CN105244910A - Control method for improving power quality of alternating current buses of micro-grid - Google Patents

Abstract

The invention discloses a control method for improving power quality of alternating current buses of a micro-grid. The control method comprises a voltage optimum control strategy, a current optimum control strategy and a current compensation control strategy. Each distributed power supply inverter in the micro-grid automatically detects the unbalance degree and the distortion degree of each accessed alternating current bus, and automatically switches the corresponding control strategy according to different operation modes of the micro-grid and the influence degrees on distributed power supplies in the micro-grid caused by unbalance loads or nonlinear loads; and the switching process does not affect a transient process in a micro-grid operation. According to the method, harmonics and imbalance on the alternating current buses in an island operation mode and a grid-connected operation mode can be simultaneously compensated; the quality of exchange power of the micro-grid and a large power grid is improved; and the micro-grid can meet the requirements of the international standard on the power quality in the grid-connected and island modes.

Description

A kind of control method improving the micro-capacitance sensor ac bus quality of power supply

Technical field

The present invention relates to a kind of control method improving the micro-capacitance sensor ac bus quality of power supply.

Background technology

Micro-capacitance sensor is the important component part of intelligent grid, as the effective carrier of new forms of energy and distributed power generation, the flexibility of power system operation, economy and spatter property can be improved further, meeting the requirement of power consumer to the quality of power supply, power supply reliability and fail safe better, is significant technology, economy, environmental benefit that electric power system and user bring.Micro-capacitance sensor can be incorporated into the power networks, when there is fluctuation in electrical network, and also can off-grid islet operation.

When accessing nonlinear load or unbalanced load in micro-capacitance sensor, if not taking effective counter-measure, will cause that distributed electrical source efficiency is lower, subscriber equipment damages, power supply reliability reduces, and even affects the stable operation of electric power system time serious.In fact, the important load in micro-capacitance sensor is generally all directly connected on ac bus.International Electrical and Electronic Engineering Association (IEEE) have promulgated that IEEE1547.4-2011 international standard has carried out specific provision to the quality that micro-capacitance sensor and bulk power grid exchange electric energy.When micro-capacitance sensor islet operation, ensure the stable of direct voltage, reduction DC bus-bar voltage imbalance and harmonic distortion are primary control objectives; When micro-grid connection is run, the quality of power supply on micro-capacitance sensor ac bus directly determines the quality exchanging electric energy with bulk power grid, and reduction DC bus current imbalance and harmonic distortion are primary control objectives.Therefore, the quality of power supply of micro-capacitance sensor ac bus is the most important thing of micro-capacitance sensor quality of power supply research.

Existing patent and document just carry out ME for maintenance by meritorious and Reactive Power Control to the research of the micro-capacitance sensor quality of power supply and stablize, the patent " a kind of control method improving the micro-grid system quality of power supply " being 201410261493.4 as application number carries out reactive power compensation by controlling three-phase grid-connected inverter, maintains direct voltage constant.Application number be 201110086457.5 patent compensate the power fluctuation of micro-capacitance sensor, to reduce voltage variety by control inverter.At present, the three-phase imbalance in micro-capacitance sensor and harmonic problem are not still studied, also do not have correlative study for the power quality problem under micro-grid connection and the pattern that is incorporated into the power networks and in mode handover procedure.

Summary of the invention

The present invention, in order to solve the problem, proposes a kind of control method improving the micro-capacitance sensor ac bus quality of power supply, and the method comprises voltage optimal control policy, electric current optimal control policy and current compensation control strategy.The operational mode different for micro-capacitance sensor and by difference that is uneven or nonlinear load influence degree, be switched to corresponding control strategy in micro-capacitance sensor distributed electrical source inventer automatic smoothing, improve the micro-capacitance sensor ac bus quality of power supply, make the quality of power supply of micro-capacitance sensor under grid-connected and island mode all can meet the requirement of international standard.

