CN105281368A - Photovoltaic grid-connected and electric energy quality management unified control strategy - Google Patents

Abstract

The invention discloses a photovoltaic grid-connected and electric energy quality management unified control strategy comprising the following steps that 1) photovoltaic component output is detected in real time, and the operation mode of a photovoltaic grid-connected system is adjusted; when the active grid-connected conditions are not met, the photovoltaic grid-connected system operates in an electric energy quality management mode, and when the active grid-connected conditions are met, the photovoltaic grid-connected system operates in an active grid-connected and electric energy quality management unified mode; and 2) when the photovoltaic grid-connected system operates in the active grid-connected and electric energy quality management unified mode, the photovoltaic grid-connected system allocates residual capacity of the photovoltaic grid-connected system according to priority of reactive power and harmonic compensation firstly and then integrates command current based on the instantaneous power theory. Compared with conventional methods, the photovoltaic grid-connected system is enabled to have a function of actively participating in power gird electric energy quality management on the basis of maintaining the original functions so that utilization rate of an inverter is enhanced, use of an electric energy quality management device is reduced and cost is saved.

Description

A kind of grid-connected with power quality controlling Unified Control Strategy

Technical field

The present invention relates to a kind of grid-connected with power quality controlling Unified Control Strategy, belong to power electronic technology and power quality controlling research field.

Background technology

Along with social development is to the active demand of new forms of energy and the increasingly mature of photovoltaic power generation technology, photovoltaic generation has entered the spread stage.But due to randomness and the intermittence of illumination, there is photovoltaic DC-to-AC converter utilance low, the problems such as systematic economy is of poor benefits.On the other hand, along with the appearance of non-linear and impact load in a large number in electrical network, the humorous of generation involves reactive current to the pollution of public electric wire net also day by day seriously, needs a large amount of compensation arrangements to improve the quality of power supply, but the extra compensation arrangement that increases will increase the input cost of electrical network.Consider that the main circuit structure of the main circuit structure of photovoltaic combining inverter and active filter is basically identical, just control algolithm is different, therefore by its Function Integration Mechanism, can take unified control.Utilize the photovoltaic combining inverter with Unified Control Strategy to play an active part in electrical network power quality controlling, both achieved the functional expansion of photovoltaic parallel in system, improve the economic benefit of photovoltaic generation, while the improvement quality of power supply, again reduce treatment cost.

Chinese scholars had carried out correlative study to multifunctional photovoltaic parallel inverter in recent years.There is scholar that static reacance generator (SVG) has been carried out unified control with generating electricity by way of merging two or more grid systems, utilize meritorious grid-connected residual capacity to realize reactive power compensation, effectively inhibit dynamic electric voltage to fluctuate.Have the unified of scholar's research active filter and photovoltaic combining inverter to control, emphasis has set forth the composition algorithm of active current and offset current, realization gain merit grid-connected while compensate for idle and harmonic wave.The elementary tactics more than studied is all utilize meritorious grid-connected residual capacity to carry out power quality controlling, but compensation policy when considering that residual capacity can not meet idle Harmonics Compensation; And system running pattern is not furtherd investigate; More than research mostly is theoretical research and simulating, verifying, has no holonomic system and realizes.

Summary of the invention

In order to solve the problems of the technologies described above, the invention provides a kind of grid-connected with power quality controlling Unified Control Strategy.

In order to achieve the above object, the technical solution adopted in the present invention is:

A kind of grid-connected with power quality controlling Unified Control Strategy, comprise the following steps,

1) detect photovoltaic module in real time to exert oneself, adjustment photovoltaic parallel in system operational mode;

When not meeting meritorious grid-connected conditions, photovoltaic parallel in system is with power quality controlling mode operation, and when meeting meritorious grid-connected conditions, photovoltaic parallel in system runs with meritorious grid-connected and power quality controlling More General Form;

2) photovoltaic parallel in system with meritorious grid-connected and power quality controlling More General Form runs time, first according to the idle priority height with harmonic compensation, distribute the residual capacity of photovoltaic parallel in system, then integrate instruction current based on instantaneous power theory.

