A cascaded active EMI filter and converter system based on component reuse

Abstract

The application discloses a kind of based on element multiplexing cascaded active EMI filter and converter system, comprising: feedforward current compensation EMI filter and feedback current compensation EMI filter;Two kinds of filters share a power supply circuit and current sensing circuit and all include the same voltage amplifier circuit, power amplifier circuit and output impedance circuit;Current sensing circuit input end is connected with the positive and negative bus of power electronic converter, and output end is connected with the input end of voltage amplifier circuit;Voltage amplifier circuit output end is connected with the input end of power amplifier circuit, and power amplifier circuit output end is connected with output impedance;The output end of output impedance is connected with DC negative bus;Current sensing circuit is used to sense common-mode current and output same voltage signal to voltage amplifier circuit;Voltage amplifier circuit is used to amplify voltage signal and output to power amplifier circuit;Power amplifier circuit outputs amplified voltage signal to output impedance circuit;Output impedance circuit is used to convert amplified voltage signal into current signal, and offset with system common-mode current;The feedforward current compensation EMI filter and feedback current compensation EMI filter designed in the application share current sensing circuit, power supply circuit and operational amplifier, can well inhibit the common-mode EMI of converter system low frequency, reduce the size of cascaded active EMI filter, reduce the cost of EMI filter.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of EMI suppression of power electronic devices, and particularly relates to a cascaded active EMI filter based on element reuse and a converter system. BACKGROUND

[0002] Power electronic converters are widely used due to their superior performance, but the high-speed switching of power electronic converters can cause serious electromagnetic interference. Electromagnetic interference can seriously affect the reliable operation of the converter system, and with the development of wide-bandgap semiconductor devices, the EMI problem is becoming more and more serious. In order to ensure the reliable operation of the system, the electromagnetic interference generated thereby must be suppressed, and the electromagnetic interference value must be limited within the range specified in the standard.

[0003] Common-mode electromagnetic interference is usually suppressed by using a common-mode EMI filter in engineering, but the passive EMI filter is relatively large in size, so in order to reduce the size of the EMI filter, an active EMI filter is used, but the suppression effect of a single active EMI filter is limited, and in order to improve the suppression effect, the existing method uses cascaded active EMI, but the existing cascaded active EMI filter is usually large in size, increasing the design cost. SUMMARY

[0004] The present application provides a cascaded active EMI filter based on element reuse and a converter system to overcome the technical problems of the existing cascaded active EMI filter, which is large in size and high in design cost.

[0005] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0006] A cascaded active EMI filter based on element reuse is connected with a power electronic converter and a line impedance stabilization network, and comprises a power supply circuit, a feedforward current compensation EMI filter and a feedback current compensation EMI filter.

[0007] The feedforward current compensation EMI filter comprises a first voltage amplification circuit, a first power amplification circuit Q1 and a first output impedance circuit; the feedback current compensation EMI filter comprises a second voltage amplification circuit, a second power amplification circuit Q2, a second output impedance circuit and shares a current sensing circuit and a power supply circuit with the feedforward current compensation EMI filter.

[0008] The power supply circuit is connected with the feedforward current compensation EMI filter and the feedback current compensation EMI filter.

[0009] The input end of the current sensing circuit is connected with the positive and negative bus of the power electronic converter, and the output end is connected with the input end of the first voltage amplification circuit and the second voltage amplification circuit respectively; the output end of the first voltage amplification circuit is connected with the input end of the first power amplification circuit Q1, and the output end of the first power amplification circuit Q1 is connected with the first output impedance; the output end of the first output impedance is connected with the DC negative bus; the output end of the second voltage amplification circuit is connected with the input end of the second power amplification circuit Q2, and the output end of the second power amplification circuit Q2 is connected with the second output impedance; the output end of the second output impedance is connected with the DC negative bus.

[0010] The current sensing circuit is used for sensing the common-mode current of the line impedance stabilization network and outputting the same voltage signal to two voltage amplification circuits; the two voltage amplification circuits are used for amplifying the voltage signal output by the current sensing circuit and outputting the amplified voltage signal to two power amplification circuits respectively; the two power amplification circuits are used for outputting the amplified voltage signal to two output impedance circuits respectively; and the two output impedance circuits are used for converting the amplified voltage signal into a current signal to offset the common-mode current in the converter system.

