CN1086256C - Combined power filter with both active and passive parts - Google Patents
Combined power filter with both active and passive parts Download PDFInfo
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- CN1086256C CN1086256C CN00109624A CN00109624A CN1086256C CN 1086256 C CN1086256 C CN 1086256C CN 00109624 A CN00109624 A CN 00109624A CN 00109624 A CN00109624 A CN 00109624A CN 1086256 C CN1086256 C CN 1086256C
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The present invention relates to a combined power filter composed of an active filter and a passive filter, which is composed of an active filter, a passive filter, a transformer and a control circuit, wherein the control circuit comprises a current sensor, a harmonic detecting circuit, a regulator, a pulse width modulation control circuit and a drive circuit. The current sensor causes the current information of an electric network to be converted into voltage signals to be input into the harmonic detecting circuit, the harmonic current signals are obtained to be sent to the regulator, and the demand signals for controlling current are obtained. The output voltage of the active filter is controlled by the demand signals to realize the filtration. The present invention has the advantages of low cost and good economic practicability.
Description
The present invention relates to a kind of combined power filter with both of active and passive formation, belong to the electrical engineering technical field.
Develop rapidly along with power electronic technology, various power electronic equipments have obtained to use widely in electric power system, industry (particularly metallurgy, iron and steel, chemical industry etc.), traffic, building automatic and family, and this just makes the harmonic pollution situation in the electrical network serious day by day.And, be used to improve the easy and system impedance generation resonance of capacitor of power factor in the electrical network, thereby cause harmonic wave to amplify.This has all increased the weight of the harmonic pollution in the electrical network.
Harmonic wave in the electrical network not only endangers electrical network itself but also endangers its peripheral equipment.Harmonic wave in the electrical network makes the efficient of production, transmission and the utilization of electric energy reduce on the one hand, makes device of overheating of electrical, produces vibration and noise, and ageing of insulation, useful life are reduced, even break down or burn.Simultaneously, harmonic wave can cause that also parallel resonance or series resonance appear in the electric power system part, and harmonic content is amplified, and causes equipment burnouts such as capacitor.Harmonic wave also can cause relay protection and automatics misoperation, and electric energy metrical is caused confusion.For the electric power system outside, harmonic wave can produce serious disturbance to communication apparatus and electronic equipment.
Harmonic pollution situation in the electrical network is serious day by day, thereby, for the also increase day by day of demand of harmonic treating apparatus.And harmonic wave control also is the important component part of building " green electrical network ".Present harmonic treating apparatus mainly contains two big classes: passive filtration unit and active filter.
Passive filtration unit wherein can be referring to " harmonic analysis of HVDC (High Voltage Direct Current) transmission system and filtering " book of being published by hydraulic and electric engineering publishing house in August, 1994, and its circuit structure diagram is seen Fig. 1, and its equivalent circuit diagram under the harmonic wave effect as shown in Figure 2.
Can calculate system harmonics according to Fig. 2 is:
First of equal sign the right is the result of harmonic current effect in the following formula, and second is the result of harmonic voltage effect.By first as can be seen, when the frequency of harmonic current consistent with the resonance frequency of filter,
, ZF/Zs → ∞, first result also is approximately equal to zero, and this has just realized the inhibition for the load harmonic current.
Except above shortcoming, passive filter also has following shortcoming:
1, the compensation performance difference is because the parameter of capacitor and inductance exists error; In running, will change because of the aging influence of variation, self-heating and the capacitor insulation of environment temperature; Simultaneously, can there be certain deviation in system frequency in running.These reasons all can cause the resonance frequency of harmonic frequency and filter inconsistent, and the impedance that presents of filter at this moment will depart from its minimum, and the filter filtering effect is degenerated.
2, bad dynamic performance is when the load current dynamic change, and it is to the inhibition weak effect of harmonic current
3, compensation performance be subjected to system impedance influence by formula (1) as can be known, passive filter is decided by Zs/ZF to the filter effect of load harmonic current, therefore, the variation of system impedance will influence its filter effect
Even 4 in ideal conditions, also can only produce reasonable inhibition effect to the specific times harmonic electric current
5, bulky, it is more to take up room
Existing active filter can be referring to nineteen ninety-five " Toyo Electric Mfg Co., Ltd.'s product description ".Its theory diagram as shown in Figure 3.Its basic principle is: active filter phase electrical network is injected with load harmonic wave size is consistent but the electric current that phase place is opposite by control, so just can make power network current is sine wave, thereby, realized the purpose of harmonic carcellation electric current.
