CN211791244U - Alternating current filter with wide frequency range - Google Patents
Alternating current filter with wide frequency range Download PDFInfo
- Publication number
- CN211791244U CN211791244U CN202020139562.5U CN202020139562U CN211791244U CN 211791244 U CN211791244 U CN 211791244U CN 202020139562 U CN202020139562 U CN 202020139562U CN 211791244 U CN211791244 U CN 211791244U
- Authority
- CN
- China
- Prior art keywords
- filter circuit
- common mode
- inductor
- phase
- filter
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Landscapes
- Filters And Equalizers (AREA)
Abstract
The utility model provides a wide frequency range's alternating current filter, include: the filter comprises a first-stage common mode filter circuit, a first-stage differential mode filter circuit and a differential common mode filter circuit, wherein a second-stage differential mode filter circuit is connected in parallel between the common mode filter circuit and the first-stage common mode filter circuit; the single-phase filter circuit of the second-stage differential mode filter circuit is a second-order high-pass filter circuit. The utility model adds a second-order high-pass filter on the basis of the original three-phase AC filter circuit structure, so that the three-phase AC filter can effectively limit the low-frequency noise at the inlet side above 10kHz except meeting the requirement of 150 kHz-30 MHz frequency band in the standard; and the common mode filter circuit structure of the three-phase alternating current filter is adjusted, the LC filter structure is changed into the LCL filter structure, the primary common mode inductor is added, and the suppression of the common mode interference noise of the system is increased.
Description
Technical Field
The utility model relates to an exchange the filtering field, especially relate to a wide frequency range's alternating current filter.
Background
With the rapid development of power electronic technology and computer control technology, an alternating current speed regulating system consisting of a servo driver and a servo motor is widely applied to a numerical control machine tool. However, the numerically controlled machine tool has electromagnetic interference (including interference of power frequency electromagnetic field and harmonic wave) in different degrees during operation, and the electromagnetic interference not only affects the precision and stability of the equipment of the numerically controlled machine tool, but also brings harm to the normal operation of surrounding equipment.
Electromagnetic interference in machine tool operation is mainly caused by high-frequency noise generated by internal power devices such as Insulated Gate Bipolar Transistors (IGBTs) in high-speed switching. Generally, a three-phase electromagnetic interference (EMI) filter is installed at an incoming line of a numerical control machine tool system, and the structure of the filter is shown in fig. 1, in the prior art, common-mode and differential-mode interference voltages are reduced, and high-frequency (frequency range of 150KHz to 30MHz) conductive interference generated by a speed regulation system is suppressed, so that the anti-interference capability of the whole machine tool system is improved.
However, in some numerically controlled machine tool systems, especially in high-power machine tool systems, the electromagnetic interference problem still exists in a lower frequency band (10KHz to 100KHz), which mainly shows that differential mode interference voltage affects malfunction or alarm of peripheral equipment, and common mode interference voltage causes excessive ground voltage difference to damage control equipment and the like, so that the overall electromagnetic interference (EMI) environment of the machine tool needs to be improved greatly.
SUMMERY OF THE UTILITY MODEL
The utility model provides a wide frequency range's alternating current filter to overcome above-mentioned technical problem.
The utility model provides a wide frequency range's alternating current filter, include: one-level common mode filter circuit, one-level differential mode filter circuit and poor common mode filter circuit, one-level common mode filter circuit includes: inductor LAInductor LBAnd an inductance LC(ii) a The inductance LAIs connected in series with the phase line A, and the inductor LBIs connected in series with the B phase line, the inductor LCIs connected in series with the C phase line; the method is characterized in that: a second-stage differential mode filter circuit is connected in parallel between the common mode filter circuit and the first-stage common mode filter circuit;
and the single-phase filter circuit of the second-stage differential mode filter circuit is a second-order high-pass filter circuit.
Further, the second-order high-pass filter circuit includes: the inductor comprises a capacitor C, a resistor R and an inductor L, wherein one end n of the resistor R connected with the inductor L in parallel is grounded, the other end m of the resistor R is connected with one end of the capacitor C, and the other end of the capacitor C is connected with any phase line.
Furthermore, the two-stage differential mode filter circuit comprises a first second-order high-pass filter circuit, a second-order high-pass filter circuit and a third second-order high-pass filter circuit;
the resistor R of the first second-order high-pass filter circuit1And an inductance L1After parallel connection, one end is m1And the other end is n1，m1And a capacitor C1Is connected to one terminal of a capacitor C1The other end of the first switch is connected with the phase line A;
resistor R of second-order high-pass filter circuit2And an inductance L2After parallel connection, one end is m2And the other end is n2，m2And a capacitor C2ToEnd-to-end, capacitor C2The other end of the first switch is connected with a phase line B;
resistor R of third second-order high-pass filter circuit3And an inductance L3After parallel connection, one end is m3And the other end is n3，m3Connected to one terminal of a capacitor C33The other end of the C-phase line is connected with the phase line C; n is1、n2、 n3Are connected.
