Design method of active common-mode interference filter for high-voltage inverter system

Abstract

The application discloses a design method of an active common-mode interference filter of a high-voltage inverter system. The method is characterized in that the cut-off frequency of the active filter is far less than the switching frequency of the inverter by analyzing the frequency spectrum characteristics of the common-mode voltage at the output side of the inverter, so that the common-mode voltage is suppressed. Meanwhile, the inverter system after the active filter is connected is analyzed simply, the system transfer function is obtained, and the element values of each link of the active filter are determined. In view of the problem that the input impedance of the amplification link of the active filter is not high and crossover distortion exists, the application designs an improved structure of the active filter, that is, a voltage multiplier is added in front of the power amplification circuit, and finally it is verified through experiments that the active filter has a good suppression effect on the common-mode voltage of the high-voltage inverter system.

Description

Technical Field

[0001] This invention belongs to the field of filter design technology, specifically relating to a design method for an active common-mode interference filter for a high-voltage inverter system. Background Technology

[0002] In high-voltage inverter systems, the inverter's output common-mode voltage can cause shaft voltage and shaft current in the motor via internal parasitic capacitance. Furthermore, the electromagnetic compatibility issues arising from high-frequency common-mode voltage can pose a significant threat to other electrical equipment surrounding the inverter system. Therefore, engineering practices require measures to mitigate the negative impacts of common-mode voltage in the inverter system, thereby maintaining stable and reliable system operation.

[0003] Passive filters are widely used in high-frequency power electronic products due to their simple structure and ease of implementation. However, improving the filtering effect of passive filters requires increasing the values ​​of inductors and capacitors. Capacitors cannot be too large due to safety concerns, while increasing the inductor size makes the filter very large and bulky. Active filters use active cancellation to eliminate common-mode voltage in the system. This is a dynamic compensation process that overcomes the limitation of fixed compensation values ​​in passive filters, making it a current research hotspot in filter design.

[0004] In the research on active suppression methods for common-mode voltage on the output side of PWM inverters, the literature [S. Ogasawara, H. Ayano and H. Akaki, "An active circuit for cancellation of common-mode voltage generated by a PWM inverter," PESC97. Record 28th Annual IEEE Power Electronics Specialists Conference. Formerly Power Conditioning Specialists Conference 1970-71. Power Processing and Electronic Specialists Conference 1972, 1997, pp. 1547-1553 vol. 2] designed a feedforward active filter structure, which can effectively eliminate the common-mode voltage of the system. However, since the amplification stage of this active filter adopts a push-pull structure composed of complementary transistors, and the collector of the transistor is directly connected to the DC bus at the input of the inverter, this structure is not suitable for inverter systems under high voltage input due to the voltage withstand capability limitation of the active devices. The literature [Chenggang Mei, JCBalda, WPWaite and K.Carr, "Active cancellation of common-mode voltages on drives rated 460-V and higher," IEEE International Electric Machines and Drives Conference, 2003. IEMDC'03., Madison, WI, USA, 2003, pp. 1845-1851 vol. 3] proposes a voltage divider sampling and voltage doubler injection scheme based on this structure, which can improve the applicable voltage level of the active filter. However, since the input impedance of the amplification stage is not infinite, the introduction of the voltage divider capacitor will cause distortion in the common-mode voltage sampling. Furthermore, the crossover distortion problem inherent in the push-pull circuit will also affect the common-mode voltage compensation effect. Summary of the Invention

[0005] In view of the above, this invention provides a design method for an active common-mode interference filter (AMOR) in a high-voltage inverter system. Based on the waveform characteristics of the common-mode voltage on the inverter output side, a feedforward voltage divider sampling compensation AMOR is designed. The single-phase equivalent circuit of the inverter system after connecting the AMOR is obtained by simplifying the three-phase system, and the system transfer function is analyzed. Then, the parameter selection for each stage of the AMOR is determined. To improve the low-frequency compensation effect of the AMOR, a voltage multiplier circuit is added before the active amplification stage, solving the problems of low input impedance and crossover distortion in the power amplifier circuit. Finally, a physical AMOR is fabricated and experimentally verified.

