CN104184147B - The filtering method of a kind of static synchroballistic device - Google Patents

Abstract

A filtering method for static synchroballistic device, according to the virtual generation electric current I of the actual offset current acquisition current sampling point that SVG in a upper cycle exports_ref(i.e. theoretical sampled value), and according to the sampling undulating quantity X that system can allow under design requirements, obtain the span of sampling point offset current i: | i-I_ref|��X, and accordingly sampling point offset current is filtered. Filtering method of the present invention achieves the prefilter to interfering current under the prerequisite not setting up physical filter part, greatly reduces the application cost of the present invention; Inventive design decision logic cleverly, it is achieved that to the real-time judge of the actual offset current of current sampling point, it is possible to complete rapidly preposition filtering, almost there is not time delay, be that filtering method of the present invention has actual application value; Carry out low-pass filtering again through the preposition filtered electric current signal of the present invention, can greatly improve filter effect.

Description

The filtering method of a kind of static synchroballistic device

The application is application number: 201310172273.X, and the applying date is: 2013-05-10, and name is called: point case application of " a kind of enhanced high-speed low-pass filtering method for static synchroballistic device "

Technical field

The present invention relates to the filtering method of a kind of static synchroballistic device.

Background technology

In recent years in order to administer electric design power quality problem, power department has installed reactive-load compensation device in low-voltage power distribution station area. These reactive-load compensation devices are dynamically thrown based on Capacitor banks and are cut principle, all there is throwing and cut differential. Owing to low pressure distribution network load changes greatly, in underload situation, owing to throwing the existence cutting extreme difference, compensating reactive power vacancy that cannot be correct in a lot of situation.

Static synchroballistic device (STATCOM-StaticSynchronousCompensator, the domestic SVG of being commonly called as) capacitive and lagging reactive power can be in extremely rapid succession provided, realize voltage and Reactive Power Control fast, ensure that power system is stable, efficient, high-quality ground runs, it is widely used in recent years in power system. Low pressure distribution network is directly towards user, it is necessary to ensure as user provides qualified electric power. SVG can more flexibly compensating reactive power vacancy, administer harmonic wave, improve three-phase imbalance, be specially adapted to low-voltage power distribution station area. Compared with traditional reactive-load compensation device, SVG has advantages such as regulating continuously, harmonic wave is little, loss is low, operating range width, reliability height, adjustment speed are fast, since coming out, has just got the attention and degree of flying development.

In addition, along with the paces that intelligent grid is built, China has started the research work of active distribution network. Research shows that active distribution network needs to rely on the flexible alternating current transmission technology of distribution network, use the trend of D-STATCOM flexible allocation distribution network, regulating voltage and idle, support the access of renewable distribution power, micro-capacitance sensor, make distribution network obtain operating performance more economical, efficient.

But, the requirement of equipment used is economic, practical by low pressure distribution network construction, has higher cost performance. In the past owing to not having the little capacity SVG product towards low pressure distribution network, and general SVG product cost is higher, is not suitable for the requirement of low pressure distribution network. Therefore, it is subject to the restriction of price factor at low pressure distribution network SVG equipment, it does not have be widely applied. The low pressure distribution network SVG equipment of development a new generation high performance-price ratio, has become a very urgent task.

For the use of static synchroballistic device, need to use wave filter to be filtered by offset current, use the method that conventional filter adopts, it is to extend time lag as cost to obtain good filter effect, and time delay is crossed conference and is caused current oscillation to increase, it is reflected in current waveform to be exactly the obvious wider width of waveform, reduce the filter effect of strainer, thus low voltage distribution network electric energy quality can be reduced. In order to eliminate above-mentioned interference when calculating momentary power, it is necessary to the wave filter of better effects if.

Summary of the invention

The present invention wants the technical solution problem to be: overcome prior art shortcoming, the filtering method of a kind of static synchroballistic device is proposed, one-level software screening method is increased before low-pass filtering, first filtering manifest error sampling point, then low-pass filtering algorithm is carried out, it is possible to greatly improve filtering speed and filter effect.