[0011] Further, the current sensing circuit comprises a current transformer and a first resistor R1.

[0012] The primary side winding L1 of the current transformer is connected with the power electronic converter, and the secondary side winding L2 of the current transformer is connected with the first resistor R1; one end of the first resistor R1 is connected with the ground.

[0013] Further, the first voltage amplification circuit and the second voltage amplification circuit have the same structure and share a double-channel operational amplifier U1, the operational amplifier U1 comprises a first-channel operational amplifier U 1.1 and a second-channel operational amplifier U 1.2 ; the first voltage amplification circuit comprises a second resistor R2 and a third resistor R3, and the second voltage amplification circuit comprises a fourth resistor R4 and a fifth resistor R5.

[0014] One end of the second resistor R2, one end of the third resistor R3 and the inverting input of the first-channel operational amplifier U 1.1 are connected; the other end of the second resistor R2 is connected with the ground.

[0015] One end of the fourth resistor R4, one end of the fifth resistor R5 and the inverting input of the second-channel operational amplifier U 1.2 are connected; the other end of the fourth resistor R4 is connected with the ground.

[0016] The two non-inverting input terminals of the operational amplifier U1 are connected to the other end of the first resistor R1; the positive voltage input terminal of the operational amplifier U1 is connected to the +V CC of the power supply; the negative voltage input terminal of the operational amplifier U1 is connected to the -V CC of the power supply.

[0017] Further, the first power amplifier circuit Q1 and the second power amplifier circuit Q2 are of the same structure, the first power amplifier circuit Q1 comprises a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a first triode T1, a second triode T2, a first diode D1 and a second diode D2; the second power amplifier circuit Q2 comprises an eleventh resistor R 11 , a twelfth resistor R 12 , a thirteenth resistor R 13 , a fourteenth resistor R 14 , a third triode T3, a fourth triode T4, a third diode D3 and a fourth diode D4;

[0018] One end of the sixth resistor R6 is connected to the collector of the first triode T1 and the +V CC of the power supply respectively; the other end of the sixth resistor R6, the base of the first triode T1 and the anode of the first diode D1 are connected; the cathode of the first diode D1 is connected to the output terminal of the first channel operational amplifier U 1.1 and the anode of the second diode D2 respectively; the cathode of the second diode D2, one end of the seventh resistor R7 and the base of the second triode T2 are connected; the other end of the seventh resistor R7, the collector of the second triode T2 and the -V CC of the power supply are connected; the emitter of the first triode T1 is connected to one end of the eighth resistor R8; the emitter of the second triode T2 is connected to one end of the ninth resistor R9; the other end of the eighth resistor R8, the other end of the ninth resistor R9 and the other end of the third resistor R3 are connected;

[0019] One end of the eleventh resistor R 11 is connected to the collector of the third triode T3 and the +V CC of the power supply respectively; the other end of the eleventh resistor R 11 , the base of the third triode T3 and the anode of the third diode D3 are connected; the cathode of the third diode D3 is connected to the output terminal of the second channel operational amplifier U 1.2 and the anode of the fourth diode D4 respectively; the cathode of the fourth diode D4, one end of the twelfth resistor R 12One end of the twelfth resistor R is connected to the base of the fourth transistor T4; 12 The other end of the fourth transistor T4, the collector and the -V CC The emitter of the third transistor T3 and the thirteenth resistor R 13 The emitter of the fourth transistor T4 and the fourteenth resistor R 14 The thirteenth resistor R 13 The other end of the fourteenth resistor R 14 The other end of is connected to the other end of the fifth resistor R5.

