Interference positioning method of conduction voltage method

Abstract

The invention relates to the technical field of electric drive system fault positioning, in particular to a conductive voltage method interference positioning method which is used for systematically positioning conductive voltage method interference of a to-be-detected electric drive system. The method comprises the following steps: in an electromagnetic compatibility darkroom, carrying out a background noise test before a to-be-tested electric drive system is powered on, and obtaining a background noise spectrum; according to the method, strict verification of background noise is introduced to ensure that all subsequent test data truly reflect the characteristics of the tested equipment, environmental variable interference is eliminated, quantitative separation of common-mode interference and differential-mode interference is combined, a traditional positioning mode depending on experience guess is changed, and the positioning accuracy is improved. According to the invention, the dominant component (common mode or differential mode) of interference and the corresponding specific frequency band can be accurately identified, and misjudgment is avoided fundamentally, so that the fault positioning efficiency and precision are improved.

Description

Technical Field

[0001] This invention relates to the field of fault location technology for electric drive systems, and in particular to an interference location method based on conducted voltage. Background Technology

[0002] With the continuous improvement of the intelligence level of new energy vehicles, higher requirements are being placed on the electromagnetic compatibility (EMC) of electronic components. As the core power drive component of new energy vehicles, the EMC performance of the electric drive system directly affects the reliability and compliance of the entire vehicle. Among them, the conducted voltage method (CEV) is one of the most complex and risky EMC tests for electric drive systems. Due to the numerous variables affecting CEV, traditional methods often rely on experience and trial and error during testing and rectification, lacking systematic and scientific positioning and rectification methods.

[0003] Currently, the CEV testing and remediation methods commonly used in the industry have significant shortcomings. A typical process includes: sample preparation, test environment setup, rough noise floor testing, direct CEV testing, and then arbitrarily speculating on interference sources based on the test results, followed by repeated trial and error remediation. This method lacks precise differentiation between common-mode and differential-mode interference and fails to systematically investigate interference within the test environment itself, leading to inaccurate problem localization and blind remediation measures. It often falls into a cycle of "guessing-testing-failure," resulting in a significant waste of time, manpower, and financial resources.

[0004] Furthermore, traditional methods are ill-suited to the rapid iteration demands of electric drive product development. Without a scientifically sound logical framework, troubleshooters cannot effectively identify the source and propagation path of interference, often leading to over-design or under-design issues in product design. This not only increases development costs but also severely restricts the competitiveness and market responsiveness of electric drive systems. Therefore, a technical method is urgently needed to systematically, quickly, and accurately locate and rectify CEV problems. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an interference location method based on the conduction voltage method, so as to improve the efficiency and accuracy of fault location.

[0006] In a first aspect, embodiments of this application provide a method for locating interference using the conducted voltage method. This method is used to systematically locate conducted voltage method interference in an electric drive system under test. The method includes: In an electromagnetic compatibility anechoic chamber, a background noise test is performed on the electric drive system under test before power-on to obtain the background noise spectrum; If the background noise spectrum is lower than the standard limit by a preset margin in the entire test frequency band, the conducted voltage method test is performed after the electric drive system under test is powered on, and the positive channel voltage and negative channel voltage are measured respectively. Common-mode interference voltage components are obtained by performing common-mode analysis based on the positive and negative channel voltages, and differential-mode interference voltage components are obtained by performing differential-mode interference analysis. Based on the amplitudes of the common-mode interference voltage components and the differential-mode interference voltage components, the common-mode dominant frequency band and the differential-mode dominant frequency band in conducted interference are determined to locate the operating conditions that cause conducted interference.

[0007] In conjunction with the first aspect, the steps for obtaining the background noise spectrum by performing a background noise test in an electromagnetic compatibility anechoic chamber before powering on the electrically driven system under test include: Connect the test equipment based on the standard test configuration and power on the auxiliary equipment in the electromagnetic compatibility anechoic chamber; A full scan was performed across the entire test frequency band, and the initial background noise spectrum was measured and recorded. The initial background noise spectrum is compared with the standard limit line to determine whether the background noise spectrum is lower than the standard limit by a preset margin across the entire frequency band. If so, record this final background noise spectrum as a qualified test benchmark.

[0008] In conjunction with the first aspect, after determining whether the background noise spectrum is below the standard limit by a preset margin across the entire frequency band, the method further includes: If not, after performing a systematic investigation, re-perform the background noise test until the obtained updated background noise spectrum is lower than the standard limit by a preset margin across the entire frequency band; the systematic investigation should include at least: checking and tightening the connections and grounding of the test system, and sequentially shutting down potential interference source devices in the electromagnetic compatibility anechoic chamber. In conjunction with the first aspect, the steps of performing a conduction voltage method test on the electric drive system under test after power-on, and measuring the positive channel voltage and negative channel voltage respectively, include: The electric drive system under test is placed in the reference operating state, and the connection between the electric drive system under test, the line impedance stabilization network, and the load system is established based on the electromagnetic compatibility test standard. Under the reference operating conditions, the voltage between the measurement port of the positive channel of the line impedance stabilization network and the reference ground is measured using an electromagnetic interference receiver, and the voltage spectrum of the positive channel is scanned and recorded in the entire frequency band; at the same time, the voltage between the measurement port of the negative channel of the line impedance stabilization network and the reference ground is measured using an electromagnetic interference receiver, and the voltage spectrum of the negative channel is scanned and recorded in the entire frequency band. The positive and negative channel voltage spectra were compared with qualified test benchmarks to confirm that all out-of-range frequency bands originated from the electric drive system under test, thus obtaining valid positive and negative channel voltage data.

[0009] In conjunction with the first aspect, the steps of performing common-mode analysis based on the positive and negative channel voltages to obtain the common-mode interference voltage components, and simultaneously performing differential-mode interference analysis to obtain the differential-mode interference voltage components, include: Calculate the arithmetic mean of the positive channel voltage and the negative channel voltage to obtain the common-mode interference voltage component; The differential-mode interference voltage component is obtained by multiplying the difference between the positive and negative channel voltages by a specified value. Extract the voltage amplitude data corresponding to each test frequency point from the voltage spectrum of the positive and negative channels; For each test frequency, calculate the common-mode interference voltage component and the differential-mode interference voltage component at that test frequency. The common-mode interference voltage component values ​​and differential-mode interference voltage component values ​​at each test frequency point are combined to form a complete common-mode interference voltage component spectrum and differential-mode interference voltage component spectrum.