In order to solve the problems of the technologies described above, the technical scheme that the present invention proposes is: the filtering method of a kind of static synchroballistic device, comprises the steps:

1st step, the actual offset current of all sampling points obtaining SVG output in a cycle on current sampling point, the actual offset current of y sampling point $I_y^{\′}=\left[\begin{array}{c}{I}_{a,y}^{\′}\\ I_{b,y}^{\′}\\ I_{c,y}^{\′}\end{array}\right],$ Y=1,2 ..., Y, Y are the sampling number of a upper cycle;

2nd step, the actual offset current I ' that the 1st step is obtained_yDo the conversion of three-dimensional static coordinate conversion, three-dimensional rotation coordinate successively, obtain the N subharmonic equivalent transformation electric current under three-dimensional rotation coordinate: $I_{N,y}^{\′\′\′}=\left[\begin{array}{c}{I}_d^{N,y}\\ I_q^{N,y}\\ I_0^{N,y}\end{array}\right],$ In formula, N is the number of times of harmonic wave,Represent the current component of the N subharmonic equivalent transformation electric current under the y actual offset current three-dimensional rotation coordinate on d, q, 0 axle respectively;

3rd step, need the harmonic order M that compensates respectively for system, to current component on q axle of the M subharmonic equivalent transformation electric current of the actual offset current of the upper all sampling points of cycleAverage and take advantage of in sin (2 �� M 50), obtain the wattless component of the M subharmonic of a upper cycle;

4th step, wattless component by described M subharmonic make rotary/static coordinate inverse transformation, three phase static coordinate inverse transformation successively, obtain the M subharmonic offset current reference value of current sampling point $I_{ref}^M=\left[\begin{array}{c}{I}_{aref}^M\\ I_{bref}^M\\ I_{cref}^M\end{array}\right],$ WhereinM subharmonic A, B, C phase offset current reference value being respectively current sampling point, the more virtual generation electric current of acquisition current sampling point that the M subharmonic offset current reference value of current sampling point is added up $I_{ref}=\left[\begin{array}{c}{I}_{aref}\\ I_{bref}\\ I_{cref}\end{array}\right]=\left[\begin{array}{c}{\mathrm{\ΣI}}_{aref}^M\\ {\mathrm{\ΣI}}_{bref}^M\\ {\mathrm{\ΣI}}_{cref}^M\end{array}\right];$

5th step, utilize I_refThe actual offset current of current sampling point is filtered by �� X as threshold, if the actual offset current of current sampling point $i=\left[\begin{array}{c}{i}_a\\ I_b\\ I_c\end{array}\right]$ Meet | i_a-I_aref|��X and | i_b-I_bref|��X and | i_c-I_cref|��X, then send the actual offset current i of current sampling point into next stage low-pass filter and carry out low-pass filtering, otherwise it can be used as interfering current to filter, whereinIn formula, U_dcFor the ME for maintenance of SVG DC capacitor, K is the difference of the upper and lower bridge arm dutycycle of the SVG bridge circuit of a upper cycle; �� is the current waveform angle of rotation corresponding to current sampling point, T is the sampling interval time, L is the inductance value that SVG connects inductance, if certain phase of the actual offset current of current sampling point or heterogeneous cross threshold, the threshold current value of corresponding phase is then utilized to replace interference phase current, complete the correction to interfering current, and the electric current feeding next stage low-pass filter after revising is carried out low-pass filtering, current waveform angle of rotation �� corresponding to current sampling point=z*2 ��/Y, z is the sampling point sequence number of current sampling point place sinusoidal current waveform. .

The filtering method of a kind of static synchroballistic device of the present invention, can not suddenly change based on electric current in inductance, the principle that in electric capacity, voltage can not suddenly change, according to the virtual generation electric current I of the actual offset current acquisition current sampling point that SVG in a upper cycle exports_ref(i.e. theoretical sampled value), then obtains the sampling undulating quantity X that system can allow under design requirements, final basis | i-I_ref|��X draws the span of sampling point offset current i, if the offset current actual value i of current sampling point meets | i-I_ref|��X, then send offset current actual value i into next stage low-pass filter and carry out low-pass filtering, otherwise it can be used as interfering current to filter.

