CN2762416Y - Large capacity parallel active filter - Google Patents

Abstract

The utility model discloses a large capacity parallel active filter, wherein primary side windings of a transformer are connected to both ends of an electric network in parallel, and harmonic current signals of a primary side is detected by a harmonic current detecting unit; each of secondary windings of which the number is N of the transformer is injected with identical harmonic current, and thus, the waveforms of the harmonic current is identical to those of the harmonic current signals of the primary side; the ratio of compensating harmonic current output by a compensating current generating subunit II' to the harmonic current of the primary side is L1/M by the control of a current signal setter unit V, then the voltage of the harmonic current in the primary windings is reduced to zero and has a low impedance approximate to zero over nth harmonic current, and thus, the majority of the harmonic current passes through the primary side windings without getting into an electric power system. The utility model only detects the harmonic current of the primary side windings of the transformer, and the response is stable; the transformer cores work in the state of harmonic flux approximate to zero, and the working point is in the vicinity of the zero point of a B-H curve and a linearity region, and has good compensating effect; the utility model is applicable to work conditions of high voltage and high capacity.

Description

A kind of big capacity shunt active power filter

Technical field

The utility model belongs to electric harmonic and suppresses technical field, is specifically related to a kind of big capacity shunt active power filter.

Background technology

Increasing along with the fast development of high-voltage large-capacity electrical network, large-capacity power electronics load, more and more urgent to the demand of high-voltage large-capacity active filter.For example the fast development of electric railway (containing subway) has caused the harmonic pollution serious to electrical network; A large amount of iron and steel roll lines drags electric equipment and produces a large amount of electric harmonics; Developing rapidly of aluminium electroloysis industry also causes electric harmonic pollution further to aggravate.

Suppress the main passive filter that adopts at high-voltage large-capacity systematic electricity harmonic wave both at home and abroad at present, its effect is bad, except the harmonic wave that injects electric power system seriously is above standard the restriction, also brings out parallel resonance easily.The foreign scholar tries hard to adopt shunt active power filter to solve the harmonic pollution problem.The domestic and international research achievement is summarized as follows at present:

The first active filter that passive filter and relative capacity is less is connected (active filter is through transformer coupled), and is then that this branch road is in parallel with load.The principle of this scheme is: when normal steady operation, because the pressure drop of capacitor is big, at parallel active filter (Shunt Active Filter abbreviates Shunt AF as) two ends pressure drop U _BXLess, whole system can be under the high pressure operating mode operate as normal.But, may damage the power electronic device of Shunt AF device when device drops into electrical network moment or reclosing moment.But how to solve its this problem abroad and do not see that document mentions.

It two is low pressure side joint parallel active filters at transformer, detect the harmonic wave in the load current, control Shunt AF output harmonic wave electric current is to the transformer low voltage winding, produces proportional harmonic current at the transformer high-voltage winding and removes to offset harmonic current in the load.This transformer work magnetic is close to be higher, because the silicon steel sheet BH curve is non-linear, wave distortion can take place in the harmonic current of high pressure winding, and it also is not so good putting into practice just bright this parallel active filter filter effect, and how to solve its jumbo problem and seldom have document to mention.

Summary of the invention

The purpose of this utility model is to overcome above-mentioned weak point, and a kind of big capacity shunt active power filter is provided, and this filter construction is simple, dependable performance, cost are lower, and has better compensation and filter effect, can be applicable to the high-voltage large-capacity operating mode.

A kind of big capacity shunt active power filter that the utility model provides, comprise harmonic current detecting unit, offset current generating unit, transformer, the given unit of current signal, it is characterized in that: the first side winding of transformer is connected in parallel on the electrical network two ends, and the number of turn of winding is w ₁, its secondary side is provided with N winding a _kx _k, k=1,2,3 ... N, N≤500, the number of turn of each winding is w ₂, physical dimension is identical; The harmonic current detecting unit comprises current transformer and the harmonic wave current detecting link that is positioned at the transformer primary side; Current transformer is used to detect the current signal of transformer first side winding, and harmonic current detects the current signal of link received current instrument transformer output, and detects harmonic current signal i wherein _1n ^～The offset current generating unit by N identical and with transformer in the offset current generation subelement that links of corresponding secondary winding constitute; One end of the given unit of current signal and harmonic current detect link and link, and the other end and offset current generating unit link.

