CN103715704A - Micro electrical network common bus voltage imbalance inhibition method - Google Patents

Abstract

The invention belongs to the distributed power source control technology field in a micro electrical network system and relates to a micro electrical network common bus voltage imbalance inhibition method. According to the method, direct compensation for bus negative phase-sequence voltage at a PPC node in the micro electrical network system is carried out, each distributed power source in the micro electrical network can automatically respond to bus voltage imbalance degree at the PPC node in the micro electrical network system, adaptive adjustment of a negative phase-sequence voltage compensation controller (UVC) is carried out, so each distributed power source carries out negative phase-sequence wattless output according to the rated negative phase-sequence wattless capacity to maintain the voltage balance degree of the bus at the PCC node. Through the method, the parallel distributed power sources in the micro electrical network are enabled to have a function of imbalance voltage inhibition in the micro electrical network.

Description

A kind of micro-electrical network common bus Voltage unbalance inhibition method

Technical field

The invention belongs to distributed power source control technology field in micro-grid system, relate to a kind of common bus Voltage unbalance inhibition method based on the parallel connection of many distributed power sources.

Background technology

Being widely used of grid-connected power generation system, makes based on multiple distributed power source, and the micro-grid system of load and energy storage device becomes the elementary cell of intelligent grid.Micro-grid system is generally low-pressure system, and in low-pressure system, single-phase load is extensively to exist, and has caused the asymmetric of three-phase inverter three-phase output voltage, thereby has caused larger energy loss, affects the stability of micro-grid system.Therefore, must take measures to be suppressed, guarantee that distributed power source keeps the relative equilibrium of output voltage under unbalanced load.

IEEE and IEC have all made clear and definite regulation to the definition of Voltage unbalance degree, maximum permissible value etc. ^[1].In standard GB/T/T15543-2008 < < quality of power supply imbalance of three-phase voltage > > that China State Bureau of Technical Supervision promulgates, stipulate, electric power system points of common connection (Point of Common Coupling, PCC) normal voltage degree of unbalance permissible value is 2%, must not surpass 4% in short-term ^[2].Therefore, micro-unbalanced source voltage compensation is of crucial importance.

The micro-unbalanced power supply voltage compensation of existing low pressure mainly contains two kinds of modes, and a kind of is by series connection electric energy regulator, injects negative sequence voltage realize to circuit; Another is to adopt electric energy regulator in parallel, by injecting negative-sequence current to circuit, realizes.The former due to cost is high and affect line parameter circuit value apply less, the latter when circuit occur serious when uneven its negative-sequence current that is input to system will increase fast, in the time of seriously, can, over the output limit of electric energy regulator, cause the accident.Moreover, these two kinds common imbalance compensation devices only drop into when Voltage unbalance occurs, and are inoperative when system is normally moved, and utilization rate of equipment and installations is low, and economic benefit is poor.

Distributed power sources a large amount of in micro-electrical network are by three-phase grid-connected inverter connecting system, therefore structure and the power quality adjusting device of its inverter are similar, and utilizing distributed power source in micro-electrical network to realize that Voltage unbalance suppresses is that a kind of cost-effective quality of voltage improves scheme.

List of references

Pillay?P,Manyage?M.Definitions?of?voltage?unbalance[J].IEEE?Power?Engineering?Review,2001,21(5):50-51.

CNS GB/T15543-2008: quality of power supply imbalance of three-phase voltage [S]. Beijing: China Standard Press, 2008.

Woods the new year, Duan Shanxu, Kang Yong, Chen Jian. the modeling of no control interconnection parallel UPS and the stability analysis [J] based on droop characteristic, controlled. Proceedings of the CSEE, 2004,24 (2), 34-39.

Bao Wei, Hu Xuehao, Li Guanghui, Bao Weiyu. the improvement droop control [J] based on virtual impedance in the micro-electrical network of self. protecting electrical power system and control, 2013,41 (16), 7-13.

Wang?X,Blaabjerg?F,Chen?Z.Synthesis?of?Variable?Harmonic?Impedance?in?Inverter-Interfaced?Distributed?Generation?Unit?for?Harmonic?Damping?Throughout?a?Distribution?Network[J].Industry?Applications,IEEE?Transactions?on,2012,48(4),1407-1417.

