CN105281332A - Hybrid active power filter with high voltage chain-type structure and control method thereof - Google Patents

Abstract

The invention discloses a hybrid active power filter with a high voltage chain-type structure and a control method thereof. The hybrid active power filter comprises chain-type structure converters, filter reactors and high-pass filters, and is characterized in that each chain-type structure converter is a structure converter with a bypass, each chain-type structure converter adopts an H-bridge module, and DC-side capacitors are mutually independent; and the chain-type structure converters are connected with the high-pass filters in parallel through the filter reactors, then connected to a power grid and respectively connected with one phase in the power grid. The control method is based on the filter structure, and comprises harmonic wave frequency division detection, active power filter harmonic closed-loop control, reactive compensation and APF average DC voltage control, and DC voltage balance control. The hybrid active power filter disclosed by the invention has the advantages of simple and compact structure, low cost, good operation reliability, excellent performance and the like.

Description

A kind of hybrid active electric filter of high-voltage chain type structure and control method thereof

Technical field

The present invention is mainly concerned with the electric-power filter field in high-pressure system, refers in particular to a kind of hybrid active electric filter based on high-voltage chain type structure and control method thereof.

Background technology

At present, the Active Power Filter-APF be applied in high-pressure system mainly adopts following three kinds of modes:

One is utilize three phase full bridge current transformer to produce compensation harmonic electric current, by accessing high-voltage fence after transformer boost, the shortcoming of which be three phase full bridge circuit be subject to the blocking voltage restriction of IGBT device cannot direct output HIGH voltage, this causes when Large Copacity application scenario, low-pressure side needs to adopt multiple three phase full bridge circuit in parallel, thus makes low-voltage bus bar electric current very huge.Huge low-tension current not only causes active filter loss to be difficult to control, and the magnetic field that big current causes also can have a negative impact to surrounding devices.Therefore, this kind of not competent Large Copacity application scenario of Active Power Filter-APF.

But along with the various extensive use of power converter technology and the increase of nonlinear-load, the demand of harmonic wave control and capacity are rendered as ascendant trend year by year, the particularly industry such as smelting enterprise, wind-powered electricity generation photovoltaic, so the structure of this Active Power Filter-APF does not utilize extensive use.

Two is the hanging Active Power Filter-APFs of high voltage direct, the Active Power Filter-APF of this form, obtains higher output voltage by series connection unsteady flow module (normally H bridge module).The advantage of which is connected by multiple converter module, CPS-PWM modulation system can be adopted, the resultant voltage exported is made to have higher equivalent switching frequency, although which improves equivalent switching frequency, but still there is the limited problem of the harmonic number of compensation in which, this is more and more extensive in industrial circle application due to various high-low pressure AC and DC hybrid transmission system and hf rectifier, make the Electric Network Higher Harmonic problem being positioned at load center more and more serious, these high order harmonic components invade other circuit can cause serious harm, therefore the Active Power Filter-APF of this form also has its limitation.

Three is hybrid active electric filters, and this kind of Active Power Filter-APF is divided into again two kinds:

One is based on three-phase bridge converter and boosting injected mixed active power filter, although decrease the capacity of active part, owing to adopting injection circuit, current transformer is connected with passive filter.First be serially connected in because current transformer and single tuned filter are cascaded, single tuned filter has higher impedance for high order harmonic component, therefore for high order harmonic component, the limitation of high harmonics ability particularly close to converter switches frequency is weak; Secondly, owing to being connected on single tuned filter, current transformer itself also has output filter simultaneously, the controls transfer spy of current transformer is made newly to become very complicated, although carried out a lot of research to the control of pouring-in compound filter both at home and abroad, but its control stability still has much room for improvement, be easily subject to the impact of filter manufacture level and tuned frequency accuracy; 3rd, although injected mixed active filter can reduce active part capacity greatly, but the minimizing of active part capacity, this type hybrid active electric filter is made to be equivalent to a stable capacitive reactive power source, only there is harmonic wave, or load is idle does not fluctuate larger occasion, still needs dynamic reactive compensation device to be mated.

