Radiation electromagnetic interference diagnosis method of power electronic device

Abstract

The invention discloses a radiation electromagnetic interference diagnosis method for a power electronic device, belongs to the field of power electronic electromagnetic compatibility, and aims to solve the problem of diagnosis of a radiation interference source, an oscilloscope is used for measuring a time domain waveform of a radiation electric field, analyzing a narrow band after band-pass filtering, and revealing circuit PWM (Pulse Width Modulation) modulation information embedded in radiation EMI (Electro-Magnetic Interference) through envelope demodulation. Determining a dominant interference source according to a known power electronic topology modulation strategy; aiming at the diagnosis problem of a radiation interference path, diagnosis of a radiation interference source dominant path is realized based on voltage and current detection, a guiding direction is deployed for an accurate suppression strategy of the dominant interference path, and meanwhile, a means is provided for revealing an EMI filtering failure mechanism. The radiation interference source and path diagnosis method provided by the invention can provide guidance for accurate suppression of radiation electromagnetic interference of a power electronic device.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic compatibility of power electronics, and more specifically, relates to a method for diagnosing radiated electromagnetic interference of a power electronic device. Background Art

[0002] In recent years, power electronic devices have been widely used in modern power systems, rail transit and consumer electronics. However, the inherent switching working mode of power electronic devices will cause serious electromagnetic interference problems, endangering the normal operation of surrounding electronic equipment or affecting the reliability and life of electronic systems. Before deployment, power electronic devices must pass strict EMC certification. Among them, radiated electromagnetic interference has a higher frequency band, a larger spatial range of influence, and more complex propagation paths and fields, making it more difficult to analyze and control radiated electromagnetic interference. In addition, the equipment and time costs required for testing radiated interference are higher. How to quickly diagnose and accurately suppress these radiated interferences has become a focus issue that needs to be urgently solved for power electronic devices. Summary of the invention

[0003] In view of the above defects or improvement needs of the prior art, the present invention provides a method for diagnosing radiated electromagnetic interference of a power electronic device, which can realize rapid and accurate diagnosis of the dominant interference source and dominant propagation path of radiated EMI.

[0004] To achieve the above object, according to a first aspect of the present invention, a method for diagnosing a radiation interference source of a power electronic device is provided, comprising:

[0005] S1, measure the radiated EMI time domain signal of the target power electronic device, perform FFT processing on it to obtain the corresponding EMI spectrum, and obtain the peak frequency f of the EMI spectrum PK ;

[0006] S2, in K·f PK The radiated EMI time domain signal is bandpass filtered for the bandpass width; wherein the value range of K is [0.05, 0.1];

[0007] S3, performing envelope demodulation and FFT processing on the radiated EMI time domain signal after bandpass filtering in sequence to obtain the switching frequency of the radiated interference source, and taking the converter in the target power electronic device that uses the switching frequency as a modulation parameter as its radiated interference source.

[0008] According to a second aspect of the present invention, a method for diagnosing a radiation interference propagation path of a power electronic device is provided, comprising:

[0009] A1, determine the radiation type of the cable connected to the radiation interference source of the target power electronic device; wherein the radiation type includes independent radiation and coupled radiation. If the cables are all independently connected to the load, the radiation type is independent radiation; if the cables are all connected to the load together with other cables, the radiation type is coupled radiation;

[0010] A2. Determine the radiation interference propagation path of the target power electronic device according to the radiation type of the antenna; wherein, if the radiation type of the cable is independent radiation, the cable with the largest radiation current is used as the radiation cable, and its path is used as the radiation interference propagation path; if the radiation type of the cable is coupled radiation, the cable with the largest radiation voltage is used as the radiation cable, and its path is used as the radiation interference propagation path.

[0011] According to a third aspect of the present invention, there is provided a radiation interference source diagnosis device for a power electronic device, comprising:

[0012] The first processing module is used to measure the radiated EMI time domain signal of the target power electronic device, perform FFT processing on it to obtain the corresponding EMI spectrum, and obtain the peak frequency f of the EMI spectrum. PK ;

[0013] The second processing module is used to PK The radiated EMI time domain signal is bandpass filtered for the bandpass width; wherein the value range of K is [0.05, 0.1];

[0014] The second processing module is used to perform envelope demodulation and FFT processing on the radiated EMI time domain signal after bandpass filtering in sequence to obtain the switching frequency of the radiation interference source, and use the converter in the target power electronic device that uses the switching frequency as the modulation parameter as its radiation interference source.

