An insulation resistance monitoring system and method for an electric vehicle

Abstract

The application provides an insulation resistance monitoring system and method for an electric vehicle, which comprises an insulation resistance detection module, a self-checking module, an isolation module and a controller, and further comprises a switch assembly comprising a switch Kst, a switch KA and a switch Kp; the switch Kst is connected between the self-checking module and the insulation resistance detection module; when the switch Kst is controlled to be closed, a self-checking loop is formed to sample a self-checking resistance value; when the switch KA is controlled to be closed, an alternating current detection loop is formed to sample an alternating current equivalent resistance value; when the switch Kp is controlled to be closed, a direct current detection loop is formed to sample a direct current equivalent resistance value; the controller compares the self-checking resistance value with an actual self-checking value, the alternating current equivalent resistance value with an alternating current safety value and the direct current equivalent resistance value with a direct current safety value respectively to output an alarm signal. After the above technical scheme is adopted, the system is not affected by a leakage capacitor and hardware parameters are universal in a working voltage range.

Description

Technical Field

[0001] This invention relates to the field of automotive control, and more particularly to an insulation resistance monitoring system and method for electric vehicles. Background Technology

[0002] Electric vehicles, as an important means of transportation, contain many high-voltage components. Their operating environment is complex and harsh; vibration, impact, acid and alkaline gas corrosion, and changes in temperature and humidity can all affect electric vehicles, potentially causing rapid aging or even damage to the insulation materials of power cables and other high-voltage components. This significantly reduces their insulation performance and seriously endangers personal safety. To ensure the safe operation of the entire vehicle, these high-voltage components must have excellent insulation performance. According to GB-T 18384-2020, the minimum insulation resistance requirements for electric vehicles are: 100Ω / V DC and 500Ω / V AC. Therefore, real-time insulation resistance monitoring is essential and crucial for electric vehicles.

[0003] Therefore, the present invention provides a novel insulation resistance monitoring system for electric vehicles, which can periodically monitor the internal insulation resistance of electric vehicles during driving to provide immediate feedback on the driving status of electric vehicles. Summary of the Invention

[0004] In order to overcome the above-mentioned technical defects, the purpose of this invention is to provide an insulation resistance monitoring system and method for electric vehicles, which is not affected by the system leakage capacitance and whose hardware parameters are universal within the operating voltage range.

[0005] This invention discloses an insulation resistance monitoring system for electric vehicles, comprising an insulation resistance detection module, a self-test module, an isolation module, and a controller. The self-test module is connected to the insulation resistance detection module, and the controller is connected to the insulation resistance detection module via the isolation module.

[0006] The insulation resistance monitoring system also includes:

[0007] A switching assembly, connected to a controller, is controlled by the controller to switch between closed and open states. The switching assembly includes: switch Kst, switch KA, and switch Kp.

[0008] Switch Kst is connected between the self-test module and the insulation resistance detection module. When switch Kst is closed under control, the self-test module forms a self-test circuit to sample and form a self-test resistance value, which is then sent to the controller.

[0009] Switch KA is connected to the AC side of the insulation resistance detection module. When switch KA is closed under control, the AC side of the insulation resistance detection module forms an AC detection circuit to sample and form an AC equivalent resistance value, which is then sent to the controller.

[0010] Switch Kp is connected to the DC side of the insulation resistance detection module. When switch Kp is closed under control, the DC side of the insulation resistance detection module forms a DC detection circuit to sample and form a DC equivalent resistance value, which is then sent to the controller.

[0011] The controller compares the self-test resistance value with the preset actual self-test value, the AC equivalent resistance value with the preset AC safety value, and the DC equivalent resistance value with the preset DC safety value. When the self-test resistance value is less than the preset actual self-test value, and / or the AC equivalent resistance value is less than the preset AC safety value, and / or the DC equivalent resistance value is less than the preset DC safety value, the controller outputs an alarm signal.