Summary of the invention

The object of the invention is to overcome the above-mentioned deficiency of prior art, provide a kind of and utilize the distributed power source in micro-electrical network to realize Voltage unbalance inhibition, is that a kind of cost-effective quality of voltage improves scheme.Technical scheme of the present invention is as follows:

A kind of micro-electrical network common bus Voltage unbalance inhibition method, it is characterized in that, the method is carried out direct compensation to micro-grid system PCC Nodes bus negative sequence voltage, each distributed power source in micro-electrical network can be from the variation of the micro-electrical network PCC of dynamic response Nodes busbar voltage degree of unbalance, self adaptation is adjusted negative sequence voltage compensating controller (UVC), make each distributed power source idle according to its specified negative phase-sequence reactive capability output negative phase-sequence, the balance of voltage degree that maintains PCC Nodes bus, comprises the following steps:

1) step 1, detects the positive sequence voltage of micro-electrical network PCC Nodes bus in real time and negative sequence voltage

calculate the real-time voltage degree of unbalance coefficient of micro-electrical network PCC Nodes bus

2) step 2, detects i distributed power source DG in micro-electrical network in real time _inegative phase-sequence output idle

3) step 3, works as VUB _pccwhile being greater than certain default percentage, drop into negative sequence voltage compensating controller (UVC): establish

rated voltage degree of unbalance coefficient for micro-electrical network points of common connection (PCC); n _ifor DG _ithe idle distribution coefficient of negative phase-sequence; k _efor Voltage unbalance degree error proportionality coefficient; k _p, k _ifor proportionality coefficient and the integral coefficient of PI control, DG _ithe negative sequence voltage penalty coefficient of UVC:

${\mathrm{VCR}}_i=(k_P+\frac{k_I}{s})\mathrm{\&Delta;}{\mathrm{VCR}}_i,$

Wherein, $\mathrm{\&Delta;}{\mathrm{VCR}}_i=k_e({\mathrm{VUB}}_{\mathrm{pcc}}-{\mathrm{VUB}}_{\mathrm{pcc}}^{*})-n_i{Q}_i^{-};$

4) step 4, by VCR _iwith DG _ithe negative sequence voltage of output multiplies each other and obtains DG _ithe reference value of negative sequence voltage compensation;

5) step 5, obtains DG _ithe reference value of negative sequence voltage compensation after, coordinate its positive sequence meritorious/frequency and REACTIVE POWER/VOLTAGE droop control, virtual impedance is controlled, synthetic DG _ithe reference voltage of control system, controls laggard horizontal pulse width modulated through electric current and voltage dicyclo.

The present invention is by changing the control system of the distributed power source accessing in micro-electrical network, make distributed power source in parallel in micro-electrical network there is the function that suppresses micro-unbalanced source voltage, each distributed power source is in parallel by transmission line separately, when carrying out the uneven inhibitory control of PCC Nodes busbar voltage between each distributed power source without signal transmssion line.Two independent targets of controlling have been realized: (1) has guaranteed the quality of voltage of micro-electrical network PCC Nodes bus simultaneously; (2) distributed power source in parallel is idle according to the negative phase-sequence of the specified negative sequence compensation capability distribution output of self.The method is not only applicable to the micro-grid system under the mode of being incorporated into the power networks, also be applicable to the micro-grid system of independent operating, strengthen the control ability of distributed power source to micro-grid voltage quality, improved the quality of voltage of micro-electrical network, realized economy and the stable operation of micro-electrical network.

Accompanying drawing explanation

Fig. 1 is the micro-grid system schematic diagram that contains a plurality of distributed power sources;

Fig. 2 is primary circuit structure and the control system structure of a distributed power source;

Fig. 3 is PSCAD simulation model schematic diagram;

Fig. 4 is PCC Nodes busbar voltage degree of unbalance change curve;

Fig. 5 is two idle curves of distributed power source output negative phase-sequence;

Fig. 6 is PCC voltage curve before negative sequence voltage compensating controller drops into;

Fig. 7 is PCC voltage curve after negative sequence voltage compensating controller drops into.

Embodiment

Below in conjunction with drawings and Examples, the present invention will be described.

Many distributed power sources of one embodiment of the invention parallel system comprises that several distributed power sources in parallel are connected on same micro-electrical network bus by PCC, and busbar voltage is 400V, as shown in Figure 1.Distributed power source comprises the micro-source of direct current, three-phase full-bridge inverter, LC filter circuit and control system.As shown in Figure 2, the control strategy of every distributed power source comprise positive sequence meritorious/frequency and REACTIVE POWER/VOLTAGE droop control, virtual impedance is controlled and Voltage unbalance inhibitory control.Gain merit/frequency of positive sequence and REACTIVE POWER/VOLTAGE droop control are guaranteed output voltage level and the power level of each distributed power source; Virtual impedance is controlled the control effect that guarantees gain merit/frequency of positive sequence and REACTIVE POWER/VOLTAGE droop control by additional impedance in distributed electrical source control system; Voltage unbalance inhibitory control detects the Voltage unbalance degree VUB at PCC place in real time _pcc, work as VUB _pccin the time of>=2%, start, the Voltage unbalance degree that each distributed power source maintains PCC place by quick adjustment maintains setting level.

