Insulation resistance detection method, device and electronic equipment

Abstract

The application provides an insulation resistance detection method and device and electronic equipment. The method comprises: adjusting a test loop topology state of the insulation resistance detection system to construct multiple different detection conditions; acquiring a measurement ratio of a positive pole-to-ground voltage and a negative pole-to-ground voltage of the DC bus under each detection condition; determining a fitting ratio between an equivalent parallel resistance of the positive pole-to-ground and an equivalent parallel resistance of the negative pole under each detection condition based on a preset resistance measurement model; constructing a cost model according to the measurement ratio and the fitting ratio; determining initial values of the positive pole-to-ground insulation resistance and the negative pole-to-ground insulation resistance based on the measurement ratio and the fitting ratio, iteratively updating the cost model, and outputting final values. The application can realize online detection of the DC bus insulation resistance under complex operating conditions.

Description

Technical Field

[0001] This invention relates to the field of insulation testing technology for high-voltage direct current systems, and particularly to an insulation resistance testing method, apparatus, and electronic equipment. Background Technology

[0002] In high-voltage DC systems such as photovoltaic inverters and energy storage systems, the DC bus voltage typically ranges from 300V to 1500V. To ensure safe equipment operation, real-time monitoring of the insulation status between the DC bus and ground is necessary. For example... Figure 1 As shown, under normal circumstances, the insulation to ground can be equivalent to two insulation resistances: the insulation resistance of BUS+ to ground and the insulation resistance of BUS- to ground. That is, the positive insulation resistance Rx corresponding to the positive terminal of the busbar to ground and the negative insulation resistance Ry corresponding to the negative terminal of the busbar to ground. When either insulation resistance decreases, it indicates that there is a problem of leakage to ground or insulation degradation in the system.

[0003] Currently, existing insulation testing technologies mainly employ current injection and voltage judgment methods. The current injection method involves injecting a small current into the circuit, superimposed with a voltage sampling circuit, and then calculating the resistance value using Ohm's law. The voltage judgment method, on the other hand, compares the sampled voltage with the voltage under normal operating conditions to determine if there is any resistance failure. Furthermore, traditional insulation resistance calculations typically rely on direct calculations based on single voltage relationships.

[0004] However, the current injection method requires expensive circuitry, and voltage-based methods can only roughly determine the presence of insulation faults, making it difficult to accurately estimate the insulation resistance of both the positive and negative terminals simultaneously. They often only provide an overall insulation level or a single-sided estimate, making it difficult to pinpoint the specific faulty side. Finally, schemes that rely on direct calculations based on single voltage relationships have weak noise immunity when encountering sampling fluctuations, common-mode noise, or local measurement instability. Furthermore, when the sampled voltage is too low under certain operating conditions, previous schemes are prone to problems such as an excessively small denominator and divergent results, leading to numerical distortion. Summary of the Invention

[0005] The purpose of this invention is to provide an insulation resistance detection method, device, and electronic equipment to solve the problem of difficulty in simultaneously and accurately estimating the insulation resistance of both the positive and negative poles.

[0006] According to a first aspect of the present invention, an insulation resistance detection method is provided, applied to an insulation resistance detection system connected to a DC bus, the DC bus having a positive-to-ground insulation resistance and a negative-to-ground insulation resistance to be measured, characterized in that: the method includes: Adjust the test circuit topology of the insulation resistance detection system to construct multiple different detection conditions; Under each testing condition, the measured ratio of the positive terminal voltage to ground voltage and the negative terminal voltage to ground voltage of the DC bus is obtained. Based on the preset resistance measurement model, the ratio between the equivalent parallel resistance of the positive electrode to ground and the equivalent parallel resistance of the negative electrode under each detection condition is determined as the fitting ratio characterizing the theoretical voltage ratio. Based on the measurement ratio and the fitting ratio, a cost model reflecting the overall fitting error is constructed. Based on the measured ratio and the fitted ratio, the initial values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance are determined. Starting from these initial values, the cost model is iteratively updated until the convergence condition is met, and then the final values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance are output.

[0007] In some possible implementations, the insulation resistance detection system includes a first detection circuit connected between the positive terminal of the DC bus and the reference potential terminal, and a second detection circuit connected between the negative terminal of the DC bus and the reference potential terminal. The first detection circuit includes a first resistor on the positive side, a second resistor on the positive side, and a first switch connected in parallel to the second resistor on the positive side; The second detection circuit includes a first resistor on the negative side, a second resistor on the negative side connected in series, and a second switch connected in parallel with the second resistor on the negative side; The adjustment of the test circuit topology of the insulation resistance detection system to construct multiple different detection conditions includes: The on / off states of the first switch and the second switch are controlled to construct multiple different detection conditions.

[0008] In some possible implementations, controlling the on / off states of the first switch and the second switch to construct multiple detection conditions includes: According to a predetermined sequence, the on / off combination of the first switch and the second switch is changed sequentially to construct the first detection condition, the second detection condition, the third detection condition and the fourth detection condition; The first detection condition is defined as: the first switch is open, and the second switch is open. The second detection condition is defined as follows: the first switch is on, and the second switch is off; The third detection condition is defined as follows: the first switch is open, and the second switch is on. The fourth detection condition is defined as follows: the first switch is on, and the second switch is on.

[0009] In some possible implementations, after acquiring the DC bus positive-to-ground voltage and negative-to-ground voltage under each detection condition, the method further includes: The DC bus positive-to-ground voltage and negative-to-ground voltage under each detection condition are compared with the preset minimum effective threshold. If any voltage of the first detection circuit or the second detection circuit is less than the preset minimum effective threshold, the corresponding detection condition is determined to be an invalid condition, and after removing the invalid condition, the remaining valid conditions are extracted.

[0010] In some possible implementations, if the number of valid operating conditions is less than three, an insulation resistance failure is determined, and the detection process is terminated.

[0011] In some possible implementations, based on a preset resistance measurement model, the ratio between the equivalent parallel resistance of the positive electrode to ground and the equivalent parallel resistance of the negative electrode under each detection condition is determined as a fitting ratio characterizing the theoretical voltage ratio, including: Based on the conduction or disconnection of the first switch and the second switch under the corresponding detection conditions, the first equivalent access resistance of the first detection circuit and the second equivalent access resistance of the second detection circuit are determined. The ratio of the parallel resistance of the positive electrode to ground insulation resistance and the first equivalent connection resistance to the parallel resistance of the negative electrode to ground insulation resistance and the second equivalent connection resistance to the ground is used as the fitting ratio for the corresponding detection condition.

[0012] In some possible implementations, determining the initial values ​​of the positive-to-ground insulation resistance and the negative-to-ground insulation resistance based on the measured ratio and the fitted ratio includes: Determine the number and type of the extracted valid working conditions; Based on the number and type of effective working conditions, the intermediate variables for measuring the positive electrode, measuring the negative electrode, fitting the positive electrode intermediate variable, and fitting the negative electrode intermediate variable are constructed respectively. Based on the measurement ratio under the corresponding effective working conditions, determine the intermediate variable of the positive electrode and the intermediate variable of the negative electrode. Under the condition that the measured ratio is equal to the fitted ratio, the initial values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance are determined based on the resistance measurement model.