[0015] According to a fourth aspect of the present invention, there is provided a device for diagnosing a radiation interference propagation path of a power electronic device, comprising:

[0016] A judgment module, used to judge the radiation type of the cable connected to the radiation interference source of the target power electronic device; wherein the radiation type includes independent radiation and coupled radiation. If the cables are all independently connected to the load, the radiation type is independent radiation; if the cables are all connected to the load together with other cables, the radiation type is coupled radiation;

[0017] A processing module is used to determine the radiation interference propagation path of the target power electronic device according to the radiation type of the antenna; wherein, if the radiation type of the cable is independent radiation, the cable with the largest radiation current is used as the radiation cable, and its path is used as the radiation interference propagation path; if the radiation type of the cable is coupled radiation, the cable with the largest radiation voltage is used as the radiation cable, and its path is used as the radiation interference propagation path.

[0018] According to a fifth aspect of the present invention, there is provided an electronic device, comprising: a computer-readable storage medium and a processor;

[0019] The computer-readable storage medium is used to store executable instructions;

[0020] The processor is used to read the executable instructions stored in the computer-readable storage medium and execute the method as described in the first aspect or the second aspect.

[0021] According to a sixth aspect of the present invention, there is provided a computer-readable storage medium, wherein the computer-readable storage medium stores computer instructions for causing a processor to execute the method as described in the first aspect or the second aspect.

[0022] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0023] The radiation interference source diagnosis method of the power electronic device provided by the present invention aims at the diagnosis difficulty of the radiation interference source, uses an oscilloscope to measure the time domain waveform of the radiation electric field, compares the radiation electric field waveform to the amplitude modulation wave in the communication theory, analyzes its narrow band after bandpass filtering, and reveals the circuit PWM modulation information embedded in the radiated EMI through envelope demodulation, and then determines the dominant interference source according to the known power electronic topology modulation strategy; it can quickly diagnose the radiation interference source and provide guidance for the deployment of precise suppression strategy for the dominant interference source.

[0024] The radiation interference propagation path diagnosis method of the power electronic device provided by the present invention aims at the diagnosis difficulty of the radiation interference path. Based on circuit theory, the node voltage and branch current are measured, and the dominant radiation cable antenna, the dominant radiation current direction and the hidden coupling are gradually determined. According to the dominant radiation current direction, it is confirmed whether the Y-type capacitor in the EMI filter connected to the dominant radiation cable antenna can effectively filter, and by judging whether there is hidden coupling in the multi-stage common-mode inductor of the EMI filter connected to the dominant radiation cable, these failed Y-type capacitors and hidden couplings are the dominant paths that need to be identified and cause the filtering performance to deteriorate, and finally provide guidance for the targeted suppression of the dominant path; the radiation path can be quickly diagnosed, and the direction for the deployment of accurate suppression strategy for the dominant interference path is provided, and at the same time, a means is provided for revealing the mechanism of EMI filtering failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the coupling of multiple radiation interference sources in power electronic devices.

[0026] Figure 2 Schematic diagram of the propagation path of electromagnetic interference radiated by power electronic devices.

[0027] Figure 3 A flow chart of a method for diagnosing radiation interference sources of a power electronic device provided in an embodiment of the present invention.

[0028] Figure 4 A schematic diagram comparing the amplitude modulation wave and radiated EMI provided in an embodiment of the present invention.

[0029] Figure 5 This is a schematic diagram of the principle of modulation and demodulation of amplitude modulated signals.

[0030] Figure 6 A simulation diagram of multi-source radiation electromagnetic interference provided by an embodiment of the present invention.

[0031] Figure 7 A simulation diagram of the diagnostic envelope spectrum of the dominant interference source with the same switching frequency and different modulation strategies provided in an embodiment of the present invention.

[0032] Figure 8 A simulation diagram of the radiated electromagnetic interference spectrum provided by an embodiment of the present invention.

[0033] Fig. 9 (a) and (b) are respectively a time domain EMI diagram and an envelope spectrum diagram of the simulated electromagnetic interference bandpass radiation EMI at 30 MHz provided by an embodiment of the present invention.

[0034] Fig.10 A flow chart of a method for diagnosing a radiation interference propagation path of a power electronic device provided in an embodiment of the present invention.

[0035] Fig.11 (a) and (b) are respectively an independent radiation model and circuit diagram, and a coupled radiation model and circuit diagram of a multi-cable antenna provided in an embodiment of the present invention.

[0036] Fig.12 A flow chart of a method for diagnosing a dominant radiating cable antenna provided in an embodiment of the present invention.

[0037] Fig.13 (a) and (b) are respectively a Y-type capacitor path direction diagnosis principle diagram and a current measurement flow chart provided in an embodiment of the present invention.

