System and method for measuring insulation resistance by fusing direct current and alternating current
By integrating the DC bridge method and the AC injection method with a dynamic weighted average algorithm, the problems of large error and insufficient anti-interference ability in the insulation resistance measurement of high-voltage systems in electric vehicles are solved. This achieves high-precision insulation resistance detection under all operating conditions and is suitable for insulation performance testing of high-voltage systems in electric vehicles.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-09
- Publication Date
- 2026-03-24
AI Technical Summary
Existing technologies for measuring insulation resistance in high-voltage systems of electric vehicles suffer from large measurement errors and insufficient anti-interference capabilities, especially under dynamic operating conditions where they are difficult to accurately reflect the insulation status.
The system employs a fusion of DC bridge and AC injection methods, combining signal generation and control modules, measurement circuit modules, signal detection and processing modules, and data fusion and analysis modules. It adjusts the measurement method in real time through a dynamic weighted average algorithm, integrates DC bridge and AC injection methods, and utilizes a microcontroller to control signal switching and data fusion to achieve high-precision insulation resistance measurement.
Significantly improves measurement accuracy and applicability, reduces cost and power consumption, and enables stable measurement under all operating conditions. It is suitable for insulation resistance testing of high-voltage systems in electric vehicles, ensuring the safety of drivers and passengers and the reliability of vehicles.
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Figure CN121721364A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electric vehicle testing technology, and in particular to a system and method for measuring the insulation resistance of high-voltage systems in electric vehicles that combines the DC bridge method and the AC injection method. It is applicable to the insulation performance testing of core high-voltage components such as power battery packs, high-voltage distribution boxes, and drive motor controllers in pure electric vehicles and hybrid electric vehicles. Background Technology
[0002] During the operation of electric vehicles, the insulation performance of the high-voltage system (typically 300V-800V) directly affects the safety of passengers and the reliability of the vehicle. Insulation resistance is a core indicator for assessing the insulation status of high-voltage components in electric vehicles, and its measurement accuracy is crucial for preventing high-voltage leakage and avoiding electric shock accidents. Currently, the commonly used insulation resistance measurement methods in the electric vehicle field mainly include the DC bridge method and the AC injection method. Both of these traditional methods have the following significant limitations in the complex operating environment of electric vehicles.
[0003] The DC bridge method, based on the unbalanced bridge method, is simple in principle and low in cost, and is widely used in laboratory static testing. However, the high-voltage system of electric vehicles has dynamic characteristics. The voltage of the power battery fluctuates significantly during charging and discharging (e.g., the voltage range of lithium iron phosphate batteries is 2.5V-3.65V / cell, and the fluctuation range can reach 10%-20% after assembly). The start and stop of the drive motor and the operation of the air conditioning compressor can cause sudden changes in the high-voltage circuit current. These factors can directly disrupt the balance of the bridge, leading to a sharp increase in measurement error. In addition, high-voltage components in electric vehicles often have distributed capacitance, which can easily generate polarization effects during DC measurement, further aggravating measurement deviations and failing to accurately reflect the insulation status during vehicle dynamic operation.
[0004] The AC injection method injects a specific frequency AC signal into a high-voltage system and calculates the insulation resistance using impedance analysis, effectively avoiding the influence of DC voltage fluctuations. Therefore, it is increasingly used in vehicle dynamic testing. However, the electromagnetic interference in the electric vehicle operating environment is extremely complex: high-frequency harmonics generated by the drive motor, switching noise from the on-board inverter, and electromagnetic radiation from the wireless charging system all superimpose with the injected AC signal, leading to signal distortion. Simultaneously, the distributed parameters of the high-voltage cable and the equivalent impedance of the power battery change with operating conditions, making the conversion relationship between AC impedance and insulation resistance unstable and increasing measurement difficulty. Traditional AC injection methods suffer from insufficient anti-interference capabilities and poor parameter adaptability; under complex conditions such as high-speed driving and rapid acceleration, measurement errors often exceed 20%, failing to meet safety standards. Summary of the Invention
[0005] The purpose of this invention is to provide a system and method for measuring insulation resistance by integrating direct current and alternating current, so as to solve the problems mentioned in the background art.
[0006] To achieve the above objectives, the present invention provides the following technical solution: A system and method for measuring insulation resistance by integrating direct current and alternating current, comprising: a signal generation and control module, a measurement circuit module, a signal detection and processing module, and a data fusion and analysis module; the core of the signal generation and control module is a microcontroller.
[0007] The measurement circuit module integrates a DC bridge circuit with resistors and switches forming the bridge arms and an AC injection circuit.
