CN105356469A - Uniform control method based on harmonic detection and photovoltaic grid-connected instruction synthesis - Google Patents

Abstract

The present invention relates to a kind of unified control method based on harmonic detecting Yu grid-connected instruction synthesis, by being based on Instantaneous power detection method completes harmonic detecting, is used for quickly detecting to three phase harmonic electric current, is calculated by MPPT maximum power point tracking control section With given voltage It handles to obtain grid-connected active command electric current through voltage regulator AVR, unified control system has the function of photovoltaic power generation and active power filtering simultaneously, unified control system work can be made in the working condition of photovoltaic power generation and active power filtering by this algorithm, one device realizes two kinds of functions, improves the utilization rate of system.

Description

A kind of unified control method based on harmonic detecting and grid-connected instruction synthesis

Technical field

The present invention relates to and grid-connectedly unify control field with active power filtering, particularly a kind of unified control method based on harmonic detecting and grid-connected instruction synthesis.

Background technology

Along with the fast development of economy, the demand of the whole world to the energy is increasing, and the total amount of non-renewable energy resources is certain, can be consumed totally one day.Therefore, new forms of energy are developed extremely urgent for a national development.Solar energy source has the factor such as recyclability and environmental protection due to it, is one of following tool new forms of energy with broad prospects for development.Grid-connected technology is ripe, enters the popularization stage.The fields such as along with the fast development of economy, a large amount of power electronic equipments is widely used in industry, agricultural.Due to power electronic equipment itself, the non-linear and time variation of such as power electronic equipment.When power electronic equipment is used, a large amount of harmonic waves and reactive power can be produced.These reactive powers and harmonic wave are influential for the stability of electrical network.For this situation of harmonic pollution, traditional method uses passive filter.But passive filter himself has a lot of shortcomings and limitations, the requirement of the electrical network quality of power supply more and more can not be met.And Active Power Filter-APF recent years has become the focus of domestic and international researcher research.

Photovoltaic power generation apparatus and Active Power Filter-APF respectively have deficiency.First, photovoltaic power generation apparatus is subject to the impact of environmental factor, particularly sunlight.When having sunlight by day, photovoltaic power generation apparatus work; When evening or cloudy day, photovoltaic power generation apparatus be excised electrical network.Therefore, for photovoltaic power generation apparatus, the utilance of himself is not high.Secondly, for Active Power Filter-APF, due to factors such as the single of its function and costs, make to promote difficulty and strengthen.

The theory of constitution of research photovoltaic generating system and Active Power Filter-APF.We can know, the two type provided to electrical network is different.But essentially, the two is then identical.Therefore when not increasing cost, unified control can be realized to both, and makes up deficiency between the two.

The application in photovoltaic generation and active power filtering unified control system based on harmonic detecting and grid-connected instruction synthesis algorithm, make a device can realize photovoltaic generation and active power filtering two kinds of functions this to developing new forms of energy, development green electric power supply has great importance.

Summary of the invention

The object of the present invention is to provide a kind of unified control method based on harmonic detecting and grid-connected instruction synthesis, to overcome the defect existed in prior art.

For achieving the above object, technical scheme of the present invention is: a kind of unified control method based on harmonic detecting and grid-connected instruction synthesis, realizes in accordance with the following steps:

Step S1: add phase-locked loop circuit PLL and function generator generation supply voltage same-phase in circuit diagram, to eliminate the impact of grid voltage waveform sudden change on testing result;

Step S2: note three-phase voltage is respectively V _sa, V _sband V _sc, threephase load electric current is respectively i _la, i _lband i _lc, and three-phase circuit is symmetrical;

Step S3: by described threephase load current i _la, i _lband i _lcby the first Matrix C ₃₂convert, transform on the orthogonal coordinate system of alpha-beta two-phase, export two-phase transient current i _αand i _β;

Step S4: by described two-phase transient current i _αand i _βbe multiplied with the second Matrix C, obtain threephase load electric current active current i _pand threephase load reactive current component i _q;

Step S5: by described threephase load electric current active current i _pwith described threephase load reactive current component i _qcorresponding to low pass filter LPF respectively, obtain the DC component of threephase load electric current active current and the DC component of threephase load electric current reactive current

Step S6: draw P by MPPT maximum power point tracking control section _pV, and measure grid-connected voltage U _dc, with predeterminated voltage U _dc ^*grid-connected meritorious instruction current is obtained through voltage regulator AVR process

