Electric vehicle insulation fault positioning method based on parallel insulation resistor detection

Abstract

The invention belongs to the technical field of new energy automobile insulation detection, and particularly relates to an electric automobile insulation fault positioning method based on parallel insulation resistance detection, which comprises the following steps: establishing an intermediate fault basic model of a battery system, and defining circuit parameters and fault positions; enabling the intermediate fault resistance of the battery system in the intermediate fault basic model to be equivalent to the insulation resistance of the total positive electrode and the total negative electrode to the ground, and obtaining a converted insulation fault equivalent circuit; calculating the total insulation resistance based on the equivalent relationship between the total positive insulation resistance to ground and the total negative insulation resistance to ground in the equivalent circuit, and determining the parallel resistance value of the total positive insulation resistance to ground and the total negative insulation resistance to ground; by measuring the total voltage of the battery system and the average voltage of the current battery pack and combining the parallel resistance value, the insulation fault position is calculated and positioned. According to the invention, the accurate calculation of the total insulation resistance and the accurate positioning of the insulation fault position are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of insulation detection of new energy vehicles, and in particular, relates to an insulation fault locating method for electric vehicles based on parallel insulation resistance detection. Background Art

[0002] With the rapid development of new energy vehicles, the safety of electric vehicles has received increasing attention. Among them, the insulation performance of the on-board high-voltage system is one of the key technologies to ensure the safety of vehicle operation. According to the current national standard "GB / T18384.1-2015 Electric Vehicle Safety Requirements", the vehicle insulation resistance test is to test the insulation resistance between the positive and negative electrodes of the on-board rechargeable energy storage system (REESS) and the vehicle body ground. The test results are required to meet the requirement that the insulation resistance error rate does not exceed 10% to ensure the safety of vehicle driving.

[0003] The current insulation detection method usually uses the insulation resistance values ​​of the total positive and negative of the battery system to the vehicle body ground (i.e., Rp and Rn) to measure, and takes the minimum value of the two as the insulation resistance value of the whole vehicle. However, the battery system is usually composed of multiple battery boxes connected in series and parallel. When the insulation fault occurs in the middle position of the battery system, the existing insulation resistance detection method ignores the equivalent insulation resistance characteristics of the middle position, and the detection result is biased, with an error rate of up to 30% to 50%. This detection error causes the battery management system (BMS) to miss or misreport insulation faults, thereby affecting maintenance efficiency and even endangering vehicle driving safety.

[0004] In addition, the existing insulation detection method can only detect the total resistance of the insulation fault, but cannot accurately locate the location of the fault. When the BMS reports an insulation fault, the driver or maintenance personnel need to manually locate the fault point, which is not only time-consuming and labor-intensive, but also misses the best rescue opportunity, resulting in serious property losses.

[0005] Therefore, the existing technology has significant deficiencies in accurately detecting the insulation resistance of the battery system and locating the fault point. There is an urgent need for a new insulation detection and fault location technology that can not only improve the insulation detection accuracy, but also quickly and accurately locate the insulation fault point. Summary of the invention

[0006] In view of the defects of the prior art, the present invention proposes an electric vehicle insulation fault locating method based on parallel insulation resistance detection. The method can improve the insulation detection accuracy of the electric vehicle battery management system (BMS) and realize the rapid positioning of the insulation fault point. The method optimizes the fault point positioning mechanism through an innovative insulation resistance detection method, and solves the problems of large errors and poor fault positioning ability of the existing detection methods without increasing the complexity of the hardware.

[0007] The present invention provides an electric vehicle insulation fault location method based on parallel insulation resistance detection, the method comprising:

[0008] Step 1: Establish a basic model of intermediate faults in the battery system and define circuit parameters and fault locations;

[0009] Step 2: Equivalent the intermediate fault resistance of the battery system in the intermediate fault basic model to the insulation resistance of the total positive electrode and the total negative electrode to the ground, to obtain a converted insulation fault equivalent circuit;

[0010] Step 3: Based on the equivalent relationship between the total positive electrode insulation resistance to ground and the total negative electrode insulation resistance to ground in the equivalent circuit, calculate the total insulation resistance, and determine the parallel resistance value of the total positive electrode insulation resistance to ground and the total negative electrode insulation resistance to ground;

[0011] Step 4: By measuring the total voltage of the battery system and the average voltage of the current battery pack, combined with the parallel resistance value, the insulation fault position is calculated and located.