[0008] The signal detection and processing module includes circuits for acquiring and amplifying voltage signals from the DC current method and AC signals from the AC injection method. The data fusion and analysis module uses a dynamic weighted average algorithm based on the variance of DC voltage fluctuations to fuse the DC and AC measurement results.
[0009] The DC bridge circuit has six arms, four of which are one or more resistors and switches, and the other two arms are the insulation resistance RF+ from the positive terminal of the battery pack to the vehicle ground, and the insulation resistance RF- from the negative terminal of the battery pack to the vehicle ground; the AC signal injection circuit includes an AC power supply, a voltage-bearing resistor, and a measuring resistor.
[0010] The DC bridge circuit is based on the unbalanced bridge method and has six bridge arms, with R... DC1 R DC2 R DC4 and R DC5 R is a voltage-bearing resistor. DC3 To measure resistance, there is a SW. DC1 SW DC2 and SW DC3 It is an isolating switch; the signal generation and control module generates a switch control signal; The AC injection circuit includes an AC signal, an isolation amplifier, a voltage-bearing resistor, a measuring resistor, a disconnect switch, a positive injection branch, a negative injection branch, and a power circuit. The AC signal in the AC injection circuit is isolated and amplified by the isolation amplifier, and then injected into the power circuit through the positive and negative injection branches. AC1 and R AC2 R is a voltage-bearing resistor. AC3 and R AC4 To measure resistance, before starting the measurement, a disconnect switch SW controlled by a microcontroller is used. DC1 and SW AC1 It can be connected to either a DC bridge circuit or an AC injection circuit.
[0011] The dynamic weight w in the data fusion of the dynamic weighted average algorithm satisfies: w = 1 / (1 + k * ΔV) 2), where ΔV is the absolute value of the difference between the current DC voltage measurement and the previous DC voltage measurement, and k is a preset empirical coefficient.
[0012] The signal generation and control module is a single-chip microcomputer. It is responsible for generating the switching control signals required by the DC bridge method, the AC signals with specific frequencies and amplitudes required by the AC injection method, and the AC / DC measurement mode switching signals.
[0013] The switch control signal is generated by a microcontroller. The AC signal is generated by the microcontroller's internal ADC chip or an external ADC chip, combined with a direct digital frequency or pulse width modulation wave that is filtered and shaped. The AC signal frequency is 1kHz–10kHz and the amplitude is 0–50V.
[0014] A method for measuring insulation resistance by integrating direct current and alternating current, based on the system described in any one of claims 1-9, includes the following steps: S1. System Initialization: After the system is powered on, the signal generation and control module initializes the system parameters. By default, ΔV is set to 0, the AC signal source is turned off, and the DC bridge method is used to measure insulation resistance. SW is disconnected. DC2 SW DC3 and SW AC1 Close SW DC1 Measure the initial voltage VB0 across the battery pack; close SW. DC1 and SW DC2 Record R DC3 Voltage V at both ends DC1 Close SW DC1 and SW DC3 Record R DC3 Voltage V at both ends DC2 According to V DC1 and V DC2 Calculate the initial insulation resistance measurement value Riso m0 ; S2. Measure the voltage across the current battery pack terminals and disconnect SW. DC2 SW DC3 and SW AC1 Close SW DC1 Measure R DC3 Voltage V at both ends DC0 Calculate the initial voltage VB across the battery pack. t ; S3. AC / DC measurement mode switching judgment, based on the previous battery pack voltage VB. t-1 Calculate ΔV = |VB t -VB t-1 |;If ΔV is less than the voltage fluctuation threshold V thIf the current power circuit voltage is considered stable, the insulation resistance is measured using the DC bridge method; if ΔV is greater than the voltage fluctuation threshold V... th If the voltage of the current power circuit is considered to fluctuate significantly, the insulation resistance is measured using the AC injection method, and the current insulation resistance measurement value is denoted as Riso. m .
[0015] S4. Measuring Insulation Resistance: If using the DC bridge method to measure insulation resistance, close SW. DC1 and SW DC2 Record R DC3 Voltage V at both ends DC1 Close SW DC1 and SW DC3 Record R DC3 Voltage V at both ends DC2 According to V DC1 and V DC2 Calculate the insulation resistance measurement value Riso m If the AC injection method is used to measure insulation resistance, close SW. AC1 Turn on the AC signal source and measure R AC3 Voltage V across the terminals AC1 , and R AC4 Voltage V across the terminals AC2 Calculate the insulation resistance measurement value Riso m Then turn off the AC signal source; S5. Data Fusion and Result Output: Current Insulation Resistance Output Value Riso t Compared to the previous output value Riso t-1 and the current measurement value Riso m Related to, i.e., Riso t =w*Riso m +(1-w)* Riso t-1 Where w is the dynamic weight for data fusion, w = 1 / (1+k*ΔV) 2 ), where k is a preset empirical value.
