Improved electromagnetic interference filter implementation method

Abstract

The invention relates to an improved EMI (Electro-Magnetic Interference) method for the output of a three-phase four-wire inverter, which is realized by arranging a common-mode rejection filtering module from the output side to the load side of the inverter, and the common-mode rejection filtering module comprises a capacitor bank and two common-mode coupling inductors for separating a differential-mode signal from a common-mode signal, and a resistance circuit module is arranged behind the second common-mode coupling inductor to absorb electromagnetic noise generated by the common-mode coupling inductor. According to the technical scheme, common-mode and differential-mode conducted electromagnetic interference can be restrained, the influence of power grid conducted electromagnetic interference on work of the power converter is reduced, and pollution of electromagnetic interference generated by the power converter to a power grid is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of electromagnetic compatibility, and in particular to an improved method for realizing an electromagnetic interference filter. Background Art

[0002] In order to solve the electromagnetic compatibility problem, an electromagnetic interference filter (EMI) needs to be set at the input and output interfaces of the inverter to control EMI conducted interference, allowing only ideal low-pass currents of DC and power frequency to pass through. The electromagnetic interference filter can achieve bidirectional filtering, which can prevent the inverter from emitting noise interference to the outside and suppress the introduction of external interference into the system. The EMI filter includes X capacitors, Y capacitors, and common-mode inductors. The ideal common-mode choke coil only eliminates noise without affecting the signal waveform, but unfortunately, the actual components cannot operate in this way. Therefore, it is necessary to improve the existing EMI filter to further reduce the impact of the common-mode choke coil on the signal waveform while improving the suppression effect of common-mode noise. Summary of the invention

[0003] In order to solve the above technical problems, the present invention proposes an improved electromagnetic interference filter implementation method, wherein the method sequentially passes the inverter output signal through a primary filtering step, a leakage current protection step, and a surge protection step and then outputs it to the load side, wherein the primary filtering step is implemented by setting a common-mode suppression filter module from the inverter output side to the load side, wherein the common-mode suppression filter module includes a filter capacitor group and two common-mode coupling inductors for separating differential-mode signals and common-mode signals, and a resistance circuit module is set after the second common-mode coupling inductor to absorb the electromagnetic noise generated by the common-mode coupling inductor.

[0004] Furthermore, the two groups of coils of the first common-mode coupling inductor are respectively the first phase line and the second phase line of the forward winding and the third phase line and the neutral line of the reverse winding, and the two groups of coils of the second common-mode coupling inductor are respectively the second phase line and the third phase line of the forward winding and the first phase line and the neutral line of the reverse winding; the inductive reactance of the common-mode coupling inductor is 3-5mH.

[0005] Furthermore, the resistance circuit module is provided with three parallel resistance strings, each resistance string is composed of a plurality of resistors with a resistance value of 250-280 kΩ connected in series.

[0006] Furthermore, the filter capacitor group includes a first filter capacitor group and a second filter capacitor group respectively arranged after the first common-mode coupling inductor and the second common-mode inductor, each of the filter capacitor groups includes three X capacitors connected in parallel, and a grounded Y capacitor is arranged on the middle line.

[0007] Furthermore, the leakage current protection step is performed by arranging a leakage protection module after the resistance circuit module, the leakage protection module includes a GFCI leakage current detector, a third filter capacitor group is arranged in front of the GFCI leakage current detector, and the third filter capacitor group includes four grounded Y capacitors, wherein one end of each Y capacitor is connected to a phase line or a neutral line.

[0008] Furthermore, the surge protection step is performed by setting parallel varistors after the leakage protection module, wherein the first varistor is connected to the first phase line and then connected in series with the first fuse; the second varistor is connected to the second phase line and then connected in series with the second fuse; the third varistor is connected to the third phase line and then connected in series with the third fuse; the fourth varistor is connected to the neutral line and then connected in series with the fourth fuse; and the four fuses are grounded through the same discharge tube.

[0009] Furthermore, the leakage protection module also includes a current difference amplifier, which triggers the GFCI leakage current detector protection switch when it detects that the current difference is greater than 5 mA.

[0010] Furthermore, each resistor string is composed of three resistors connected in series with a resistance value of 270 kΩ.

[0011] Further, the X capacitor in the first filter capacitor group is configured to be 20-25 μF, and the Y capacitor in the first filter capacitor group is configured to be 1 nF; the X capacitor in the second filter capacitor group is configured to be 0.4-0.5 μF, and the Y capacitor in the second filter capacitor group is configured to be 4-5 nF.

[0012] Furthermore, the rated output power of the inverter output side ranges from 6 kW to 100 kW.