[0012] Further, step 1 comprises:

[0013] Step 1.1: define an initial circuit, wherein the initial circuit includes a total voltage of the battery system, fault points distributed at different positions of the total voltage of the battery system, insulation resistances of the upper branch and the lower branch, insulation resistance of the middle fault point, and a switch for controlling the circuit state;

[0014] Step 1.2: Based on the initial circuit defined in step 1.1, determine the proportional position where the fault occurs in the system;

[0015] Step 1.3: According to the initial circuit defined in step 1.1, determine the voltage distribution from the intermediate fault point to the total positive electrode and the total negative electrode of the battery system.

[0016] Furthermore, in step 1.2, the relative position parameter of the insulation fault in the battery system is represented by Y, and the value range of Y is 0≤Y≤1, specifically including:

[0017] When Y = 0, it means that the insulation fault occurs at the total negative pole position of the battery system;

[0018] When Y=1, it means that the insulation fault occurs at the total positive electrode position of the battery system;

[0019] When 0<Y<1, it indicates that the insulation fault occurs in the middle position between the total negative electrode and the total positive electrode of the battery system.

[0020] Furthermore, step 2 includes:

[0021] Step 2.1: construct an insulation fault equivalent circuit, wherein the equivalent circuit includes the total voltage of the battery system, the insulation resistance of the total positive electrode, the insulation resistance of the total negative electrode, the insulation resistance of the upper branch, the insulation resistance of the lower branch, and a switch for controlling the circuit state;

[0022] Step 2.2: Based on the insulation fault equivalent circuit, determine the voltages of the upper branch and the lower branch;

[0023] Step 2.3: Convert the fault resistance at the middle position into positive insulation resistance and negative insulation resistance.

[0024] Furthermore, in step 2.3, the equivalent insulation resistance R p Determined by the following formula:

[0025]

[0026] Equivalent insulation resistance R of negative pole to ground n Determined by the following formula:

[0027]

[0028] Where: X represents the equivalent insulation resistance at the location where the insulation fault occurs in the battery system; Y represents the relative position parameter of the insulation fault in the battery system; 1-Y represents the ratio of the voltage from the intermediate fault point to the total negative electrode of the battery system to the total system voltage.

[0029] Further, step 3 includes:

[0030] Step 3.1: Determine the total insulation resistance using the parallel resistance formula using the equivalent insulation resistance of the positive and negative sides;

[0031] Step 3.2: Consider the insulation resistance of the total positive electrode and the total negative electrode as a parallel relationship, and calculate the equivalent parallel resistance between the total positive electrode and the total negative electrode.

[0032] Further, in step 3.1, the total insulation resistance is determined by the following formula:

[0033]

[0034] Where: R p Indicates the equivalent insulation resistance of the positive electrode to the ground; R n Indicates the equivalent insulation resistance of the negative pole to ground.

[0035] Furthermore, in step 3.2, the equivalent parallel resistance is determined by the following formula:

[0036]

[0037] Where: R pIndicates the equivalent insulation resistance of the positive electrode to the ground; R n Indicates the equivalent insulation resistance of the negative pole to ground.

[0038] Further, step 4 includes:

[0039] Step 4.1: Measure the battery system through the insulation monitoring device to obtain the fault leakage voltage, and obtain the average voltage of the current battery cell through the battery management system;

[0040] Step 4.2: Determine the location of the fault point in the battery system based on the ratio of the fault leakage voltage to the average voltage of the battery cell.

[0041] Furthermore, in step 4.2, the insulation fault location is determined by the following formula:

[0042]

[0043] The beneficial effects of the present invention are:

[0044] First, the electric vehicle insulation fault location method based on parallel insulation resistance detection provided by the present invention achieves accurate calculation of the total insulation resistance and precise location of the insulation fault position by equating the intermediate fault resistance of the battery system to the insulation resistance of the total positive and negative electrodes to the ground, and combining the parallel resistance relationship and voltage measurement. This method can effectively solve the problems of large insulation resistance detection errors and difficult fault location in the prior art, improve the accuracy and reliability of electric vehicle insulation fault detection, and ensure the safety and stability of the system.