[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of this application are: (1) Significantly improve measurement accuracy: Equipped with a dynamic weighting algorithm based on voltage fluctuation variance, the weight ratio of the current measurement value and the historical output value is adjusted in real time. When the voltage fluctuation is small, the accuracy of DC measurement is enhanced, and when the fluctuation is large, the stability of AC measurement is highlighted. It effectively suppresses the error caused by interference. Compared with the traditional AC injection method, the accuracy is greatly improved, and the insulation status of the high voltage system is truly reflected.
[0017] (2) Expand the scope of application: The innovative dual-branch integrated design of "DC bridge method + AC injection method" is adopted. The working condition is intelligently judged by the voltage fluctuation value ΔV: when the voltage is stable (ΔV < threshold), the DC bridge method is activated to balance low cost and static measurement accuracy; when the voltage fluctuation is obvious or the electromagnetic interference is strong (ΔV > threshold), the AC injection method is automatically switched to avoid DC polarization effect and high frequency interference, and the measurement deviation problem of traditional methods under dynamic working conditions such as vehicle charging and discharging and motor start and stop is completely solved, achieving stable coverage of all working conditions.
[0018] (3) Reduced cost and power consumption: The microcontroller is used as the core control unit, which simplifies the hardware architecture and significantly reduces the R&D and manufacturing costs compared with dedicated high-precision measurement chips. At the same time, it integrates components such as isolating switches and isolation amplifiers to improve the system's anti-interference capability and insulation safety. It is suitable for 300V-800V high-voltage operating environment and can be directly applied to vehicle dynamic detection, making it highly practical for engineering applications.
[0019] (4) Full-process automation: It realizes full-process automated control of "operating condition judgment - branch switching - signal acquisition - data fusion - result output", without manual intervention, with fast response speed, which can meet the real-time monitoring needs of insulation resistance during the operation of electric vehicles, timely capture insulation abnormalities (such as leakage), provide proactive protection for the life safety of drivers and passengers, and improve the reliability of vehicle operation. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of the integrated DC / AC insulation resistance measurement system of this application; Figure 2 This is the circuit diagram for the DC bridge method measurement in this application; Figure 3 This is a circuit diagram for measuring the AC injection method in this application; Figure 4 This is a flowchart of the testing process for this application. Detailed Implementation
[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, 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.
[0022] like Figure 1As shown, this application discloses a system and method for measuring insulation resistance using both DC and AC currents, comprising: a signal generation and control module, a measurement circuit module, a signal detection and processing module, and a data fusion and analysis module; the core of the signal generation and control module is a microcontroller. The measurement circuit module integrates a DC bridge circuit (with resistors and switches forming the bridge arms) and an AC injection circuit. The signal detection and processing module includes circuits for acquiring and amplifying the voltage signal from the DC current method and the AC signal from the AC injection circuit. The data fusion and analysis module uses a dynamic weighted average algorithm based on the variance of DC voltage fluctuations to fuse the DC and AC measurement results.
[0023] like Figure 2 and Figure 3 As shown, the DC bridge circuit has six arms, four of which are one or more resistors and switches, and the other two arms are the insulation resistance RF+ from the positive terminal of the battery pack to the vehicle ground, and the insulation resistance RF- from the negative terminal of the battery pack to the vehicle ground; the AC signal injection circuit includes an AC power supply, a voltage-bearing resistor, and a measuring resistor.
[0024] The DC bridge circuit is based on the unbalanced bridge method and has six bridge arms, with R... DC1 R DC2 R DC4 and R DC5 R is a voltage-bearing resistor. DC3 To measure resistance, there is a SW. DC1 SW DC2 and SW DC3 It is an isolating switch; the signal generation and control module generates a switch control signal; The AC injection circuit includes an AC signal, an isolation amplifier, a voltage-bearing resistor, a measuring resistor, a disconnect switch, a positive injection branch, a negative injection branch, and a power circuit. The AC signal in the AC injection circuit is isolated and amplified by the isolation amplifier, and then injected into the power circuit through the positive and negative injection branches. AC1 and R AC2 R is a voltage-bearing resistor. AC3 and R AC4 To measure resistance, before starting the measurement, a disconnect switch SW controlled by a microcontroller is used. DC1 and SW AC1 It can be connected to either a DC bridge circuit or an AC injection circuit.