Another kind is the injection active power filter adopting H bridge chain structure, and this kind adopts chain structure Multilevel Inverters to connect as feature with passive single tuned filter.Although improve the capacity of injected mixed active power filtering, but also there is shortcoming, although active filter is in parallel with passive filter add harmonic ability, owing to not adopting frequency division compensation way, be easy to make active filter and passive filter generation resonance.Although injection type hybrid active filter proposes the Detection Methods with Separate Frequency based on nth harmonic dq coordinate system, but the method mainly adopts low-pass filtering to carry out filtering, harmonic wave after low pass filter filtering accounts for fundamental component, and phase delay is difficult to better compensation, detects real-time general; Although being also designed in some pouring-in compound filter adopts the methods such as neural net to carry out the method for harmonic wave frequency dividing control simultaneously, but due to the harmonic wave superimposing compensation signal detected, this carries out frequency dividing control again, not only adds amount of calculation, also there is mutual interference problem simultaneously.

Summary of the invention

The technical problem to be solved in the present invention is just: the technical problem existed for prior art, the invention provides a kind of simple and compact for structure, with low cost, functional reliability is good, the hybrid active electric filter based on high-voltage chain type structure of superior performance and control method thereof.

For solving the problems of the technologies described above, the present invention by the following technical solutions:

A hybrid active electric filter for high-voltage chain type structure, comprises chain structure current transformer, filter reactor and high pass filter; Described chain structure current transformer is the structure current transformer with bypass, and described chain structure current transformer adopts H bridge module, and each DC bus capacitor is separate; Described chain structure current transformer is in parallel with high pass filter by filter reactor, and then accesses electrical network, is connected mutually respectively with one in electrical network.

As a further improvement on the present invention: described high pass filter is bivalent high-pass filter, after the filter inductance in described high pass filter is in parallel with absorption resistance, then connects with filter capacitor.

The present invention also provides a kind of hybrid active electric filter of high-voltage chain type structure, comprises chain structure current transformer, step-up transformer and high pass filter; Described chain structure current transformer adopts H bridge module, and each DC bus capacitor is separate; Described chain structure current transformer is in parallel with high pass filter by step-up transformer, and then accesses electrical network.

As a further improvement on the present invention: described high pass filter is bivalent high-pass filter, after the filter inductance in described high pass filter is in parallel with absorption resistance, then connects with filter capacitor.

As a further improvement on the present invention: described chain structure current transformer (2) is for having the structure current transformer of bypass.

The present invention also provides a kind of control method based on above-mentioned hybrid active electric filter further, and comprise harmonic wave frequency division and detect, the step that harmonic wave frequency division detects is:

(1.1) system side electric current I is first got _a, I _b, I _c, utilize formula (1), when then using for jth subharmonic, transformation matrix is C _j, j subharmonic can be transformed in j dq coordinate system, be now i lower than j time and above harmonic amplitude _djbe i with phase place _qj;

$C_n=\sqrt{\frac{2}{2}}\left[\begin{array}{ccc}\sin \left(\mathrm{n\ωt}\right)& \sin (\mathrm{n\ωt}-\frac{2\mathrm{\π}}{3})& \sin (\mathrm{n\ωt}+\frac{2\mathrm{\π}}{3})\\ \cos \left(\mathrm{n\ωt}\right)& \cos (\mathrm{n\ωt}-\frac{2\mathrm{\π}}{3})& \cos \left(\mathrm{n\ωt}\frac{2\mathrm{\π}}{3}\right)\end{array}\right]---\left(1\right)$

(1.2) by i _djby high-pass filtering, the alternating current component after filtering also obtains the d axis AC component of the more high order than j time by phase compensation again will with i _djobtain the d axle direct current signal of jth subharmonic under j dq coordinate system more afterwards it is the mapping of j subharmonic amplitude information in j dq coordinate system; By i _qjthe q axis AC component of the more high order than j time is obtained by phase compensation through the filtered alternating current component of high-pass filtering again will with obtain jth subharmonic q axle DC component signal under j dq coordinate system after iqj it is the mapping of j subharmonic phase information in j dq coordinate system.