[0045] Second, in the preferred implementation, the present invention can systematically define and analyze the initial circuit state of the battery system through steps 1.1 to 1.3, and accurately locate the proportional position and voltage distribution of the fault. This method helps to clarify the voltage relationship between the fault point and the positive and negative electrodes of the battery system, thereby providing accurate data support for insulation resistance detection. By accurately analyzing the circuit structure and voltage distribution, the problem of inaccurate fault location and voltage detection in the prior art is effectively solved, measurement errors are reduced, and the accuracy and reliability of insulation resistance detection are improved. It is particularly suitable for insulation fault diagnosis of intermediate nodes of battery systems;

[0046] Third, in a preferred implementation, step 1.2 of the present invention introduces parameter Y (0≤Y≤1) to represent the relative position of the insulation fault in the battery system, which can accurately reflect the distribution of the fault point between the total negative electrode and the total positive electrode: when Y=0, the fault is located at the total negative electrode; when Y=1, the fault is located at the total positive electrode; and when 0<Y<1, the fault is located in the middle between the two. This parameterized description effectively solves the problem that the traditional method cannot accurately locate the insulation fault position;

[0047] Fourth, in the preferred implementation, the present invention converts the complex battery system fault resistance into positive electrode insulation resistance and negative electrode insulation resistance based on the insulation fault equivalent circuit through the implementation of step 2, and accurately calculates the equivalent insulation resistance values ​​of the positive and negative electrodes in combination with the voltage ratio parameter. This method can accurately locate the fault location, simplify the calculation process of insulation resistance detection, and effectively reduce the detection error;

[0048] Fifth, in a preferred implementation, the present invention, through the implementation of step 3, regards the equivalent insulation resistance of the positive electrode side and the negative electrode side as a parallel relationship, calculates the total insulation resistance using the parallel resistance formula, and further optimizes the calculation process of the equivalent parallel resistance. This method can accurately decompose and simplify the insulation resistance of a complex battery system into a calculable form, effectively improving the accuracy and efficiency of insulation resistance detection. In addition, through the mathematical formula R 总 The calculation ensures accurate evaluation of insulation fault location and resistance value;

[0049] Sixth, in the preferred implementation, the present invention implements step 4, uses the insulation monitoring device to measure the battery system, obtains the fault leakage voltage, and calculates the ratio in combination with the average voltage of the battery cell, so as to accurately locate the location where the fault occurs. This method improves the accuracy of fault diagnosis, helps to quickly identify the insulation fault point in the battery system, thereby shortening the troubleshooting time and improving the detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a flow chart of the electric vehicle insulation fault location method based on parallel insulation resistance detection of the present invention;

[0051] Figure 2 It is a schematic diagram of a simultaneous equivalent conversion of an equivalent circuit of a battery system midpoint insulation fault and an equivalent circuit of a battery system total positive and total negative insulation fault in an embodiment of the present invention;

[0052] Figure 3 is a commercial vehicle real vehicle test scene diagram of an embodiment of the present invention;

[0053] Figure 4 is a schematic diagram of an artificially triggered insulation fault according to an embodiment of the present invention;

[0054] Figure 5 Graph showing the insulation resistance of the total positive electrode and the total negative electrode of the embodiment of the present invention. DETAILED DESCRIPTION

[0055] In order to enable those skilled in the art to better understand the technical solution of the present application, the present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0056] In the description of this application, the terms "first", "second", and "third" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance; the term "plurality" refers to two or more, unless otherwise expressly defined. Terms such as "installed", "connected", "connected", and "fixed" should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0057] In the description of the present application, it should be understood that the directions or positional relationships indicated by the terms "up", "down", "left", "right", "front", "back", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation, and therefore, should not be understood as a limitation on the present application.

[0058] In the description of this specification, the description of the terms "one embodiment / method", "some embodiments / methods", "specific embodiments / methods", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments / methods or examples in a suitable manner.

[0059] As the instruction manual Figure 1 The present invention proposes an electric vehicle insulation fault location method based on parallel insulation resistance detection, comprising:

[0060] Step 1: Establish a basic model of intermediate faults in the battery system and define circuit parameters and fault locations.

