Current-sampling current-compensated differential-mode active emi filter and system

Abstract

The application discloses a current sampling current compensation differential mode active EMI filter and system, and belongs to the field of active EMI filters, and comprises: an injection circuit, an input end of which is connected with a DC bus, and a connection point is located between a LISN and a bus support capacitor; a current limiting auxiliary inductor, which is connected in series on the DC bus and is located between the LISN and the bus support capacitor; a sampling circuit, which is used for sampling an EMI interference source current between the LISN and a bridge arm of a power electronic converter, and performing integral processing on a corresponding induced voltage to obtain a voltage signal; a signal processing circuit, which is used for eliminating a DC bias in the voltage signal and adjusting the voltage signal to be matched with a phase, so as to obtain an injection voltage; and a power amplification circuit, which is used for performing power amplification on the injection voltage to obtain an injection current, and the injection circuit is used for converting the injection current into an injection current matched with the phase, and injecting the injection current into the DC bus to realize DC side differential mode EMI suppression. The application can improve the insertion loss and improve the suppression effect of the DC side differential mode EMI.

Description

Technical Field

[0001] This invention belongs to the field of active EMI filters, and more specifically, relates to a differential-mode active EMI filter and system with current sampling and current compensation. Background Technology

[0002] Electromagnetic interference (EMI) refers to unintended electromagnetic energy generated by electronic devices or systems during operation, through conduction or radiation. This energy can affect the normal operation of surrounding equipment, and may even lead to performance degradation or functional failure. With the rapid development of power electronics technology, especially the high-frequency and high-power applications of switching devices (such as MOSFETs and IGBTs), the rate of voltage and current change within equipment has increased dramatically, making EMI problems increasingly prominent. Based on different propagation paths, EMI is mainly divided into two categories: conducted interference (typically in the 150kHz to 30MHz frequency band) propagating through conductors such as power lines and signal lines; and radiated interference (typically in the frequency band above 30MHz) propagating through spatial coupling. In power management and automotive electronics applications, conducted interference is the most common and difficult-to-suppress form of noise.

[0003] Suppressing EMI is not only necessary to ensure stable equipment operation and improve the system signal-to-noise ratio, but also a prerequisite for meeting mandatory electromagnetic compatibility (EMC) standards. Traditional suppression methods typically employ passive EMI filters composed of capacitors and inductors. However, these filters are often bulky, have fixed parameters, and their effectiveness in suppressing low-frequency conducted interference is limited by the physical size of the inductors and capacitors, making it difficult to meet the high power density and integration requirements of modern electronic equipment. Active EMI filters, on the other hand, can effectively reduce conducted EMI in the mid-to-low frequency range, increase the cutoff frequency of passive filters, thereby reducing the size and weight of passive filters and effectively improving the power density of the system.

[0004] Active EMI (Electromagnetic Interference) filters work by actively sampling interference signals, processing them, and then generating a compensation signal to cancel the interference, thereby suppressing EMI. Based on the type of sampling and compensation signals, active EMI filters can be divided into four categories: current-sampling with current compensation, current-sampling with voltage compensation, voltage-sampling with voltage compensation, and voltage-sampling with current compensation. Among these, current-sampling with current compensation active EMI filters, because they detect interference current in the circuit and inject reverse compensation current to cancel noise, have advantages such as relatively simple control loops, good high-frequency noise compensation effect, and low oscillation risk, making them one of the mainstream solutions for suppressing conducted interference.

[0005] Existing active EMI filters suffer from two main problems while suppressing EMI interference. Firstly, like passive filters, their insertion loss is affected by impedance matching. In scenarios involving DC-side differential-mode EMI suppression, the insertion loss of conventional current-sampling and current-compensated active filters is unsatisfactory due to the presence of bus support capacitors. Secondly, the sampling and compensation stages of active filters also require the introduction of passive components. Current transformers are commonly used for current sampling, and transformers are frequently used for voltage compensation. However, their poor high-frequency characteristics limit the bandwidth of active filters, and the large size and weight of transformers also hinder improvements in power density and integration.