[0025] The dynamic weight w in the data fusion of the dynamic weighted average algorithm satisfies: w = 1 / (1 + k * ΔV) 2 ), where ΔV is the absolute value of the difference between the current DC voltage measurement and the previous DC voltage measurement, and k is a preset empirical coefficient.
[0026] The signal generation and control module is a single-chip microcomputer. It is responsible for generating the switching control signals required by the DC bridge method, the AC signals with specific frequencies and amplitudes required by the AC injection method, and the AC / DC measurement mode switching signals.
[0027] The switch control signal is generated by a microcontroller. The AC signal is generated by the microcontroller's internal ADC chip or an external ADC chip, combined with a direct digital frequency or pulse width modulation wave that is filtered and shaped. The AC signal frequency is 1kHz–10kHz and the amplitude is 0–50V.
[0028] like Figure 4 As shown, a method for measuring insulation resistance by integrating direct current and alternating current, based on the above-described system, includes the following steps: Step 1, System Initialization: After the system is powered on, the signal generation and control module initializes the system parameters. By default, ΔV is set to 0, the AC signal source is turned off, and the DC bridge method is used to measure insulation resistance. Disconnect SW. DC2 SW DC3 and SW AC1 Close SW DC1 Measure the initial voltage VB0 across the battery pack; close SW. DC1 and SW DC2 Record R DC3 Voltage V at both ends DC1 Close SW DC1 and SW DC3 Record R DC3 Voltage V at both ends DC2 According to V DC1 and V DC2 Calculate the initial insulation resistance measurement value Riso m0 ; Step 2. Measure the voltage across the current battery pack terminals and disconnect SW. DC2 SW DC3 and SW AC1 Close SW DC1 Measure R DC3 Voltage V at both ends DC0 Calculate the initial voltage VB across the battery pack. t ; Step 3. AC / DC measurement mode switching judgment, based on the previous battery pack voltage VB. t-1 Calculate ΔV = |VB t -VB t-1 |;If ΔV is less than the voltage fluctuation threshold V th If the current power circuit voltage is considered stable, the insulation resistance is measured using the DC bridge method; if ΔV is greater than the voltage fluctuation threshold V... thIf the voltage of the current power circuit is considered to fluctuate significantly, the insulation resistance is measured using the AC injection method, and the current insulation resistance measurement value is denoted as Riso. m .
[0029] Step 4. Measure the insulation resistance: If using the DC bridge method to measure the insulation resistance, close SW. DC1 and SW DC2 Record R DC3 Voltage V at both ends DC1 Close SW DC1 and SW DC3 Record R DC3 Voltage V at both ends DC2 According to V DC1 and V DC2 Calculate the insulation resistance measurement value Riso m If the AC injection method is used to measure insulation resistance, close SW. AC1 Turn on the AC signal source and measure R AC3 Voltage V across the terminals AC1 , and R AC4 Voltage V across the terminals AC2 Calculate the insulation resistance measurement value Riso m Then turn off the AC signal source; Step 5. Data Fusion and Result Output: Current Insulation Resistance Output Value Riso t Compared to the previous output value Riso t-1 and the current measurement value Riso m Related to, i.e., Riso t =w*Riso m +(1-w)* Riso t-1 Where w is the dynamic weight for data fusion, w = 1 / (1+k*ΔV) 2 ), where k is a preset empirical value.
[0030] 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. A system integrating DC and AC measurement of insulation resistance, characterized in that, include: The module includes a signal generation and control module, a measurement circuit module, a signal detection and processing module, and a data fusion and analysis module.
2. The system for measuring insulation resistance by integrating direct current and alternating current according to claim 1, characterized in that: The measurement circuit module integrates a DC bridge circuit and an AC injection circuit, and the core of the signal generation and control module includes a microcontroller.
3. The system for measuring insulation resistance by integrating direct current and alternating current according to claim 2, characterized in that: The signal detection and processing module includes a circuit for acquiring and amplifying voltage signals from resistors using the DC current method and AC signals from the AC injection method.
4. The system for measuring insulation resistance by integrating direct current and alternating current according to claim 3, characterized in that: The data fusion and analysis module uses a dynamic weighted average algorithm based on DC voltage fluctuation variance to fuse DC and AC measurement results.
5. A system for measuring insulation resistance by integrating direct current and alternating current according to claim 2, characterized in that: The DC bridge circuit has six arms, four of which are one or more resistors and switches, and the other two arms are the insulation resistance RF+ from the positive terminal of the battery pack to the vehicle ground, and the insulation resistance RF- from the negative terminal of the battery pack to the vehicle ground; the AC signal injection circuit includes an AC power supply, a voltage-bearing resistor, and a measuring resistor.