[0061] The purpose of step 1 is to establish a basic model of intermediate faults in the battery system, define fault parameters and fault locations, clarify the location of the fault and the relationship between various circuit parameters, and analyze the impact of the fault on the system voltage distribution and insulation resistance. This provides a theoretical basis for the subsequent conversion of the intermediate fault resistance into the insulation resistance of the total positive and negative electrodes of the system.

[0062] Step 1 includes:

[0063] Step 1.1: Define an initial circuit, which includes the total voltage of the battery system, fault points distributed at different positions of the total voltage of the battery system, insulation resistance of the upper branch and the lower branch, insulation resistance of the middle fault point, and a switch for controlling the circuit state.

[0064] Step 1.2: Based on the initial circuit defined in step 1.1, determine the proportional location where the fault occurs in the system.

[0065] Step 1.3: Based on the initial circuit defined in step 1.1, determine the voltage distribution from the intermediate fault point to the total positive and total negative electrodes of the battery system.

[0066] As the instruction manual Figure 2 , Figure 2 The process of how to perform a simultaneous equivalent conversion between the equivalent circuit of the battery system midpoint insulation fault and the equivalent circuit of the battery system total positive and total negative insulation fault is demonstrated. Figure 2 (a) is the original circuit model of the intermediate fault point, including the influence of the intermediate fault resistance X and its position Y on the overall voltage distribution, where K1 and K2 represent switches, which are used to control the circuit closure of the upper branch (positive side) and the lower branch (negative side) respectively. U1 and U2 represent the voltage of the upper branch and the lower branch respectively. R1 and R2 represent the insulation resistance of the upper branch and the lower branch respectively. X represents the equivalent insulation resistance of the location where the insulation fault occurs in the battery system.

[0067] Y represents the relative position parameter of the insulation fault in the battery system, ranging from 0≤Y≤1. When Y=0, it means that the fault occurs at the total negative pole position of the battery system (close to the lowest voltage point), when Y=1, it means that the fault occurs at the total positive pole position of the battery system (close to the highest voltage point), and 0<Y<1 means that the fault occurs in the middle of the total negative pole and the total positive pole of the battery system. s Indicates the total voltage of the battery system. (1-Y)U s Indicates the voltage distribution from the intermediate point fault to the negative pole. s Represents the voltage distribution from the intermediate point fault to the positive pole.

[0068] Based on the basic model of the intermediate fault of the battery system, only the switch K1 is closed to obtain the voltage relationship of the upper branch of the basic model:

[0069]

[0070] Based on the basic model of the intermediate fault of the battery system, only the switch K2 is closed, and the voltage relationship of the lower branch of the basic model is obtained:

[0071]

[0072] Step 2: The intermediate fault resistance of the battery system in the intermediate fault basic model is equivalent to the insulation resistance of the total positive electrode and the total negative electrode to the ground, and the converted insulation fault equivalent circuit is obtained.

[0073] The purpose of step 2 is to convert the circuit model of the intermediate fault of the battery system in step 1 into the equivalent insulation resistance X between the total positive and negative electrodes of the battery system and the ground through mathematical methods and equivalent conversion. p and R n , in order to simplify the circuit structure and facilitate subsequent calculations and fault analysis.

[0074] Step 2 includes:

[0075] Step 2.1: Construct an insulation fault equivalent circuit, which includes the total voltage of the battery system, the insulation resistance of the total positive electrode, the insulation resistance of the total negative electrode, the insulation resistance of the upper branch, the insulation resistance of the lower branch, and the switch that controls the circuit state.

[0076] As the instruction manual Figure 2 , Figure 2 (b) is the equivalent conversion circuit of (a), which converts the intermediate fault effect into the insulation resistance R of the total positive and negative electrodes. p and R n , where R p Indicates the insulation resistance between the total positive electrode of the battery system and the vehicle body ground, R n Indicates the insulation resistance between the total negative electrode of the battery system and the vehicle body ground. The insulation resistances R1 and R2 of the upper and lower branches remain unchanged. The total voltage of the battery system is U s .

[0077] Step 2.2: Based on the insulation fault equivalent circuit, determine the voltages of the upper and lower branches.