The present invention also provides a kind of control method based on above-mentioned hybrid active electric filter further, comprises APF harmonic closed-loop control, and the step of APF harmonic closed-loop control is:

(2.1) utilize following formula (2), then transformation matrix is used for j subharmonic frequency division is detected the jth subharmonic d axle DC component obtained with q axle DC component by j transformation matrix after through the pi regulator PI as shown in the formula the jth subharmonic shown in (3) _j, obtain the voltage u needing to export required for absorption jth primary current under abc coordinate system _hj;

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

${\mathrm{PI}}_j={\mathrm{Kp}}_j+\frac{{\mathrm{Ki}}_j}{s}---\left(3\right)$

Wherein: Kp _jfor jth subharmonic proportionality coefficient, Ki _jjth subharmonic integral coefficient;

(2.2) by u _hj, u _hj+ ₁u _hnwith system voltage reference value u _srcascade is subtracted each other, hybrid active filter output voltage reference signal u _hr.

The present invention also provides a kind of control method based on above-mentioned hybrid active electric filter further, comprises reactive power compensation and APF mean direct voltage controls, and the step that reactive power compensation and APF mean direct voltage control is:

(3.1) detect the DC capacitor voltage of each phase converter module of three-phase high-voltage chain structure current transformer respectively, wherein in formula (4), N is the serial number of chain structure current transformer, u _{adc_i}for the direct voltage of A phase i-th chain link module, u _{bdc_i}for the direct voltage of B phase i-th chain link module, u _{cdc_i}for the direct voltage of C phase i-th chain link module, u _{dc_av}for the module average voltage of wherein three-phase phase current transformer, u _rthe voltage control signal of module at different levels can be obtained by CPS-PWM modulation;

$u_{\mathrm{dc}\_\mathrm{av}}=(\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{u}_{\mathrm{Adc}\_i}+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{u}_{\mathrm{Bdc}\_i}+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{u}_{\mathrm{Cdc}\_i})/3N---\left(4\right)$

(3.2) by mean direct voltage value of feedback u _{dc_av}with the DC voltage value u expected _dcrcompare, obtain the d component u of current transformer output voltage through PI controller _cd, by the fundamental reactive component i of the output current of chain type active filter under dq coordinate system _qfbwith benchmark reactive current component i _qrcompare, obtain the q component u of current transformer output voltage through PI controller _cq, more idle and real power control command voltage u under abc coordinate system can being obtained by current indirect control _pq;

(3.3) by idle and real power control command voltage u _pqwith harmonic absorption command voltage u _hrsuperposition, so obtain the three-phase modulations voltage command signal u under abc coordinate _r.

The present invention also provides a kind of control method based on above-mentioned hybrid active electric filter further, comprises voltage balance control, and the step of voltage balance control is:

(4.1) by i-th of ABC three-phase converter module direct voltage feedback signal U _{adc_i}, U _{bdc_i}, U _{cdc_i}respectively with three-phase chain type current transformer mean direct voltage U _{dc_av}subtract each other, by error amount respectively with ABC three-phase output feedack current i _oA, i _oB, i _oCbe multiplied and obtain each phase i-th module modulation voltage increment U after pi regulator _{Δ Ai}, U _{Δ Bi}, U _{Δ Ci};

(4.2) each phase voltage modulation fiducial value U _ar, U _br, U _cr, with each phase i-th module modulation voltage increment U _{Δ Ai}, U _{Δ Bi}, U _{Δ Ci}addition obtains, the final modulation signal U of i-th module of each phase _ari, U _bri, U _cri.

Compared with prior art, the invention has the advantages that:

1, hybrid active electric filter of the present invention is the Parallel Hybrid Active Power Filter formed based on Multilevel Inverters and the passive high three-way filter of chain structure.The present invention utilizes frequency division to detect and compensates specific subharmonic, by chain type many level active power filters filtering low-order harmonic (within 13 times), takes into account dynamic reactive power compensation simultaneously; Passive high three-way filter then filtering high order harmonic component (as more than 13 times), takes into account providing unit point capacitive reactive power compensation simultaneously.The many level block of chain type improve current transformer output voltage, improve current transformer output capacity, adopt phase-shifting carrier wave PWM technology simultaneously, can not need the actual switch frequency increasing the full control devices such as IGBT when significantly improving equivalent switching frequency, improve the fan-out capability of higher harmonic current and the response speed of device.