[0013] The beneficial effect of the present invention is that the influence of the common mode choke coil on the output signal waveform of the inverter can be reduced, thereby ensuring the stability of the power supply output. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 .Schematic diagram of some solutions;

[0015] Figure 2 .Circuit schematics of some solutions;

[0016] Figure 3 . Schematic diagram of partial circuit structure of some schemes;

[0017] Figure 4 .Schematic diagram of partial circuit structure of some schemes. DETAILED DESCRIPTION

[0018] In the relevant technical field, "common-mode coupling inductor" is an inductor device used to suppress common-mode interference. "Common-mode interference" refers to an interference signal that affects two signals at the same time. The function of the common-mode coupling inductor is to reduce the impact of common-mode interference by winding two signal coils on the same iron core in the signal transmission line so that there is a strong coupling between them. Common-mode coupling inductors are generally composed of two concentric coils, one of which is used to transmit differential-mode signals (signals with forward and reverse phases) and the other is used to transmit common-mode signals (the addition of two signals). By separating the differential-mode signal and the common-mode signal, common-mode interference can be effectively suppressed. Common-mode coupling inductors are widely used in some communications, audio and video equipment, especially in differential signal transmission and suppressing ground return noise. It can improve the system's anti-interference ability and provide clearer and more stable signal transmission.

[0019] GFCI stands for Ground Fault Current Interrupter.

[0020] The situations of "leakage" and "no leakage" described in the present invention refer to:

[0021] (1) No leakage: When the three phases of the external circuit are balanced, there is no current in the neutral line (neutral line); when the three phases are unbalanced, there is current in the neutral line.

[0022] (2) Leakage: Even when the three phases of the external circuit are balanced, there is still current in the neutral line (center line).

[0023] Various aspects of the present invention will now be explained with reference to the accompanying drawings. As long as the shapes, relative positions and other aspects of the components described in these aspects are not clearly defined, the scope of the present disclosure is not limited to the components shown, which are only used for illustrative purposes. In addition, although many details are set forth, it should be understood that some aspects of the present disclosure can be implemented without these details. In other cases, well-known circuits, structures and technologies are not shown in detail to avoid obscuring the understanding of the description.

[0024] Some solutions include Figure 1 The steps shown in the figure receive a signal from the inverter output end, and the received signal is processed in sequence through a primary filtering step, a leakage current protection step, and a surge protection step before being output to the load side. The primary filtering step is performed by setting a Figure 2 The common mode suppression filter module shown is implemented as follows. The common mode suppression filter module includes a filter capacitor group and two common mode coupling inductors for separating differential mode signals from common mode signals, and a resistor circuit module is arranged after the second common mode coupling inductor to absorb the electromagnetic noise generated by the common mode coupling inductor.

[0025] like Figure 1-2 The scheme shown in the figure has a circuit diagram as shown in Figure 3 , the two groups of coils of the first common-mode coupling inductor are respectively the first phase line and the second phase line of the forward winding and the third phase line and the neutral line of the reverse winding, and the two groups of coils of the second common-mode coupling inductor are respectively the second phase line and the third phase line of the forward winding and the first phase line and the neutral line of the reverse winding; the inductive reactance of each common-mode coupling inductor is 3-5mH. Preferably, the inductive reactance of the common-mode coupling inductor is 3mH. A first filter capacitor group and a second filter capacitor group are respectively arranged after the first common-mode coupling inductor and the second common-mode inductor, each of the filter capacitor groups includes three parallel X capacitors, and a grounded Y capacitor is arranged on the neutral line.

[0026] exist Figure 1-2 Based on the scheme shown, preferably, the following is set Figure 4 The resistor circuit module is composed of three parallel resistor strings, each resistor string is provided with a plurality of series resistors, and the resistance value of each resistor is set to 250-280 kΩ. Preferably, each resistor string is provided with three series resistors, and the resistance value of each resistor is set to 270 kΩ. The secondary noise generated by the common mode inductance will be absorbed by these impedance elements.

[0027] like Figure 1 The leakage current protection step is achieved by arranging a leakage protection module after the resistance circuit module. The leakage protection module includes a GFCI leakage current detector, and a third filter capacitor group is arranged in front of the GFCI leakage current detector. The third filter capacitor group includes four grounded Y capacitors, and one end of each Y capacitor is connected to the phase line or the neutral line.

[0028] like Figure 1-2 The scheme, in which the surge protection step is realized by arranging a surge protection module composed of parallel varistors after the leakage protection module, wherein the first varistor is connected to the first phase line and then connected in series with the first fuse; the second varistor is connected to the second phase line and then connected in series with the second fuse; the third varistor is connected to the third phase line and then connected in series with the third fuse; the fourth varistor is connected to the neutral line and then connected in series with the fourth fuse; the four fuses are grounded through the same discharge tube.

[0029] In some solutions, based on the above solutions, the leakage protection module preferably also includes a current difference amplifier, which triggers the GFCI leakage current detector protection switch when it detects that the current difference is greater than 5 mA.