Further, still include: the second-stage common mode filter circuit is arranged on the incoming line side and is used for filtering three-phase current of the incoming line;
the second-stage common mode filter circuit includes: inductor LXInductor LYAnd an inductance LZ(ii) a The inductance LXIs connected in series with the phase line A, and the inductor LYIs connected in series with the B phase line, the inductor LZIs connected in series with the C phase line.
Further, the second-stage common mode filter circuit further includes: and a damping resistor Rg connected to the second-stage common mode filter circuit.
The utility model adds a second-order high-pass filter on the basis of the original three-phase AC filter circuit structure, so that the three-phase AC filter can effectively limit the low-frequency noise at the inlet side above 10kHz except meeting the requirement of 150 kHz-30 MHz frequency band in the standard; and the common mode filter circuit structure of the three-phase alternating current filter is adjusted, the LC filter structure is changed into the LCL filter structure, the primary common mode inductor is added, and the suppression of the common mode interference noise of the system is increased.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive labor.
FIG. 1 is a schematic diagram of a prior art three-phase AC filter circuit configuration;
FIG. 2 is a schematic diagram of the wide frequency range AC filter circuit of the present invention;
FIG. 3 is a schematic diagram of a second order high pass filter circuit for a wide frequency range AC filter of the present invention;
FIG. 4 is a comparison graph of amplitude-frequency characteristics of a wide-frequency-range AC filter according to the present invention and a three-phase AC filter according to the prior art;
FIG. 5 is an attenuation curve for a low pass filter of different orders;
FIG. 6 is a schematic diagram of the LCL single-phase filter circuit structure;
FIG. 7 is a block diagram of a model structure of an LCL single-phase filter circuit;
fig. 8 is a comparison of amplitude-frequency characteristics of the common mode circuit LC and the LCL of the three-phase ac filter.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
The utility model provides a wide frequency range's alternating current filter, include: first-order common mode filter circuit 1, first-order differential mode filter circuit 5 and poor common mode filter circuit 6, first-order common mode filter circuit 1 includes: inductor LAInductor LBAnd an inductance LC(ii) a The inductance LAIs connected in series with the phase line A, and the inductor LBIs connected in series with the B phase line, the inductor LCIs connected in series with the C phase line; the method is characterized in that: a second-stage differential mode filter circuit 2 is connected in parallel between the common mode filter circuit 6 and the first-stage common mode filter circuit 1;
and the single-phase filter circuit of the second-stage differential mode filter circuit 2 is a second-order high-pass filter circuit.
Further, the second-order high-pass filter circuit includes: as shown in fig. 3, a capacitor C, a resistor R and an inductor L, wherein one end n of the resistor R connected in parallel with the inductor L is grounded, the other end m is connected with one end of the capacitor C, and the other end of the capacitor C is connected to any phase line.
Further, as shown in fig. 2, the two-stage differential mode filter circuit 2 includes a first second-order high-pass filter circuit 7, a second-order high-pass filter circuit 8, and a third second-order high-pass filter circuit 9;
the resistor R of the first second-order high-pass filter circuit 71And an inductance L1After parallel connection, one end is m1And the other end is n1，m1And a capacitor C1Is connected to one terminal of a capacitor C1The other end of the first switch is connected with the phase line A;
resistor R of second-order high-pass filter circuit 82And an inductance L2After parallel connection, one end is m2And the other end is n2，m2And a capacitor C2Is connected to one terminal of a capacitor C2The other end of the first switch is connected with a phase line B;
resistor R of third second-order high-pass filter circuit 93And an inductance L3After parallel connection, one end is m3And the other end is n3，m3Connected to one terminal of a capacitor C33The other end of the C-phase line is connected with the phase line C; n is1、n2、 n3Are connected.
Further, still include: the second-stage common mode filter circuit 3 is arranged on the incoming line side and is used for filtering three-phase current of the incoming line;
the two-stage common mode filter circuit 3 includes: inductor LXInductor LYAnd an inductance LZ(ii) a The inductance LXIs connected in series with the phase line A, and the inductor LYIs connected in series with the B phase line, the inductor LZIs connected in series with the C phase line.
Further, the two-stage common mode filter circuit 3 further includes: and the damping resistor Rg of the second-stage common mode filter circuit 3 is accessed.