[0013] In some possible implementations, when the number of effective operating conditions is four, the intermediate variable for measuring the positive electrode is constructed based on the number and type of effective operating conditions as follows: ; The intermediate variable for measuring the negative electrode is constructed as follows: ; The fitted positive intermediate variable is constructed as follows: ; The fitted negative intermediate variable is constructed as follows: = ; in, , , , These are the measurement ratios under the first to fourth testing conditions, respectively. , , , These represent the fitting ratios for the first to fourth detection conditions, respectively. c represents the intermediate variable measured at the positive electrode; To measure the intermediate variable at the negative pole; To fit the positive intermediate variable; To fit the negative intermediate variable; This is the initial value of the insulation resistance between the positive terminal and ground; This is the initial value of the insulation resistance between the negative electrode and ground; R1 is the first resistor on the positive side; R2 is the second resistor on the positive side. R1 is the first resistor on the negative side; R4 is the second resistor on the negative side. This indicates the operation of resistors in parallel.

[0014] In some possible implementations, when the number of effective operating conditions is three, the construction of the intermediate variables for measuring the positive electrode and the intermediate variables for measuring the negative electrode, based on the number and type of effective operating conditions, includes: When the first detection condition is invalid , ; When the second detection condition is invalid , ; When the third detection condition is invalid , ; When the fourth detection condition is invalid , ; Based on the number and type of effective operating conditions, the positive and negative intermediate variables for fitting are constructed as follows: When the first detection condition is invalid , ; When the second detection condition is invalid , ; When the third detection condition is invalid , ; When the fourth detection condition is invalid , ; in, , , , These are the measurement ratios under the first to fourth testing conditions, respectively. , , , These represent the fitting ratios for the first to fourth detection conditions, respectively. c represents the intermediate variable measured at the positive electrode; To measure the intermediate variable at the negative pole; To fit the positive intermediate variable; To fit the negative intermediate variable.

[0015] In some possible implementations, the method further includes, before constructing a cost model reflecting the overall fitting error based on the measurement ratio and the fitting ratio: Extract the smaller value between the voltages of the first and second detection circuits under the corresponding detection conditions, and determine the weight of the corresponding detection condition based on the square of the smaller value.

[0016] In some possible implementations, a cost model reflecting the overall fitting error, constructed based on the measurement ratio and the fitting ratio, is expressed as follows: ; in, For the first The weights corresponding to each detection condition For the first The fitting ratio under each detection condition For the first The measurement ratio under each testing condition.

[0017] In some possible implementations, the cost model is iteratively updated until the convergence condition is met, and then the final values ​​of the positive-to-ground insulation resistance and the negative-to-ground insulation resistance are output, including: The current estimated values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance are input into the cost model to obtain the current error, and the direction of change and adjustment step size of the current estimated value are determined. Based on the direction of change and the adjustment step size, the current estimated value is updated to obtain a candidate estimated value, and the update error of the candidate estimated value under the cost model is obtained; If the update error is less than or equal to the current error, the candidate estimate is accepted as the new current estimate and the iteration continues. It is then determined whether the new current estimate satisfies the convergence condition. If it does, the iteration is terminated and the corresponding new current estimate is output as the final value. If it does not, the iteration returns to the step of obtaining the current error to continue the iteration. If the update error is greater than the current error, then the candidate estimate is rejected, the current estimate before the update is retained as the final value, and the iteration is terminated. The convergence conditions include: the update error is less than or equal to a preset error threshold, and / or the number of iterations reaches a preset maximum number.

[0018] In some possible implementations, determining the direction of change and adjustment step size of the current estimate includes: By performing first-order linearization on the cost model near the parameter point corresponding to the current estimate, and based on the weighted least squares criterion, the change direction and adjustment step size of the positive electrode to ground insulation resistance and the change direction and adjustment step size of the negative electrode to ground insulation resistance are calculated respectively. The direction of change and adjustment step size of the positive electrode's insulation resistance to ground are expressed as follows: ; The direction of change and adjustment step size of the insulation resistance between the negative electrode and ground are expressed as follows: ; in, ; ; ; ; ; .

[0019] According to a second aspect of the present invention, an insulation resistance detection device is provided, comprising: The working condition construction module is used to adjust the test circuit topology of the insulation resistance detection system and construct multiple different detection working conditions. The measurement ratio acquisition module is used to acquire the measurement ratio of the positive terminal voltage to ground and the negative terminal voltage to ground of the DC bus under various detection conditions. The fitting ratio acquisition module is used to determine the ratio between the equivalent parallel resistance of the positive electrode to ground and the equivalent parallel resistance of the negative electrode under each detection condition based on a preset resistance measurement model, and to use it as a fitting ratio characterizing the theoretical voltage ratio. The cost model construction module is used to construct a cost model that reflects the overall fitting error based on the measurement ratio and the fitting ratio. The iterative solution module is used to determine the initial values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance based on the measured ratio and the fitted ratio, and to iteratively update the cost model from these initial values ​​until the convergence condition is met, and then output the final values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance.

[0020] According to a third aspect of the present invention, an electronic device is provided, comprising: an input unit, a memory, at least one processor, and an output interface, wherein the memory stores program instructions executable on the processor, and the processor can execute an insulation resistance detection method by calling the program instructions.

[0021] According to the present invention, multiple detection conditions are constructed by controlling the on and off states of switching devices in the test circuit. Without interrupting the DC bus power supply, a cost model reflecting the overall fitting error is constructed using only the voltage ratio characteristics under each condition. Then, the positive-to-ground insulation resistance and negative-to-ground insulation resistance are solved synchronously through iterative updates. This eliminates the need for additional high-voltage AC signals or complex hardware bridge arms, reducing hardware cost and size, and enabling online real-time detection of insulation impedance under complex operating conditions where the power supply equipment is energized. Attached Figure Description

[0022] Figure 1 A schematic diagram of the equivalent model of the insulation resistance of a DC bus to ground; Figure 2 A schematic diagram of the topology of the DC bus insulation resistance detection circuit in the power supply equipment provided in the embodiments of this application; Figure 3 This is a flowchart illustrating the steps of an insulation resistance testing method according to an embodiment of this application. Figure 4 A schematic diagram of an effective working condition screening process provided for an embodiment of this application; Figure 5 This application provides a schematic diagram of a process for determining an initial value according to an embodiment of the present application. Figure 6 This is a schematic diagram illustrating an iterative update process for a cost model, provided as an embodiment of this application. Figure 7 This is a unit block diagram of an insulation resistance detection device according to an embodiment of this application; Figure 8 This is a block diagram of an electronic device according to an embodiment of this application. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the application. The singular forms “a,” “said,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0025] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0026] It should be understood that although the terms first, second, third, etc., may be used in the embodiments of this application, these descriptions should not be limited to these terms. These terms are only used to distinguish the descriptions. For example, first may also be referred to as second without departing from the scope of the embodiments of this application, and similarly, second may also be referred to as first.