[0006] Overall, in scenarios involving the suppression of DC-side differential-mode EMI, the EMI suppression performance of existing current-sampling and current-compensated active EMI filters still needs further improvement. Summary of the Invention

[0007] In view of the shortcomings of the existing technology and the need for improvement, the present invention provides a differential-mode active EMI filter and system with current sampling and current compensation. Its purpose is to improve the insertion loss of the current sampling and current compensation type active EMI filter, thereby improving the suppression effect of DC-side differential-mode EMI.

[0008] To achieve the above objectives, according to one aspect of the present invention, a differential-mode active EMI filter with current sampling and current compensation is provided for suppressing DC-side differential-mode EMI in a power electronic converter, comprising: a current-limiting auxiliary inductor. Sampling circuit, signal processing circuit, power amplifier circuit and injection circuit;

[0009] The output terminal of the injection circuit is connected to the DC bus, forming a connection point. Connection point LISN and bus support capacitor located in power electronic converter between;

[0010] Current-limiting auxiliary inductor Connected in series with the DC bus and located at the connection point With bus support capacitor between;

[0011] The sampling circuit is used to sample the EMI interference source current at a preset sampling point on the DC bus. and the EMI interference source current The corresponding induced voltage is integrated to obtain a voltage signal. The preset sampling point is located at the bus support capacitor. Between the bridge arm and the power electronic converter;

[0012] The input terminal of the signal processing circuit is connected to the output terminal of the sampling circuit to eliminate voltage signals. After the DC bias generated by the integral is applied, its magnitude is adjusted to match the current of the EMI interference source. Matching to obtain the injection voltage ;

[0013] The input terminal of the power amplifier circuit is connected to the output terminal of the signal processing circuit to process the injected voltage. Power amplification is performed to obtain the injection voltage. ;

[0014] The input terminal of the injection circuit is connected to the output terminal of the power amplifier circuit to convert the injected voltage. Converted to current from EMI interference sources Matching injection current It is injected into the DC bus to achieve DC-side differential mode EMI suppression.

[0015] Furthermore, the sampling circuit includes: One PCB Rogowski coil, Damping resistor and integrator; This refers to the number of bridge arms connected in parallel with the DC bus in a power electronic converter.

[0016] A PCB Rogowski coil is connected in parallel with the DC bus in the power electronic converter. Each bridge arm is connected accordingly; each PCB Rogowski coil includes two sub-coils connected in series. The two sub-coils have the same size and number of turns, but are wound in opposite directions and are connected to the positive DC terminal and negative DC terminal of the corresponding bridge arm, respectively.

[0017] Each PCB Rogowski coil is connected to a damping resistor. in parallel; The PCB Rogowski coils are connected in series, and their two ends are connected to the integrator. The output of the integrator is the output of the sampling circuit.

[0018] Furthermore, the low-frequency cutoff frequency of the integrator .

[0019] Furthermore, the signal processing circuit includes: a first high-pass filter and a non-inverting amplifier;

[0020] The input terminal of the first high-pass filter is the input terminal of the signal processing circuit and is connected to the output terminal of the sampling circuit; the high-pass filter is used to eliminate voltage signals. DC bias generated by the integral;

[0021] The input terminal of the inverting amplifier is connected to the output terminal of the first high-pass filter, and the output terminal of the inverting amplifier is the output terminal of the signal processing circuit; the inverting amplifier is used to process the voltage signal after DC bias elimination. Adjust the size to match the EMI interference source current. Matching to obtain the injection voltage .

[0022] Furthermore, the cutoff frequency of the first high-pass filter .

[0023] Furthermore, the injection circuit includes an injection capacitor. and injection resistance A second high-pass filter formed by cascading;

[0024] Furthermore, the gain of the in-phase amplifier satisfy: ;

[0025] in, This represents the mutual inductance corresponding to each sub-coil in the PCB Rogowski coil; and These represent the resistor and capacitor in the integrator, respectively. This represents the parasitic inductance of the busbar support capacitor.

[0026] Furthermore, injecting capacitors It is a safety-certified X capacitor.

[0027] Furthermore, the cutoff frequency of the second high-pass filter .

[0028] According to another aspect of the present invention, a power electronic converter system is provided, comprising a power electronic converter and a differential-mode active EMI filter with current sampling and current compensation provided by any of the above-mentioned current-sampling and current-compensated methods of the present invention.