[0012] Preferably, the self-test module includes:

[0013] A low-frequency current source Is is connected at one end to one end of a switch Kst;

[0014] One end of the resistor Rm is connected to the other end of the low-frequency current source Is.

[0015] The grounding terminal is connected to the other end of the resistor Rm;

[0016] The self-test resistor Rst is connected at one end to the other end of the switch Kst, and at the other end to the ground terminal.

[0017] When switch Kst is closed, a self-testing circuit is formed, consisting of low-frequency current source Is, self-testing resistor Rst, and resistor Rm.

[0018] Preferably, the controller is based on the following formula:

[0019] Im = Um / Rm calculates the current Im flowing through resistor Rm, where Um is the known voltage across resistor Rm;

[0020] The controller is based on the following formula:

[0021] Derivation and calculation of the self-test resistance value Rst: Us=Im*Rst+Um

[0022] Rst = (Us - Um) / Im, where Us is the known electromotive force of the low-frequency current source Is.

[0023] Preferably, the AC side of the insulation resistance detection module includes:

[0024] One end of resistor Ri is connected to one end of low-frequency current source Is, and the other end is connected to one end of switch KA;

[0025] RL networks, including:

[0026] Resistor RAG is connected at one end to switch KA and at the other end to ground.

[0027] One end of the inductor LA is connected to one end of the switch KA;

[0028] Resistor RBG has one end connected to the other end of inductor LA via inductor LB, and the other end connected to ground.

[0029] Resistor RCG has one end connected to the other end of inductor LA via inductor LC, and the other end connected to ground.

[0030] When switch KA is closed, an AC detection circuit is formed consisting of a low-frequency current source Is, a resistor Ri, an RL network, and a resistor Rm.

[0031] Preferably, the controller is based on the following formula:

[0032] Im = Um / Rm calculates the current Im flowing through resistor Rm, where Um is the known voltage across resistor Rm;

[0033] The controller is based on the following formula:

[0034] Us = Ui + Im * Rir_ac + Um Derivation and calculation of the AC equivalent resistance Rir_ac of the RL network:

[0035] Rir_ac=(Us-Ui-Um) / Im, where Us is the known electromotive force of the low-frequency current source Is, and Ui is the known voltage across the resistor Ri.

[0036] Preferably, one end of switch Kp is connected to one end of resistor Ri;

[0037] The DC side of the insulation resistance detection module includes:

[0038] RC networks, including:

[0039] One end of the resistor Rng is connected to one end of the switch Kp, and the other end is connected to the ground terminal;

[0040] One end of resistor Rpg is connected to one end of switch Kp, and the other end is connected to ground.

[0041] One end of capacitor Cyn is connected to one end of switch Kp, and the other end is connected to ground.

[0042] One end of capacitor Cyp is connected to one end of switch Kp, and the other end is connected to the ground terminal;

[0043] When switch Kp is closed, a DC detection circuit is formed consisting of low-frequency current source Is, resistor Ri, RC network, and resistor Rm.

[0044] Preferably, the controller is based on the following formula:

[0045] Im = Um / Rm calculates the current Im flowing through resistor Rm, where Um is the known voltage across resistor Rm;

[0046] The controller is based on the following formula:

[0047] Derivation and calculation of the DC equivalent resistance Rir_dc of the RC network: Us=Ui+Im*Rir_dc+Um

[0048] Rir_dc = (Us - Ui - Um) / Im, where Us is the known electromotive force of the low-frequency current source Is, and Ui is the known voltage across the resistor Ri.

[0049] The present invention also discloses an insulation resistance monitoring method for the insulation resistance monitoring system described above, comprising the following steps:

[0050] The insulation resistance monitoring system initializes after power-on reset;

[0051] When switch Kst is closed, the self-test module forms a self-test circuit for self-testing. The controller compares the self-test resistance value with the preset actual self-test value. When the number of consecutive times the self-test resistance value is less than the actual self-test value exceeds the first threshold, the controller issues the first alarm signal.