2, hybrid active electric filter of the present invention, adopts passive high-pass filtering filtering high order harmonic component, adopts the many level of chain type as active part current transformer, active part filtering intermediate frequency and low-frequency harmonics; Further provide corresponding control method simultaneously, make current transformer can carry out specific subharmonic compensation for demand, suppress because high pass filter introduces low-order harmonic scale-up problem in generation, make current transformer not only can with high pass filter parallel running, also can easily form filtering system with single tuning low-pass filtering simultaneously, if current transformer while compensation harmonic, have a spare capacity can carry out reactive power compensation.

Accompanying drawing explanation

Fig. 1 is the principle schematic of the present invention in embody rule example 1.

Fig. 2 is the principle schematic of the present invention in embody rule example 2.

Fig. 3 is the principle schematic of the present invention in embody rule example 3.

Fig. 4 is the principle schematic of getting system side electric current in control method of the present invention when carrying out harmonic wave frequency division and detecting.

Fig. 5 is in the principle schematic of carrying out harmonic amplitude detection in control method of the present invention.

Fig. 6 is in the principle schematic of carrying out harmonic phase detection in control method of the present invention.

Fig. 7 is in the principle schematic of carrying out harmonic wave frequency dividing control process in control method of the present invention.

Fig. 8 is the principle schematic in control method of the present invention when carrying out reactive power compensation and APF mean direct voltage controls.

Fig. 9 is carrying out voltage balance control and is obtaining the schematic diagram of each phase i-th module modulation voltage increment in control method of the present invention.

Figure 10 is carrying out voltage balance control and is obtaining the schematic diagram of final modulation signal in control method of the present invention.

Marginal data:

1, filter reactor; 2, chain structure current transformer; 3, high pass filter; 4, step-up transformer.

Embodiment

Below with reference to Figure of description and specific embodiment, the present invention is described in further details.

Embodiment 1: as shown in Figure 1, hybrid active electric filter for high-voltage chain type structure of the present invention is applied particularly to electrical schematic diagram during direct screening chain structure, and this hybrid active electric filter comprises chain structure current transformer 2, filter reactor 1 and high pass filter 3; Wherein, chain structure current transformer 2 adopts H bridge module, and each DC bus capacitor is separate; Chain structure current transformer 2 is in parallel with high pass filter 3 by filter reactor 1, and then accesses electrical network, and be connected with one in electrical network (A/B/C three-phase) respectively.

In this example, high pass filter 3 can adopt bivalent high-pass filter according to actual needs, after in parallel with absorption resistance by filter inductance, then connects with filter capacitor.

In said structure of the present invention, active converter have employed chain structure, and its output voltage is unrestricted in theory, can connect as required, direct screening can access electrical network, can also improve system response time, improve equivalent switching frequency.The many level active power filters of chain type adopt frequency division to detect, it is little that harmonic amplitude under n-th dq coordinate system after high pass filter 3 and the phase place of phase signal prolong difference, unified phase compensation mode conveniently can be adopted to realize delay reduce, improve the accuracy that frequency division detects.The many level active power filters of chain type and high pass filter 3 parallel running, due to the problem adopting frequency dividing control can solve high pass filter 3 pairs of low-order harmonics amplifications, after Active Power Filter-APF filtering, in system, low-order harmonic content reduces greatly.Can compensate reactive power when harmonic compensation ability is more than needed, the stability of further raising system.High pass filter 3 can keep good harmonic absorption ability by whole high band, is also the characteristic harmonics of current transformer filtering switching frequency, reduces the high order harmonic component injecting electrical network.

Embodiment 2: as shown in Figure 2, hybrid active electric filter for high-voltage chain type structure of the present invention is applied particularly to electrical schematic diagram during boosting chain structure, and this hybrid active electric filter comprises chain structure current transformer 2, step-up transformer 4 and high pass filter 3; Wherein, chain structure current transformer 2 adopts H bridge module, and each DC bus capacitor is separate; Chain structure current transformer 2 is in parallel with high pass filter 3 by step-up transformer 4, and then accesses electrical network.

In this example, high pass filter 3 can adopt bivalent high-pass filter according to actual needs, after in parallel with absorption resistance by filter inductance, then connects with filter capacitor.