[0010] In conjunction with the first aspect, the steps of determining the common-mode dominant frequency band and differential-mode dominant frequency band in conducted interference based on the amplitudes of the common-mode interference voltage component and the differential-mode interference voltage component, in order to locate the operating conditions that cause conducted interference, include: The specified operating conditions of the electric drive system under test are changed one by one in sequence. After each change of a single variable, the conducted voltage method test and common-differential mode analysis are re-executed to obtain the common-mode and differential-mode interference spectrum under the single operating condition. The interference spectrum under the current single operating condition is compared with the interference spectrum under the reference operating condition to identify the specified frequency band that has changed significantly due to the change in the operating condition. The significant changes include a significant increase or decrease in the amplitude of the specified frequency band or the appearance of new interference frequency points. Based on the identified specified frequency bands that have undergone significant changes, the system correlates them with the currently set single operating conditions to determine that the operating condition is the source of conducted interference in this part of the frequency band. Establish and record a mapping table between the operating conditions of the electric drive system under test and the frequency bands of conducted interference, and locate the source of the operating conditions that cause conducted interference.

[0011] Following the first aspect, after determining the common-mode dominant frequency band and differential-mode dominant frequency band in conducted interference based on the amplitudes of the common-mode interference voltage component and the differential-mode interference voltage component to locate the source of the operating condition causing conducted interference, the method further includes: Based on the identified operating conditions and their corresponding common-mode or differential-mode dominant frequency bands, rectification is carried out, including filter rectification and source rectification.

[0012] In conjunction with the first aspect, based on the identified operating condition source and its corresponding common-mode dominant frequency band or differential-mode dominant frequency band, the following steps are taken to rectify the filter: If the interference is mainly dominated by common-mode components, implement common-mode suppression measures, including adjusting common-mode inductor parameters, optimizing Y capacitor layout, or improving equipment grounding; If the interference is mainly dominated by differential mode components, differential mode suppression measures should be implemented, including adjusting the differential mode inductor parameters, optimizing the X capacitor parameters, or improving the high-frequency characteristics of the DC bus capacitor.

[0013] In conjunction with the first aspect, after performing filter rectification steps based on the identified operating condition source and its corresponding common-mode dominant frequency band or differential-mode dominant frequency band, the process also includes: Re-perform the conducted voltage method test to verify whether the interference spectrum after rectification meets the standard requirements; If so, the rectification is complete; If not, implement source rectification until the standard requirements are met.

[0014] In conjunction with the first aspect, the steps for implementing source rectification include: Based on the identified operating conditions that cause conducted interference, the circuit source of electromagnetic interference is determined, including power switching device circuits or motor drive circuits. When the operating conditions are related to power switching devices, the adjustments implemented include at least one of optimizing the gate drive resistance of the switching devices, adjusting the switching frequency, or changing the PWM modulation strategy. When the operating conditions are related to the motor drive, the adjustments implemented include at least one of correcting the motor's current loop control parameters, optimizing the field weakening control strategy, or improving the dead time compensation effect. Physical layout optimization of the identified circuit sources includes at least one of the following: shortening high-frequency loop paths, reducing parasitic inductance of power loops, or strengthening the shielding and grounding of key nodes. After completing the source rectification, the conducted voltage method test was re-executed to verify the suppression effect of the source rectification on the common-mode dominant frequency band and the differential-mode dominant frequency band.

[0015] The embodiments of the present invention bring the following beneficial effects: This application provides an interference localization method based on the conducted voltage method, which is used to systematically locate conducted voltage interference in an electric drive system under test. The method includes: in an electromagnetic compatibility anechoic chamber, performing a background noise test before powering on the electric drive system under test to obtain the background noise spectrum; if the background noise spectrum is lower than the standard limit by a preset margin in the entire test frequency band, performing a conducted voltage method test after powering on the electric drive system under test, and measuring the positive channel voltage and the negative channel voltage respectively; performing common-mode analysis based on the positive channel voltage and the negative channel voltage to obtain the common-mode interference voltage component, and simultaneously performing differential-mode interference analysis to obtain the differential-mode interference voltage component; determining the common-mode dominant frequency band and the differential-mode dominant frequency band in the conducted interference based on the amplitude of the common-mode interference voltage component and the differential-mode interference voltage component, so as to locate the operating condition source that causes the conducted interference.

[0016] The method in this application ensures that all subsequent test data truly reflect the characteristics of the device under test by introducing rigorous background noise verification, eliminating environmental variable interference. Combined with the quantitative separation of common-mode and differential-mode interference, it changes the traditional positioning mode that relies on experience and guesswork, and can accurately identify the dominant component of the interference (common-mode or differential-mode) and its corresponding specific frequency band, avoiding misjudgment from the root cause, thereby improving the efficiency and accuracy of fault location.

[0017] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description, claims and drawings.

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the interference localization method based on the conductive voltage method provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the electronic device structure provided in an embodiment of the present invention.

[0021] Figure label: 130 - Processor, 131 - Memory, 132 - Bus, 133 - Communication interface. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] To facilitate understanding of this embodiment, the technical terms used in this application will be briefly introduced below.

[0024] EMC (Electromagnetic Compatibility) refers to the ability of electronic devices or systems to function normally together in a common electromagnetic environment without causing unacceptable electromagnetic interference to any other devices in that environment. For electric drive systems in new energy vehicles, conducted emissions are a core challenge in EMC testing, especially the conducted voltage method (CEV). This method measures the conducted interference voltage generated by the electric drive system to the external power grid through the power line. Because electric drives are high-frequency, high-power switching devices, the electromagnetic noise they generate is extremely complex, making CEV testing difficult to pass and the rectification process highly challenging.

[0025] Conducted emission (CE) refers to the phenomenon where electromagnetic interference energy generated by a device or system propagates outward through conductors (such as power lines, signal lines, control lines, etc.) as conduction paths.

[0026] RE (Radiated Emission) refers to the phenomenon where electromagnetic interference energy generated by a device or system is radiated outward through space in the form of electromagnetic waves.

[0027] After introducing the technical terms used in this application, the application scenarios and design concepts of the embodiments of this application will be briefly described below.

[0028] With the intelligent development of electric drive systems in new energy vehicles, electromagnetic compatibility (EMC) requirements are becoming increasingly stringent. Among these, the conducted voltage method (CEV) test, with its numerous dependent variables and complex interference paths, has become a major challenge for achieving EMC compliance in electric drive systems. Currently, the industry generally relies on trial and error to locate and rectify CEV problems, which involves blindly speculating on interference sources based on test results and then repeatedly adjusting and verifying them. This method lacks precise differentiation between common-mode and differential-mode interference and fails to systematically investigate the impact of test environment and operating condition variables, leading to inaccurate location, haphazard rectification, and significant time and cost wasted, severely restricting product development efficiency and market competitiveness.

[0029] Based on this, this application provides an interference location method using the conductive voltage method to improve the efficiency and accuracy of fault location in electric drive systems.