[0020] Furthermore, the first output impedance circuit and the second output impedance circuit have the same structure, and the first output impedance circuit includes a tenth resistor R 10 and a first capacitor C1; the second output impedance circuit includes a fifteenth resistor R 15 and a second capacitor C2;

[0021] The tenth resistor R 10 One end of the tenth resistor R is connected to the other end of the eighth resistor R8 and the other end of the ninth resistor R9; 10 The other end of is connected to one end of the first capacitor C1; the other end of the first capacitor C1 is connected to the negative bus;

[0022] The fifteenth resistor R 15 One end of each resistor R 13 The other end and the fourteenth resistor R 14 The other end of the fifteenth resistor R 15 The other end of is connected to one end of the second capacitor C2; the other end of the second capacitor C2 is connected to the negative bus.

[0023] Furthermore, the first transistor T1 and the third transistor T3 are of NPN structure; the second transistor T2 and the fourth transistor T4 are of PNP structure.

[0024] Furthermore, it also includes a power electronic converter system, which includes the cascaded active EMI filter based on component reuse.

[0025] Beneficial effects: The present invention provides a cascaded active EMI filter based on component reuse. By designing a feedforward current compensated EMI filter and a feedback current compensated EMI filter, and sharing a current sensing circuit and a power supply circuit, the low-frequency common-mode EMI of the converter system can be effectively suppressed, while reducing the volume of the cascaded active EMI filter and the cost of the EMI filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0027] Figure 1 It is a schematic diagram of a general power electronic converter system;

[0028] Figure 2 It is a schematic diagram of a cascaded active EMI filter based on component reuse in the present application;

[0029] Figure 3 It is a schematic diagram of a first power amplification circuit in the present application;

[0030] Figure 4 It is a schematic diagram of a second power amplification circuit in the present application;

[0031] Figure 5 It is an equivalent circuit diagram of a cascaded active EMI filter based on component reuse;

[0032] In the figure, Q1, first power amplification circuit; Q2, second power amplification circuit. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort are within the protection scope of the present application.

[0034] The present embodiment provides a cascaded active EMI filter based on component reuse, as shown in Figure 2 connected with a power electronic converter and a line impedance stabilization network, including a power supply circuit, a feedforward current compensation EMI filter and a feedback current compensation EMI filter;

[0035] The feedforward current compensation EMI filter includes a first voltage amplification circuit, a first power amplification circuit Q1 and a first output impedance circuit; the feedback current compensation EMI filter includes a second voltage amplification circuit, a second power amplification circuit Q2, a second output impedance circuit and shares a current sensing circuit and a power supply circuit with the feedforward current compensation EMI filter;

[0036] The power supply circuit is connected with the feedforward current compensation EMI filter and the feedback current compensation EMI filter;

[0037] The input end of the current sensing circuit is connected with the positive and negative bus of the power electronic converter, and the output end is connected with the input end of the first voltage amplification circuit and the second voltage amplification circuit respectively; the output end of the first voltage amplification circuit is connected with the input end of the first power amplification circuit Q1, and the output end of the first power amplification circuit Q1 is connected with the first output impedance; the output end of the first output impedance is connected with the negative DC bus; the output end of the second voltage amplification circuit is connected with the input end of the second power amplification circuit Q2, and the output end of the second power amplification circuit Q2 is connected with the second output impedance; the output end of the second output impedance is connected with the negative DC bus;

[0038] The current sensing circuit is used for sensing the common mode current of the line impedance stabilization network and outputting the same voltage signal to two voltage amplification circuits; the two voltage amplification circuits are used for amplifying the voltage signal output by the current sensing circuit and outputting the amplified voltage signal to two power amplification circuits respectively; the two power amplification circuits are used for outputting the amplified voltage signal to two output impedance circuits respectively and providing additional current to improve the current output capability; the two output impedance circuits are used for converting the amplified voltage signal into current signal to offset the common mode current in the converter system.