Above-mentioned offset current generation subelement comprises the Current Control part that links with the given unit of current signal, and the inverter section that links with Circuit Fault on Secondary Transformer.Wherein, the current control division branch comprises feedback current detection part, operational amplifier, pi regulator, comparator and the triangular-wave generator that links successively; Inverter section comprises inverter, the switching frequency filter that links successively, and the current transformer that is used to detect Circuit Fault on Secondary Transformer winding current signal.

The primary side two ends of above-mentioned transformer be parallel with voltage transformer, and with the joining voltage detecting parts of voltage transformer output.

The utlity model has following technical characterstic:

(1) current transformer of extraction harmonic current is connected in the winding of transformer primary side; And the current transformer of prior art is connected in the load bus.

(2) compensatory michanism of the present utility model is to be zero with harmonic current voltage-drop compensation in the winding of transformer primary side, so the transformer first side winding is the Low ESR that is approximately zero to harmonic current; The harmonic current that flows through in the transformer first side winding is ∑ i _1n, be ∑ i at the harmonic current ripple of the injection of each secondary winding of transformer _2n/ N, these two harmonic currents are unshakable in one's determination altogether, directly compensate, and compensation effect is good; And prior art is that the larger capacity transformer is used as current source, sends harmonic current, removes to offset the harmonic wave in the load current, and given electric current and feedback current are unshakable in one's determination altogether, are indirect; The compensation effect variation.

(3) transformer core of the present utility model is operated in approximate zero harmonic flux state, and this working point is near the zero point of B H curve, to be the range of linearity; The pressure drop of transformer primary side leakage reactance is also compensated, and compensation effect is good; And the transformer core of prior art is operated in than the high-magnetodensity state, and the leakage reactance non-linear, transformer of BH curve makes the compensation effect variation.

(4) the utility model is provided with N winding in Circuit Fault on Secondary Transformer, and each winding links with identical offset current generation subelement.Adopt this method to realize the high voltage large capcity shunt active power filter, so simple, reliable, cheap.For example can utilize existing low voltage, less current device (for example 1200V, the IGBT of 200A～500A) realizes high voltage larger capacity (for example 10kV, several thousand kVA) active filter; And prior art generally adopts IGBT connection in series-parallel, many level etc.These methods are all complicated, poor reliability and cost height.

Description of drawings

Fig. 1 is a structural representation of the present utility model;

Fig. 2 is a kind of structural representation of embodiment;

Fig. 3 is the structural representation of the shunt active power filter of band static reacance generator effect;

Fig. 4 is the structural representation of series and parallel hybrid active filter;

Fig. 5 is the structural representation of the series and parallel hybrid active filter of band static reacance generator effect;

Fig. 6 is the structural representation of the big capacity shunt active power filter of band controlled reactor effect.

Embodiment

Below in conjunction with accompanying drawing the utility model is described in further detail.

As shown in Figure 1, the said big capacity shunt active power filter of the utility model mainly is made up of four unit: harmonic current detecting unit I, offset current generating unit II, transformer III, the given unit V of current signal.

Transformer III, its first side winding is connected in parallel on the electrical network two ends, and its secondary side is provided with N winding a _kx _k, k=1,2,3 ... N (N≤500), the number of turn of each winding is w ₂, physical dimension is identical.

Harmonic current detecting unit I is made of current transformer 4 and harmonic wave current detecting link 5.The current transformer 4 that is positioned at transformer III primary side detects the current signal of transformer first side winding; 5 current signals from current transformer 4 outputs of harmonic current detection link detect harmonic current signal i wherein _1n ^～, for example adopt the method for instantaneous reactive power theory just can accomplish.i _1n ^～Be proportional to the harmonic current waveform ∑ i of transformer first side winding _1n

Harmonic current detecting unit I detects the harmonic current signal i of transformer primary side _1n ^～, and with i _1n ^～Be transported among the given unit V of current signal.The given unit V of current signal is according to harmonic current signal i _1n ^～With Circuit Fault on Secondary Transformer number of windings N, output harmonic wave current signal i _1n ^～/ N each subelement II ' in the offset current generating unit II.