To achieve these goals, the present invention adopts following technical scheme:

Improve a control method for the micro-capacitance sensor ac bus quality of power supply, comprise the following steps:

(1) gather micro-capacitance sensor distributed electrical source inventer filter capacitor voltage and and filter inductance electric current, calculate meritorious and reactive power, obtain reference voltage, according to microgrid operational mode, select a control strategy in step (2)-(4) to regulate;

(2) carry out voltage optimal control, carry out fundamental voltage control and harmonic voltage control with reference to the error after voltage and filter capacitor voltage compare, export after adding up and obtain reference current;

(3) carry out electric current optimal control, carry out fundamental voltage control, with reference to harmonic current I with reference to the error after voltage and filter capacitor voltage compare _dG=0 with filter inductance current ratio comparatively after error carry out harmonic current control, both control, and result is cumulative obtains reference current;

(4) carry out current compensation control, carry out fundamental voltage control, with reference to harmonic current I with reference to the error after voltage and filter capacitor voltage compare _dG=I _localwith filter inductance current ratio comparatively after error carry out harmonic current control, both control, and result is cumulative obtains reference current;

(5) make comparisons with reference to electric current and inverter output current, and carry out inner ring Current Control, carry out pulse-width modulation generation.

The concrete grammar of described step (1) is:

The filter capacitor voltage V of sampling micro-capacitance sensor distributed electrical source inventer _cwith filter inductance electric current I ₂calculate active-power P _lPFand reactive power Q _lPF, input power controller obtains reference voltage V _dG, the expression formula of power controller is as follows:

ω _DG＝ω ^*+m(P _rated-P _LPF)

E _DG＝E ^*+n(Q _rated-Q _LPF)

V _DG＝E _DGcosω _DGt

Wherein, ω ^*for reference angle frequency, E ^*for reference voltage amplitude, m is the sagging coefficient of active power, and n is the sagging coefficient of reactive power, P _ratedfor the specified active power of inverter, Q _ratedfor the rated reactive power of inverter.

Further, when micro-capacitance sensor islet operation, when access point current unbalance factor or the degree of distortion are less than setting threshold, distributed electrical source inventer adopts voltage optimal control policy, improves the quality of voltage of ac bus; When current unbalance factor or the degree of distortion are greater than setting threshold, distributed electrical source inventer adopts current compensation control strategy, and compensating non-linear load or unbalanced load are on the impact of the ac bus quality of power supply.

When micro-grid connection is run, if when access point current unbalance factor or the degree of distortion are less than setting threshold, distributed electrical source inventer adopts electric current optimal control policy, improves the current quality of ac bus; When current unbalance factor or the degree of distortion are greater than setting threshold, distributed electrical source inventer adopts current compensation control strategy, and compensating non-linear load or unbalanced load are on the impact of the ac bus quality of power supply.

The concrete grammar of described step (2) comprising:

With reference to voltage V _dGwith filter capacitor voltage V _cerror input fundamental voltage control device G relatively _fVwith harmonic voltage controller G _hV, exporting adds up obtains reference current I _dG.Fundamental voltage control device G _fVexpression formula as follows:

$G_{FV}\left(s\right)=K_{pv}+\frac{K_{iv}}{s}$

Wherein, K _pv, K _ivbe respectively proportional gain and storage gain.Harmonic voltage control device G _hVexpression formula as follows:

$G_{HV}\left(s\right)=\underset{h=2,6,\mathrm{...}}{\Σ}\frac{K_{rvh}{\mathrm{\ω}}_{cvh}s}{s^2+2{\mathrm{\ω}}_{cvh}s+{(\±h\·{\mathrm{\ω}}_s)}^2}$

Wherein, K _rvhfor harmonic frequency ± h ω _sthe resonance gain at place, ω _cvhfor harmonic frequency ± h ω _sthe cut-off frequency at place, ω _sfor first-harmonic angular frequency, h is harmonic number.

In described step (3), with reference to voltage V _dGwith filter capacitor voltage V _cerror input fundamental voltage control device G relatively _fV, with reference to harmonic current I _dG=0 with filter inductance electric current I ₂error input harmonic current controller G relatively _hC, G _fVand G _hCexporting adds up obtains reference current I _dG.Fundamental voltage control device G _fVexpression formula as follows:

$G_{FV}\left(s\right)=K_{pv}+\frac{K_{iv}}{s}$

Wherein, K _pv, K _ivbe respectively proportional gain and storage gain, harmonic current controller G _hCexpression formula as follows:

$G_{HC}\left(s\right)=\underset{h=2,6,\mathrm{...}}{\Σ}\frac{K_{rih}{\mathrm{\ω}}_{ch}s}{s^2+2{\mathrm{\ω}}_{cih}s+{(\±h\·{\mathrm{\ω}}_s)}^2}$

Wherein, K _rihfor harmonic frequency ± h ω _sthe resonance gain at place, ω _cihfor harmonic frequency ± h ω _sthe cut-off frequency at place, ω _sfor first-harmonic angular frequency, h is harmonic number.