[0039] Specifically, the current sensing circuit in the cascaded active EMI filter detects the common-mode current in the line impedance stabilization network, the cancellation current output by the feed-forward current compensation EMI filter is in front of the position where the current sensing circuit detects the common-mode current, and the cancellation current output by the feedback current compensation EMI filter is behind the position where the current sensing circuit detects the common-mode current; the power supply circuit is connected with the power electronic converter and the line impedance stabilization network, and is connected with two voltage amplification circuits and two power amplification circuits; the current sensing circuit is used for detecting a common-mode current signal and converting the common-mode current signal into a voltage signal, and is connected with the input terminals of the first voltage amplification circuit and the second voltage amplification circuit respectively; the two voltage amplification circuits are composed of in-phase amplifiers, the input impedance of which is large, so that the attenuation of the voltage signal can be reduced; the output terminal of the first voltage amplification circuit is connected with the input terminal of the first power amplification circuit Q1, and the output terminal of the second voltage amplification circuit is connected with the input terminal of the second power amplification circuit Q2; the power amplification circuits are used for transmitting the voltage signal output by the voltage amplification circuits to the output impedance, and improving the ability of the output current in the converter system to better cancel the common-mode current; the output terminal of the first power amplification circuit Q1 is connected with the first output impedance, and the output terminal of the second power amplification circuit Q2 is connected with the second output impedance; the output impedance converts the amplified voltage signal into a current signal, cancels the common-mode current in the converter system, thereby suppressing the EMI on the DC side, and simultaneously plays a role of isolation; the output terminals of the two output impedance circuits are connected with the DC negative bus.

[0040] In specific embodiments, a fifth capacitor C5 is further included, two ends of the fifth capacitor C5 are connected with two ends of the line impedance stabilization network respectively and are arranged between the current sensing circuit and the line impedance stabilization network;

[0041] The fifth capacitor C5 arranged in front of the position where the current sensing circuit detects the common-mode current is used to ensure that the cancellation current output by the first power amplification circuit in the feed-forward current compensation EMI filter can flow freely in the system.

[0042] In specific embodiments, as shown in Figure 2 The current sensing circuit includes a current transformer and a first resistor R1.

[0043] The primary side winding L1 of the current transformer is connected with the power electronic converter, and the secondary side winding L2 of the current transformer is connected with the two ends of the first resistor R1; one end of the first resistor R1 is connected with the ground.

[0044] In the current sensing circuit designed in the embodiment, the first resistor R1 is 10 ohms, and the turns ratio of the current transformer is 1:10; in the embodiment, the number of gates on the positive and negative buses of the primary winding L1 of the current transformer is equal; the primary winding L1 of the current transformer and the secondary winding L2 of the current transformer share one magnetic core and are tightly coupled.

[0045] The current sensing circuit can detect the common-mode current on the network side of the line impedance stabilizing network and output a voltage signal; in the current sensing circuit, only one current transformer is needed for the cascaded active EMI filter, and the obtained voltage signal is transmitted to the voltage amplification circuit of the feedforward current compensation EMI filter and the feedback current compensation EMI filter of the cascaded active EMI filter, so that the number of transformers of the cascaded active EMI filter is reduced, and the volume of the cascaded active EMI filter can be reduced.

[0046] In specific embodiments, as shown in Figure 2 , the first voltage amplification circuit and the second voltage amplification circuit are of the same structure and share one double-channel operational amplifier U1, the operational amplifier U1 includes a first-channel operational amplifier U 1.1 and a second-channel operational amplifier U 1.2 ; the first voltage amplification circuit includes a second resistor R2 and a third resistor R3, and the second voltage amplification circuit includes a fourth resistor R4 and a fifth resistor R5;

[0047] One end of the second resistor R2, one end of the third resistor R3, and the inverting input of the first-channel operational amplifier U 1.1 are connected; the other end of the second resistor R2 is grounded;

[0048] One end of the fourth resistor R4, one end of the fifth resistor R5, and the inverting input of the second-channel operational amplifier U 1.2 are connected; the other end of the fourth resistor R4 is grounded;

[0049] The two non-inverting inputs of the operational amplifier U1 are connected to the other end of the first resistor R1; the positive voltage input of the operational amplifier U1 is connected to +V CC of the power supply; and the negative voltage input of the operational amplifier U1 is connected to -V CC of the power supply.