[0029] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0030] (1) The differential-mode active EMI filter with current sampling and current compensation provided by the present invention has a current-limiting auxiliary resistor set near the power supply side, and the current sampling point is close to the converter side (located at the bus support capacitor). Between the bridge arm of the power electronic converter, its insertion loss is only related to the feedforward coefficient and is not affected by the impedance characteristics. This effectively improves the insertion loss of the current sampling current compensation type active EMI filter, thereby improving the suppression effect of DC side differential mode EMI.

[0031] (2) In the preferred embodiment of the differential mode active EMI filter with current sampling and current compensation provided by the present invention, current limiting sampling using PCB Rogowski coil can increase the integration of the active EMI filter while ensuring accurate sampling current, thereby improving the power density of the system.

[0032] (3) In the preferred embodiment of the differential-mode active EMI filter with current sampling and current compensation provided by the present invention, the low-frequency cutoff frequency of the integrator in the current sampling circuit is less than 15kHz, which can effectively suppress conducted EMI.

[0033] (4) In the preferred embodiment of the differential-mode active EMI filter with current sampling and current compensation provided by the present invention, the cutoff frequency of the high-pass filter in the signal processing circuit is less than 15kHz, which can effectively suppress conducted EMI.

[0034] (5) In a preferred embodiment of the differential-mode active EMI filter with current sampling and current compensation provided by the present invention, the gain of the in-phase amplifier in the signal processing circuit satisfies This ensures the total current injected into the system. Matching the actual interference source current further improves the DC-side differential mode EMI suppression effect.

[0035] (6) In the preferred embodiment of the differential-mode active EMI filter with current sampling and current compensation provided by the present invention, the cutoff frequency of the high-pass filter in the signal injection circuit is less than 15kHz, which can effectively suppress conducted EMI. Attached Figure Description

[0036] Figure 1 A schematic diagram of a differential-mode active EMI filter with current sampling and current compensation provided by the present invention.

[0037] Figure 2 This is the circuit diagram of an existing dual active bridge converter.

[0038] Figure 3 The invention provides an embodiment for suppressing Figure 2 The diagram shows a differential active EMI filter for current sampling and compensation of DC-side differential EMI in a dual active bridge converter.

[0039] Figure 4 The differential-mode equivalent circuit for current sampling and current compensation provided in the embodiments of the present invention.

[0040] Figure 5 The differential-mode equivalent circuit for current sampling and current compensation is provided for the existing current sampling current.

[0041] Figure 6 A schematic diagram of a PCB Rogowski coil provided in an embodiment of the present invention.

[0042] Figure 7 A comparison chart showing the suppression effect of the differential-mode active EMI filter provided by this invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0044] In this invention, the terms "first," "second," etc. (if present) in the invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0045] To improve the insertion loss of current-sampling and current-compensated active EMI filters and thus enhance the suppression of DC-side differential-mode EMI, this invention provides a current-sampling and current-compensated differential-mode active EMI filter and system. Based on a feedforward current-sampling and current-compensated topology, it optimizes the current sampling position, overcomes the drawback of insertion loss being affected by impedance characteristics, and improves the suppression of DC-side differential-mode EMI.

[0046] Based on the above concepts, the differential-mode active EMI filter with current sampling and current compensation provided by this invention is as follows: Figure 1 As shown, a method for suppressing DC-side differential-mode EMI in a power electronic converter is characterized by comprising: a current-limiting auxiliary inductor. Sampling circuit, signal processing circuit, power amplifier circuit and injection circuit;

[0047] The output terminal of the injection circuit is connected to the DC bus, forming a connection point. Connection point LISN and bus support capacitor located in power electronic converter between;

[0048] Current-limiting auxiliary inductor Connected in series with the DC bus and located at the connection point With bus support capacitor between;

[0049] The sampling circuit is used to sample the EMI interference source current at a preset sampling point on the DC bus. and the EMI interference source current The corresponding induced voltage is integrated to obtain a voltage signal. The preset sampling point is located at the bus support capacitor. Between the bridge arm and the power electronic converter;

[0050] The input terminal of the signal processing circuit is connected to the output terminal of the sampling circuit to eliminate voltage signals. After the DC bias generated by the integral is applied, its magnitude is adjusted to match the current of the EMI interference source. Matching to obtain the injection voltage ;

[0051] The input terminal of the power amplifier circuit is connected to the output terminal of the signal processing circuit to process the injected voltage. Power amplification is performed to obtain the injection voltage. ;

[0052] The input terminal of the injection circuit is connected to the output terminal of the power amplifier circuit to convert the injected voltage. Converted to current from EMI interference sources Matching injection current It is injected into the DC bus to achieve DC-side differential mode EMI suppression.