[0030] Example 1 This application provides a method for locating interference using the conducted voltage method, which is used to systematically locate conducted voltage interference in an electric drive system under test; combined with Figure 1 As shown, the method includes: S110, in an electromagnetic compatibility anechoic chamber, performs background noise testing before powering on the electric drive system under test to obtain the background noise spectrum.

[0031] S120. If the background noise spectrum is lower than the standard limit by a preset margin in the entire test frequency band, the conducted voltage method test is performed after the electric drive system under test is powered on, and the positive channel voltage and negative channel voltage are measured respectively. S130 performs common-mode interference voltage component analysis based on positive and negative channel voltages, and performs differential-mode interference analysis to obtain differential-mode interference voltage component.

[0032] S140: Based on the amplitudes of the common-mode interference voltage component and the differential-mode interference voltage component, determine the common-mode dominant frequency band and the differential-mode dominant frequency band in the conducted interference, so as to locate the operating conditions that cause the conducted interference.

[0033] This application ensures that all subsequent test data truly reflect the characteristics of the device under test by introducing rigorous background noise verification, eliminating environmental variable interference. Combined with the quantitative separation of common-mode and differential-mode interference, it changes the traditional positioning mode that relies on experience and guesswork, and can accurately identify the dominant component of the interference (common-mode or differential-mode) and its corresponding specific frequency band, avoiding misjudgment from the root cause, thereby improving the efficiency and accuracy of fault location.

[0034] Understandably, the purpose of the two stages before step S110, including EMC sample preparation and EMC test environment setup, is to fix all test variables and ensure that subsequent positioning operations are based on a stable and reproducible test platform, thereby ensuring the validity and comparability of all test data. EMC prototype preparation is used to ensure the consistency and reliability of the state of the test object and its associated systems. Specifically, this includes: preparing prototypes, host computers, wiring harnesses, rectification materials, and tooling in advance; and setting up the EMC test environment, including: test equipment (such as a Line Impedance Stabilization Network (LISN), an Electromagnetic Interference (EMI) receiver, a current probe, a power analyzer, etc.), CEV setup (referring to the physical connection and system integration of the LISN, prototype, load (such as a dynamometer), and measuring instruments in an anechoic chamber according to test standards. This process must ensure reliable connections, low grounding impedance, and strict adherence to the layout and distance specified in the standards), and EMC test condition debugging (referring to setting and verifying a series of typical operating points in the prototype host computer before formal testing. These operating conditions typically cover the core operating range of the electric drive system, such as: constant speed operation at different speeds, load loading at different torques, switching under different modulation strategies (such as SVPWM, DPWM), and changes in switching frequency).

[0035] In conjunction with the first aspect, step S110 includes: S111 connects to the test equipment based on the standard test configuration and powers on the auxiliary equipment in the electromagnetic compatibility anechoic chamber.

[0036] The standard test configuration refers to the test setup strictly following international or EMC standards (such as CISPR 25, GB / T 18655). This includes using a line impedance stabilization network (LISN) to power the electric drive system and couple its radio frequency interference voltage to the measuring equipment, using a standard-compliant electromagnetic interference receiver, and connecting all equipment to the anechoic chamber reference ground plane.

[0037] Auxiliary equipment refers to the equipment necessary to maintain the operation and testing functions of the darkroom, such as lighting systems, cooling systems for the equipment under test, and signal simulators.

[0038] Before powering on the device under test (DUT), all auxiliary devices are powered on first to include them as part of the background noise. This ensures that the measured background noise is the "most realistic" test environment background, encompassing the noise from all fixed auxiliary devices, thus guaranteeing the validity and comparability of subsequent test data.

[0039] S112 scans the entire test frequency band, measuring and recording the initial background noise spectrum.

[0040] Background noise spectrum refers to the set of inherent noise signals of the test system itself and the test environment within a specified frequency band when the device under test is not connected or started, presented in the form of an amplitude-frequency curve.

[0041] By scanning across the entire frequency band, a baseline of environmental noise can be obtained. Any subsequent signals exceeding this baseline can be attributed to the device under test. Thus, this step quantifies and records the electromagnetic environment, providing an objective data basis for subsequent judgments.

[0042] S113, compare the initial background noise spectrum with the standard limit line, and determine whether the background noise spectrum is lower than the standard limit by a preset margin across the entire frequency band.

[0043] A preset margin is a self-defined internal requirement that is more stringent than the standard limit. For example, the standard requires background noise to be 6 dB below the limit, while this embodiment may require it to be 10 dB or more below the limit.

[0044] Understandably, simply being "below the limit" may not be enough to eliminate weak and unstable environmental interference. Therefore, this embodiment sets a more stringent "preset margin" and a clean, low-noise test environment to ensure that any interference exceeding the standard measured must come from the device under test, avoiding misjudgments and disputes caused by environmental noise fluctuations and improving the reliability of subsequent test data.

[0045] S114; If so, record this final background noise spectrum as a qualified test benchmark.

[0046] The test benchmark refers to a verified and qualified background noise spectrum file that serves as a reference for subsequent test data comparison.

[0047] In conjunction with the first aspect, after step S113, the following also includes: If not, after performing a systematic investigation, retest the background noise until the updated background noise spectrum obtained is lower than the standard limit by a preset margin across the entire frequency band; the systematic investigation includes at least: checking and tightening the connections and grounding of the test system, and sequentially shutting down potential interference source devices in the electromagnetic compatibility anechoic chamber. Understandably, when the background noise spectrum fails to meet the preset margin requirements, a multi-layered diagnostic and troubleshooting mechanism will be activated. This mechanism constructs an orderly troubleshooting path from basic connections to complex systems based on the probability distribution of electromagnetic interference generation: First, a physical layer check is performed to ensure that all RF connectors (such as BNC and N-type interfaces) are secure and not loose, and to confirm that the grounding wires of all devices (especially LISNs and receivers) are firmly connected and that the grounding impedance is sufficiently low, eliminating the most common contact problems.

[0048] Subsequently, intelligent interference source isolation is implemented. Potential interference sources are precisely located by sequentially shutting down various auxiliary devices in the darkroom and monitoring spectrum changes in real time. Examples include: turning off LED lights or their drivers; turning off surveillance cameras; turning off chargers or adapters at wall sockets; and temporarily shutting down the ventilation system. Each time a device is shut down, the background noise is immediately rescanned to observe whether the noise in the exceeding frequency bands significantly decreases or disappears. If the noise disappears after a device is shut down, that device can be identified as the internal interference source.

[0049] Finally, the reliability of the testing system itself is verified through the equipment self-test process. This structured troubleshooting method achieves a complete diagnostic loop from "identifying the problem" to "locating the root cause," ensuring that the testing environment is in optimal condition.