Step S7: by the DC component of described threephase load electric current active current with described grid-connected instruction current synthesis, and according to this through described second matrix inversion Matrix C ^-1and described first matrix inversion Matrix C ₂₃, output current i _fa, i _fband i _fc;

Step S8: by described threephase load current i _la, i _lband i _lccorresponding and described current i respectively _fa, i _fband i _fcsubtract each other, obtain i _lha, i _lhb, i _lhc, and i _lha, i _lhb, i _lhcbe respectively idle, the harmonic current of threephase load and the summation of grid-connected meritorious instruction current;

Step S9: by the i obtained _lha, i _lhb, i _lhcby inverter, final offset current instruction is imported electrical network.

In an embodiment of the present invention, in described step S2, described three-phase voltage V _sa, V _sband V _scbe respectively:

$V_{sa}=\sqrt{2}{V}_{1}sin\mathrm{\ω}t$

$V_{sb}=\sqrt{2}{V}_{1}sin(\mathrm{\ω}t-2\mathrm{\π}/3)$

$V_{sc}=\sqrt{2}{V}_{1}sin(\mathrm{\ω}t+2\mathrm{\π}/3)$

Wherein, V ₁be the effective value of supply voltage first-harmonic, ω is angular frequency;

Described threephase load current i _la, i _lband i _lcfor:

$i_{La}=\underset{n=1}{\overset{\mathrm{\∞}}{\Σ}}\sqrt{2}{I}_{n}sin(n\mathrm{\ω}t+{\mathrm{\θ}}_n)$

$i_{Lb}=\underset{n=1}{\overset{\mathrm{\∞}}{\Σ}}\sqrt{2}{I}_n\sin \[n\left(\mathrm{\ω}t-2\mathrm{\π}/3\right)+{\mathrm{\θ}}_n\]$

$i_{Lc}=\underset{n=1}{\overset{\mathrm{\∞}}{\Σ}}\sqrt{2}{I}_{n}sin\[n\left(\mathrm{\ω}t+2\mathrm{\π}/3\right)+{\mathrm{\θ}}_n\]$

Wherein, n=3k ± 1, k is integer, and during k=0, n can only be 1, I _neach primary current effective value, θ _nit is initial phase angle.

In an embodiment of the present invention, in described step S3, described two-phase transient current i _α, i _βcalculate in the following way:

Wherein, described first Matrix C ₃₂for:

$C_{32}=\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right].$

In an embodiment of the present invention, in described step S4, described threephase load electric current active current i _pand described threephase load reactive current component i _qcalculate by following formula:

Wherein, described second Matrix C is:

$C=\left[\begin{array}{cc}sin\mathrm{\ω}t& -cos\mathrm{\ω}t\\ -cos\mathrm{\ω}t& -sin\mathrm{\ω}t\end{array}\right].$

In an embodiment of the present invention, in described step S5, the DC component of described threephase load electric current active current and the DC component of described threephase load electric current reactive current for:

$\left[\begin{array}{c}\stackrel{\‾}{i_p}\\ \stackrel{\‾}{i_q}\end{array}\right]=\sqrt{3}\left[\begin{array}{c}{I}_1\cos (-{\mathrm{\θ}}_n)\\ -I_1\sin \left({\mathrm{\θ}}_n\right)\end{array}\right].$

In an embodiment of the present invention, in described step S6, specifically comprise the following steps:

Step S61: note U is initial value, fixed step size is Δ U, and sample to the magnitude of voltage exported and current value, current sampling data is I, and calculates P;

Step S62: make U ₁=U+ Δ U, samples to current value, and current sampling data is I ₁, and calculate P ₁;

Step S63: make Δ P=P ₁-P, when judging that reference voltage U changes, the situation of change of Δ P; If when reference voltage U becomes large, Δ P > 0, then go to step S64, and Δ P < 0, then go to step S65; If when reference voltage U diminishes, Δ P > 0, then go to step S66, and Δ P < 0, then go to step S67;

Step S64: maximum power point MPP is positioned at the right side of present operating point, the change trend that system should keep reference voltage to become large, makes U ₂=U ₁+ Δ U, U ₂be the magnitude of voltage after second time disturbance, go to step S68;

