Insulation detection circuit and method for inverter system

Abstract

The invention discloses an insulation detection circuit and method of an inverter system. The inverter system comprises an inverter, n input branches, an output bus, a direct current source and a protection grounding point, the first end of the input branch is connected with the input end of the inverter, the second end of the input branch is connected with the positive electrode of the direct current source, and the output end of the inverter is connected with the output bus; an equivalent insulation resistance value exists between the input branch and the protection grounding point; the insulation detection circuit is characterized by comprising a voltage adjusting module; the first end of the voltage adjusting module is connected with the protection grounding point, and the second end of the voltage adjusting module is connected with the cathode of the DC source. The voltage adjusting module is used for adjusting the voltage values of the n input branches and the voltage of the output bus. According to the technical scheme of the embodiment of the invention, the insulation resistance values of multiple branches can be measured at one time, the measurement cost is reduced, the change of the direct current input voltage can be ignored, and the accuracy of an insulation value measurement result is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of inverter insulation detection, and in particular to an insulation detection circuit and method for an inverter system. Background Art

[0002] With the rapid development of inverters, the power of inverters is getting bigger and bigger, and the number of input branches is increasing. Any insulation problem of an input branch will cause the inverter to fail and damage, resulting in large property losses and potential safety hazards. At present, balanced bridge method and unbalanced bridge method are usually used to perform insulation tests on the input branches of inverters. The existing test methods not only require more bias resistor switches, but also have low accuracy of the detected insulation resistance value, high overall detection cost, and low detection efficiency. Summary of the invention

[0003] The invention provides an insulation detection circuit and method for an inverter system, so as to improve the accuracy of the insulation resistance detection result of the inverter.

[0004] According to one aspect of the present invention, an insulation detection circuit of an inverter system is provided, the inverter system comprising: an inverter, n input branches, an output bus, a DC source and a protective grounding point; a first end of the input branch is connected to an input end of the inverter, a second end of the input branch is connected to a positive electrode of the DC source, and an output end of the inverter is connected to the output bus; an equivalent insulation resistance value exists between the input branch and the protective grounding point; the insulation detection circuit comprises: a voltage adjustment module;

[0005] The first end of the voltage adjustment module is connected to the protective grounding point, and the second end of the voltage adjustment module is connected to the negative electrode of the DC source; the voltage adjustment module is used to adjust the voltage values ​​of the n input branches and the voltage value of the output bus.

[0006] Optionally, the voltage adjustment module includes a voltage adjustment unit and a current limiting unit;

[0007] The first end of the voltage adjustment unit is connected to the protective grounding point, the second end of the voltage adjustment unit and the first end of the current limiting unit are commonly connected to a first node, and the second end of the current limiting unit is connected to the negative electrode of the DC source.

[0008] Optionally, it also includes a sampling module and a calculation module;

[0009] The sampling end of the sampling module is connected to the input branch, the output bus and the first node respectively; the output end of the sampling module is connected to the calculation module;

[0010] The sampling module is used to obtain the voltage value of the input branch and the voltage value of the output bus corresponding to the output value of each voltage adjustment module under the output value of n+2 voltage adjustment modules;

[0011] The calculation module is used to substitute the output value of the voltage adjustment module, the corresponding voltage values ​​of each input branch and the voltage value of the output bus into a preset equation, wherein the unknown quantity of the preset equation is each equivalent insulation resistance; and determine the equivalent insulation resistance according to the n+2 preset equations corresponding to the output values ​​of the n+2 voltage adjustment modules.

[0012] Optionally, the DC source comprises a photovoltaic panel and / or a battery.

[0013] Optionally, the current limiting unit includes a resistor.

[0014] According to another aspect of the present invention, a method for detecting an insulation value of an inverter system is provided, which is performed according to the inverter insulation detection circuit of the first aspect, and includes:

[0015] Under the output values ​​of n+2 voltage adjustment modules, obtaining the voltage value of the input branch and the voltage value of the output bus corresponding to the output value of each voltage adjustment module;

[0016] Substituting the output value of the voltage adjustment module, the corresponding voltage value of each input branch and the voltage value of the output bus into a preset equation, wherein the unknown quantity of the preset equation is each equivalent insulation resistance;

[0017] The equivalent insulation resistance is determined according to the n+2 preset equations corresponding to the output values ​​of the n+2 voltage adjustment modules.