[0050] By establishing this mandatory environmental purification process, the accuracy and authority of subsequent test data are fundamentally guaranteed, and overall testing efficiency is significantly improved. In practical applications, this method reduces test repetition rates caused by environmental interference and provides a reliable data foundation for subsequent precise rectification, becoming an important technical guarantee for achieving rapid EMC compliance.

[0051] In conjunction with the first aspect, step S120 includes: S121, the electric drive system under test is placed in the reference operating state, and the connection between the electric drive system under test, the line impedance stabilization network, and the load system is established based on the electromagnetic compatibility test standard.

[0052] A baseline operating state refers to a predefined, stable, and repeatable initial operating point. Typically, a medium speed and light load condition is chosen to allow the system to start operating in a standard and predictable mode, establishing a unified comparison benchmark for subsequent variable comparisons.

[0053] Line Impedance Stabilized Network (LISN) is a standard test device. First, it provides DC power to the electric drive system. Second, it provides a stable, standard impedance to the measurement equipment in the radio frequency range and couples the conducted interference voltage generated by the electric drive system to the measurement receiver, while preventing noise from the power grid side from entering the test system.

[0054] Load system: usually refers to dynamometer or electronic load, used to absorb the power output of electric drive system and simulate the load conditions when it is working in real time.

[0055] Starting the test under baseline conditions ensures consistent initial data conditions. Strictly adhering to standard wiring impedance stabilization networks is fundamental to ensuring the accuracy, repeatability, and legal validity of measurement results. In this embodiment, the introduction of a wiring impedance stabilization network makes test results for the same product comparable across different laboratories and at different times.

[0056] S122, under reference operating conditions, use an electromagnetic interference receiver to measure the voltage between the measurement port of the positive channel of the line impedance stabilization network and the reference ground, and scan and record the voltage spectrum of the positive channel across the entire frequency band; simultaneously, use an electromagnetic interference receiver to measure the voltage between the measurement port of the negative channel of the line impedance stabilization network and the reference ground, and scan and record the voltage spectrum of the negative channel across the entire frequency band.

[0057] An electromagnetic interference (EMI) receiver is a precision measuring instrument used to accurately measure the amplitude of interference signals within a specified frequency band. Its function is similar to that of a high-performance frequency-selective voltmeter.

[0058] The positive channel voltage spectrum refers to the graph of the interference voltage relative to the reference ground as a function of frequency, obtained from the positive measurement port of the LISN. Conversely, the negative channel voltage spectrum refers to the graph of the interference voltage relative to the reference ground as a function of frequency, obtained from the negative measurement port of the LISN.

[0059] In this step, the interference voltage on the positive and negative wires is captured simultaneously but separately, ensuring that the positive and negative data are acquired under exactly the same operating conditions at any given time. This provides spatiotemporally consistent raw data pairs for subsequent accurate common-mode and differential-mode analysis, which is an important guarantee for avoiding analysis errors.

[0060] S123 compares the positive channel voltage spectrum and the negative channel voltage spectrum with the qualified test benchmark to confirm that all out-of-range frequency bands originate from the electric drive system under test, thereby obtaining valid positive channel voltage and negative channel voltage data.

[0061] A qualified test benchmark is the clean background noise spectrum recorded in step S114.

[0062] The frequency range exceeding the standard refers to the frequency range in which the measured interference voltage amplitude exceeds the limit specified in the applicable standard.

[0063] By superimposing and comparing the measurement results after the device is powered on with the background noise reference before power-on, it can be clearly determined that: A. All frequency bands exceeding the standard are indeed introduced by the device under test, rather than environmental noise. B. Even in frequency bands that do not exceed the standard, interference generated by the device itself but masked by background noise can be identified.

[0064] As can be seen, step S120 constitutes a rigorous data acquisition process from establishing a reference to synchronous acquisition and then to data verification, ensuring that the obtained raw voltage data is not only standardized (through LISN and reference state) and complete (containing both positive and negative information), but also real and valid (by comparing with background noise).

[0065] In conjunction with the first aspect, S130 includes: S131, calculate the arithmetic mean of the positive channel voltage and the negative channel voltage to obtain the common-mode interference voltage component.

[0066] The common-mode interference voltage component is equal to the arithmetic mean of the positive and negative channel voltages. From an electromagnetic compatibility (EMC) perspective, common-mode interference is an asymmetrical interference. Its noise current flows in the same direction and amplitude on both positive and negative conductors, with the ground or chassis serving as a common loop. The physical significance of calculating the arithmetic mean lies in its ability to extract the common voltage component relative to the reference ground, which is simultaneously superimposed on both conductors. In practice, this means that for each test frequency, the positive and negative voltage values ​​at that frequency are added together and then divided by 2 to obtain the common-mode component. This quantifies and isolates the common-mode noise, which is originally hidden in the mixed signal and is mainly harmful due to electromagnetic radiation and ground loops. This provides indispensable quantitative data for accurately determining the dominant frequency band of common-mode interference and implementing targeted common-mode suppression measures (such as selecting common-mode inductors and adjusting Y capacitors).

[0067] S132 calculates the product of the difference between the positive channel voltage and the negative channel voltage and the specified value to obtain the differential mode interference voltage component.

[0068] The differential-mode interference voltage component is defined as half the difference between the positive and negative channel voltages. Differential-mode interference is symmetrical in nature; its noise current has equal amplitude but opposite direction on both positive and negative conductors, and its loop is consistent with the normal power current loop. Calculating half the difference physically means extracting the differential voltage component flowing back and forth between the two conductors. This calculation effectively separates the high-frequency noise generated on the DC bus by the switching actions of the drive system itself (such as the rapid switching of IGBTs and MOSFETs). In this way, a pure differential-mode interference voltage value can be calculated at each frequency point, providing a precise data basis for subsequent identification of the dominant differential-mode frequency band and the implementation of targeted differential-mode filtering measures (such as optimizing the differential-mode inductor, selecting the X capacitor, and improving the high-frequency characteristics of the bus capacitor).

[0069] S133 extracts the voltage amplitude data corresponding to each test frequency point from the voltage spectrum of the positive channel and the voltage spectrum of the negative channel.

[0070] The preceding steps yielded two continuous spectral curves: the positive channel voltage spectrum and the negative channel voltage spectrum. However, computers cannot directly perform the aforementioned mathematical operations on continuous curves. Therefore, this step requires systematically extracting the positive and negative voltage amplitudes corresponding to each test frequency point (e.g., from 150kHz to 108MHz, in steps of the receiver's intermediate frequency bandwidth) from these two continuous spectra in a discretized manner. This process essentially involves the digital sampling and recording of the analog signal, forming a data list containing three dimensions: frequency, positive voltage, and negative voltage. This ensures that all subsequent mathematical operations are performed on precise, one-to-one corresponding discrete data points, guaranteeing the accuracy and repeatability of the analysis.

