Impedance detection circuit and method, inverter and photovoltaic power generation system

Abstract

The invention discloses an impedance detection circuit and method, an inverter and a photovoltaic power generation system, and relates to the technical field of computers. The impedance detection circuit comprises an anode load circuit, a cathode load circuit and a controller; the controller is connected with a parallel node of the positive load circuit and the negative load circuit, the first switch and the second switch, and the controller is used for collecting first voltage data under the condition that the first switch is switched on and the second switch is switched off; acquiring second voltage data under the condition that the first switch and the second switch are switched on; an impedance detection result is determined based on the first voltage data and the second voltage data. The impedance detection circuit is controlled to be in different connection states through accurate operation of the controller on switches in different load circuits, so that the first voltage data and the second voltage data are respectively acquired in different circuit connection states, and accurate impedance detection is realized.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of computer technology, and in particular to an impedance detection circuit, method, inverter, and photovoltaic power generation system. Background Art

[0002] As a key device in photovoltaic power generation systems, microinverters usually refer to inverters with a power of less than or equal to 1000 watts and component-level MPPT (Maximum Power Point Tracking) function.

[0003] In related technologies, insulation resistance is a key parameter to measure the insulation performance of electrical equipment or circuits to the ground. For the inverter in the photovoltaic power generation system, the insulation resistance of its photovoltaic (PV) port to the ground has an even more important influence. The level of insulation resistance is directly related to the safety and stability of the inverter operation.

[0004] When the insulation impedance to ground of the PV+ (positive power supply) or PV- (negative power supply) port in the inverter is reduced, it may cause abnormalities in the internal circuit of the inverter and even cause leakage to the ground, which will not only damage the inverter itself but also pose a serious threat to personal safety. Therefore, how to accurately detect the insulation impedance in the inverter has become a problem that needs to be solved urgently. Summary of the invention

[0005] The embodiment of the present application provides an impedance detection circuit, method, inverter and photovoltaic power generation system, and the technical solution is as follows:

[0006] In one aspect, an impedance detection circuit is provided, the circuit comprising a positive load circuit, a negative load circuit and a controller;

[0007] The positive load circuit and the negative load circuit are connected in parallel to the protective grounding PE terminal, and the positive load circuit is connected to the positive electrode of the power supply, and the negative load circuit is grounded; the positive load circuit includes a first load, a second load and a first switch, and the negative load circuit includes a third load, a fourth load and a second switch;

[0008] The first end of the first load is connected to the first end of the third load; the first end of the first load is connected to the PE end; the second end of the first load is connected to the first switch; the first end of the second load is connected to the first switch; the second end of the third load is connected to the second switch, the first end of the fourth load is connected to the second switch; the second end of the second load is connected to the second end of the fourth load;

[0009] The controller is respectively connected to the parallel node of the positive load circuit and the negative load circuit, the first switch, and the second switch. The controller is used to: collect first voltage data when the first switch is turned on and the second switch is turned off; collect second voltage data when the first switch and the second switch are turned on; and determine the impedance detection result based on the first voltage data and the second voltage data.

[0010] In some embodiments, the second end of the first load is connected to the first static contact of the first switch; the first end of the second load is connected to the first moving contact of the first switch; the second end of the third load is connected to the second moving contact of the second switch, and the first end of the fourth load is connected to the second static contact of the second switch.

[0011] In some embodiments, the circuit also includes a grounded load circuit; the grounded load circuit includes a fifth load and a sixth load; the first end of the fifth load is connected to the first end of the sixth load; the second end of the fifth load is connected to the second end of the second load; the second end of the sixth load is grounded; and the second end of the fifth load is connected to the controller.

[0012] In some embodiments, when the first switch is turned on and the second switch is turned off, the circuit includes the following loop:

[0013] a first loop, in which current flows from the first load to the third load;

[0014] a second loop, in which current flows from the first load to the fifth load, and from the fifth load to the sixth load;

[0015] a third loop, in which current flows from the second load to the third load;

[0016] A fourth loop, in which current flows from the second load to the fifth load, and from the fifth load to the sixth load.

[0017] In some embodiments, when the first switch and the second switch are turned on, the circuit includes the following loop:

[0018] a first loop, in which current flows from the first load to the third load;

[0019] a second loop, in which current flows from the first load to the fifth load, and from the fifth load to the sixth load;

[0020] a third loop, in which current flows from the second load to the third load;

[0021] a fourth loop, in which current flows from the second load to the fifth load, and from the fifth load to the sixth load;

[0022] a fifth loop, in which current flows from the first load to the fourth load;

[0023] A sixth loop, in which current flows from the second load to the fourth load.

[0024] In some embodiments, the circuit further includes at least one diode, and the positive load circuit is connected to the at least one diode.

[0025] On the other hand, an impedance detection method is provided, which is applied to the impedance detection circuit as described above and is executed by a controller in the impedance detection circuit. The method includes:

[0026] Acquire a first voltage value corresponding to the positive electrode of the power supply of the impedance detection circuit in a first connected state, and a second voltage value corresponding to the protective ground PE terminal; the first connected state is used to indicate a state in which the first switch in the impedance detection circuit is turned on and the second switch is turned off;

[0027] Acquire a third voltage value corresponding to the positive electrode of the power supply of the impedance detection circuit in a second connected state, and a fourth voltage value corresponding to the PE terminal; the second connected state is used to indicate a state in which the first switch and the second switch are turned on;

[0028] Based on the first voltage value, the second voltage value, the third voltage value and the fourth voltage value, an impedance detection result is determined, and the impedance detection result includes at least one of the insulation impedance of the positive pole of the power supply to the ground in the impedance detection circuit and the insulation impedance of the negative pole of the power supply to the ground in the impedance detection circuit.

[0029] On the other hand, an impedance detection device is provided, which is applied to the impedance detection circuit as described above, and the device comprises:

[0030] An acquisition module, used to acquire a first voltage value corresponding to the positive electrode of the power supply of the impedance detection circuit in a first connected state, and a second voltage value corresponding to the protective ground PE terminal; the first connected state is used to indicate a state in which the first switch in the impedance detection circuit is turned on and the second switch is turned off;

[0031] The acquisition module is used to acquire a third voltage value corresponding to the positive electrode of the power supply of the impedance detection circuit in a second connected state, and a fourth voltage value corresponding to the PE terminal; the second connected state is used to indicate a state in which the first switch and the second switch are turned on;

[0032] A processing module is used to determine an impedance detection result based on the first voltage value, the second voltage value, the third voltage value and the fourth voltage value, wherein the impedance detection result includes at least one of the insulation impedance of the positive pole of the power supply to the ground in the impedance detection circuit and the insulation impedance of the negative pole of the power supply to the ground in the impedance detection circuit.

[0033] On the other hand, an inverter is provided, wherein the inverter comprises the impedance detection circuit as described above, and the inverter is used to execute the impedance detection method as described above.

[0034] On the other hand, a photovoltaic power generation system is provided, wherein the photovoltaic power generation system comprises an inverter, wherein the inverter comprises the impedance detection circuit as described above, and the inverter is used to execute the impedance detection method as described above.

[0035] On the other hand, a computer-readable storage medium is provided, wherein at least one instruction, at least one program, a code set or an instruction set is stored in the storage medium, and the at least one instruction, the at least one program, the code set or the instruction set is loaded and executed by a processor to implement any of the above-mentioned impedance detection methods.

[0036] On the other hand, a computer program product or a computer program is provided, the computer program product or the computer program comprising computer instructions, the computer instructions being stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device performs any of the above-mentioned impedance detection methods.

[0037] The beneficial effects brought by the technical solution provided by the embodiment of the present application include at least:

[0038] An impedance detection circuit is designed, in which a positive load circuit and a negative load circuit are connected in parallel to a PE terminal, a controller is connected to the parallel node of the circuit, and the impedance detection circuit is controlled to be in different connection states by the controller's precise operation of switches in different load circuits, thereby respectively collecting first voltage data and second voltage data in different circuit connection states to achieve accurate impedance detection. In addition, the controller can automatically control switches in different load circuits to switch the circuit connection state, realize automatic impedance detection, avoid the process of manually adjusting the circuit connection state, and improve the efficiency and accuracy of impedance detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 is a structural schematic diagram of an impedance detection circuit provided by an exemplary embodiment of the present application;

[0041] Figure 2 is a schematic diagram of the structure of a switch provided by an exemplary embodiment of the present application;

[0042] Figure 3 is a structural schematic diagram of an impedance detection circuit provided by another exemplary embodiment of the present application;

[0043] Figure 4 is a structural schematic diagram of an equivalent circuit provided by an exemplary embodiment of the present application;

[0044] Figure 5 is a structural schematic diagram of an equivalent circuit provided by another exemplary embodiment of the present application;

[0045] Figure 6 is a structural schematic diagram of an impedance detection circuit provided by another exemplary embodiment of the present application;

[0046] Figure 7 is a flow chart of an impedance detection method provided by an exemplary embodiment of the present application;

[0047] Figure 8 is a schematic diagram of a control signal provided by an exemplary embodiment of the present application;

[0048] Fig. 9 is a schematic diagram of a control signal provided by yet another exemplary embodiment of the present application;

[0049] Fig.10 is a schematic diagram of a control signal provided by another exemplary embodiment of the present application;

[0050] Fig.11 is a schematic diagram of an impedance detection process provided by an exemplary embodiment of the present application;

[0051] Fig.12 is a structural schematic diagram of an inverter provided by an exemplary embodiment of the present application;

[0052] Fig.13 Schematic diagram of a photovoltaic power generation system provided by an exemplary embodiment of the present application. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the present application clearer, the implementation mode of the present application will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are 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 ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0054] In the present application, the terms "first", "second", etc. are used to distinguish identical or similar items with substantially the same effects and functions. It should be understood that there is no logical or temporal dependency between "first" and "second", nor are there any limitations on quantity and execution order.

