CN104795822A - Appointed sub-harmonic detection and compensation method with reactive compensation function - Google Patents

Abstract

The invention provides an appointed sub-harmonic detection and compensation method with a reactive compensation function. Any sub-harmonic of harmonic current, generated by load in a power grid, is subjected to separated detection and compensation by abc-dq and dq-abc rotary coordinate conversion matrixes, and does not need to be subjected to calculation and detection respectively under the coordinate conversion of positive and negative sequences. According to the appointed sub-harmonic current detection method, the harmonic can be detected and compensated in a targeted manner and the method has the reactive compensation; the detection method is simpler and clearer. The compensation current can be controlled very well, and the control is easier to control. The system stability and reliability can be enhanced.

Description

The appointment subharmonic having reactive power compensation concurrently detects and compensation method

Technical field

The present invention relates to the one having reactive power compensation concurrently specifies subharmonic to detect and compensation method, belongs to harmonic detecting and harmonic wave control field.

Background technology

Along with the develop rapidly of economy, Technics of Power Electronic Conversion device is widely used at industrial circle, the harmonic pollution of electrical network is made to become more and more serious, Active Power Filter-APF (active power filter, APF) be acknowledged as a kind of novel electric power electric device of dynamic suppression harmonic pollution in electric power net, it can all the harmonic current of real-time change and reactive current carry out dynamic compensation to amplitude and frequency.

In order to compensate harmonic current very well, the detection of inevitable requirement harmonic current has rapidity and accuracy simultaneously, namely real-time and the good harmonic detecting technique of dynamic property are the important prerequisites that Active Power Filter-APF efficiently works, therefore harmonic detecting method and Current Control Technology are Active Power Filter-APFs realizes the main link of of commercial Application, become the study hotspot of Active Power Filter-APF.

Current existing harmonic detecting technique is mainly based on the synchronous rotating angle technology under instantaneous power theory.This technical basis exist in three-phase balanced system at 6k ± 1 subharmonic.6k+1 subharmonic is defined as positive sequence harmonic amount, and 6k-1 subharmonic is defined as Negative sequence harmonic component, and proposes positive sequence abc-dq, dq-abc transformation matrix and negative phase-sequence dq-abc, dq-abc transformation matrix thus respectively, so namely adds algorithm complexity.

Summary of the invention

For above-mentioned prior art Problems existing, one provided by the invention specifies subharmonic detection method, carry out separation by means of only any subharmonic of abc-dq, dq-abc rotating coordinate transformation matrix to the harmonic current that load in electrical network produces to detect and compensate, and carry out computing detection under not needing the coordinate transform respectively under positive and negative sequence.

The object of the invention is by following means realize.

The appointment subharmonic having reactive power compensation concurrently detects and compensation method, carries out separation and detects and compensate, comprise following treatment step to any subharmonic of the harmonic current that load in electrical network produces:

1) three-phase phase-locked loop locks voltage fundamental phase place and frequency, is obtained fixed phase and the frequency of the n-th subharmonic by n frequency-doubling method;

2) with 1) phase place of the n-th subharmonic that obtains and frequency be for carrying out Harmonic currents detection and Detecting Reactive Current with reference to distortion load current;

3) with above 1) and 2) process carries out Harmonic currents detection and Detecting Reactive Current to converter output current;

4) utilize 2), 3) harmonic current that obtains, based on the general principle of instantaneous power, carry out pq uneoupled control, obtain required compensation harmonic current component, through low-pass filtering, proportional integral regulates, and harmonic current components and referenced reactive current are transformed to voltage space between current hollow;

5) by 4) inverse transformation of voltage instruction under n frequency multiplication of gained, obtain requiredly compensating nth harmonic and idle voltage instruction, by SVPWM method, obtain the control signal of converter.

Described step 2) coordinate transform that distortion load current carries out under n frequency multiplication, its transformation matrix of coordinates is:

$P_n=\frac{2}{3}\left[\begin{array}{ccc}\cos n\left(\mathrm{\ωt}\right)& \cos n(\mathrm{\ωt}-2\mathrm{\π}/3)& \cos n(\mathrm{\ωt}+2\mathrm{\π}/3)\\ -\sin n\left(\mathrm{\ωt}\right)& -\sin n(\mathrm{\ωt}-2\mathrm{\π}/3)& -\sin n(\mathrm{\ωt}+2\mathrm{\π}/3)\end{array}\right]---\left(2\right)$

Appointment subharmonic current detection method provided by the invention can detect harmonic wave targetedly and compensate; Detection method is simpler, more than you know.And can control preferably offset current, implement and be easier to.And the stability of a system and reliability can be strengthened.

Compared with prior art, remarkable gain effect of the present invention is:

1, can detect harmonic wave targetedly and compensate and can compensating reactive power be had concurrently;

2, detection method is simpler;

3, can control preferably offset current, implement and be easier to;

4, the stability of a system and reliability can be strengthened.

Accompanying drawing explanation

Fig. 1 is the system block diagram that the present invention uses.

Fig. 2 is the algorithm block diagram that decoupled active and reactive controls and harmonic detecting controls.