The filtering method of a kind of static synchroballistic device of the present invention, also has following improvement:

1, the y actual offset current acquisition methods that on current sampling point, in a cycle, SVG exports is as follows: sampling constantly with designated frequency, on current sampling point, in a cycle, the three-phase offset current of y sampling point is $I_y=\left[\begin{array}{c}{I}_{a,y}\\ I_{b,y}\\ I_{c,y}\end{array}\right]$ And center line offset current I_n,y; The actual offset current that on current sampling point, in a cycle, SVG exports $I_y^{\′}=\left[\begin{array}{c}{I}_{a,y}^{\′}\\ I_{b,y}^{\′}\\ I_{c,y}^{\′}\end{array}\right]=\left[\begin{array}{c}{I}_{a,y}\\ I_{b,y}\\ I_{c,y}\end{array}\right]-I_{z,y},$ In formula $I_{z,y}=\frac{I_{a,y}+I_{b,y}+I_{c,y}+I_{n,y}}{4}.$

2, the base ripple equivalent transformation electric current under three-dimensional rotation coordinate and each harmonic equivalent transformation electric current acquisition methods are as follows:

First to actual offset current I '_yDo three-dimensional static coordinate conversion, obtain the three-dimensional static coordinate system equivalent transformation electric current of the y actual offset current: $I_y^{\′\′}=\left[\begin{array}{c}{I}_{\mathrm{\α},y}^{\′\′}\\ I_{\mathrm{\β},y}^{\′\′}\\ I_{\mathrm{\γ},y}^{\′\′}\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\\ \frac{1}{\sqrt{2}}& \frac{1}{\sqrt{2}}& \frac{1}{\sqrt{2}}\end{array}\right]\left[\begin{array}{c}{I}_{a,y}^{\′}\\ I_{b,y}^{\′}\\ I_{c,y}^{\′}\end{array}\right],$

I in formula "_��,y��I��_��,y��I��_r,yThe current value component being respectively under the three-dimensional static coordinate system of the y actual offset current equivalent transformation electric current on ��, ��, �� axle;

Again to the three-dimensional static coordinate system equivalent transformation electric current I of described the y actual offset current "_yCarry out the conversion of three-dimensional rotation coordinate, obtain the N subharmonic equivalent transformation electric current under the three-dimensional rotation coordinate of the y actual offset current:

$I_{N,y}^{\′\′\′}=\left[\begin{array}{c}{I}_d^{N,y}\\ I_q^{N,y}\\ I_0^{N,y}\end{array}\right]=\left[\begin{array}{ccc}\cos \left(2\·\mathrm{\π}\·N\·50\right)& \sin \left(2\·\mathrm{\π}\·N\·50\right)& 0\\ -\sin \left(2\·\mathrm{\π}\·N\·50\right)& \cos \left(2\·\mathrm{\π}\·N\·50\right)& 0\\ 0& 0& 1\end{array}\right]\left[\begin{array}{c}{I}_{\mathrm{\α},y}^{\′\′}\\ I_{\mathrm{\β},y}^{\′\′}\\ I_{\mathrm{\γ},y}^{\′\′}\end{array}\right],$

In formula, N is the number of times of harmonic wave,Represent the current component on d, q, 0 axle of N subharmonic equivalent transformation electric current under the three-dimensional rotation coordinate of the y actual offset current respectively.

Filtering method of the present invention achieves the prefilter to interfering current under the prerequisite not setting up physical filter part, greatly reduces the application cost of the present invention; Inventive design decision logic cleverly, it is achieved that to the real-time judge of the actual offset current of current sampling point, it is possible to complete rapidly preposition filtering, almost there is not time delay, be that filtering method of the present invention has actual application value; And the present invention proposes the scheme revised by interfering current, it is ensured that the reliable and stable output of SVG, can not affect because lasting interfering current exists and compensate output; Carry out low-pass filtering again through the preposition filtered electric current signal of the present invention, can greatly improve filter effect, overcome traditional method and rely on raising hardware cost or prolongation time lag to be the defect of cost with boostfiltering effect.

Accompanying drawing explanation

Below in conjunction with accompanying drawing, the present invention is further illustrated.

Fig. 1 is the schema of filtering method embodiment of the present invention

Fig. 2 is the virtual generation electric current of A phase and boundary curve schematic diagram.

Fig. 3-a is current waveform schematic diagram after tradition filtering algorithm SVG compensates.