[0053] The LISN (line impedance stabilization network) is used to isolate interference introduced by the DC power supply and provide stable impedance. It is a common structure in power electronic converters located near the power supply side.

[0054] Building upon the above concepts, this invention further employs a PCB Rogowski coil instead of a current transformer for sampling, thereby increasing integration and power density while balancing suppression bandwidth and power density. Accordingly, as... Figure 1 As shown, the sampling circuit includes: One PCB Rogowski coil, Damping resistor and integrator; This refers to the number of bridge arms connected in parallel with the DC bus in a power electronic converter.

[0055] A PCB Rogowski coil is connected in parallel with the DC bus in the power electronic converter. Each bridge arm is connected accordingly; each PCB Rogowski coil includes two sub-coils connected in series. The two sub-coils have the same size and number of turns, but are wound in opposite directions and are connected to the positive DC terminal and negative DC terminal of the corresponding bridge arm, respectively.

[0056] Each PCB Rogowski coil is connected to a damping resistor. in parallel; The PCB Rogowski coils are connected in series, and their two ends are connected to the integrator. The output of the integrator is the output of the sampling circuit.

[0057] This invention is applicable to differential-mode EMI suppression in converters with DC buses, and offers strong portability and scalability. Without loss of generality, the following embodiments use a dual active bridge converter as an example for explanation and illustration.

[0058] The following is an example.

[0059] Example 1:

[0060] A differential-mode active EMI filter with current sampling and current compensation is used to suppress DC-side differential-mode EMI in a dual active bridge power electronic converter.

[0061] The topology of a dual active bridge power electronic converter is as follows: Figure 2 As shown, it is through a single-sided phase-shifting inductor and high-frequency isolation transformer The transformer consists of two full-bridge circuits connected to each other on the primary and secondary sides. The turns ratio of the secondary voltage to the primary voltage is: , and These represent the number of turns on the secondary and primary sides of the transformer, respectively. and These represent the DC bus voltages of the primary and secondary sides, respectively, which are the input voltage and the output voltage. and These represent the DC-side capacitors for the input and output, respectively. Figure 2 The dual active bridge power electronic converter shown contains two bridge arms on its input side, each arm being a two-level half-bridge module, while the phase-shifting inductor... ,transformer And the overall generalized load formed by the secondary-side full bridge. This embodiment suppresses differential-mode interference on the input DC side, and the input capacitor... That is Figure 1 The supporting capacitor shown .

[0062] To suppress Figure 2 The differential-mode EMI on the input DC side of the dual active bridge power electronic converter shown is as follows: Figure 3 As shown, this embodiment includes:

[0063] Current-limiting auxiliary inductor Sampling circuit, signal processing circuit, power amplifier circuit and injection circuit;

[0064] The output terminal of the injection circuit is connected to the DC bus, forming a connection point. Connection point LISN and bus support capacitor located in power electronic converter between;

[0065] Current-limiting auxiliary inductor Connected in series with the DC bus and located at the connection point With bus support capacitor between;

[0066] The sampling circuit is used to sample the EMI interference source current at a preset sampling point on the DC bus. and the EMI interference source current The corresponding induced voltage is integrated to obtain a voltage signal. The preset sampling point is located at the bus support capacitor. Between the bridge arm and the power electronic converter;

[0067] The input terminal of the signal processing circuit is connected to the output terminal of the sampling circuit to eliminate voltage signals. After the DC bias generated by the integral is applied, its magnitude is adjusted to match the current of the EMI interference source. Matching to obtain the injection voltage ;

[0068] The input terminal of the power amplifier circuit is connected to the output terminal of the signal processing circuit to process the injected voltage. Power amplification is performed to obtain the injection voltage. ;

[0069] The input terminal of the injection circuit is connected to the output terminal of the power amplifier circuit to convert the injected voltage. Converted to current from EMI interference sources Matching injection current It is injected into the DC bus to achieve DC-side differential mode EMI suppression.