In described step (4), with reference to voltage V _dGwith filter capacitor voltage V _cerror input fundamental voltage control device G relatively _fV, with reference to harmonic current I _dG=I _localwith filter inductance electric current I ₂error input harmonic current controller G relatively _hC, G _fVand G _hCexporting adds up obtains reference current I _dG, fundamental voltage control device G _fVexpression formula as follows:

$G_{FV}\left(s\right)=K_{pv}+\frac{K_{iv}}{s}$

Wherein, K _pv, K _ivbe respectively proportional gain and storage gain.Harmonic current controller G _hCexpression formula as follows:

$G_{HC}\left(s\right)=\underset{h=2,6,\mathrm{...}}{\Σ}\frac{K_{rih}{\mathrm{\ω}}_{ch}s}{s^2+2{\mathrm{\ω}}_{cih}s+{(\±h\·{\mathrm{\ω}}_s)}^2}$

Wherein, K _rihfor harmonic frequency ± h ω _sthe resonance gain at place, ω _cihfor harmonic frequency ± h ω _sthe cut-off frequency at place, ω _sfor first-harmonic angular frequency, h is harmonic number.

In described step (5), reference current I _dGwith inverter output current I ₂error input inner ring current controller G relatively _inner, export and enter in pulse-width modulation (PWM) generator of inverter.Inner ring current controller G _innerexpression formula as follows:

G _inner(s)＝K _pi

Wherein, K _pifor proportional gain.

Further, each distributed electrical source inventer in micro-capacitance sensor all gathers the electric current I at its access point place separately _local, and calculating current degree of unbalance and current distortion degree, current distortion degree HF is the value added up to multiple harmonic after carrying out fast Fourier transform to electric current.

Further, to the computing formula of degree of unbalance UF:

$UF=\frac{\sqrt{{\left(I_{localD}^{-}\right)}^2+{\left(I_{localQ}^{-}\right)}^2}}{\sqrt{{\left(I_{localD}^{+}\right)}^2+{\left(I_{localQ}^{+}\right)}^2}}\×100\%$

Wherein, be respectively I _localnegative sequence component rotating coordinate transformation after D axle component and Q axle component; be respectively I _localpositive sequence component rotating coordinate transformation after D axle component and Q axle component.

Beneficial effect of the present invention is:

(1) the micro-capacitance sensor distributed electrical source inventer in this invention automatically gathers the electric current at incoming transport bus place and calculates degree of unbalance and the degree of distortion, implementation method is simple and input cost is low, meets the plug and play of distributed power source in micro-capacitance sensor and the function needs of hot plug.

(2) this invention proposes three kinds of micro-capacitance sensor distributed power source control strategy for inverters based on pi controller+resonant controller, voltage optimal control policy can improve the quality of inverter output voltage, electric current optimal control policy can improve the quality of inverter output current, current compensation control strategy can compensate the current harmonics of access point, three kinds of control strategies can compensate the harmonic wave of unbalanced load and nonlinear load generation simultaneously, and three kinds of control strategies can realize take over seamlessly, the transient process of micro-capacitance sensor is not affected.

(3) operational mode that each distributed electrical source inventer in this invention in micro-capacitance sensor is different according to micro-capacitance sensor, automatic detection is the degree of unbalance at incoming transport bus place and the degree of distortion separately, and the corresponding control strategy that automatically switches, micro-capacitance sensor islet operation pattern and the harmonic wave on the ac bus under the pattern that is incorporated into the power networks and imbalance can be compensated simultaneously, improve the quality that micro-capacitance sensor and bulk power grid exchange electric energy, make micro-capacitance sensor grid-connected with island mode under all can meet the requirement of international standard to the quality of power supply.

Accompanying drawing explanation

Fig. 1 is micro-capacitance sensor distributed power source control strategy structure chart;

Fig. 2 is the micro-capacitance sensor structural representation containing multiple distributed power source;

Fig. 3 adopts the wave form varies that before and after the method, islet operation micro-capacitance sensor distributed power source runs;

Fig. 4 is the micro-capacitance sensor distributed power source operation waveform that is incorporated into the power networks before employing the method;

Fig. 5 is the micro-capacitance sensor distributed power source operation waveform that is incorporated into the power networks after employing the method.