[0038] Fig.14(a) and (b) are respectively a schematic diagram and a flow chart of an implicit coupling diagnosis based on voltage measurement provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] Radiated electromagnetic interference source diagnosis refers to determining the dominant radiated circuit topology in power electronic devices. As the demand for power conversion develops towards multi-functions, power electronic devices begin to integrate multiple types and groups of conversion topologies. Different topology circuits produce electromagnetic interference with different characteristics. Multiple electromagnetic interferences couple with each other to form multi-source electromagnetic interference of the entire power electronic device, causing the problem of unknown dominant interference sources. Figure 1 As shown in the figure, a power electronic device has four circuit topologies, each of which generates a type of radiated EMI (Electromagnetic Interference). These radiated EMIs are coupled to each other to generate multi-source radiated EMIs, which are radiated outward together and received by the EMC antenna at the same time without distinction. The spectrum is finally tested by the spectrum analyzer to obtain the spectrum. However, it is unknown which type of circuit topology mainly causes the maximum peak point of the spectrum, and this needs to be diagnosed. Although there are many studies on EMI suppression technology, when the dominant interference source is unknown, the deployment of the suppression strategy is blind. Only by determining the dominant radiation circuit topology that causes the spectrum peak emission can targeted and accurate suppression be taken for radiated interference.

[0041] Radiated electromagnetic interference path diagnosis refers to determining how the radiated EMI is transmitted and emitted outward. Figure 2 As shown in Figure 1, the power electronic device that integrates multiple circuit topologies is itself a complex circuit network. In addition to directly connected circuit elements, this type of network also contains indirectly connected electromagnetic field coupling effects. Radiated electromagnetic interference eventually propagates along the complex circuit network to the port of the power electronic device, emitting electromagnetic waves outward. Determining the main propagation path in the network is the beginning of the analysis of the radiated electromagnetic interference mechanism and precise path suppression.

[0042] At present, the diagnosis of radiated EMI still mostly adopts the "trial and error method", that is, comparing the spectrum before and after the installation of specific suppression measures. If the suppression effect is significant, the dominant path and the dominant source are diagnosed. This type of method is very dependent on experience and puts the cart before the horse. If the dominant radiation path and the dominant source can be quickly diagnosed, and then targeted suppression strategies can be adopted, the efficiency of radiated EMI analysis will be significantly improved, and even unnecessary suppression measures can be reduced, which will help improve the quality and reduce the cost of power electronic devices.

[0043] Based on this, an embodiment of the present invention provides a method for diagnosing radiation interference sources of a power electronic device, such as Figure 3 As shown, including:

[0044] S1, measuring the radiated electromagnetic interference time domain signal (also called radiated EMI time domain signal) of the target power electronic device, performing FFT processing on it to obtain the corresponding EMI spectrum, and obtaining the peak frequency f of the EMI spectrum PK ;

[0045] S2, in K·f PK The radiated EMI time domain signal is bandpass filtered for the bandpass width; wherein the value range of K is [0.05, 0.1];

[0046] S3, performing envelope demodulation and FFT processing on the radiated EMI time domain signal after bandpass filtering in sequence to obtain the switching frequency of the radiated interference source, and taking the converter in the target power electronic device that uses the switching frequency as a modulation parameter as the radiated interference source of the target power electronic device.

[0047] The radiation interference source diagnosis method provided in the embodiment of the present invention adopts the radiation interference dominant source identification technology based on envelope demodulation. The core idea is to compare the radiated EMI with the amplitude modulated wave (AM), analyze their similarities, and use the method of processing the amplitude modulated wave AM, namely envelope demodulation, to process the radiated EMI.

[0048] Figure 4Radiated EMI and amplitude modulation waves are compared from the perspectives of carrier wave, modulation wave and demodulation method. AM and radiated EMI have similar waveforms, both of which are high-frequency oscillations. Radiated EMI and AM have similar carrier waves. For AM, the carrier wave is a sine wave with a fixed frequency, while for radiated EMI, the carrier wave is a sine wave mixed with multiple frequencies, which is slightly different from the AM carrier wave, but a sine wave carrier with only a fixed frequency can be achieved through a bandpass. The modulation wave of AM is an arbitrary waveform, while for radiated EMI, the modulation wave is a modulation strategy, and both satisfy that the modulation wave frequency is much smaller than the carrier frequency. This is because the modulation wave of AM is the information to be transmitted, which can be any low-frequency waveform (lower frequency than the carrier frequency; radiated EMI can be considered to have such a modulation wave: when the switching device is switched, the modulation wave amplitude is large, and when the switching device is not switched, the modulation wave amplitude is 0. Therefore, the periodic characteristics of the modulation wave of radiated EMI actually reflect the switching frequency of the converter that generates radiated EMI. The demodulation result of AM is the recovered transmission signal, while the demodulation result of radiated EMI is the pulse period of the modulation strategy of the converter, that is, the switching frequency. Therefore, AM and radiated EMI are highly similar. The envelope demodulation method is borrowed to the processing of radiated EMI.