Offset current generating unit II is made of N identical offset current generation subelement II '.Each subelement II ' among the offset current generating unit II is according to the harmonic current signal i that receives _1n ^～Harmonic current takes place in/N, again with the harmonic current ∑ i of its generation _2n/ N is injected in the transformer in the corresponding secondary winding (i.e. k subelement II ' _kHarmonic current ∑ i with its generation _2n/ N is injected into k secondary winding a of transformer _kx _kIn, k=1,2,3 ... N), and from motion tracking harmonic current signal i _1n ^～/ N.

Obviously, the harmonic current waveform that is transported to each secondary winding of transformer is identical, is ∑ i _2n/ N, and with the harmonic current waveform ∑ i of a winding of transformer _1nIdentical, the given unit V of current signal controls the harmonic current signal i of its output _1n ^～/ N, the compensation harmonic electric current ∑ i that makes offset current generation subelement II ' output _2n/ N and transformer III primary side harmonic current waveform ∑ i _1nRatio equal L ₁/ M, then the harmonic current pressure drop is zero in winding of transformer.Its reason is summarized as follows:

L ₁·∑i _1n-M ₁∑i _2n/N-M ₂∑i _2n/N-……-M _N∑i _2n/N＝0

Abbreviation is: L ₁∑ i _1n-M ∑ i _2n/ N=0

In the formula: M=∑ M _KK=1,2 ... N

M in the formula _KMutual inductance for a K secondary winding of transformer and a winding; L ₁Be the self-induction of a winding of transformer, L ₁M is constant.

The harmonic current ∑ i of each secondary winding output of transformer _2n/ N and its primary side harmonic current waveform ∑ i _1nProportionate relationship be:

(∑ i _2n/ N)/∑ i _1n=L ₁/ M==constant.

So the harmonic current pressure drop is zero in winding of transformer, the transformer primary side is the Low ESR that is approximately zero to the nth harmonic electric current, and the harmonic current overwhelming majority is circulated in the transformer first side winding, does not scurry into electric power system; The transformer primary side is very big excitation impedance to fundamental current, only flows through less first-harmonic exciting current, and active power filtering in parallel is not made a difference.

The harmonic current that flows through in the transformer first side winding is ∑ i _1n, be ∑ i at the harmonic current ripple of the injection of each secondary winding of transformer _2n/ N, these two harmonic currents are unshakable in one's determination altogether, directly compensate; Transformer core of the present utility model is operated in approximate zero harmonic flux state, and this working point is near the zero point of BH curve, to be the range of linearity, and compensation effect is good.

Fig. 1 is a kind of single-phase big capacity shunt active power filter, the single-phase big capacity shunt active power filter of three covers adopts star connection or delta connection can constitute the big capacity shunt active power filter of three-phase, at this moment three-phase transformer can adopt the three-phase heart type structure, and inverter also can adopt three-phase inverter.

Fig. 2 is an embodiment, and offset current generation subelement II ' comprises Current Control part II ' 1 and inverter section II ' 2.Current Control part II ' 1 adopts the triangular wave manner of comparison, comprises feedback current detection part 7, operational amplifier 8 (for example operational amplifier TL074), PI (being proportional integral) adjuster 12, comparator 9 (for example comparator LM311), triangular-wave generator 10.Inverter section II ' 2 comprises inverter 4, switching frequency filter L _dC _dSummation current transformer TA ₂, TA ₂Be used to detect the current signal of Circuit Fault on Secondary Transformer winding.