[0052] When the number of consecutive times the self-test resistance value is less than the actual self-test value is less than the first threshold, the controller determines that the insulation resistance of the self-test module is normal and disconnects switch Kst.

[0053] When switch Kp is closed, the insulation resistance detection module forms a DC detection circuit. The controller compares the DC equivalent resistance value with the preset DC safety value. When the number of consecutive times the DC equivalent resistance value is less than the DC safety value exceeds the second threshold, the controller issues a second alarm signal.

[0054] When the number of consecutive times the DC equivalent resistance is less than the DC safety value is less than the second threshold, the controller determines that the insulation resistance on the DC side of the insulation resistance detection module is normal and disconnects switch Kp.

[0055] When switch KA is closed, the insulation resistance detection module forms an AC detection circuit. The controller compares the AC equivalent resistance value with the preset AC safety value. When the number of consecutive times the AC equivalent resistance value is less than the AC safety value exceeds the third threshold, the controller issues a third alarm signal.

[0056] When the number of consecutive times the AC equivalent resistance is less than the AC safety value is less than the third threshold, the controller determines that the insulation resistance on the AC side of the insulation resistance detection module is normal and disconnects switch KA.

[0057] Compared with existing technologies, the above technical solution has the following advantages:

[0058] 1. It can quickly detect the insulation resistance value at various locations to determine the driving status of the electric vehicle;

[0059] 2. Anticipate potential malfunctions in electric vehicles and issue warnings in advance, thereby improving user safety when using electric vehicles. Attached Figure Description

[0060] Figure 1 This is a schematic diagram of the system structure of the insulation resistance monitoring system in a preferred embodiment of the present invention;

[0061] Figure 2 This is a circuit topology diagram of the insulation resistance monitoring system in a preferred embodiment of the present invention;

[0062] Figure 3 To conform to the circuit topology diagram of the self-test module in a preferred embodiment of the present invention;

[0063] Figure 4a To conform to the circuit topology diagram of the AC detection loop in a preferred embodiment of the present invention;

[0064] Figure 4b This is a schematic diagram of the equivalent topology of the AC detection loop in a preferred embodiment of the present invention;

[0065] Figure 5a To conform to the circuit topology diagram of the DC detection circuit in a preferred embodiment of the present invention;

[0066] Figure 5b This is a schematic diagram of the equivalent topology of the DC detection circuit in a preferred embodiment of the present invention;

[0067] Figure 6 A flowchart illustrating the insulation resistance monitoring method in a preferred embodiment of the present invention. Detailed Implementation

[0068] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

[0069] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0070] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0071] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0072] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0073] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0074] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.

[0075] See Figure 1To conform to the framework diagram of the insulation resistance monitoring system in a preferred embodiment of the present invention, in this embodiment, the insulation resistance monitoring system includes an insulation resistance detection module, a self-test module, an isolation module, and a controller. The insulation resistance detection module is used to detect whether the insulation resistance of the DC bus or AC bus of the electric vehicle's motor controller meets safety requirements. The self-test module is an internal module of the insulation resistance monitoring system that tests its own testing capabilities and safety. After completing the self-test, it connects to the insulation resistance detection module to initiate the testing of the insulation resistance detection module. The isolation module is connected between the controller and the insulation resistance detection module to electrically isolate the controller and prevent changes in insulation resistance from affecting the controller. In this embodiment, the insulation resistance monitoring system also includes:

[0076] A switching assembly, connected to a controller, is controlled by the controller to switch between closed and open states. The switching assembly includes: switch Kst, switch KA, and switch Kp. Specifically, switch Kst, switch KA, and switch Kp can be solid-state relays. Switch Kst is connected between the self-test module and the insulation resistance detection module. When switch Kst is closed under control (controlled by a command from the controller), the self-test module forms a self-test loop to sample the internal resistance and generate a self-test resistance value, which represents the magnitude of the insulation resistance within the self-test module, and is then sent to the controller. Switch KA is connected to the AC side of the insulation resistance detection module. When switch KA is closed under control (controlled by a command from the controller), the AC side of the insulation resistance detection module forms an AC detection loop to sample the insulation resistance on the AC bus side and generate an AC equivalent resistance value, which is then sent to the controller. Switch Kp is connected to the DC side of the insulation resistance detection module. When switch Kp is closed under control (controlled by a command from the controller), the DC side of the insulation resistance detection module forms a DC detection loop to sample the insulation resistance on the DC bus side and generate a DC equivalent resistance value, which is then sent to the controller. With the above data, the controller compares the self-test resistance value with the preset actual self-test value, the AC equivalent resistance value with the preset AC safety value, and the DC equivalent resistance value with the preset DC safety value. When the self-test resistance value is less than the preset actual self-test value, and / or the AC equivalent resistance value is less than the preset AC safety value, and / or the DC equivalent resistance value is less than the preset DC safety value, it indicates that the insulation capability represented by the insulation resistance has decreased, and the controller outputs an alarm signal. Preferably, the alarm signals output by the controller can be stepped. Specifically, the actual self-test value, AC safety value, and DC safety value can be set in steps. Once the value is less than a certain step, it indicates that the insulation resistance is too low. If the first step is exceeded, only an alarm message can be sent to the user, but no restrictions can be placed on driving behavior. If the second step is exceeded, an alarm command can be sent to the user, and some functions will be restricted if the alarm command is not cleared. If the third step is exceeded, the electric vehicle can be directly shut down, or the user can be prompted to pull over to seek assistance, thus providing different prompts to the user under various operating conditions.

[0077] See Figure 3The diagram illustrates a circuit topology design of a self-test module according to a preferred embodiment of the present invention. In this embodiment, the self-test module includes: a low-frequency current source Is, one end of which is connected to one end of a switch Kst; a resistor Rm, one end of which is connected to the other end of the low-frequency current source Is; a ground terminal, connected to the other end of the resistor Rm; and a self-test resistor Rst, one end of which is connected to the other end of the switch Kst, and the other end connected to the ground terminal. When the switch Kst is closed, a self-test loop is formed consisting of the low-frequency current source Is, the self-test resistor Rst, and the resistor Rm. Using the low-frequency current source Is as the power source, the insulation resistance within the self-test module is represented by the resistor Rst. Under the above topology configuration, the controller calculates the current Im flowing through the resistor Rm based on the following formula: Im = Um / Rm, where Um is the known voltage value across the resistor Rm, which can be obtained by connecting a sampling element to both ends of the resistor Rm and sending a sampling signal to both ends of the resistor Rm. Once the current Im is available, the controller derives and calculates the self-test resistance value Rst based on the following formula: Us=Im*Rst+Um: Rst=(Us-Um) / Im, where Us is the known electromotive force of the low-frequency current source Is. Through the above formula, the self-test resistance value Rst can be calculated, and then compared with the actual self-test value (which can be the impedance) in subsequent steps to check whether the self-test module is functioning properly.