[0018] Optionally, the voltage adjustment module includes a voltage adjustment unit and a current limiting unit; a first end of the voltage adjustment unit is connected to the protective grounding point, and a second end of the voltage adjustment unit and a first end of the current limiting unit are commonly connected to a first node;

[0019] Under the output values ​​of n+2 voltage adjustment modules, obtaining the voltage value of the input branch and the voltage value of the output bus corresponding to the output value of each voltage adjustment module includes:

[0020] Set the output value of the voltage adjustment unit;

[0021] Obtaining a voltage value of the input branch, a voltage value of the output bus, and a voltage value of the first node corresponding to an output value of the voltage adjustment module;

[0022] Return to the step of setting the output value of the voltage adjustment unit until the voltage values ​​of the input branches, the output bus and the first node corresponding to a total of n+2 groups of the voltage adjustment modules at different output values ​​are obtained.

[0023] Optionally, the preset equation includes:

[0024] (U1x-Umx)*G1+...+(Unx-Umx)*Gn+(Ubx-Umx)*Gb-Umx*Gm-Uax*Gr=0;

[0025] Among them, Umx is the output value of the voltage adjustment module, Unx is the voltage value on the nth input branch corresponding to Umx, Ubx is the voltage value of the output bus corresponding to Umx, Uax is the voltage value of the first node, Gn is the reciprocal of the equivalent insulation resistance value on the nth input branch, Gb is the reciprocal of the equivalent insulation resistance value on the output bus, Gm is the reciprocal of the equivalent insulation resistance value at the protective grounding point, and Gr is the conductance value of the current limiting unit.

[0026] Optionally, determining the equivalent insulation resistance according to n+2 preset equations corresponding to the output values ​​of the n+2 voltage adjustment modules includes:

[0027] Arrange the n+2 preset equations in a matrix and solve the unknowns, wherein the matrix expression is A*G+B=0;

[0028] Among them, G1, G2...Gn, Gb and Gm are the unknown quantities G to be determined, n+2 groups U1x-Umx, U2x-Umx...Unx-Umx, Ubx-Umx and -Umx are the coefficients of the matrix A, and n+2 groups -Uax*Gr are the constant terms B of the matrix.

[0029] Optionally, after arranging the n+2 preset equations in a matrix and solving the unknowns, the method further includes: finding the inverse of the solution of the matrix.

[0030] The technical solution provided by the present invention obtains the voltage values ​​of n input branches and the output busbar at each voltage adjustment of the voltage adjustment module, takes the voltage of the voltage adjustment module after each adjustment, the voltage on the n input branches and the voltage on the output busbar as known quantities, takes the protective grounding point as the voltage node, and combines Kirchhoff's law to solve the equivalent insulation resistance between each input branch and the protective grounding point, as well as the equivalent insulation resistance between the output busbar and the protective grounding point. Compared with the prior art, the technical solution provided by the present invention does not need to set multiple groups of bias switches, can measure the insulation resistance values ​​of multiple branches at one time, and reduces the measurement cost; does not need to switch on and off resistors, will not affect the reduction of the actual insulation value during testing, can ignore the change of the DC input voltage, and improves the accuracy of the insulation value measurement result.

[0031] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 A schematic diagram of the structure of an insulation detection circuit of an inverter system provided by an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of the structure of an insulation detection circuit of another inverter system provided by an embodiment of the present invention;

[0035] Figure 3 A schematic diagram of the structure of an insulation detection circuit of another inverter system provided by an embodiment of the present invention;

[0036] Figure 4 It is a flow chart of a method for detecting insulation value of an inverter system provided by the present invention;

[0037] Figure 5 is a flow chart of another method for detecting insulation value of an inverter system provided by the present invention;

[0038] Figure 6 This is a flow chart of another method for detecting the insulation value of an inverter system provided by the present invention. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0040] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0041] Figure 1 The present invention provides an insulation detection circuit structure diagram of an inverter system. Figure 1 As shown, the inverter system includes: an inverter 10, n input branches L1, L2, L3...Ln, an output bus L0, a DC source 20 and a protective grounding point PE; the first end of the input branch is connected to the input end of the inverter 10, the second end of the input branch is connected to the positive pole of the DC source 20, and the output end of the inverter 10 is connected to the output bus L0; there is an equivalent insulation resistance value R1, R2, R3...Rn between each input branch and the protective grounding point PE. The insulation detection circuit includes: a voltage adjustment module 100; the first end of the voltage adjustment module 100 is connected to the protective grounding point PE, and the second end of the voltage adjustment module 100 is connected to the negative pole GND of the DC source 20; the voltage adjustment module 100 is used to adjust the voltage values ​​of the n input branches and the voltage value of the output bus L0.