[0070] The following is about current-limiting auxiliary inductors The specific implementation and working principle of the current sampling circuit, signal processing circuit, power amplification circuit, and injection circuit will be further explained.

[0071] Current-limiting auxiliary inductor Connected in series with the DC bus, it serves to limit the amplitude of the compensation current. In the conducted EMI frequency band, the DC bus has low capacitive impedance, thus limiting the parasitic inductance of the bus support capacitor. Playing a leading role, a current-limiting auxiliary inductor is introduced. The actual interference source current that needs to be compensated later for: .

[0072] Due to the bus support capacitor The parasitic inductance is in the nanohenry class, therefore the current-limiting auxiliary inductor The amplitude of the compensation current can be significantly reduced with only microhenries.

[0073] Figure 3 The topology shown can be simplified to Figure 4 The equivalent circuit shown here has the differential-mode current insertion loss expressed as: , This represents the overall feedforward coefficient of the system. In an ideal situation, .

[0074] Therefore, in this embodiment, by optimizing the current sampling position, the insertion loss of the differential-mode active EMI filter with current sampling and compensation is only related to the feedforward coefficient and is not affected by the impedance characteristics. Thus, by adjusting the feedforward coefficient (for example, ensuring that the feedforward coefficient is close to 1), a larger insertion loss can be achieved, effectively suppressing DC-side differential-mode EMI interference.

[0075] Traditional current-sampling and current-compensated active EMI filters have their current sampling location close to the power supply side (between the power supply and the bus support capacitor), and their equivalent circuit is as follows: Figure 5 As shown, the corresponding insertion loss is: ,in, This is the equivalent impedance of the DC bus. This is the equivalent impedance of the LISN.

[0076] Therefore, it can be seen that the insertion loss of traditional current-sampling current-compensated active EMI filters is affected not only by the feedforward coefficient but also by the impedance characteristics.

[0077] As can be seen from the insertion loss comparison, this embodiment optimizes the sampling position, sampling the interference source current closer to the converter side. rather than the current closer to the power source. It can effectively eliminate the influence of circuit impedance matching on insertion loss and suppress differential-mode active EMI.

[0078] As a preferred embodiment, this example uses a PCB Rogowski coil instead of a current transformer for sampling, such as... Figure 3 As shown, in this embodiment, the sampling circuit includes: two PCB Rogowski coils and two damping resistors. and integrator;

[0079] like Figure 6 As shown, the two PCB Rogowski coils are connected to the two bridge arms in parallel with the DC bus in the power electronic converter. Each PCB Rogowski coil includes two sub-coils connected in series (i.e., sub-coil 1 and sub-coil 2). The two sub-coils have the same size and number of turns, and the winding directions are opposite. They are connected to the positive DC terminal and negative DC terminal of the corresponding bridge arm, respectively.

[0080] Each PCB Rogowski coil is connected to a damping resistor. Parallel connection; after the two PCB Rogowski coils are connected in series, their two ends are connected to the integrator, and the output of the integrator is the output of the sampling circuit.

[0081] The two sub-coils in each PCB Rogowski coil generate an induced voltage in response to the current at the positive DC terminal P and the negative DC terminal N. / and / Two Rogowski coils connected in parallel with a damping resistor Then they are connected in series to obtain the differential mode current. The corresponding induced voltage. The total input induced voltage of the sampling circuit. The following relationship must be satisfied:

[0082] ;

[0083] in, The mutual inductance corresponding to each sub-coil can be measured and obtained using equipment such as a loop analyzer. Indicates time. PCB Rogowski coils have high integration density and low mutual inductance, ensuring accurate current sampling without affecting normal circuit operation, thus improving integration density.

[0084] The integrator is induced by the input voltage. The voltage signal is obtained by integration. Corresponding to the integrator, in this embodiment, the signal processing circuit includes: a first high-pass filter and a non-inverting amplifier;

[0085] The input terminal of the first high-pass filter is the input terminal of the signal processing circuit and is connected to the output terminal of the sampling circuit; the high-pass filter is used to eliminate voltage signals. DC bias generated by the integral;

[0086] The input terminal of the inverting amplifier is connected to the output terminal of the first high-pass filter, and the output terminal of the inverting amplifier is the output terminal of the signal processing circuit; the inverting amplifier is used to process the voltage signal after DC bias elimination. Adjust the size to match the EMI interference source current. Matching to obtain the injection voltage .