Step S65: maximum power point MPP is positioned at the left side of present operating point, the change direction that system should keep reference voltage to diminish, U ₂=U ₁-Δ U, U ₂be the magnitude of voltage after second time disturbance, go to step S68;

Step S66: maximum power point MPP is positioned at the left side of present operating point, the change direction that system should keep reference voltage to diminish, U ₂=U ₁-Δ U, U ₂be the magnitude of voltage after second time disturbance, go to step S68;

Step S67: maximum power point MPP is positioned at the right side of present operating point, the change trend that system should keep reference voltage to become large, U ₂=U ₁+ Δ U, U ₂be the magnitude of voltage after second time disturbance, go to step S68;

Step S68: judge whether the power output of solar cell and the difference of maximum power point MPP are ± 1%, if so, then go to step S69, otherwise, go to described step S63; Repeatedly disturbance is carried out to reference voltage in this process, voltage is changed, and make the power output of described solar cell towards becoming large change trend;

Step S69: the output voltage U of to be voltage that maximum power point MPP is corresponding by photovoltaic Output matrix power be photovoltaic matrix, output voltage U obtains described grid-connected voltage U by photovoltaic topological structure _dc.

In an embodiment of the present invention, in described step S7, described output i _fa, i _fband i _fcby following calculating:

$\left[\begin{array}{c}{i}_{fa}\\ i_{fb}\\ i_{fc}\end{array}\right]=C_{23}{C}^{-1}\left[\begin{array}{c}\stackrel{\&OverBar;}{i_p}-\stackrel{\&OverBar;}{i_{pv}}\\ 0\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{c}\sin \mathrm{\&omega;}t\\ \sin \left(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3\right)\\ \sin \left(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3\right)\end{array}\right]\&lsqb;\stackrel{\&OverBar;}{i_p}-\stackrel{\&OverBar;}{i_{pv}}\&rsqb;$

Wherein, $C_{23}=\sqrt{\frac{2}{3}}\left[\begin{array}{cc}1& 0\\ -\frac{1}{2}& \frac{\sqrt{3}}{2}\\ -\frac{1}{2}& -\frac{\sqrt{3}}{2}\end{array}\right],C^{-1}=\left[\begin{array}{cc}sin\mathrm{\&omega;}t& -cos\mathrm{\&omega;}t\\ -cos\mathrm{\&omega;}t& -sin\mathrm{\&omega;}t\end{array}\right],$ C ₂₃, C ^-1be respectively

Described first Matrix C ₃₂and the inverse matrix of described second Matrix C, ω is angular frequency.

In an embodiment of the present invention, in described step S8, i _lha, i _lhband i _lhcby following calculating:

$\left[\begin{array}{c}{i}_{Lha}\\ i_{Lhb}\\ i_{Lhc}\end{array}\right]=\left[\begin{array}{c}{i}_{La}\\ i_{Lb}\\ i_{Lc}\end{array}\right]-\left[\begin{array}{c}{i}_{fa}\\ i_{fb}\\ i_{fc}\end{array}\right]=\left[\begin{array}{c}{i}_{La}\\ i_{Lb}\\ i_{Lc}\end{array}\right]-\sqrt{\frac{2}{3}}\left[\begin{array}{c}\sin \mathrm{\&omega;}t\\ \sin \left(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3\right)\\ \sin \left(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3\right)\end{array}\right]\&lsqb;\stackrel{\&OverBar;}{i_p}-\stackrel{\&OverBar;}{i_{pv}}\&rsqb;=\left[\begin{array}{c}{i}_{La}-\sqrt{\frac{2}{3}}\stackrel{\&OverBar;}{i_p}\sin \mathrm{\&omega;}t\\ i_{Lb}-\sqrt{\frac{2}{3}}\stackrel{\&OverBar;}{i_p}\sin \left(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3\right)\\ i_{Lc}-\sqrt{\frac{2}{3}}\stackrel{\&OverBar;}{i_p}\sin \left(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3\right)\end{array}\right]+\sqrt{\frac{2}{3}}\stackrel{\&OverBar;}{i_{pv}}\left[\begin{array}{c}\sin \mathrm{\&omega;}t\\ \sin \left(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3\right)\\ \sin \left(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3\right)\end{array}\right]$

Wherein, front portion is the harmonics and reactive current component of load electricity, and rear portion is the fundametal compoment of photovoltaic instruction current.