[0050] In the voltage amplification circuit of the feedforward current compensation EMI filter and the voltage amplification circuit of the feedback current compensation EMI filter designed in the scheme, the second resistor R2 is 1K ohms, the third resistor R3 is 1K ohms, the fourth resistor R4 is 1K ohms, the fifth resistor R5 is 9K ohms, and the operational amplifier U1 is AD826.

[0051] In the voltage amplification circuit of the feedforward current compensation EMI filter and the voltage amplification circuit of the feedback current compensation EMI filter, a double-channel operational amplifier can be shared, so as to reduce the volume and cost of the cascade active EMI filter; the voltage amplification circuit is composed of a non-inverting amplifier, and has large input impedance, so as to reduce the attenuation of the voltage signal.

[0052] In specific embodiments, as shown in Figure 3 and Figure 4 , the first power amplification circuit Q1 and the second power amplification circuit Q2 have the same structure, the first power amplification circuit Q1 comprises a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a first triode T1, a second triode T2, a first diode D1 and a second diode D2; the second power amplification circuit Q2 comprises an eleventh resistor R 11 , a twelfth resistor R 12 , a thirteenth resistor R 13 , a fourteenth resistor R 14 , a third triode T3, a fourth triode T4, a third diode D3 and a fourth diode D4;

[0053] One end of the sixth resistor R6 is connected with the collector of the first triode T1 and the +V CC of the power supply respectively; the other end of the sixth resistor R6, the base of the first triode T1 and the anode of the first diode D1 are connected; the cathode of the first diode D1 is connected with the output end of the first-channel operational amplifier U 1.1 and the anode of the second diode D2 respectively; the cathode of the second diode D2, one end of the seventh resistor R7 and the base of the second triode T2 are connected; the other end of the seventh resistor R7, the collector of the second triode T2 and the -V CC of the power supply are connected; the emitter of the first triode T1 is connected with one end of the eighth resistor R8; the emitter of the second triode T2 is connected with one end of the ninth resistor R9; the other end of the eighth resistor R8, the other end of the ninth resistor R9 and the other end of the third resistor R3 are connected;

[0054] One end of the eleventh resistor R 11 is connected with the collector of the third triode T3 and the +V CC of the power supply respectively; the other end of the eleventh resistor R 11 , the base of the third triode T3 and the anode of the third diode D3 are connected; the cathode of the third diode D3 is connected with the output end of the second-channel operational amplifier U 1.2The output end of the 12th resistor R is connected to the positive electrode of the fourth diode D4; the negative electrode of the fourth diode D4 and the twelfth resistor R 12 One end of the twelfth resistor R is connected to the base of the fourth transistor T4; 12 The other end of the fourth transistor T4, the collector and the -V CC The emitter of the third transistor T3 and the thirteenth resistor R 13 The emitter of the fourth transistor T4 and the fourteenth resistor R 14 The thirteenth resistor R 13 The other end of the fourteenth resistor R 14 The other end of is connected to the other end of the fifth resistor R5;

[0055] The first transistor T1 and the third transistor T3 are of NPN structure; the second transistor T2 and the fourth transistor T4 are of PNP structure.

[0056] In the power amplifier circuit designed in this scheme, the sixth resistor R6, the seventh resistor R7, and the eleventh resistor R 11 , the twelfth resistor R 12 All are 1K ohm, the eighth resistor R8, the ninth resistor R9, the thirteenth resistor R 13 , the fourteenth resistor R 14 All are 1 ohm, the first transistor T1 and the third transistor T3 are FZT692B, the second transistor T2 and the fourth transistor T4 are FZT792A, and the first diode D1, the second diode D2, the third diode D3 and the fourth diode D4 are 1N4148.

[0057] The sixth resistor R6, the seventh resistor R7, and the eleventh resistor R 11 , the twelfth resistor R 12 is a bias resistor, the eighth resistor R8, the ninth resistor R9, the thirteenth resistor R 13 , the fourteenth resistor R 14 It is a resistor set to prevent temperature drift. The first diode D1, the second diode D2, the third diode D3 and the fourth diode D4 are set to eliminate the dead zone effect. The power amplifier circuit works alternately through two complementary transistors. The two output stages can provide current for the cascaded active EMI filter to ensure the output of the offset current. At the same time, the two output stages can reduce the output impedance, enhance the output current capacity of the EMI filter, and ensure the common-mode EMI suppression effect of the active filter.