[0087] Optionally, in this embodiment, the integrating circuit is a hybrid integrator, designed for the frequency band of concern for conducted EMI (150kHz~30MHz). , and These represent the resistance and capacitance of the passive part of the integrator, respectively. Indicates the grounding resistance of the integrator. This represents the parallel capacitor in the feedback branch of the integrator. The integrated voltage and the induced voltage satisfy the following relationship:

[0088] ;

[0089] in, The variable is represented by Laplace, and its derivative is represented in the transfer function.

[0090] In this embodiment, the low-frequency cutoff frequency of the integrator is , This represents the parallel resistance of the integrator's feedback branch. To accurately reproduce interference signals within the frequency band of interest for conducted EMI (150kHz~30MHz), f 1 should be small enough; specifically, in this embodiment, .

[0091] The first high-pass filter applies voltage signals. A high-pass filter is applied to eliminate the DC bias generated by the integrator. The cutoff frequency of the first high-pass filter is... , and These represent the resistor and capacitor of the first high-pass filter, respectively. To accurately reproduce interference signals within the frequency band of interest for conducted EMI (150kHz~30MHz), the cutoff frequency of the high-pass filter is... f 2 should be small enough; specifically, in this embodiment, the cutoff frequency of the first high-pass filter. .

[0092] The filtered voltage is then processed by a non-inverting amplifier to obtain the injection voltage. In order to ensure the total current injected into the system To match the actual interference source current, in this embodiment, the gain of the in-phase amplifier satisfies:

[0093] ;

[0094] in, and These represent the grounding resistance and feedback resistance of the in-phase amplifier, respectively. This represents the injection resistance in the injection circuit.

[0095] In this embodiment, the power amplifier circuit consists of a buffer and a push-pull circuit. Optionally, the push-pull circuit uses multiple AB-class amplifier circuits connected in parallel to ensure the output current amplitude and current gain.

[0096] In this embodiment, the injection circuit includes an injection capacitor. and injection resistance A second high-pass filter is formed by cascading. Optionally, in this embodiment, an injection capacitor... For safety-certified capacitors (X-level), the capacitance value is much smaller than that of the bus capacitor; generally, a value in the microfarad range is sufficient.

[0097] Injection capacitor and injection resistance The cutoff frequency of the second high-pass filter formed by cascading is To ensure effective suppression of conducted EMI, in this embodiment, the cutoff frequency of the second high-pass filter is sufficiently small. Specifically, the cutoff frequency of the second high-pass filter is... .

[0098] Overall, compared to traditional current-sampling and current-compensated filters, this embodiment improves the insertion loss of current-sampling and current-compensated topologies and enhances suppression performance by changing the sampling point location so that the insertion loss is not affected by circuit impedance matching. Furthermore, by using PCB Rogowski coils for current sampling, the integration of the filter is increased, which helps to improve the power density of the system.

[0099] This solution is applicable to differential-mode EMI suppression in converters with a DC bus, and it offers strong portability and scalability. It's easy to understand that when the number of bridge arms connected in parallel with the DC bus in the power electronic converter changes, the number of Rogowski coils on the PCB of the current sampling circuit can be modified accordingly.

[0100] The following analysis further verifies the beneficial effects of this invention by comparing the differential-mode EMI under different operating conditions. Specifically, three operating conditions are considered: the original circuit corresponding to the differential-mode active EMI filter without current sampling and current compensation; the differential-mode active EMI filter with current sampling and current compensation provided in this embodiment but not in operation; and the differential-mode active EMI filter with current sampling and current compensation provided in this embodiment and in operation. The comparison of differential-mode EMI under these three different operating conditions is as follows. Figure 7 As shown. According to Figure 7 The comparison results show that the current-sampling and current-compensated differential-mode active EMI filter provided in this embodiment can effectively suppress EMI in the range of 150kHz to 1MHz, with a maximum suppression effect of up to 20dB. This result demonstrates that this embodiment can balance suppression bandwidth and power density.

[0101] Example 2:

[0102] A power electronic converter system includes a power electronic converter and a differential-mode active EMI filter with current sampling and current compensation provided in Embodiment 1 above.

[0103] In this embodiment, the connection method of the power electronic converter and the differential active EMI filter can be referred to the description in Embodiment 1 above, and will not be repeated here.