The filtering method SVG that Fig. 3-b is the embodiment of the present invention compensates rear current waveform schematic diagram.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention will be further described.

As shown in Figure 1, being the filtering method schema of the static synchroballistic device of the embodiment of the present invention, the present embodiment comprises the steps:

1st step, the actual offset current obtaining all sampling points that SVG exports in a cycle on current sampling point, the actual offset current of y sampling point $I_y^{\′}=\left[\begin{array}{c}{I}_{a,y}^{\′}\\ I_{b,y}^{\′}\\ I_{c,y}^{\′}\end{array}\right],$ Y=1,2 ..., Y, Y are the sampling number of a upper cycle; In this example, a cycle sampling point number is 128.

The y actual offset current acquisition methods that in this step, on current sampling point, in a cycle, SVG exports is as follows: sampling constantly with designated frequency, on current sampling point, in a cycle, the three-phase offset current of y sampling point is $I_y=\left[\begin{array}{c}{I}_{a,y}\\ I_{b,y}\\ I_{c,y}\end{array}\right]$ And center line offset current I_n,y; The actual offset current that on current sampling point, in a cycle, SVG exports $I_y^{\′}=\left[\begin{array}{c}{I}_{a,y}^{\′}\\ I_{b,y}^{\′}\\ I_{c,y}^{\′}\end{array}\right]=\left[\begin{array}{c}{I}_{a,y}\\ I_{b,y}\\ I_{c,y}\end{array}\right]-I_{z,y},$ In formula $I_{z,y}=\frac{I_{a,y}+I_{b,y}+I_{c,y}+I_{n,y}}{4}.$

2nd step, the actual offset current I that the 1st step is obtained_y' do the conversion of the conversion of three-dimensional static coordinate, three-dimensional rotation coordinate successively, obtain the N subharmonic equivalent transformation electric current under three-dimensional rotation coordinate: $I_{N,y}^{\′\′\′}=\left[\begin{array}{c}{I}_d^{N,y}\\ I_q^{N,y}\\ I_0^{N,y}\end{array}\right],$ In formula, N is the number of times of harmonic wave,Represent the current component of the N subharmonic equivalent transformation electric current under the y actual offset current three-dimensional rotation coordinate on d, q, 0 axle respectively.

In this step, base ripple equivalent transformation electric current and each harmonic equivalent transformation electric current acquisition methods under three-dimensional rotation coordinate are as follows:

First to actual offset current I '_yDo three-dimensional static coordinate conversion, obtain the three-dimensional static coordinate system equivalent transformation electric current of the y actual offset current:

$I_y^{\′\′}=\left[\begin{array}{c}{I}_{\mathrm{\α},y}^{\′\′}\\ I_{\mathrm{\β},y}^{\′\′}\\ I_{\mathrm{\γ},y}^{\′\′}\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\\ \frac{1}{\sqrt{2}}& \frac{1}{\sqrt{2}}& \frac{1}{\sqrt{2}}\end{array}\right]\left[\begin{array}{c}{I}_{a,y}^{\′}\\ I_{b,y}^{\′}\\ I_{c,y}^{\′}\end{array}\right],$

I in formula "_��,y��I��_��,y��I��_r,yThe current value component being respectively under the three-dimensional static coordinate system of the y actual offset current equivalent transformation electric current on ��, ��, �� axle;

Again to the three-dimensional static coordinate system equivalent transformation electric current I of described the y actual offset current "_yCarry out the conversion of three-dimensional rotation coordinate, obtain the N subharmonic equivalent transformation electric current under the three-dimensional rotation coordinate of the y actual offset current:

$I_{N,y}^{\′\′\′}=\left[\begin{array}{c}{I}_d^{N,y}\\ I_q^{N,y}\\ I_0^{N,y}\end{array}\right]=\left[\begin{array}{ccc}\cos \left(2\·\mathrm{\π}\·N\·50\right)& \sin \left(2\·\mathrm{\π}\·N\·50\right)& 0\\ -\sin \left(2\·\mathrm{\π}\·N\·50\right)& \cos \left(2\·\mathrm{\π}\·N\·50\right)& 0\\ 0& 0& 1\end{array}\right]\left[\begin{array}{c}{I}_{\mathrm{\α},y}^{\′\′}\\ I_{\mathrm{\β},y}^{\′\′}\\ I_{\mathrm{\γ},y}^{\′\′}\end{array}\right],$

In formula, N is the number of times of harmonic wave,Represent the current component on d, q, 0 axle of N subharmonic equivalent transformation electric current under the three-dimensional rotation coordinate of the y actual offset current respectively.