[0058] In a specific embodiment, the first output impedance circuit and the second output impedance circuit have the same structure, and the first output impedance circuit includes a tenth resistor R10 and the first capacitor C1; the second output impedance circuit comprises a tenth resistor R 15 and a second capacitor C2;

[0059] The tenth resistor R 10 has one end connected with the other end of the eighth resistor R8 and the other end of the ninth resistor R9 respectively; the other end of the tenth resistor R 10 is connected with one end of the first capacitor C1; the other end of the first capacitor C1 is connected with a negative bus line;

[0060] The fifteenth resistor R 15 has one end connected with the other end of the thirteenth resistor R 13 and the other end of the fourteenth resistor R 14 respectively; the other end of the fifteenth resistor R 15 is connected with one end of the second capacitor C2; the other end of the second capacitor C2 is connected with a negative bus line.

[0061] In the output impedance circuit of the feedforward current-compensated EMI filter and the output impedance circuit of the feedback current-compensated EMI filter designed in the scheme, the tenth resistor R 10 is 2 ohms, the fifteenth resistor R 15 is 1 ohm, and the first capacitor C1 and the second capacitor C2 are both 1 microfarad.

[0062] In the output impedance circuit of the feedforward current-compensated EMI filter and the output impedance circuit of the feedback current-compensated EMI filter in the embodiment, the amplified voltage signal is converted into a current signal, which is offset from the common-mode current of the system, thereby suppressing the EMI on the DC side; the first capacitor C1 and the second capacitor C2 play an isolating role.

[0063] In specific embodiments, as shown in Figure 1 , the power electronic converter system further comprises the line impedance stabilization network.

[0064] The schematic diagram of the power electronic converter system is shown in Figure 1 , which comprises a DC power supply, a line impedance stabilization network (LISN) for testing the cascaded active EMI filter based on element reuse, a power electronic converter, and a parasitic capacitor C p .

[0065] Figure 2The circuit diagram after the cascaded active EMI filter based on element reuse designed for the power electronic converter is accessed to the application, the active EMI filter is composed of feedforward current compensation EMI filter and feedback current compensation EMI filter, the above two EMI filters share three parts: current sensing circuit, power supply circuit and operational amplifier, which reduces the volume and cost of the cascaded active EMI filter; the cascaded active EMI filter improves the suppression effect of low frequency EMI by cascading two EMI active filters, so as to further reduce the volume of the required passive filter.

[0066] Figure 5 The equivalent circuit diagram after the cascaded active EMI filter designed for the power electronic converter is accessed to the application. In the figure, V CM is the common mode voltage source of the whole system, I LISN is the common mode current flowing through the LISN, I CM is the common mode current flowing through Z CM , I s is the common mode current flowing through the primary winding of the mutual inductor, Z outFF is the output impedance of the feedforward current compensation EMI filter, Z outFB is the output impedance of the feedback current compensation EMI filter, Z injFF is the impedance of the injection branch of the feedforward current compensation EMI filter, Z injFB is the impedance of the injection branch of the feedback current compensation EMI filter, Z LISN is the equivalent common mode impedance of the parallel LISN, V outFF is the output voltage of the feedforward current compensation EMI filter, V outFB is the output voltage of the feedback current compensation EMI filter, I injFF is the output current of the feedforward current compensation EMI filter, I injFB is the output current of the feedback current compensation EMI filter. A VFF is the gain of the sensing current to the output voltage of the feedforward current compensation EMI filter, A VFB is the gain of the sensing current to the output voltage of the feedback current compensation EMI filter, which is ideally related to the turns ratio of the current transformer, the resistance R1 and the amplification coefficient of the first channel operational amplifier U 1.1 and the second channel operational amplifier U 1.2 .