Embodiment 3: as shown in Figure 3, hybrid active electric filter for high-voltage chain type structure of the present invention is applied particularly to electrical schematic diagram during boosting chain structure, and this hybrid active electric filter comprises chain structure current transformer 2, step-up transformer 4 and high pass filter 3; Wherein, chain structure current transformer 2 adopts H bridge module, and each DC bus capacitor is separate; Chain structure current transformer 2 is in parallel with high pass filter 3 by step-up transformer 4, and then accesses electrical network.Just be with the difference of embodiment 2: unbypassed design in chain structure current transformer 2.

In this example, high pass filter 3 can adopt bivalent high-pass filter according to actual needs, after in parallel with absorption resistance by filter inductance, then connects with filter capacitor.

The present invention further provides a kind of control method of the hybrid active electric filter based on above-mentioned high-voltage chain type structure, the steps include:

(1) harmonic wave frequency division detects;

(1.1) system side electric current I is first got _a, I _b, I _c, as shown in Figure 4, utilize formula (1), when then using for jth subharmonic, transformation matrix is C _j, j subharmonic can be transformed in j dq coordinate system, be now i lower than j time and above harmonic amplitude _djbe i with phase place _qj;

$C_n=\sqrt{\frac{2}{2}}\left[\begin{array}{ccc}\sin \left(\mathrm{n\ωt}\right)& \sin (\mathrm{n\ωt}-\frac{2\mathrm{\π}}{3})& \sin (\mathrm{n\ωt}+\frac{2\mathrm{\π}}{3})\\ \cos \left(\mathrm{n\ωt}\right)& \cos (\mathrm{n\ωt}-\frac{2\mathrm{\π}}{3})& \cos \left(\mathrm{n\ωt}\frac{2\mathrm{\π}}{3}\right)\end{array}\right]---\left(1\right)$

(1.2) by i _djby high-pass filtering, the alternating current component after filtering also obtains the d axis AC component of the more high order than j time by phase compensation again will with i _djobtain the d axle DC component signal of jth subharmonic under j dq coordinate system more afterwards by i _qjthe q axis AC component of the more high order than j time is obtained by phase compensation through the filtered alternating current component of high-pass filtering again will the q axle DC component signal of jth subharmonic under j dq coordinate system is obtained more afterwards with i as shown in Figure 5, j ~ n subharmonic phase-detection as shown in Figure 6 for j ~ nth harmonic amplitude detection flow process.

(2) APF harmonic closed-loop control; Due to collection is system side electric current, and therefore harmonic wave frequency dividing control process of the present invention as shown in Figure 7, can realize closed-loop control.

(2.1) utilize following formula (2), then transformation matrix is used for j subharmonic frequency division is detected the jth subharmonic d axle DC component obtained with q axle DC component by j transformation matrix after through the pi regulator PI as shown in the formula the jth subharmonic shown in (3) _j, obtain the voltage needing to export required for absorption jth primary current under abc coordinate system

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

${\mathrm{PI}}_j={\mathrm{Kp}}_j+\frac{{\mathrm{Ki}}_j}{s}---\left(3\right)$

Wherein: Kp _jfor jth subharmonic proportionality coefficient, Ki _jjth subharmonic integral coefficient;

(2.2) by u _hj, u _hj+ ₁u _hnwith system voltage reference value u _srcascade is subtracted each other, hybrid active filter output voltage reference signal u _hr.

(3) reactive power compensation and APF mean direct voltage control;

(3.1) detect the DC capacitor voltage of each phase converter module of three-phase high-voltage chain structure current transformer respectively, wherein in formula (4), N is the serial number of chain structure current transformer, u _{adc_i}for the direct voltage of A phase i-th chain link module, u _{bdc_i}for the direct voltage of B phase i-th chain link module, u _{cdc_i}for the direct voltage of C phase i-th chain link module, u _{dc_av}for the module average voltage of wherein three-phase phase current transformer, u _rthe voltage control signal of module at different levels can be obtained by CPS-PWM modulation

$u_{\mathrm{dc}\_\mathrm{av}}=(\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{u}_{\mathrm{Adc}\_i}+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{u}_{\mathrm{Bdc}\_i}+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{u}_{\mathrm{Cdc}\_i})/3N---\left(4\right)$

