CN111092542A - High-voltage filter for coal mine - Google Patents
High-voltage filter for coal mine Download PDFInfo
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- CN111092542A CN111092542A CN201911323744.6A CN201911323744A CN111092542A CN 111092542 A CN111092542 A CN 111092542A CN 201911323744 A CN201911323744 A CN 201911323744A CN 111092542 A CN111092542 A CN 111092542A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/12—Arrangements for reducing harmonics from ac input or output
- H02M1/126—Arrangements for reducing harmonics from ac input or output using passive filters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/44—Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/12—Arrangements for reducing harmonics from ac input or output
- H02M1/123—Suppression of common mode voltage or current
Abstract
The application discloses a high-voltage filter for coal mines, which is provided with a high-voltage alternating-current input end and a high-voltage alternating-current output end, wherein the high-voltage alternating-current output end is used for outputting filtered high-voltage alternating current to a high-frequency switching power supply which is used for supplying power to mining equipment, the high-voltage filter comprises a two-stage LC filter circuit, the first-stage LC filter circuit comprises a piezoresistor circuit connected with the high-voltage alternating-current input end in parallel, the piezoresistor circuit is formed by connecting one or more piezoresistors in series, the first-stage LC filter circuit also comprises a first capacitor circuit connected with the high-voltage alternating-current input end in parallel, the first capacitor circuit comprises an X1 capacitor or a plurality of X1 capacitors in series, the first-stage LC filter circuit also comprises a differential mode inductor and a first common mode inductor, the second-stage LC filter circuit comprises a second common mode inductor, the second-stage LC filter circuit also comprises a second capacitor, the second capacitor circuit is composed of one X1 capacitor or a plurality of X1 capacitors connected in series.
Description
Technical Field
The invention belongs to the technical field of filter components, and relates to a scene for testing electromagnetic compatibility of a product for a coal mine, in particular to a high-voltage filter for the coal mine and a design method thereof.
Background
Currently, electromagnetic compatibility (EMC) is an increasingly critical factor in the electrical and electronics industry, including the coal mine industry where there are a large number of electrical circuits and equipment at the job site.
According to the specifications and requirements of the coal mine industry, all mining equipment of the safety monitoring system, whether aboveground or underground, needs to have anti-electromagnetic interference capability. To meet the relevant requirements, it is necessary to perform tests on the downhole equipment relating to factors such as electromagnetic radiation immunity, burst immunity, surge (surge) immunity of the ac power port, dc power and signal ports, and to compare the test data with qualification data.
According to traditional mining equipment, underground high-voltage alternating current is input, is connected with a power frequency transformer, is converted into low-voltage rectification and then is connected with a switching power supply module for voltage conversion, and outputs intrinsic safety or non-safety voltage to supply power for intrinsic safety products such as sensors or non-installed equipment. The new generation of mining products omits a power frequency transformer, and high-voltage alternating current input directly supplies power to a wide-range input DC/DC high-frequency switching power supply, and is converted into intrinsic safety or non-safety voltage to supply power to subsequent electric equipment. The method has the advantages of improving the overall efficiency of the product, reducing the power frequency transformer, saving space and cost, and correspondingly increasing the difficulty of passing electromagnetic compatibility.
In the prior art, measures such as the layout of circuit boards inside equipment composed of various systems, connecting lines between Printed Circuit Boards (PCBs), the wiring of the PCBs, the shielding and grounding of sensitive components and parts are adjusted, so that the electromagnetic interference and radiation can be weakened to a certain extent. However, the principle of these measures is not to cancel the interference and radiation at the very source, but to remedy the interference after it has entered the subsequent circuit.
Disclosure of Invention
The inventor considers that the working voltage level of the alternating current power supply port is high and is in the frontmost end of the whole power supply system, so that the interference elimination at the frontmost end is the first choice for the safety monitoring system to pass the EMC experiment. The invention mainly aims at the mining products without power frequency transformer isolation, an EMC filter is arranged at a high-voltage alternating current input port, the problem of anti-interference of a system per se is solved, interference energy generated by the system per se can be eliminated on the filter, and the transmission of interference to an underground power grid or the radiation interference of surrounding electric equipment is prevented.
