Risk prediction method for high-voltage conducted emission electromagnetic interference of electric drive system

Abstract

The invention discloses a risk prediction method for high-voltage conducted emission electromagnetic interference of an electric drive system, and the method comprises the steps: injecting a double-pulse drive signal, and synchronously collecting the switching voltage waveform of an upper bridge switching tube and a lower bridge switching tube and the waveform of switching current flowing through an inductor through an oscilloscope; performing fast Fourier transform, and extracting conducted interference spectrum data; obtaining the comprehensive insertion loss of the filter to be evaluated, testing a conduction voltage method noise value, then retesting the conduction voltage method noise value, and calculating the comprehensive insertion loss; subtracting the obtained comprehensive insertion loss of the filter from the obtained conducted interference spectrum data, and outputting a conducted voltage method evaluation result; and comparing the output evaluation result with a target limit value standard, and if the evaluation result is lower than a limit value, determining that there is no EMC risk. According to the method, accurate EMC risk assessment is finally obtained through measurement analysis and calculation, the defects of other methods are overcome, the assessment result is more accurate, and the practicability is higher.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic compatibility testing technology, and in particular to a risk prediction method for high-voltage conducted electromagnetic interference in electric drive systems. Background Technology

[0002] As electric drive systems for new energy vehicles develop towards higher integration (such as three-in-one and multi-in-one systems), the switching actions of their high-voltage power devices (IGBT / SiC modules) generate high-frequency conducted electromagnetic interference (EMI). If this interference exceeds international standard limits (such as CISPR25), it will lead to the failure of vehicle EMC testing, causing system malfunctions or compatibility issues. Traditional EMC verification relies on post-integration field testing, but the cost and time required for rectification after the integration of electric drive systems are high. Therefore, there is an urgent need for a method that can predict EMI risks during the design phase.

[0003] The existing technology has the following shortcomings and problems:

[0004] 1. Verification lag:

[0005] Electromagnetic interference issues are usually only exposed through EMC laboratory testing after the prototype of the electric drive system is completed. By this time, the design has been finalized, and rectification requires readjusting the hardware layout or replacing the filter, which leads to extended development cycles and soaring costs.

[0006] 2. Lack of accurate forecasting tools:

[0007] Existing simulation tools (such as circuit model simulation) are unable to accurately simulate the actual spectral characteristics of high-frequency switching noise, and are affected by parasitic parameter modeling errors, resulting in large deviations between the predicted results and the actual measurements, thus failing to provide reliable guidance for design.

[0008] 3. System-level interference coupling complexity:

[0009] In all-in-one electric drive systems, the high integration of motors, controllers, and power supplies complicates interference paths. Traditional module-level testing cannot reflect the overall EMI characteristics of the system, while full-system testing lacks early feasibility.

[0010] 4. High cost of trial and error:

[0011] Relying on the iterative model of "design-prototype-test-rectification", each failure involves high-value components (such as SiC modules) and structural reconstruction, which seriously delays the product development schedule. Summary of the Invention

[0012] The purpose of this invention is to overcome the shortcomings of the existing technology. To achieve the above objective, a risk prediction method for high-voltage conducted electromagnetic interference in electric drive systems is adopted to solve the problems mentioned in the background technology.

[0013] A risk prediction method for high-voltage conducted electromagnetic interference in electric drive systems includes the following steps:

[0014] Step S1, Double Pulse Test Execution:

[0015] A dual-pulse drive signal is injected into the electric drive system under test, and the switching voltage waveforms of the upper bridge switch and the lower bridge switch and the switching current waveform flowing through the inductor are simultaneously acquired by an oscilloscope.

[0016] Step S2, Spectral Feature Analysis:

[0017] The acquired switching voltage waveforms are subjected to Fast Fourier Transform to extract conducted interference spectrum data;

[0018] Step S3: Obtaining filter insertion loss:

[0019] To obtain the overall insertion loss of the filter to be evaluated, the conducted voltage method noise value is tested on a sample without a filter. After the filter is installed, the conducted voltage method noise value is retested, and the overall insertion loss of the filter is calculated.

[0020] Step S4, Calculation of Interference Risk Value:

[0021] Subtract the filter integration insertion loss obtained in S3 from the conducted interference spectrum data obtained in S2, and output the conducted voltage method evaluation result.

[0022] Step S5, Risk Assessment:

[0023] The evaluation results output by S4 are compared with the target limit standard. If the evaluation results are lower than the limit, it is determined that there is no EMC risk.

[0024] As a further aspect of the present invention: in step S1, the upper bridge switch and the lower bridge switch are IGBT or SiC power devices, the inductor is a dual-pulse test-specific inductor, and the capacitor is a thin-film capacitor for an electric drive system.

[0025] As a further aspect of the present invention: the pulse width and interval time of the dual-pulse drive signal in step S1 are set according to the rated current and inductive load characteristics of the switch under test.