[0071] S134, for each test frequency point, calculate the common-mode interference voltage component value and the differential-mode interference voltage component value at that test frequency point.

[0072] The data list containing all frequency points generated in step S133 is traversed, and for each frequency point in the list, the calculation models defined in S131 and S132 are applied independently and in parallel. Specifically, for the i-th frequency point, its positive and negative voltage values ​​are retrieved from the data list, and then the common-mode voltage and differential-mode voltage values ​​for that frequency point are calculated respectively. The output results in two entirely new data sequences: one is a "common-mode voltage-frequency" sequence that purely describes common-mode interference, and the other is a "differential-mode voltage-frequency" sequence that purely describes differential-mode interference.

[0073] S135 combines the common-mode interference voltage component value and the differential-mode interference voltage component value of each test frequency point to form a complete common-mode interference voltage component spectrum and differential-mode interference voltage component spectrum.

[0074] The two discrete "common-mode voltage-frequency" and "differential-mode voltage-frequency" data sequences generated in step S134 are reconstructed and plotted into two complete and continuous spectrograms through plotting or data reconstruction: a common-mode interference voltage component spectrogram and a differential-mode interference voltage component spectrogram. These two spectrograms are no longer a mixture of the original signals, but rather decomposed diagnostic spectrograms with a single physical meaning. Engineers can interpret them like reading a... Figure 1 In this way, it is clear which frequency bands are dominated by common-mode interference (the common-mode spectrum amplitude is much higher than that of differential-mode interference) and which frequency bands are dominated by differential-mode interference. It is even possible to analyze the ratio of common-mode to differential-mode interference at a specified frequency point.

[0075] In conjunction with the first aspect, step S140 includes: S141, change the specified operating conditions of the electric drive system under test one by one in sequence. After each change of a single variable, re-execute the conducted voltage method test and common-differential mode analysis to obtain the common-mode and differential-mode interference spectrum under the single operating condition.

[0076] In step S141, the controlled variable method is used to sequentially and individually change the specified operating conditions of the electric drive system under test. These operating conditions are variables of its operating state, typically including switching frequency, modulation strategy (such as switching between SVPWM and DPWM), load torque, motor speed, etc. It is worth noting that the key is the single variable principle, that is, only one operating parameter is changed at a time, while all other conditions remain unchanged. After each single operating condition change, the complete process from conducted voltage method test (S120) to common-mode and differential-mode analysis (S130) must be re-executed to obtain the common-mode and differential-mode interference spectrum under the specified, clean operating condition.

[0077] In this way, by artificially creating a series of controllable and clearly defined experimental states, a clean and comparable set of data samples is prepared for subsequent observation of the response to electromagnetic interference.

[0078] S142, compare the interference spectrum under the current single operating condition with the interference spectrum under the reference operating condition, and identify the specified frequency band that has changed significantly due to the change in the operating condition, wherein the significant change includes a significant increase or decrease in the amplitude of the specified frequency band or the appearance of new interference frequency points.

[0079] The interference spectrum (including common-mode and differential-mode spectra) collected in step S141 under a single changing operating condition is precisely compared, frequency-to-frequency, with the interference spectrum under a predefined "baseline operating condition" (usually the initial stable state set in S121). The purpose is to identify and pinpoint designated frequency bands that have undergone "significant changes" due to the change in the current operating condition from the complex spectrum. In this embodiment, such "significant changes" are explicitly defined as three observable phenomena: 1) a significant increase in the amplitude of the designated frequency band (usually referring to a jump exceeding the measurement error range); 2) a significant decrease in the amplitude of the designated frequency band; 3) the appearance of new, reproducible interference frequencies in previously clean frequency bands. In this way, macroscopic spectral differences are transformed into a microscopic, specific list of problem frequency bands.

[0080] S143, based on the identified specified frequency band that has undergone significant changes, associate it with the currently set single operating condition to determine that the operating condition is the source of conducted interference in this part of the frequency band.

[0081] The specified frequency bands that have undergone significant changes, identified in S142, will be forcibly correlated with the single operating condition currently set in S141. The underlying logic is that since the system only introduces this one variable, any significant changes in the observed spectrum must be a direct or indirect result of this variable.

[0082] Therefore, it can be determined that the current operating conditions are the source of conducted interference in this specified frequency band. For example, if a new differential-mode interference peak is observed near an octave of the switching frequency when only the switching frequency is increased, it can be determined that the differential-mode interference originates from the increase in the switching frequency. This step represents a qualitative shift from "observing a change" to "attributing it to a variable," completing the initial location of the interference source.

[0083] S144, Establish and record the mapping relationship table between the operating conditions of the electric drive system under test and the frequency band of conducted interference, and complete the location of the operating condition source that causes conducted interference.

[0084] The "operating condition-interference frequency band" relationships established in the preceding steps (S141 to S143) are systematically organized and recorded to form a structured "operating condition-conducted interference frequency band mapping table." This table clearly lists different operating conditions (such as "switching frequency 150kHz," "load torque 200Nm") and the main interference frequency bands they are responsible for (such as "differential mode interference, frequency band 30-40MHz"). This completes the final identification of the operating condition source causing conducted interference, making the abstract interference problem concrete and manageable. It also serves as a transferable diagnostic knowledge base, providing the most direct input for subsequent targeted rectification (such as adjusting control parameters for the operating condition or designing filters for the frequency band), and providing valuable experience data for the design of similar products in the future, avoiding repeated trial and error costs.

[0085] In conjunction with the first aspect, after step S140, the following also includes: S150 performs filter rectification based on the identified operating condition source and its corresponding common-mode dominant frequency band or differential-mode dominant frequency band.

[0086] Understandably, after locating the source of the fault through steps S110-S140, the aforementioned precise diagnostic conclusions need to be transformed into efficient and accurate engineering solutions to abandon the traditional, blind trial-and-error rectification model. In this embodiment, the rectification actions are systematically divided into two complementary directions: filter rectification and source rectification.

[0087] Among them, filter rectification targets the propagation path of electromagnetic interference. Specifically, it involves inserting filters along the propagation path of interference noise to selectively attenuate noise at a specified frequency and prevent it from propagating outward. On the other hand, source rectification targets the source of electromagnetic interference. Specifically, it involves adjusting circuit parameters or control strategies to reduce the intensity of noise generation at the source, which is a more fundamental and optimized solution.

[0088] In conjunction with the first aspect, step S150 includes: S151 If the interference is mainly dominated by common-mode components, implement common-mode suppression measures, including adjusting the common-mode inductor parameters, optimizing the Y capacitor layout, or improving equipment grounding.

