection on the photovoltaic inverter comprises: controlling the insulation impedance detection circuit to be in the first detection state, and when the insulation impedance detection circuit is in the first detection state, collecting the voltage between the common ground terminal and the negative bus to obtain a first voltage; controlling the insulation impedance detection circuit to be in the second detection state, and when the insulation impedance detection circuit is in the second detection state, collecting the voltage between the common ground terminal and the negative bus to obtain a second voltage; The insulation impedance value is calculated according to the first voltage and the second voltage, and the insulation impedance value includes the insulation positive impedance value of all input channels with the positive and negative electrodes disconnected.

4. The insulation impedance detection method according to claim 3, characterized in that: The insulation impedance detection circuit comprises a first detection resistor, a second detection resistor, a third detection resistor, a fourth detection resistor, a first controllable switch and a second controllable switch, wherein the first detection resistor, the second detection resistor, the third detection resistor and the fourth detection resistor are connected in series in sequence, a non-series connection end of the first detection resistor is connected to the positive bus, a connection end between the first detection resistor and the second detection resistor is connected to a first end of the first controllable switch, a connection end between the second detection resistor and the third detection resistor and a second end of the first controllable switch are both connected to the common ground end, a connection end between the third detection resistor and the fourth detection resistor is connected to a first end of the second controllable switch, and a non-series connection end of the fourth detection resistor and a second end of the second controllable switch are both connected to the negative bus; The controlling the insulation impedance detection circuit to be in a first detection state includes: Controlling the first controllable switch to be turned on, and controlling the second controllable switch to be turned off, and the resistance value of the first impedance is equal to the resistance value of the first detection resistor, and the resistance value of the second impedance is equal to the sum of the resistance values ​​of the third detection resistor and the fourth detection resistor; The controlling the insulation impedance detection circuit to be in a second detection state includes: The first controllable switch is controlled to be turned off, and the second controllable switch is controlled to be turned on, and the resistance value of the third impedance is equal to the sum of the resistance values ​​of the first detection resistor and the second detection resistor, and the resistance value of the fourth impedance is equal to the resistance value of the third detection resistor.

5. The insulation impedance detection method according to claim 3, characterized in that: The step of calculating the insulation impedance value according to the first voltage and the second voltage includes: The insulation positive impedance of all input channels with the positive and negative electrodes disconnected is calculated by a first calculation formula, wherein the first calculation formula is: Among them, U a , U b are the first voltage and the second voltage respectively, V2 is the voltage between the positive bus and the negative bus, R aP and R bP are the resistance values ​​of the first impedance and the third impedance respectively, R aN , R bN are the resistance values ​​of the second impedance and the fourth impedance respectively; R eqP is the insulation positive impedance value of all input channels with the positive and negative electrodes disconnected, V eq It is the equivalent voltage on the positive electrodes of all input channels with the positive and negative electrodes disconnected.

6. The insulation impedance detection method according to claim 3, characterized in that: The insulation impedance also includes the insulation positive impedance of all input channels with positive and negative electrodes short-circuited in parallel with the insulation negative impedance of the plurality of input channels as a whole; The step of calculating the insulation impedance value according to the first voltage and the second voltage includes: The resistance value of the insulation positive impedance of all input channels with the positive and negative electrodes short-circuited in parallel with the insulation negative impedance of the multiple input channels as a whole is calculated by a second calculation formula, wherein the second calculation formula is: Among them, U a , U b are the first voltage and the second voltage respectively, V2 is the voltage between the positive bus and the negative bus, R aP and R bP are the resistance values ​​of the first impedance and the third impedance respectively, R aN , R bN are the resistance values ​​of the second impedance and the fourth impedance respectively; R eqN V is the resistance value of the insulation positive impedance of all input channels with the positive and negative electrodes short-circuited in parallel with the insulation negative impedance of the plurality of input channels as a whole, eq It is the equivalent voltage on the positive electrodes of all input channels with the positive and negative electrodes disconnected.

7. The insulation impedance detection method according to claim 1, characterized in that: Before determining the target input channel from the multiple input channels, the method further includes: When at least one of the multiple input channels reaches the wake-up voltage of the photovoltaic inverter, the insulation impedance value of the multiple input channels as a whole is detected, and when the insulation impedance value of the multiple input channels as a whole is less than a preset threshold, it is determined that single-channel insulation impedance detection is required; or, When a single-channel insulation impedance detection instruction is received, it is determined that a single-channel insulation impedance detection needs to be performed.

8. The insulation impedance detection method according to claim 1, characterized in that: The step of determining a target input channel from the plurality of input channels comprises: Determine, from the multiple input channels, an input channel with the highest voltage on the positive electrode as a target input channel; Determining the input channel to be detected from the multiple input channels as the current detection input channel; The input channel to be detected with the highest voltage on the positive electrode is determined from the multiple input channels as the current detection input channel.

9. An insulation impedance detection circuit for a photovoltaic inverter, characterized in that: It comprises a control processing unit, and the control processing unit is used to execute the steps in the insulation impedance detection method according to any one of claims 1 to 8.

10. A photovoltaic inverter, characterized in that: The invention comprises the insulation impedance detection circuit as claimed in claim 9.

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