[0027] Depending on the context, the words “if” or “suppose” as used here can be interpreted as “when” or “in response to determination” or “in response to detection.” Similarly, depending on the context, the phrases “if determination” or “if detection (of the stated condition or event)” can be interpreted as “when determination” or “in response to determination” or “when detection (of the stated condition or event)” or “in response to detection (of the stated condition or event).”

[0028] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0029] It should be noted that any symbols and / or numbers present in the specification that are not marked in the accompanying drawings are not reference numerals.

[0030] The optional embodiments of this application are described in detail below with reference to the accompanying drawings.

[0031] To facilitate understanding of the insulation resistance detection method provided in the embodiments of this application, the hardware interaction architecture and circuit topology on which this method depends will be described below.

[0032] Please see Figure 2 , Figure 2 A schematic diagram of the circuit topology of an insulation resistance detection system is shown. The insulation resistance detection system 10 is connected to the DC bus 11.

[0033] In the embodiments of this application, the insulation resistance detection system 10 can have various specific physical product forms or application scenarios. For example, the insulation resistance detection system 10 can be set up independently as an insulation monitoring device (IMD), or it can be integrated into or applied to various systems involving DC insulation detection, such as the battery management system (BMS) of electric vehicles, the energy storage converter (PCS) of energy storage systems, high-power DC charging piles, photovoltaic inverter systems, uninterruptible power supplies (UPS), and DC microgrids.

[0034] At the topological level, there is an equivalent positive-to-ground insulation resistance Rx between the positive terminal of DC bus 11 and the reference potential terminal (such as vehicle chassis, equipment metal casing or reference ground), and there is an equivalent negative-to-ground insulation resistance Ry between the negative terminal of DC bus 11 and the reference potential terminal.

[0035] In one optional circuit topology implementation, the insulation resistance detection system 10 includes a first detection circuit 12 and a second detection circuit 13. The first detection circuit 12 is connected between the positive terminal of the DC bus 11 and the reference potential terminal, and the second detection circuit 13 is connected between the negative terminal of the DC bus 11 and the reference potential terminal. In addition, a first switch S1 is provided on the first detection circuit 12, and a second switch S2 is provided on the second detection circuit 13, which is used to change the physical topology of the detection circuit by switching the on and off states of the first switch S1 and the second switch S2.

[0036] Based on the above hardware interaction architecture and circuit topology, this application provides an insulation resistance detection method. Figure 3 A flowchart illustrating an insulation resistance testing method is shown, which includes the following steps: S101, Adjust the test circuit topology of the insulation resistance detection system to construct multiple different detection conditions; The testing condition refers to the state of different physical measurement circuit topologies and connected resistance values ​​formed by changing the on or off states of the first detection circuit 12 and the second detection circuit 13 during the insulation resistance testing process.

[0037] Combination Figure 2 The circuit topology shown provides a detailed explanation of the specific structure of the first detection circuit 12 and the second detection circuit 13, as well as the construction process for various detection conditions: The first detection circuit 12 includes a first resistor and a second resistor connected in series on the positive side, and a first switch S1 connected in parallel with the second resistor on the positive side. The second detection circuit 13 includes a first resistor and a second resistor connected in series on the negative side, and a second switch S2 connected in parallel with the second resistor on the negative side.

[0038] It should be noted that, in order to simplify the resistance measurement model and reduce the computational complexity, the first detection circuit 12 and the second detection circuit 13 can adopt a symmetrical hardware parameter design, that is, the resistance values ​​of the first resistor on the positive side and the first resistor on the negative side are the same (R1=R3), and the resistance values ​​of the second resistor on the positive side and the second resistor on the negative side are the same (R2=R4).

[0039] When changing the on / off state of the first switch S1 and the second switch S2, the on / off combinations of the first switch S1 and the second switch S2 can be changed sequentially according to a predetermined timing sequence, and the constructed detection conditions include: First test condition: First switch S1 is open, and second switch S2 is open. Under this test condition, neither the second resistor on the positive side nor the second resistor on the negative side is short-circuited. The first resistor on the positive side and the second resistor on the positive side are connected in series in the test circuit, and the first resistor on the negative side and the second resistor on the negative side are connected in series in the test circuit.

[0040] Second testing condition: First switch S1 is on, and second switch S2 is off. Under this condition, the second resistor on the positive side is short-circuited by the closed first switch S1, and only the first resistor on the positive side is connected to the test circuit; the first resistor on the negative side and the second resistor on the negative side are connected in series to the test circuit.

[0041] Third testing condition: First switch S1 is open, and second switch S2 is closed. Under this condition, the first resistor on the positive side and the second resistor on the positive side are connected in series in the test circuit; the second resistor on the negative side is short-circuited by the closed second switch S2, and only the first resistor on the negative side is connected to the negative side of the test circuit.

[0042] Fourth testing condition: First switch S1 is on, and second switch S2 is on. Under this condition, the second resistor on the positive side and the second resistor on the negative side are short-circuited by their respective switches, and only the corresponding first resistor is connected to both the positive and negative sides of the test circuit.

[0043] In actual operating condition switching control, in order to avoid voltage fluctuations and measurement errors caused by the transient switching of switches (such as relays or solid-state switches), a predetermined stabilization waiting time can be set after each detection operating condition switch. After the circuit voltage division state is completely stable, the next step of voltage sampling can be performed.

[0044] S102, respectively acquire the measured ratio of the DC bus positive terminal to ground voltage to the negative terminal to ground voltage under each detection condition; Under each constructed testing condition, the total voltage (Vbus) between the positive and negative terminals of the DC bus 11 and the detection voltage (Viso) of the insulation detection node are obtained through voltage sampling, i.e., the voltage of the second detection circuit 13. Since the first detection circuit 12 and the second detection circuit 13 together form a voltage divider circuit, the voltage of the first detection circuit 12 can be obtained by subtracting the detection voltage from the total voltage. Based on the total voltage and the detection voltage, the voltages of the first detection circuit 12 and the second detection circuit 13 can be determined, i.e., the positive terminal voltage to ground and the negative terminal voltage to ground of the DC bus 11, which can be specifically expressed as: ; ; in, For the first Under each testing condition, the positive terminal to ground voltage of DC bus 11; For the first Total voltage under each detection condition; For the first Detection voltage under various detection conditions; For the first Under a specific testing condition, the negative terminal voltage of DC bus 11 to ground.

[0045] After determining the positive-to-ground voltage and the negative-to-ground voltage of DC bus 11, the measurement ratio can be obtained: ; in, For the first The ratio of the positive voltage to ground to the negative voltage to ground of DC bus 11 under each testing condition.