[0049] Figure 5 The principle of modulation and demodulation of amplitude modulation signals is demonstrated. The low frequency modulated wave is multiplied by the high frequency carrier to obtain the AM wave. After the AM wave is envelope detected, the original modulated wave information to be transmitted is restored. Therefore, an important feature that enables AM waves to be effectively processed is that the frequency of the carrier is fixed.

[0050] Figure 3 The proposed method for diagnosing radiated electromagnetic interference sources is given. First, the time domain waveform of radiated EMI is measured according to the standard test process. It is worth noting that the test equipment should be a high-bandwidth oscilloscope instead of an EMI receiver. This is because the identification of the dominant interference source requires time domain information, not just spectrum information. If an EMI receiver is used, the time domain information of radiated EMI cannot be obtained.

[0051] Then, the EMI spectrum is calculated based on FFT to determine the peak frequency f PK , and the time domain EMI is at the peak frequency f PK The passband width can be selected as K times of the current frequency. The value range of K is [0.05, 0.1]. For example, when K = 0.1, the passband range is [0.95f PK ,1.05f PK ].

[0052] It should be noted that the passband width is not recommended to be the same as the resolution bandwidth RBW specified in the standard. This is because the RBW specified in the standard is relatively small at high frequencies, the envelope after the passband tends to be stable, and the recognition performance of time domain spikes decreases, which is specifically manifested as a decrease in the highest switching frequency of the distinguishable converter. Considering that the change in the dominant interference source category is not a sudden change from frequency point to frequency point, but a gradual change. In a relatively wide spectrum range such as K·f PK , the dominant interference source of EMI is of the same category, but the time domain peak recognition performance of the envelope after bandpass is better, and this bandpass width should be used. Then, the time domain waveform of the radiated EMI after bandpass has been converted into an amplitude modulation wave AM, so envelope demodulation can be used. First, the upper envelope is calculated directly according to the Hilbert transform. This process can reveal the switching pulse moment of the modulation strategy adopted. Then, according to the switching pulse moment, the FFT spectrum of the upper envelope is calculated. This process can reveal the switching frequency of the dominant interference source. Finally, according to the switching frequency of the dominant interference source and the known modulation strategy of the converter, determine which converter the dominant interference source belongs to, and the converter is the dominant interference source. It can be understood that when the converter adopts different modulation strategies, the modulation parameters adopted---the switching frequency are also different. Therefore, according to the switching frequency of the dominant interference source, it can be known which converter the dominant interference source is.

[0053] In summary, the core idea of ​​the identification method proposed in the embodiment of the present invention is to convert the radiated EMI with multi-frequency sine as the carrier into an amplitude modulated wave with a single-frequency sine as the carrier after bandpass pre-selection processing, and then determine the switching frequency of the dominant interference source through envelope demodulation and envelope spectrum, and finally determine which power electronic circuit the dominant interference source comes from.

[0054] It should be pointed out that even if the switching frequencies of the two types of converters are the same, since sinusoidally modulated PWM has sideband harmonics compared to fixed duty cycle PWM, the shapes of the two on the spectrum are still different and can be distinguished.

[0055] That is, for two types of converters with the same switching frequency and different modulation strategies, their envelope spectra are also different and can still be distinguished. For example, SPWM has sideband harmonics compared to FDPWM; variable frequency PWM has a wide switching frequency (that is, the envelope spectrum presents a very wide peak), while the envelope spectra of the other two PWMs present very narrow peaks. By simulating the envelope spectrum of multi-source coupled interference with FDPWM and DPWM modulation, such as Figure 7 As shown in the figure, the switching frequency of these two interference sources is 10kHz, but their envelope spectra can still be distinguished. FDPWM has a very narrow peak value, and it can be seen that the one with the largest amplitude in the envelope spectrum is FDPWM. The spectrum with some sideband harmonics and a certain width at the bottom is DPWM.