Fig. 3 is the simulating, verifying figure of this algorithm, and wherein a figure is load current waveform, and b figure is 5 subharmonic detection limits of load, and c figure is the current waveform after only compensating 5 subharmonic, and d figure is the current waveform according to compensating after 5,7,11,13,17 subharmonic simultaneously.

Embodiment

In Fig. 1, Vs is mains side line voltage, and R+jX is line impedance, U _abcand I _abcload-side three-phase net pressure and three-phase current respectively; Main circuit comprises cascaded inverter and DC bus capacitor C, U _dcthe voltage on DC bus capacitor; Control system comprises phase-locked loop part, harmonic wave is idle test section and idle meritorious uneoupled control, harmonic detecting control section, I _cit is rectifier side offset current;

Fig. 2 comprises idle with DC voltage control module, harmonic detecting compensating module and modulation module; Idle with i in DC voltage control module _cabcrectifier side three-phase offset current, i _labcbe threephase load electric current, w is electrical network fundamental frequency, and P represents rotating coordinate transformation, i _refdthe current reference value controlling rectifier DC side voltage stabilization, i _cdand i _cqd-axis d component and the quadrature axis q component that rectifier side offset current represents offset current fundametal compoment after rotating coordinate transformation and low-pass filtering, in like manner, i _lqrepresent the quadrature axis q component of load current fundametal compoment, V _dand V _qrepresent the direct-axis voltage component of rectifier side first-harmonic net pressure after rotating coordinate transformation and quadrature-axis voltage component respectively, U _dbe the direct-axis voltage component of mains side first-harmonic net pressure after rotating coordinate transformation, P-1 is to V _dand V _qcarry out rotational coordinates inverse transformation, generate only containing the rectifier side three-phase net pressure of first-harmonic, V _5abc, V _7abc, V _11abc, V _nabcrepresent 5 times, 7 times, 11 times, n time rectifier side three-phase net pressure respectively; In like manner, i in harmonic detecting compensating module _5prand i _5qrrepresent direct axis component and the quadrature axis component of load current 5 component of degree n n respectively, i _5pand i _5qrepresent direct axis component and the quadrature axis component of offset current 5 component of degree n n, V _5pand V _5qrepresent 5 direct axis components that rectifier side 5 secondary net presses component after rotating coordinate transformation and quadrature axis component.

Embodiment

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described.

Step one: three-phase phase-locked loop locks voltage fundamental phase place and frequency, obtains frequency and the phase place of three-phase voltage, is obtained fixed phase and the frequency of the n-th subharmonic by n frequency-doubling method;

Step 2: with the phase place of the n-th subharmonic of step one gained and frequency for reference, to distortion load current i _labccarry out the rotating coordinate transformation under n frequency multiplication, its transformation matrix of coordinates is

$P_n=\frac{2}{3}\left[\begin{array}{ccc}\cos n\left(\mathrm{\ωt}\right)& \cos n(\mathrm{\ωt}-2\mathrm{\π}/3)& \cos n(\mathrm{\ωt}+2\mathrm{\π}/3)\\ -\sin n\left(\mathrm{\ωt}\right)& -\sin n(\mathrm{\ωt}-2\mathrm{\π}/3)& -\sin n(\mathrm{\ωt}+2\mathrm{\π}/3)\end{array}\right]---\left(3\right)$

If establish the n-th subharmonic current component

$i_{\mathrm{Lnabc}}=\left(\begin{array}{c}{i}_{\mathrm{Lna}}\\ i_{\mathrm{Lnb}}\\ i_{\mathrm{Lnc}}\end{array}\right)=i_{\max }\left(\begin{array}{c}\cos \mathrm{nwt}\\ \cos (\mathrm{nwt}-\frac{2}{3}\mathrm{\π})\\ \cos (\mathrm{nwt}+\frac{2}{3}\mathrm{\π})\end{array}\right)---\left(4\right)$

I _maxbe the amplitude of nth harmonic electric current, w is electrical network fundamental voltage, then through rotating coordinate transformation, and i _ndq=P _ni _nabc, the amount of gained, through low-pass filtering, obtains required compensation nth harmonic reference current DC component i _npr, i _nqr,

$i_{\mathrm{ndq}}=P_n\·i_{\mathrm{nabc}}=\left(\begin{array}{c}{i}_{\mathrm{npr}}\\ i_{\mathrm{nqr}}\end{array}\right)---\left(5\right)$

Step 3: in like manner can obtain the p component i in offset current _npwith q component i _nq;

Step 4: utilize the rotation relationship of current component and component of voltage and the general principle of pq decoupling zero, instruction is transformed to voltage space between current hollow is foundation based on following Mathematical Modeling by instruction map between current hollow to voltage space instruction:

$V_{\mathrm{dq}}=\left(\begin{array}{c}{V}_d\\ V_q\end{array}\right)=\left(\begin{array}{c}-L\frac{{\mathrm{di}}_d}{\mathrm{dt}}+\mathrm{wL}{i}_q-{\mathrm{Ri}}_d+u_d\\ -L\frac{{\mathrm{di}}_d}{\mathrm{dt}}-w{\mathrm{Li}}_d-{\mathrm{Ri}}_q+u_q\end{array}\right)---\left(6\right)$