[0042] Specifically, the inverter 10 is a converter that converts the DC power of the DC source 20 into AC power of a certain frequency. The positive poles of the n DC sources 20 are connected to the input end of the inverter 10 through the input branches L1, L2, L3...Ln, respectively, and are output through the output bus L0 after conversion by the inverter 10. The protective grounding point PE can be the casing of the inverter 10, and the casing of the inverter 10 is connected to the ground to ensure that the electric potential of the entire inverter system is the same. There is a certain insulation resistance between each input branch and the protective grounding point PE, and between the output bus L0 and the protective grounding point PE. For example, Figure 1 As shown, the equivalent insulation resistance value between the input branch L1 and the protective grounding point PE is R1, the equivalent insulation resistance value between the input branch L2 and the protective grounding point PE is R2, and so on, the equivalent insulation resistance value between the input branch Ln and the protective grounding point PE is Rn; the equivalent insulation resistance value between the output bus L0 and the protective grounding point PE is Rb. In order to obtain the equivalent insulation resistance between each input branch and the protective grounding point PE, and between the output bus L0 and the protective grounding point PE, the insulation detection circuit provided by the present invention connects the first end of the voltage adjustment module 100 to the protective grounding point PE, and the second end of the voltage adjustment module 100 is connected to the common negative electrode GND of the n DC sources 20. By adjusting the voltage of the voltage adjustment module 100, the voltage values ​​of the n input branches and the voltage value of the output bus L0 are changed. The voltage of the voltage adjustment module 100 after each adjustment, the voltage on the n input branches Ln and the voltage on the output bus L0 are taken as known quantities, and the protective grounding point PE is taken as a voltage node. Kirchhoff's law is combined to solve the equivalent insulation resistance between each input branch L and the protective grounding point PE, the equivalent insulation resistance between the output bus L0 and the protective grounding point PE, and the equivalent insulation resistance between the common negative electrode GND of the n input branches and the protective grounding point PE.

[0043] The technical solution provided by the present invention obtains the voltage values ​​of n input branches and the output busbar at each voltage adjustment of the voltage adjustment module, takes the voltage of the voltage adjustment module after each adjustment, the voltage on the n input branches and the voltage on the output busbar as known quantities, takes the protective grounding point as the voltage node, and combines Kirchhoff's law to solve the equivalent insulation resistance between each input branch and the protective grounding point, as well as the equivalent insulation resistance between the output busbar and the protective grounding point. Compared with the prior art, the technical solution provided by the present invention does not need to set multiple groups of bias switches, can measure the insulation resistance values ​​of multiple branches at one time, and reduces the measurement cost; does not need to switch on and off resistors, will not affect the reduction of the actual insulation value during testing, can ignore the change of the DC input voltage, and improves the accuracy of the insulation value measurement result.

[0044] Optionally, Figure 2 The following is a schematic diagram of the insulation detection circuit structure of another inverter system provided by an embodiment of the present invention. Figure 2 As shown, the voltage adjustment module 100 includes a voltage adjustment unit 110 and a current limiting unit 120; the first end of the voltage adjustment unit 110 is connected to the protective grounding point PE, the second end of the voltage adjustment unit 110 and the first end of the current limiting unit 120 are commonly connected to the first node A, and the second end of the current limiting unit 120 is connected to the negative pole GND of the DC source 20.