Harmonic current detecting unit I is with detected harmonic current signal i _1n ^～Output to the given unit V of current signal, the given unit V of current signal is according to harmonic current signal i _1n ^～Count N with secondary side winding, output harmonic wave current signal i _1n ^～/ N arrives "+" terminal of the operational amplifier 8 among the Current Control part II ' 1; Feedback current detection part 7 is from current transformer TA ₂The current signal i of a winding of receiving transformer secondary side ₂ ^～/ N produces feedback current signal i _1f ^～, i _1f ^～Be output to "-" terminal of operational amplifier 8,8 couples of input signal i of operational amplifier _1n ^～/ N and i _1f ^～Difference amplify and obtain output signal e ₁, and with e ₁Be transported to pi regulator 12, regulate obtaining output signal e by pi regulator 12 _P1, pi regulator 12 is with output signal e _P1Deliver to "+" terminal of comparator 9, the certain triangle wave voltage signal of the amplitude of triangular-wave generator 10 output fixed frequencies (for example be 20kHz) is to "-" terminal of comparator 9, and exporting a series of amplitudes by comparator 9 is+1 (to work as e _P1Greater than the triangle wave voltage part) or 0 (work as e _P1Less than the triangle wave voltage part) the pulse signal of change width, i.e. drive signal i _PWMDrive signal i _PWMDrive the circuits for triggering in the inverter 4, inverter 4 output harmonic wave electric current ∑ i _2n/ N is in a secondary side winding of transformer, and the given unit V of current signal controls the harmonic current signal i of its output _1n ^～/ N makes the compensation harmonic electric current ∑ i of inverter section II ' 2 output of offset current generation subelement _2n/ N and transformer III primary side harmonic current waveform ∑ i _1nRatio equal L ₁/ M, then the harmonic current pressure drop is zero in winding of transformer.Filter L _dC _dThe switching frequency that is used for power device (for example IGBT) when operation of filtering inverter 4.

The utility model can use separately, also can (application for a patent for invention number: 200410060663.9) unite use, constitute the big capacity shunt active power filter of band static reacance generator effect, its structure as shown in Figure 3 with big capacity static reacance generator.So promptly can realize parallel connection type active filtering, can realize reactive power compensation again: when load was capacitive, this reacance generator can absorb lagging reactive power from electrical network; When load was perception, this reacance generator can absorb capacitive reactive power from electrical network, thereby realized dynamic passive compensation.

Below in conjunction with Fig. 3 the big capacity shunt active power filter of band static reacance generator effect is described in further detail.

Voltage detection unit VI comprises the voltage transformer 2 that is positioned at transformer III primary side two ends, and and the joining voltage detecting parts 3 of voltage transformer 2 outputs.When line voltage did not contain harmonic wave, voltage detecting parts 3 can use resistive element, and the voltage at its two ends is detected voltage signal.Voltage detection unit VI detects the voltage signal u at transformer primary side two ends _1s(being fundamental voltage), and with u _1sBe transported to main control unit IV _AIn.

Main control unit IV _AAccording to voltage signal u _1sReactive power S with the absorption of electrical network need the utility model device _Q, output and voltage signal u _1sThe fundamental current signal i that frequency is identical ₁₁To the given unit V of electric current _A

The given unit V of electric current _AAccording to fundamental current signal i ₁₁With by harmonic current detecting unit I _ADetect the harmonic current ∑ i of a winding of transformer _1nSignal i _1n ^～, secondary side winding is counted N, output first-harmonic+harmonic current signal (i ₁₁+ i _1n ^～)/N is to offset current generating unit II.

Each offset current generation subelement II ' among the offset current generating unit II is according to the first-harmonic+harmonic current signal (i that receives ₁₁+ i _1n ^～)/N produces electric current (i ₂₁+ ∑ i _2n)/N, and fundamental current i ₂₁From motion tracking fundamental current signal i ₁₁Harmonic current ∑ i _2nFrom motion tracking harmonic current signal i _1n ^～K subelement II _k' electric current (i of each its generation ₂₁+ ∑ i _2n)/N delivers to k secondary winding a of transformer _kx _kIn, k=1,2,3 ... N.The size of current that each offset current generation subelement II ' is transported to each secondary winding of transformer equates, waveform is identical.

For fundamental current: when ignoring less no-load current, I ₂₁=I ₁(w ₁/ w ₂),

With

Same-phase.