3rd step, need the harmonic order M that compensates respectively for system, to current component on q axle of the M subharmonic equivalent transformation electric current of the actual offset current of the upper all sampling points of cycleAverage and take advantage of in sin (2 �� M 50), obtain the wattless component of the M subharmonic of a upper cycle.

For different equipment, system needs the harmonic order compensated to be not quite similar, and embodiment is for common three phase full bridge controllable silicon Rectified DC load, waveform contains a large amount of harmonic components, but main with 5 times, 7 times, 11 times is for 13 times main, containing a small amount of 17,19 subharmonic, according to this algorithm, emphasis considers 5 times, 7 times, 11 times, 13 order harmonic components. Mainly fundamental wave reactive power content is relatively big for motor load, three-phase four-wire system user then various times harmonic all likely exist. Then may there is the odd harmonic of more than 12 times in 12 pulse three phase rectifying installations. The target compensation of this example is the electric current of silicon controlled rectifier intermediate frequency furnace, then M=1,5,7,11,13. The present embodiment SVG outward current one cycle has 128 sampling points, then there is 128 base ripples (1 subharmonic) idle transient component in a cycle, 128 5 idle transient components of subharmonic, 128 7 idle transient components of subharmonic, 128 11 idle transient components of subharmonic, 128 13 idle transient components of subharmonic. 128 fundamental wave reactive power transient components are averaging and take advantage of in the sine value of corresponding angle of rotation, namely obtain the wattless component of base ripple, the wattless component of all each harmonics needing to compensate can be obtained with reason.

4th step, wattless component by described M subharmonic make rotary/static coordinate inverse transformation, three phase static coordinate inverse transformation successively, obtain the M subharmonic offset current reference value of current sampling point $I_{ref}^M=\left[\begin{array}{c}{I}_{aref}^M\\ I_{bref}^M\\ I_{cref}^M\end{array}\right],$ WhereinM subharmonic A, B, C phase offset current reference value being respectively current sampling point, the more virtual generation electric current of acquisition current sampling point that the M subharmonic offset current reference value of current sampling point is added up $I_{ref}=\left[\begin{array}{c}{I}_{aref}\\ I_{bref}\\ I_{cref}\end{array}\right]=\left[\begin{array}{c}{\mathrm{\ΣI}}_{aref}^M\\ {\mathrm{\ΣI}}_{bref}^M\\ {\mathrm{\ΣI}}_{cref}^M\end{array}\right].$

5th step, utilize I_refThe actual offset current of current sampling point is filtered by �� X as threshold, if the actual offset current of current sampling point $i=\left[\begin{array}{c}{i}_a\\ I_b\\ I_c\end{array}\right]$ Meet | i_a-I_aref|��X and | i_b-I_bref|��X and | i_c-I_cref|��X, then send the actual offset current i of current sampling point into next stage low-pass filter and carry out low-pass filtering, otherwise it can be used as interfering current to filter, whereinIn formula, U_dcFor the ME for maintenance of SVG DC capacitor, K is the difference of the upper and lower bridge arm dutycycle of the SVG bridge circuit of a upper cycle; �� is the current waveform angle of rotation corresponding to current sampling point, and ��=z*2 ��/Y, z are the sampling point sequence number of current sampling point place sinusoidal current waveform, and T is the sampling interval time, and L is the inductance value that SVG connects inductance.

For A phase, as shown in Figure 2, middle curve is the virtual generation electric current I of A phase of current sampling point_aref(i.e. theoretical sampled value) is relative to the function curve of time; Boundary curve of reaching the standard grade is I_aref+ X, the boundary curve that rolls off the production line is I_aref-X, X are the sampling fluctuation maximum value that system can allow under design requirements. Boundary curve will be reached the standard grade and the offset current actual value that rolls off the production line between boundary curve retains, and send into next stage low-pass filter and carry out low-pass filtering; Otherwise it can be used as interfering current to filter; Respectively the offset current actual value of B phase, C phase is filtered in the same way.