[0006] A design method for an active common-mode interference filter in a high-voltage inverter system includes the following steps:

[0007] (1) Measure the time-domain waveform of the common-mode voltage on the output side of the inverter, and then perform a fast Fourier transform on it to analyze the characteristics of the common-mode interference spectrum. Based on the test results, obtain the magnitude of the time-domain amplitude of the common-mode voltage and the main distribution frequency band of the common-mode interference.

[0008] (2) An active common-mode interference filter is designed based on the active cancellation principle, which includes a common-mode voltage sampling stage, an active amplification stage, and a common-mode voltage compensation stage.

[0009] (3) Analyze the single-phase equivalent circuit of the inverter system after the active common-mode interference filter is connected, calculate the transfer function of the active common-mode interference filter after it is connected to the system, and determine the relevant parameters;

[0010] (4) Based on the device parameters and selection of the active common-mode interference filter, a physical prototype was made, and the common-mode voltage on the output side of the inverter was tested after the active common-mode interference filter was connected to verify the suppression effect of the active common-mode interference filter on the common-mode interference of the inverter system.

[0011] Furthermore, in step (1), an oscilloscope and a passive probe are used to measure and perform spectrum analysis on the common-mode voltage of the inverter output side. The peak-to-peak value of the common-mode voltage on the inverter output side is U. CM,max The frequency point corresponding to the maximum common-mode voltage amplitude in the spectrum analysis results is the inverter switching frequency f. sw .

[0012] Furthermore, the common-mode voltage sampling stage includes three passive networks Z1 and one passive network Z2. One end of each of the three passive networks Z1 is connected to the three-phase output port of the inverter to detect the common-mode voltage on the output side of the inverter. The other end of each of the three passive networks Z1 is connected in a star configuration and is used to divide the voltage with the passive network Z2. The voltage division ratio is 1:n, that is, the neutral point is connected to one end of the passive network Z2, and the other end of the passive network Z2 is grounded.

[0013]

[0014] Where z1 is the impedance value of passive network Z1, and z2 is the impedance value of passive network Z2. Both passive networks Z1 and Z2 adopt an RLC series structure.

[0015] Furthermore, the active amplification stage includes four voltage divider resistors R1 to R4, two NPN transistors T1 and T2, one PNP transistor T3, and a DC filter capacitor C. f And a DC power supply, wherein one end of R1 is connected to the collector of T2 and connected to a DC bias voltage V. cc The other end of R1 is connected to one end of R2, the collector of T1, and the base of T2. The other end of R2 is connected to one end of R3, the base of T1, and the neutral point of the passive network Z1. The other end of R3 is connected to one end of R4, the emitter of T1, and the base of T3. The other end of R4 is connected to the collector of T3 and grounded. The emitters of T2 and T3 are connected. T2 and T3 form a push-pull circuit. C f The DC component of the push-pull circuit output is filtered, and the DC bias voltage V is applied. cc Powered by a DC power supply.

[0016] Furthermore, the common-mode voltage compensation stage consists of a four-winding transformer wound on the same toroidal magnetic core. One end of the primary winding of the transformer is connected to the emitter of T2, and the other end is connected to C. f One end is connected; the three secondary windings of the transformer are respectively connected in series on the three-phase line between the inverter output side and the motor; in order to achieve voltage multiplication injection of common mode voltage, the number of turns of the three secondary windings is equal and in a certain proportion to the number of turns of the primary winding.

[0017] Furthermore, the common-mode voltage sampling circuit detects the time-domain peak-to-peak value of the common-mode voltage as U. CM,max / n should be less than the voltage rating of the transistor used in the active amplification stage. If the transistor voltage rating is low, increase the value of n appropriately; otherwise, decrease the value of n.

[0018] Furthermore, in order to completely eliminate the common-mode voltage on the inverter output side, the voltage division ratio of the common-mode voltage sampling stage should satisfy n = k, where k is the turns ratio of the transformer secondary winding to the primary winding in the common-mode voltage compensation stage.

[0019] Furthermore, the transfer function expression of the active common-mode interference filter after it is connected to the system in step (3) is as follows:

[0020]

[0021] Where: H(s) is the transfer function of the active common-mode interference filter after it is connected to the system, V out (s) represents the frequency domain expression of the common-mode voltage on the inverter output side after the active common-mode interference filter is applied, V cm (s) represents the frequency domain expression of the common-mode voltage on the inverter output side without an active common-mode interference filter, where s is the Laplace operator, ω n Let be the resonant angular frequency of the transfer function. Here, r is the damping coefficient of the transfer function, r1 is the resistance of the voltage divider resistor R1, and c1 is the capacitance in the RLC series structure of the passive network Z1. f DC filter capacitor C f The capacitance value is β, which is the current amplification factor of the active amplification stage (the larger the value, the better, but it is limited by the voltage withstand requirements of the transistor itself), and l2 is the inductance value of the secondary winding of the transformer in the common-mode voltage compensation stage.