Compared to prior art, the present invention has following beneficial effect: a kind of unified control method based on harmonic detecting and grid-connected instruction synthesis proposed by the invention, by carrying out the synthesis of harmonic detecting and grid-connected instruction to unified control system, carry out active power filtering when unified control system can be made to be operated in photovoltaic generation simultaneously, improve the utilance of system.

Accompanying drawing explanation

Fig. 1 is that the present invention is a kind of based on the circuit theory diagrams in the unified control method of harmonic detecting and grid-connected instruction synthesis.

Fig. 2 is a kind of maximum power tracking method principle flow chart based on adopting in the unified control method of harmonic detecting and grid-connected instruction synthesis of the present invention.

Embodiment

Below in conjunction with accompanying drawing, technical scheme of the present invention is specifically described.

The invention provides a kind of unified control method based on harmonic detecting and grid-connected instruction synthesis, as shown in Figure 1, the method be based on harmonic detecting and grid-connected instruction synthesis algorithm at photovoltaic generation and active power filtering unified control method, comprise the idle of load and harmonic current when K disconnects in testing result; When K closes, algorithm only detects the harmonic current content in load, and synthesizes with grid-connected instruction current, obtains harmonic compensation and the synthetic instruction of the electric current that generates electricity by way of merging two or more grid systems.Below in conjunction with schematic diagram, the situation that K switch disconnects is discussed, specifically comprises the following steps:

Step S1: in order to eliminate the impact of grid voltage waveform sudden change on testing result, adding phase-locked loop circuit PLL sum functions generator and producing supply voltage same-phase in circuit diagram.

Step S2: establish three-phase circuit symmetrical, every voltage is as follows:

$V_{sa}=\sqrt{2}{V}_{1}sin\mathrm{\&omega;}t$

$V_{sb}=\sqrt{2}{V}_{1}sin(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3)$

$V_{sc}=\sqrt{2}{V}_{1}sin(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3)$

In formula, V ₁be the effective value of supply voltage first-harmonic, ω is angular frequency.

Threephase load electric current is:

$i_{La}=\underset{n=1}{\overset{\mathrm{\&infin;}}{\&Sigma;}}\sqrt{2}{I}_{n}sin(n\mathrm{\&omega;}t+{\mathrm{\&theta;}}_n)$

$i_{Lb}=\underset{n=1}{\overset{\mathrm{\&infin;}}{\&Sigma;}}\sqrt{2}{I}_n\sin \&lsqb;n\left(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3\right)+{\mathrm{\&theta;}}_n\&rsqb;$

$i_{Lc}=\underset{n=1}{\overset{\mathrm{\&infin;}}{\&Sigma;}}\sqrt{2}{I}_{n}sin\&lsqb;n\left(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3\right)+{\mathrm{\&theta;}}_n\&rsqb;$

In formula, n=3k ± 1, k is integer, and as k=0, n can only be 1, I _neach primary current effective value, θ _nit is initial phase angle.

Step S3: three-phase current i _la, i _lb, i _lcpass through Matrix C ₃₂conversion, transforms on the orthogonal coordinate system of alpha-beta two-phase, exports as two-phase transient current i _α, i _β.Concrete formula is as follows:

C ₃₂matrix is:

$C_{32}=\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right].$

Step S4:i _α, i _βbe multiplied with Matrix C, obtain threephase load electric current active current i _p, threephase load reactive current component i _q, C is that the synchronous sine of line voltage and cosine signal form transformation matrix, and concrete formula is as follows:

C matrix is:

$C=\left[\begin{array}{cc}sin\mathrm{\&omega;}t& -cos\mathrm{\&omega;}t\\ -cos\mathrm{\&omega;}t& -sin\mathrm{\&omega;}t\end{array}\right]$

Step S5:i _pand i _qafter low pass filter (LPF), obtain with the DC component of threephase load electric current active current, the DC component of threephase load electric current reactive current:

$\left[\begin{array}{c}\stackrel{\&OverBar;}{i_p}\\ \stackrel{\&OverBar;}{i_q}\end{array}\right]=\sqrt{3}\left[\begin{array}{c}{I}_1\cos \left(-{\mathrm{\&theta;}}_n\right)\\ -I_1\sin \left({\mathrm{\&theta;}}_n\right)\end{array}\right]$