The shortcoming of present active power filtering technology can mainly contain referring to Tsing-Hua University's thesis for the doctorate " research of novel combined power filtering system " in 1997:
1, because the fundamental voltage of AC power is applied directly on the inverter, and offset current provides by inverter fully, therefore, the capacity of inverter must be very big
2, because the power electronic device cost is higher at present, the price of this system is very expensive
3,, need further to improve because testing circuit is subject to the influence that error is disperseed and debugged to device parameters, and this can influence its compensation performance
4, because active filter adopts brand-new structure, be unsuitable for original passive filtration unit is transformed
The objective of the invention is to design a kind of passive active synthesis filter.It not only can overcome the shortcoming of independent use passive filter and active filter, and can draw both advantages, to obtain a kind of good wave filtering effect, lower-cost novel electric power filter.
The combined power filter with both of the active and passive formation of the present invention's design, form by active filter, passive filter, transformer and control circuit, one end and the electrical network of passive filter link, one end of the other end and transformer secondary output links, the mutual short circuit of the other end of transformer secondary output together, the mid point of inverter bridge leg links in one end on the former limit of transformer and the active filter, and the mutual short circuit of the other end on former limit together.Control circuit comprises current sensor, harmonics detection circuit, adjuster, control circuit for pulse-width modulation and drive circuit.Current sensor is transformed into input harmonics testing circuit behind the voltage signal with the current signal of electrical network, obtain the mains by harmonics current signal, this signal is sent into adjuster, the command signal of the feedback signal of the capacitance voltage in active filter controlled electric current after regulating, and send into control circuit for pulse-width modulation, symbol according to command signal produces control signal corresponding, promptly when the command signal of a phase wherein greater than zero the time, produce a signal, send into drive circuit, through shaping, amplify, after the isolation, make the switching tube conducting of brachium pontis on the inverter bridge with this mutually corresponding active filter, the switching tube of following brachium pontis turn-offs; If less than zero the time, produce a signal, send into drive circuit, after shaping, amplification, isolation, make the switching tube of brachium pontis on the inverter bridge with this mutually corresponding active filter turn-off the switching tube conducting of following brachium pontis, with the output voltage of control active filter, realize filtering.
Device of the present invention has the following advantages:
1, cost is low, economic and practical good: the power of the active part among the present invention is less, calculate with reference to the price standard that provides in IEEE Trans.Ind.Appl.Vol (33) No.4 (1997) " the Effectiveness of Harmonic Mitigation Equipment for CommercialOffice Buildings " literary composition, the price price $227.3/kVA of this filter, the price ($200/kVA of this and passive filtration unit) very nearly the same.If original passive filtration unit is transformed, its improvement cost only is $50/kVA.
2, filtering performance is good: for rectification load, after equipment dropped into, in the power network current 5 times, 7 times, 11 times, 13 subharmonic current content were respectively 1.7%, 1.4%, 0.8%, 0.9%, and this moment, the power network current waveform was more satisfactory sine wave.Current waveform contrasts referring to Fig. 7 in the electrical network before and after filter drops into.The actual running results shows that this filter has following characteristics: the filter effect of filtering system is subjected to the influence of power system impedance little; Can not produce serial or parallel connection resonance between power system impedance and the passive filter.
Description of drawings:
Fig. 1 is the passive filter circuit theory diagrams.
Fig. 2 is the one phase equivalent circuit figure of passive filter under the harmonic wave effect.
Fig. 3 is the active filter circuit schematic diagram.
Fig. 4 is the circuit theory diagrams of apparatus of the present invention.
Fig. 5 is the equivalent circuit diagrams of apparatus of the present invention under the harmonic wave effect, and wherein Fig. 5 a is one phase equivalent circuit figure, and Fig. 5 b is the equivalent circuit diagram under load harmonic current Ilh acts on separately, and Fig. 5 c is the equivalent circuit diagram under mains by harmonics voltage U sh acts on separately.
Fig. 6 is pulse-width modulation (PWM) control circuit schematic diagram.