Specifically, the inventor develops a power filter which is applied to an EMC filter of a high-voltage input port in the coal mine industry. The input voltage level may be a downhole ac voltage, such as 127V, 380V, 660V, and the device power level may be designed at 250W. The EMC filter mainly comprises a lightning protection device, a safety capacitor, a common mode inductor, a differential mode inductor and the like, is a composite filter, can solve the problem of interference resistance of a system per se, and can filter interference energy generated by the system per se through the filter, so that electromagnetic interference/radiation is prevented from being transmitted to an underground power grid or peripheral equipment of the underground power grid.
According to an embodiment of the invention, a high-voltage filter for coal mines is provided, which comprises a high-voltage alternating current input end and a high-voltage alternating current output end, wherein the high-voltage alternating current output end is used for outputting filtered high-voltage alternating current to a high-frequency switching power supply which is used for supplying power to mining equipment, the high-voltage filter comprises a two-stage LC filter circuit, the first-stage LC filter circuit comprises a piezoresistor circuit connected with the high-voltage alternating current input end in parallel, the piezoresistor circuit is formed by connecting one or more piezoresistors (RV1, RV2 and RV3) in series, the first-stage LC filter circuit further comprises a first capacitor circuit connected with the high-voltage alternating current input end in parallel, the first capacitor circuit is formed by connecting one X1 capacitor or a plurality of X1 capacitors (Cx2, Cx4 and Cx6) in series, and the first-stage LC filter circuit further comprises a differential mode inductor (L1, L1 and Cx6, L4) and a first common mode inductor (L2), the second stage LC filter circuit comprises a second common mode inductor (L3), the second stage LC filter circuit also comprises a second capacitor circuit connected with the high voltage alternating current output end in parallel, and the second capacitor circuit consists of an X1 capacitor or is formed by connecting a plurality of X1 capacitors (Cx1, Cx3 and Cx5) in series.
Aiming at the upgrading and reforming requirements of the coal mine industry, the invention can comprehensively pass the anti-interference performance surge (impact) immunity test and the pulse group immunity test, and simultaneously inhibit the conduction and radiation interference of the self to the underground power grid and peripheral equipment.
Drawings
Fig. 1 is a schematic circuit diagram of a high-voltage EMC filter for a coal mine according to an embodiment of the present invention;
fig. 2 shows the distribution of the common mode interference signal CM and the differential mode interference signal DM of the EMC signal;
FIG. 3 is a circuit schematic of a single stage EMC filter;
FIG. 4 is a circuit schematic of a two-stage EMC filter;
fig. 5 is a circuit schematic of a dual stage LC filter network configuration.
Detailed Description
The following describes the embodiments in further detail with reference to the accompanying drawings.
It will be appreciated by those skilled in the art that while the following description refers to numerous technical details relating to embodiments of the present invention, this is by way of example only, and not by way of limitation, to illustrate the principles of the invention. The present invention can be applied to a place other than the technical details exemplified below as long as it does not depart from the principle and spirit of the present invention.
In addition, in order to avoid limiting the description of the present specification to a great extent, in the description of the present specification, it is possible to omit, simplify, and modify some technical details that may be obtained in the prior art, as would be understood by those skilled in the art, and this does not affect the sufficiency of disclosure of the present specification.
The present invention will be described in detail with reference to the accompanying drawings.
Fig. 1 is a schematic circuit diagram of a high-voltage EMC filter for a coal mine according to an embodiment of the present invention. As shown in FIG. 1, CX1～CX6Is X1 capacitance, has high peak voltage resistance, and V is more than 0.33uF when the capacitance C isP＝4e(0.33-C)KV. When the capacitor fails, electric shock cannot be caused, personal safety is not endangered, and meanwhile, because the working voltage of the input port is high, the reliability can be improved by selecting a series connection mode. The resistors R1-R12 are used to form a discharge circuit when discharging the X capacitor.
C1-C8 are Y1 capacitors, and are also connected in series for filtering common mode interference in the circuit. Due to the physical characteristics of the Y capacitor, in addition to meeting the withstand voltage requirement of normal operation, it is also required to leave sufficient safety margin in terms of electrical and mechanical properties to avoid the occurrence of breakdown short circuit.