Step S6: grid-connected meritorious instruction current draws P by MPPT maximum power point tracking control section _pV, measure U _dc, with given voltage U _dc ^*grid-connected instruction current is obtained through voltage regulator (AVR) process

Step S7: by the DC component of threephase load electric current active current with grid-connected instruction current synthesis, through C ^-1, C ₂₃matrix, exports i _fa, i _fb, i _fc; i _fa, i _fb, i _fccalculate by following formula:

$\left[\begin{array}{c}{i}_{fa}\\ i_{fb}\\ i_{fc}\end{array}\right]=C_{23}{C}^{-1}\left[\begin{array}{c}\stackrel{\&OverBar;}{i_p}-\stackrel{\&OverBar;}{i_{pv}}\\ 0\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{c}\sin \mathrm{\&omega;}t\\ \sin \left(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3\right)\\ \sin \left(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3\right)\end{array}\right]\&lsqb;\stackrel{\&OverBar;}{i_p}-\stackrel{\&OverBar;}{i_{pv}}\&rsqb;$

In formula, $C_{23}=\sqrt{\frac{2}{3}}\left[\begin{array}{cc}1& 0\\ -\frac{1}{2}& \frac{\sqrt{3}}{2}\\ -\frac{1}{2}& -\frac{\sqrt{3}}{2}\end{array}\right],C^{-1}=\left[\begin{array}{cc}sin\mathrm{\&omega;}t& -cos\mathrm{\&omega;}t\\ -cos\mathrm{\&omega;}t& -sin\mathrm{\&omega;}t\end{array}\right].$ C ₂₃, C ^-1be respectively C ₃₂, the inverse matrix of C, ω is angular frequency.

Step S8: by electrical network three-phase current i _la, i _lb, i _lcrespectively with i _fa, i _fb, i _fcsubtract each other, obtain i _lha, i _lhb, i _lhc.I _lba, i _lhb, i _lhcbe respectively the summation of idle, harmonic current, the grid-connected meritorious instruction current of threephase load.Concrete formula is as follows:

$\left[\begin{array}{c}{i}_{Lha}\\ i_{Lhb}\\ i_{Lhc}\end{array}\right]=\left[\begin{array}{c}{i}_{La}\\ i_{Lb}\\ i_{Lc}\end{array}\right]-\left[\begin{array}{c}{i}_{fa}\\ i_{fb}\\ i_{fc}\end{array}\right]=\left[\begin{array}{c}{i}_{La}\\ i_{Lb}\\ i_{Lc}\end{array}\right]-\sqrt{\frac{2}{3}}\left[\begin{array}{c}\sin \mathrm{\&omega;}t\\ \sin \left(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3\right)\\ \sin \left(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3\right)\end{array}\right]\&lsqb;\stackrel{\&OverBar;}{i_p}-\stackrel{\&OverBar;}{i_{pv}}\&rsqb;=\left[\begin{array}{c}{i}_{La}-\sqrt{\frac{2}{3}}\stackrel{\&OverBar;}{i_p}\sin \mathrm{\&omega;}t\\ i_{Lb}-\sqrt{\frac{2}{3}}\stackrel{\&OverBar;}{i_p}\sin \left(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3\right)\\ i_{Lc}-\sqrt{\frac{2}{3}}\stackrel{\&OverBar;}{i_p}\sin \left(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3\right)\end{array}\right]+\sqrt{\frac{2}{3}}\stackrel{\&OverBar;}{i_{pv}}\left[\begin{array}{c}\sin \mathrm{\&omega;}t\\ \sin \left(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3\right)\\ \sin \left(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3\right)\end{array}\right]$

In formula, front portion is the harmonics and reactive current component of load electricity, and rear portion is just in time the fundametal compoment of photovoltaic instruction current.

Step S9: by the i obtained _lha, i _lhb, i _lhcby inverter, final offset current instruction is imported electrical network.