(3.2) as shown in Figure 8, by mean direct voltage value of feedback u _{dc_av}with the DC voltage value u expected _dcrcompare, obtain the d component u of current transformer output voltage through PI controller _cd, by the fundamental reactive component i of the output current of chain type active filter under dq coordinate system _qfbwith benchmark reactive current component i _qrcompare, obtain the q component u of current transformer output voltage through PI controller _cq, more idle and real power control command voltage u under abc coordinate system can being obtained by current indirect control _pq;

(3.3) by idle and real power control command voltage u _pqwith harmonic absorption command voltage u _hrsuperposition, so obtain the three-phase modulations voltage command signal u under abc coordinate _r.

(4) voltage balance control strategy;

(4.1) as shown in Figure 9, by i-th of ABC three-phase converter module direct voltage feedback signal U _{adc_i}, U _{bdc_i}, U _{cdc_i}respectively with three-phase chain type current transformer mean direct voltage U _{dc_av}subtract each other, by error amount respectively with ABC three-phase output feedack current i _oA, i _oB, i _oCbe multiplied and obtain each phase i-th module modulation voltage increment U after pi regulator _{Δ Ai}, U _{Δ Bi}, U _{Δ Ci};

(4.2) as shown in Figure 10, each phase voltage modulation fiducial value U _ar, U _br, U _cr, with each phase i-th module modulation voltage increment U _{Δ Ai}, U _{Δ Bi}, U _{Δ Ci}addition obtains, the final modulation signal U of i-th module of each phase _ari, U _bri, U _cri.

Below be only the preferred embodiment of the present invention, protection scope of the present invention be not only confined to above-described embodiment, all technical schemes belonged under thinking of the present invention all belong to protection scope of the present invention.It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principles of the present invention, should be considered as protection scope of the present invention.

Claims (9)

1. a hybrid active electric filter for high-voltage chain type structure, is characterized in that, comprises chain structure current transformer (2), filter reactor (1) and high pass filter (3); Described chain structure current transformer (2) is for having the structure current transformer of bypass, and described chain structure current transformer (2) adopts H bridge module, and each DC bus capacitor is separate; Described chain structure current transformer (2) is in parallel with high pass filter (3) by filter reactor (1), and then accesses electrical network, is connected mutually respectively with one in electrical network.

2. the hybrid active electric filter of high-voltage chain type structure according to claim 1, it is characterized in that, described high pass filter (3) is bivalent high-pass filter, after filter inductance in described high pass filter (3) is in parallel with absorption resistance, then connect with filter capacitor.

3. a hybrid active electric filter for high-voltage chain type structure, is characterized in that, comprises chain structure current transformer (2), step-up transformer (4) and high pass filter (3); Described chain structure current transformer (2) adopts H bridge module, and each DC bus capacitor is separate; Described chain structure current transformer (2) is in parallel with high pass filter (3) by step-up transformer (4), and then accesses electrical network.

4. the hybrid active electric filter of high-voltage chain type structure according to claim 3, it is characterized in that, described high pass filter (3) is bivalent high-pass filter, after filter inductance in described high pass filter (3) is in parallel with absorption resistance, then connect with filter capacitor.

5. the hybrid active electric filter of high-voltage chain type structure according to claim 3, is characterized in that, described chain structure current transformer (2) is for having the structure current transformer of bypass.

6. based on a control method for any one hybrid active electric filter in the claims 1 ~ 5, it is characterized in that, comprise harmonic wave frequency division and detect, the step that harmonic wave frequency division detects is:

(1.1) system side electric current I is first got _a, I _b, I _c, utilize formula (1), when then using for jth subharmonic, transformation matrix is C _j, j subharmonic can be transformed in j dq coordinate system, be now i lower than j time and above harmonic amplitude _djbe i with phase place _qj;

$C_n=\sqrt{\frac{2}{2}}\left[\begin{array}{ccc}\sin \left(\mathrm{n\ωt}\right)& \sin (\mathrm{n\ωt}-\frac{2\mathrm{\π}}{3})& \sin (\mathrm{n\ωt}+\frac{2\mathrm{\π}}{3})\\ \cos \left(\mathrm{n\ωt}\right)& \cos (\mathrm{n\ωt}-\frac{2\mathrm{\π}}{3})& \cos \left(\mathrm{n\ωt}\frac{2\mathrm{\π}}{3}\right)\end{array}\right]---\left(1\right)$