[0056] The correctness of the diagnosis of radiated electromagnetic interference sources can be verified through simulation. Figure 6 The simulation shows two types of electromagnetic interference sources, 10kHz discontinuous PWM (DPWM) with an amplitude of 1 and 300kHz fixed duty PWM (FDPWM) with an amplitude of 10, which are mixed together to generate multi-source electromagnetic interference. The multi-source electromagnetic interference is then high-pass processed at a frequency of 30MHz to generate simulated radiated electromagnetic interference. The dominant interference source of radiated electromagnetic interference is determined using the proposed identification method.

[0057] Figure 8 For the simulated radiated EMI spectrum, it can be determined that the peak frequency band that needs to be diagnosed is 30MHz. In addition, since the simulated electromagnetic interference source has an ideal fixed switching frequency, there will be no high-frequency spread spectrum effect of the EMI generated by the non-ideal fixed switching frequency PWM in the experiment, and the EMI spectrum presents a discrete spectrum. From the spectrum peak, it can also be determined that the dominant electromagnetic interference source is 300kHzFDPWM. This result can be used to verify the proposed diagnostic method. It is worth noting that in the experimental measurement spectrum, the radiated EMI does not appear as a discrete spectrum due to its non-ideal characteristics, but must be a continuous spectrum. The modulation strategy cannot be determined by the discrete spectrum peak, which further emphasizes the superiority of the proposed diagnostic method.

[0058] Fig. 9 (a) shows the bandpass radiated EMI at 30MHz. Fig. 9 (b) in the figure is the envelope spectrum of the simulated multi-source electromagnetic interference. The 10kHz peak with sideband harmonics and the 300kHz peak without sideband harmonics are Fig. 9 It can be clearly seen in (b) that the amplitude of the latter is much larger than the former, which indicates that 300kHz FDPWM is the main source of electromagnetic interference, verifying the correctness of the diagnosis method.

[0059] In order to quickly diagnose the radiation dominant path, an embodiment of the present invention provides a method for diagnosing the radiation interference propagation path of a power electronic device, comprising:

[0060] A1, determine the radiation type of the cable connected to the radiation interference source of the target power electronic device; wherein the radiation type includes independent radiation and coupled radiation. If the cables are all independently connected to the load, the radiation type is independent radiation; if the cables are all connected to the load together with other cables, the radiation type is coupled radiation;

[0061] A2. Determine the radiation interference propagation path of the target power electronic device according to the radiation type of the antenna; wherein, if the radiation type of the cable is independent radiation, the cable with the largest radiation current is used as the radiation cable, and its path is used as the radiation interference propagation path; if the radiation type of the cable is coupled radiation, the cable with the largest radiation voltage is used as the radiation cable, and its path is used as the radiation interference propagation path.

[0062] The radiation interference source of the target power electronic device adopts the radiation interference source diagnosis method of the power electronic device as described in any of the above embodiments (such as Fig.10 The diagnosis is obtained by using the radiation interference source diagnosis method of any existing power electronic device as shown in the figure.

[0063] Preferably, in order to identify the key leakage path in the installed EMI filter to guide targeted solutions, and ultimately increase the actual performance of the EMI filter without increasing the volume of the EMI filter, and improve the power density of the power electronic device, the radiation interference propagation path diagnosis method of the power electronic device provided by the embodiment of the present invention also includes:

[0064] A3, judging whether the converter-side current I1 of the Y-type capacitor in the EMI filter connected to the radiation cable is less than the port-side current I2, if so, the Y-type capacitor can effectively filter, otherwise it cannot effectively filter;

[0065] A4, determine whether the voltages at both ends of the multi-stage common-mode inductors in the EMI filter connected to the main radiating cable decrease step by step. If so, there is no hidden coupling in the multi-stage common-mode inductors. If not, there is hidden coupling in the common-mode inductors that do not decrease step by step.

[0066] The radiation interference propagation path diagnosis method of the power electronic device provided by the embodiment of the present invention adopts the radiation interference path diagnosis technology based on voltage and current detection.

[0067] 1. Lead the diagnostic process of radiating cable antennas.

[0068] For power electronic devices, cables are always the main radiation source due to their large size. For high-power converters, the metal chassis is a good shielding layer that blocks the radiation of converter components, while the external cables of the chassis are the main radiation source. For small low-power power converters, since the converter body is too small, even if the converter does not have a metal chassis, the external cables are still the main radiation source.

[0069] It is always necessary to diagnose the dominant radiating antenna. This is important for power electronics with multiple input / output cable antennas, but it is also necessary for power electronics with a single input and single output. Since the radiated electric fields of the input and output cables are not always the same, for example, some studies have found significant differences in the radiated currents of the input and output cables.