With transformer primary side both end voltage  ₁Be maintained fixed phase relation: when electrical network needs the utility model device to absorb lagging reactive power, control i ₁₁Make

Lag behind 190 ° of  electrical degree (

Also lag behind  ₁90 ° of electrical degrees), when electrical network needs the utility model device to absorb capacitive reactive power, control i ₁₁Make

Be ahead of U ₁90 ° electrical degree (

Also be ahead of  ₁90 ° of electrical degrees).Offset current generation subelement II ' can utilize existing ripe current tracking technology to realize.

The reactive power S that the utility model absorbs from electrical network _Q=U ₁I ₁, when ignoring the less no-load current of transformer primary side, S _Q=U ₁I ₂₁(w ₂/ w ₁).Main control unit IV control static reacance generator makes: when offset current at perceptual reactive current I _21NTo capacitive reactive power electric current-I _21NBetween controllable continuous when changing, its reactive power that absorbs from electrical network is at lagging reactive power U ₁I _1N(≈ U ₁I _21N(w ₂/ w ₁)) to capacitive reactive power-U ₁I _1N≈ (U ₁I _21N(w ₂/ w ₁)) between controllable continuous change, can realize dynamic passive compensation.

For harmonic current, the big capacity shunt active power filter of band static reacance generator effect is identical with the principle and the course of work of filter shown in Figure 1.Also the secondary winding of transformer can be divided into N ₁And N ₂Two groups, to N ₁Individual secondary winding is only injected fundamental current i ₂₁/ N ₁, to N ₂Individual secondary winding is only injected harmonic current ∑ i _2n/ N ₂

The utility model can also and (the application for a patent for invention number: 03119026.X) unite use of big capacity series connection type active electric power filter, can also unite with the parallel connection type passive filter when needing and constitute the series and parallel hybrid active filter, its structure as shown in Figure 4, it can obtain better filter effect.M among the figure: series connection type active electric power filter; P: parallel connection type active electric filter; J: parallel connection type passive filter.

The big capacity parallel connection type active filtering of band static reacance generator effect shown in Figure 3 can also and (the application for a patent for invention number: 03119026.X) unite use of big capacity series connection type active electric power filter, constitute the series and parallel hybrid active filter of band static reacance generator effect, its structure as shown in Figure 5.M among the figure: series connection type active electric power filter; Q: the big capacity parallel connection type active electric filter of band static reacance generator.

The utility model also can and large-capacity controllable reactor (application for a patent for invention number: 03128112.5) unite use, constitute the big capacity shunt active power filter of band controlled reactor effect, as shown in Figure 6, can be used for the capacitive harmonic load, passive filter in parallel can be used as the some of capacitive harmonic load.So promptly parallel connection type active filtering can be realized, the lagging reactive power dynamic compensation can be realized again.

Below in conjunction with Fig. 6 the big capacity shunt active power filter of band controlled reactor effect is described further.

Harmonic current detecting unit I _BBy current transformer 4 and harmonic wave current detecting link 5 _BConstitute.Current transformer 4 detects the current signal of transformer first side winding; Harmonic current detects link 5 _BThen from the current signal of current transformer 4 outputs, detect the fundamental current signal i in winding of transformer ₁₁Harmonious signal wave current i _1n ^～, i ₁₁Be proportional to the fundamental current i in the winding one time ₁i _1n ^～Be proportional to the harmonic current ∑ i in the winding one time _1n, for example adopt the method for instantaneous reactive power theory just can accomplish.

Main control unit IV _BAccording to voltage signal u _1sReactive power S with the absorption of electrical network need the utility model device _QObtain α: $S_Q=U_1^2/(Z_1+(1-\mathrm{\α})Z_m):$ u _1s=u ₁/ k _u, i ₁₁=i ₁/ k ₁, k _uNo-load voltage ratio for the voltage sensor; k ₁No-load voltage ratio for current sensors.

The given unit V of electric current _BAccording to fundamental current signal i ₁₁Harmonious signal wave current i _1n ^～, secondary side winding is counted N, output first-harmonic+harmonic current signal (α i ₁₁+ i _1s ^～)/N is to offset current generating unit II.