[0055] First, the impedance detection circuit provided in the embodiment of the present application is introduced.

[0056] Figure 1 Schematic diagram of an impedance detection circuit provided by an embodiment of the present disclosure. Figure 1 As shown, the impedance detection circuit 100 includes: a positive load circuit 110 , a negative load circuit 120 and a controller 130 .

[0057] The positive load circuit 110 and the negative load circuit 120 are connected in parallel to a protective earth (PE) terminal, and the positive load circuit 110 is connected to a positive electrode V+ of a power source, while the negative load circuit 120 is grounded.

[0058] Optionally, the negative load circuit 120 is grounded, which means that the negative load circuit 120 is connected to a ground (GND) terminal, wherein the GND terminal is the negative electrode V- of the power supply; or, the GND terminal is connected to the negative electrode V- of the power supply.

[0059] The PE terminal ensures the safe operation of the circuit by connecting to the ground.

[0060] The GND terminal is usually used as a reference potential point to define a reference benchmark for voltage and current. In some embodiments, the GND terminal recorded in the embodiments of the present disclosure may also be replaced by other power terminals that can provide lower potential signals, such as a pull-down power supply VSS (Voltage Source and Sink) terminal.

[0061] It should be noted that the impedance detection circuit in the embodiment of the present disclosure is mainly used to calculate the insulation impedance of the positive pole V+ of the power supply to the ground, and / or the insulation impedance of the negative pole V- of the power supply to the ground, wherein the insulation impedance of the positive pole V+ of the power supply to the ground refers to the insulation impedance of the positive pole V+ of the power supply to the PE end, and the insulation impedance of the negative pole V- of the power supply to the ground refers to the insulation impedance of the negative pole V- of the power supply to the PE end.

[0062] The positive load circuit 110 includes a first load R1, a second load R2 and a first switch Q1, and the negative load circuit 120 includes a third load R3, a fourth load R4 and a second switch Q2.

[0063] The first load R1 is used to indicate the equivalent insulation impedance of the positive power supply V+ to the PE terminal, and the third load R3 is used to indicate the equivalent insulation impedance of the negative power supply V- to the PE terminal. Schematically, the first load R1 can be implemented as a first resistor R1, and the third load R3 can be implemented as a third resistor R3.

[0064] The second load R2 is a load in the positive load circuit 110, and the fourth load R4 is a load in the negative load circuit 120. The second load R2 and the fourth load R4 can be resistors, heating plates, etc., and the following mainly describes that the second load R2 is implemented as the second resistor R2 and the fourth load R4 is implemented as the fourth resistor R4. In the embodiment of the present disclosure, the resistance values ​​of the second resistor R2 and the fourth resistor R4 are known, and optionally, the resistance value of the second resistor R2 is equal to the resistance value of the fourth resistor R4.

[0065] The first switch Q1 and the second switch Q2 can be implemented as at least one of a mechanical switch and an electronic switch, which are not limited here. A mechanical switch realizes the on-off of a circuit through physical contact; an electronic switch realizes the on-off of a circuit through electronic components (such as transistors, etc.).

[0066] Combine the following Figure 1 The connection relationship of each component in the impedance detection circuit 100 is described as follows:

[0067] In the positive load circuit 110:

[0068] The first end a1 of the first load R1 is connected to the PE end; the second end b1 of the first load R1 is connected to the first switch Q1, wherein the second end b1 of the first load R1 is connected to the first output end out1 of the positive electrode V+ of the power supply, that is, the current flows from the positive electrode V+ of the power supply to the first load R1, and the first switch Q1 is connected to the second output end out2 of the positive electrode V+ of the power supply, that is, the current flows from the positive electrode V+ of the power supply to the first switch Q1; the first end a2 of the second load R2 is connected to the first switch Q1; the second end b2 of the second load R2 is connected to the first end a1 of the first load R1.

[0069] In the negative load circuit 120:

[0070] The first end a1 of the first load R1 is connected to the first end a3 of the third load R3 , and the second end b2 of the second load R2 is connected to the second end b4 of the fourth load R4 .

[0071] A first end a3 of the third load R3 is connected to the PE end; a second end b3 of the third load R3 is connected to the second switch Q2, wherein the second end b3 of the third load R3 is connected to the GND end (or the negative power supply electrode V-), that is, the current flows from the second end b3 of the third load R3 to the GND end (or the negative power supply electrode V-), and the second switch Q2 is connected to the GND end (or the negative power supply electrode V-), that is, the current flows from the second switch Q2 to the GND end (or the negative power supply electrode V-); a first end a4 of the fourth load R4 is connected to the second switch Q2, and a second end b4 of the fourth load R4 is connected to the first end a3 of the third load R3.

[0072] For controller 130:

[0073] The controller 130 is connected to the parallel node of the positive load circuit 110 and the negative load circuit 120, such as Figure 1 As shown, the first control terminal c1 of the controller 130 is connected to the second terminal b2 of the second load R2, and the first control terminal c1 of the controller 130 is connected to the second terminal b4 of the fourth load R4. Optionally, the first control terminal c1 of the controller 130 is connected to the parallel node between the second terminal b2 of the second load R2 and the second terminal b4 of the fourth load R4.

[0074] The controller 130 is connected to the first switch Q1 and the second switch Q2 respectively. The controller 130 is used to control the first switch Q1 to be turned on or off. The controller 130 is used to control the second switch Q2 to be turned on or off. Figure 1 As shown, the second control terminal c2 of the controller 130 is connected to the first switch Q1, and the third control terminal c3 of the controller 130 is connected to the second switch Q2.

[0075] The controller 130 is used to: collect first voltage data when the first switch Q1 is turned on and the second switch Q2 is turned off; collect second voltage data when the first switch Q1 and the second switch Q2 are turned on; and determine the impedance detection result based on the first voltage data and the second voltage data.

[0076] Here, conduction means that current can flow through the switch, for example, conduction of the first switch Q1 means that current can flow through the first switch Q1; and off means that current cannot flow through the switch, for example, off of the first switch Q1 means that current cannot flow through the first switch Q1.

[0077] In some embodiments, the first voltage data includes voltage data of the positive electrode V+ of the power supply and voltage data of the PE terminal; the second voltage data includes voltage data of the positive electrode V+ of the power supply and voltage data of the PE terminal. The impedance detection result includes at least one of the insulation impedance of the positive electrode V+ of the power supply to the PE terminal and the insulation impedance of the negative electrode V- of the power supply to the PE terminal.

[0078] In the embodiment of the present disclosure, the first load R1 is used to indicate the equivalent insulation impedance of the positive electrode V+ of the power supply to the PE end, and the third load R3 is used to indicate the equivalent insulation impedance of the negative electrode V- of the power supply to the PE end. That is, the load value of the first load R1 is used to indicate the insulation impedance of the positive electrode V+ of the power supply to the PE end, and the load value of the third resistor R3 is used to indicate the insulation impedance of the negative electrode V- of the power supply to the PE end.

[0079] It should be noted that in the embodiment of the present disclosure, the load values ​​of the first load R1 and the third load R3 are unknown. The controller 130 detects the load value of the first load R1 as the insulation impedance between the positive electrode V+ of the power supply and the PE end, and detects the load value of the third load R3 as the insulation impedance between the negative electrode V- of the power supply and the PE end.

[0080] Optionally, after obtaining the first voltage data and the second voltage data, the controller 130 determines the load value of the first load R1 (such as the resistance value of the first resistor) as the insulation impedance between the positive electrode V+ of the power supply and the PE end based on the first voltage data and the second voltage data; and / or determines the load value of the third load R3 (such as the resistance value of the third resistor) as the insulation impedance between the negative electrode V- of the power supply and the PE end based on the first voltage data and the second voltage data.

[0081] For the first switch Q1 and the second switch Q2:

[0082] 1. The first switch Q1 and the second switch Q2 are implemented as mechanical switches.