Improvement measures of the common mode circuit: on the basis of the prior circuit structure shown in FIG. 1, a two-stage common mode circuit 3, namely three inductors L, is addedX、LYAnd LZThe original LC second-order low-pass filter circuit is upgraded to an LCL third-order low-pass filter circuit, so that the filter frequency range can be improved, and the rejection capability of common-mode interference harmonic waves is also improved. The high frequency common mode voltage generated by a PWM (pulse width modulation) inverter causes a series of negative effects during the speed regulation: a large amount of higher harmonic current flows into the power grid through the common ground end, so that harmonic pollution to the power grid is caused; the increasing switching frequency leads to the overlarge voltage rising rate of output, and voltage reflection is easy to occur at the motor end to cause overvoltage; a large amount of electromagnetic radiation is generated in the operation of the medium and high power inverter, electromagnetic interference is generated on electronic and electrical product components, and the performance index of the product is influenced. Compared with the traditional L-type or LC-type filter circuit, the LCL filter circuit is suitable for being applied to a three-phase alternating current filter circuit on a high-power occasion with lower cost and better high-order filtering attenuation capability.
Firstly, analyzing a differential mode interference circuit: comparing the filter circuit diagram of fig. 2 with the filter circuit diagram of fig. 1 in the prior art, it can be seen that the differential mode filter circuit 2 is added, and is composed of three second-order high-pass filter circuits 7, and the structure of the differential mode filter circuit is shown in fig. 2. Since the inductor L is connected in parallel with the resistor R, the parallel impedance of the inductor L does not exceed the resistance value, so that the inductor L is different from a single-tuned filter which only presents a low impedance for a certain frequency and has a lower impedance frequency range. The larger the resistance, the sharper the tuning, and its quality factor is an indicator of the sharpness of the tuning. When the frequency is below the cut-off frequency fcWhen the filter is used, the impedance of the filter is obviously increased due to the increase of the capacitive reactance, and low-order harmonic current is difficult to pass; when the frequency is higher than fcIn this case, the capacitance is not large, and the total impedance is not changed much, thereby forming a passband.
The second-order high-pass filter circuit 7 can select the circuit constant according to two parameters:
(1) cut-off frequency
(2) Quality factor Q
In the formula, XLnThe impedance value of the inductor L at the harmonic frequency; and n is the harmonic order. From the above formula, Q is related to n. As with the single tuned filter, when n satisfies the following equation:
nXC＝nXL(3)
the Q value of the time is the quality factor, X, of the high-pass filter circuitCIs the impedance value, X, of a capacitor C in a second-order high-pass filterLIs the impedance value of the inductor L in the second order high pass filter. So that the formula (2) and the formula
(3) Deducing:
the parameter m is introduced and defined as follows:
the parameter m is also called a shape parameter, and when a plurality of higher harmonics are filtered, the value range is generally 0.1-2, so the Q value is about 0.7-3.2. In general, the operating characteristics of the second-order high-pass filter are insensitive to component parameter variations and frequency, and thus the effects of frequency offset may not be considered. Moreover, the total impedance of the second-order high-pass filter is approximately equal in a relatively wide frequency band, so that the problem of selecting the best Q value does not exist. Consideration should be given to the second-order high-pass filtering above the cut-off frequency f without affecting the filtering effect on higher harmonicscExhibit a low impedance characteristic.
As shown in fig. 3, with respect to the determination of R, L, C three parameters in the second-order high-pass filter, the impedance, current value, voltage value, and capacitance value of each element in the case of fundamental wave and higher harmonic wave can be calculated from various operating conditions of the three-phase ac filter.
The impedance value of the second-order high-pass filter is as follows:
when the Q value is 0.85, and in engineering applications, considering material cost and structural layout, when R is 1.1 Ω, L is 50uH, and C is 30uF, a second-order high-pass filter is added, and then the amplitude-frequency characteristic of the differential-mode circuit of the three-phase ac filter is as shown in fig. 4. The cut-off frequency of the second-order high-pass filter circuit 7 is greatly reduced, so that the range of suppressing harmonic interference is widened, and the range of suppressing harmonic interference is increased from 48.2394K-30MHz to 6.8180K-30MHz as can be seen from a curve a and a curve b.
For the differential mode interference, to achieve the same filtering effect in a wide frequency range, the capacity of the capacitor C in the second-order high-pass filter circuit may be increased or the number of stages of the high-pass filter circuit may be increased, but the cost and the space requirement may be increased undoubtedly.