[0045] Specifically, the first end of the voltage adjustment unit 110 is connected to the protective grounding point PE, and the second end of the voltage adjustment unit 110 is connected to the first node A. When the voltage of the voltage adjustment unit 110 changes, it can change the voltage on the first node A, the voltage on the n input branches, and the voltage on the output bus L0. With the protective grounding point PE as the voltage node, the voltage on the n input branches, the voltage on the output bus, and the voltage on the first node A as known quantities, the equivalent insulation resistance value of the n input branches relative to the protective grounding point PE, the equivalent insulation resistance value on the output bus relative to the protective grounding point PE, and the equivalent insulation resistance value between the common negative electrode GND of the n input branches and the protective grounding point PE as unknown quantities, and the equation is listed in combination with Kirchhoff's law. The voltage of the voltage adjustment unit 110 is adjusted n+2 times, thereby listing n+2 equations to solve the equivalent insulation resistance values ​​of the n input branches relative to the protective grounding point PE, the equivalent insulation resistance value of the output busbar relative to the protective grounding point PE, and the equivalent insulation resistance value between the common negative electrode GND of the n input branches and the protective grounding point PE.

[0046] Optionally, Figure 3 The following is a schematic diagram of the insulation detection circuit structure of another inverter system provided by an embodiment of the present invention. Figure 3 As shown, it also includes a sampling module 200 and a calculation module 300; the sampling end of the sampling module 200 is respectively connected to the input branch, the output bus L0 and the first node A; the output end of the sampling module 200 is connected to the calculation module 300; the sampling module 200 is used to obtain the voltage value of the input branch and the voltage value of the output bus L0 corresponding to the output value of each voltage adjustment module 100 under the output value of n+2 voltage adjustment modules 100; the calculation module 300 is used to substitute the output value of the voltage adjustment module 100, the corresponding voltage value of each input branch and the voltage value of the output bus L0 into a preset equation, wherein the unknown quantity of the preset equation is each equivalent insulation resistance; and the equivalent insulation resistance is determined according to the n+2 preset equations corresponding to the output values ​​of the n+2 voltage adjustment modules 100.

[0047] Specifically, the sampling module 200 may be a voltage sensor. The sampling module 200 may automatically detect and obtain the voltage value of the first node A of the voltage adjustment module 100 when the voltage adjustment changes, and the corresponding voltage value of the input branch and the voltage value of the output bus L0, and transmit n+2 sets of voltage information to the calculation module 300. The calculation module 300 may be a microprocessing unit. The calculation module 300 stores preset equations, substitutes the n+2 sets of voltage information obtained by the sampling module 200 into the preset equations, and calculates the equivalent insulation resistance between each input branch and the protective grounding point PE and the equivalent insulation resistance between the output bus L0 and the protective grounding point PE according to the n+2 preset equations.

[0048] The technical solution provided by the present invention can automatically obtain the voltage value of the input branch and the voltage value of the output bus corresponding to the output value of each voltage adjustment module through a sampling module; and substitute the output value of the voltage adjustment module, the corresponding voltage value of each input branch and the voltage value of the output bus into a preset equation through a calculation module, thereby automatically solving the equivalent insulation resistance between each input branch and the protective grounding point and the equivalent insulation resistance between the output bus and the protective grounding point. The technical solution provided by the present invention can automatically calculate the insulation resistance of multiple branches through a sampling module and a calculation module, further improving the efficiency of inverter insulation resistance detection.

[0049] Optionally, based on the above embodiment, Figure 2 The DC source 20 includes a photovoltaic panel and / or a battery, and the current limiting unit 120 includes a resistor r.

[0050] Specifically, the n DC sources 20 may all be photovoltaic panels, or all be batteries. When a portion of the n DC sources 20 are photovoltaic panels and another portion are batteries, the inverter 10 may be a hybrid inverter. The current limiting unit 120 may be a fixed resistor r, so that the current value of the branch where the voltage adjustment module 100 is located can be calculated based on the voltage value of the first node A and the fixed resistor r.

[0051] Figure 4 FIG. 1 is a flow chart of a method for detecting insulation value of an inverter system provided by the present invention. Figure 4 .like Figure 4 The method shown comprises:

[0052] S110, obtaining the voltage value of the input branch and the voltage value of the output bus corresponding to the output value of each voltage adjustment module under the output values ​​of n+2 voltage adjustment modules;

[0053] Specifically, when the output value of each voltage adjustment module is stable, the voltage value of the corresponding input branch and the voltage value of the output bus are obtained. A total of n+2 groups of output values ​​of voltage adjustment modules and the voltage values ​​of the input branches and the voltage values ​​of the output bus corresponding to the output values ​​are obtained.