[0083] like Figure 1 As shown, the first end a1 of the first load R1 is connected to the first static contact e1 of the first switch Q1; the first end a2 of the second load R2 is connected to the first moving contact e2 of the first switch Q1. The first static contact e1 of the first switch Q1 is connected to the second output end out2 of the positive electrode V+ of the power supply, that is, the current flows from the positive electrode V+ of the power supply to the first static contact e1 of the first switch Q1.

[0084] The controller 130 may be connected to one end of the first static contact e1 of the first switch Q1, or to one end of the first moving contact e2. The controller 130 controls the first static contact e1 to connect with the first moving contact e2, so that the first switch Q1 is turned on, and controls the first static contact e1 to disconnect with the first moving contact e2, so that the first switch Q1 is turned off.

[0085] like Figure 2 As shown, the second end b3 of the third load R3 is connected to the second moving contact e3 of the second switch Q2, and the first end a4 of the fourth load R4 is connected to the second static contact e4 of the second switch Q2. The second moving contact e3 of the second switch Q2 is connected to the GND end (or the negative electrode V- of the power supply), that is, the current flows from the second moving contact e3 of the second switch Q2 to the GND end (or the negative electrode V- of the power supply).

[0086] The controller 130 may be connected to one end of the second moving contact e3 of the second switch Q2, or to one end of the second stationary contact e4. The controller 130 controls the second moving contact e3 to connect with the second stationary contact e4, so that the second switch Q2 is turned on, and controls the second moving contact e3 to disconnect with the second stationary contact e4, so that the second switch Q2 is turned off.

[0087] 2. The first switch Q1 and the second switch Q2 are implemented as electronic switches.

[0088] The following description will be made by taking the first switch Q1 and the second switch Q2 as transistors as an example.

[0089] Optionally, in the disclosed embodiment, the transistor may be a triode (Bipolar Transistor, also known as a bipolar junction transistor), or a field effect transistor (such as a metal oxide semiconductor tube, Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET), and the application does not limit the type of transistor. The following mainly takes the first switch Q1 and the second switch Q2 as a triode as an example for explanation, and the three electrodes of the triode are a base (Base, B), an emitter (Emitter, E) and a collector (Collector, C).

[0090] Among them, transistors can be divided into N-type transistors and P-type transistors. For triodes, N-type transistors are also called NPN-type transistors. When NPN-type transistors are used as switches: when the base voltage reaches or exceeds a certain threshold, the transistor is turned on (that is, the switch is turned on); when the base voltage is lower than the threshold, the transistor is cut off (that is, the switch is turned off). P-type transistors are also called PNP-type transistors. When PNP-type transistors are used as switches: when the base voltage drops below a certain threshold, the transistor is turned on (that is, the switch is turned on); when the base voltage is higher than the threshold, the transistor is cut off (that is, the switch is turned off).

[0091] In some embodiments, the first switch Q1 can be implemented as an N-type transistor or a P-type transistor; the second switch Q2 can be implemented as an N-type transistor or a P-type transistor, which is not limited in the present application.

[0092] Schematically, the first switch Q1 and the second switch Q2 are both NPN transistors. Figure 2 As shown, Figure 1 The first switch Q1 shown can also be implemented as Figure 2 An NPN transistor 200 is shown.

[0093] The first electrode (i.e., base electrode B) of the first switch Q1 is connected to the second control terminal c2 of the controller 130, the second electrode (i.e., collector electrode C) of the first switch Q1 is connected to the first terminal a1 of the first load R1, and the third electrode (i.e., emitter electrode E) of the first switch Q1 is connected to the first terminal a1 of the first load R1. The second electrode (i.e., collector electrode C) of the first switch Q1 is connected to the second output terminal out2 of the positive electrode V+ of the power supply, that is, the current flows from the positive electrode V+ of the power supply to the second electrode (i.e., collector electrode C) of the first switch Q1.

[0094] The controller 130 controls the voltage of the first electrode of the first switch Q1 to be greater than or equal to the first threshold through the second control terminal c2 to control the first switch Q1 to be turned on, and controls the voltage of the first electrode of the first switch Q1 to be less than the first threshold through the second control terminal c2 to control the first switch Q1 to be turned off.

[0095] Figure 1 The second switch Q2 shown can also be implemented as Figure 2 An NPN transistor 200 is shown.

[0096] The first electrode (i.e., base electrode B) of the second switch Q2 is connected to the third control terminal c3 of the controller 130, the second electrode (i.e., collector electrode C) of the second switch Q2 is connected to the first terminal a4 of the fourth load R4, and the third electrode (i.e., emitter electrode E) of the second switch Q2 is connected to the second terminal b3 of the third load R3. The third electrode (i.e., emitter electrode E) of the second switch Q2 is connected to the GND terminal (or the negative electrode V- of the power supply), that is, the current flows from the third electrode (i.e., emitter electrode E) of the second switch Q2 to the GND terminal (or the negative electrode V- of the power supply).

[0097] The controller 130 controls the voltage of the first electrode of the second switch Q2 to be greater than or equal to the second threshold value through the third control terminal c3 to control the second switch Q2 to be turned on, and controls the voltage of the first electrode of the second switch Q2 to be less than the second threshold value through the third control terminal c3 to control the second switch Q2 to be turned off. The first threshold value and the second threshold value may be the same or different.

[0098] It should be noted that the above examples of the first switch Q1 and the second switch Q2 are only for illustrative purposes and are not limited in the embodiments of the present application.

[0099] In summary, the embodiment of the present application designs an impedance detection circuit, wherein the positive load circuit and the negative load circuit are connected in parallel to the PE terminal, and the controller is connected to the parallel node of the circuit. The controller precisely operates the switches in different load circuits to control the impedance detection circuit to be in different connection states, thereby respectively collecting the first voltage data and the second voltage data in different circuit connection states to achieve accurate impedance detection. In addition, the controller can automatically control the switches in different load circuits to switch the connection state of the circuit, realize automatic impedance detection, avoid the process of manually adjusting the circuit connection state, and improve the efficiency and accuracy of impedance detection.

[0100] Optional, Figure 3 is a schematic diagram of another impedance detection circuit provided by an embodiment of the present disclosure. Figure 3 As shown, the impedance detection circuit 100 further includes a grounded load circuit 140 .

[0101] The ground load circuit 140 includes a fifth load R5 and a sixth load R6.

[0102] The first end a5 of the fifth load R5 is connected to the first end a6 of the sixth load R6.

[0103] The second end b5 of the fifth load R5 is connected to the second end b2 of the second load R2; the second end b5 of the fifth load R5 is connected to the second end b4 of the fourth load. Optionally, the second end b5 of the fifth load R5 is connected to the parallel node between the second end b2 of the second load R2 and the second end b4 of the fourth load R4.

[0104] The second end b6 of the sixth load R6 is connected to the GND end (or the negative power supply electrode V−), that is, the current flows from the second end b6 of the sixth load R6 to the GND end (or the negative power supply electrode V−).

[0105] Among them, the second end b6 of the sixth load R6 is connected to the second switch Q2. Schematically, if the second switch Q2 is a mechanical switch, the second end b6 of the sixth load R6 is connected to the second moving contact e3 of the second switch Q2; if the second switch Q2 is an NPN transistor, the second end b6 of the sixth load R6 is connected to the third pole (i.e., the emitter E) of the second switch Q2.

[0106] The second end b5 of the fifth load R5 is connected to the controller 130. Illustratively, the second end b5 of the fifth load R5 is connected to the first control end c1 of the controller 130.

[0107] The fifth load R5 and the sixth load R6 may be resistors, heating plates, etc., and the following description will be mainly based on the fifth load R5 being implemented as a fifth resistor R5 and the sixth load R6 being implemented as a sixth resistor R6.

[0108] In the embodiment of the present disclosure, the resistance values ​​of the fifth resistor R5 and the sixth resistor R6 are known, and the above-mentioned second resistor R1, second resistor R2, fifth resistor R5 and sixth resistor R6 are pre-set resistors, which are not limited in the embodiment of the present application. Schematically, the resistance value of the fifth resistor R5 is greater than the resistance value of the sixth resistor R6, the resistance value of the fifth resistor R5 is greater than the resistance value of the second resistor R2 and the resistance value of the fourth resistor R4, and the resistance value of the sixth resistor R6 is greater than the resistance value of the second resistor R2 and the resistance value of the fourth resistor R4.

[0109] In some embodiments, Figure 3 In the impedance detection circuit 100 shown, the controller 130 can control the states of the first switch Q1 and the second switch Q2. According to the states of the first switch Q1 and the second switch Q2, different loops exist in the impedance detection circuit 100. The loop conditions in the impedance detection circuit under different switch states are introduced below.

[0110] (1) When the first switch Q1 is turned on and the second switch Q2 is turned off, the impedance detection circuit 100 includes the following Loop:

[0111] The first loop, in which the current flows from the first load R1 to the third load R3; and from the third load R3 to the GND terminal (or the negative electrode V- of the power supply).