The process of adjustment photovoltaic parallel in system operational mode is,

Definition photovoltaic module output current threshold value is i _pvf;

As the real-time output current i of photovoltaic module _pv< i _pvftime, judge that illumination does not meet meritorious grid-connected conditions, photovoltaic parallel in system is with power quality controlling mode operation;

As the real-time output current i of photovoltaic module _pv>=i _pvftime, judge that illumination meets meritorious grid-connected conditions, photovoltaic parallel in system is with meritorious grid-connected and power quality controlling More General Form operation, under this pattern, it is meritorious that photovoltaic module exports, a part is for overcoming the switching loss of photovoltaic parallel in system, and a part controls to be converted to grid-connected active current by DC side PI.

According to the idle priority height with harmonic compensation, the process of distributing the residual capacity of photovoltaic parallel in system is,

A1) adopt ip-iq method to detect load current, extract meritorious, idle and harmonic current, and calculate the effective value I getting active current _p, reactive current effective value I _qand the effective value I of harmonic current _h;

A2) defining rated capacity is I _s, then residual capacity

A3) if when residual capacity is abundant, namely then can meet full compensation that is idle and harmonic wave, obtain reactive power compensation coefficient k _qwith harmonic wave penalty coefficient k _h; If when residual capacity is not abundant, namely then can according to the idle priority height with harmonic compensation, a certain component of preferential compensation, obtains reactive power compensation coefficient k _qwith harmonic wave penalty coefficient k _h;

A4) residual capacity is distributed according to penalty coefficient;

Reactive capability after distribution is I _q ^*=k _qi _q, the harmonic wave capacity after distribution is I _h ^*=k _hi _h.

Calculate the effective value I getting active current _p, reactive current effective value I _qand the effective value I of harmonic current _hprocess be,

B1) defining load-side three-phase current is i _a, i _b, i _c;

Wherein, ω t is the phase place of line voltage, represent the phase difference of n voltage and electric current, I _nrepresent n primary current;

B2) three-phase current is done meritorious obtain i with idle decoupling zero _p, i _q;

Wherein,

$C=\left[\begin{array}{cc}sin\mathrm{\&omega;}t& -cos\mathrm{\&omega;}t\\ -cos\mathrm{\&omega;}t& -sin\mathrm{\&omega;}t\end{array}\right],C_{32}=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right];$

B3) by i _p, i _qdC component is obtained through low pass filter wherein, for active current, for reactive current component;

B4) by i _p, i _qdeduct respectively to alternating current component i.e. harmonic component;

B5) will carry out inverse transformation and obtain reactive current;

$\left[\begin{array}{c}{i}_{aq}\\ i_{bq}\\ i_{cq}\end{array}\right]=C_{23}{C}^{-1}\&lsqb;\frac{0}{i_q}\&rsqb;$

Wherein, C ₂₃, C ^-1be respectively C ₃₂, C inverse matrix, i _aq, i _bq, i _cqrepresent three-phase reactive current;

Will carry out inverse transformation and obtain harmonic current;

$\left[\begin{array}{c}{i}_{ah}\\ i_{bh}\\ i_{ch}\end{array}\right]=C_{23}{C}^{-1}\left[\begin{array}{c}{\tilde{i}}_p\\ {\tilde{i}}_q\end{array}\right]$

Wherein, i _ah, i _bh, i _chrepresent three phase harmonic electric current;

B6) reactive current integration is obtained to the effective value I of reactive current _q;

$I_q=\sqrt{\frac{1}{T}{\&Integral;}_0^T{i}_{aq}^{2}dt}$

Wherein, T represents integration period;

Harmonic current integration is obtained to the effective value I of harmonic current _h;

$I_h=\sqrt{\frac{1}{T}{\&Integral;}_0^T{i}_{ah}^{2}dt};$

B7) because active current is synchronous fundamental current with line voltage, therefore the effective value of active current is wherein, i _pdcfor DC voltage control exports meritorious grid-connected component.