In order to better more stable realization is to the compensation of system, interfering current has been revised by the present embodiment, specific practice is: in the 5th step, if certain phase of the actual offset current of current sampling point or heterogeneous cross threshold, the threshold current value of corresponding phase is then utilized to replace interference phase current, complete the correction to interfering current, and the electric current feeding next stage low-pass filter after revising is carried out low-pass filtering. Assume that A phase offset current actual value is greater than I_aref+ X, then the A interfere electric current after revising equals I_aref+ X, if A phase offset current actual value is less than I_aref-X, then the A interfere electric current after revising equals I_aref-X, revises B phase, C interfere electric current in the same way.

The present embodiment is to tradition low-pass filtering and carries out carrying out low-pass filtering after preposition filtering again through the inventive method and has contrasted, and filter effect refers to as shown in Fig. 3-a and Fig. 3-b. As seen from the figure: use conventional filter in order to reach same filter effect, filtering delay-time is excessive, for the algorithm that momentary value Current direct control mode adopts, time delay is crossed conference and is caused current oscillation to increase, the obvious wider width of the waveform in Fig. 3-a can be seen, and after Fig. 3-b display employing filtering method of the present invention, owing to time delay is less, embody current waveform by momentary current algorithm obviously thinner.

In addition to the implementation, the present invention can also have other enforcement modes. All employings are equal to replacement or the technical scheme of equivalent transformation formation, all drop on the protection domain of requirement of the present invention.

Claims (3)

1. a filtering method for static synchroballistic device, comprises the steps:

1st step, the actual offset current of all sampling points obtaining SVG output in a cycle on current sampling point, the actual offset current of y sampling point $I_y^{\′}=\left[\begin{array}{c}{I}_{a,y}^{\′}\\ I_{b,y}^{\′}\\ I_{c,y}^{\′}\end{array}\right],$ Y=1,2 ..., Y, Y are the sampling number of a upper cycle;

2nd step, the actual offset current I ' that the 1st step is obtained_yDo the conversion of three-dimensional static coordinate conversion, three-dimensional rotation coordinate successively, obtain the N subharmonic equivalent transformation electric current under three-dimensional rotation coordinate: $I_{N,y}^{\′\′\′}=\left[\begin{array}{c}{I}_d^{N,y}\\ I_q^{N,y}\\ I_0^{N,y}\end{array}\right],$ In formula, N is the number of times of harmonic wave,Represent the current component of the N subharmonic equivalent transformation electric current under the y actual offset current three-dimensional rotation coordinate on d, q, 0 axle respectively;

3rd step, need the harmonic order M that compensates respectively for system, to current component on q axle of the M subharmonic equivalent transformation electric current of the actual offset current of the upper all sampling points of cycleAverage and take advantage of in sin (2 �� M 50), obtain the wattless component of the M subharmonic of a upper cycle;

4th step, wattless component by described M subharmonic do rotary/static coordinate inverse transformation, three phase static coordinate inverse transformation successively, obtain the M subharmonic offset current reference value of current sampling point $I_{ref}^M=\left[\begin{array}{c}{I}_{aref}^M\\ I_{bref}^M\\ I_{cref}^M\end{array}\right],$ WhereinM subharmonic A, B, C phase offset current reference value being respectively current sampling point, the more virtual generation electric current of acquisition current sampling point that the M subharmonic offset current reference value of current sampling point is added up

$I_{ref}=\left[\begin{array}{c}{I}_{aref}\\ I_{bref}\\ I_{cref}\end{array}\right]=\left[\begin{array}{c}\mathrm{\Σ}{I}_{aref}^M\\ {\mathrm{\ΣI}}_{bref}^M\\ {\mathrm{\ΣI}}_{cref}^M\end{array}\right];$