Embodiment:

Below in conjunction with accompanying drawing and embodiment, the invention will be further described.

The present invention proposes the different control strategies of distributed electrical source inventer in micro-capacitance sensor, wherein the implementation method of voltage optimal control policy comprises:

(1) the filter capacitor voltage V of sampling micro-capacitance sensor distributed electrical source inventer _cwith filter inductance electric current I ₂calculate active-power P _lPFand reactive power Q _lPF, input power controller obtains reference voltage V _dG.The expression formula of power controller is as follows:

ω _DG＝ω ^*+m(P _rated-P _LPF)

E _DG＝E ^*+n(Q _rated-Q _LPF)

V _DG＝E _DGcosω _DGt

Wherein, ω ^*for reference angle frequency, E ^*for reference voltage amplitude, m is the sagging coefficient of active power, and n is the sagging coefficient of reactive power, P _ratedfor the specified active power of inverter, Q _ratedfor the rated reactive power of inverter.

(2) with reference to voltage V _dGwith filter capacitor voltage V _cerror input fundamental voltage control device G relatively _fVwith harmonic voltage controller G _hV, exporting adds up obtains reference current I _dG.Fundamental voltage control device G _fVexpression formula as follows:

$G_{FV}\left(s\right)=K_{pv}+\frac{K_{iv}}{s}$

Wherein, K _pv, K _ivbe respectively proportional gain and storage gain.Harmonic voltage control device G _hVexpression formula as follows:

$G_{HV}\left(s\right)=\underset{h=2,6,\mathrm{...}}{\Σ}\frac{K_{rvh}{\mathrm{\ω}}_{cvh}s}{s^2+2{\mathrm{\ω}}_{cvh}s+{(\±h\·{\mathrm{\ω}}_s)}^2}$

Wherein, K _rvhfor harmonic frequency ± h ω _sthe resonance gain at place, ω _cvhfor harmonic frequency ± h ω _sthe cut-off frequency at place, ω _sfor first-harmonic angular frequency, h is harmonic number.Under rotating coordinate system, when having unbalanced load near distributed electrical source inventer access point, the voltage and current at access point place contains 2 order harmonic components; When having unbalanced load near distributed electrical source inventer access point, the voltage and current at access point place is mainly containing 6 times, 8 times, 12 times, 14 order harmonic components.Therefore, harmonic voltage control device G _hVmiddle harmonic number h gets 2,6,8,12,14.

(3) reference current I _dGwith inverter output current I ₂error input inner ring current controller G relatively _inner, export and enter in pulse-width modulation (PWM) generator of inverter.Inner ring current controller G _innerexpression formula as follows:

G _inner(s)＝K _pi

Wherein, K _pifor proportional gain.

The implementation method of electric current optimal control policy comprises:

(1) identical with the step (1) of voltage method for optimally controlling;

(2) with reference to voltage V _dGwith filter capacitor voltage V _cerror input fundamental voltage control device G relatively _fV, with reference to harmonic current I _dG=0 with filter inductance electric current I ₂error input harmonic current controller G relatively _hC, G _fVand G _hCexporting adds up obtains reference current I _dG.Fundamental voltage control device G _fVexpression formula as follows:

$G_{FV}\left(s\right)=K_{pv}+\frac{K_{iv}}{s}$

Wherein, K _pv, K _ivbe respectively proportional gain and storage gain.Harmonic current controller G _hCexpression formula as follows:

$G_{HC}\left(s\right)=\underset{h=2,6,\mathrm{...}}{\Σ}\frac{K_{rih}{\mathrm{\ω}}_{ch}s}{s^2+2{\mathrm{\ω}}_{cih}s+{(\±h\·{\mathrm{\ω}}_s)}^2}$

Wherein, K _rihfor harmonic frequency ± h ω _sthe resonance gain at place, ω _cihfor harmonic frequency ± h ω _sthe cut-off frequency at place, ω _sfor first-harmonic angular frequency, h is harmonic number.Harmonic current controller G _hCmiddle harmonic number h gets 2,6,8,12,14.