Wherein L is the support inductance of main circuit of converter, and w is electrical network fundamental frequency, V _d, V _qthe harmonic wave or the reactive power compensation instruction that transform to voltage space;

Step 5: the inverse transformation under n frequency multiplication, is compensated the voltage instruction V of the n-th subharmonic _nabc, wherein inverse-transform matrix is

${P^{-1}}_n=\left[\begin{array}{cc}\cos \mathrm{n\ωt}& -\sin \mathrm{n\ωt}\\ \cos n(\mathrm{\ωt}-2\mathrm{\π}/3)& -\sin n(\mathrm{\ωt}-2\mathrm{\π}/3)\\ \cos n(\mathrm{\ωt}+2\mathrm{\π}/3)& -\sin n(\mathrm{\ωt}+2\mathrm{\π}/3)\end{array}\right]---\left(7\right)$

By reference to the accompanying drawings 1 and accompanying drawing 2 can find out the carrying out practically process of this embodiment

A, three-phase phase-locked loop (1) lock voltage fundamental phase place and frequency, are obtained fixed phase and the frequency of the n-th subharmonic by n frequency-doubling method; When carrying out the operation of n frequency multiplication, be the n frequency multiplication operation of total phase angle under sinusoidal quantity fundamental frequency, formed and both can be used for carrying out positive sequence harmonic current detecting, can be used for again the single transformation matrix of coordinates that negative sequence harmonic current detects;

B, the phase place of the n-th subharmonic obtained with (a) and frequency, for reference, carry out Harmonic currents detection (2) and Detecting Reactive Current (3) respectively to distortion load current and converter output current;

C, the harmonic current that (b) is obtained, by pq coordinate transform, obtain the current component of required compensation harmonic under pq coordinate, again after low-pass filtering elimination wherein alternating current component, passing ratio derivative controller (PI) regulates, and harmonic current components and referenced reactive current are transformed to voltage space (4) between current hollow;

D, by the inverse transformation of the voltage instruction of (c) gained under n frequency multiplication, obtain required compensating nth harmonic and idle voltage instruction, by SVPWM method (5), obtain the control signal of converter.

By reference to the accompanying drawings 1, accompanying drawing 2 also can see the detailed process of compensation, and to the detailed process of above-mentioned steps four, details are as follows:

By given for current transformer DC voltage and DC voltage V _dcpassing ratio integral adjustment, obtains DC side current reference value i _refd, by current transformer current i _cabcthrough rotating coordinate transformation and low-pass filtering, obtain its DC component i _cdand i _cq, in like manner by load current through rotating coordinate transformation and low-pass filtering, obtain its idle DC component i _lq, by each component i obtained above _refd, i _cd, i _cqand i _lqregulate through proportional integral, just current-order is transformed to voltage space by between current hollow, obtain DC voltage component V _dwith V _q, then by V _d, V _qby dq inverse transformation, obtain the three-phase alternating voltage signal V controlling DC capacitor voltage balance and compensating reactive power _abc; Harmonic detecting and compensation method as described below:

By current transformer current i _cabcthrough rotating coordinate transformation and low-pass filtering, obtain its DC component i _5pand i _5q, in like manner by load current i _labcthrough rotating coordinate transformation and low-pass filtering, obtain required compensation quintuple harmonics reference current DC component i _5pr, i _5qr; By each component i obtained above _5p, i _5q, i _5prand i _5qrregulate through proportional integral, just current-order is transformed to voltage space by between current hollow, obtain DC voltage component V _5pwith V _5q, then by V _5p, V _5qby dq inverse transformation, be compensated the voltage signal V of quintuple harmonics _5abc; The compensation principle of other subharmonic is same as described above.

Claims (2)

1. the appointment subharmonic having reactive power compensation concurrently detects and compensation method, carries out separation and detects and compensate, comprise following treatment step to any subharmonic of the harmonic current that load in electrical network produces:

1) three-phase phase-locked loop locks voltage fundamental phase place and frequency, is obtained fixed phase and the frequency of the n-th subharmonic by n frequency-doubling method;

2) with 1) phase place of the n-th subharmonic that obtains and frequency be for carrying out Harmonic currents detection and Detecting Reactive Current with reference to distortion load current;

3) with above 1) and 2) process carries out Harmonic currents detection and Detecting Reactive Current to converter output current;

4) utilize 2), 3) harmonic current that obtains, based on the general principle of instantaneous power, carry out pq uneoupled control, obtain required compensation harmonic current component, through low-pass filtering, proportional integral regulates, and harmonic current components and referenced reactive current are transformed to voltage space between current hollow;

5) by 4) inverse transformation of voltage instruction under n frequency multiplication of gained, obtain requiredly compensating nth harmonic and idle voltage instruction, by SVPWM method, obtain the control signal of converter.

2. the appointment subharmonic having reactive power compensation according to claim 1 concurrently detects and compensation method, it is characterized in that, described step 2) coordinate transform that distortion load current carries out under n frequency multiplication, its transformation matrix of coordinates is:

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