Secondly, analyzing a common-mode interference circuit: comparing fig. 2 with fig. 1, the structural form of the common mode circuit is changed from LC to LCL structure filter circuit, i.e. a first common mode inductance coil, i.e. L, is addedX、LY、Lz。
The attenuation of common mode filtering is mainly due to the common mode inductance (L) at low frequenciesA、LB、LC、LX、LY、LZ) Acting and at high frequencies largely by common mode capacitance (C)X、CY、CZ) And (4) acting. The common mode capacitor is selected according to actual conditions, and is connected between a power supply line and a ground line, and is subjected to a relatively high voltage, so that high withstand voltage and low leakage current characteristics are required. After the first-stage common mode inductor is added, the filter circuit is changed from the second-order to the third-order, so that the attenuation degree of harmonic current can be greatly changed. We take as an example the attenuation curves of filters of different orders, as shown in fig. 5, where the abscissa is the response frequency, expressed logarithmically, the ordinate represents the gain (in dB), the rightmost one is the attenuation curve of a first-order filter, the frequency increases by a factor of ten from 100k to 1M, from the ordinate it can be seen that the gain decreases by 20dB, commonly referred to as a 10 octave attenuation of 20dB,the second curve on the right is a second order filter, and a 10 octave attenuation of 40dB is readily seen. It follows that the tenfold frequency attenuation increases by 20dB for each order of filter increase.
Before designing the LCL filter, a transfer function expression of the LCL filter in a frequency domain is established, and the influence of the transfer function expression on the stability of the system is analyzed by researching the expression. The single-phase LCL filter structure is shown in FIG. 6, and the equivalent structure of the single-phase LCL filter structure in the frequency domain is shown in FIG. 7. Assuming that the harmonic content of the ideal grid voltage is 0, e(s) is 0, and thus a single-phase model frequency domain admittance expression is established as follows:
wherein:
U＝LALXCX(8)
V＝LXCX(R4+R6)+LACX(R5+R6) (9)
W＝LA+LX+CX(R4R5+R4R6+R5R6) (10) D＝R4+R5(11)
due to R4，R5，R6The numerical value is small, and R is ignored in theoretical analysis4，R5，R6The expression can be derived as follows:
the two-port network of the transfer function is unstable according to the Laus stability criterion, the impedance of the LCL single-phase filter circuit is zero at a certain frequency, and the resonant frequency is
However, there is an equivalent impedance in the actual inductor and capacitorThe value is very small, and the stability of the LCL single-phase filter circuit is very little influenced. In order to solve the stability problem of the LCL single-phase filter circuit and eliminate the peak generated by the interference signal at the cut-off frequency of the filter, the common mode inductor (L) at the line inlet side of the filter circuit is adopted in the inventionX、LY、 LZ) Is added with a damping resistor RgAnd the original secondary side transformation ratio is 1:1, and the formula (12) is derived as follows:
in this example, take LA＝1000uH,LX＝500uH,CX20uF, Rg 10 omega, as shown in figure 8
As shown, a curve a1 is an amplitude-frequency characteristic curve of the LC filter circuit in fig. 1, a curve c is an amplitude-frequency characteristic curve of the LCL filter circuit in fig. 2 without adding the damping resistor Rg, and a curve b1 is an amplitude-frequency characteristic curve of the LCL filter circuit in fig. 2 with adding the damping resistor Rg. As can be seen from fig. 8, when the damping resistor Rg is not added, one peak in the curve b is a resonance point, and after the damping resistor Rg is added, the peak is weakened, and the high-frequency characteristic curve of the curve b is unchanged, but the low-frequency characteristic curve is gradually flattened. It can be seen that a first common mode inductor (L) is addedX、LY、LZ) And then, the suppression capability of the high-frequency harmonic interference of the whole common mode filter circuit is enhanced, and a good filtering effect is achieved in a low-frequency band.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention.
Claims (5)
1. A wide frequency range ac filter comprising: first order common mode filteringCircuit (1), one-level differential mode filter circuit (5) and poor common mode filter circuit (6), one-level common mode filter circuit (1) includes: inductor LAInductor LBAnd an inductance LC(ii) a The inductance LAIs connected in series with the phase line A, and the inductor LBIs connected in series with the B phase line, the inductor LCIs connected in series with the C phase line; the method is characterized in that: a second-stage differential mode filter circuit (2) is connected in parallel between the common mode filter circuit (6) and the first-stage common mode filter circuit (1);
and the single-phase filter circuit of the second-stage differential mode filter circuit (2) is a second-order high-pass filter circuit.