[0078] Only switch K1 is closed, and the voltage relationship of the upper branch of the insulation fault equivalent circuit is obtained:

[0079]

[0080] Only switch K2 is closed, and the voltage relationship of the lower branch of the insulation fault equivalent circuit is obtained:

[0081]

[0082] Step 2.3: Convert the fault resistance at the middle position into positive insulation resistance and negative insulation resistance.

[0083] By simplifying formulas (1)-(4), the equivalent insulation resistance R of the positive electrode to ground is p Determined by the following formula:

[0084]

[0085] Equivalent insulation resistance R of negative pole to ground n Determined by the following formula:

[0086]

[0087] In equations (5) and (6), X represents the equivalent insulation resistance of the location where the insulation fault occurs in the battery system; Y represents the relative position parameter of the insulation fault in the battery system; 1-Y represents the voltage from the intermediate fault point to the total negative electrode of the battery system as a percentage of the total system voltage U s ratio (i.e. positional relationship).

[0088] Step 3: Based on the equivalent relationship between the total positive electrode-to-ground insulation resistance and the total negative electrode-to-ground insulation resistance in the equivalent circuit, calculate the total insulation resistance, and determine the parallel resistance value of the total positive electrode-to-ground insulation resistance and the total negative electrode-to-ground insulation resistance.

[0089] The purpose of step 3 is to determine the total insulation resistance of the battery system through the equivalent insulation resistance relationship between the total positive electrode and the total negative electrode to ground, and express it as the parallel value of the two insulation resistances. This provides a mathematical model and calculation basis for the accurate evaluation of the insulation performance of the battery system.

[0090] Step 3 includes:

[0091] Step 3.1: Equivalent insulation resistance R on the positive and negative sides p and R n , use the parallel resistance formula to determine the total insulation resistance X:

[0092]

[0093] It should be noted that the total insulation resistance X represents the actual resistance of the fault point.

[0094] Step 3.2: Calculate the insulation resistance R of the total positive and total negative electrodes. p and R n Consider it as a parallel relationship and calculate the equivalent parallel resistance R between the total positive electrode and the total negative electrode 总 .

[0095]

[0096] Step 4: By measuring the total voltage of the battery system and the average voltage of the current battery pack, combined with the parallel resistance value, the insulation fault position is calculated and located.

[0097] The purpose of step 4 is to accurately calculate the location Y of the insulation fault point by measuring the total voltage of the battery system, the fault leakage voltage and the average voltage of the battery unit. This step provides a practical means for quickly locating the fault point and improving the efficiency of fault repair.

[0098] Step 4 includes:

[0099] Step 4.1: Measure the battery system through the insulation monitoring device to obtain the fault leakage voltage, and obtain the average voltage of the current battery cell through the battery management system (BMS).

[0100] Step 4.2: Determine the location of the fault point in the battery system based on the ratio of the fault leakage voltage to the average voltage of the battery cell:

[0101] The insulation fault location is calculated by the following formula:

[0102]

[0103] Example

[0104] The beneficial effects of the present invention are illustrated by comparing the insulation resistance detection method of the prior art with the insulation resistance detection method of the present invention.

[0105] The insulation detection method of the prior art is: the insulation resistance should be measured at the most appropriate stage and at an appropriate frequency to obtain the minimum value of the insulation resistance. If the insulation circuit is not integrated in the REESS (Rechargeable Energy Storage System is used in electric vehicles and hybrid vehicles, referring to the battery pack or energy storage device that stores electrical energy), open the key switch and measure the insulation resistance directly; if the insulation circuit is integrated in the REESS, measure the insulation resistance of the switch-closed circuit. When measuring the insulation resistance of the REESS, measure the resistance between the two terminals and the electrical platform:

[0106] The higher value is defined as U1, the lower value is defined as U2, and the two insulation resistances are defined as R1 and R2 respectively, where R2 = Ri (ie, the smaller value of the insulation resistance). Therefore, R2 is finally determined as the insulation resistance Ri of the REESS.

[0107] As the instruction manual Figure 3-4 , using the insulation detection method of the existing technology, when the insulation fault point of the battery system occurs in the middle position between the non-total positive and non-total negative, a battery system consisting of 4 battery boxes in series on a commercial vehicle of a well-known automobile company was tested. Resistances of different sizes were artificially short-circuited between the total positive of the No. 2 battery box and the vehicle body to artificially trigger the insulation fault. Through on-site real vehicle testing, it was found that the insulation resistance value detected by the insulation detection method of the existing technology was not equal to the actual insulation resistance value, that is, Rtotal ≠ Min (Rp, Rn), and there was an error of 30% to 50% between the detected value and the actual value.