5th step, utilize I_refThe actual offset current of current sampling point is filtered by �� X as threshold, if the actual offset current of current sampling point $i=\left[\begin{array}{c}{i}_a\\ I_b\\ I_c\end{array}\right]$ Meet | i_a-I_aref|��X and | i_b-I_bref|��X and | i_c-I_cref|��X, then send the actual offset current i of current sampling point into next stage low-pass filter and carry out low-pass filtering, otherwise it can be used as interfering current to filter, whereinIn formula, U_dcFor the ME for maintenance of SVG DC capacitor, K is the difference of the upper and lower bridge arm dutycycle of the SVG bridge circuit of a upper cycle; �� is the current waveform angle of rotation corresponding to current sampling point, T is the sampling interval time, L is the inductance value that SVG connects inductance, if certain phase of the actual offset current of current sampling point or heterogeneous cross threshold, the threshold current value of corresponding phase is then utilized to replace interference phase current, complete the correction to interfering current, and the electric current feeding next stage low-pass filter after revising is carried out low-pass filtering, current waveform angle of rotation �� corresponding to current sampling point=z*2 ��/Y, z is the sampling point sequence number of current sampling point place sinusoidal current waveform.

2. the filtering method of static synchroballistic device according to claim 1, it is characterized in that the y actual offset current acquisition methods that on current sampling point, in a cycle, SVG exports is as follows: sampling in real time with designated frequency, on current sampling point, in a cycle, the three-phase offset current of y sampling point is $I_y=\left[\begin{array}{c}{I}_{a,y}\\ I_{b,y}\\ I_{c,y}\end{array}\right]$ And center line offset current I_n,y; The actual offset current that on current sampling point, in a cycle, SVG exports $I_y^{\′}=\left[\begin{array}{c}{I}_{a,y}^{\′}\\ I_{b,y}^{\′}\\ I_{c,y}^{\′}\end{array}\right]=\left[\begin{array}{c}{I}_{a,y}\\ I_{b,y}\\ I_{c,y}\end{array}\right]-I_{z,y},$ In formula $I_{z,y}=\frac{I_{a,y}+I_{b,y}+I_{c,y}+I_{n,y}}{4}.$

3. the filtering method of static synchroballistic device according to claim 1, it is characterised in that base ripple equivalent transformation electric current and each harmonic equivalent transformation electric current acquisition methods under three-dimensional rotation coordinate are as follows:

First to actual offset current I '_yDo three-dimensional static coordinate conversion, obtain the three-dimensional static coordinate system equivalent transformation electric current of the y actual offset current:

$I_y^{\′\′}=\left[\begin{array}{c}{I}_{\mathrm{\α},y}^{\′\′}\\ I_{\mathrm{\β},y}^{\′\′}\\ I_{\mathrm{\γ},y}^{\′\′}\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\\ \frac{1}{\sqrt{2}}& \frac{1}{\sqrt{2}}& \frac{1}{\sqrt{2}}\end{array}\right]\left[\begin{array}{c}{I}_{a,y}^{\′}\\ I_{b,y}^{\′}\\ I_{c,y}^{\′}\end{array}\right],$

In formulaThe current value component being respectively under the three-dimensional static coordinate system of the y actual offset current equivalent transformation electric current on ��, ��, �� axle;

Again to the three-dimensional static coordinate system equivalent transformation electric current I of described the y actual offset current "_yCarry out the conversion of three-dimensional rotation coordinate, obtain the N subharmonic equivalent transformation electric current under the three-dimensional rotation coordinate of the y actual offset current:

$I_{N,y}^{\′\′\′}=\left[\begin{array}{c}{I}_d^{N,y}\\ I_q^{N,y}\\ I_0^{N,y}\end{array}\right]=\left[\begin{array}{ccc}cos(2\·\mathrm{\π}\·N\·50)& sin(2\·\mathrm{\π}\·N\·50)& 0\\ -sin(2\·\mathrm{\π}\·N\·50)& cos(2\·\mathrm{\π}\·N\·50)& 0\\ 0& 0& 1\end{array}\right]\left[\begin{array}{c}{I}_{\mathrm{\α},y}^{\′\′}\\ I_{\mathrm{\β},y}^{\′\′}\\ I_{\mathrm{\γ},y}^{\′\′}\end{array}\right],$

In formula, N is the number of times of harmonic wave,Represent the current component on d, q, 0 axle of N subharmonic equivalent transformation electric current under the three-dimensional rotation coordinate of the y actual offset current respectively.