Component after decoupling zero is controlled, the code reassignment of photovoltaic parallel in system residual capacity can be realized, obtain compensating instruction electric current;

$\left\{\begin{array}{c}{\tilde{i}}_p^{*}=k_h{\tilde{i}}_p\\ {\tilde{i}}_p^{*}=k_h{\tilde{i}}_p\\ \stackrel{\&OverBar;}{i_p^{*}}=k_q\stackrel{\&OverBar;}{i_p}\end{array}\right.$

Wherein, for reactive power compensation command current, with for harmonic compensation instruction current;

Reactive power compensation command current, harmonic compensation instruction current and active current instruction is integrated based on instantaneous power theory;

Integration formula is,

$\left[\begin{array}{c}{i_a}^{*}\\ {i_b}^{*}\\ {i_c}^{*}\end{array}\right]=C_{23}{C}^{-1}\left[\begin{array}{c}{i}_{pdc}+{\tilde{i}}_p^{*}\\ \stackrel{\&OverBar;}{i_q^{*}}+{\tilde{i}}_q^{*}\end{array}\right]=C_{23}{C}^{-1}\left[\begin{array}{c}{i}_{pdc}+k_h{\tilde{i}}_p\\ k_q\stackrel{\&OverBar;}{i_q}+k_h{\tilde{i}}_q\end{array}\right]$

Wherein, i _a ^*, i _b ^*, i _c ^*for the three-phase instruction current three-phase after integration.

The beneficial effect that the present invention reaches: the present invention is compared to conventional method, make photovoltaic parallel in system on the basis keeping original function, possess the function of active participate electrical network power quality controlling, improve the utilance of inverter, decrease the input of power quality controlling device, save cost.

Accompanying drawing explanation

Fig. 1 is principle of the present invention.

Fig. 2 is the strategy of adjustment photovoltaic parallel in system operational mode.

Fig. 3 is that residual capacity distributes and instruction electric current integral traffic control strategy.

Fig. 4 is controller soft hardware configuration.

Fig. 5 is experimental program.

Full remuneration that Fig. 6 is unglazed/have light compensates and DC voltage waveform under generating operating mode.

Full remuneration that Fig. 7 is unglazed/have light compensates and network side current waveform under generating operating mode.

Fig. 8 is power quality controlling mode operation effect.

Fig. 9 is the waveform after a state compensation.

Figure 10 is the waveform after b state compensation.

Figure 11 is the waveform after c state compensation.

Figure 12 is the waveform after d state compensation.

Figure 13 is the waveform after e state compensation.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.Following examples only for technical scheme of the present invention is clearly described, and can not limit the scope of the invention with this.

As shown in Figure 1, a kind of grid-connected with power quality controlling Unified Control Strategy, comprise the following steps:

1) detect photovoltaic module in real time to exert oneself, adjustment photovoltaic parallel in system operational mode.

When not meeting meritorious grid-connected conditions, photovoltaic parallel in system is with power quality controlling mode operation, and when meeting meritorious grid-connected conditions, photovoltaic parallel in system runs with meritorious grid-connected and power quality controlling More General Form.

Specifically as shown in Figure 2:

Definition photovoltaic module output current threshold value is i _pvf;

As the real-time output current i of photovoltaic module _pv< i _pvftime, judge that illumination does not meet meritorious grid-connected conditions, photovoltaic parallel in system is with power quality controlling mode operation; DC side reference voltage adopts steady state value; In this mode, DC side PI control by regulate from electrical network absorb active current number, overcome the switching loss of photovoltaic parallel in system, holding power balance, burning voltage;

As the real-time output current i of photovoltaic module _pv>=i _pvftime, judge that illumination meets meritorious grid-connected conditions, photovoltaic parallel in system is with meritorious grid-connected and power quality controlling More General Form operation, under this pattern, it is meritorious that photovoltaic module exports, a part is for overcoming the switching loss of photovoltaic parallel in system, and a part controls to be converted to grid-connected active current by DC side PI.