[0108] Short-circuit different resistance values to trigger the BMS to report an insulation fault. Through the short-circuit test in the actual scenario, the insulation resistance detection results of the insulation detection method of the prior art are obtained, as shown in Table 1:

[0109] Table 1

[0110]

[0111] As can be seen from Table 1, the error rate in the table is between 30.6% and 50%, indicating that there is a large deviation between the insulation resistance value measured by the insulation detection method of the prior art and the short-circuit resistance value actually set.

[0112] Further, according to formulas (5) and (6), the insulation resistance R Figure 5 of the total positive electrode and the total negative electrode shown in the attached drawings of the specification is generated. The existing insulation detection method uses the "take the minimum value" principle to measure the insulation resistance R p and R n , but there are obvious errors in actual applications. The specific situation is as follows: p and R n , but there are obvious errors in actual applications. The specific situation is as follows:

[0113] When Y = 0, R p = X, R n = ∞, and the insulation resistance is correctly measured as X with an error of zero.

[0114] When Y = 1, R p = ∞, R n = X, and the insulation resistance is still correctly measured as X with an error of zero.

[0115] However, when 0 < Y < 1, taking the smaller value according to the existing insulation detection method, the insulation resistance is not equal to the actual value X, and the error is larger when approaching Y = 0.5.

[0116] When Y = 0.5, R p = 2X, R n = 2X, and the measured value of the insulation resistance is 2X, with an error reaching X, that is, 100% of the actual value.

[0117] Therefore, according to the existing insulation detection method (i.e., the insulation resistance adopts the principle of taking the smaller of the two), although the insulation resistance of the total positive and total negative of the battery can be accurately tested, it is not applicable to the insulation resistance detection of the middle point of the battery system.

[0118] According to the same test environment, using the insulation resistance detection of the present application, the equivalent circuit of the insulation fault at the middle point of the battery system and the equivalent circuit of the insulation fault of the total positive and total negative of the battery system are联立等效转换, and the insulation resistance detection results obtained are shown in Table 2:

[0119] Table 2

[0120]

[0121] It can be seen from Table 2 that the insulation resistance detection method of the present application has a measured value that is closer to the actual short-circuit resistance value, with a slight negative error, and the error rate is between -3.0% and -8.8%. Compared with the existing insulation resistance detection method, the error is significantly reduced and the detection accuracy is higher.

[0122] The present invention converts the intermediate fault resistance of the battery system into the insulation resistance of the positive and negative electrodes to the ground, combines the parallel resistance relationship with the voltage ratio parameter, introduces the fault location parameter Y to accurately describe the fault distribution, and uses the insulation monitoring device to obtain the leakage voltage and the average voltage of the battery cell for ratio calculation, thereby achieving accurate positioning of the fault position and accurate calculation of the total insulation resistance, thereby effectively solving the problems of large detection errors and inaccurate fault positioning in the prior art, and improving the accuracy, efficiency and reliability of insulation fault diagnosis of the electric vehicle battery system.

[0123] The above is only an embodiment of the present invention, and the common sense such as the known specific structure and characteristics in the scheme is not described in detail here. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the attached claims rather than the above description, so it is intended to include all changes within the meaning and scope of the equivalent elements of the claims. Any figure mark in the claims should not be regarded as limiting the claims involved.

Claims

1. A method for locating insulation faults in electric vehicles based on parallel insulation resistance detection, characterized in that: Methods include: Step 1: Establish a basic model of intermediate faults in the battery system and define circuit parameters and fault locations; Step 2: Equivalent the intermediate fault resistance of the battery system in the intermediate fault basic model to the insulation resistance of the total positive electrode and the total negative electrode to the ground, to obtain a converted insulation fault equivalent circuit; Step 3: Based on the equivalent relationship between the total positive electrode insulation resistance to ground and the total negative electrode insulation resistance to ground in the equivalent circuit, calculate the total insulation resistance, and determine the parallel resistance value of the total positive electrode insulation resistance to ground and the total negative electrode insulation resistance to ground; Step 4: By measuring the total voltage of the battery system and the average voltage of the current battery pack, combined with the parallel resistance value, the insulation fault position is calculated and located.