[0067] In order to reduce the volume of the mutual inductor, the turns ratio of the primary side of the mutual inductor is 1, and the turns ratio of the secondary side is n, according to the equivalent circuit diagram, the formula (1) of the output current of the active EMI filter can be obtained,

[0068]

[0069] By the common-mode current I flowing through the primary winding of the transformer s In contrast, the following equation (2) is obtained,

[0070]

[0071] Based on the principle of active EMI filter with feed-forward structure, I injFF should be equal to I s , so that I LISN may be equal to 0, according to equation (2), A VFF / (Z outFF +Z injFF ) should be equal to 1; based on the principle of active EMI filter with feedback structure, I injFB should be much greater than I s , so that the common-mode noise on the DC side can be well suppressed, according to equation (2), when A VFF / (Z outFF +Z injFF ) is equal to 1, A VFB / (Z outFB +Z injFB ) >> 1.

[0072] According to the equivalent circuit diagram, the ratio of the common-mode noise on the DC side with and without the active EMI filter, i.e. the insertion loss IL, can be obtained, as shown in equation (3),

[0073]

[0074] It can be seen that when A VFF / (Z outFF +Z injFF ) is equal to 1, A VFB / (Z outFB +Z injFB ) >> 1, the smaller the insertion loss, the better the effect of the cascaded active EMI filter, so that the common-mode noise on the DC side can be well suppressed. According to equation (3), it can be seen that the active EMI filter with feed-forward structure and the active EMI filter with feedback structure work together, which can greatly reduce the insertion loss. Compared with a single active EMI filter, the cascaded active EMI filter can further suppress the common-mode noise.

[0075] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A cascaded active EMI filter based on element reuse, connected to a power electronic converter and a line impedance stabilization network, characterized in that, The application relates to a cascaded active EMI filter based on element reuse. The feedforward current-compensated EMI filter comprises a first voltage amplification circuit, a first power amplification circuit Q1 and a first output impedance circuit; the feedback current-compensated EMI filter comprises a second voltage amplification circuit, a second power amplification circuit Q2 and a second output impedance circuit. The feedback current-compensated EMI filter shares a current sensing circuit and a power supply circuit with the feedforward current-compensated EMI filter. The power supply circuit is connected with the feedforward current-compensated EMI filter and the feedback current-compensated EMI filter. The input end of the current sensing circuit is connected with the positive and negative bus bars of the power electronic converter, and the output end is connected with the input end of the first voltage amplification circuit and the second voltage amplification circuit respectively; the output end of the first voltage amplification circuit is connected with the input end of the first power amplification circuit Q1, and the output end of the first power amplification circuit Q1 is connected with the first output impedance; the output end of the first output impedance is connected with the negative DC bus bar; the output end of the second voltage amplification circuit is connected with the input end of the second power amplification circuit Q2, and the output end of the second power amplification circuit Q2 is connected with the second output impedance; the output end of the second output impedance is connected with the negative DC bus bar. The current sensing circuit is used for sensing the common-mode current of the line impedance stabilization network and outputting the same voltage signal to two voltage amplification circuits; the two voltage amplification circuits are used for amplifying the voltage signal output by the current sensing circuit and outputting the amplified voltage signal to two power amplification circuits respectively; the two power amplification circuits are used for outputting the amplified voltage signal to two output impedance circuits respectively; and the two output impedance circuits are used for converting the amplified voltage signal into a current signal to offset the common-mode current in the converter system. The current sensing circuit comprises a current transformer and a first resistor R1.

2. The cascaded active EMI filter based on component reuse of claim 1, wherein, The primary side winding L1 of the current transformer is connected with the power electronic converter, and the secondary side winding L2 of the current transformer is connected with the first resistor R1; one end of the first resistor R1 is connected with the ground. The first transistor T1 and the third transistor T3 are NPN structures; and the second transistor T2 and the fourth transistor T4 are PNP structures.