[0112] The second loop, in which the current flows from the first load R1 to the fifth load R5, from the fifth load R5 to the sixth load R6; and from the sixth load R6 to the GND terminal (or the negative electrode V- of the power supply).

[0113] The third loop, in which the current flows from the second load R2 to the third load R3; and from the third load R3 to the GND terminal (or the negative electrode V- of the power supply).

[0114] The fourth loop, in which the current flows from the second load R2 to the fifth load R5, and from the fifth load R5 to the sixth load R6; and from the sixth load R6 to the GND terminal (or the negative electrode V- of the power supply).

[0115] Based on the above circuit, schematically, please refer to Figure 4 , when the first switch Q1 is turned on and the second switch Q2 is turned off, the equivalent circuit of the impedance detection circuit 100 is shown in 400, wherein R1 and R2 are connected in parallel, R5 and R6 and R3 are connected in parallel, R1 and R3 are connected in series, R2 and R3 are connected in series, R1, R5 and R6 are connected in series, and R2, R5 and R6 are connected in series.

[0116] (2) When the first switch Q1 is turned on and the second switch Q2 is turned on, the impedance detection circuit 100 includes the following Loop:

[0117] The first loop, in which the current flows from the first load R1 to the third load R3; and from the third load R3 to the GND terminal (or the negative electrode V- of the power supply).

[0118] The second loop, in which the current flows from the first load R1 to the fifth load R5, from the fifth load R5 to the sixth load R6; and from the sixth load R6 to the GND terminal (or the negative electrode V- of the power supply).

[0119] The third loop, in which the current flows from the second load R2 to the third load R3; and from the third load R3 to the GND terminal (or the negative electrode V- of the power supply).

[0120] The fourth loop, in which the current flows from the second load R2 to the fifth load R5, and from the fifth load R5 to the sixth load R6; and from the sixth load R6 to the GND terminal (or the negative electrode V- of the power supply).

[0121] The fifth loop, in which the current flows from the first load R1 to the fourth load R4; and from the fourth load R4 to the GND terminal (or the negative electrode V- of the power supply).

[0122] The sixth loop, in which the current flows from the second load R2 to the fourth load R4; and from the fourth load R4 to the GND terminal (or the negative electrode V- of the power supply).

[0123] Based on the above circuit, schematically, please refer to Figure 5 , when the first switch Q1 is turned on and the second switch Q2 is turned on, the equivalent circuit of the impedance detection circuit 100 is shown in 500, wherein R1 and R2 are connected in parallel, R5 is connected in parallel with R6 and R3, R3 and R4 are connected in parallel, R5 is connected in parallel with R6 and R4, R1 and R3 are connected in series, R2 and R3 are connected in series, R1, R5 and R6 are connected in series, R2, R5 and R6 are connected in series, R1 and R4 are connected in series, and R2 and R4 are connected in series.

[0124] Based on the above introduction, optionally, Figure 3 The impedance detection circuit controller 130 shown is used to: when the first switch Q1 is turned on and the second switch Q2 is turned off, collect the voltage value of the positive electrode V+ of the power supply and the voltage value of the PE terminal as the first voltage data; when the first switch Q1 and the second switch Q2 are turned on, collect the voltage value of the positive electrode V+ of the power supply and the voltage value of the PE terminal as the second voltage data; based on the first voltage data, the second voltage data, the load value of the second load R2, the load value of the fourth load R4, the load value of the fifth load R5 and the load value of the sixth load R6, determine the load value of the first load R1 as the insulation impedance of the positive electrode V+ of the power supply to the PE terminal, and determine the load value of the third load R3 as the insulation impedance of the negative electrode V- of the power supply to the PE terminal.

[0125] Schematically, when the first switch Q1 is turned on and the second switch Q2 is turned off, according to Figure 4 The series-parallel relationship of the resistors in the equivalent circuit 400 shown, when the voltage value of the positive electrode V+ of the power supply, the voltage value of the PE terminal, the resistance value of the second resistor R2, the resistance value of the fifth resistor R5 and the resistance value of the sixth resistor R6 are known, the first current equivalent relationship is determined according to Kirchhoff's voltage and current law.

[0126] When the first switch Q1 is turned on and the second switch Q2 is turned on, according to Figure 5 The series-parallel relationship of the resistors in the equivalent circuit 500 shown, when the voltage value of the positive electrode V+ of the power supply, the voltage value of the PE terminal, the resistance value of the second resistor R2, the resistance value of the fourth resistor R4, the resistance value of the fifth resistor R5 and the resistance value of the sixth resistor R6 are known, the second current equivalent relationship is determined according to Kirchhoff's voltage and current law.

[0127] Finally, the resistance value of the first resistor R1 is determined as the insulation impedance of the positive electrode V+ of the power supply to the PE terminal according to the first current equivalent relationship and the second current equivalent relationship, and the resistance value of the third resistor R3 is determined as the insulation impedance of the negative electrode V- of the power supply to the PE terminal. The specific determination process can refer to the description of the impedance detection method in the following embodiment, which is not limited here.

[0128] In some embodiments, the impedance detection circuit 100 further includes: at least one diode, and the positive load circuit is connected to the at least one diode. The diode is used to be connected to the positive electrode of the power supply, and each diode is connected to a positive electrode V+ of the power supply.

[0129] A diode is an electronic device having two electrodes (positive and negative), wherein the negative terminal of at least one diode is connected to the positive load circuit, and the positive terminal of at least one diode is connected to the positive electrode V+ of the power supply, wherein the current flows from the positive terminal of the diode to the negative terminal, and then from the negative terminal to the positive load circuit 110.

[0130] Optionally, the cathode terminal of at least one diode is connected to the second end b1 of the first load R1 in the positive load circuit 110, and the current flows from the anode terminal of the diode to the cathode terminal, and then from the cathode terminal to the first load R1; the cathode terminal of at least one diode is connected to the first switch Q1, and the current flows from the anode terminal of the diode to the cathode terminal, and then from the cathode terminal to the first switch Q1.

[0131] In some embodiments, the impedance detection circuit 100 in the present application is used in an inverter in a photovoltaic power generation system, and the positive power supply V+ of the impedance detection circuit 100 refers to PV+, that is, the positive pole of the photovoltaic power supply; the negative power supply V- refers to PV-, that is, the negative pole of the photovoltaic power supply. Schematically, in a photovoltaic power generation system, the photovoltaic power supply is connected to the inverter through an MPPT (Maximum Power Point Tracking) controller, wherein the positive power supply PV+ of the photovoltaic power supply is connected to the diode in the impedance detection circuit 100 in the inverter through the MPPT controller. The negative power supply PV- of the photovoltaic power supply is connected to the GND terminal in the impedance detection circuit 100 in the inverter through the MPPT controller.

[0132] In some embodiments, there is an impedance detection circuit 100 connected to multiple power supplies, and the impedance detection circuit 100 includes multiple diodes, wherein each diode is connected to a positive electrode V+ of a power supply, and multiple power supplies are connected to a common negative electrode V- of the power supply, that is, the negative electrodes of the power supplies of multiple power supplies are connected to the same common negative electrode point (such as: GND terminal). Schematically, in a photovoltaic power generation system, multiple photovoltaic power supplies are connected to an inverter, each photovoltaic power supply corresponds to an MPPT controller, and multiple photovoltaic power supplies are connected to the impedance detection circuit 100 in the inverter through their respective corresponding MPPT controllers, wherein the positive electrodes PV+ of multiple power supplies are respectively connected to the impedance detection circuit 100 in the inverter, each positive electrode PV+ of the power supply is connected to a diode, and the positive electrodes PV- of multiple power supplies are commonly connected to the GND terminal in the impedance detection circuit 100 in the inverter.

[0133] The following description is made by taking the example that at least one diode includes a first diode and a second diode.

[0134] Optional, Figure 6 is a schematic diagram of another impedance detection circuit provided by an embodiment of the present disclosure. Figure 6 As shown, the impedance detection circuit 100 further includes: a first diode D1 and a second diode D2. The cathode terminal of the first diode D1 is connected to the positive load circuit; the cathode terminal of the second diode D2 is connected to the positive load circuit.

[0135] The positive terminal of the first diode D1 is connected to the positive electrode V1+ of the first power supply, and the positive terminal of the second diode D2 is connected to the positive electrode V2+ of the second power supply, wherein a seventh load R7 is included between the first diode D1 and the positive load circuit 110, and a seventh load R7 is included between the second diode D2 and the positive load circuit 110. The seventh load R7 can be a resistor, a heating plate, etc., which is not limited here.

[0136] In an embodiment of the present application, for the above-mentioned first voltage data, when the first switch Q1 is turned on and the second switch Q2 is turned off, the controller 130 collects the voltage value of the first positive power supply V1+ and the voltage value of the second positive power supply V2+, and takes the maximum value of the voltage value of the first positive power supply V1+ and the voltage value of the second positive power supply V2+ as the first voltage data.