[0104] Those skilled in the art will readily understand that the above description is merely 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 within the scope of protection of the present invention.

Claims

1. A differential-mode active EMI filter with current sampling and current compensation, used to suppress DC-side differential-mode EMI in power electronic converters, characterized in that, include: Current-limited auxiliary inductor , a sampling circuit, a signal processing circuit, a power amplification circuit and an injection circuit; The output terminal of the injection circuit is connected to the DC bus, forming a connection point. The connection point The LISN and bus support capacitor located in the power electronic converter between; The current limiting auxiliary inductor is connected in series with the DC bus and is located at the connection point with the bus support capacitor between; The sampling circuit is used for sampling EMI interference source current at a preset sampling point on the DC bus , and the EMI interference source current is integrated to obtain a voltage signal ; the preset sampling point is located between the bus support capacitor and the bridge arm of the power electronic converter The input terminal of the signal processing circuit is connected to the output terminal of the sampling circuit to eliminate voltage signals. After the DC bias generated by the integral is applied, its magnitude is adjusted to match the current of the EMI interference source. Matching to obtain the injection voltage ; The input terminal of the power amplifier circuit is connected to the output terminal of the signal processing circuit, and is used to process the injected voltage. Power amplification is performed to obtain the injection voltage. ; The input terminal of the injection circuit is connected to the output terminal of the power amplifier circuit, and is used to inject the voltage. Converted to current from EMI interference sources Matching injection current And injected into the DC bus to achieve DC-side differential mode EMI suppression.

2. The differential-mode active EMI filter with current sampling and current compensation as described in claim 1, characterized in that, The sampling circuit includes: One PCB Rogowski coil, Damping resistor and integrator; The number of bridge arms in the power electronic converter that are connected in parallel with the DC bus; The Each PCB Rogowski coil is connected in parallel with the DC bus in the power electronic converter. Each bridge arm is connected accordingly; each PCB Rogowski coil includes two sub-coils connected in series. The two sub-coils have the same size and number of turns, and are wound in opposite directions. They are respectively connected to the positive DC terminal and negative DC terminal of the corresponding bridge arm. Each of the PCB Rogowski coils is coupled with a damping resistor. Parallel connection; the aforementioned After the PCB Rogowski coils are connected in series, their two ends are respectively connected to the integrator, and the output of the integrator is the output of the sampling circuit.

3. The differential-mode active EMI filter with current sampling and current compensation as described in claim 2, characterized in that, The low-frequency cutoff frequency of the integrator .

4. The differential-mode active EMI filter with current sampling and current compensation as described in claim 2, characterized in that, The signal processing circuit includes: a first high-pass filter and a non-inverting amplifier; The input terminal of the first high-pass filter is the input terminal of the signal processing circuit and is connected to the output terminal of the sampling circuit; the high-pass filter is used to eliminate voltage signals. DC bias generated by the integral; The input terminal of the in-phase amplifier is connected to the output terminal of the first high-pass filter, and the output terminal of the in-phase amplifier is the output terminal of the signal processing circuit; the in-phase amplifier is used to process the voltage signal after DC bias elimination. Adjust the size to match the EMI interference source current. Matching to obtain the injection voltage .

5. The differential-mode active EMI filter with current sampling and current compensation as described in claim 4, characterized in that, The cutoff frequency of the first high-pass filter .

6. The differential-mode active EMI filter with current sampling and current compensation as described in claim 4, characterized in that, The injection circuit includes an injection capacitor. and injection resistance A second high-pass filter formed by cascading; Furthermore, the gain of the in-phase amplifier satisfy: ; in, This represents the mutual inductance corresponding to each sub-coil in the PCB Rogowski coil; and These represent the resistor and capacitor in the integrator, respectively. Indicates the busbar support capacitor Parasitic inductance.

7. The differential-mode active EMI filter with current sampling and current compensation as described in claim 6, characterized in that, The injection capacitor It is a safety-certified X capacitor.

8. The differential-mode active EMI filter with current sampling and current compensation as described in claim 6, characterized in that, The cutoff frequency of the second high-pass filter .

9. A power electronic converter system, characterized in that, Includes power electronic converters and differential-mode active EMI filters with current sampling and current compensation as described in any one of claims 1 to 8.

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