[0054] S120, substituting the output value of the voltage adjustment module, the corresponding voltage values ​​of each input branch and the voltage value of the output bus into a preset equation, wherein the unknown quantity of the preset equation is each equivalent insulation resistance;

[0055] Specifically, the preset equation can be an equation listed according to Kirchhoff's current law with the protective grounding point PE as a node. The output value of the voltage adjustment module, the voltage value of each corresponding input branch and the voltage value of the output bus are used as known quantities, and the equivalent insulation resistance value between the n input branches and the protective grounding point PE, the equivalent insulation resistance value between the output bus and the protective grounding point PE, and the equivalent insulation resistance value between the common negative pole of the DC source and the protective grounding point PE are substituted into the preset equation as unknown quantities to obtain an n+2 variable linear equation.

[0056] S130 , determining an equivalent insulation resistance according to n+2 preset equations corresponding to the output values ​​of the n+2 voltage adjustment modules.

[0057] Specifically, the output values ​​of the n+2 groups of voltage adjustment modules, as well as the voltage values ​​of the input branches and the output busbars corresponding to the output values ​​are respectively substituted into the preset equations to obtain a total of n+2 linear equations. The equations are solved to obtain the equivalent insulation resistance value between each input branch and the protective grounding point PE, the equivalent insulation resistance value between the output busbar and the protective grounding point PE, and the equivalent insulation resistance value between the common negative pole of the DC source and the protective grounding point PE.

[0058] Optionally, Figure 5 FIG. 1 is a flow chart of another method for detecting the insulation value of an inverter system provided by the present invention. Figure 2 and Figure 5 The voltage adjustment module 100 includes a voltage adjustment unit 110 and a current limiting unit 120; a first end of the voltage adjustment unit 110 is connected to the protective grounding point PE, and a second end of the voltage adjustment unit 110 and a first end of the current limiting unit 120 are connected to a first node A. The current limiting unit 120 may be a fixed value resistor r. Figure 5 As shown, the method includes:

[0059] S210, setting the output value of the voltage adjustment unit;

[0060] Specifically, the voltage adjustment unit 110 may be a battery pack including a plurality of batteries, and the output value of the voltage adjustment unit is set by controlling the number of detection circuits connected to the battery pack.

[0061] S220, obtaining a voltage value of an input branch, a voltage value of an output bus, and a voltage value of a first node corresponding to an output value of a voltage adjustment module;

[0062] Specifically, after adjusting and setting the primary output value of the voltage adjustment unit 110, the voltage values ​​on the n input branches, the voltage value on the output bus and the voltage value of the first node corresponding to the output value can be respectively obtained through the sampling module 200, and the output value of the voltage adjustment unit 110, the voltage values ​​on the n input branches, the voltage value on the output bus and the voltage value of the first node can be transmitted to the calculation module as a set of voltage data.

[0063] S230, returning to the step of setting the output value of the voltage adjustment unit until the voltage values ​​of the input branches, the voltage value of the output bus, and the voltage value of the first node corresponding to n+2 groups of voltage adjustment modules at different output values ​​are obtained;

[0064] Specifically, the output value of the voltage adjustment unit 110 is readjusted, and the voltage values ​​on the n input branches, the voltage value on the output bus, and the voltage value of the first node corresponding to the output value are measured and obtained, and the output value of the voltage adjustment unit 110, the voltage values ​​on the n input branches, the voltage value on the output bus, and the voltage value of the first node after the readjustment are transmitted as the second set of voltage data. Steps S210 and S220 are repeated in sequence until n+2 sets of voltage data are obtained.

[0065] S240, substituting the output value of the voltage adjustment module, the corresponding voltage values ​​of each input branch and the voltage value of the output bus into a preset equation, wherein the unknown quantity of the preset equation is each equivalent insulation resistance;

[0066] S250 , determining equivalent insulation resistance according to n+2 preset equations corresponding to output values ​​of n+2 voltage adjustment modules.

[0067] Optionally, based on the above embodiment, the preset equation includes:

[0068] (U1x-Umx)*G1+...+(Unx-Umx)*Gn+(Ubx-Umx)*Gb-Umx*Gm-Uax*Gr=0;

[0069] Among them, Umx is the output value of the voltage adjustment module, Unx is the voltage value on the nth input branch corresponding to Umx, Ubx is the voltage value of the output bus corresponding to Umx, Uax is the voltage value of the first node, Gn is the reciprocal of the equivalent insulation resistance value on the nth input branch, Gb is the reciprocal of the equivalent insulation resistance value on the output bus, Gm is the reciprocal of the equivalent insulation resistance value on the protective grounding point, and Gr is the conductance value of the current limiting unit.