[0022] Furthermore, to achieve better common-mode interference suppression in an active common-mode interference filter, the resonant frequency f of the transfer function must be guaranteed. n Less than the inverter switching frequency f sw f n =ω n / 2π.

[0023] This invention analyzes the spectral characteristics of the common-mode voltage on the inverter output side, ensuring that the cutoff frequency of the active filter is much lower than the inverter's switching frequency, thereby suppressing the common-mode voltage. Simultaneously, by simplifying the analysis of the inverter system after connecting the active filter, the system transfer function is obtained, thus determining the component values ​​for each stage of the active filter. Addressing the issues of low input impedance and crossover distortion in the active filter's amplification stage, this invention designs an improved active filter structure by adding a voltage multiplier before the power amplifier circuit. Finally, experiments verify that the proposed active filter has a good suppression effect on the common-mode voltage of the inverter system.

[0024] Compared to active filters that use only complementary transistors in a push-pull circuit as the amplification stage, this invention improves the active amplification stage by adding a voltage multiplier before the push-pull circuit. This solves the inherent crossover distortion problem of push-pull circuits and increases the input impedance of the active amplification stage, thereby improving the low-frequency suppression effect of the active common-mode filter. Furthermore, the active filter design method of this invention uses voltage divider sampling and voltage multiplier injection to compensate for the common-mode voltage, overcoming the voltage withstand limitations of active devices and improving the voltage applicability level of the active filter. This provides a new approach for the design of active common-mode interference filters in high-voltage inverter systems. Attached Figure Description

[0025] Figure 1This is a schematic diagram of the circuit structure of a high-voltage inverter system.

[0026] Figure 2(a) is a schematic diagram of the time-domain waveform of the common-mode voltage on the output side of the inverter.

[0027] Figure 2(b) is a schematic diagram of the spectrum analysis of the common-mode voltage on the output side of the inverter.

[0028] Figure 3 This is a schematic diagram of the active common-mode interference filter circuit topology designed for this invention.

[0029] Figure 4 (a) is a schematic diagram of the three-phase structure of a four-winding common-mode transformer.

[0030] Figure 4 (b) is a schematic diagram of the single-phase equivalent structure of a four-winding common-mode transformer.

[0031] Figure 5 This is a schematic diagram of the single-phase equivalent circuit after an active filter is connected to the inverter system.

[0032] Figure 6 (a) is a schematic diagram of the toroidal core structure of a four-winding transformer.

[0033] Figure 6 (b) is a schematic diagram of the winding method of a four-winding transformer.

[0034] Figure 7 (a) is a physical diagram of the common-mode voltage sampling and amplification stage of the active filter.

[0035] Figure 7 (b) is a physical diagram of the common-mode voltage compensation stage of an active filter.

[0036] Figure 8(a) is a schematic diagram of the time-domain waveform of the common-mode voltage of the system after the active filter is connected.

[0037] Figure 8(b) is a schematic diagram comparing the spectrum of the common-mode voltage of the system before and after the active filter is connected.

[0038] Figure 9 This is a schematic diagram of the active filter circuit topology used in the control group.

[0039] Figure 10 (a) is a physical diagram of the common-mode voltage sampling and amplification stage of the active filter used in the control group.

[0040] Figure 10 (b) is a physical diagram of the common-mode voltage compensation stage of the active filter used in the control group.

[0041] Figure 11 This is a schematic diagram of the time-domain waveform of the common-mode voltage on the output side of the inverter system after the control group filter is connected.