L2 and L3 are common mode inductors, and L1 and L4 are differential mode inductors, and the design method is described later.
RV1, RV2, RV3 are piezo-resistors, select the series connection mode for use, can increase high-voltage circuit's security and reliability.
It should be noted that the numbers of the capacitors, the resistors and the piezoresistors are only examples, and may be changed according to actual requirements.
Next, a design process of the EMC filter of the present invention is explained.
EMC signals include common mode interference signal CM and differential mode interference signal DM, which are distributed as shown in fig. 2. According to experience, the EMC filter is generally used to suppress noise in a frequency range below 30MHz, and has a certain suppression effect on transmission interference above 30MHz, and can be divided into 3 frequency bands in a cutoff frequency range: under 100KHz, the differential mode interference is mainly inhibited; within the range of 0.1-1 MHz, common mode interference is mainly inhibited, and differential mode interference is assisted; the common mode interference is mainly inhibited within the range of 1-30 MHz. In addition, attention must be paid to the problem of electromagnetic wave coupling with surrounding electric devices, and auxiliary suppression means such as grounding and shielding of sensitive components should be considered as appropriate. In addition, since parasitic capacitance is generated between media during high-frequency switching, the parasitic capacitance can generate an unexpected unbalance phenomenon on a branch circuit of a circuit, and common-mode interference is mainly coupled into a current loop through the parasitic capacitance, common-mode noise occupies a main component for the high-frequency switching power supply, and the influence of the common-mode noise is larger than that of differential-mode noise.
The main performance indexes of the EMC filter include insertion loss, frequency characteristics, impedance matching, rated voltage and current values, leakage current, use environment, reliability of itself, and the like. The maximum design consideration is 3 items of rated voltage and current values, insertion loss and leakage current.
Insertion loss (also called insertion attenuation) is a main index for evaluating the performance of an EMC filter. Insertion loss (A)dB) Is a function of frequency and is expressed in dB. Let the noise power transmitted to the load before and after the insertion of the EMC filter be P1, P2, respectively, and have the formula:
AdB＝10lg(P1/P2) (1)
assuming that the load impedance Z remains constant before and after insertion, P1 is V1 2/Z,P2＝V2 2and/Z. In the formula V1Is the voltage, V, applied directly to the load by a source of noise2Noise voltage on a load is obtained after an EMC filter is inserted between a noise source and the load and is substituted into the formula (1):
AdB＝20lg(V1/V2) (2)
the insertion loss is expressed in decibels (dB), the greater the decibel value, the greater the ability to suppress noise interference.
The leakage current is the current flowing between the phase line L and the neutral line N of the filter and the ground E under the rated voltage, the leakage current is caused by the capacitance of the ground, and the leakage current of the phase line or the neutral line to the ground does not exceed 0.8mA due to strict regulations on the leakage current in consideration of safety.
The formula for calculating the drain current of the EMC filter is as follows:
ILD＝2πfCVC(3)
f is the grid frequency.
Taking the single-stage EMC filter circuit of fig. 3 as an example, C ═ C3+C4，VCIs C3、C4The voltage drop, namely the voltage of the output end to the ground, is selected according to the highest rated working voltage, Vc is 660V/2 is 330V, and the leakage current is in direct proportion to the common-mode capacitor C. The smaller the leakage current is, the better the safety is, which typically should be a few hundred microamperes.
Finally, the design is made according to the schematic diagram of the two-stage EMC filter of fig. 4. When an EMC filter is designed, parameters of corresponding components need to be designed for cutoff frequencies different from common mode interference and differential mode interference. The following describes the common mode interference resistance design flow and the differential mode interference resistance design flow of the EMC filter, respectively.
(1) Common-mode interference resistant filter
Cut-off frequency f of the anti-common mode part of an EMC filterCMIs calculated as
Wherein, CCM＝C3+C4
The following can be obtained by the formula (3):
wherein, C3＝C4
In practical design, the common-mode capacitance C is firstly determined according to the safety standard of leakage current3、C4If the safety standard is exceeded, the value of the common-mode capacitance needs to be reduced. According to engineering design evaluation, the cut-off frequency of the filter is generally required to be about 1/10 of the working frequency of the switching power supply, and the cut-off frequency f of the common-mode interference can be determined by determining the frequency of the switching power supply behind the filterCM. The previously obtained C3And the determined value of fCMThe value of (3) is substituted for the value of (4), and the common mode inductance L can be obtained1The value of (c).