[0137] For the above-mentioned second voltage data, when the first switch Q1 is turned on and the second switch Q2 is turned on, the controller 130 collects the voltage value of the first positive power supply V1+ and the voltage value of the second positive power supply V2+, and takes the maximum value of the voltage value of the first positive power supply V1+ and the voltage value of the second positive power supply V2+ as the second voltage data.

[0138] It needs to be explained that Figure 6 Only the case where two diodes are each connected to a power source is shown. In the embodiment of the present application, the number of diodes in the impedance detection circuit 100 and the number of connected power sources are not limited.

[0139] Secondly, the impedance detection method provided in this application is introduced.

[0140] Figure 7 This is a flowchart of an impedance detection method provided in an embodiment of the present application. The method is applied to an impedance detection circuit 100 as described above as an example for explanation. The method is executed by a controller 130 in the impedance detection circuit 100. The method includes the following steps 710 to 730.

[0141] Step 710, obtaining a first voltage value corresponding to the positive electrode of the power supply of the impedance detection circuit in the first connected state, and a second voltage value corresponding to the protective ground PE terminal.

[0142] The first connected state is used to indicate a state in which the first switch in the impedance detection circuit is turned on and the second switch is turned off. Figure 3 The first switch is turned on when the moving contact e2 and the stationary contact e1 of Q1 are connected, and the second switch is turned off when the moving contact e3 and the stationary contact e4 of Q2 are disconnected.

[0143] When the impedance detection circuit 100 is in the first connected state, the controller 130 can obtain the voltage value of the positive power supply V+ of the impedance detection circuit 100 as the first voltage value, and obtain the voltage value of the PE terminal of the impedance detection circuit 100 as the second voltage value. The first voltage value and the second voltage value are the above-mentioned first voltage data.

[0144] In some embodiments, to improve the accuracy of the first voltage value and the second voltage value obtained by the controller, the positive power supply and the PE terminal of the impedance detection circuit may be sampled multiple times, and the first voltage value and the second voltage value may be determined based on the multiple sampling values.

[0145] Optionally, when the impedance detection circuit is in a first connected state, the voltage value of the positive pole of the power supply of the impedance detection circuit is sampled to obtain at least two first candidate voltage values, and the voltage value of the PE terminal is sampled to obtain at least two second candidate voltage values; based on the at least two first candidate voltage values, the first voltage value is determined; based on the at least two second candidate voltage values, the second voltage value is determined.

[0146] Optionally, the voltage value of the positive electrode of the power supply of the impedance detection circuit is sampled at a preset time interval to obtain at least two first candidate voltage values; the voltage value of the PE terminal is sampled at a preset time interval to obtain at least two second candidate voltage values. Schematically, when the impedance detection circuit 100 is in the first connected state, at the first second, the voltage of the positive electrode of the power supply and the PE terminal is measured to obtain the first first candidate voltage value and the first second candidate voltage value, and at the second second, the voltage of the positive electrode of the power supply and the PE terminal is measured again to obtain the second first candidate voltage value and the second second candidate voltage value, until the sampling number reaches the preset sampling number, and the sampling is stopped.

[0147] By sampling multiple voltage values ​​in the first connected state to determine the first voltage value and the second voltage value, the accuracy and reliability of the voltage values ​​are improved. Multiple sampling can reduce the impact of accidental errors, making the final impedance detection result more accurate.

[0148] After obtaining at least two first candidate voltage values ​​and at least two second candidate voltage values, the method for determining the first voltage value and the second voltage value further includes:

[0149] (1) Average value method.

[0150] Illustratively, an average value of at least two first candidate voltage values ​​is calculated as the first voltage value, and an average value of at least two second candidate voltage values ​​is calculated as the second voltage value.

[0151] (2) Maximum / minimum method.

[0152] Illustratively, a maximum value or a minimum value among at least two first candidate voltage values ​​is selected as the first voltage value; and a maximum value or a minimum value among at least two second candidate voltage values ​​is selected as the second voltage value.

[0153] (3) Median method.

[0154] Illustratively, a median of at least two first candidate voltage values ​​is calculated as the first voltage value, and a median of at least two second candidate voltage values ​​is calculated as the second voltage value.

[0155] (4) Weighted average method.

[0156] Illustratively, if the sampling time intervals are uneven, or some sampling points are more important than other points, a weighted average value may be used to calculate the first voltage value and the second voltage value. For example, a weight is assigned to each first candidate voltage value, and then a weighted average value of at least two first candidate voltage values ​​is calculated as the first voltage value; a weight is assigned to each second candidate voltage value, and then a weighted average value of at least two second candidate voltage values ​​is calculated as the second voltage value.

[0157] (5)Trend analysis method.

[0158] In an illustrative manner, if the sampling is performed continuously over a period of time, trend analysis can also be performed. A straight line or a curve is fitted based on at least two first candidate voltage values ​​or at least two second candidate voltage values ​​to describe the change trend of the voltage value over time, and a first voltage value is extracted from the results of fitting the at least two first candidate voltage values; and a second voltage value is extracted from the results of fitting the at least two second candidate voltage values.

[0159] The above examples of methods for determining the first voltage value and the second voltage value are merely illustrative and are not limited here.

[0160] In some embodiments, if there are multiple power supplies connected to the impedance detection circuit, the first voltage values ​​corresponding to the positive electrodes of the multiple power supplies are obtained, and the maximum value of the multiple first voltage values ​​is used as the first voltage value for subsequent use. Figure 6 , when the first switch Q1 is turned on and the second switch Q2 is turned off, the controller 130 samples the voltage value of the first positive power source V1+ and the voltage value of the second positive power source V2+ N times, and uses the average value of the voltage values ​​of the N first positive power source V1+ as the first voltage value of the first positive power source V1+, and uses the average value of the voltage values ​​of the N second positive power source V2+ as the first voltage value of the second positive power source V2+; wherein, if the first voltage value of the first positive power source V1+ is greater than the first voltage value of the second positive power source V2+, the first voltage value of the first positive power source V1+ is used as the first voltage value for subsequent use, that is, as the first voltage value of the positive power source V+; if the first voltage value of the first positive power source V1+ is less than or equal to the first voltage value of the second positive power source V2+, the first voltage value of the second positive power source V2+ is used as the first voltage value for subsequent use, that is, as the first voltage value of the positive power source V+. wherein N is an integer greater than 1.

[0161] In some embodiments, the controller controls the impedance detection circuit to enter a first connection state through a first control signal.

[0162] Optionally, a first control signal is acquired, where the first control signal is used to control the first switch in the impedance detection circuit to be turned on and the second switch in the impedance detection circuit to be turned off.

[0163] Optionally, the first control signal includes two sub-control signals, wherein sub-control signal 1 (or referred to as the first sub-control signal) is used to control the first switch Q1, and sub-control signal 2 (or referred to as the second sub-control signal) is used to control the second switch Q2.

[0164] The following description is made by taking the first switch Q1 and the second switch Q2 as NPN transistors as an example.

[0165] For sub-control signal 1, such as Figure 8 As shown, in the circuit diagram 800, Q1_Ctrl is the sub-control signal 1 generated by the controller. When Q1_Ctrl is high (that is, the voltage applied to the base of Q1 is greater than or equal to the first threshold), Q1 is turned on to allow current to pass.

[0166] For sub-control signal 2, such as Fig. 9 As shown, in the circuit diagram 900, Q2_Ctrl is the sub-control signal 2 generated by the controller. When Q2_Ctrl is at a low level (ie, the voltage applied to the base of Q2 is less than the second threshold), Q2 is turned off and no current is allowed to pass.

[0167] Step 720, obtaining a third voltage value corresponding to the positive electrode of the power supply of the impedance detection circuit in the second connected state, and a fourth voltage value corresponding to the PE terminal.

[0168] The second connected state is used to indicate the state in which the first switch and the second switch are connected. Figure 3 The first switch being turned on means that the moving contact e2 of Q1 is connected to the stationary contact e1, and the second switch being turned on means that the moving contact e3 of Q2 is connected to the stationary contact e4.

[0169] When the impedance detection circuit 100 is in the second connected state, the controller 130 can obtain the voltage value of the positive power supply V+ of the impedance detection circuit 100 as the third voltage value, and obtain the voltage value of the PE terminal of the impedance detection circuit 100 as the fourth voltage value. The third voltage value and the fourth voltage value are the above-mentioned second voltage data.

[0170] In some embodiments, to improve the accuracy of the third voltage value and the fourth voltage value obtained by the controller, the positive power supply and the PE terminal of the impedance detection circuit may be sampled multiple times, and the third voltage value and the fourth voltage value may be determined based on the multiple sampling values.