[0070] According to the standard "GB / T 6113.203-2020 Radio disturbance and immunity measurement methods - radiated disturbance measurement", in the radiated EMI test, the cable termination should use a common mode absorber device (CMAD), which can be regarded as an open circuit termination. Whether the cable is terminated independently or short-circuited and coupled, it corresponds to different radiation models. Fig.11 (a) and (b) are simplified radiation models of typical cable antennas, including independent radiation and coupled radiation.

[0071] Fig.11 The independent radiation in (a) means that the antenna cables are not connected and each radiates independently. Power electronic devices with multiple output cables are typical examples of independent radiation models. This is because different output ends need to be terminated with CMADs separately. In addition, converters with non-negligible chassis size are also cases of independent radiation models. This is because the input and output cables and the chassis each form a pair of antennas. The typical feature of independent radiation is that the current on the cable may be very different. The dominant radiating antenna can be determined based on the current size, as shown in equations (1) and (2). The radiated electric field E emitted by the device system is composed of the two cable antenna radiated electric fields E A1 ,E A2 Composition, each cable antenna electric field E A1 ,E A2 Both are related to the antenna current I A1 ,I A2 Proportional to G IA1 ,G IA2 , and because the cable lengths are close, the proportionality coefficients are similar. Then when I A1 Current ratio I A2 When it is larger, the radiated electric field E A1 Must be greater than E A2 , cable 1 is identified as the dominant antenna, as shown in equation (2). Since the measured current of the cable is the antenna current at this time, the measured current is the criterion for determining the dominant radiating antenna in the independent radiation model.

[0072] E=E A1 +E A2 =G IA1 I A1 +G IA2 I A2 ≈G IA (IA1 +I A2 ) (1)

[0073]

[0074] Fig.11 The coupled radiation in (b) usually occurs in power electronic devices with multiple inputs. Different power sources supply power to the device, such as multiple photovoltaic (PV) panels or multiple energy storage batteries. When performing radiated EMC testing, these multiple input cables are connected to the same input power source. Therefore, the cable antenna is short-circuited. In this model, the current of the coupled cable is directly connected and the current I is measured. m Not equal to the antenna current I A , the magnitude relationship of the antenna current cannot be obtained based on the relationship of the measured current, as shown in equation (3). Therefore, the measured current cannot be used as a criterion for the diagnosis of the dominant radiation cable in the coupled radiation model.

[0075]

[0076] Radiation voltage V A1 ,V A2 It can be used as the leading cable antenna diagnostic criterion for the coupled radiation model. The antenna radiation electric field is also linearly related to the antenna port voltage, G VA1 ,G VA2 is the proportionality coefficient of the port voltage to the electric field of the two antennas, and the proportionality coefficients are very close, as shown in equation (4). It should be noted that the measured voltage is the antenna voltage, so the larger the measured antenna port voltage, the larger the electric field radiated by the antenna, as shown in equation (5).

[0077] E=G VA1 V A1 +G VA2 V A2 ≈G VA (V A1 +V A2 ) (4)

[0078]

[0079] Fig.12It is a flowchart of the proposed antenna diagnosis method. For independent radiation, the radiation current can be used as a criterion for the dominant antenna. The antenna with the largest radiation current is the main radiation antenna. However, for coupled radiation, it is not appropriate to use only the magnitude of the radiation current as the criterion for the dominant antenna. Their radiation current amplitudes are always very close because they are connected to the same auxiliary power supply equipment. Radiation voltage measurement can solve the problem of diagnosing the dominant antenna in coupled radiation. The radiation voltage at the port is the fundamental cause of exciting the radiation current of the antenna. The highest radiation voltage excites the current in all antenna cables. Therefore, the radiation voltage is an accurate criterion for judging the dominant antenna.

[0080] 2. Diagnosis of the effectiveness of Y-capacitor filtering

[0081] The Y-capacitor in the converter, as an important part of electromagnetic interference filtering, provides a necessary path to bypass electromagnetic interference back to the chassis. However, for high-power power electronic devices, due to the existence of parasitic inductance and skin effect, the large metal chassis cannot be regarded as an equipotential body. There may be voltage jumps on the chassis reference ground, which may cause the current direction on the Y-capacitor not to flow into the ground but to flow out from the ground. The electromagnetic interference flowing out through the Y-capacitor will cause the electromagnetic interference filter to fail. It is impossible to directly measure the direction of the capacitor current because the capacitor pins are very small and an EMI current clamp cannot be installed.

[0082] Fig.13 Figures (a) and (b) in [reference] show the principle and process of path direction diagnosis based on current measurement. Since the radiated EMI propagates outside the converter, the current directions of the converter side and port side currents I1 and I2 of the Y-capacitor are always determined to be outward, while the direction of the Y-capacitor grounding current I g is unknown. But at this node, according to Kirchhoff's Current Law (KCL), there is formula (1). According to the magnitudes of I2 and I1, the current direction of I g can be determined.