(3) identical with the step (3) of voltage method for optimally controlling;

The implementation method of current compensation control strategy comprises:

(1) identical with the step (1) of voltage method for optimally controlling;

(2) with reference to voltage V _dGwith filter capacitor voltage V _cerror input fundamental voltage control device G relatively _fV, with reference to harmonic current I _dG=I _localwith filter inductance electric current I ₂error input harmonic current controller G relatively _hC, G _fVand G _hCexporting adds up obtains reference current I _dG.Fundamental voltage control device G _fVexpression formula as follows:

$G_{FV}\left(s\right)=K_{pv}+\frac{K_{iv}}{s}$

Wherein, K _pv, K _ivbe respectively proportional gain and storage gain.Harmonic current controller G _hCexpression formula as follows:

$G_{HC}\left(s\right)=\underset{h=2,6,\mathrm{...}}{\Σ}\frac{K_{rih}{\mathrm{\ω}}_{ch}s}{s^2+2{\mathrm{\ω}}_{cih}s+{(\±h\·{\mathrm{\ω}}_s)}^2}$

Wherein, K _rihfor harmonic frequency ± h ω _sthe resonance gain at place, ω _cihfor harmonic frequency ± h ω _sthe cut-off frequency at place, ω _sfor first-harmonic angular frequency, h is harmonic number.Harmonic current controller G _hCmiddle harmonic number h gets 2,6,8,12,14.

(3) identical with the step (3) of voltage method for optimally controlling;

When micro-capacitance sensor islet operation, ensure the stable of direct voltage, reduction DC bus-bar voltage imbalance and harmonic distortion are primary control objectives.Therefore, each distributed electrical source inventer in micro-capacitance sensor all gathers the electric current I at its access point place separately _local, and calculating current degree of unbalance and current distortion degree.Current distortion degree HF is the value added up to 3 to 15 subharmonic after carrying out fast Fourier transform (FFT) to electric current, generally gets degree of unbalance threshold value HF=0.3; Computing formula to degree of unbalance UF:

$UF=\frac{\sqrt{{\left(I_{localD}^{-}\right)}^2+{\left(I_{localQ}^{-}\right)}^2}}{\sqrt{{\left(I_{localD}^{+}\right)}^2+{\left(I_{localQ}^{+}\right)}^2}}\×100\%$

Wherein, be respectively I _localnegative sequence component rotating coordinate transformation after D axle component and Q axle component; be respectively I _localpositive sequence component rotating coordinate transformation after D axle component and Q axle component.Generally get degree of distortion threshold value UF=0.2.

When micro-capacitance sensor islet operation, ensure the stable of busbar voltage, reduction busbar voltage imbalance and harmonic distortion are primary control objectives.Therefore, each distributed electrical source inventer in micro-capacitance sensor all gathers the electric current I at its access point place separately _local, and calculating current degree of unbalance and current distortion degree.When access point current unbalance factor or the degree of distortion are less than setting threshold, distributed electrical source inventer adopts voltage optimal control policy, improves the quality of voltage of ac bus; When current unbalance factor or the degree of distortion are greater than setting threshold, distributed electrical source inventer adopts current compensation control strategy, and compensating non-linear load or unbalanced load are on the impact of the ac bus quality of power supply.When micro-grid connection is run, the quality of power supply that raising micro-capacitance sensor and bulk power grid exchange, reduces bus current imbalance and harmonic distortion is primary control objectives.When access point current unbalance factor or the degree of distortion are less than setting threshold, distributed electrical source inventer adopts electric current optimal control policy, improves the current quality of ac bus; When current unbalance factor or the degree of distortion are greater than setting threshold, distributed electrical source inventer adopts current compensation control strategy, and compensating non-linear load or unbalanced load are on the impact of the ac bus quality of power supply.

Voltage optimal control policy, electric current optimal control policy are identical in the control structure at fundamental frequency place with current compensation control strategy, just select different controllers at high-frequency harmonic place, therefore the switching of control strategy does not affect micro-capacitance sensor transient process, can realize taking over seamlessly between control strategy.

Cardinal principle of the present invention is:

This invention proposes three kinds of micro-capacitance sensor distributed power source control strategy for inverters based on pi controller+resonant controller, voltage optimal control policy can improve the quality of inverter output voltage, electric current optimal control policy can improve the quality of inverter output current, current compensation control strategy can compensate the current harmonics of access point, three kinds of control strategies can compensate the harmonic wave of unbalanced load and nonlinear load generation simultaneously, and the structure chart of three kinds of control strategies as shown in Figure 1.