2) photovoltaic parallel in system with meritorious grid-connected and power quality controlling More General Form runs time, first according to the idle priority height with harmonic compensation, distribute the residual capacity of photovoltaic parallel in system, then integrate instruction current based on instantaneous power theory.

Photovoltaic parallel in system is realizing under the grid-connected prerequisite of maximum active power, and its residual capacity is limited, possibly cannot meet the full compensation to idle harmonic wave, need to redistribute residual capacity.

As shown in Figure 3, according to the idle priority height with harmonic compensation, the process of distributing the residual capacity of photovoltaic parallel in system is:

A1) adopt ip-iq method to detect load current, extract meritorious, idle and harmonic current, and calculate the effective value I getting active current _p, reactive current effective value I _qand the effective value I of harmonic current _h.

Calculate the effective value I getting active current _p, reactive current effective value I _qand the effective value I of harmonic current _hprocess be:

B1) defining load-side three-phase current is i _a, i _b, i _c;

Wherein, ω t is the phase place of line voltage, is obtained by phase-locked loop, represent the phase difference of n voltage and electric current, I _nrepresent n primary current;

B2) three-phase current is done meritorious obtain i with idle decoupling zero _p, i _q;

Wherein,

$C=\left[\begin{array}{cc}sin\mathrm{\&omega;}t& -cos\mathrm{\&omega;}t\\ -cos\mathrm{\&omega;}t& -sin\mathrm{\&omega;}t\end{array}\right],C_{32}=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right];$

B3) by i _p, i _qdC component is obtained through low pass filter wherein, for active current, for reactive current component;

B4) by i _p, i _qdeduct respectively to alternating current component i.e. harmonic component;

B5) will carry out inverse transformation and obtain reactive current;

$\left[\begin{array}{c}{i}_{aq}\\ i_{bq}\\ i_{cq}\end{array}\right]=C_{23}{C}^{-1}\&lsqb;\frac{0}{i_q}\&rsqb;$

Wherein, C ₂₃, C ^-1be respectively C ₃₂, C inverse matrix, i _aq, i _bq, i _cqrepresent three-phase reactive current;

Will carry out inverse transformation and obtain harmonic current;

$\left[\begin{array}{c}{i}_{ah}\\ i_{bh}\\ i_{ch}\end{array}\right]=C_{23}{C}^{-1}\left[\begin{array}{c}{\tilde{i}}_p\\ {\tilde{i}}_q\end{array}\right]$

Wherein, i _ah, i _bh, i _chrepresent three phase harmonic electric current;

B6) reactive current integration is obtained to the effective value I of reactive current _q;

$I_q=\sqrt{\frac{1}{T}{\&Integral;}_0^T{i}_{aq}^{2}dt}$

Wherein, T represents integration period;

Harmonic current integration is obtained to the effective value I of harmonic current _h;

$I_h=\sqrt{\frac{1}{T}{\&Integral;}_0^T{i}_{ah}^{2}dt};$

B7) because active current is synchronous fundamental current with line voltage, therefore the effective value of active current is wherein, i _pdcfor DC voltage control exports meritorious grid-connected component.

A2) defining rated capacity is I _s, then residual capacity

A3) if when residual capacity is abundant, namely then can meet full compensation that is idle and harmonic wave, obtain reactive power compensation coefficient k _qwith harmonic wave penalty coefficient k _h; If when residual capacity is not abundant, namely then can according to the idle priority height with harmonic compensation, a certain component of preferential compensation, obtains reactive power compensation coefficient k _qwith harmonic wave penalty coefficient k _h.

Penalty coefficient as shown in Table 1.

Table one is based on the compensation policy of priority

A4) residual capacity is distributed according to penalty coefficient;

Reactive capability after distribution is I _q ^*=k _qi _q, the harmonic wave capacity after distribution is I _h ^*=k _hi _h.