[0089] S152 If the interference is mainly dominated by differential mode components, differential mode suppression measures are implemented, including adjusting the differential mode inductor parameters, optimizing the X capacitor parameters, or improving the high-frequency characteristics of the DC bus capacitor.

[0090] Based on the interference dominance mode determined by S140, targeted measures are taken. If the problem frequency band is identified as common-mode dominant, the focus is on adjusting common-mode filtering components, such as increasing the common-mode inductance, optimizing the capacitance value and grounding position of the Y capacitor (line-to-ground capacitor). If the problem frequency band is identified as differential-mode dominant, the focus is on adjusting differential-mode filtering components, such as increasing the differential-mode inductance, optimizing the capacitance value or parallel structure of the X capacitor (line-to-line capacitor), and improving the high-frequency decoupling performance of the DC bus capacitor.

[0091] In conjunction with the first aspect, step S150 includes: S151 If the interference is mainly dominated by common-mode components, implement common-mode suppression measures, including adjusting the common-mode inductor parameters, optimizing the Y capacitor layout, or improving equipment grounding.

[0092] S152 If the interference is mainly dominated by differential mode components, differential mode suppression measures are implemented, including adjusting the differential mode inductor parameters, optimizing the X capacitor parameters, or improving the high-frequency characteristics of the DC bus capacitor.

[0093] Step S150 involves specific engineering countermeasures for the frequency band identified as being dominated by common-mode interference. The fundamental principle is to construct a filter network that presents high impedance to common-mode noise or provides a low-impedance bypass path for common-mode noise, thereby preventing its propagation along the conductor.

[0094] The working principle of adjusting common-mode inductor parameters involves two coils wound in opposite directions on a single magnetic core. For common-mode current (in the same direction), the magnetic fluxes superimpose, resulting in a large inductance and high inductive reactance, thus blocking high-frequency common-mode noise. For differential-mode current (in opposite directions), the magnetic fluxes cancel each other out, resulting in a small inductance that does not affect normal power transmission. According to the inductive reactance formula, increasing the inductive reactance value can improve its impedance in the specified problematic frequency band, thereby enhancing the attenuation effect.

[0095] The working principle of optimizing Y-capacitor placement is that the Y-capacitor is connected between the power line (positive or negative) and ground (equipment casing, reference ground). It provides a low-impedance capacitive path for common-mode current to return to the noise source, causing it to be "short-circuited" and bypassed by the capacitor, instead of flowing to the LISN and being measured. Specifically, based on the problem frequency band, select an appropriate capacitance value (the larger the capacitance value, the better the bypass effect for low-frequency noise); mount the Y-capacitor as close as possible to the noise source (such as the power module), and connect its ground pin to the low-impedance reference ground with the shortest and widest path. Lead inductance will severely degrade the high-frequency performance of the Y-capacitor, so the core of optimization lies in minimizing parasitic parameters.

[0096] Understandably, a low-impedance, low-inductive grounding system is fundamental for the effective operation of the Y capacitor and provides a smooth path for common-mode current discharge. Poor grounding prevents effective bypass of common-mode current, drastically reducing the overall effectiveness of the common-mode filter. This can be addressed by using metal spring fingers and conductive pads to ensure good contact between the shield and the ground plane, and by using wide, short copper strips or braided wire as the grounding wire. The effect is to establish a reliable, low-impedance return path for common-mode noise, ensuring the filtering measures function effectively.

[0097] In step S152, for the frequency band identified as dominated by differential mode interference, barriers are placed or bypasses are provided in the path of the noise flowing between the positive and negative poles.

[0098] The differential-mode inductors consist of two independent inductors connected in series in the positive and negative circuits, respectively. They exhibit inductive reactance to differential-mode current (i.e., line-to-line current), thus attenuating high-frequency differential-mode noise. Increasing the differential-mode inductance can improve the attenuation of differential-mode noise in the problematic frequency band. Because its magnetic circuit is open, care must be taken to prevent saturation; therefore, magnetic powder core materials are typically used.

[0099] The X capacitor is directly connected between the positive and negative terminals. It provides a low-impedance capacitive bypass path for differential-mode noise, allowing it to be discharged near its source and not conducted to the grid. "Optimization parameters" mainly refer to selecting appropriate capacitance values. Larger X capacitors have better filtering effects on low-frequency differential-mode noise, but they will increase size, cost, and standby power consumption. This measure needs to be precisely selected based on the problem frequency band and space.

[0100] The differential-mode noise of an electric drive system mainly originates from the high-speed switching action of power switching devices (such as IGBTs), which generates high-frequency ripple current on the DC bus. An ideal DC bus capacitor should provide a localized, low-impedance energy storage and discharge path for this high-frequency current. Ordinary electrolytic capacitors exhibit significant parasitic inductance (ESL) at high frequencies, resulting in high impedance and failure. Therefore, measures to improve high-frequency characteristics include: High-frequency film capacitors or ceramic capacitors: These capacitors have extremely low ESL, providing a truly low-impedance path for high-frequency noise.

[0101] Optimize capacitor layout and connections: place them as close as possible to the power switch and connect them using low-inductance busbars to minimize parasitic inductance in the circuit. This measure suppresses differential mode from the closest point to the noise source and is one of the most effective means of solving high-frequency differential mode problems.

[0102] In conjunction with the first aspect, after step S150, the following also includes: S160, re-execute the conducted voltage method test to verify whether the interference spectrum after rectification meets the standard requirements.

[0103] If yes, proceed to step S170; otherwise, proceed to step S180.

[0104] S170, rectification completed.

[0105] S180, implement source rectification until the standard requirements are met.

[0106] Understandably, after completing the targeted filter rectification measures, this method enters the crucial verification and closed-loop optimization stage. Step S160 requires re-performing the conducted voltage method test. Its core purpose is to objectively evaluate the actual effect of the rectification measures, compare the rectified interference spectrum with the standard limit, and form a decision point based on measured data: if the verification passes (S170), it signifies that the rectification process for the specified problem is successfully completed; if the verification fails (S180), it indicates that relying solely on filter rectification may not be sufficient to fundamentally solve the problem, and a deeper level of "source rectification" must be initiated. That is, based on the previously identified operating conditions, the parameters of the noise generation source (such as the switching characteristics of power devices, control strategy parameters, etc.) are directly adjusted or the design is optimized, and iterative testing and verification are carried out until the interference spectrum fully meets the standard requirements. This forms a rigorous engineering closed loop with self-correction capabilities, fundamentally ensuring the final effectiveness and reliability of the rectification, and eliminating the repeated trial and error and resource waste common in traditional methods.

[0107] In conjunction with the first aspect, the steps in step S180 for implementing source rectification include: S181, based on the identified source of the conducting interference, determine the circuit source that generates the electromagnetic interference, including the power switching device circuit or the motor drive circuit.