[0046] To improve the anti-interference capability under complex electromagnetic environments (such as sampling fluctuations and common-mode noise) and avoid result divergence caused by the denominator of the ratio approaching zero due to excessively low local sampling voltage, after obtaining the positive-to-ground voltage and negative-to-ground voltage of DC bus 11 under each detection condition, it is necessary to extract the effective conditions. The extraction process is as follows: Figure 4 As shown, it includes: The positive and negative voltages of DC bus 11 to ground under each test condition are compared with the preset minimum effective threshold. If either the positive voltage to ground or the negative voltage to ground is less than the preset minimum effective threshold, the corresponding detection condition is determined to be invalid. After removing invalid conditions, the remaining valid conditions are extracted, and subsequent steps are performed based on the remaining valid conditions.

[0047] If, after eliminating invalid operating conditions, the number of remaining valid operating conditions is less than three, it indicates that the dimensions of the remaining valid equations are insufficient to support the bivariate solution of the positive-to-ground insulation resistance Rx and the negative-to-ground insulation resistance Ry. In this case, an insulation impedance failure fault is directly determined, and the subsequent detection process is immediately terminated.

[0048] It should be noted that the minimum effective threshold can be set according to the specific needs of the detection process, and is not limited here.

[0049] S103, based on the preset resistance measurement model, determines the ratio between the equivalent parallel resistance of the positive electrode to ground and the equivalent parallel resistance of the negative electrode under each detection condition, as a fitting ratio characterizing the theoretical voltage ratio; Based on the switching of the states of the first switch S1 and the second switch S2 under different detection conditions, the physical topology of the test circuit changes. Therefore, it is necessary to determine the first equivalent connection resistance of the first detection circuit 12 and the second equivalent connection resistance of the second detection circuit 13 based on the on or off states of the first switch S1 and the second switch S2 under the corresponding detection conditions.

[0050] In the first detection condition, both the first switch S1 and the second switch S2 are open. At this time, the first equivalent connection resistance is the first resistance on the positive side plus the second resistance on the positive side (R1+R2), and the second equivalent connection resistance is the first resistance on the negative side plus the second resistance on the negative side (R3+R4). In the second detection condition, the first switch S1 is turned on and the second switch S2 is turned off. At this time, the first equivalent connection resistance is the first resistance on the positive side (R1), and the second equivalent connection resistance is the first resistance on the negative side plus the second resistance on the negative side (R3+R4). In the third detection condition, the first switch S1 is open and the second switch S2 is open. At this time, the first equivalent connection resistance is the first resistance on the positive side plus the second resistance on the positive side (R1+R2), and the second equivalent connection resistance is the first resistance on the negative side (R3). In the fourth detection condition, both the first switch S1 and the second switch S2 are turned on. At this time, the first equivalent connection resistance is the first resistance (R1) on the positive side, and the second equivalent connection resistance is the first resistance (R3) on the negative side.

[0051] After determining the first equivalent connection resistance and the second equivalent connection resistance corresponding to each testing condition, the ratio of the parallel resistance of the positive electrode to ground insulation resistance Rx to the first equivalent connection resistance to the parallel resistance of the negative electrode to ground insulation resistance Ry to the second equivalent connection resistance to the parallel resistance of the negative electrode to ground insulation resistance ...

[0052] Under the first testing condition, the parallel resistance value of the positive electrode-to-ground insulation resistance Rx and the first equivalent connection resistance is expressed as: ; The parallel resistance value of the negative electrode insulation resistance to ground Ry and the second equivalent connection resistance is expressed as: ; Under the second testing condition, the parallel resistance value of the positive electrode-to-ground insulation resistance Rx and the first equivalent connection resistance is expressed as: ; The parallel resistance value of the negative electrode insulation resistance to ground Ry and the second equivalent connection resistance is expressed as: ; Under the third testing condition, the parallel resistance value of the positive electrode-to-ground insulation resistance Rx and the first equivalent connection resistance is expressed as: ; The parallel resistance value of the negative electrode insulation resistance to ground Ry and the second equivalent connection resistance is expressed as: ; Under the fourth detection condition, the parallel resistance value of the positive electrode-to-ground insulation resistance Rx and the first equivalent connection resistance is expressed as: ; The parallel resistance value of the negative electrode insulation resistance to ground Ry and the second equivalent connection resistance is expressed as: ; That is, the fitting ratio corresponding to each detection condition is expressed as: ; in, For the first The parallel resistance value of the positive electrode insulation resistance to ground and the first equivalent connection resistance under each testing condition. For the first The parallel resistance value of the negative electrode insulation resistance to ground and the second equivalent connection resistance under each testing condition. For the first Fit ratio under each detection condition.

[0053] It should be noted that, according to the series voltage divider principle of DC steady-state circuits, the voltage ratio of each branch in the circuit should be strictly equal to the ratio of their corresponding equivalent resistances. The fitting ratio corresponding to the ratio of equivalent parallel resistances under each detection condition, calculated through the resistance measurement model, is... In terms of the algorithm's physical logic, this represents the theoretical voltage ratio under this topological state. Under ideal, error-free conditions, this fitted ratio should be equal to the measured ratio obtained from actual sampling. Based on the measured ratio Ratio of fit Based on this equivalent correspondence, the insulation resistance detection system 10 can utilize the difference measure between the two to construct a cost model reflecting the overall fitting error in subsequent steps, thereby achieving iterative optimization of the true value of insulation resistance.

[0054] To facilitate understanding of the physical correlation between the fitting ratio and the aforementioned measurement ratio, the following is combined with... Figure 2 The circuit topology shown will be described in detail: like Figure 2 As shown, under any specific testing condition, the insulation resistance testing system 10 and the insulation resistance of the positive electrode to ground to be tested are... and the insulation resistance of the negative electrode to ground Together, they form a closed DC series voltage divider circuit. Specifically, the current starts from the positive terminal (BUS+) of DC bus 11 and flows through the insulation resistance between the positive terminal and ground. The positive-to-ground parallel network formed by the first detection circuit 12 (which exhibits different equivalent connection resistances depending on the on / off state of the first switch S1) converges at the reference potential terminal. Subsequently, current flows from the reference potential terminal through the negative-to-ground insulation resistance... The negative terminal of the circuit, which is connected in parallel with the ground to form a negative terminal network with the second detection circuit 13 (which presents different equivalent connection resistances depending on the on / off state of the second switch S2), eventually flows back to the negative terminal (BUS-) of the DC bus 11.

[0055] According to Kirchhoff's current law, under steady-state conditions, the total current flowing through the positive-to-ground parallel network is equal to the total current flowing through the negative-to-ground parallel network. Based on Ohm's law, the ratio of the positive-to-ground voltage (i.e., the voltage across the positive-to-ground parallel network) to the negative-to-ground voltage (i.e., the voltage across the negative-to-ground parallel network) of DC bus 11 is numerically equal to the equivalent parallel resistance of the positive-to-ground network. Equivalent parallel resistance to ground with negative electrode The ratio of .