6. The system for measuring insulation resistance by integrating direct current and alternating current according to claim 5, characterized in that: The DC bridge circuit is built based on the unbalanced bridge method and has six bridge arms, with R... DC1 R DC2 R DC4 and R DC5 R is a voltage-bearing resistor. DC3 To measure resistance, there is a SW. DC1 SW DC2 and SW DC3 It is an isolating switch; the signal generation and control module generates a switch control signal; The AC injection circuit includes an AC signal, an isolation amplifier, a voltage-bearing resistor, a measuring resistor, an isolating switch, a positive injection branch, a negative injection branch, and a power circuit. The AC signal in the AC injection circuit is isolated and amplified by the isolation amplifier, and then injected into the power circuit through the positive and negative injection branches. AC1 and R AC2 R is a voltage-bearing resistor. AC3 and R AC4 To measure resistance, before starting the measurement, a disconnect switch SW controlled by a microcontroller is used. DC1 and SW AC1 It can be connected to either a DC bridge circuit or an AC injection circuit.
7. A system for measuring insulation resistance by integrating direct current and alternating current according to claim 4, characterized in that: The dynamic weighted average algorithm's data fusion dynamic weight w satisfies: w = 1 / (1 + k * ΔV) 2 ), where ΔV is the absolute value of the difference between the current DC voltage measurement and the previous DC voltage measurement, and k is a preset empirical coefficient.
8. The system for measuring insulation resistance by integrating direct current and alternating current according to claim 1, characterized in that: The signal generation and control module is a single-chip microcomputer. The signal generation and control module is responsible for generating the switching control signal required by the DC bridge method, the AC signal with specific frequency and amplitude required by the AC injection method, and the AC / DC measurement mode switching signal.
9. A system for measuring insulation resistance by integrating direct current and alternating current according to claim 8, characterized in that: The switch control signal is generated by a microcontroller. The AC signal is generated by the microcontroller's internal ADC chip or an external ADC chip, combined with a direct digital frequency or pulse width modulation wave that is filtered and shaped. The AC signal frequency is 1kHz–10kHz and the amplitude is 0–50V.
10. A method for measuring insulation resistance by integrating direct current and alternating current, based on the system described in any one of claims 1-9, comprising the following steps: S1. System Initialization: After the system is powered on, the signal generation and control module initializes the system parameters. By default, ΔV is set to 0, the AC signal source is turned off, and the DC bridge method is used to measure insulation resistance. SW is disconnected. DC2 SW DC3 and SW AC1 Close SW DC1 Measure the initial voltage VB0 across the battery pack; close SW. DC1 and SW DC2 Record R DC3 Voltage V at both ends DC1 Close SW DC1 and SW DC3 Record R DC3 Voltage V at both ends DC2 According to V DC1 and V DC2 Calculate the initial insulation resistance measurement value Riso m0 ; S2. Measure the voltage across the current battery pack terminals and disconnect SW. DC2 SW DC3 and SW AC1 Close SW DC1 Measure R DC3 Voltage V at both ends DC0 Calculate the initial voltage VB across the battery pack. t ; S3. AC / DC measurement mode switching judgment, based on the previous battery pack voltage VB. t-1 Calculate ΔV = |VB t -VB t-1 |;If ΔV is less than the voltage fluctuation threshold V th If the current power circuit voltage is considered stable, the insulation resistance is measured using the DC bridge method; if ΔV is greater than the voltage fluctuation threshold V... th If the voltage of the current power circuit is considered to fluctuate significantly, the insulation resistance is measured using the AC injection method, and the current insulation resistance measurement value is denoted as Riso. m； S4. Measuring Insulation Resistance: If using the DC bridge method to measure insulation resistance, close SW. DC1 and SW DC2 Record R DC3 Voltage V at both ends DC1 Close SW DC1 and SW DC3 Record R DC3 Voltage V at both ends DC2 According to V DC1 and V DC2 Calculate the insulation resistance measurement value Riso m If the AC injection method is used to measure insulation resistance, close SW. AC1 Turn on the AC signal source and measure R AC3 Voltage V across the terminals AC1 , and R AC4 Voltage V across the terminals AC2 Calculate the insulation resistance measurement value Riso m Then turn off the AC signal source; S5. Data Fusion and Result Output: Current Insulation Resistance Output Value Riso t Compared to the previous output value Riso t-1 and the current measurement value Riso m Related to, i.e., Riso t =w* Riso m +(1-w)*Riso t-1 Where w is the dynamic weight for data fusion, w = 1 / (1+k*ΔV) 2 ), where k is a preset empirical value.