[0078] See Figure 4a and Figure 4bTo detect whether the insulation resistance on the AC side of the insulation resistance detection module is within a safe range, the AC side of the insulation resistance detection module includes: a resistor Ri, one end of which is connected to one end of a low-frequency current source Is, and the other end of which is connected to one end of a switch KA; an RL network, including: a resistor RAG, one end of which is connected to one end of a switch KA, and the other end of which is connected to a ground terminal; an inductor LA, one end of which is connected to one end of a switch KA; a resistor RBG, one end of which is connected to the other end of an inductor LA via an inductor LB, and the other end of which is connected to a ground terminal; and a resistor RCG, one end of which is connected to the other end of an inductor LA via an inductor LC, and the other end of which is connected to a ground terminal. Inductors LA, LB, and LC are the inductance values ​​of phases A, B, and C of the motor, respectively, and resistors RAG, RBG, and RCG are the insulation resistance values ​​of phases A, B, and C of the motor to ground, respectively. Therefore, the inductors LA, LB, and LC, together with resistors RAG, RBG, and RCG, constitute the insulation resistance on the AC side of the insulation resistance detection module. When switch KA is closed, an AC detection loop is formed consisting of the low-frequency current source Is, resistor Ri, RL network, and resistor Rm. Under this topology, the controller calculates the current Im flowing through resistor Rm based on the following formula: Im = Um / Rm, where Um is the known voltage across resistor Rm. The controller derives and calculates the AC equivalent resistance Rir_ac of the RL network based on the following formula: Us = Ui + Im * Rir_ac + Um: Rir_ac = (Us - Ui - Um) / Im, where Us is the known electromotive force of the low-frequency current source Is, and Ui is the known voltage across resistor Ri. It can be understood that this AC equivalent resistance Rir_ac represents the equivalent value of the AC-side insulation network formed by inductors LA, LB, and LC, and resistors RAG, RBG, and RCG, and can be directly used to represent the insulation resistance or impedance of the AC side.

[0079] See Figure 5a and 5bTo detect whether the insulation resistance on the DC side of the insulation resistance detection module is within a safe range, one end of switch Kp is connected to one end of resistor Ri. The DC side of the insulation resistance detection module includes: resistor Rng, one end of which is connected to one end of switch Kp and the other end is connected to ground; resistor Rpg, one end of which is connected to one end of switch Kp and the other end is connected to ground; capacitor Cyn, one end of which is connected to one end of switch Kp and the other end is connected to ground; and capacitor Cyp, one end of which is connected to one end of switch Kp and the other end is connected to ground. Resistor Rpg is the insulation resistance of the positive DC bus to ground, and resistor Rng is the insulation resistance of the negative DC bus to ground. Thus, resistors Rng, Rpg, Cyn, and Cyp together form the insulation resistance on the DC side of the insulation resistance detection module. When switch Kp is closed, a DC detection loop is formed from the low-frequency current source Is, resistor Ri, RC network, and resistor Rm. Under the above topology configuration, the controller calculates the current Im flowing through resistor Rm based on the following formula: Im = Um / Rm, where Um is the known voltage across resistor Rm; the controller derives and calculates the DC equivalent resistance Rir_dc of the RC network based on the following formula: Us = Ui + Im * Rir_dc + Um: Rir_dc = (Us - Ui - Um) / Im, where Us is the known electromotive force of the low-frequency current source Is, and Ui is the known voltage across resistor Ri. It can be understood that this DC equivalent resistance Rir_dc represents the equivalent value of the DC-side insulation network formed by resistors Rng, Rpg, Cyn, and Cyp, and can be directly used to represent the magnitude of the DC-side insulation resistance or impedance.

[0080] See Figure 2 The topology of the self-test module and the insulation resistance detection module is integrated to form the system schematic of the entire insulation resistance detection. The DC-side battery has extremely low impedance and can be ignored when calculating the DC-side insulation resistance. The two grounding terminals can be the same, allowing for normal connection between the DC and AC sides.

[0081] See Figure 6 A schematic flowchart of an insulation resistance monitoring method is shown. In this embodiment, the method includes the following steps:

[0082] -Insulation resistance monitoring system initializes after power-on reset;

[0083] - When switch Kst is closed, the self-test module forms a self-test circuit for self-testing. The controller compares the self-test resistance value with the preset actual self-test value (the self-test count is incremented by one after each self-test). When the number of consecutive times the self-test resistance value is less than the actual self-test value exceeds a first threshold (e.g., 3 times), the controller issues a first alarm signal. Preferably, after the first alarm signal is issued, the insulation resistance at other locations can be stopped to indicate that the requirements for safe driving cannot be met under the first alarm signal.