[0030] In some schemes, based on the above scheme, the X capacitor in the first filter capacitor group is preferably configured to be 20-25 μF, and the Y capacitor in the first filter capacitor group is configured to be 1 nF; the X capacitor in the second filter capacitor group is configured to be 0.4-0.5 μF, and the Y capacitor in the second filter capacitor group is configured to be 4-5 nF.

[0031] The rated output power range of the inverter output side of the above solution is 6-100kW.

[0032] Although this specification contains many specific implementation details, these should not be interpreted as limitations on the scope of any invention or the scope of what can be claimed, but rather as an illustration of features that can concretize a particular embodiment of a particular invention. The specific features described in this specification in the context of independent embodiments can also be implemented in combination with a single embodiment. Conversely, the various features described in the context of a single embodiment can also be implemented independently in multiple embodiments, or in any suitable sub-combination. In addition, although the features can be described above as a combination effect and even initially required, one or more features from the required combination can be removed from the combination in some cases, and the required combination can be turned to a sub-combination or a variation of the sub-combination.

[0033] Specific implementations of the subject matter have been described. Other implementations are within the scope of the following claims. For example, the activities recited in the claims can be performed in a different order and still achieve the desired results. As an example, the processes described in the accompanying drawings do not necessarily require the specific order or sequential order shown in order to achieve the desired results. In certain implementations, multitasking and parallel processing may be advantageous.

Claims

1. An improved electromagnetic interference filter implementation method, characterized in that: The method outputs the inverter output signal to the load side after passing through a primary filtering step, a leakage current protection step, and a surge protection step in sequence. The primary filtering step is achieved by arranging a common-mode suppression filter module from the inverter output side to the load side. The common-mode suppression filter module includes a filter capacitor group and two common-mode coupling inductors for separating differential-mode signals from common-mode signals, and a resistance circuit module is arranged after the second common-mode coupling inductor to absorb electromagnetic noise generated by the common-mode coupling inductor.

2. The improved electromagnetic interference filter implementation method as claimed in claim 1, characterized in that: The two groups of coils of the first common-mode coupling inductor are respectively the first phase line and the second phase line of the forward winding and the third phase line and the neutral line of the reverse winding; the two groups of coils of the second common-mode coupling inductor are respectively the second phase line and the third phase line of the forward winding and the first phase line and the neutral line of the reverse winding; the inductive reactance of the common-mode coupling inductor is 3-5mH.

3. The improved electromagnetic interference filter implementation method as claimed in claim 2, characterized in that: The resistor circuit module is provided with three parallel resistor strings, each of which is composed of a plurality of resistors with a resistance value of 250-280 kΩ connected in series.

4. The improved electromagnetic interference filter implementation method as claimed in claim 3, characterized in that: The filter capacitor group includes a first filter capacitor group and a second filter capacitor group respectively arranged after the first common-mode coupling inductor and the second common-mode inductor, each of the filter capacitor groups includes three X capacitors connected in parallel, and a grounded Y capacitor is arranged on the middle line.

5. The improved electromagnetic interference filter implementation method as claimed in claim 1, characterized in that: The leakage current protection step is achieved by arranging a leakage protection module after the resistance circuit module, wherein the leakage protection module includes a GFCI leakage current detector, and a third filter capacitor group is arranged in front of the GFCI leakage current detector, wherein the third filter capacitor group includes four grounded Y capacitors, wherein one end of each Y capacitor is connected to a phase line or a neutral line.

6. The improved electromagnetic interference filter implementation method as claimed in claim 1, characterized in that: The surge protection step is performed by setting parallel varistors after the leakage protection module, wherein the first varistor is connected to the first phase line and then connected in series with the first fuse; the second varistor is connected to the second phase line and then connected in series with the second fuse; the third varistor is connected to the third phase line and then connected in series with the third fuse; the fourth varistor is connected to the neutral line and then connected in series with the fourth fuse; and the four fuses are grounded through the same discharge tube.

7. The improved electromagnetic interference filter implementation method as claimed in claim 1, characterized in that: The leakage protection module also includes a current difference amplifier, which triggers the GFCI leakage current detector protection switch when it detects that the current difference is greater than 5 mA.

8. The improved electromagnetic interference filter implementation method as claimed in claim 3, characterized in that: Each resistor string consists of three resistors connected in series with a resistance of 270kΩ.

9. The improved electromagnetic interference filter implementation method as claimed in claim 4, characterized in that: The X capacitors in the first filter capacitor group are configured to be 20-25 μF, and the Y capacitors in the first filter capacitor group are configured to be 1 nF; the X capacitors in the second filter capacitor group are configured to be 0.4-0.5 μF, and the Y capacitors in the second filter capacitor group are configured to be 4-5 nF.

10. The improved electromagnetic interference filter implementation method as claimed in claim 1, characterized in that: The rated output power of the inverter output side ranges from 6 kW to 100 kW.

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