Fig. 7 is current waveform contrast in the electrical network before and after apparatus of the present invention drop into, and wherein, Fig. 7 a is a current waveform in the electrical network before apparatus of the present invention put into operation, and Fig. 7 b is apparatus of the present invention current waveforms in the electrical network of back that put into operation.
Below in conjunction with accompanying drawing, introduce content of the present invention in detail.
Of the present invention active as follows with the operation principle passive synthesis filter:
Suppose that active filter is the ideal controllable voltage source, harmonic load is a current source.Under three symmetrical situations, its one phase equivalent circuit figure such as Fig. 5 (a) listen and show.U wherein
SfBe the first-harmonic part in the supply voltage, U
ShIt is the harmonic wave part in the supply voltage; I
SfBe the first-harmonic part in the source current, I
ShBe the harmonic wave part in the source current; I
LfBe the first-harmonic part in the load current, I
LhBe the harmonic wave part in the load current; Z
FIt is the passive filter impedance; Z
s(L
s) be system impedance.
Under the situation of not taking into account system loss, do not contain the first-harmonic composition in the active filter output voltage.Can be broken down into Fig. 5 (b) and Fig. 5 (c) according to principle of stacking Fig. 5 (a).For harmonic current source ILh, the equivalent electric circuit under it acts on separately is shown in Fig. 5 (b).At this moment, active filter can be regarded a harmonic impedance Zc as.When Uc=ZF * ILh, the harmonic impedance Zc under the each harmonic frequency is constantly equal to-ZF, i.e. ZF+Zc=0, and all like this load harmonic current ILh will flow into the passive filter branch road, and the filter effect of passive filter is improved.For the harmonic wave composition Ush in the system voltage, the equivalent electric circuit under it acts on separately is shown in Fig. 5 (c).At this moment, active filter can be regarded a controlled voltage source as.When UC=Ush, the harmonic current Ish that Ush produces will be zero, like this harmonic current with regard to having suppressed to cause owing to system harmonics voltage.Above two kinds of information summaries are got up, when active filter output voltage U C=Ush+ZF * ILh, will realize inhibitory action all harmonic currents in the system.
Because active filter voltage U C=Ush+ZF * ILh, be much smaller than line voltage, this makes that the capacity of the Capacity Ratio shunt active power filter of active filter is much smaller in the combined power filtering system, be more suitable for jumbo harmonic load is compensated, its initial outlay and operating cost are lower than shunt active power filter.Thereby have the low and good advantage of active filter filtering performance of passive filter cost simultaneously, have very strong practicality and economy.
PWM (pulse-width modulation) control circuit schematic diagram is that example is introduced its course of work referring to Fig. 6 with a mutually.As a phase command signal Ia
*Greater than zero the time, low level of comparator C omp-A output is to the input of not gate IC1:A, not gate IC1:A just exports the D end of a high level to d type flip flop IC3:A, when the clock end CLK of d type flip flop has a rising edge to arrive, this high level just makes high level of its positive output end Q output, this high level is sent in the drive circuit, thereby makes switching tube S1 conducting; Simultaneously, this high level also just makes low level of its negative output Q output, and this low level is sent in the drive circuit, thereby switching tube S2 is turn-offed.On the contrary, as a phase command signal Ia
*Less than zero the time, low level of the output of d type flip flop makes switching tube S1 turn-off the S2 conducting.The control procedure and a of other two-phases are similar.The output voltage that like this, just can guarantee active filter equals (Ush+ZF * Ilh)
*N, and then guarantee that the integrated filter device has comparatively ideal filter effect.
Not gate IC2:A, IC2:B among the figure, IC2:C, RY and CY constitute a square-wave oscillator.The output of supposing not gate IC2:A when initial is a low level, this high level is input to IC2:B makes it be output as high level, this high level carries out positive charge for capacitor C Y through resistance R Y, when B point current potential is higher than the threshold voltage of IC2:C, the IC2:C output low level, the input that this low level is input to IC2:A makes its output high level, simultaneously, the output of IC2:B is a low level, like this, IC2:A is just to capacitor discharge, and when B point current potential was lower than the threshold voltage of IC2:C, IC2:C exported high level.So, discharge and recharge repeatedly just and can obtain the certain square-wave pulse of one-period at the output of IC2:C, this square-wave pulse is delivered to the clock end of d type flip flop after IC2:D eurymeric is also reverse.Last surface analysis is arranged as can be known, only when rising edge appearred in clock end, the state of the output Q of d type flip flop just may change, thereby the on off state that causes switching tube changes.Therefore, the rising edge of the state variation of switching tube and square-wave pulse is synchronous.Can make the switching frequency of active filter keep constant like this, exactly.