[0084] - When the number of consecutive times the self-test resistance value is less than the actual self-test value is less than the first threshold, the controller determines that the insulation resistance of the self-test module is normal and disconnects switch Kst;

[0085] - The self-test count is reset to zero, switch Kp is closed, the insulation resistance detection module forms a DC detection circuit, and the controller compares the DC equivalent resistance value with the preset DC safety value (the DC detection count is incremented by one after each comparison). When the number of consecutive times the DC equivalent resistance value is less than the DC safety value exceeds the second threshold (e.g., 3 times), the controller issues a second alarm signal. Preferably, after the second alarm signal is issued, the insulation resistance at other locations can no longer be detected, indicating that the requirements for safe driving cannot be met under the second alarm signal.

[0086] - When the number of consecutive times the DC equivalent resistance is less than the DC safety value is less than the second threshold, the controller determines that the insulation resistance on the DC side of the insulation resistance detection module is normal and disconnects switch Kp;

[0087] - The DC side detection count is reset to zero. When switch KA is closed, the insulation resistance detection module forms an AC detection loop. The controller compares the AC equivalent resistance value with the preset AC safety value (the AC side detection count is incremented by one after each comparison). When the number of consecutive times the AC equivalent resistance value is less than the AC safety value exceeds the third threshold (e.g., 3 times), the controller issues a third alarm signal.

[0088] - When the number of consecutive times the AC equivalent resistance is less than the AC safety value is less than the third threshold, the controller determines that the insulation resistance on the AC side of the insulation resistance detection module is normal and disconnects switch KA.

[0089] The above monitoring methods can be used to periodically check the latest safety of electric vehicles in terms of insulation resistance.