[0108] By analyzing the identified sources of operating conditions, the specific circuit sources that generate electromagnetic interference can be accurately identified. These mainly include power switching device circuits that carry high-frequency switching currents (such as IGBT / MOSFET and their snubber circuits) and motor drive circuits that involve motor control algorithms, so as to correlate macroscopic operating conditions with microscopic circuit functional modules.

[0109] S182, when the operating condition is related to the power switching device, the adjustments implemented include at least one of optimizing the gate drive resistance of the switching device, adjusting the switching frequency, or changing the PWM modulation strategy.

[0110] When the source of interference is directly related to the power switching device, suppression will be implemented from the noise generation mechanism through hardware and software means such as optimizing the gate drive resistor to control the voltage and current change rate of the switching transient, adjusting the switching frequency to avoid the resonance point or disperse the harmonic energy, or changing the PWM modulation strategy (such as switching from continuous modulation to discontinuous modulation) to reshape the harmonic spectrum.

[0111] S183, when the operating condition is related to the motor drive, the adjustments implemented include at least one of correcting the motor's current loop control parameters, optimizing the field weakening control strategy, or improving the dead time compensation effect.

[0112] If the problem is traced back to the motor drive circuit, the rectification should focus on the control level. This can be achieved by modifying the current loop control parameters (such as adjusting the PID gain) to improve the current tracking accuracy and stability, optimizing the field weakening control strategy to maintain waveform quality in the high-speed region, or finely calibrating the dead-time compensation time to eliminate voltage distortion caused by switching delay, thereby reducing the generation of interference from the source of control.

[0113] S184, perform physical layout optimization on the identified circuit source, including shortening the high-frequency loop path, reducing the parasitic inductance of the power loop, or strengthening the shielding and grounding of key nodes, at least one of these.

[0114] After identifying the circuit source of interference (such as a power switching circuit), noise is fundamentally suppressed by changing its physical structure, materials, and connections. This differs from "path remediation"—adding filters to "block" noise—in that it directly optimizes the characteristics of the noise source itself.

[0115] Specifically, according to the law of electromagnetic induction, a closed loop is equivalent to an antenna; the larger the loop area, the higher its efficiency in radiating and receiving electromagnetic noise. However, a large loop area also means higher loop self-inductance, which exacerbates voltage overshoot and ringing during switching. In PCB layout or busbar design, the positive and negative traces between the DC bus capacitor, switching devices (IGBT / MOSFET), and drive units should be made as close, parallel, and short as possible. By minimizing the area enclosed by the high-frequency switching current loop formed by the positive power supply, the switching transistor, and the negative power supply, the effectiveness of this loop as a radiating antenna and conducted noise source is greatly reduced. Simultaneously, voltage spikes and high-frequency ringing caused by loop inductance are reduced, thereby directly lowering differential-mode interference.

[0116] Parasitic inductance in power circuits can also be reduced by using multilayer busbars, selecting capacitors with low ESL (equivalent series inductance), and increasing parallel paths. The shielding and grounding of critical nodes can also be enhanced by using a metal shield to cover high-frequency noise sources (such as switching transistors and drive circuits) and by making low-impedance, multi-point good connections between the shield and the system's reference ground (such as the chassis).

[0117] It is understandable that the root cause of electromagnetic interference can be addressed by minimizing the antenna effect (shortening the loop), suppressing the intensity of the noise source (reducing parasitic inductance), and controlling the noise path (shielding and grounding).

[0118] S185, after completing the source rectification, the conducted voltage method test was re-executed to verify the suppression effect of the source rectification on the common-mode dominant frequency band and the differential-mode dominant frequency band.

[0119] The new conducted voltage method test was used to quantitatively evaluate the dominant frequency bands of common mode and differential mode, verifying the actual suppression effect of the aforementioned source rectification measures.

[0120] Understandably, if the suppression effect is not satisfactory, step S180 will be repeated for continuous verification, feedback, and adjustment. Preferably, the number of rectification attempts is preset. If the requirements are still not met after the preset number of rectification attempts, feedback should be given to the engineer or the process should switch to step S160 for filter rectification. This can be selected according to actual needs and is not limited here.

[0121] Thirdly, embodiments of this application provide an electronic device, combined with Figure 2 As shown, the electronic device includes a memory 131 and a processor 130. The memory 131 stores a computer program, and the processor 130 runs the computer program to make the electronic device perform the above-described method.

[0122] Furthermore, combined Figure 2The electronic device shown also includes a bus 132 and a communication interface 133, with the processor 130, the communication interface 133 and the memory 131 connected via the bus 132.

[0123] The memory 131 may include high-speed random access memory (RAM) and may also include non-volatile memory, such as at least one disk storage device. Communication between this system network element and at least one other network element is achieved through at least one communication interface 133 (which can be wired or wireless), such as the Internet, wide area network, local area network, metropolitan area network, etc. The bus 132 may be an ISA bus, PCI bus, or EISA bus, etc. The bus can be divided into address bus, data bus, control bus, etc. For ease of representation, Figure 2 The symbol is represented by a single double-headed arrow, but this does not mean that there is only one bus or one type of bus.

[0124] Processor 130 may be an integrated circuit chip with signal processing capabilities. In implementation, each step of the above method can be completed by the integrated logic circuitry in the hardware of processor 130 or by instructions in software form. Processor 130 may be a general-purpose processor, including a Central Processing Unit (CPU), a Network Processor (NP), etc.; it may also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this invention. The general-purpose processor may be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of this invention can be directly manifested as execution by a hardware decoding processor, or execution by a combination of hardware and software modules in the decoding processor. The software module can reside in a mature storage medium in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, or registers. This storage medium is located in memory 131, and processor 130 reads the information in memory 131 and, in conjunction with its hardware, completes the steps of the method described in the foregoing embodiments.

[0125] Fourthly, embodiments of this application provide a readable storage medium storing computer program instructions, which are read and executed by a processor to perform the above-described method.

[0126] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system and apparatus described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0127] Furthermore, in the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0128] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0129] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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 the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0130] Finally, it should be noted that the above embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, 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 the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for locating interference using the conducted voltage method, characterized in that, The method is used to systematically locate conducted voltage method interference in the electric drive system under test; the method includes: In an electromagnetic compatibility anechoic chamber, a background noise test was performed on the electric drive system under test before it was powered on, and the background noise spectrum was obtained. If the background noise spectrum is lower than the standard limit by a preset margin in the entire test frequency band, the conducted voltage method test is performed after the electric drive system under test is powered on, and the positive channel voltage and negative channel voltage are measured respectively. Common-mode interference voltage components are obtained by performing common-mode analysis based on the positive channel voltage and the negative channel voltage, and differential-mode interference voltage components are obtained by performing differential-mode interference analysis. Based on the amplitudes of the common-mode interference voltage component and the differential-mode interference voltage component, the common-mode dominant frequency band and the differential-mode dominant frequency band in the conducted interference are determined to locate the operating conditions that cause the conducted interference.