[0056] Therefore, the fitting ratio calculated by the resistance measurement model in this step is essentially a simulation of the theoretical voltage ratio between the positive and negative poles of the DC bus and ground under this operating condition. Under ideal conditions of accurate hardware sampling and measurement, the actual measured ratio is calculated from the total voltage and the detected voltage. The fitting ratio obtained from the theoretical simulation equal.

[0057] S104, Based on the measurement ratio and the fitting ratio, construct a cost model that reflects the overall fitting error; Considering that there may be local common-mode interference or low local voltage sampling signal-to-noise ratio in the actual operating environment, in order to further improve the robustness and anti-interference ability of the cost model in the iterative solution process, before constructing the cost model reflecting the overall fitting error based on the measurement ratio and fitting ratio, weights can be dynamically assigned to each detection condition.

[0058] For each detection condition involved in the processing, the smaller value (i.e., the positive terminal to ground voltage Vx) of the voltages of the first detection circuit 12 and the second detection circuit 13 under the corresponding detection condition is extracted. i Voltage Vy of negative terminal to ground i The smaller value in the range is used to determine the weight of the corresponding detection condition based on the squared feature of the smaller value. ; in, For the first The weights corresponding to each detection condition The first The positive and negative voltages of the DC bus to ground under the test conditions.

[0059] By assigning weights to each detection condition, when a local common-mode interference on one side of a certain detection condition causes the sampling voltage to be too low, the proportion of the low-confidence condition in the overall solution can be reduced adaptively and exponentially by using the square of the smaller voltage as the weight, thereby effectively suppressing the impact of abnormal data on the global model.

[0060] It should be noted that, unlike traditional data fusion algorithms which typically require the sum of all weights to be normalized to 1, this embodiment uses weights... It is not used for regular weighted summation and averaging operations, but rather as a relative penalty coefficient for the cost model under the weighted least squares criterion.

[0061] In the mathematical essence of algorithmic iterative optimization, the core purpose of constructing a cost model is to find the extreme point that minimizes the error by differentiating the model. According to optimization theory, scaling the weights of each term in the objective function proportionally (i.e., normalized division) does not change the location of the extreme point (i.e., the initial value or update step size of the final output) algebraically. Therefore, this embodiment directly uses the squared features with smaller values ​​as absolute weights in the construction of the cost model, and the sum of the weights of each detection condition does not need to be equal to 1.

[0062] After determining the weights of the corresponding testing conditions, the difference measurement features between the measurement ratio and the fitting ratio under each testing condition can be obtained. Then, using the weights of the corresponding testing conditions, the difference measurement features are weighted and fused to construct a cost model that reflects the overall fitting error. ; in, For the first The weights corresponding to each detection condition For the first The fitting ratio under each detection condition For the first The measurement ratio under each testing condition.

[0063] S105, Based on the measured ratio and the fitted ratio, determine the initial values ​​of the positive electrode to ground insulation resistance and the negative electrode to ground insulation resistance, and use these as the starting point to iteratively update the cost model until the convergence condition is met, and then output the final values ​​of the positive electrode to ground insulation resistance and the negative electrode to ground insulation resistance. Cost models (such as weighted least squares objective functions) are typically nonlinear, making it difficult to directly solve for accurate resistance values ​​analytically. Therefore, a numerical optimization iteration is introduced. The specific execution logic is as follows: First, initial values ​​are assigned to the positive-to-ground and negative-to-ground insulation resistances. Then, these initial values ​​are substituted into the cost model to calculate the current fitting error, and the adjustment step size for the resistance value is determined based on the gradient direction of the error descent. Next, the current resistance estimate is updated using this step size, and the above error calculation and updating process is repeated continuously. When the iteration process meets the preset convergence condition, the optimal solution is determined, the iteration stops, and the current corresponding resistance value is output as the final positive-to-ground and negative-to-ground insulation resistances.

[0064] During the iteration process, the accuracy of the final value depends on the given initial value. If the initial value deviates too much from the true value, it can easily lead to iteration divergence or getting trapped in a local minimum. The initial value extraction process for the positive-to-ground insulation resistance and the negative-to-ground insulation resistance is as follows: Figure 5 As shown, it includes: Determine the number and type of valid operating conditions to be extracted; Based on the number and type of effective working conditions, the intermediate variables for measuring the positive electrode, measuring the negative electrode, fitting the positive electrode intermediate variable, and fitting the negative electrode intermediate variable are constructed respectively. Based on the measurement ratio under the corresponding effective working conditions, determine the intermediate variable of the positive electrode and the intermediate variable of the negative electrode. Under the condition that the measured ratio is equal to the fitted ratio, the initial values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance are determined based on the resistance measurement model.

[0065] First, determine and extract the number and type of the current valid detection conditions. Since different combinations of valid conditions correspond to different test loop topology states, the processor needs to match the corresponding algebraic analytical expression based on the actual distribution of valid conditions.

[0066] After determining the number and type of effective operating conditions, two sets of intermediate variables were constructed independently: one set was the measurement positive and negative intermediate variables calculated based on the actual sampling voltage; the other set was the fitting positive and negative intermediate variables derived based on the pure resistance value of the circuit structure.

[0067] Based on the series voltage divider principle of the aforementioned DC steady-state circuit, under ideal boundary conditions of accurate measurement and sampling, the actual measured ratio is... Fit ratio with theoretical derivation They are equal, therefore, based on the measured ratio There exists a one-to-one correspondence between the calculated intermediate measurement variables and the fitted intermediate variables constructed from the pure resistance formula, i.e., under the ideal boundary conditions of accurate sampling. = .

[0068] The initial value can be obtained by performing inverse feature matching based on equivalence relations.

[0069] Specifically, when there are four valid operating conditions, the intermediate variable for measuring the positive electrode is constructed based on the number and type of valid operating conditions as follows: ; The intermediate variable for measuring the negative electrode is constructed as follows: ; The fitted positive intermediate variable is constructed as follows: ; The fitted negative intermediate variable is constructed as follows: = ; in, , , , These are the measurement ratios under the first to fourth testing conditions, respectively. , , , These represent the fitting ratios for the first to fourth detection conditions, respectively. c represents the intermediate variable measured at the positive electrode; To measure the intermediate variable at the negative pole; To fit the positive intermediate variable; To fit the negative intermediate variable; This is the initial value of the insulation resistance between the positive terminal and ground; This is the initial value of the insulation resistance between the negative electrode and ground; R1 is the first resistor on the positive side; R2 is the resistance value of the first resistor on the negative side; R1 is the second resistor on the positive side; R4 is the resistance value of the second resistor on the negative side; This indicates the operation of resistors in parallel.