Micro-capacitance sensor distributed electrical source inventer automatically gathers the electric current at incoming transport bus place and calculates degree of unbalance and the degree of distortion, the operational mode different according to micro-capacitance sensor, automatically switch corresponding control strategy, micro-capacitance sensor islet operation pattern and the harmonic wave on the ac bus under the pattern that is incorporated into the power networks and imbalance can be compensated simultaneously, improve the quality that micro-capacitance sensor and bulk power grid exchange electric energy, make micro-capacitance sensor grid-connected with island mode under all can meet the requirement of international standard to the quality of power supply.

Specific embodiment of the invention scheme is:

The micro-capacitance sensor of the present invention by reference to the accompanying drawings containing many distributed power sources shown in 2 is described a kind of method improving the micro-capacitance sensor ac bus quality of power supply.DG1, DG2, DG3, DG4 distributed plant-grid connection micro-capacitance sensor ac bus in micro-capacitance sensor in figure, the load of isochrone sexual balance, nonlinear load, three-phase imbalance load have also accessed the diverse location of micro-capacitance sensor ac bus.Wherein, nonlinear load adopts rectifier load, and three-phase balancing load adopts RLC load (resistance+inductance+electric capacity), and three-phase imbalance load adopts the RLC load of single-phase short circuit.

When static switch disconnects, micro-capacitance sensor islet operation.Ensure the stable of busbar voltage, reduction busbar voltage imbalance and harmonic distortion are primary control objectives.Therefore, each distributed electrical source inventer in micro-capacitance sensor all gathers the electric current I at its access point place separately _local, and calculating current degree of unbalance UF and current distortion degree HF.The HU of distributed power source DG1 is greater than setting threshold 0.3, and therefore the inverter of DG1 adopts current compensation control strategy, reduces nonlinear load to the impact of ac bus; The HF of distributed power source DG2 is less than setting threshold 0.3, UF and is less than setting threshold 0.2, and therefore the inverter of DG2 adopts voltage optimal control policy, improves busbar voltage quality; The HF of distributed power source DG3 is less than setting threshold 0.3, UF and is less than setting threshold 0.2, and therefore the inverter of DG3 adopts voltage optimal control policy, improves busbar voltage quality; The UF of distributed power source DG4 is greater than setting threshold 0.2, and therefore the inverter of DG4 adopts current compensation control strategy, reduces unbalanced load to the impact of ac bus.Adopt before and after this method, as shown in Figure 3, the voltage and current waveform at micro-capacitance sensor bus place obtains obvious improvement to the wave form varies that in micro-capacitance sensor, distributed power source runs.

When static switch closes, micro-grid connection is run.The quality of power supply that raising micro-capacitance sensor and bulk power grid exchange, reduces DC bus current imbalance and harmonic distortion is primary control objectives.Therefore, each distributed electrical source inventer in micro-capacitance sensor all gathers the electric current I at its access point place separately _local, and calculating current degree of unbalance UF and current distortion degree HF.The HU of distributed power source DG1 is greater than setting threshold 0.3, and therefore the inverter of DG1 adopts current compensation control strategy, reduces nonlinear load to the impact of ac bus; The HF of distributed power source DG2 is less than setting threshold 0.3, UF and is less than setting threshold 0.2, and therefore the inverter of DG2 adopts electric current optimal control policy, improves bus current quality; The HF of distributed power source DG3 is less than setting threshold 0.3, UF and is less than setting threshold 0.2, and therefore the inverter of DG3 adopts electric current optimal control policy, improves bus current quality; The UF of distributed power source DG4 is greater than setting threshold 0.2, and therefore the inverter of DG4 adopts current compensation control strategy, reduces unbalanced load to the impact of ac bus.Adopt before this method, the wave form varies that in micro-capacitance sensor, distributed power source runs as shown in Figure 4, wherein during 1s micro-capacitance sensor again islet operation pattern transfer the pattern of being incorporated into the power networks to.Adopt after this method, the wave form varies that in micro-capacitance sensor, distributed power source runs as shown in Figure 5, wherein during 1s micro-capacitance sensor again islet operation pattern transfer the pattern of being incorporated into the power networks to.The voltage and current waveform at micro-capacitance sensor bus place obtains obvious improvement.