[0090] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. An insulation resistance monitoring system for an electric vehicle, comprising an insulation resistance detection module, a self-checking module, an isolation module and a controller, the self-checking module being connected to the insulation resistance detection module, the controller being connected to the insulation resistance detection module via the isolation module, characterized in that the insulation resistance monitoring system further comprises: a switch assembly connected to the controller and controlled by the controller to switch between a closed state and an open state, wherein the switch assembly comprises a switch Kst, a switch KA and a switch Kp; the switch Kst is connected between the self-checking module and the insulation resistance detection module, when the switch Kst is controlled to be closed, the self-checking module forms a self-checking loop to sample a self-checking resistance value and send it to the controller; the switch KA is connected to an AC side of the insulation resistance detection module, when the switch KA is controlled to be closed, the AC side of the insulation resistance detection module forms an AC detection loop to sample an AC equivalent resistance value and send it to the controller; the switch Kp is connected to a DC side of the insulation resistance detection module, when the switch Kp is controlled to be closed, the DC side of the insulation resistance detection module forms a DC detection loop to sample a DC equivalent resistance value and send it to the controller; the controller compares the self-checking resistance value with a preset actual self-checking value, the AC equivalent resistance value with a preset AC safety value, and the DC equivalent resistance value with a preset DC safety value, respectively, and outputs an alarm signal when the self-checking resistance value is less than the preset actual self-checking value, and / or the AC equivalent resistance value is less than the preset AC safety value, and / or the DC equivalent resistance value is less than the preset DC safety value; the self-checking module comprises: a low-frequency current source Is, one end of which is connected to one end of the switch Kst; a resistor Rm, one end of which is connected to the other end of the low-frequency current source Is; a ground terminal, the other end of the resistor Rm being connected to the ground terminal; a self-checking resistor Rst, one end of which is connected to the other end of the switch Kst and the other end of which is connected to the ground terminal; when the switch Kst is closed, a self-checking loop is formed from the low-frequency current source Is, the self-checking resistor Rst and the resistor Rm; the AC side of the insulation resistance detection module comprises: a resistor Ri, one end of which is connected to one end of the low-frequency current source Is and the other end of which is connected to one end of the switch KA; an RL network comprising: a resistor RAG, one end of which is connected to one end of the switch KA and the other end of which is connected to the ground terminal; an inductor LA, one end of which is connected to one end of the switch KA; a resistor RBG, one end of which is connected to the other end of the inductor LA via an inductor LB and the other end of which is connected to the ground terminal; a resistor RCG, one end of which is connected to the other end of the inductor LA via an inductor LC and the other end of which is connected to the ground terminal, so that the inductor LA, the inductor LB and the inductor LC, and the resistor RAG, the resistor RBG and the resistor RCG together form an insulation resistance of the AC side of the insulation resistance detection module; when the switch KA is closed, an AC detection loop is formed from the low-frequency current source Is, the resistor Ri, the RL network and the resistor Rm. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2.The insulation resistance monitoring system of claim 1, wherein the controller calculates the current Im flowing through the resistance Rm based on the following formula: wherein Um is a known voltage value across the resistance Rm. The controller derives and calculates the self-checking resistance value Rst of the self-checking resistance Rst based on the following formula: wherein Us is a known electromotive force of the low-frequency current source Is. 3.The insulation resistance monitoring system of claim 1, wherein the controller calculates the current Im flowing through the resistance Rm based on the following formula: wherein Um is a known voltage value across the resistance Rm. The controller derives and calculates the AC equivalent resistance value Rir_ac of the RL network based on the following formula: wherein Us is a known electromotive force of the low-frequency current source Is, and Ui is a known voltage value across the resistance Ri. 4.The insulation resistance monitoring system of claim 1, wherein one end of the switch Kp is connected to one end of the resistance Ri. The DC side of the insulation resistance detection module comprises: a RC network comprising: a resistance Rng having one end connected to one end of the switch Kp and the other end connected to a ground terminal; a resistance Rpg having one end connected to one end of the switch Kp and the other end connected to a ground terminal; a capacitor Cyn having one end connected to one end of the switch Kp and the other end connected to a ground terminal; a capacitor Cyp having one end connected to one end of the switch Kp and the other end connected to a ground terminal; when the switch Kp is closed, a DC detection loop is formed from the low-frequency current source Is, the resistance Ri, the RC network, and the resistance Rm. 5.The insulation resistance monitoring system of claim 4, wherein the controller calculates the current Im flowing through the resistance Rm based on the following formula: wherein Um is a known voltage value across the resistance Rm. The controller derives and calculates the DC equivalent resistance value Rir_dc of the RC network based on the following formula: wherein Us is a known electromotive force of the low-frequency current source Is, and Ui is a known voltage value across the resistance Ri. comprising the following steps: initializing after the insulation resistance monitoring system is powered on and reset; closing the switch Kst, the self-checking module forms a self-checking loop for self-checking, and the controller compares the self-checking resistance value with a preset actual self-checking value, when the number of times that the self-checking resistance value is less than the actual self-checking value is greater than a first threshold value, the controller sends a first alarm signal; when the number of times that the self-checking resistance value is less than the actual self-checking value is less than the first threshold value, the controller determines that the insulation resistance of the self-checking module is normal, and the switch Kst is opened. ​ ​ ​ ​ ​ ​ ​ ​ ​ 6. An insulation resistance monitoring method of the insulation resistance monitoring system according to claim 1, characterized by, ​ ​ ​ ​ When switch Kp is closed, the insulation resistance detection module forms a DC detection circuit. The controller compares the DC equivalent resistance value with the preset DC safety value. When the number of consecutive times the DC equivalent resistance value is less than the DC safety value exceeds the second threshold, the controller issues a second alarm signal. When the number of consecutive times the DC equivalent resistance is less than the DC safety value is less than the second threshold, the controller determines that the insulation resistance on the DC side of the insulation resistance detection module is normal and disconnects switch Kp. When switch KA is closed, the insulation resistance detection module forms an AC detection circuit. The controller compares the AC equivalent resistance value with the preset AC safety value. When the number of consecutive times the AC equivalent resistance value is less than the AC safety value exceeds the third threshold, the controller issues a third alarm signal. When the number of consecutive times the AC equivalent resistance value is less than the AC safety value is less than the third threshold, the controller determines that the insulation resistance on the AC side of the insulation resistance detection module is normal and disconnects switch KA.

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