(2) Anti-differential mode interference filter
Cut-off frequency f of anti-differential mode part of EMC filterDMThe calculation formula (c) is as follows:
wherein, CDM＝C1＝C2
In the actual calculation process, as well as the step of calculating the common-mode filter, the required C is first determinedDMAnd fDMIs substituted into the formula (6) derived from the formula (5), and L is calculatedDMThe value of (c). Then, the differential mode inductance L is calculated by the formula (7)3Size of (here L)3The inductors are independent inductors, and can be simply wound to a common mode inductor L1，L2In the middle), the leakage inductance value of the common mode inductor is 0.5% -2% of the common mode inductance value under the general condition.
L3＝0.5(LDM-LLeakage inductance) (7)
After the above steps, the parameters of all components in the EMC filter of the switching converter for different frequencies can be calculated.
For the design of the second-stage LC filter, the design can be carried out according to a two-stage LC filter network. The filter adopts a double-stage LC filter network structure, and has a better effect in the aspect of filtering higher harmonics, as shown in FIG. 5, the frequency domain transfer function is as follows:
since the LC network resonates, a large current (voltage) spike occurs, and the resonant values of the network at three frequency points must be limited, otherwise a larger EMC disturbance is generated. The three frequency points are:
resonant frequency of the first stage filter:
resonance frequency of the second stage filter:
the third frequency point is the working switching frequency f of the power converter0
The amplitudes of the transfer functions corresponding to the three frequency points are respectively
H1(s＝j2πf1)＝C1/C2(11)
H2(s＝j2πf2)＝L2/L1(12)
The analysis was as follows:
to limit f1The resonance peak of the spot requires insertion attenuation of 20lg (H)1)＝20lgC1/C2< 0, i.e. C1/C2Less than 1, according to engineering experience value, taking ratio range
C1/C2＝0.2～0.4 (14)
To limit f2Resonance peak of point, taking L in the same way2/L1＝0.2～0.4(15)
To limit f0Resonance peak of point, requirement 20lgH3＝-20～-150dB，
H3＝0.2～0.4 (16)
Wherein: 1. equations (14) to (16) define ratios, only two parameters being independent; 2. because the filter is required to filter out the differential mode ripple noise, the capacitor should be selected to be a little larger.
The parameters of the schematic (as shown in fig. 4) calculated from the previous formula are as follows: l is1＝1.56mH， L2＝0.6mH，C1＝0.3uF，C2＝0.7uF，C3＝C4＝2.2nF，C5＝C6＝2.2nF。
Through electromagnetic compatibility experimental equipment, after surge and pulse group tests are carried out, the following parameters can be further designed: l is1＝3mH，L2＝1mH，C1＝0.47uF，C2＝0.82uF，C3＝C4＝1.1nF，C5＝C6＝1.1nF， LDifferential mode inductor＝52uH。
From the above calculated values, the EMC filter (as shown in fig. 1) as the final product was selected as follows:
L2＝3mH，L3＝1mH，L1＝L4＝52uH，Cx2＝Cx4＝Cx6＝1.5uF， Cx1＝Cx3＝Cx5＝2.2uF，C1＝C2＝C3＝C4＝C5＝C6＝C7＝C8＝2.2nF。
R1-R12 are used as discharge capacitors of the X capacitor, and the resistance value can be selected to be between 104-205. RV1, RV2 and RV3 are piezoresistors and can be selected from model 751KD 14.
The calculated values are merely examples, and the number and parameters of each component may be adjusted according to requirements in practical applications.
As described above, for the measures taken in the surge immunity experiment, because the input voltage value is too high, the embodiment of the present invention adopts a mode of using a voltage dependent resistor, and has the advantages of fast action response, large flow capacity, low residual voltage, bidirectional immunity and the like. If the surge level requirement is too high, the piezoresistor can be connected with the gas discharge tube in parallel, and the follow current problem of the circuit is also considered. Considering that the working voltage is higher than 660V, the piezoresistors are used in series in an actual circuit, the maximum voltage which can be borne by the converter after the filter is calculated, and the maximum residual voltage value of the piezoresistors is selected to select the type of the piezoresistors. The input end of the power converter is also generally provided with a piezoresistor or a TVS (transient suppression diode) for secondary surge protection, and the EMC filter is not provided with a TVS for repeated protection.