[0026] As a further aspect of the present invention: the frequency range of the FFT analysis in step S2 is 150kHz-108MHz.

[0027] As a further aspect of the present invention: the filter synthesis insertion loss in step S3 is obtained by a comparative measurement method.

[0028] As a further aspect of the present invention: the two conducted voltage noise values ​​in step S3 are obtained by measuring in an anechoic chamber according to the CISPR25 standard.

[0029] As a further aspect of the present invention: the conducted voltage method evaluation result output in step S4 is presented in the form of a spectrum diagram, with the horizontal axis representing frequency and the vertical axis representing noise interference intensity.

[0030] As a further aspect of the present invention: the error rate between the evaluation result output in step S4 and the final vehicle test result is less than 5 dB (before 30M).

[0031] Compared with the prior art, the present invention has the following technical advantages:

[0032] The above technical solution first acquires the voltage waveform of the switching transistor through a dual-pulse test, and obtains the conducted interference spectrum through FFT analysis. Then, the noise value of the unfiltered prototype and the noise value after adding the target filter are measured, and the filter's overall insertion loss is dynamically calculated. The insertion loss is subtracted from the interference spectrum to obtain the net interference value, which is finally compared with the limit standard to determine the EMC risk. The test data is dynamically corrected by measuring the filter insertion loss, and the evaluation results are compared with the limits required by the vehicle customer. Through measurement, analysis, and calculation, a more accurate EMC risk assessment result is obtained, making up for the shortcomings of other methods, resulting in a more accurate assessment and stronger practicality. Attached Figure Description

[0033] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings:

[0034] Figure 1 This is a schematic diagram illustrating the steps of the risk prediction method according to an embodiment of this application;

[0035] Figure 2 This is a schematic diagram of a switch test according to an embodiment of this application;

[0036] Figure 3 This is a switching voltage waveform diagram of the IGBT or SiC module in step S1 of an embodiment disclosed in this application;

[0037] Figure 4 This is an FFT analysis diagram of step S2 in the embodiment disclosed in this application;

[0038] Figure 5 This is a schematic diagram illustrating the evaluation results of an embodiment disclosed in this application;

[0039] Figure 6 This is a comparison chart of the evaluation results and actual test results of the embodiments disclosed in this application. Detailed Implementation

[0040] The technical solutions of the embodiments 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, and 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.

[0041] Please refer to Figure 1 and Figure 2 In this embodiment of the invention, a risk prediction method for high-voltage conducted electromagnetic interference in an electric drive system includes the following steps:

[0042] Step S1, Double Pulse Test Execution:

[0043] A dual-pulse drive signal is injected into the electric drive system under test, and the switching voltage waveforms of the upper bridge switch and the lower bridge switch and the switching current waveform flowing through the inductor are simultaneously acquired by an oscilloscope.

[0044] In this embodiment, the upper bridge switch and the lower bridge switch in step S1 are IGBT or SiC power devices, the inductor is a dual-pulse test-specific inductor, and the capacitor is a thin-film capacitor for the electric drive system.

[0045] In this embodiment, the pulse width and interval of the dual-pulse drive signal in step S1 are set according to the rated current and inductive load characteristics of the switch under test.

[0046] like Figure 2 As shown, where:

[0047] S1: Indicates the upper bridge IGBT or SiC switching transistor;

[0048] S2: Indicates the lower bridge IGBT or SiC switching transistor;

[0049] L: Indicates the inductor used for double pulse testing;

[0050] C: Indicates a thin-film capacitor used in an electric drive system;

[0051] Vge: Represents the injected dual-pulse drive signal;

[0052] Vce: Represents the switching voltage waveform captured by the oscilloscope;

[0053] Ic: Represents the switching current waveform captured by the oscilloscope;

[0054] like Figure 3 As shown in the figure, the switching voltage waveform of the IGBT or SiC module in step S1 is shown.

[0055] Step S2, Spectral Feature Analysis:

[0056] The acquired switching voltage waveforms are subjected to Fast Fourier Transform to extract conducted interference spectrum data;

[0057] In this embodiment, the frequency range of the FFT analysis in step S2 is 150kHz-108MHz.

[0058] like Figure 4 As shown, the diagram is an FFT analytical plot, in which... Figure 3 The test data is analyzed using FFT to obtain the results shown in the figure.

[0059] Step S3: Obtaining filter insertion loss:

[0060] To obtain the overall insertion loss of the filter to be evaluated, the conducted voltage method noise value is tested on a sample without a filter. After the filter is installed, the conducted voltage method noise value is retested, and the overall insertion loss of the filter is calculated.

[0061] In this embodiment, the filter insertion loss in step S3 is obtained by actual measurement comparison.

[0062] In this embodiment, the two conducted voltage method noise values ​​in step S3 are obtained by measuring in an anechoic chamber according to the CISPR25 standard.