As shown in Figure 4, the component after decoupling zero is controlled, the code reassignment of photovoltaic parallel in system residual capacity can be realized, obtain compensating instruction electric current;

$\left\{\begin{array}{c}{\tilde{i}}_p^{*}=k_h{\tilde{i}}_p\\ {\tilde{i}}_p^{*}=k_h{\tilde{i}}_p\\ \stackrel{\&OverBar;}{i_p^{*}}=k_q\stackrel{\&OverBar;}{i_p}\end{array}\right.$

Wherein, for reactive power compensation command current, with for harmonic compensation instruction current;

Reactive power compensation command current, harmonic compensation instruction current and active current instruction is integrated based on instantaneous power theory;

Integration formula is,

$\left[\begin{array}{c}{i_a}^{*}\\ {i_b}^{*}\\ {i_c}^{*}\end{array}\right]=C_{23}{C}^{-1}\left[\begin{array}{c}{i}_{pdc}+{\tilde{i}}_p^{*}\\ \stackrel{\&OverBar;}{i_q^{*}}+{\tilde{i}}_q^{*}\end{array}\right]=C_{23}{C}^{-1}\left[\begin{array}{c}{i}_{pdc}+k_h{\tilde{i}}_p\\ k_q\stackrel{\&OverBar;}{i_q}+k_h{\tilde{i}}_q\end{array}\right]$

Wherein, i _a ^*, i _b ^*, i _c ^*for the three-phase instruction current three-phase after integration.

As shown in Figure 5, experimental program, utilizes 1 programmable DC power supply simulated light photovoltaic assembly, 1 uncontrollable rectifier unit simulation harmonic source, its DC terminal connecting resistance, 1 programmable load simulation reactive load.14 oscilloscope channel gathers DC voltage u respectively _dc, A phase voltage on line side e _a, current on line side i _ga, inverter output current i _ca.A phase load electric current is i _a, electric current meets equation i _ga=i _a-i _ca.

As shown in Figures 6 and 7,0-22s photovoltaic parallel in system is with power quality controlling mode operation, and now DC side reference voltage is definite value 360V.Photo-voltaic power supply is dropped into during 22s, the situation that illumination simulation increases, systems axiol-ogy is greater than threshold values to photovoltaic module output current, grid-connectedly to run with power quality controlling More General Form with meritorious, now grid-connected for realizing maximum power, DC side reference voltage is generated by MPPT algorithm, 22 ~ 33s system searches maximum power point, the amplitude of visible current on line side, in continuous increase, is finally stabilized in about 345V, achieves the grid-connected and power quality compensation of maximum power.41s cuts away simulation photo-voltaic power supply, and illumination simulation weakens suddenly, and systems axiol-ogy exports lower than threshold values to photovoltaic, and with quality of power supply mode operation, DC side reference voltage gets back to definite value 360V.

Photovoltaic module does not generate electricity, and photovoltaic parallel in system, with quality of power supply mode operation, drops into uncontrollable rectifier device, and programmable load is adjusted to perceptual reactive load.As shown in Figure 8, before system drops into, current on line side aberration rate is 21.2%, power factor 0.65, and after dropping into, the aberration rate of current on line side is 4.3%, and power factor 0.96, reaches compensation effect.

When illumination is abundant, photovoltaic parallel in system is unified control model with power quality controlling run with grid-connected.First meet maximum power in this mode grid-connected, secondly residual capacity is used for compensating, realizes idle Harmonics Compensation when residual capacity is abundant; Carry out undercompensation according to idle with the priority height of harmonic wave when residual capacity is not enough, priority artificially sets according to the demand of electrical network.Exported and load by adjustment photovoltaic, simulate 5 kinds of states that may occur, to be that residual capacity is abundant meet the full state compensated to a state, and all the other 4 kinds can not meet the state of full compensation for residual capacity.When adopting idle preferential compensation, b state is that reactive component compensates, harmonic wave uncompensation; C state is idle full compensation, and harmonic compensates.When adopting harmonic wave preferentially to compensate, d state is Harmonics Compensation, and reactive component compensates; E state is that harmonic compensates, idle uncompensation.Corresponding state parameter and penalty coefficient are as shown in Table 2.