[0042] Figure 12 A schematic diagram comparing the time-domain waveforms of the common-mode voltage on the output side after connecting two active filters to an inverter system. Detailed Implementation

[0043] To describe the present invention in more detail, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] This invention discloses a design method for an active common-mode interference filter in a high-voltage inverter system. Based on the analysis of the common-mode voltage waveform characteristics on the inverter output side, the cutoff frequency of the active filter and the voltage division ratio of the common-mode voltage sampling stage are determined while meeting the device withstand voltage requirements. In the active amplification stage, to increase the input impedance of the power amplifier circuit and eliminate the crossover distortion problem of the push-pull circuit, this invention uses a push-pull circuit containing a voltage multiplier as the amplification stage. Then, through simplified analysis of the inverter system after the active filter is connected, its transfer function is obtained, and the parameters and selection of each component in the active filter are determined. Finally, a physical active filter is fabricated and experimentally verified. The specific steps include:

[0045] (1) The time-domain waveform of the common-mode voltage on the inverter output side was measured, and then a fast Fourier transform was performed to analyze the characteristics of the common-mode interference spectrum. By analyzing the test results, the peak-to-peak value of the common-mode voltage on the inverter output side in the time domain can be obtained as U. CM,max The frequency point corresponding to the maximum common-mode voltage amplitude in the spectrum analysis results is the inverter switching frequency f. sw .

[0046] (2) Based on the active cancellation principle, an active common-mode interference filter is designed, comprising three parts: a common-mode voltage sampling stage, an active amplification stage, and a common-mode voltage compensation stage. The common-mode voltage sampling stage uses three star-connected passive networks Z1 to detect the common-mode voltage on the inverter output side, and then performs a voltage divider with the passive network Z2. The voltage divider ratio is denoted as 1:n. Therefore, the time-domain peak-to-peak value of the common-mode voltage obtained by the common-mode voltage sampling stage is U. CM,max / n, its value should be less than the withstand voltage requirement of the transistor used in the active amplifier stage. The active amplifier stage is a push-pull circuit containing a voltage multiplier. The common-mode voltage compensation stage consists of a four-winding transformer wound on the same toroidal core, with a turns ratio of N1:N2:N3:N4. Let k be the primary-secondary turns ratio of the common-mode transformer. To achieve completely inverted injection of the common-mode voltage on the inverter output side, the following is required:

[0047]

[0048] (3) Analyze the single-phase equivalent circuit of the inverter system after the active filter is connected, calculate the transfer function of the active filter after it is connected to the system, and determine the relevant parameters.

[0049] (4) Based on the parameters and selection of the active filter device, the filter is fabricated and the common-mode voltage on the output side of the inverter is tested after the active filter is connected to verify the suppression effect of the active filter on the common-mode interference of the high-voltage inverter system.

[0050] Example

[0051] The basic structure of the high-voltage inverter system in this embodiment is as follows: Figure 1 As shown, it consists of a DC input power supply, an NPC three-level inverter, connecting cables, and a motor, wherein the DC input power supply U DC The NPC three-level inverter is rated at 800V and uses a modulation method of in-phase carrier stacking. The modulation frequency is 25Hz and the carrier frequency is 15kHz. The motor used is a permanent magnet synchronous motor of model DVEV1G-200L-24, with a rated voltage of 380V and a rated frequency of 25Hz. The motor runs idle during the operation of the inverter system.

[0052] The common-mode voltage on the inverter output side was measured using an oscilloscope and a passive probe. The time-domain measurement results are shown in Figure 2(a). The peak-to-peak value of the common-mode voltage on the inverter output side in the time domain is U. CM,max The common-mode voltage is 552V; the common-mode voltage spectrum analysis results are shown in Figure 2(b). It can be seen that the large amplitude components of the inverter's common-mode voltage are mainly concentrated in the 15kHz to 2MHz frequency band, and at the switching frequency f sw The amplitude is maximum at 15kHz. Therefore, to suppress the common-mode voltage of the inverter system, the active filter used needs to have low-pass characteristics and a cutoff frequency less than 15kHz.

[0053] The active filter circuit topology designed in this invention is as follows: Figure 3 As shown, to analyze the transfer function of the active filter connected to the inverter system, the three-phase system needs to be simplified by equivalent calculation to a single phase. For the common-mode voltage source, since its three phases are equal in magnitude and direction, any phase can be analyzed. The passive network of the sampling stage can be equivalently represented by the series-parallel relationship. For the active amplification stage, since its voltage amplification factor is 1, only its current amplification capability is considered, and the current amplification factor of the power amplifier circuit is β. For the four-winding transformer of the common-mode voltage compensation stage, its single-phase equivalent process is as follows: Figure 4 (a) and Figure 4 As shown in (b), the spatial state equation of the four-winding transformer is:

[0054]

[0055] Based on the single-phase equivalent results, the single-phase equivalent circuit of the inverter system after connecting the active filter is as follows: Figure 5As shown, the transfer function of the active filter can be obtained as follows:

[0056]

[0057] Let λ = Z1 / Z2, and represent the passive network using an RLC series structure, i.e., Z1 = R1 + sL1 + 1 / sC1, then:

[0058]

[0059] To ensure that an active filter has low-pass characteristics, the following must be true:

[0060] (λ+3)βL2+L1-3βM=0

[0061] To ensure the active filter completely cancels common-mode noise at the inverter output, the system closed-loop gain is 1. This means the voltage division ratio of the voltage sampling stage should be the reciprocal of the amplification factor of the four-winding transformer.

[0062]

[0063]

[0064] After simplification, L1 = 0, meaning the passive network of the sampling stage cannot contain inductive components. Therefore, the transfer function of the system after the active filter is connected is:

[0065]

[0066] To avoid additional power loss due to the use of resistors, only capacitors are used in the sampling stage. Considering that the withstand voltage of complementary transistors on the market is generally below 400V, and the peak-to-peak time-domain value of the common-mode voltage U on the inverter output side... CM,max Since the voltage is 552V, the common-mode voltage sampling divider ratio n = 5 is chosen. The final parameters of the active filter components are shown in Tables 1 and 2. The structure and winding method of the four-winding transformer used in the common-mode voltage injection stage are as follows: Figure 6 (a) and Figure 6 As shown in (b), the corresponding parameters are shown in Table 3.

[0067] Table 1

[0068]

[0069] Table 2

[0070]

[0071] Table 3

[0072]

[0073] Based on the parameters of the active filter device, select the components and manufacture the physical prototype. The physical active filter prototype is shown below. Figure 7 (a) and Figure 7 As shown in (b). An active common-mode filter was connected to the inverter output port. The common-mode voltage of the system before and after the filter was connected is shown in Figure 8(a) and Figure 8(b). It can be seen that after the active filter was connected, the common-mode voltage on the inverter output side was significantly suppressed. The peak-to-peak value in the time domain decreased from 552V to 72V. The suppression of common-mode voltage in the 15kHz to 1MHz frequency band was about 40dB.

[0074] To demonstrate that the active filter designed in this invention has a better filtering effect on the common-mode voltage of the inverter output side, an active filter using only a push-pull circuit in the active amplification stage was set up as a control group during the experiment. Its circuit structure is as follows. Figure 9 As shown, the actual filter is as follows Figure 10 (a) and Figure 10 As shown in (b), its filtering effect is as follows: Figure 11 As shown in the figure. The spectral analysis comparing the common-mode voltage suppression performance of the two active filters is as follows. Figure 12 As shown, it can be seen that after the active filter without the voltage multiplier circuit is connected to the system, the peak-to-peak value of the system common-mode voltage in the time domain is reduced from 552V to 120V. However, the active filter with the voltage multiplier circuit can provide higher insertion loss in the range of 15kHz to 1MHz, thereby suppressing the system common-mode voltage to 72V.

[0075] Because the active filter designed in this invention contains a voltage multiplier before the power amplifier circuit, it can eliminate the crossover distortion problem caused by the push-pull circuit and increase the input impedance of the active amplifier stage, thus having a better common-mode voltage suppression effect.

