CN1095233C - Serial active filter method and system based on fundamental flux compensation - Google Patents

Serial active filter method and system based on fundamental flux compensation Download PDF

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CN1095233C
CN1095233C CN99120103A CN99120103A CN1095233C CN 1095233 C CN1095233 C CN 1095233C CN 99120103 A CN99120103 A CN 99120103A CN 99120103 A CN99120103 A CN 99120103A CN 1095233 C CN1095233 C CN 1095233C
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fundamental
current
harmonic
fundamental current
transformer
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CN1258948A (en
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陈乔夫
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

The present invention relates to a method and a system for a series active filter based on fundamental magnetic flux compensation. Fundamental signals of a bus bar distortion current are obtained by a fundamental detecting unit, a fundamental compensation current generator tracks the signals to generate a fundamental current, and the fundamental current is input into a secondary winding of a series transformer so that the main magnetic flux of the iron core of the series transformer is approximate to zero. Therefore, the primary winding of the transformer generates small voltage drop on a bus bar and forms high impedance to harmonic, a harmonic current is prevented from flowing into a power system, and parallel resonance can be suppressed. The volume of the active filter is small.

Description

Method and system based on the serial active filter of fundamental flux compensation
The invention belongs to the electric harmonic filter field.
Along with increasing of nonlinear load, power electronics load, harmonic wave is serious day by day to the pollution of electric power system.Electric harmonic can make motor, transformer, capacitor etc. produce supplementary load loss, overheated, vibration, even overload; Produce the harmonic wave overvoltage; Cause relay misoperation to do; Also can interfering TV, communication; The household electrical appliance operating mode is degenerated.In a word, harmonic wave has become big public hazards of electric power system.In order to suppress electric harmonic, experts and scholars have developed multiple electric harmonic filter both at home and abroad, conclude and get up can be divided into following two classes:
1, single tuned filter
Single tuned filter is in series by L, C, and is in parallel with system, and a single tuning branch road weakens a harmonic wave.The shortcoming of this kind filter is, about 20% the harmonic current of still having an appointment is scurried into electric power system; In addition, reliability is not high, then may cause parallel resonance if design is improper.
2, based on the serial active filter of harmonic current compensation
About this active filter, a large amount of research work have been carried out both at home and abroad.The external representative paper of having delivered has: " A practical approach to harmonic compensation in powersystem-series connection of passive and active filters ", Hideaki Fujita, IEEETransaction, Vol.27, No.6,1991.It is reported that title, Japan have model machine linked network trial run in system, China does not see the report of introducing the type filter as yet.China relevant expert has also carried out a large amount of research work in this field, the representative conduct that it is main: " based on the series hybrid type Monophase electric power active filter of instantaneous reactive power theory ", Wang Zhaoan, Proceedings of the CSEE, Vol.17, No.1,1997.1.But do not see the report of actual model machine hanging net operation as yet.
The basic principle of above-mentioned domestic and international research work is identical, all be from the actual electric network electric current, to detect harmonic current, (promptly from actual current the deduction fundamental current and obtain), produce one with this harmonic current equal and opposite in direction and opposite polarity offset current by compensation arrangement, this electric current is coupled in the system by current transformer, remove to offset harmonic current, make power network current only contain fundametal compoment.
Adopt this kind method that following three problems are arranged: 1). from the electric current of reality distortion, detect and deducted the harmonic current behind the first-harmonic and be difficult to, still have a large amount of articles to detect problem in that the monophase current harmonic wave is discussed so far; 2). utilize compensation arrangement to produce one and detected harmonic wave equal and opposite in direction, opposite polarity offset current is more difficult, because the harmonic spectrum broad, inertance elements such as current transformer are different to the different frequency response; 3). how to accomplish that the fundamental current pressure drop is approximately zero in the electrical network bus, to reduce the active filter capacity, this problem all is not resolved in discussion in the past.
The objective of the invention is at problems of the prior art and deficiency, propose to detect single-frequency, response is stable, the method for the serial active filter of easier realization and system thereof.
The said serial active filter based on fundamental flux compensation of the present invention mainly is made up of three unit: i.e. fundamental Current's Detection unit I, compensating fundamental wave electric current generating unit II and series transformer III.The formation of its system, method and principle are as follows:
1. method:
The said employing of the present invention based on the method for the serial active filter of fundamental flux compensation is:
A). from the electrical network bus current i of distortion, detect fundamental current signal i by fundamental Current's Detection unit I 1s
B). by compensating fundamental wave electric current generating unit II according to the fundamental current signal i that receives 1s, produce fundamental current i 1 *, and make fundamental current i 1 *From motion tracking fundamental current signal i 1s
C). with fundamental current i 1 *Deliver to paying among the square winding ax of series transformer III;
D). make fundamental current i 1 *Fundamental current i from motion tracking electrical network bus 1
E). make first-harmonic main flux Φ in the series transformer III iron core Ml≈ 0, grid side first-harmonic pressure drop U AX≈ 0, for the nth harmonic impedance Z AX (n)=nZ AX (1)
F). after above-mentioned steps, realize that series transformer III has stoped harmonic wave to scurry into electric power system.
2. system constitutes:
Electrical network bus 1 is provided with current transformer 2, and the output of current transformer 2 is connected with fundamental Current's Detection link 3, and fundamental Current's Detection unit I will detect its fundamental current signal i from the power network current i of distortion 1sAs output signal; Should detected output stream signal i 1sCarry and be connected to the input of compensating fundamental wave electric current generating unit II; Compensating fundamental wave electric current generating unit II is with the fundamental current i that is produced 1 *Output is connected to the square winding ax that pays of series transformer III, and its former side's winding AX is connected in the electrical network bus.
3. operation principle:
A). fundamental Current's Detection unit I is by on electrical network bus 1 current transformer 2 being set and fundamental Current's Detection link 3 is formed, current transformer 2 is placed on the electrical network bus 1, the distortion current i waveform of obtained electrical network bus 1 is delivered in the fundamental Current's Detection link 3, from the current waveform i of distortion, detected its fundamental current signal i by fundamental Current's Detection unit I 1sB). will from fundamental Current's Detection unit I, detect fundamental current signal i 1s, being transported among the compensating fundamental wave electric current generating unit II, compensating fundamental wave electric current generating unit II is according to the fundamental current signal i that receives 1s, produce fundamental current i 1 *, and from motion tracking fundamental current signal i 1sC). with the fundamental current i that produces among the compensating fundamental wave electric current generating unit II 1 *(number of turn of paying square winding is W to deliver to the square winding ax that pays of series transformer III Ax) in, (number of turn of former side's winding is W to its former side's winding AX AX) be connected in the electrical network bus fundamental current i 1 *Fundamental current i from motion tracking electrical network bus 1, and make in series transformer III iron core Central Plains, pay square winding ampere-turn equilibrium, that is: W AXI 1+ W AxI 1 *=0, thus make first-harmonic main flux Φ in the series transformer III iron core Ml≈ 0, series transformer III grid side first-harmonic pressure drop U AX≈ 0, and presents impedance Z for nth harmonic AX (n)=nZ AX (1), (Z AX (1)Be series transformer first-harmonic excitation impedance).Therefore, series transformer III stops harmonic wave to scurry into electric power system.
The said serial active filter based on fundamental flux compensation of the present invention has been compared following advantage with filter of the prior art:
1, the present invention only need detect first-harmonic from power network current, compares with detecting harmonic current, and fundamental frequency is single, and response is stable, easier realization.
2, the present invention only need utilize compensation arrangement to produce an offset current identical with detected fundamental current frequency, that size becomes to have reached ratio, compares with tracking of the prior art, generation harmonic current, and its implementation is much easier.
3, the present invention with the former side's windings in series of series transformer in the electrical network bus, when square winding is paid in the offset current injection, can make in the series transformer iron core first-harmonic main flux be approximately zero, at former side AX port fundamental current is zero impedance (or very Low ESR), thereby the filter capacity is less, and harmonic current is presented excitation impedance (being a very big impedance), thereby stop the harmonic current circulation.Can prevent that also parallel resonance from taking place.
Fig. 1: based on the schematic diagram of the serial active filter of fundamental flux compensation;
Fig. 2: the distortion current waveform i of electrical network bus and fundamental current i thereof 1Waveform;
Fig. 3: the current waveform i of the former side's winding of series transformer AX port 1
Fig. 4: the current waveform i of the series transformer side of paying winding ax port 1 *
Fig. 5: the serial active filter of fundamental flux compensation and parallel connection type passive filter are united the schematic diagram of use.
Below in conjunction with accompanying drawing serial active filter and the method thereof based on fundamental flux compensation of the present invention is further described.
Fig. 1 is the agent structure of patent of the present invention.
The formation of fundamental Current's Detection unit I is that current transformer 2 is set on electrical network bus 1, the electrical network bus distortion current i waveform of obtaining on the current transformer 2 (shown in the dotted line waveform among Fig. 2) is delivered in the fundamental Current's Detection link 3, from the current waveform of distortion, detected its fundamental current signal i by fundamental Current's Detection unit I 1s, this signal is sinusoidal wave, with the first-harmonic i of sensed current 1Same frequency, and its amplitude size and i 1In direct ratio.To from fundamental Current's Detection unit I, detect fundamental current signal i 1s, being transported among the compensating fundamental wave electric current generating unit II, compensating fundamental wave electric current generating unit II is according to the fundamental current signal i that receives 1s, produce fundamental current i 1 *, (said fundamental current i 1 *Fundamental current i with the electrical network bus 1Same frequency, size are proportional) and from the fundamental current i of motion tracking electrical network bus 1With the fundamental current i that produces among the compensating fundamental wave electric current generating unit II 1 *Deliver to paying among the square winding ax of series transformer III, its former side's winding AX is connected in the electrical network bus, and makes W AXI 1+ W AxI 1 *=0, thus make first-harmonic main flux Φ in the series transformer III iron core Ml≈ 0, series transformer III grid side first-harmonic pressure drop U AX≈ 0, and for the nth harmonic impedance Z AX (n)=nZ AX (1), (Z AX (1)Be series transformer first-harmonic excitation impedance).Thus, series transformer III stops harmonic wave to scurry into electric power system.
Tandem type filter according to the said technical scheme of the present invention is made both can use separately, also can unite use with the parallel connection type passive filter, also can unite use with shunt active power filter.
Fig. 5 is based on the serial active filter of fundamental flux compensation and the example that the parallel connection type passive filter is united use.