2. The filter of claim 1, wherein the second order high pass filter circuit comprises: the inductor comprises a capacitor C, a resistor R and an inductor L, wherein one end n of the resistor R connected with the inductor L in parallel is grounded, the other end m of the resistor R is connected with one end of the capacitor C, and the other end of the capacitor C is connected with any phase line.
3. A filter according to claim 2, wherein the two-stage differential-mode filter circuit (2) comprises a first second-order high-pass filter circuit (7), a second-order high-pass filter circuit (8) and a third second-order high-pass filter circuit (9);
the resistor R of the first second-order high-pass filter circuit (7)1And an inductance L1After parallel connection, one end is m1And the other end is n1，m1And a capacitor C1Is connected to one terminal of a capacitor C1The other end of the first switch is connected with the phase line A;
a resistor R of the second-order high-pass filter circuit (8)2And an inductance L2After parallel connection, one end is m2And the other end is n2，m2And a capacitor C2Is connected to one terminal of a capacitor C2The other end of the first switch is connected with a phase line B;
a resistor R of the third second-order high-pass filter circuit (9)3And an inductance L3After parallel connection, one end is m3And the other end is n3，m3Connected to one terminal of a capacitor C33The other end of the C-phase line is connected with the phase line C; n is1、n2、n3Are connected.
4. The filter of claim 1, further comprising: the second-stage common mode filter circuit (3) is arranged on the incoming line side and is used for filtering three-phase current of the incoming line;
the two-stage common mode filter circuit (3) comprises: inductor LXInductor LYAnd an inductance LZ(ii) a The inductance LXIs connected in series with the phase line A, and the inductor LYIs connected in series with the B phase line, the inductor LZIs connected in series with the C phase line.
5. A filter according to claim 4, characterized in that the second-stage common-mode filter circuit (3) further comprises: and a damping resistor Rg connected to the second-stage common mode filter circuit (3).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020139562.5U CN211791244U (en) | 2020-01-21 | 2020-01-21 | Alternating current filter with wide frequency range |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020139562.5U CN211791244U (en) | 2020-01-21 | 2020-01-21 | Alternating current filter with wide frequency range |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN211791244U true CN211791244U (en) | 2020-10-27 |
Family
ID=72903886
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202020139562.5U Active CN211791244U (en) | 2020-01-21 | 2020-01-21 | Alternating current filter with wide frequency range |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN211791244U (en) |
-
2020
- 2020-01-21 CN CN202020139562.5U patent/CN211791244U/en active Active
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN113224935A (en) | Alternating current filter with wide frequency range | |
| CN110719021A (en) | Grid-connected three-phase inverter common-mode EMI filter optimization design method | |
| EP3435509A1 (en) | System using a subcircuit shared between capacitors for providing reactive power | |
| CN115940153A (en) | Adaptive capacity adjusting method of active filter | |
| CN211791244U (en) | Alternating current filter with wide frequency range | |
| CN116054541B (en) | Filter for inhibiting motor drive system machine end overvoltage, design method and application | |
| CN210839320U (en) | LCLC type passive damping circuit, single-phase and three-phase grid-connected inverter system | |
| CN115173435A (en) | High-frequency oscillation suppression method, system and medium for flexible direct current transmission system | |
| Dovgun et al. | Passive filter design for power supply systems with traction loads | |
| JPH044814B2 (en) | ||
| CN114744627A (en) | CLC branch impedance matching method of low-frequency resonance suppression device | |
| CN114844344A (en) | EMI filter for airborne composite secondary power converter and design method thereof | |
| CN210867493U (en) | Multistage harmonic filter of shipborne electric equipment | |
| Chingale et al. | Harmonic filter design for line start permanent magnet synchronous motor | |
| CN115833772A (en) | Parallel filter | |
| CN210867491U (en) | Filter circuit, switching power supply and air conditioner | |
| CN114070025B (en) | Optimal design method for adjustable LCL filter of T-shaped three-level energy storage converter | |
| CN116845894A (en) | High-pass filter | |
| CN218850623U (en) | Conducted interference suppression circuit based on unbalanced circuit | |
| CN118100842B (en) | EMI filter based on remote plasma source | |
| CN217469758U (en) | Household appliance and three-phase PFC circuit and main control board thereof | |
| Ke et al. | Internal Characteristic Analysis and Optimal Application Scenario of 2 nd Filter and C-type Filter | |
| CN113364267B (en) | EMI filter based on improved FOSTER high-frequency model and design method thereof | |
| CN217590797U (en) | Three-phase power supply filter of alternating current power carrier equipment | |
| CN212459898U (en) | Filter device for no-load test of transformer |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| GR01 | Patent grant | ||
| GR01 | Patent grant |