(1.2) by i _djby high-pass filtering, the alternating current component after filtering also obtains the d axis AC component of the more high order than j time by phase compensation again will the d axle DC component signal of jth subharmonic under j dq coordinate system is obtained more afterwards with idj by i _qjthe q axis AC component of the more high order than j time is obtained by phase compensation through the filtered alternating current component of high-pass filtering again will with i _qjobtain the q axle DC component signal of jth subharmonic under j dq coordinate system more afterwards

7. based on a control method for any one hybrid active electric filter in the claims 1 ~ 5, it is characterized in that, comprise APF harmonic closed-loop control, the step of APF harmonic closed-loop control is:

(2.1) utilize following formula (2), then transformation matrix is used for j subharmonic frequency division is detected the jth subharmonic d axle DC component obtained with q axle DC component by j transformation matrix after through the pi regulator PI as shown in the formula the jth subharmonic shown in (3) _j, obtain the voltage u needing to export required for absorption jth primary current under abc coordinate system _hj;

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

${\mathrm{PI}}_j={\mathrm{Kp}}_j+\frac{{\mathrm{Ki}}_j}{s}---\left(3\right)$

Wherein: Kp _jfor jth subharmonic proportionality coefficient, Ki _jjth subharmonic integral coefficient;

(2.2) by u _hj, u _hj+1u _hnsubtract each other with system voltage reference value usr cascade, hybrid active filter output voltage reference signal u _hr.

8. based on a control method for any one hybrid active electric filter in the claims 1 ~ 5, it is characterized in that, comprise reactive power compensation and APF mean direct voltage controls, the step that reactive power compensation and APF mean direct voltage control is:

(3.1) detect the DC capacitor voltage of each phase converter module of three-phase high-voltage chain structure current transformer respectively, wherein in formula (4), N is the serial number of chain structure current transformer, u _{adc_i}for the direct voltage of A phase i-th chain link module, u _{bdc_i}for the direct voltage of B phase i-th chain link module, u _{cdc_i}for the direct voltage of C phase i-th chain link module, u _{dc_av}for the module average voltage of wherein three-phase phase current transformer, u _rthe voltage control signal of module at different levels can be obtained by CPS-PWM modulation;

$u_{\mathrm{dc}\_\mathrm{av}}=(\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{u}_{\mathrm{Adc}\_i}+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{u}_{\mathrm{Bdc}\_i}+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{u}_{\mathrm{Cdc}\_i})/3N---\left(4\right)$

(3.2) by mean direct voltage value of feedback u _{dc_av}with the DC voltage value u expected _dcrcompare, obtain the d component u of current transformer output voltage through PI controller _cd, by the fundamental reactive component i of the output current of chain type active filter under dq coordinate system _qfbwith benchmark reactive current component i _qrcompare, obtain the q component u of current transformer output voltage through PI controller _cq, more idle and real power control command voltage u under abc coordinate system can being obtained by current indirect control _pq;

(3.3) by idle and real power control command voltage u _pqwith harmonic absorption command voltage u _hrsuperposition, so obtain the three-phase modulations voltage command signal u under abc coordinate _r.

9. based on a control method for any one hybrid active electric filter in the claims 1 ~ 5, it is characterized in that, comprise voltage balance control, the step of voltage balance control is:

(4.1) by i-th of ABC three-phase converter module direct voltage feedback signal U _{adc_i}, U _{bdc_i}, U _{cdc_i}respectively with three-phase chain type current transformer mean direct voltage U _{dc_av}subtract each other, by error amount respectively with ABC three-phase output feedack current i _oA, i _oB, i _oCbe multiplied and obtain each phase i-th module modulation voltage increment U after pi regulator _{Δ Ai}, U _{Δ Bi}, U _{Δ Ci};

(4.2) each phase voltage modulation fiducial value U _ar, U _br, U _cr, with each phase i-th module modulation voltage increment U _{Δ Ai}, U _{Δ Bi}, U _{Δ Ci}addition obtains, the final modulation signal U of i-th module of each phase _ari, U _bri, U _cri.