Claims (1)
1, a kind of combined power filter with both of active and passive formation, it is characterized in that this device is made up of active filter, passive filter, transformer and control circuit, one end and the electrical network of passive filter link, one end of the other end and transformer secondary output links, the mutual short circuit of the other end of transformer secondary output together, the mid point of inverter bridge leg links in one end on the former limit of transformer and the active filter, and the mutual short circuit of the other end on former limit together; Control circuit comprises current sensor, harmonics detection circuit, adjuster, control circuit for pulse-width modulation and drive circuit; Current sensor is transformed into input harmonics testing circuit behind the voltage signal with the current signal of electrical network, obtain the mains by harmonics current signal, this signal is sent into adjuster, the command signal of the feedback signal of the capacitance voltage in active filter controlled electric current after regulating, and send into control circuit for pulse-width modulation, symbol according to command signal produces control signal corresponding, promptly when the command signal of a phase wherein greater than zero the time, produce a signal, send into drive circuit, through shaping, amplify, after the isolation, make the switching tube conducting of brachium pontis on the inverter bridge with this mutually corresponding active filter, the switching tube of following brachium pontis turn-offs, if less than zero the time, produce a signal, send into drive circuit, through shaping, amplify, after the isolation, the switching tube of brachium pontis on the inverter bridge with this mutually corresponding active filter is turn-offed, the switching tube conducting of following brachium pontis with the output voltage of control active filter, realizes filtering.
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| CN00109624A CN1086256C (en) | 2000-06-16 | 2000-06-16 | Combined power filter with both active and passive parts |
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| CN00109624A CN1086256C (en) | 2000-06-16 | 2000-06-16 | Combined power filter with both active and passive parts |
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| CN1086256C true CN1086256C (en) | 2002-06-12 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100355177C (en) * | 2005-12-18 | 2007-12-12 | 江苏省电力公司无锡供电公司 | Mixed THF based on symmetrical component method |
| CN100407539C (en) * | 2007-02-15 | 2008-07-30 | 湖南大学 | Control method for high-power active filter |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100336276C (en) * | 2003-09-25 | 2007-09-05 | 西安交通大学 | Parallel mixed power filter for electrified railway |
| CN100369344C (en) * | 2003-10-24 | 2008-02-13 | 华南理工大学 | Synthetized compensation device in electric power system and synthetized compensation method |
| CN100399666C (en) * | 2004-08-26 | 2008-07-02 | 盈正豫顺电子股份有限公司 | Three-phase three-wire type active electric filter |
| CN100344042C (en) * | 2004-11-25 | 2007-10-17 | 郑州大学 | Method for realizing driving and power generation by using harmonic wave and apparatus using same method |
| CN100346550C (en) * | 2005-07-18 | 2007-10-31 | 西安交通大学 | Control method for restraining oscillate based on mixed electric power filter |
| CN1851973B (en) * | 2006-04-30 | 2010-05-12 | 西安交通大学 | Wide-frequency-band high-attenuation common-mode conductive electromagnetic interference shunt mixed type wave filter |
| CN102222910A (en) * | 2010-04-15 | 2011-10-19 | 西门子公司 | Filtering system |
| CN102545223A (en) * | 2012-01-04 | 2012-07-04 | 北京华东电气股份有限公司 | High-voltage dynamic filtering power-saving device for mine |
| CN103178526A (en) * | 2013-04-10 | 2013-06-26 | 西安布伦帕电力无功补偿技术有限公司 | Composite filter |
| CN104201682B (en) * | 2014-09-25 | 2016-07-20 | 湖北瑞力电气有限公司 | A kind of high pressure passive filtering cabinet of built-in annular reactor |
-
2000
- 2000-06-16 CN CN00109624A patent/CN1086256C/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100355177C (en) * | 2005-12-18 | 2007-12-12 | 江苏省电力公司无锡供电公司 | Mixed THF based on symmetrical component method |
| CN100407539C (en) * | 2007-02-15 | 2008-07-30 | 湖南大学 | Control method for high-power active filter |
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| CN1274977A (en) | 2000-11-29 |
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