[0070] Specifically, Figure 2As shown, Umx is the voltage value between the protective earthing point PE and the common negative pole of the DC source. R is the equivalent insulation resistance value between the common negative pole of the DC source and the protective earthing point. The preset equation can be an equation listed according to Kirchhoff's current law with the protective earthing point PE as the node. Among them, (Unx-Umx)*Gn represents the current flowing into the protective earthing point PE from the input branch, (Ubx-Umx)*Gb represents the current flowing into the protective earthing point PE from the output bus, -Umx*Gm represents the current flowing into the protective earthing point PE from the common negative pole of the DC power supply, and -Uax*Gr represents the current flowing into the protective earthing point PE from the branch where the voltage adjustment module is located.

[0071] Optionally, Figure 6 FIG. 1 is a flow chart of another method for detecting the insulation value of an inverter system provided by the present invention. Figure 6 The method comprises:

[0072] S310, setting the output value of the voltage adjustment unit;

[0073] S320, obtaining a voltage value of an input branch, a voltage value of an output bus, and a voltage value of a first node corresponding to an output value of a voltage adjustment module;

[0074] S330, returning to the step of setting the output value of the voltage adjustment unit until the voltage values ​​of the input branches, the voltage value of the output bus, and the voltage value of the first node corresponding to n+2 groups of voltage adjustment modules at different output values ​​are obtained;

[0075] S340, substituting the output value of the voltage adjustment module, the corresponding voltage values ​​of each input branch and the voltage value of the output bus into a preset equation, wherein the unknown quantity of the preset equation is each equivalent insulation resistance;

[0076] S350. Arrange the n+2 preset equations in a matrix and solve the unknowns. The matrix expression is A*G+B=0; wherein G1, G2...Gn, Gb and Gm are the unknowns G to be solved, n+2 groups of U1x-Umx, U2x-Umx...Unx-Umx, Ubx-Umx and -Umx are the matrix coefficients A, and n+2 groups of -Uax*Gr are the constant terms B of the matrix.

[0077] Specifically, when solving the n+2 linear equations, the n+2 linear equations can be solved by matrix arrangement. For example, the voltage value of each PE branch flowing into the protective grounding point is used as the coefficient A of the matrix.

[0078] The current value flowing into the protective grounding point PE from the branch where the voltage adjustment module is located is taken as the constant term B of the matrix.

[0079] The insulation conductivity value of each branch flowing into the protective earthing point PE is taken as the unknown quantity G to be determined in the matrix.

[0080] in,

[0081] Optionally, based on the above embodiment, after arranging the n+2 preset equations in a matrix and solving the unknowns, the method further includes: finding the inverse of the matrix solution.

[0082] Specifically, the solutions obtained by the matrix A*G+B=0 are the insulation conductance values ​​between each of the n branches and the protective grounding point, the insulation conductance value between the output bus and the protective grounding point, and the insulation conductance value between the common negative pole of the DC source and the protective grounding point; the inverse of the solution obtained by the matrix A*G+B=0 is taken to finally obtain the insulation resistance value between each of the n branches and the protective grounding point, the insulation resistance value between the output bus and the protective grounding point, and the insulation resistance value between the common negative pole of the DC source and the protective grounding point.

[0083] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0084] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An insulation detection circuit of an inverter system, the inverter system comprising: Inverter, n input branches, output bus, DC source and protective grounding point; The first end of the input branch is connected to the input end of the inverter, the second end of the input branch is connected to the positive electrode of the DC source, and the output end of the inverter is connected to the output bus; There is an equivalent insulation resistance value between the input branch and the protective grounding point; characterized in that the insulation detection circuit comprises: a voltage adjustment module; The first end of the voltage adjustment module is connected to the protective grounding point, and the second end of the voltage adjustment module is connected to the negative electrode of the DC source; the voltage adjustment module is used to adjust the voltage values ​​of the n input branches and the voltage value of the output bus.

2. The insulation detection circuit of the inverter system according to claim 1, characterized in that: The voltage adjustment module includes a voltage adjustment unit and a current limiting unit; The first end of the voltage adjustment unit is connected to the protective grounding point, the second end of the voltage adjustment unit and the first end of the current limiting unit are commonly connected to a first node, and the second end of the current limiting unit is connected to the negative electrode of the DC source.