2. The electric vehicle insulation fault location method based on parallel insulation resistance detection according to claim 1 is characterized in that: Step 1 includes: Step 1.1: define an initial circuit, wherein the initial circuit includes a total voltage of the battery system, fault points distributed at different positions of the total voltage of the battery system, insulation resistances of the upper branch and the lower branch, insulation resistance of the middle fault point, and a switch for controlling the circuit state; Step 1.2: Based on the initial circuit defined in step 1.1, determine the proportional position where the fault occurs in the system; Step 1.3: According to the initial circuit defined in step 1.1, determine the voltage distribution from the intermediate fault point to the total positive electrode and the total negative electrode of the battery system.

3. The electric vehicle insulation fault location method based on parallel insulation resistance detection according to claim 2 is characterized in that: In step 1.2, the relative position parameter of the insulation fault in the battery system is represented by Y, and the value range of Y is 0≤Y≤1, specifically including: When Y = 0, it means that the insulation fault occurs at the total negative pole position of the battery system; When Y=1, it means that the insulation fault occurs at the total positive electrode position of the battery system; When 0<Y<1, it indicates that the insulation fault occurs in the middle position between the total negative electrode and the total positive electrode of the battery system.

4. The electric vehicle insulation fault location method based on parallel insulation resistance detection according to claim 1 is characterized in that: Step 2 includes: Step 2.1: construct an insulation fault equivalent circuit, wherein the equivalent circuit includes the total voltage of the battery system, the insulation resistance of the total positive electrode, the insulation resistance of the total negative electrode, the insulation resistance of the upper branch, the insulation resistance of the lower branch, and a switch for controlling the circuit state; Step 2.2: Based on the insulation fault equivalent circuit, determine the voltages of the upper branch and the lower branch; Step 2.3: Convert the fault resistance at the middle position into positive insulation resistance and negative insulation resistance.

5. The electric vehicle insulation fault location method based on parallel insulation resistance detection according to claim 4 is characterized in that: In step 2.3, the equivalent insulation resistance R between the positive electrode and the ground p Determined by the following formula: Equivalent insulation resistance R of negative pole to ground n Determined by the following formula: Where: X represents the equivalent insulation resistance at the location where the insulation fault occurs in the battery system; Y represents the relative position parameter of the insulation fault in the battery system; 1-Y represents the ratio of the voltage from the intermediate fault point to the total negative electrode of the battery system to the total system voltage.

6. The electric vehicle insulation fault location method based on parallel insulation resistance detection according to claim 4 is characterized in that: Step 3 includes: Step 3.1: Determine the total insulation resistance using the parallel resistance formula using the equivalent insulation resistance of the positive and negative sides; Step 3.2: Consider the insulation resistance of the total positive electrode and the total negative electrode as a parallel relationship, and calculate the equivalent parallel resistance between the total positive electrode and the total negative electrode.

7. The electric vehicle insulation fault location method based on parallel insulation resistance detection according to claim 6 is characterized in that: In step 3.1, the total insulation resistance is determined by the following formula: Where: R p Indicates the equivalent insulation resistance of the positive electrode to the ground; R n Indicates the equivalent insulation resistance of the negative pole to ground.

8. The electric vehicle insulation fault location method based on parallel insulation resistance detection according to claim 6 is characterized in that: In step 3.2, the equivalent parallel resistance is determined by the following formula: Where: R p Indicates the equivalent insulation resistance of the positive electrode to the ground; R n Indicates the equivalent insulation resistance of the negative pole to ground.

9. The electric vehicle insulation fault location method based on parallel insulation resistance detection according to claim 1 is characterized in that: Step 4 includes: Step 4.1: Measure the battery system through the insulation monitoring device to obtain the fault leakage voltage, and obtain the average voltage of the current battery cell through the battery management system; Step 4.2: Determine the location of the fault point in the battery system based on the ratio of the fault leakage voltage to the average voltage of the battery cell.

10. The electric vehicle insulation fault location method based on parallel insulation resistance detection according to claim 9, characterized in that: In step 4.2, the insulation fault location is determined by the following formula:

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