[0063] Specifically, select the overall insertion loss of the filter to be used in the plan. This insertion loss can be obtained through the following method:

[0064] Select a known unfiltered prototype and test the conducted voltage method noise 1;

[0065] The planned filter was installed in the unfiltered prototype, and the noise level 2 of the conducted voltage method with the filter added was obtained by testing.

[0066] Subtracting the conducted voltage noise 1 from the conducted voltage noise 2 gives the overall insertion loss of the filter.

[0067] Step S4: Calculation of interference noise value:

[0068] Subtract the obtained filter insertion loss from the obtained conducted interference spectrum data to output the conducted voltage method evaluation result;

[0069] In this embodiment, the conducted voltage method evaluation results output in step S4 are presented in the form of a spectrum diagram, with the horizontal axis representing frequency and the vertical axis representing noise interference intensity.

[0070] In this embodiment, the error rate between the evaluation result output in step S4 and the final vehicle test result is less than 5dB before 30M.

[0071] Specifically, subtracting the combined insertion loss of the filter from step S3 from the result obtained in step S2 yields the evaluation result of the conducted voltage method, such as... Figure 5 As shown.

[0072] Step S5, Risk Assessment:

[0073] The output evaluation results are compared with the target limit standard. If the evaluation results are lower than the limit, it is determined that there is no EMC risk.

[0074] Specifically, comparing the results of step four with the required limits, the results meet the required limits, therefore a risk-free conclusion can be reached. For example... Figure 6 As shown in the figure, the comparison chart is between the evaluation results and the measured results.

[0075] Beneficial effects:

[0076] In the process of assessing the risk of electromagnetic interference from high-voltage conducted emissions in electric drive systems, through measurement, analysis, and calculation, the EMC risk is assessed more accurately, making up for the shortcomings of other methods. The assessment results are more accurate and more practical.

[0077] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is defined by the appended claims and their equivalents, all of which should be included within the scope of protection of the invention.

Claims

1. A risk prediction method for high-voltage conducted electromagnetic interference in electric drive systems, characterized in that, Includes the following steps: Step S1, Double Pulse Test Execution: A dual-pulse drive signal is injected into the electric drive system under test, and the switching voltage waveforms of the upper bridge switch and the lower bridge switch and the switching current waveform flowing through the inductor are simultaneously acquired by an oscilloscope. Step S2, Spectral Feature Analysis: The acquired switching voltage waveforms are subjected to Fast Fourier Transform to extract conducted interference spectrum data; Step S3: Obtaining filter insertion loss: To obtain the overall insertion loss of the filter to be evaluated, the conducted voltage method noise value is tested on a sample without a filter. After the filter is installed, the conducted voltage method noise value is retested, and the overall insertion loss of the filter is calculated. Step S4, Calculation of Interference Risk Value: Subtract the filter integration insertion loss obtained in S3 from the conducted interference spectrum data obtained in S2, and output the conducted voltage method evaluation result. Step S5, Risk Assessment: The evaluation results output by S4 are compared with the target limit standard. If the evaluation results are lower than the limit, it is determined that there is no EMC risk.

2. The risk prediction method for high-voltage conducted electromagnetic interference in electric drive systems according to claim 1, characterized in that, In step S1, the upper and lower bridge switching transistors are IGBTs or SiC power devices, the inductor is a dual-pulse test-specific inductor, and the capacitor is a thin-film capacitor for the electric drive system.

3. The risk prediction method for high-voltage conducted electromagnetic interference in electric drive systems according to claim 1, characterized in that, The pulse width and interval of the dual-pulse drive signal in step S1 are set according to the rated current and inductive load characteristics of the switch under test.

4. The risk prediction method for high-voltage conducted electromagnetic interference in electric drive systems according to claim 1, characterized in that, The frequency range of the FFT analysis in step S2 is 150kHz-108MHz.

5. The risk prediction method for high-voltage conducted electromagnetic interference in an electric drive system according to claim 1, characterized in that, The filter insertion loss in step S3 is obtained by actual measurement comparison.

6. The risk prediction method for high-voltage conducted electromagnetic interference in an electric drive system according to claim 5, characterized in that, The two conducted voltage method noise values ​​in step S3 were obtained by measuring in an anechoic chamber according to the CISPR25 standard.

7. The risk prediction method for high-voltage conducted electromagnetic interference in an electric drive system according to claim 1, characterized in that, The conducted voltage method evaluation results output in step S4 are presented in the form of a spectrum diagram, with the horizontal axis representing frequency and the vertical axis representing noise interference intensity.

8. A risk prediction method for high-voltage conducted electromagnetic interference in an electric drive system according to any one of claims 1-7, characterized in that, The error rate between the evaluation result output in step S4 and the final system installation test result is less than 5dB before 30M.

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