[0083] I1 - I2 = I g (6)

[0084] When I2 < I1, I g flows into the chassis ground, and the Y-capacitor plays an inhibitory role in electromagnetic interference. When I2 > I1, I g flows out from the chassis ground, and the Y-capacitor plays a deteriorating role in electromagnetic interference. In this case, continuously increasing the CM inductance impedance at I1 before the capacitor cannot suppress the emission of this capacitor branch. The flowchart of the proposed path direction diagnosis method is as shown in Fig.13 Figure (b) in [reference].

[0085] 3. Diagnosis of hidden coupling

[0086] CM inductance (i.e. common mode inductance) is an important component of EMI filtering and propagation path, providing key impedance to suppress the propagation of radiated EMI. However, inductance is also susceptible to other undesirable and unknown couplings, which can cause radiated EMI to fail to be blocked as expected, which may lead to filtering failure and even EMC certification failure. Therefore, it is very necessary to diagnose hidden and undesirable coupling.

[0087] There are two main types of unwanted coupling, from upstream components, and from other unknown sources, such as non-filter components such as fan lines. For multi-stage inductors between the converter end and the input / output end of the filter, the voltage across each inductor should decrease step by step, otherwise the inductor has unwanted coupling and should be shielded. Taking the secondary common-mode inductor between the converter end and the output / input end of the filter as an example, the hidden coupling diagram is as follows Fig.14 As shown in (a), V a is the voltage of the front end of the first-stage common-mode inductor to ground, V b is the voltage of the first-stage common-mode inductor to ground, V c is the voltage at the back end of the second-stage common-mode inductor to ground (i.e., the input / output voltage of the filter). These undesirable hidden couplings make the voltage distribution on the propagation path inconsistent with the ideal one. Therefore, hidden coupling can be diagnosed by voltage measurement.

[0088] When V a >V b >V c When V c >V b , there is undesirable coupling and the common mode inductance should be shielded. The flowchart of the proposed hidden coupling diagnosis method is shown in Fig.14 As shown in (b) in .

[0089] An embodiment of the present invention provides a radiation interference source diagnosis device for a power electronic device, comprising:

[0090] The first processing module is used to measure the radiated EMI time domain signal of the target power electronic device, perform FFT processing on it to obtain the corresponding EMI spectrum, and obtain the peak frequency f of the EMI spectrum. PK ;

[0091] The second processing module is used to PK The radiated EMI time domain signal is bandpass filtered for the bandpass width; wherein the value range of K is [0.05, 0.1];

[0092] The second processing module is used to perform envelope demodulation and FFT processing on the radiated EMI time domain signal after bandpass filtering in sequence to obtain the switching frequency of the radiation interference source, and use the converter in the target power electronic device that uses the switching frequency as the modulation parameter as its radiation interference source.

[0093] An embodiment of the present invention provides a device for diagnosing a radiation interference propagation path of a power electronic device, comprising:

[0094] A judgment module, used to judge the radiation type of the cable connected to the radiation interference source of the target power electronic device; wherein the radiation type includes independent radiation and coupled radiation. If the cables are all independently connected to the load, the radiation type is independent radiation; if the cables are all connected to the load together with other cables, the radiation type is coupled radiation;

[0095] A processing module is used to determine the radiation interference propagation path of the target power electronic device according to the radiation type of the antenna; wherein, if the radiation type of the cable is independent radiation, the cable with the largest radiation current is used as the radiation cable, and its path is used as the radiation interference propagation path; if the radiation type of the cable is coupled radiation, the cable with the largest radiation voltage is used as the radiation cable, and its path is used as the radiation interference propagation path.

[0096] An embodiment of the present invention provides an electronic device, including: a computer-readable storage medium and a processor;

[0097] The computer-readable storage medium is used to store executable instructions;

[0098] The processor is used to read the executable instructions stored in the computer-readable storage medium to execute the method for diagnosing the radiation interference source of the power electronic device as described in any of the above embodiments or the method for diagnosing the radiation interference propagation path of the power electronic device as described in any of the above embodiments.

[0099] An embodiment of the present invention provides a computer-readable storage medium, which stores computer instructions, and the computer instructions are used to enable a processor to execute a method for diagnosing a radiation interference source of a power electronic device as described in any of the above embodiments or a method for diagnosing a radiation interference propagation path of a power electronic device as described in any of the above embodiments.