[0171] Optionally, when the impedance detection circuit is in the second connectivity state, the voltage value of the positive pole of the power supply of the impedance detection circuit is sampled to obtain at least two third candidate voltage values, and the voltage value of the PE terminal is sampled to obtain at least two fourth candidate voltage values; based on the at least two third candidate voltage values, the third voltage value is determined; based on the at least two fourth candidate voltage values, the fourth voltage value is determined.

[0172] The method for determining the third voltage value may refer to the method for determining the first voltage value in step 710 , and the method for determining the fourth voltage value may refer to the method for determining the second voltage value in step 710 , which will not be described in detail here.

[0173] By sampling multiple voltage values ​​in the second connection state to determine the third voltage value and the fourth voltage value, the accuracy and reliability of the voltage values ​​are improved. Multiple sampling can reduce the impact of accidental errors, making the final impedance detection result more accurate.

[0174] In some embodiments, if there are multiple power supplies connected to the impedance detection circuit, the third voltage values ​​corresponding to the positive electrodes of the multiple power supplies are obtained, and the maximum value of the multiple third voltage values ​​is used as the third voltage value for subsequent use. Figure 6 , when the first switch Q1 is turned on and the second switch Q2 is turned on, the controller 130 samples the voltage value of the first positive power supply V1+ and the voltage value of the second positive power supply V2+ N times, and takes the average value of the voltage values ​​of the N first positive power supply V1+ as the third voltage value of the first positive power supply V1+, and takes the average value of the voltage values ​​of the N second positive power supply V2+ as the third voltage value of the second positive power supply V2+; wherein, if the third voltage value of the first positive power supply V1+ is greater than the third voltage value of the second positive power supply V2+, the third voltage value of the first positive power supply V1+ is used as the third voltage value for subsequent use, that is, as the third voltage value of the positive power supply V+; if the third voltage value of the first positive power supply V1+ is less than or equal to the third voltage value of the second positive power supply V2+, the third voltage value of the second positive power supply V2+ is used as the third voltage value for subsequent use, that is, as the third voltage value of the positive power supply V+.

[0175] In some embodiments, the controller controls the impedance detection circuit to enter the second connection state through a second control signal.

[0176] Optionally, a second control signal is obtained, and the second control signal is used to control the first switch in the impedance detection circuit to be turned on and the second switch in the impedance detection circuit to be turned on.

[0177] Optionally, the second control signal includes two control signals, wherein sub-control signal 1 (or called the third sub-control signal) is used to control the first switch Q1, and sub-control signal 2 (or called the fourth sub-control signal) is used to control the second switch Q2.

[0178] For sub-control signal 1, such as Figure 8 As shown, in the circuit diagram 800, Q1_Ctrl is the sub-control signal 1 generated by the controller 130. When Q1_Ctrl is high (ie, the voltage applied to the base of Q1 is greater than or equal to the first threshold), Q1 is turned on to allow current to pass.

[0179] For sub-control signal 2, such as Fig. 9 As shown, in the circuit diagram 900, Q2_Ctrl is the sub-control signal 2 generated by the controller 130. When Q2_Ctrl is high (ie, the voltage applied to the base of Q2 is greater than or equal to the second threshold), Q2 is turned on to allow current to pass.

[0180] In some embodiments, the second control signal is used to control the first switch to be turned on before the second switch.

[0181] In the embodiment of the present application, in order to obtain more accurate impedance detection results, when controlling Q2 to turn on, Q1 can be controlled to turn on in advance, so that the voltage of the positive electrode V+ of the power supply flows through R2 and R4 and then to the GND end, so that the voltage of the PE end can be sampled more accurately.

[0182] Optionally, in the above-mentioned second control signal, after the controller triggers sub-control signal 1, sub-control signal 2 is not triggered temporarily, and sub-control signal 2 is triggered after a preset time period has passed after sub-control signal 1 is triggered.

[0183] For illustration, please refer to Fig.10 When Q1_Ctrl is triggered, Q1 is turned on. At this time, Q2_Ctrl can be temporarily untriggered. When Q1 is turned on, the voltage of the positive electrode V+ of the power supply will flow through R2 and R4 and then to the GND end. After Q1_Ctrl is triggered, after a preset time, Q2_Ctrl is triggered, making Q2 turned on.

[0184] Step 730, determining an impedance detection result based on the first voltage value, the second voltage value, the third voltage value, and the fourth voltage value.

[0185] The impedance detection result includes at least one of the insulation impedance of the positive pole of the power supply to the ground in the impedance detection circuit and the insulation impedance of the negative pole of the power supply to the ground in the impedance detection circuit.

[0186] Optionally, based on the first voltage value, the second voltage value, the third voltage value and the fourth voltage value, a load value of the first load and a load value of the third load in the impedance detection circuit are determined.

[0187] The load value of the first load is used to indicate the insulation impedance of the positive pole of the power supply to the ground in the impedance detection circuit, and the load value of the third load is used to indicate the insulation impedance of the negative pole of the power supply to the ground in the impedance detection circuit.

[0188] For illustration, please refer to Figure 3 The controller 130 determines the load value of the first load as the insulation impedance of the positive electrode of the power supply to the PE terminal, and determines the load value of the third load as the insulation impedance of the negative electrode of the power supply to the PE terminal based on the first voltage value, the second voltage value, the third voltage value, the fourth voltage value, the load value of the second load, the load value of the fourth load, the load value of the fifth load and the load value of the sixth load.

[0189] It should be noted that in the embodiment of the present application, the load values ​​of the second load, the fourth load, the fifth load and the sixth load in the impedance detection circuit are known quantities, and the load values ​​of the first load and the third load are unknown quantities. The following is an introduction to the process of determining the impedance detection results, taking the above-mentioned loads as resistors as an example for explanation.

[0190] (1) When the first switch Q1 is turned on and the second switch Q2 is turned off, refer to Figure 4 The equivalent circuit is shown.

[0191] like Figure 4 As shown, the first resistor R1 and the second resistor R2 are connected in parallel, and the first resistance value RP1 is calculated by formula 1, which is: first resistance value RP1 = (resistance value of the first resistor R1 × resistance value of the second resistor R2) ÷ (resistance value of the first resistor R1 + resistance value of the second resistor R2).

[0192] The fifth resistor R5 and the sixth resistor R6 are connected in series and in parallel with the third resistor R3, and the second resistance value RP2 is calculated by formula 2. Formula 2 is: second resistance value RP2 = ((resistance value of the fifth resistor R5 + resistance value of the sixth resistor R6) × resistance value of the third resistor R3) ÷ ((resistance value of the fifth resistor R5 + resistance value of the sixth resistor R6) + resistance value of the third resistor R3).

[0193] (2) When the first switch Q1 is turned on and the second switch Q2 is turned on, refer to Figure 5 The equivalent circuit is shown.

[0194] like Figure 5 As shown, the third resistor R3 and the fourth resistor R4 are connected in parallel, and the third resistance value RP3 is calculated by Formula 3, which is: the third resistance value RP3 = (resistance value of the third resistor R3 × resistance value of the fourth resistor R4) ÷ (resistance value of the third resistor R3 + resistance value of the fourth resistor R4).

[0195] The fifth resistor R5 and the sixth resistor R6 are connected in series and in parallel with the parallel resistor of the third resistor R3 and the fourth resistor R4, and the fourth resistance value RP4 is calculated by formula 4. Formula 4 is: fourth resistance value RP4 = ((resistance value of the fifth resistor R5 + resistance value of the sixth resistor R5) × third resistance value RP3) ÷ ((resistance value of the fifth resistor R5 + resistance value of the sixth resistor R5) + third resistance value RP3).

[0196] After the above formulas 1 to 4 are obtained, the first equivalent current relationship and the second equivalent current relationship in the impedance detection circuit are determined according to Kirchhoff's voltage and current laws.

[0197] The first equivalent current relationship is expressed by the following formula 5, which is: first voltage value V1×second resistance value RP2=second voltage value V2×(first resistance value RP1+second resistance value RP2).

[0198] The second equivalent current relationship is expressed by the following formula 6, which is: third voltage value V3×fourth resistance value RP4=fourth voltage value V4×(first resistance value RP1+fourth resistance value RP4).

[0199] By combining the above formulas 1 to 6 and substituting the first voltage value, the second voltage value, the third voltage value, the fourth voltage value, the resistance value of the second resistor, the resistance value of the fourth resistor, the resistance value of the fifth resistor and the resistance value of the sixth resistor, the resistance value of the first resistor and the resistance value of the third resistor can be solved, wherein the resistance value of the first resistor is also the insulation impedance of the positive pole of the power supply to the ground in the impedance detection circuit, and the resistance value of the third resistor is also the insulation impedance of the negative pole of the power supply to the ground in the impedance detection circuit.

[0200] To sum up, the impedance detection method provided in the embodiment of the present application can accurately determine the insulation impedance of the positive and negative poles of the power supply to the ground by obtaining the voltage value of the impedance detection circuit in different connectivity states, thereby improving the accuracy of impedance detection. Moreover, through automated detection, the complexity of manual operation is reduced and the detection efficiency is improved.