3. The cascaded active EMI filter based on component reuse of claim 2, wherein, The first voltage amplification circuit and the second voltage amplification circuit are of the same structure and share a double-channel operational amplifier U1, the operational amplifier U1 comprises a first-channel operational amplifier U 1.1 and a second-channel operational amplifier U 1.2 ; the first voltage amplification circuit comprises a second resistor R2 and a third resistor R3, and the second voltage amplification circuit comprises a fourth resistor R4 and a fifth resistor R5; one end of the second resistor R2, one end of the third resistor R3 and the inverting input of the first pass operational amplifier U 1.1 are connected; the other end of the second resistor R2 is grounded; one end of the fourth resistor R4, one end of the fifth resistor R5 and the inverting input of the second channel operational amplifier U 1.2 are connected; the other end of the fourth resistor R4 is grounded; The two non-inverting input terminals of the operational amplifier U1 are connected to the other end of the first resistor R1; the positive voltage input terminal of the operational amplifier U1 is connected to the +V CC of the power supply; and the negative voltage input terminal of the operational amplifier U1 is connected to the -V CC of the power supply.

4. The cascaded active EMI filter based on component reuse of claim 3, wherein, The first power amplifier circuit Q1 and the second power amplifier circuit Q2 are of the same structure, the first power amplifier circuit Q1 comprises a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a first triode T1, a second triode T2, a first diode D1 and a second diode D2; the second power amplifier circuit Q2 comprises an eleventh resistor R 11 , a twelfth resistor R 12 , a thirteenth resistor R 13 , a fourteenth resistor R 14 , a third triode T3, a fourth triode T4, a third diode D3 and a fourth diode D4; One end of the sixth resistor R6 is connected with the collector of the first triode T1 and the +V of the power supply respectively CC The other end of the sixth resistor R6, the base of the first triode T1 and the anode of the first diode D1 are connected 1.1 The cathode of the first diode D1, the output of the first channel operational amplifier U and the anode of the second diode D2 are connected respectively; the cathode of the second diode D2, one end of the seventh resistor R7 and the base of the second triode T2 are connected; the other end of the seventh resistor R7, the collector of the second triode T2 and the -V of the power supply are connected CC The emitter of the first triode T1 and one end of the eighth resistor R8 are connected; the emitter of the second triode T2 and one end of the ninth resistor R9 are connected; the other end of the eighth resistor R8, the other end of the ninth resistor R9 and the other end of the third resistor R3 are connected; one end of the eleventh resistor R 11 is connected with the collector of the third transistor T3 and the +V CC of the power supply respectively; the other end of the eleventh resistor R 11 , the base of the third transistor T3 and the anode of the third diode D3 are connected; the cathode of the third diode D3 is connected with the output of the second channel operational amplifier U 1.2 and the anode of the fourth diode D4 respectively; the cathode of the fourth diode D4, one end of the twelfth resistor R 12 and the base of the fourth transistor T4 are connected; the other end of the twelfth resistor R 12 , the collector of the fourth transistor T4 and the -V CC of the power supply are connected; the emitter of the third transistor T3 is connected with one end of the thirteenth resistor R 13 ; the emitter of the fourth transistor T4 is connected with one end of the fourteenth resistor R 14 ; the other end of the thirteenth resistor R 13 , the other end of the fourteenth resistor R 14 and the other end of the fifth resistor R5 are connected.

5. The cascaded active EMI filter based on component reuse of claim 4, wherein, The first output impedance circuit and the second output impedance circuit are of the same structure, the first output impedance circuit comprises a tenth resistor R 10 and a first capacitor C1; the second output impedance circuit comprises a fifteenth resistor R 15 and a second capacitor C2; One end of the tenth resistor R 10 is connected with the other end of the eighth resistor R8 and the other end of the ninth resistor R9 respectively; the other end of the tenth resistor R 10 is connected with one end of the first capacitor C1; the other end of the first capacitor C1 is connected with the negative bus. One end of the fifteenth resistor R 15 is connected with the other end of the thirteenth resistor R 13 and the other end of the fourteenth resistor R 14 respectively; the other end of the fifteenth resistor R 15 is connected with one end of the second capacitor C2; the other end of the second capacitor C2 is connected with the negative bus.

6. The cascaded active EMI filter based on component reuse of claim 4, wherein, 7. A power electronic converter system comprising the cascaded active EMI filter based on element reuse according to claim 1. ​

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