[0076] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. Those skilled in the art can readily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A design method for an active common-mode interference filter in a high-voltage inverter system, comprising the following steps: (1) Measure the time-domain waveform of the common-mode voltage on the output side of the inverter, and then perform a fast Fourier transform on it to analyze the characteristics of the common-mode interference spectrum. Based on the test results, obtain the magnitude of the time-domain amplitude of the common-mode voltage and the main distribution frequency band of the common-mode interference. (2) An active common-mode interference filter is designed based on the active cancellation principle, which includes a common-mode voltage sampling stage, an active amplification stage, and a common-mode voltage compensation stage; The active amplification stage includes four voltage divider resistors. R 1~ R 4. Two NPN transistors T 1 and T 2. A PNP transistor T 3. DC filter capacitor C f And DC power supply, among which R One end of 1 and T The collector of 2 is connected in parallel with a DC bias voltage. V cc , R The other end of 1 and R One end of 2 T The collector of 1 and T The bases of 2 are connected. R The other end of 2 and R 3 at one end T 1 base and passive network Z Connect the neutral points of 1. R The other end of 3 and R 4 at one end T The emitter of 1 and T The base of 3 is connected. R The other end of 4 and T The collector of 3 is connected to and grounded. T 2's emitter and T The emitters of 3 are connected. T 2 and T 3. Form a push-pull circuit. C f The DC component of the push-pull circuit output is filtered, and the DC bias voltage is applied. V cc Powered by a DC power supply; (3) Analyze the single-phase equivalent circuit of the inverter system after the active common-mode interference filter is connected, calculate the transfer function of the active common-mode interference filter after it is connected to the system, and determine the relevant parameters; (4) Based on the device parameters and selection of the active common-mode interference filter, a physical fabrication was carried out, and the common-mode voltage on the output side of the inverter was tested after the active common-mode interference filter was connected to verify the suppression effect of the active common-mode interference filter on the common-mode interference of the inverter system.

2. The design method for an active common-mode interference filter in a high-voltage inverter system according to claim 1, characterized in that: In step (1), an oscilloscope and a passive probe are used to measure and perform spectrum analysis on the common-mode voltage of the inverter output side. The peak-to-peak value of the common-mode voltage in the time domain is: U CM,max The frequency point corresponding to the maximum common-mode voltage amplitude in the spectrum analysis results is the inverter switching frequency. f sw .

3. The design method for an active common-mode interference filter in a high-voltage inverter system according to claim 2, characterized in that: The common-mode voltage sampling stage includes three passive networks. Z 1 and a passive network Z 2. Three passive networks Z One end of 1 is connected to the three-phase output ports of the inverter to detect the common-mode voltage on the inverter output side. Three passive networks... Z The other end of 1 is connected in a star configuration and is connected to the passive network. Z 2. Perform voltage division, with a voltage division ratio of 1: n That is, neutral point and passive network Z One end of 2 is connected, passive network Z The other end of 2 is grounded; in: z 1 is a passive network Z The impedance value of 1 z 2 is a passive network Z Impedance value of 2, passive network Z 1 and Z Both adopt an RLC series structure.

4. The design method for an active common-mode interference filter in a high-voltage inverter system according to claim 1, characterized in that: The common-mode voltage compensation stage consists of a four-winding transformer wound on the same toroidal magnetic core, with one end of the primary winding of the transformer connected to... T The emitter of 2 is connected, and the other end is connected to C f One end is connected; the three secondary windings of the transformer are respectively connected in series on the three-phase line between the inverter output side and the motor; in order to achieve voltage multiplication injection of common mode voltage, the number of turns of the three secondary windings is equal and in a certain proportion to the number of turns of the primary winding.

5. The design method for an active common-mode interference filter in a high-voltage inverter system according to claim 3, characterized in that: To achieve complete elimination of the common-mode voltage on the inverter output side, the voltage division ratio of the common-mode voltage sampling stage should meet the following requirements: n = k , k This refers to the turns ratio of the secondary winding to the primary winding of the transformer in the common-mode voltage compensation stage.

6. The design method for an active common-mode interference filter in a high-voltage inverter system according to claim 4, characterized in that: The transfer function expression of the active common-mode interference filter after it is connected to the system in step (3) is as follows: in: H ( s Let be the transfer function of the active common-mode interference filter after it is connected to the system. V out ( s This is the frequency domain representation of the common-mode voltage on the inverter output side after the active common-mode interference filter is applied. V cm ( s This represents the frequency domain expression of the common-mode voltage on the inverter output side when no active common-mode interference filter is connected. s For the Laplace operator, ω n Let be the resonant angular frequency of the transfer function. Let be the damping coefficient of the transfer function. r 1 is a voltage divider resistor R The resistance value of 1 c 1 is a passive network Z The capacitance value in a 1-bit RLC series structure, c f DC filter capacitor C f The capacitance value, β The current amplification factor of the active amplification stage. l 2 represents the inductance value of the secondary winding of the transformer in the common-mode voltage compensation stage.

7. The design method for an active common-mode interference filter in a high-voltage inverter system according to claim 6, characterized in that: Guarantee the resonant frequency of the transfer function f n Less than the inverter switching frequency f sw , f n =ω n / 2π.

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