Offset current generating unit II is made of the individual identical offset current generation subelement II ' of N (N≤500).Each subelement II ' among the offset current generating unit II is according to first-harmonic+harmonic current signal (the σ i that receives ₁₁+ i _1s ^～)/N produces electric current (α i ₂₁+ ∑ i _2n)/N, and fundamental current i ₂₁From motion tracking fundamental current signal i ₁₁, i ₂₁=k ₁i ₁₁w ₁/ w ₂Harmonic current ∑ i _2nFrom motion tracking harmonic current signal i _1s ^～K subelement II _k' with electric current (the α i of its generation ₂₁+ ∑ i _2n)/N delivers to k secondary winding a of transformer _kx _kIn, k=1,2,3 ... N.The size of current that subelement II ' is transported to each secondary winding of transformer equates, waveform is identical, i ₂₁=i ₁w ₁/ w ₂

For fundamental current:

With

Same-phase, transformer are once surveyed AX two ends equiva lent impedance: Z _AX=Z ₁+ (1-α) Z _m, transformer is once surveyed the lagging reactive power that absorbs from electrical network and is: $S_Q=U_1^2/Z_{\mathrm{AX}},$ Output and voltage signal u _1sThe fundamental current signal that frequency is identical cuts down α i ₁₁To the given unit V of electric current _Bu _1s=u ₁/ k _u, k _uNo-load voltage ratio for voltage transformer; i ₁₁=i ₁/ k ₁, k ₁No-load voltage ratio for current transformer; $S_Q=U_1^2/(Z_1+(1-\mathrm{\α})Z_m),$ Formula is obtained α thus.

For harmonic current, the big capacity shunt active power filter of band controllable reactance effect is identical with the principle and the course of work of filter shown in Figure 1.

Also the secondary winding of transformer can be divided into N ₁And N ₂Two groups, to N ₁Individual secondary winding is only injected fundamental current α i ₂₁/ N ₁, to N ₂Individual secondary winding is only injected harmonic current ∑ i _2n/ N ₂

Persons skilled in the art can adopt multiple concrete mode that the utility model is realized according to above-mentioned disclosed content.

Claims (3)

1, a kind of big capacity shunt active power filter comprises harmonic current detecting unit (I), offset current generating unit (II), transformer (III), the given unit of current signal (V), it is characterized in that:

The first side winding of transformer (III) is connected in parallel on the electrical network two ends, and the number of turn of winding is w ₁, its secondary side is provided with N winding a _kx _k, k=1,2,3 ... N, N≤500, the number of turn of each winding is w ₂, physical dimension is identical;

Harmonic current detecting unit (I) comprises current transformer (4) and the harmonic wave current detecting link (5) that is positioned at transformer (III) primary side; Current transformer (4) is used to detect the current signal of transformer first side winding, and harmonic current detects the current signal of link (5) received current instrument transformer (4) output, and detects harmonic current signal i wherein _Ln ^～

Offset current generating unit (II) by N identical and with transformer (III) in the offset current generation subelement that links of corresponding secondary winding (II ') formation;

One end of the given unit of current signal (V) and harmonic current detect link (5) and link, and the other end and offset current generating unit (II) link.

2, filter according to claim 1, it is characterized in that: described offset current generation subelement (II ') comprises the Current Control part (II ' 1) that links with the given unit of current signal (V), and the inverter section (II ' 2) that links with transformer (III) secondary side;

Current Control part (II ' 1) comprises feedback current detection part (7), operational amplifier (8), pi regulator (12), comparator (9) and the triangular-wave generator (10) that links successively;

Inverter section (II ' 2) comprises inverter (4), the switching frequency filter (L that links successively _dC _d), and the current transformer (TA that is used to detect Circuit Fault on Secondary Transformer winding current signal ₂).

3, filter according to claim 1 and 2 is characterized in that: the primary side two ends of transformer (III) be parallel with voltage transformer (2), and with voltage transformer (2) the joining voltage detecting parts of output (3).

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