[0070] When there are three valid operating conditions, the intermediate variables for measuring the positive electrode and the intermediate variables for measuring the negative electrode are constructed based on the number and type of valid operating conditions, including: When the first detection condition is invalid , ; When the second detection condition is invalid , ; When the third detection condition is invalid , ; When the fourth detection condition is invalid , ; Based on the number and type of effective operating conditions, the positive and negative intermediate variables for fitting are constructed as follows: When the first detection condition is invalid , ; When the second detection condition is invalid , ; When the third detection condition is invalid , ; When the fourth detection condition is invalid , ; in, , , , These are the measurement ratios under the first to fourth testing conditions, respectively. , , , These represent the fitting ratios for the first to fourth detection conditions, respectively. c represents the intermediate variable measured at the positive electrode; To measure the intermediate variable at the negative pole; To fit the positive intermediate variable; To fit the negative intermediate variable.

[0071] After constructing the intermediate variable of the positive electrode based on the actual sampling voltage, and measuring the intermediate variable of the negative electrode And the fitting positive intermediate variable constructed based on the pure resistance value derivation of the circuit structure. and fitting negative intermediate variables Subsequently, due to the constructed intermediate measurement variables ( , ) and fitting intermediate variables ( , It adopts a symmetrical mathematical ratio structure. Under the ideal boundary conditions of accurate sampling, when the measurement ratio of each detection condition is equal to the fitting ratio ( = When ), then = , = Based on this equality relationship, the specific measured values ​​are substituted to determine the intermediate measurement variables ( , Based on the equivalent parallel relationship of the first resistance on the positive side, the second resistance on the positive side, the first resistance on the negative side, and the second resistance on the negative side, the initial values ​​of the insulation resistance between the positive and negative poles to ground can be obtained by reverse calculation.

[0072] Specifically, based on the equivalent parallel relationship of the first resistor on the positive side, the second resistor on the positive side, the first resistor on the negative side, and the second resistor on the negative side (with resistance values ​​of R1, R2, R3, and R4 respectively), an analytical algebraic inverse calculation is performed to obtain the initial value of the insulation resistance between the positive terminal and ground. and the initial value of the insulation resistance between the negative electrode and ground .

[0073] The initial value of the insulation resistance between the positive electrode and ground is expressed as: ; The initial value of the insulation resistance between the negative electrode and ground is expressed as: ; in, c is the positive intermediate variable; c is a negative intermediate variable; This is the initial value of the insulation resistance between the positive terminal and ground; This is the initial value of the insulation resistance between the negative electrode and ground; The first resistor on the positive side; R1 is the second resistor on the positive side; R2 is the first resistor on the negative side; R3 is the second resistor on the negative side.

[0074] After obtaining the initial values ​​of the positive-to-ground insulation resistance and the negative-to-ground insulation resistance by back-calculating the positive and negative intermediate variables, the cost model can be iteratively updated starting from the initial values ​​until the final values ​​of the positive-to-ground insulation resistance and the negative-to-ground insulation resistance are output.

[0075] Specifically, the process of iteratively updating the cost model until the convergence condition is met, and then outputting the final values ​​of the positive-to-ground insulation resistance and the negative-to-ground insulation resistance, is as follows: Figure 6 As shown, it includes: Input the current estimated values ​​of the positive-to-ground insulation resistance and the negative-to-ground insulation resistance into the cost model to obtain the current error, and determine the direction of change of the current estimated value and the adjustment step size; Based on the direction of change and the adjustment step size, the current estimate is updated to obtain candidate estimates, and the update error of the candidate estimates under the cost model is obtained. If the update error is less than or equal to the current error, the candidate estimate is accepted as the new current estimate and the iteration continues. The iteration is then checked to see if the new current estimate meets the convergence condition. If it does, the iteration is terminated and the corresponding new current estimate is output as the final value. If it does not meet the condition, the iteration returns to the step of obtaining the current error to continue the iteration. If the update error is greater than the current error, the candidate estimate is rejected, the current estimate before the update is retained as the final value, and the iteration is terminated. The convergence conditions include: the update error is less than or equal to a preset error threshold, and / or the number of iterations reaches a preset maximum number.

[0076] In each iteration, the current estimated values ​​of the positive-to-ground insulation resistance and the negative-to-ground insulation resistance are input (in the first iteration, the initial value of the positive-to-ground insulation resistance is input separately). and the initial value of the insulation resistance between the negative electrode and ground The current error value J is obtained by inputting it into the cost model. Then, by performing first-order linearization on the cost model near the current parameter point, the direction of change of the current estimate and the adjustment step size are determined.

[0077] The direction of change and adjustment step size of the positive electrode-to-ground insulation resistance are expressed as follows: ; The direction of change and adjustment step size of the insulation resistance between the negative electrode and ground are expressed as follows: ; in, ; ; ; ; ; ; After obtaining the step size, the resistance values ​​are updated by superposition to obtain a new set of candidate estimates: , .

[0078] Finally, the candidate estimates , When the data is re-entered into the cost model, the new error caused by this set of candidate estimates is calculated, i.e., the update error J. new .

[0079] If J new If the value is less than or equal to J, it indicates that the current optimization direction is correct. In this case, the update is accepted, and the candidate estimate is used as the new current estimate for the next iteration. It is then determined whether the current estimate meets the convergence condition. If it does, the current estimate is output as the final value. If it does not meet the condition, the error calculation and update process is repeated. This process continues until the iteration meets the convergence condition, and the current estimate obtained in the last step is output as the final result.

[0080] It should be noted that when the update error J is calculated... new If the error is less than the preset error threshold, it means that the result is close to the optimal solution; or, the system stops when the number of forced loop iterations reaches the maximum allowed number, in order to control the system's computing resources.

[0081] If Jnew > J, it means that forcibly updating at this point will cause the model to diverge (at this point, there may be extremely bad situations such as extremely noisy data or serious deviations from the initial value prediction, making it impossible to fit a normal convergence result). Therefore, the system directly rejects the update, stops at the current point, and retains the current estimated value before the update as the final value output, thereby effectively ensuring the safety and stability of the system under abnormal operating conditions.

[0082] After outputting the final values ​​of the positive-to-ground insulation resistance and the negative-to-ground insulation resistance, these values ​​can be compared with preset resistance thresholds. If both the final values ​​of the positive-to-ground and negative-to-ground insulation resistances are greater than the preset resistance thresholds, it indicates that the current DC bus insulation performance to ground is good, the circuit is considered normal, and the system continues to maintain normal operation. Conversely, if either the final value of the positive-to-ground or negative-to-ground insulation resistance is less than or equal to the preset resistance threshold, it indicates that leakage or insulation material deterioration has occurred on the positive or negative side. In this case, insulation impedance failure is determined, and the insulation resistance detection system 10 can further trigger safety protection mechanisms, such as sending an insulation fault alarm message to the main control unit (e.g., BMS or PCS), illuminating a fault indicator light, or directly controlling the high-voltage relay to disconnect the DC bus, thereby ensuring the safe operation of the electrical system.

[0083] The preset resistance threshold is a pre-calibrated critical resistance value based on safety standards or system insulation class requirements (for example, it can be set by multiplying the maximum operating voltage of the system by a specified insulation reference factor).