Finally, those skilled in the art will appreciate that various modifications, adaptations, and alternatives to the above-described embodiments of the present invention can be made without departing from the scope of the invention as defined in the following claims.
Claims (5)
1. A high-voltage filter for coal mines has a high-voltage alternating current input terminal and a high-voltage alternating current output terminal, the high-voltage alternating current output terminal is used for outputting filtered high-voltage alternating current to a high-frequency switching power supply, the high-frequency switching power supply is used for supplying power to mining equipment,
the high-voltage filter comprises a first-stage LC filter circuit and a second-stage LC filter circuit which are cascaded, the first-stage LC filter circuit comprises a piezoresistor circuit which is connected with the high-voltage alternating-current input end in parallel, the piezoresistor circuit is formed by connecting one or more piezoresistors (RV1, RV2 and RV3) in series,
the first-stage LC filter circuit also comprises a first capacitance circuit connected with the high-voltage alternating-current input end in parallel, the first capacitance circuit consists of an X1 capacitor or a plurality of X1 capacitors (Cx2, Cx4 and Cx6) which are connected in series,
the first stage LC filter circuit further comprises differential mode inductors (L1, L4) and a first common mode inductor (L2),
the second stage LC filter circuit includes a second common mode inductance (L3),
the second-stage LC filter circuit also comprises a second capacitance circuit connected with the high-voltage alternating-current output end in parallel, and the second capacitance circuit consists of an X1 capacitor or a plurality of X1 capacitors (Cx1, Cx3 and Cx5) which are connected in series.
2. The high voltage filter for coal mines as set forth in claim 1, wherein the first stage LC filter circuit further comprises a third capacitor circuit connected in series with the first common mode inductor (L2) and connected to ground, the third capacitor circuit being formed by a plurality of Y1 capacitors (C1-C4) connected in series.
3. The high voltage filter for coal mines as set forth in claim 1, wherein the second stage LC filter circuit further comprises a fourth capacitive circuit connected in series with the second common mode inductor (L3) and connected to ground, the fourth capacitive circuit being formed by a plurality of Y1 capacitors (C5-C8) connected in series.
4. The high-voltage filter for coal mines as set forth in claim 1, wherein each of the X1 capacitors (Cx2, Cx4, Cx6) in the first capacitor circuit is connected in parallel with a first resistor circuit, and the first resistor circuit is composed of one resistor or a plurality of resistors (R2, R4, R6, R8, R10, R11) connected in series.
5. The high voltage filter for coal mine according to claim 1, wherein each of the X1 capacitors (Cx1, Cx3, Cx5) in the second capacitor circuit is connected in parallel with a second resistor circuit, and the second resistor circuit is composed of one resistor or a plurality of resistors (R1, R3, R5, R7, R9, R12) connected in series.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20150263260A1 (en) * | 2008-07-15 | 2015-09-17 | D-Wave Systems Inc. | Input/output systems and devices for use with superconducting devices |
| CN209472393U (en) * | 2019-03-29 | 2019-10-08 | 中国电子科技集团公司第三十八研究所 | A kind of spaceborne power filter device |
| CN209608539U (en) * | 2019-04-12 | 2019-11-08 | 深圳市合派电子技术有限公司 | A kind of power circuit of electromagnetic compatibility |
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- 2019-12-20 CN CN201911323744.6A patent/CN111092542A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20150263260A1 (en) * | 2008-07-15 | 2015-09-17 | D-Wave Systems Inc. | Input/output systems and devices for use with superconducting devices |
| CN209472393U (en) * | 2019-03-29 | 2019-10-08 | 中国电子科技集团公司第三十八研究所 | A kind of spaceborne power filter device |
| CN209608539U (en) * | 2019-04-12 | 2019-11-08 | 深圳市合派电子技术有限公司 | A kind of power circuit of electromagnetic compatibility |
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Application publication date: 20200501 |