Further, in the present embodiment, what maximal power tracing adopted is voltage disturbance method in disturbance-observer method.Judged the working region of system by the change direction comparing power and voltage, then carry out adjusting accordingly photovoltaic system is operated near maximum power point to reference voltage.Concrete, as shown in Figure 2, adopt in step S6 and comprise the following steps:

Step S61: note U is initial value, fixed step size is Δ U, and sample to the magnitude of voltage exported and current value, current sampling data is I, and calculates P;

Step S62: make U ₁=U+ Δ U, samples to current value, and current sampling data is I ₁, and calculate P ₁;

Step S63: make Δ P=P ₁-P, when judging that reference voltage U changes, the situation of change of Δ P; If when reference voltage U becomes large, Δ P > 0, then go to step S64, and Δ P < 0, then go to step S65; If when reference voltage U diminishes, Δ P > 0, then go to step S66, and Δ P < 0, then go to step S67;

Step S64: maximum power point MPP is positioned at the right side of present operating point, the change trend that system should keep reference voltage to become large, makes U ₂=U ₁+ Δ U, U ₂be the magnitude of voltage after second time disturbance, go to step S68;

Step S65: maximum power point MPP is positioned at the left side of present operating point, the change direction that system should keep reference voltage to diminish, U ₂=U ₁-Δ U, U ₂be the magnitude of voltage after second time disturbance, go to step S68;

Step S66: maximum power point MPP is positioned at the left side of present operating point, the change direction that system should keep reference voltage to diminish, U ₂=U ₁-Δ U, U ₂be the magnitude of voltage after second time disturbance, go to step S68;

Step S67: maximum power point MPP is positioned at the right side of present operating point, the change trend that system should keep reference voltage to become large, U ₂=U ₁+ Δ U, U ₂be the magnitude of voltage after second time disturbance, go to step S68;

Step S68: judge whether the power output of solar cell and the difference of maximum power point MPP are ± 1%, if so, then go to step S69, otherwise, go to described step S63; Repeatedly disturbance is carried out to reference voltage in this process, voltage is changed, and make the power output of solar cell towards becoming large change trend, until the difference of the power output of described solar cell and maximum power point MPP is ± 1%; In the present embodiment, the reference voltage at this place starts to be U, is U after first time disturbance ₁, be U after second time disturbance ₂, disturbance is always gone down.Disturbance herein refers to reference voltage to be increased or reduces Δ U.Allowed band required for different capacity system is different, and in the present embodiment, the power output of solar cell and the difference of maximum power point MPP are ± 1%.

Step S69: the output voltage U of to be voltage that maximum power point MPP is corresponding by photovoltaic Output matrix power be photovoltaic matrix, output voltage U obtains described grid-connected voltage U by photovoltaic topological structure _dc.

Be more than preferred embodiment of the present invention, all changes done according to technical solution of the present invention, when the function produced does not exceed the scope of technical solution of the present invention, all belong to protection scope of the present invention.

Claims (8)

1. based on a unified control method for harmonic detecting and grid-connected instruction synthesis, it is characterized in that, realize in accordance with the following steps:

Step S1: add phase-locked loop circuit PLL and function generator generation supply voltage same-phase in circuit diagram, to eliminate the impact of grid voltage waveform sudden change on testing result;

Step S2: note three-phase voltage is respectively V _sa, V _sband V _sc, threephase load electric current is respectively i _la, i _lband i _lc, and three-phase circuit is symmetrical;

Step S3: by described threephase load current i _la, i _lband i _lcby the first Matrix C ₃₂convert, transform on the orthogonal coordinate system of alpha-beta two-phase, export two-phase transient current i _αand i _β;

Step S4: by described two-phase transient current i _αand i _βbe multiplied with the second Matrix C, obtain threephase load electric current active current i _pand threephase load reactive current component i _q;

Step S5: by described threephase load electric current active current i _pwith described threephase load reactive current component i _qcorresponding to low pass filter LPF respectively, obtain the DC component of threephase load electric current active current and the DC component of threephase load electric current reactive current

Step S6: draw P by MPPT maximum power point tracking control section _pV, and measure grid-connected voltage U _dc, with predeterminated voltage U _dc ^*grid-connected meritorious instruction current is obtained through voltage regulator AVR process

Step S7: by the DC component of described threephase load electric current active current with described grid-connected instruction current synthesis, and according to this through described second matrix inversion Matrix C ^-1and described first matrix inversion Matrix C ₂₃, output current i _fa, i _fband i _fc;

Step S8: by described threephase load current i _la, i _lband i _lccorresponding and described current i respectively _fa, i _fband i _fcsubtract each other, obtain i _lha, i _lhb, i _lhc, and i _lha, i _lhb, i _lhcbe respectively idle, the harmonic current of threephase load and the summation of grid-connected meritorious instruction current;

Step S9: by the i obtained _lha, i _lhb, i _lhcby inverter, final offset current instruction is imported electrical network.