[0201] In some embodiments, the impedance detection circuit 100 in the present application is used for an inverter in a photovoltaic power generation system. The positive power pole V+ of the impedance detection circuit 100 refers to PV+, that is, the positive power pole of the photovoltaic power source; the negative power pole V- refers to PV-, that is, the negative power pole of the photovoltaic power source. The impedance detection circuit 100 is used to detect the insulation impedance of the positive power pole PV+ of the photovoltaic power source to the ground and the insulation impedance of the negative power pole PV- of the photovoltaic power source to the ground. For illustration, please refer to Fig.11 , which shows a schematic diagram of the process of insulation impedance detection, the following is combined with Figure 6 The following describes the steps in the insulation resistance test flow.

[0202] Step 1101, clear the sampling count and sampling buffer.

[0203] Before starting a new insulation impedance detection, the controller 130 clears all previous data (including the count value of the sampling count and the voltage value stored in the sampling buffer) to avoid data confusion.

[0204] Step 1102, close Q1 and open Q2.

[0205] Please refer to Figure 6 , closing Q1 also turns on the first switch Q1, and opening Q2 also turns off the second switch Q2. Schematically, the controller 130 controls the moving contact e2 and the stationary contact e1 of Q1 to connect to close Q1, and the controller 130 controls the moving contact e3 and the stationary contact e4 of Q2 to disconnect to disconnect Q2.

[0206] Step 1103, sampling PV1+, PV2+, and PE voltages.

[0207] When Q1 is closed and Q2 is open, the controller 130 samples the PV1+ voltage, PV2+ voltage, and PE voltage. Figure 6 The positive voltage of the photovoltaic power source connected to D1 is shown, where the PV2+ voltage is also Figure 6 The positive voltage of the photovoltaic power source connected to D2 is shown, and the PE voltage is Figure 6 The voltage at the PE terminal is shown.

[0208] After the controller 130 completes one sampling, the sampling count is increased by 1, and the controller 130 stores the sampled voltage value into the sampling buffer. Completing one sampling means successfully sampling the PV1+ voltage, PV2+ voltage, and PE voltage once.

[0209] Step 1104, determine whether the sampling count reaches N times.

[0210] The controller 130 determines whether the current sampling count reaches N times, where N is an integer greater than 1.

[0211] If the sampling count does not reach N times, go to step 1103, that is, continue sampling.

[0212] Step 1105: If it reaches N times, calculate Vpv0 and Vpe0.

[0213] If the sampling count reaches N times, the controller 130 calculates the sampling values ​​in the sampling buffer: the average value of the N PV1+ voltages obtained by sampling is calculated as a, the average value of the N PV2+ voltages obtained by sampling is calculated as b, and the maximum value of a and b is used as Vpv0 (when a=b, a or b is used as Vpv0), which is the above-mentioned first voltage value; the average value of the N PE voltages obtained by sampling is calculated as Vpe0, which is the above-mentioned second voltage value.

[0214] Step 1106, clear the sampling count and sampling buffer.

[0215] After obtaining Vpv0 and Vpe0, the controller 130 clears the sampling count and the sampling buffer.

[0216] Step 1107, close Q1, close Q2.

[0217] Please refer to Figure 6 , closing Q1 also turns on the first switch Q1, closing Q2 also turns on the second switch Q2. Schematically, the controller 130 controls the connection between the moving contact e2 and the stationary contact e1 of Q1 to close Q1, and the controller 130 controls the connection between the moving contact e3 and the stationary contact e4 of Q2 to close Q2.

[0218] Step 1108, sampling PV1+, PV2+, and PE voltages.

[0219] After closing Q1 and closing Q2 (wherein, voltage sampling can begin after closing Q1, and Q2 is closed after Q1), the controller 130 starts sampling the PV1+ voltage, the PV2+ voltage, and the PE voltage.

[0220] After the controller 130 completes one sampling, the sampling count is increased by 1, and the controller 130 stores the sampled voltage value in the sampling buffer.

[0221] Step 1109, determine whether the sampling count reaches N times.

[0222] The controller 130 determines whether the current sampling count reaches N times.

[0223] If the sampling count does not reach N times, go to step 1108, that is, continue sampling.

[0224] Step 1110: If it reaches N times, calculate Vpv1 and Vpe1.

[0225] If the sampling count reaches N times, the controller 130 calculates the sampling values ​​in the sampling buffer: the average value of the N PV1+ voltages obtained by sampling is calculated as c, the average value of the N PV2+ voltages obtained by sampling is calculated as d, and the maximum value of c and d is used as Vpv1 (when c=d, c or d is used as Vpv1), that is, the third voltage value; the average value of the N PE voltages obtained by sampling is calculated as Vpe1, that is, the fourth voltage value.

[0226] Step 1111, calculating the insulation resistance of PV+ to ground and the insulation resistance of PV- to ground.

[0227] After obtaining Vpv0, Vpe0, Vpv1 and Vpe1, the resistance values ​​of R1 and R2 can be obtained by combining the known resistance values ​​of R2, R4, R5 and R6, where the resistance value of R1 is the insulation impedance of PV+ to ground, and the resistance value of R2 is the insulation impedance of PV- to ground. The following is an explanation of the process of determining the insulation impedance.

[0228] When Q1 is closed and Q2 is open, R2 and R1 are connected in parallel, and the parallel resistance RP1 of the two is calculated using Formula 1, and the resistance RP2 of R5 and R6 connected in series and in parallel with R3 is calculated using Formula 2. When Q1 and Q2 are closed, the parallel resistance RP3 of R4 and R3 is calculated using Formula 3, and the resistance RP4 of R5 and R6 connected in series and in parallel with the parallel resistance of R3 and R4 is calculated using Formula 4.

[0229] Then, according to Kirchhoff's voltage and current law, Formula 5 and Formula 6 are listed, and Formula 1 to 6 are combined. Substituting the known values ​​of Vpv0 (PV+ voltage value), Vpe0 (PE terminal voltage value), Vpv1 (PV+ voltage value), Vpe1 (PE terminal voltage value) and R2, R4, R5 and R6, the insulation resistance R1 of PV+ to ground and the insulation resistance R2 of PV- to ground can be calculated.

[0230] Wherein, formula 1 to formula 6 are as follows:

[0231] Formula 1: RP1=(R1×R2)÷(R1+R2)

[0232] Formula 2: RP2 = ((R5 + R6) × R3) ÷ ((R5 + R6) + R3)

[0233] Formula 3: RP3=(R3×R4)÷(R3+R4)

[0234] Formula 4: RP4 = ((R5 + R6) × RP3) ÷ ((R5 + R6) + RP3)

[0235] Formula 5: Vpv0×RP2=Vpe0×(RP1+RP2)

[0236] Formula 6: Vpv1×RP4=Vpe1×(RP1+RP4)

[0237] It should be noted that in formulas 1 to 6, Ri represents the resistance value, for example, R2 represents the resistance value of the second resistor.

[0238] In summary, the insulation impedance detection method provided in the embodiment of the present application can accurately calculate the insulation impedance of PV+ or PV- to the ground and the insulation impedance of PV+ and PV- to the ground at the same time, compared with the traditional balanced bridge method for detecting insulation impedance. The implementation method is simple and easy to operate and can be applied to all photovoltaic inverters.

[0239] Next, the inverter provided by this application is introduced.

[0240] The inverter provided in the present application includes any impedance detection circuit as described above, and the inverter is used to execute any impedance detection method as described above.

[0241] For illustration, please refer to Fig.12 , which shows a schematic diagram of the structure of an inverter, such as Fig.12 As shown, the inverter 1200 includes: an inverter circuit 1210 and an impedance detection circuit 1220 .

[0242] An inverter is a device that converts direct current (DC) into alternating current (AC) and is widely used in photovoltaic power generation systems. For example, an inverter can convert DC power sources such as photovoltaic power sources (such as solar cells) in photovoltaic power generation systems into AC power for use by AC loads.

[0243] The inverter circuit 1210 is the core part of the inverter, responsible for converting DC power into AC power. This conversion process is usually achieved by controlling the on and off of the switch elements. When the switch elements are turned on and off at a certain frequency and duty cycle, the DC power supply will generate high-frequency pulse voltage or current through these switch elements. After these pulses are filtered and modulated, the required AC output can be obtained.

[0244] The impedance detection circuit 1220 is used to monitor and analyze the impedance characteristics of the inverter. This is essential to ensure the stable operation of the inverter. The impedance detection circuit 1220 can be implemented as any impedance detection circuit described above, and the impedance detection circuit 1220 includes a controller, which can execute any impedance detection method described above, which will not be described in detail here.

[0245] Finally, the photovoltaic power generation system provided by this application is introduced.

[0246] The photovoltaic power generation system provided in the present application includes an inverter, the inverter includes any impedance detection circuit as described above, and the inverter is used to execute any impedance detection method as described above.