[0084] like Figure 7 As shown, one embodiment of this application provides an insulation resistance detection device 20, which includes: The working condition construction module 21 is used to adjust the test circuit topology state of the insulation resistance detection system and construct multiple different detection working conditions. The measurement ratio acquisition module 22 is used to acquire the measurement ratio of the DC bus positive terminal to ground voltage to the negative terminal to ground voltage under each detection condition. The fitting ratio acquisition module 23 is used to determine the ratio between the equivalent parallel resistance of the positive electrode to ground and the equivalent parallel resistance of the negative electrode under each detection condition based on a preset resistance measurement model, and to use it as a fitting ratio to characterize the theoretical voltage ratio. The cost model construction module 24 is used to construct a cost model that reflects the overall fitting error based on the measurement ratio and the fitting ratio. The iterative solution module 25 is used to determine the initial values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance based on the measured ratio and the fitted ratio, and to iteratively update the cost model from this starting point until the convergence condition is met, and then output the final values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance.

[0085] Each module in the above-mentioned device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0086] like Figure 8 As shown, one embodiment of the present invention provides an electronic device 700. The electronic device 700 includes a memory 701, a processor 702, and an input / output (I / O) interface 703. The memory 701 is used to store instructions. The processor 702 is used to execute the insulation resistance detection method of the embodiments of this application by calling the instructions stored in the memory 701. The processor 702 is connected to both the memory 701 and the I / O interface 703, for example, via a bus system and / or other forms of connection mechanism (not shown). The memory 701 can be used to store programs and data, including the program for the insulation resistance detection method involved in the embodiments of this application. The processor 702 executes various functional applications and data processing of the electronic device 700 by running the program stored in the memory 701.

[0087] In this embodiment, the processor 702 can be implemented in at least one of the following hardware forms: digital signal processor (DSP), field programmable gate array (FPGA), and programmable logic array (PLA). The processor 702 can be one or a combination of several of the following: central processing unit (CPU) or other processing units with data processing capability and / or instruction execution capability.

[0088] The memory 701 in this embodiment may include one or more computer program products, which may include various forms of computer-readable storage media, such as volatile memory and / or non-volatile memory. Volatile memory may include, for example, random access memory (RAM) and / or cache memory. Non-volatile memory may include, for example, read-only memory (ROM), flash memory, hard disk drive (HDD), or solid state drive (SSD).

[0089] In this embodiment, the I / O interface 703 can be used to receive input instructions (such as numeric or character information, and to generate key signal inputs related to user settings and function control of the electronic device 700), and can also output various information (such as images or sounds) to the outside. In this embodiment, the I / O interface 703 may include one or more of the following: a physical keyboard, function keys (such as volume control keys, power buttons, etc.), a mouse, a joystick, a trackball, a microphone, a speaker, and a touch panel.

[0090] The foregoing description of implementations of this application has been provided for illustrative and descriptive purposes. The foregoing description is not exhaustive and is not intended to limit this application to the exact forms disclosed. Various modifications and variations may exist in accordance with the foregoing teachings, or may arise from practice of this application. These embodiments were chosen and described to illustrate the principles of this application and its practical application, enabling those skilled in the art to utilize this application in various implementations and modifications to suit the specific purpose of the concept.

[0091] Regarding the apparatus in the above embodiments, the specific manner in which each module performs its operation has been described in detail in the embodiments related to the method, and will not be elaborated upon here.

[0092] It can be further understood that, unless otherwise specified, "connection" includes both direct connections where no other components exist between the two parties and indirect connections where other components exist between them.

[0093] It is further understood that although the operations are described in a specific order in the accompanying drawings in the embodiments of this application, this should not be construed as requiring these operations to be performed in the specific order or serial order shown, or requiring all the operations shown to be performed to obtain the desired result. In certain environments, multitasking and parallel processing may be advantageous.

[0094] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the field of this application that are not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0095] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

[0096] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. An insulation resistance detection method, applied to an insulation resistance detection system, wherein the insulation resistance detection system is connected to a DC bus, and the DC bus has a positive-to-ground insulation resistance and a negative-to-ground insulation resistance to be measured, characterized in that: The method includes: Adjust the test circuit topology of the insulation resistance detection system to construct multiple different detection conditions; Under each testing condition, the measured ratio of the positive terminal voltage to ground voltage and the negative terminal voltage to ground voltage of the DC bus is obtained. Based on the preset resistance measurement model, the ratio between the equivalent parallel resistance of the positive electrode to ground and the equivalent parallel resistance of the negative electrode under each detection condition is determined as the fitting ratio characterizing the theoretical voltage ratio. Based on the measurement ratio and the fitting ratio, a cost model reflecting the overall fitting error is constructed. Based on the measured ratio and the fitted ratio, the initial values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance are determined. Starting from these initial values, the cost model is iteratively updated until the convergence condition is met, and then the final values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance are output.

2. The insulation resistance detection method as described in claim 1, characterized in that, The insulation resistance detection system includes a first detection circuit connected between the positive terminal of the DC bus and the reference potential terminal, and a second detection circuit connected between the negative terminal of the DC bus and the reference potential terminal. The first detection circuit includes a first resistor on the positive side, a second resistor on the positive side, and a first switch connected in parallel to the second resistor on the positive side; The second detection circuit includes a first resistor on the negative side, a second resistor on the negative side connected in series, and a second switch connected in parallel with the second resistor on the negative side; Adjusting the test circuit topology of the insulation resistance testing system to construct multiple different testing conditions includes: The on / off states of the first switch and the second switch are controlled to construct multiple different detection conditions.

3. The insulation resistance detection method as described in claim 2, characterized in that, Controlling the on / off states of the first and second switches to construct multiple detection conditions includes: According to a predetermined sequence, the on / off combination of the first switch and the second switch is changed sequentially to construct the first detection condition, the second detection condition, the third detection condition and the fourth detection condition; The first detection condition is defined as: the first switch is open, and the second switch is open. The second detection condition is defined as follows: the first switch is on, and the second switch is off; The third detection condition is defined as follows: the first switch is open, and the second switch is on. The fourth detection condition is defined as follows: the first switch is on, and the second switch is on.

4. The insulation resistance detection method as described in claim 3, characterized in that, After acquiring the DC bus positive-to-ground voltage and negative-to-ground voltage under each testing condition, the following data is obtained: The DC bus positive-to-ground voltage and negative-to-ground voltage under each detection condition are compared with the preset minimum effective threshold. If either the positive electrode voltage to ground or the negative electrode voltage to ground is less than a preset minimum effective threshold, the corresponding detection condition is determined to be an invalid condition, and after removing the invalid condition, the remaining valid conditions are extracted.

5. The insulation resistance detection method as described in claim 4, characterized in that: If the number of valid operating conditions is less than three, an insulation resistance failure is determined, and the detection process is terminated.