It can also be seen that from Fig. 5, the switching of voltage optimal control policy, electric current optimal control policy and current compensation control strategy does not affect micro-capacitance sensor transient process, can realize taking over seamlessly between control strategy.

By reference to the accompanying drawings the specific embodiment of the present invention is described although above-mentioned; but not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme of the present invention, those skilled in the art do not need to pay various amendment or distortion that creative work can make still within protection scope of the present invention.

Claims (10)

1. improve a control method for the micro-capacitance sensor ac bus quality of power supply, it is characterized in that: comprise the following steps:

(1) gather micro-capacitance sensor distributed electrical source inventer filter capacitor voltage and and filter inductance electric current, calculate meritorious and reactive power, obtain reference voltage, according to microgrid operational mode, select a control strategy in step (2)-(4) to regulate;

(2) carry out voltage optimal control, carry out fundamental voltage control and harmonic voltage control with reference to the error after voltage and filter capacitor voltage compare, export after adding up and obtain reference current;

(3) carry out electric current optimal control, carry out fundamental voltage control, with reference to harmonic current I with reference to the error after voltage and filter capacitor voltage compare _dG=0 with filter inductance current ratio comparatively after error carry out harmonic current control, both control, and result is cumulative obtains reference current;

(4) carry out current compensation control, carry out fundamental voltage control, with reference to harmonic current I with reference to the error after voltage and filter capacitor voltage compare _dG=I _localwith filter inductance current ratio comparatively after error carry out harmonic current control, both control, and result is cumulative obtains reference current;

(5) make comparisons with reference to electric current and inverter output current, and carry out inner ring Current Control, carry out pulse-width modulation generation.

2. a kind of control method improving the micro-capacitance sensor ac bus quality of power supply as claimed in claim 1, is characterized in that: the concrete grammar of described step (1) is:

The filter capacitor voltage V of sampling micro-capacitance sensor distributed electrical source inventer _cwith filter inductance electric current I ₂calculate active-power P _lPFand reactive power Q _lPF, input power controller obtains reference voltage V _dG, the expression formula of power controller is as follows:

ω _DG＝ω ^*+m(P _rated-P _LPF)

E _DG＝E ^*+n(Q _rated-Q _LPF)

V _DG＝E _DGcosω _DGt

Wherein, ω ^*for reference angle frequency, E ^*for reference voltage amplitude, m is the sagging coefficient of active power, and n is the sagging coefficient of reactive power, P _ratedfor the specified active power of inverter, Q _ratedfor the rated reactive power of inverter.

3. a kind of control method improving the micro-capacitance sensor ac bus quality of power supply as claimed in claim 1, it is characterized in that: when micro-capacitance sensor islet operation, when access point current unbalance factor or the degree of distortion are less than setting threshold, distributed electrical source inventer adopts voltage optimal control policy, improves the quality of voltage of ac bus; When current unbalance factor or the degree of distortion are greater than setting threshold, distributed electrical source inventer adopts current compensation control strategy, and compensating non-linear load or unbalanced load are on the impact of the ac bus quality of power supply.

4. a kind of control method improving the micro-capacitance sensor ac bus quality of power supply as claimed in claim 1, it is characterized in that: when micro-grid connection is run, if when access point current unbalance factor or the degree of distortion are less than setting threshold, distributed electrical source inventer adopts electric current optimal control policy, improves the current quality of ac bus; When current unbalance factor or the degree of distortion are greater than setting threshold, distributed electrical source inventer adopts current compensation control strategy, and compensating non-linear load or unbalanced load are on the impact of the ac bus quality of power supply.

5. a kind of control method improving the micro-capacitance sensor ac bus quality of power supply as claimed in claim 1, is characterized in that: the concrete grammar of described step (2) comprising:

With reference to voltage V _dGwith filter capacitor voltage V _cerror input fundamental voltage control device G relatively _fVwith harmonic voltage controller G _hV, exporting adds up obtains reference current I _dG, fundamental voltage control device G _fVexpression formula as follows:

$G_{FV}\left(s\right)=K_{pv}+\frac{K_{iv}}{s}$

Wherein, K _pv, K _ivbe respectively proportional gain and storage gain, harmonic voltage control device G _hVexpression formula as follows:

$G_{HV}\left(s\right)=\underset{h=2,6,...}{\Σ}\frac{K_{rvh}{\mathrm{\ω}}_{cvh}s}{s^2+2{\mathrm{\ω}}_{cvh}s+{(\±h\·{\mathrm{\ω}}_s)}^2}$

Wherein, K _rvhfor harmonic frequency ± h ω _sthe resonance gain at place, ω _cvhfor harmonic frequency ± h ω _sthe cut-off frequency at place, ω _sfor first-harmonic angular frequency, h is harmonic number.