[0247] For illustration, please refer to Fig.13 , which shows a schematic diagram of a photovoltaic power generation system. Fig.13 As shown, the photovoltaic power generation system 1300 includes: a power grid / load 1301, an inverter 1302, and a plurality of MPPT controllers and photovoltaic power sources PV respectively connected to the plurality of MPPT controllers. Fig.13 There are m MPPT controllers shown, where m is an integer greater than 1.

[0248] The photovoltaic power generation system 1300 is a system that directly converts sunlight into electrical energy using photovoltaic power sources.

[0249] The grid / load 1301 is the output end of the photovoltaic power generation system, which can be a grid or a directly connected load (such as a household appliance). After the electric energy generated by the photovoltaic power generation system is converted into AC power by an inverter, it can be directly supplied to these loads for use or incorporated into the grid.

[0250] The inverter 1302 converts the direct current generated by the photovoltaic power source PV into alternating current for use by the power grid or load. Optionally, the inverter 1302 can be implemented as follows: Fig.12 Inverter 1200 is shown.

[0251] The MPPT controller is used to maximize the power output of photovoltaic power sources. Each MPPT controller is connected to a group of photovoltaic power sources PV. The MPPT controller adjusts the voltage and current to make the photovoltaic power source PV always work at its maximum power point. The photovoltaic power source PV can be implemented as a solar cell.

[0252] like Fig.13 As shown, multiple photovoltaic power sources PV are connected to the inverter 1302 through their respective corresponding MPPT controllers, wherein multiple power positive electrodes PV+ are respectively connected to the impedance detection circuit in the inverter 1302, each power positive electrode PV+ is connected to a diode, and multiple power positive electrodes PV- are commonly connected to the GND end of the impedance detection circuit in the inverter 1302.

[0253] In the embodiment of the present application, the impedance detection circuit can be applied to the inverter in the photovoltaic power generation system. The impedance detection circuit is mainly used in the inverter of the photovoltaic power generation system to monitor the impedance change between the photovoltaic power source and the ground, which helps to ensure the stable operation of the inverter and prevents failures or accidents caused by abnormal impedance. For ungrounded photovoltaic power sources, the inverter needs to perform insulation impedance detection on all connected photovoltaic power sources before grid-connected operation. Only when the impedance values ​​of PV+ and PV- to the ground of all photovoltaic power sources are not less than the specified minimum value, grid-connected operation is allowed, which helps to prevent electric shock accidents caused by reduced insulation performance.

Claims

1. An impedance detection circuit, characterized in that: The circuit includes a positive load circuit, a negative load circuit and a controller; The positive load circuit and the negative load circuit are connected in parallel to the protective grounding PE terminal, and the positive load circuit is connected to the positive electrode of the power supply, and the negative load circuit is grounded; the positive load circuit includes a first load, a second load and a first switch, and the negative load circuit includes a third load, a fourth load and a second switch; The first end of the first load is connected to the first end of the third load; the first end of the first load is connected to the PE end; the second end of the first load is connected to the first switch; the first end of the second load is connected to the first switch; the second end of the third load is connected to the second switch, the first end of the fourth load is connected to the second switch; the second end of the second load is connected to the second end of the fourth load; The controller is respectively connected to the parallel node of the positive load circuit and the negative load circuit, the first switch, and the second switch. The controller is used to: collect first voltage data when the first switch is turned on and the second switch is turned off; collect second voltage data when the first switch and the second switch are turned on; and determine the impedance detection result based on the first voltage data and the second voltage data.

2. The circuit according to claim 1, characterized in that The second end of the first load is connected to the first static contact of the first switch; the first end of the second load is connected to the first moving contact of the first switch; The second end of the third load is connected to the second moving contact of the second switch, and the first end of the fourth load is connected to the second static contact of the second switch.

3. The circuit according to claim 1 or 2, characterized in that: The circuit also includes a grounded load circuit; The grounded load circuit includes a fifth load and a sixth load; The first end of the fifth load is connected to the first end of the sixth load; the second end of the fifth load is connected to the second end of the second load; the second end of the sixth load is grounded; The second end of the fifth load is connected to the controller.

4. The circuit according to claim 3, characterized in that When the first switch is turned on and the second switch is turned off, the circuit includes the following loops: a first loop, in which current flows from the first load to the third load; a second loop, in which current flows from the first load to the fifth load, and from the fifth load to the sixth load; a third loop, in which current flows from the second load to the third load; A fourth loop, in which current flows from the second load to the fifth load, and from the fifth load to the sixth load.

5. The circuit according to claim 3, characterized in that When the first switch and the second switch are turned on, the circuit includes the following loops: a first loop, in which current flows from the first load to the third load; a second loop, in which current flows from the first load to the fifth load, and from the fifth load to the sixth load; a third loop, in which current flows from the second load to the third load; a fourth loop, in which current flows from the second load to the fifth load, and from the fifth load to the sixth load; a fifth loop, in which current flows from the first load to the fourth load; A sixth loop, in which current flows from the second load to the fourth load.

6. The circuit according to claim 1 or 2, characterized in that: The circuit also includes at least one diode, and the positive load circuit is connected to the at least one diode.

7. An impedance detection method, characterized in that: Applied to the impedance detection circuit as described in any one of claims 1 to 6 above, and executed by a controller in the impedance detection circuit, the method comprises: Acquire a first voltage value corresponding to the positive electrode of the power supply of the impedance detection circuit in a first connected state, and a second voltage value corresponding to the protective ground PE terminal; the first connected state is used to indicate a state in which the first switch in the impedance detection circuit is turned on and the second switch is turned off; Acquire a third voltage value corresponding to the positive electrode of the power supply of the impedance detection circuit in a second connected state, and a fourth voltage value corresponding to the PE terminal; the second connected state is used to indicate a state in which the first switch and the second switch are turned on; Based on the first voltage value, the second voltage value, the third voltage value and the fourth voltage value, an impedance detection result is determined, and the impedance detection result includes at least one of the insulation impedance of the positive pole of the power supply to the ground in the impedance detection circuit and the insulation impedance of the negative pole of the power supply to the ground in the impedance detection circuit.

8. The method according to claim 7, characterized in that The determining the impedance detection result based on the first voltage value, the second voltage value, the third voltage value and the fourth voltage value comprises: determining a load value of a first load and a load value of a third load in the impedance detection circuit based on the first voltage value, the second voltage value, the third voltage value, and the fourth voltage value; The load value of the first load is used to indicate the insulation impedance of the positive pole of the power supply to the ground in the impedance detection circuit, and the load value of the third load is used to indicate the insulation impedance of the negative pole of the power supply to the ground in the impedance detection circuit.

9. The method according to claim 7, characterized in that: The obtaining of a first voltage value corresponding to the positive electrode of the power supply of the impedance detection circuit in the first connected state and a second voltage value corresponding to the protective ground PE terminal includes: When the impedance detection circuit is in the first connected state, sampling the voltage value of the positive electrode of the power supply of the impedance detection circuit to obtain at least two first candidate voltage values, and sampling the voltage value of the PE terminal to obtain at least two second candidate voltage values; The first voltage value is determined based on the at least two first candidate voltage values; and the second voltage value is determined based on the at least two second candidate voltage values.

10. The method according to claim 7, characterized in that The obtaining of a third voltage value corresponding to the positive electrode of the power supply of the impedance detection circuit in the second connected state and a fourth voltage value corresponding to the PE terminal includes: When the impedance detection circuit is in the second connected state, sampling the voltage value of the positive electrode of the power supply of the impedance detection circuit to obtain at least two third candidate voltage values, and sampling the voltage value of the PE terminal to obtain at least two fourth candidate voltage values; The third voltage value is determined based on the at least two third candidate voltage values; and the fourth voltage value is determined based on the at least two fourth candidate voltage values.

11. The method according to any one of claims 7 to 10, characterized in that: Before obtaining a first voltage value corresponding to the positive electrode of the power supply of the impedance detection circuit in the first connected state and a second voltage value corresponding to the protective ground PE terminal, the method further includes: Acquire a first control signal, where the first control signal is used to control the first switch in the impedance detection circuit to be turned on and the second switch in the impedance detection circuit to be turned off; Before acquiring the third voltage value corresponding to the positive electrode of the power supply of the impedance detection circuit in the second connected state and the fourth voltage value corresponding to the PE terminal, the method further includes: A second control signal is obtained, where the second control signal is used to control the first switch and the second switch to be turned on.

12. An inverter, characterized in that: The inverter comprises the impedance detection circuit as claimed in any one of claims 1 to 6, and the inverter is used to execute the impedance detection method as claimed in any one of claims 7 to 11.

13. A photovoltaic power generation system, characterized in that: The photovoltaic power generation system includes an inverter, the inverter includes the impedance detection circuit as described in any one of claims 1 to 6, and the inverter is used to execute the impedance detection method as described in any one of claims 7 to 11.

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