6. The insulation resistance detection method as described in claim 5, characterized in that, Based on a pre-defined resistance measurement model, the ratio between the equivalent parallel resistance of the positive electrode to ground and the equivalent parallel resistance of the negative electrode under each detection condition is determined as a fitting ratio characterizing the theoretical voltage ratio, including: Based on the conduction or disconnection of the first switch and the second switch under the corresponding detection conditions, the first equivalent access resistance of the first detection circuit and the second equivalent access resistance of the second detection circuit are determined. The ratio of the parallel resistance of the positive electrode to ground insulation resistance and the first equivalent connection resistance to the parallel resistance of the negative electrode to ground insulation resistance and the second equivalent connection resistance to the ground is used as the fitting ratio for the corresponding detection condition.

7. The insulation resistance detection method as described in claim 6, characterized in that, Based on the measured ratio and the fitted ratio, the initial values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance are determined, including: Determine the number and type of the extracted valid working conditions; Based on the number and type of effective working conditions, the intermediate variables for measuring the positive electrode, measuring the negative electrode, fitting the positive electrode intermediate variable, and fitting the negative electrode intermediate variable are constructed respectively. Based on the measurement ratio under the corresponding effective working conditions, determine the intermediate variable of the positive electrode and the intermediate variable of the negative electrode. Under the condition that the measured ratio is equal to the fitted ratio, the initial values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance are determined based on the resistance measurement model.

8. The insulation resistance detection method as described in claim 7, characterized in that: When the number of effective operating conditions is four, based on the number and type of effective operating conditions, the intermediate variable for measuring the positive electrode is constructed as follows: ； The intermediate variable for measuring the negative electrode is constructed as follows: ； The fitted positive intermediate variable is constructed as follows: ； The fitted negative intermediate variable is constructed as follows: = ； in, , , , These are the measurement ratios under the first to fourth testing conditions, respectively. , , , These represent the fitting ratios for the first to fourth detection conditions, respectively. c represents the intermediate variable measured at the positive electrode; To measure the intermediate variable at the negative pole; To fit the positive intermediate variable; To fit the negative intermediate variable; This is the initial value of the insulation resistance between the positive terminal and ground; This is the initial value of the insulation resistance between the negative electrode and ground; R1 is the first resistor on the positive side; R2 is the second resistor on the positive side. R1 is the first resistor on the negative side; R4 is the second resistor on the negative side. This indicates the operation of resistors in parallel.

9. The insulation resistance detection method as described in claim 7, characterized in that: When the number of effective operating conditions is three, the intermediate variables for measuring the positive electrode and the intermediate variables for measuring the negative electrode are constructed based on the number and type of effective operating conditions, including: When the first detection condition is invalid , ; When the second detection condition is invalid , ; When the third detection condition is invalid , ; When the fourth detection condition is invalid , ; Based on the number and type of effective operating conditions, the positive and negative intermediate variables for fitting are constructed as follows: When the first detection condition is invalid , ; When the second detection condition is invalid , ; When the third detection condition is invalid , ; When the fourth detection condition is invalid , ; in, , , , These are the measurement ratios under the first to fourth testing conditions, respectively. , , , These represent the fitting ratios for the first to fourth detection conditions, respectively. c represents the intermediate variable measured at the positive electrode; To measure the intermediate variable at the negative pole; To fit the positive intermediate variable; To fit the negative intermediate variable.

10. The insulation resistance testing method according to any one of claims 1-9, characterized in that, Before constructing a cost model reflecting the overall fitting error based on the measurement ratio and the fitting ratio, the method further includes: Extract the smaller value between the positive electrode voltage to ground and the negative electrode voltage to ground under the corresponding detection condition, and determine the weight of the corresponding detection condition based on the square of the smaller value, expressed as follows: ； in, For the first The weight corresponding to each detection condition For the first The positive terminal to ground voltage of the DC bus under the test conditions. For the first The negative terminal to ground voltage of the DC bus under the test conditions.

11. The insulation resistance detection method as described in claim 10, characterized in that, Based on the measurement ratio and the fitting ratio, a cost model reflecting the overall fitting error is constructed as follows: ； in, For the first The weight corresponding to each detection condition For the first The fitting ratio under each detection condition For the first The measurement ratio under each testing condition.

12. The insulation resistance detection method as described in claim 11, characterized in that, The cost model is iteratively updated until the convergence condition is met, and the final values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance are output, including: The current estimated values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance are input into the cost model to obtain the current error, and the direction of change and adjustment step size of the current estimated value are determined. Based on the direction of change and the adjustment step size, the current estimated value is updated to obtain a candidate estimated value, and the update error of the candidate estimated value under the cost model is obtained; If the update error is less than or equal to the current error, the candidate estimate is accepted as the new current estimate and the iteration continues. It is then determined whether the new current estimate satisfies the convergence condition. If it does, the iteration is terminated and the corresponding new current estimate is output as the final value. If it does not, the iteration returns to the step of obtaining the current error to continue the iteration. If the update error is greater than the current error, then the candidate estimate is rejected, the current estimate before the update is retained as the final value, and the iteration is terminated. The convergence conditions include: the update error is less than or equal to a preset error threshold, and / or the number of iterations reaches a preset maximum number.

13. The insulation resistance detection method as described in claim 12, characterized in that, Determining the direction of change and adjustment step size of the current estimate includes: By performing first-order linearization on the cost model near the parameter point corresponding to the current estimate, and based on the weighted least squares criterion, the change direction and adjustment step size of the positive electrode to ground insulation resistance and the change direction and adjustment step size of the negative electrode to ground insulation resistance are calculated respectively. The direction of change and adjustment step size of the positive electrode's insulation resistance to ground are expressed as follows: ； The direction of change and adjustment step size of the insulation resistance between the negative electrode and ground are expressed as follows: ； in, ; ; ; ； ； 。 14. An insulation resistance testing device, applied to an insulation resistance testing system, wherein the insulation resistance testing system is connected to a DC bus, and the DC bus has a positive-to-ground insulation resistance and a negative-to-ground insulation resistance to be measured, characterized in that, The device includes: The working condition construction module is used to adjust the test circuit topology of the insulation resistance detection system and construct multiple different detection working conditions. The measurement ratio acquisition module is used to acquire the measurement ratio of the positive terminal voltage to ground and the negative terminal voltage to ground of the DC bus under various detection conditions. The fitting ratio acquisition module is used to determine the ratio between the equivalent parallel resistance of the positive electrode to ground and the equivalent parallel resistance of the negative electrode under each detection condition based on a preset resistance measurement model, and to use it as a fitting ratio characterizing the theoretical voltage ratio. The cost model construction module is used to construct a cost model that reflects the overall fitting error based on the measurement ratio and the fitting ratio. The iterative solution module is used to determine the initial values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance based on the measured ratio and the fitted ratio, and to iteratively update the cost model from these initial values ​​until the convergence condition is met, and then output the final values ​​of the positive electrode-to-ground insulation resistance and the negative electrode-to-ground insulation resistance.

15. An electronic device, characterized in that, include: The device includes an input unit, a memory, at least one processor, and an output interface, wherein the memory stores program instructions that can be executed on the processor, and the processor can execute the insulation resistance detection method as described in any one of claims 1 to 13 by calling the program instructions.

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