2. a kind of unified control method based on harmonic detecting and grid-connected instruction synthesis according to claim 1, is characterized in that, in described step S2, and described three-phase voltage V _sa, V _sband V _scbe respectively:

$V_{sa}=\sqrt{2}{V}_{1}sin\mathrm{\&omega;}t$

$V_{sb}=\sqrt{2}{V}_{1}sin(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3)$

$V_{sc}=\sqrt{2}{V}_{1}sin(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3)$

Wherein, V ₁be the effective value of supply voltage first-harmonic, ω is angular frequency;

Described threephase load current i _la, i _lband i _lcfor:

$i_{La}=\underset{n=1}{\overset{\mathrm{\&infin;}}{\&Sigma;}}\sqrt{2}{I}_{n}sin(n\mathrm{\&omega;}t+{\mathrm{\&theta;}}_n)$

$i_{Lb}=\underset{n=1}{\overset{\mathrm{\&infin;}}{\&Sigma;}}\sqrt{2}{I}_{n}sin\&lsqb;n\left(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3\right)+{\mathrm{\&theta;}}_n\&rsqb;$

$i_{Lc}=\underset{n=1}{\overset{\mathrm{\&infin;}}{\&Sigma;}}\sqrt{2}{I}_{n}sin\&lsqb;n\left(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3\right)+{\mathrm{\&theta;}}_n\&rsqb;$

Wherein, n=3k ± 1, k is integer, and during k=0, n can only be 1, I _neach primary current effective value, θ _nit is initial phase angle.

3. a kind of unified control method based on harmonic detecting and grid-connected instruction synthesis according to claim 2, is characterized in that, in described step S3, and described two-phase transient current i _α, i _βcalculate in the following way:

Wherein, described first Matrix C ₃₂for:

$C_{32}=\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right].$

4. a kind of unified control method based on harmonic detecting and grid-connected instruction synthesis according to claim 3, is characterized in that, in described step S4, and described threephase load electric current active current i _pand described threephase load reactive current component i _qcalculate by following formula:

Wherein, described second Matrix C is:

$C=\left[\begin{array}{cc}sin\mathrm{\&omega;}t& -cos\mathrm{\&omega;}t\\ -cos\mathrm{\&omega;}t& -sin\mathrm{\&omega;}t\end{array}\right].$

5. a kind of unified control method based on harmonic detecting and grid-connected instruction synthesis according to claim 1, is characterized in that, in described step S5, and the DC component of described threephase load electric current active current and the DC component of described threephase load electric current reactive current for:

$\left[\begin{array}{c}\stackrel{\&OverBar;}{i_p}\\ \stackrel{\&OverBar;}{i_q}\end{array}\right]=\sqrt{3}\left[\begin{array}{c}{I}_{1}cos(-{\mathrm{\&theta;}}_n)\\ -I_{1}sin\left({\mathrm{\&theta;}}_n\right)\end{array}\right].$

6. a kind of unified control method based on harmonic detecting and grid-connected instruction synthesis according to claim 1, is characterized in that, in described step S6, specifically comprise the following steps:

Step S61: note U is initial value, fixed step size is Δ U, and sample to the magnitude of voltage exported and current value, current sampling data is I, and calculates P;

Step S62: make U ₁=U+ Δ U, samples to current value, and current sampling data is I1, and calculates P1;

Step S63: make Δ P=P ₁-P, when judging that reference voltage U changes, the situation of change of Δ P; If when reference voltage U becomes large, Δ P > 0, then go to step S64, and Δ P < 0, then go to step S65; If when reference voltage U diminishes, Δ P > 0, then go to step S66, and Δ P < 0, then go to step S67;

Step S64: maximum power point MPP is positioned at the right side of present operating point, the change trend that system should keep reference voltage to become large, makes U ₂=U ₁+ Δ U, U ₂be the magnitude of voltage after second time disturbance, go to step S68;

Step S65: maximum power point MPP is positioned at the left side of present operating point, the change direction that system should keep reference voltage to diminish, U ₂=U ₁-Δ U, U ₂be the magnitude of voltage after second time disturbance, go to step S68;

Step S66: maximum power point MPP is positioned at the left side of present operating point, the change direction that system should keep reference voltage to diminish, U ₂=U ₁-Δ U, U ₂be the magnitude of voltage after second time disturbance, go to step S68;