Claims (2)

1, a kind of method that adopts based on the serial active filter of fundamental flux compensation is characterized in that:
A). from the electrical network bus current (i) of distortion, detect fundamental current signal (i by fundamental Current's Detection unit (I) 1s);
B). by compensating fundamental wave electric current generating unit (II) according to the fundamental current signal (i that receives 1s), produce fundamental current (i 1 *), and make fundamental current (i 1 *) from motion tracking fundamental current signal (i 1s);
C). with fundamental current (i 1 *) deliver in pair square winding of series transformer (III);
D). make fundamental current (i 1 *) from the fundamental current (i of motion tracking electrical network bus 1);
E). make first-harmonic main flux Φ in series transformer (III) iron core Ml≈ 0, grid side first-harmonic pressure drop U AX≈ 0, for the nth harmonic impedance Z AX (n)=nZ AX (1)
F). realize that series transformer III stops harmonic wave to scurry into electric power system.
2, a kind of serial active filter system based on fundamental flux compensation is characterized in that, said system is made up of three unit: i.e. fundamental Current's Detection unit, compensating fundamental wave electric current generating unit and series transformer; Its structural relation is:
Electrical network bus (1) is provided with current transformer (2), and the output of current transformer (2) is connected with fundamental Current's Detection link (3), and fundamental Current's Detection unit (I) will detect its fundamental current signal (i from the distortion current (i) of bus 1 *) as output signal; Should detected fundamental current signal (i 1s) carry and be connected to the input of compensating fundamental wave electric current generating unit (II); Compensating fundamental wave electric current generating unit (II) is with the fundamental current (i that is produced 1 *) export pair square winding (ax) that is connected to series transformer (III), its former side's winding (AX) is connected in the electrical network bus.
CN99120103A 1999-12-04 1999-12-04 Serial active filter method and system based on fundamental flux compensation Expired - Fee Related CN1095233C (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100352124C (en) * 2005-05-30 2007-11-28 安徽工业大学 Method for controlling, restraining and eliminating voltage network harmonic of transformer magnetic circuit
CN100355178C (en) * 2003-12-13 2007-12-12 王昆生 Method and apparatus for combined tandem type active fundamental wave electric power reactive compensation and filtering

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1323477C (en) * 2003-04-30 2007-06-27 华中科技大学 High-capacity tandem type active electric power filter
WO2008046309A1 (en) * 2006-10-18 2008-04-24 Zhang Yunyi A method and a device for managing electric network non-power frequency

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100355178C (en) * 2003-12-13 2007-12-12 王昆生 Method and apparatus for combined tandem type active fundamental wave electric power reactive compensation and filtering
CN100352124C (en) * 2005-05-30 2007-11-28 安徽工业大学 Method for controlling, restraining and eliminating voltage network harmonic of transformer magnetic circuit

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