The compensation policy of table two different conditions

The compensation effect of table three different conditions

Waveform after 5 kinds of state compensations is as shown in Fig. 9,10,11,12,13, and as shown in Table 3, the power factor of compensation front and back grid side and aberration rate meet the compensation policy of 5 kinds of states, demonstrate the feasibility of this strategy.

In sum, above-mentioned grid-connected with power quality controlling Unified Control Strategy, when illumination is good, photovoltaic parallel in system to run with power quality controlling More General Form to generate electricity by way of merging two or more grid systems; When illumination is bad, take power quality controlling mode operation, study the operational mode of exerting oneself based on photovoltaic module to switch and DC side voltage control method, the inverter capacity proposed based on idle/harmonic wave priority distributes and instruction current synthesis strategy, develop the controller based on FPGA+RT framework, build experiment grid-connected system, demonstrate the performance of photovoltaic parallel in system under different operational mode.Compared to conventional method, make photovoltaic system on the basis keeping original function, possess the function of active participate electrical network power quality controlling, improve the utilance of inverter, decrease the input of power quality controlling device, saved cost.

The above is only the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the prerequisite not departing from the technology of the present invention principle; can also make some improvement and distortion, these improve and distortion also should be considered as protection scope of the present invention.

Claims (5)

1. grid-connected with a power quality controlling Unified Control Strategy, it is characterized in that: comprise the following steps,

1) detect photovoltaic module in real time to exert oneself, adjustment photovoltaic parallel in system operational mode;

When not meeting meritorious grid-connected conditions, photovoltaic parallel in system is with power quality controlling mode operation, and when meeting meritorious grid-connected conditions, photovoltaic parallel in system runs with meritorious grid-connected and power quality controlling More General Form;

2) photovoltaic parallel in system with meritorious grid-connected and power quality controlling More General Form runs time, first according to the idle priority height with harmonic compensation, distribute the residual capacity of photovoltaic parallel in system, then integrate instruction current based on instantaneous power theory.

2. one according to claim 1 is grid-connected with power quality controlling Unified Control Strategy, it is characterized in that: the process of adjustment photovoltaic parallel in system operational mode is,

Definition photovoltaic module output current threshold value is i _pvf;

As the real-time output current i of photovoltaic module _pv< i _pvftime, judge that illumination does not meet meritorious grid-connected conditions, photovoltaic parallel in system is with power quality controlling mode operation;

As the real-time output current i of photovoltaic module _pv>=i _pvftime, judge that illumination meets meritorious grid-connected conditions, photovoltaic parallel in system is with meritorious grid-connected and power quality controlling More General Form operation, under this pattern, it is meritorious that photovoltaic module exports, a part is for overcoming the switching loss of photovoltaic parallel in system, and a part controls to be converted to grid-connected active current by DC side PI.

3. one according to claim 2 is grid-connected with power quality controlling Unified Control Strategy, it is characterized in that: according to the idle priority height with harmonic compensation, the process of distributing the residual capacity of photovoltaic parallel in system is,

A1) adopt ip-iq method to detect load current, extract meritorious, idle and harmonic current, and calculate the effective value I getting active current _p, reactive current effective value I _qand the effective value I of harmonic current _h;

A2) defining rated capacity is I _s, then residual capacity

A3) if when residual capacity is abundant, namely then can meet full compensation that is idle and harmonic wave, obtain reactive power compensation coefficient k _qwith harmonic wave penalty coefficient k _h; If when residual capacity is not abundant, namely then can according to the idle priority height with harmonic compensation, a certain component of preferential compensation, obtains reactive power compensation coefficient k _qwith harmonic wave penalty coefficient k _h;

A4) residual capacity is distributed according to penalty coefficient;

Reactive capability after distribution is I _q ^*=k _qi _q, the harmonic wave capacity after distribution is I _h ^*=k _hi _h.