Step S67: maximum power point MPP is positioned at the right side of present operating point, the change trend that system should keep reference voltage to become large, U ₂=U ₁+ Δ U, U ₂be the magnitude of voltage after second time disturbance, go to step S68;

Step S68: judge whether the power output of solar cell and the difference of maximum power point MPP are ± 1%, if so, then go to step S69, otherwise, go to described step S63; Repeatedly disturbance is carried out to reference voltage in this process, voltage is changed, and make the power output of described solar cell towards becoming large change trend;

Step S69: the output voltage U of to be voltage that maximum power point MPP is corresponding by photovoltaic Output matrix power be photovoltaic matrix, output voltage U obtains described grid-connected voltage U by photovoltaic topological structure _dc.

7. a kind of unified control method based on harmonic detecting and grid-connected instruction synthesis according to claim 1, is characterized in that, in described step S7, and described output i _fa, i _fband i _fcby following calculating:

$\left[\begin{array}{c}{i}_{fa}\\ i_{fb}\\ i_{fc}\end{array}\right]=C_{23}{C}^{-1}\left[\begin{array}{c}\stackrel{\&OverBar;}{i_p}-\stackrel{\&OverBar;}{i_{pv}}\\ 0\end{array}\right]=\sqrt{\frac{2}{3}}\left[\begin{array}{c}\sin \mathrm{\&omega;}t\\ \sin \left(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3\right)\\ \sin \left(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3\right)\end{array}\right]\&lsqb;\stackrel{\&OverBar;}{i_p}-\stackrel{\&OverBar;}{i_{pv}}\&rsqb;$

Wherein, $C_{23}=\sqrt{\frac{2}{3}}\left[\begin{array}{cc}1& 0\\ -\frac{1}{2}& \frac{\sqrt{3}}{2}\\ -\frac{1}{2}& -\frac{\sqrt{3}}{2}\end{array}\right],$ $C^{-1}=\left[\begin{array}{cc}sin\mathrm{\&omega;}t& -cos\mathrm{\&omega;}t\\ -cos\mathrm{\&omega;}t& -sin\mathrm{\&omega;}t\end{array}\right],$ C ₂₃, C ^-1be respectively described first Matrix C ₃₂and the inverse matrix of described second Matrix C, ω is angular frequency.

8. a kind of unified control method based on harmonic detecting and grid-connected instruction synthesis according to claim 7, is characterized in that, in described step S8, and i _lha, i _lhband i _lhcby following calculating:

$\left[\begin{array}{c}{i}_{Lha}\\ i_{Lhb}\\ i_{Lhc}\end{array}\right]=\left[\begin{array}{c}{i}_{La}\\ i_{Lb}\\ i_{Lc}\end{array}\right]-\left[\begin{array}{c}{i}_{fa}\\ i_{fb}\\ i_{fc}\end{array}\right]=\left[\begin{array}{c}{i}_{La}\\ i_{Lb}\\ i_{Lc}\end{array}\right]-\sqrt{\frac{2}{3}}\left[\begin{array}{c}\sin \mathrm{\&omega;}t\\ \sin \left(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3\right)\\ \sin \left(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3\right)\end{array}\right]\&lsqb;\stackrel{\&OverBar;}{i_p}-\stackrel{\&OverBar;}{i_{pv}}\&rsqb;=\left[\begin{array}{c}{i}_{La}-\sqrt{\frac{2}{3}}\stackrel{\&OverBar;}{i_p}\sin \mathrm{\&omega;}t\\ i_{Lb}-\sqrt{\frac{2}{3}}\stackrel{\&OverBar;}{i_p}\sin \left(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3\right)\\ i_{Lc}-\sqrt{\frac{2}{3}}\stackrel{\&OverBar;}{i_p}\sin \left(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3\right)\end{array}\right]+\sqrt{\frac{2}{3}}\stackrel{\&OverBar;}{i_{pv}}\left[\begin{array}{c}\sin \mathrm{\&omega;}t\\ \sin \left(\mathrm{\&omega;}t-2\mathrm{\&pi;}/3\right)\\ \sin \left(\mathrm{\&omega;}t+2\mathrm{\&pi;}/3\right)\end{array}\right]$

Wherein, front portion is the harmonics and reactive current component of load electricity, and rear portion is the fundametal compoment of photovoltaic instruction current.