2. The method according to claim 1, characterized in that, In an electromagnetic compatibility anechoic chamber, the steps for obtaining the background noise spectrum by performing a background noise test on the electrically driven system under test before powering on include: Connect the test equipment based on the standard test configuration and power on the auxiliary equipment in the electromagnetic compatibility anechoic chamber; A full scan was performed across the entire test frequency band, and the initial background noise spectrum was measured and recorded. The initial background noise spectrum is compared with the standard limit line to determine whether the background noise spectrum is lower than the standard limit by a preset margin across the entire frequency band. If so, record this final background noise spectrum as a qualified test benchmark.

3. The method according to claim 1, characterized in that, After determining whether the background noise spectrum is below the standard limit by a preset margin across the entire frequency band, the method further includes: If not, after performing a systematic investigation, the background noise test is repeated until the obtained updated background noise spectrum is lower than the standard limit by a preset margin across the entire frequency band; the systematic investigation includes at least: checking and tightening the connection and grounding of the test system, and sequentially shutting down potential interference source devices in the electromagnetic compatibility anechoic chamber.

4. The method according to claim 1, characterized in that, The steps of performing a conduction voltage method test on the electric drive system under test after power-on, and measuring the positive channel voltage and negative channel voltage respectively, include: The electric drive system under test is placed in a reference operating state, and the connection between the electric drive system under test, the line impedance stabilization network, and the load system is established based on the electromagnetic compatibility test standard. Under the aforementioned reference operating conditions, an electromagnetic interference receiver is used to measure the voltage between the measurement port of the positive channel of the line impedance stabilization network and the reference ground, and the voltage spectrum of the positive channel is scanned and recorded across the entire frequency band; simultaneously, the electromagnetic interference receiver is used to measure the voltage between the measurement port of the negative channel of the line impedance stabilization network and the reference ground, and the voltage spectrum of the negative channel is scanned and recorded across the entire frequency band. The positive channel voltage spectrum and negative channel voltage spectrum are compared with qualified test benchmarks to confirm that all out-of-range frequency bands originate from the electric drive system under test, thereby obtaining valid positive channel voltage and negative channel voltage data.

5. The method according to claim 1, characterized in that, The steps of performing common-mode analysis based on the positive channel voltage and the negative channel voltage to obtain the common-mode interference voltage component, and simultaneously performing differential-mode interference analysis to obtain the differential-mode interference voltage component, include: Calculate the arithmetic mean of the positive channel voltage and the negative channel voltage to obtain the common-mode interference voltage component; The differential-mode interference voltage component is obtained by multiplying the difference between the positive channel voltage and the negative channel voltage by a specified value. Extract the voltage amplitude data corresponding to each test frequency point from the positive channel voltage spectrum and the negative channel voltage spectrum; For each of the test frequencies, calculate the common-mode interference voltage component value and the differential-mode interference voltage component value at the test frequency. The common-mode interference voltage component value and the differential-mode interference voltage component value at each of the test frequency points are combined to form a complete common-mode interference voltage component spectrum and a differential-mode interference voltage component spectrum.

6. The method according to claim 1, characterized in that, The step of determining the common-mode dominant frequency band and the differential-mode dominant frequency band in conducted interference based on the amplitudes of the common-mode interference voltage component and the differential-mode interference voltage component, in order to locate the operating condition source causing conducted interference, includes: The specified operating conditions of the electric drive system under test are changed one by one in sequence. After each change of a single variable, the conducted voltage method test and common-differential mode analysis are re-executed to obtain the common-mode and differential-mode interference spectrum under a single operating condition. The interference spectrum under the current single operating condition is compared with the interference spectrum under the reference operating condition to identify the specified frequency band that has changed significantly due to the change in the operating condition. The significant change includes a significant increase or decrease in the amplitude of the specified frequency band or the appearance of new interference frequency points. Based on the identified specified frequency bands that have undergone significant changes, the system associates these bands with the currently set single operating conditions to determine that the operating condition is the source of conducted interference in this frequency band. Establish and record a mapping table between the operating conditions of the electric drive system under test and the frequency band of conducted interference, and complete the location of the operating conditions that cause conducted interference.

7. The method according to claim 1, characterized in that, After determining the common-mode dominant frequency band and differential-mode dominant frequency band in conducted interference based on the amplitudes of the common-mode interference voltage component and the differential-mode interference voltage component, in order to locate the operating condition source causing conducted interference, the method further includes: Based on the identified operating conditions and their corresponding common-mode or differential-mode dominant frequency bands, filter modifications are performed.

8. The method according to claim 7, characterized in that, Based on the identified operating condition source and its corresponding common-mode dominant frequency band or differential-mode dominant frequency band, the filter rectification steps include: If the interference is mainly dominated by common-mode components, implement common-mode suppression measures, including adjusting common-mode inductor parameters, optimizing Y capacitor layout, or improving equipment grounding; If the interference is mainly dominated by differential mode components, differential mode suppression measures should be implemented, including adjusting the differential mode inductor parameters, optimizing the X capacitor parameters, or improving the high-frequency characteristics of the DC bus capacitor.

9. The method according to claim 7, characterized in that, Based on the identified operating condition source and its corresponding common-mode dominant frequency band or differential-mode dominant frequency band, after performing the filter rectification steps, the following steps are also included: Re-perform the conducted voltage method test to verify whether the interference spectrum after rectification meets the standard requirements; If so, the rectification is complete; If not, implement source rectification until the standard requirements are met.

10. The method according to claim 9, characterized in that, The steps for implementing source rectification include: Based on the identified source of the conducted interference, the circuit source that generates the electromagnetic interference is determined, including a power switching device circuit or a motor drive circuit. When the operating condition is related to power switching devices, the adjustments implemented include at least one of optimizing the gate drive resistance of the switching devices, adjusting the switching frequency, or changing the PWM modulation strategy. When the operating condition is related to the motor drive, the adjustments implemented include at least one of correcting the motor's current loop control parameters, optimizing the field weakening control strategy, or improving the dead time compensation effect. Physical layout optimization of the identified circuit sources includes at least one of the following: shortening high-frequency loop paths, reducing parasitic inductance of power loops, or strengthening the shielding and grounding of key nodes. After completing the source rectification, the conducted voltage method test was re-executed to verify the suppression effect of the source rectification on the common-mode dominant frequency band and the differential-mode dominant frequency band.

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