4. one according to claim 3 is grid-connected with power quality controlling Unified Control Strategy, it is characterized in that: calculate the effective value I getting active current _p, reactive current effective value I _qand the effective value I of harmonic current _hprocess be,

B1) defining load-side three-phase current is i _a, i _b, i _c;

Wherein, ω t is the phase place of line voltage, represent the phase difference of n voltage and electric current, I _nrepresent n primary current;

B2) three-phase current is done meritorious obtain i with idle decoupling zero _p, i _q;

Wherein,

$C=\left[\begin{array}{cc}sin\mathrm{\&omega;}t& -cos\mathrm{\&omega;}t\\ -cos\mathrm{\&omega;}t& -sin\mathrm{\&omega;}t\end{array}\right],C_{32}=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right];$

B3) by i _p, i _qdC component is obtained through low pass filter wherein, for active current, for reactive current component;

B4) by i _p, i _qdeduct respectively to alternating current component i.e. harmonic component;

B5) will carry out inverse transformation and obtain reactive current;

$\left[\begin{array}{c}{i}_{aq}\\ i_{bq}\\ i_{cq}\end{array}\right]=C_{23}{C}^{-1}\left[\begin{array}{c}0\\ \stackrel{\&OverBar;}{i_q}\end{array}\right]$

Wherein, C ₂₃, C ^-1be respectively C ₃₂, C inverse matrix, i _aq, i _bq, i _cqrepresent three-phase reactive current;

Will carry out inverse transformation and obtain harmonic current;

$\left[\begin{array}{c}{i}_{ah}\\ i_{bh}\\ i_{ch}\end{array}\right]=C_{23}{C}^{-1}\left[\begin{array}{c}{\tilde{i}}_p\\ {\tilde{i}}_q\end{array}\right]$

Wherein, i _ah, i _bh, i _chrepresent three phase harmonic electric current;

B6) reactive current integration is obtained to the effective value I of reactive current _q;

$I_q=\sqrt{\frac{1}{T}{\&Integral;}_0^T{i}_{aq}^{2}dt}$

Wherein, T represents integration period;

Harmonic current integration is obtained to the effective value I of harmonic current _h;

$I_h=\sqrt{\frac{1}{T}{\&Integral;}_0^T{i}_{ah}^{2}dt};$

B7) because active current is synchronous fundamental current with line voltage, therefore the effective value of active current is wherein, i _pdcfor DC voltage control exports meritorious grid-connected component.

5. one according to claim 4 is grid-connected with power quality controlling Unified Control Strategy, it is characterized in that: control the component after decoupling zero, can realize the code reassignment of photovoltaic parallel in system residual capacity, obtains compensating instruction electric current;

$\left\{\begin{array}{c}{\tilde{i}}_p^{*}=k_h{\tilde{i}}_p\\ {\tilde{i}}_q^{*}=k_h{\tilde{i}}_q\\ \stackrel{\&OverBar;}{i_q^{*}}=k_q\stackrel{\&OverBar;}{i_p}\end{array}\right.$

Wherein, for reactive power compensation command current, with for harmonic compensation instruction current;

Reactive power compensation command current, harmonic compensation instruction current and active current instruction is integrated based on instantaneous power theory;

Integration formula is,

$\left[\begin{array}{c}{i_a}^{*}\\ {i_b}^{*}\\ {i_c}^{*}\end{array}\right]=C_{23}{C}^{-1}\left[\begin{array}{c}{i}_{pdc}+{\tilde{i}}_p^{*}\\ \stackrel{\&OverBar;}{i_q^{*}}+{\tilde{i}}_q^{*}\end{array}\right]=C_{23}{C}^{-1}\left[\begin{array}{c}{i}_{pdc}+k_h{\tilde{i}}_p\\ k_q\stackrel{\&OverBar;}{i_q}+k_h{\tilde{i}}_q\end{array}\right]$

Wherein, i _a ^*, i _b ^*, i _c ^*for the three-phase instruction current three-phase after integration.