3. The insulation detection circuit of the inverter system according to claim 2, characterized in that: It also includes a sampling module and a calculation module; The sampling end of the sampling module is connected to the input branch, the output bus and the first node respectively; the output end of the sampling module is connected to the calculation module; The sampling module is used to obtain the voltage value of the input branch and the voltage value of the output bus corresponding to the output value of each voltage adjustment module under the output value of n+2 voltage adjustment modules; The calculation module is used to substitute the output value of the voltage adjustment module, the corresponding voltage values ​​of each input branch and the voltage value of the output bus into a preset equation, wherein the unknown quantity of the preset equation is each equivalent insulation resistance; and determine the equivalent insulation resistance according to the n+2 preset equations corresponding to the output values ​​of the n+2 voltage adjustment modules.

4. The insulation detection circuit of the inverter system according to claim 1, characterized in that: The DC source includes a photovoltaic panel and / or a battery.

5. The insulation detection circuit of the inverter system according to claim 2, characterized in that: The current limiting unit includes a resistor.

6. A method for detecting the insulation value of an inverter system, performed by the inverter insulation detection circuit according to any one of claims 1 to 5, characterized in that: include: Under the output values ​​of n+2 voltage adjustment modules, obtaining the voltage value of the input branch and the voltage value of the output bus corresponding to the output value of each voltage adjustment module; Substituting the output value of the voltage adjustment module, the corresponding voltage value of each input branch and the voltage value of the output bus into a preset equation, wherein the unknown quantity of the preset equation is each equivalent insulation resistance; The equivalent insulation resistance is determined according to the n+2 preset equations corresponding to the output values ​​of the n+2 voltage adjustment modules.

7. The method for detecting the insulation value of an inverter according to claim 6, characterized in that: The voltage adjustment module comprises a voltage adjustment unit and a current limiting unit; a first end of the voltage adjustment unit is connected to the protection grounding point, and a second end of the voltage adjustment unit and a first end of the current limiting unit are connected to a first node together; Under the output values ​​of n+2 voltage adjustment modules, obtaining the voltage value of the input branch and the voltage value of the output bus corresponding to the output value of each voltage adjustment module includes: Set the output value of the voltage adjustment unit; Obtaining a voltage value of the input branch, a voltage value of the output bus, and a voltage value of the first node corresponding to an output value of the voltage adjustment module; Return to the step of setting the output value of the voltage adjustment unit until the voltage values ​​of the input branches, the output bus and the first node corresponding to a total of n+2 groups of the voltage adjustment modules at different output values ​​are obtained.

8. The method for detecting the insulation value of an inverter according to claim 7, characterized in that: The preset equation includes: (U1x-Umx)*G1+...+(Unx-Umx)*Gn+(Ubx-Umx)*Gb-Umx*Gm-Uax*Gr=0; Among them, Umx is the output value of the voltage adjustment module, Unx is the voltage value on the nth input branch corresponding to Umx, Ubx is the voltage value of the output bus corresponding to Umx, Uax is the voltage value of the first node, Gn is the reciprocal of the equivalent insulation resistance value on the nth input branch, Gb is the reciprocal of the equivalent insulation resistance value on the output bus, Gm is the reciprocal of the equivalent insulation resistance value at the protective grounding point, and Gr is the conductance value of the current limiting unit.

9. The method for detecting the insulation value of an inverter according to claim 8, characterized in that: Determining the equivalent insulation resistance according to the n+2 preset equations corresponding to the output values ​​of the n+2 voltage adjustment modules includes: Arrange the n+2 preset equations in a matrix and solve the unknowns, wherein the matrix expression is A*G+B=0; Among them, G1, G2...Gn, Gb and Gm are the unknown quantities G to be determined, n+2 groups U1x-Umx, U2x-Umx...Unx-Umx, Ubx-Umx and -Umx are the coefficients of the matrix A, and n+2 groups -Uax*Gr are the constant terms B of the matrix.

10. The method for detecting the insulation value of an inverter according to claim 9, characterized in that: After arranging the n+2 preset equations in a matrix and solving the unknown quantity, the method further includes: The solution to the matrix is ​​inverted.

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