6. a kind of control method improving the micro-capacitance sensor ac bus quality of power supply as claimed in claim 1, is characterized in that: in described step (3), with reference to voltage V _dGwith filter capacitor voltage V _cerror input fundamental voltage control device G relatively _fV, with reference to harmonic current I _dG=0 with filter inductance electric current I ₂error input harmonic current controller G relatively _hC, G _fVand G _hCexporting adds up obtains reference current I _dG, fundamental voltage control device G _fVexpression formula as follows:

$G_{FV}\left(s\right)=K_{pv}+\frac{K_{iv}}{s}$

Wherein, K _pv, K _ivbe respectively proportional gain and storage gain, harmonic current controller G _hCexpression formula as follows:

$G_{HC}\left(s\right)=\underset{h=2,6,...}{\Σ}\frac{K_{rih}{\mathrm{\ω}}_{ch}s}{s^2+2{\mathrm{\ω}}_{cih}s+{(\±h\·{\mathrm{\ω}}_s)}^2}$

Wherein, K _rihfor harmonic frequency ± h ω _sthe resonance gain at place, ω _cihfor harmonic frequency ± h ω _sthe cut-off frequency at place, ω _sfor first-harmonic angular frequency, h is harmonic number.

7. a kind of control method improving the micro-capacitance sensor ac bus quality of power supply as claimed in claim 1, is characterized in that: in described step (4), with reference to voltage V _dGwith filter capacitor voltage V _cerror input fundamental voltage control device G relatively _fV, with reference to harmonic current I _dG=I _localwith filter inductance electric current I ₂error input harmonic current controller G relatively _hC, G _fVand G _hCexporting adds up obtains reference current I _dG, fundamental voltage control device G _fVexpression formula as follows:

$G_{FV}\left(s\right)=K_{pv}+\frac{K_{iv}}{s}$

Wherein, K _pv, K _ivbe respectively proportional gain and storage gain, harmonic current controller G _hCexpression formula as follows:

$G_{HC}\left(s\right)=\underset{h=2,6,...}{\Σ}\frac{K_{rih}{\mathrm{\ω}}_{ch}s}{s^2+2{\mathrm{\ω}}_{cih}s+{(\±h\·{\mathrm{\ω}}_s)}^2}$

Wherein, K _rihfor harmonic frequency ± h ω _sthe resonance gain at place, ω _cihfor harmonic frequency ± h ω _sthe cut-off frequency at place, ω _sfor first-harmonic angular frequency, h is harmonic number.

8. a kind of control method improving the micro-capacitance sensor ac bus quality of power supply as claimed in claim 1, is characterized in that: in described step (5), reference current I _dGwith inverter output current I ₂error input inner ring current controller G relatively _inner, export and enter in the pulse-width modulation PWM generator of inverter, inner ring current controller G _innerexpression formula as follows:

G _inner(s)＝K _pi

Wherein, K _pifor proportional gain.

9. a kind of control method improving the micro-capacitance sensor ac bus quality of power supply as claimed in claim 1, is characterized in that: each distributed electrical source inventer in micro-capacitance sensor all gathers the electric current I at its access point place separately _local, and calculating current degree of unbalance and current distortion degree, current distortion degree HF is the value added up to multiple harmonic after carrying out fast Fourier transform to electric current.

10. a kind of control method improving the micro-capacitance sensor ac bus quality of power supply as claimed in claim 1, is characterized in that: the computing formula to degree of unbalance UF:

$UF=\frac{\sqrt{{\left(I_{localD}^{-}\right)}^2+{\left(I_{localQ}^{-}\right)}^2}}{\sqrt{{\left(I_{localD}^{+}\right)}^2+{\left(I_{localQ}^{+}\right)}^2}}\×100\%$

Wherein, be respectively I _localnegative sequence component rotating coordinate transformation after D axle component and Q axle component; be respectively I _localpositive sequence component rotating coordinate transformation after D axle component and Q axle component.