[0100] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for diagnosing radiation interference sources of a power electronic device, characterized in that: include: S1, measure the radiated EMI time domain signal of the target power electronic device, perform FFT processing on it to obtain the corresponding EMI spectrum, and obtain the peak frequency f of the EMI spectrum PK ; S2, in K·f PK The radiated EMI time domain signal is bandpass filtered for the bandpass width; wherein the value range of K is [0.05, 0.1]; S3, performing envelope demodulation and FFT processing on the radiated EMI time domain signal after bandpass filtering in sequence to obtain the switching frequency of the radiated interference source, and taking the converter in the target power electronic device that uses the switching frequency as a modulation parameter as its radiated interference source.

2. The method according to claim 1, characterized in that In step S1, a high-bandwidth oscilloscope is used to measure the radiated EMI time domain signal of the target power electronic device.

3. The method according to claim 1 or 2, characterized in that In step S3, the radiated EMI time domain signal after bandpass filtering is subjected to envelope demodulation and FFT processing in sequence to obtain the switching frequency of the radiated interference source, including: Performing Hilbert transform on the radiated EMI time domain signal after bandpass filtering to calculate the upper envelope, so as to obtain the switching pulse moment of the radiated EMI time domain signal; The upper envelope is processed by FFT to obtain an envelope spectrum, and the switching frequency of the radiated EMI time domain signal is obtained according to the switching pulse timing.

4. A method for diagnosing the propagation path of radiation interference of a power electronic device, characterized in that: include: A1, determine the radiation type of the cable connected to the radiation interference source of the target power electronic device; wherein the radiation type includes independent radiation and coupled radiation. If the cables are all independently connected to the load, the radiation type is independent radiation; if the cables are all connected to the load together with other cables, the radiation type is coupled radiation; A2. Determine the radiation interference propagation path of the target power electronic device according to the radiation type of the antenna; wherein, if the radiation type of the cable is independent radiation, the cable with the largest radiation current is used as the radiation cable, and its path is used as the radiation interference propagation path; if the radiation type of the cable is coupled radiation, the cable with the largest radiation voltage is used as the radiation cable, and its path is used as the radiation interference propagation path.

5. The method according to claim 4, characterized in that The radiation interference source of the target power electronic device is diagnosed by using the diagnosis method according to any one of claims 1 to 3.

6. The method according to claim 4, characterized in that Also includes: A3, judging whether the converter-side current I1 of the Y-type capacitor in the EMI filter connected to the radiation cable is less than the port-side current I2, if so, the Y-type capacitor can effectively filter, otherwise it cannot effectively filter; A4, determine whether the voltages at both ends of the multi-stage common-mode inductors in the EMI filter connected to the main radiating cable decrease step by step. If so, there is no hidden coupling in the multi-stage common-mode inductors. If not, there is hidden coupling in the common-mode inductors that do not decrease step by step.

7. A radiation interference source diagnostic device for a power electronic device, characterized in that: include: The first processing module is used to measure the radiated EMI time domain signal of the target power electronic device, perform FFT processing on it to obtain the corresponding EMI spectrum, and obtain the peak frequency f of the EMI spectrum. PK ; The second processing module is used to PK The radiated EMI time domain signal is bandpass filtered for the bandpass width; wherein the value range of K is [0.05, 0.1]; The second processing module is used to perform envelope demodulation and FFT processing on the radiated EMI time domain signal after bandpass filtering in sequence to obtain the switching frequency of the radiation interference source, and use the converter in the target power electronic device that uses the switching frequency as the modulation parameter as its radiation interference source.

8. A device for diagnosing the propagation path of radiation interference of a power electronic device, characterized in that: include: A judgment module, used to judge the radiation type of the cable connected to the radiation interference source of the target power electronic device; wherein the radiation type includes independent radiation and coupled radiation. If the cables are all independently connected to the load, the radiation type is independent radiation; if the cables are all connected to the load together with other cables, the radiation type is coupled radiation; A processing module is used to determine the radiation interference propagation path of the target power electronic device according to the radiation type of the antenna; wherein, if the radiation type of the cable is independent radiation, the cable with the largest radiation current is used as the radiation cable, and its path is used as the radiation interference propagation path; if the radiation type of the cable is coupled radiation, the cable with the largest radiation voltage is used as the radiation cable, and its path is used as the radiation interference propagation path.

9. An electronic device, characterized in that: include: A computer readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is used to read the executable instructions stored in the computer-readable storage medium, and execute the method according to any one of claims 1 to 3 or the method according to any one of claims 4 to 6.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable a processor to execute the method according to any one of claims 1 to 3 or the method according to any one of claims 4 to 6.

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