1. the Voltage unbalance inhibition method of the many distributed power sources parallel connection in micro-electrical network, comprises the following steps:

(1) as shown in Figure 2, each distributed power source detects the positive sequence voltage of micro-electrical network PCC Nodes bus in real time

and negative sequence voltage

form the real-time voltage degree of unbalance constant of micro-electrical network PCC Nodes bus

1) the control system collection of distributed power source outlet voltage v _cabc=[v _cav _cbv _cc] ^twith outlet current i _cabc=[i _cai _cbi _cc] ^t.According to symmetrical component method, in three-phase circuit, any asymmetric three-phase voltage or electric current all can resolve into by symmetrical component method the component of three groups of three-phase symmetricals, i.e. positive sequence, negative phase-sequence and zero-sequence component.In phase three-wire three circuit, owing to there is no zero sequence path, therefore do not have zero-sequence current, and residual voltage also can be ignored on the impact of micro-grid system.From instantaneous symmetrical component method, instantaneous voltage positive sequence component and negative sequence component

can be expressed as,

$\left\{\begin{array}{c}{v}_{\mathrm{Cabc}}^{+}={\&lsqb;v_{\mathrm{Ca}}^{+}{v}_{\mathrm{Cb}}^{+}{v}_{\mathrm{Cc}}^{+}\&rsqb;}^T=T_{+}{\&lsqb;v_{\mathrm{Ca}}{v}_{\mathrm{Cb}}{v}_{\mathrm{Cc}}\&rsqb;}^T\\ v_{\mathrm{Cabc}}^{-}={\&lsqb;v_{\mathrm{Ca}}^{-}{v}_{\mathrm{Cb}}^{-}{v}_{\mathrm{Cc}}^{-}\&rsqb;}^T=T_{-}{\&lsqb;v_{\mathrm{Ca}}{v}_{\mathrm{Cb}}{v}_{\mathrm{Cc}}\&rsqb;}^T\end{array}\right.,$

Transient current positive sequence component and negative sequence component can be expressed as,

$\left\{\begin{array}{c}{i}_{\mathrm{Cabc}}^{+}={\&lsqb;i_{\mathrm{Ca}}^{+}{i}_{\mathrm{Cb}}^{+}{i}_{\mathrm{Cc}}^{+}\&rsqb;}^T=T_{+}{\&lsqb;i_{\mathrm{Ca}}{i}_{\mathrm{Cb}}{i}_{\mathrm{Cc}}\&rsqb;}^T\\ i_{\mathrm{Cabc}}^{-}={\&lsqb;i_{\mathrm{Ca}}^{-}{i}_{\mathrm{Cb}}^{-}{i}_{\mathrm{Cc}}^{-}\&rsqb;}^T=T_{-}{\&lsqb;i_{\mathrm{Ca}}{i}_{\mathrm{Cb}}{i}_{\mathrm{Cc}}\&rsqb;}^T\end{array}\right..$

Wherein $T_{+}=\frac{1}{3}\left[\begin{array}{ccc}1& a& a^2\\ a^2& 1& a\\ a& a^2& 1\end{array}\right],$ $T_{-}=\frac{1}{3}\left[\begin{array}{ccc}1& a^2& a\\ a& 1& a^2\\ a^2& a& 1\end{array}\right],$ And $a=e^{j\frac{2}{3}\mathrm{\&pi;}}.$

2) by abc → α β conversion, this output voltage and output current are converted into v _{c α β}and i _{c α β}:

$\left\{\begin{array}{c}{v}_{\mathrm{C\&alpha;\&beta;}}={\&lsqb;v_{\mathrm{C\&alpha;}}{v}_{\mathrm{C\&beta;}}\&rsqb;}^T=T_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}{\&lsqb;v_{\mathrm{Ca}}{v}_{\mathrm{Cb}}{v}_{\mathrm{Cc}}\&rsqb;}^T\\ i_{\mathrm{C\&alpha;\&beta;}}={\&lsqb;i_{\mathrm{C\&alpha;}}{i}_{\mathrm{C\&beta;}}\&rsqb;}^T=T_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}{\&lsqb;i_{\mathrm{Ca}}{i}_{\mathrm{Cb}}{i}_{\mathrm{Cc}}\&rsqb;}^T\end{array}\right.,$ Wherein $T_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}=\frac{2}{3}\left[\begin{array}{ccc}1& -1/2& -1/2\\ 0& \sqrt{3}/2& \sqrt{3}/2\end{array}\right].$

3) utilize v _{c α β}and i _{c α β}calculate respectively fundamental positive sequence output voltage

first-harmonic negative phase-sequence output voltage

fundamental positive sequence output current

first-harmonic negative phase-sequence output current

wherein,

$\left\{\begin{array}{c}{v}_{\mathrm{C\&alpha;\&beta;}}^{+}={\&lsqb;v_{\mathrm{C\&alpha;}}^{+}{v}_{\mathrm{C\&beta;}}^{+}\&rsqb;}^T=T_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}{v}_{\mathrm{Cabc}}^{+}=T_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}{T}_{+}{v}_{\mathrm{Cabc}}=T_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}{T}_{+}{T}_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}^T{v}_{\mathrm{C\&alpha;\&beta;}}\\ v_{\mathrm{C\&alpha;\&beta;}}^{-}={\&lsqb;v_{\mathrm{C\&alpha;}}^{-}{v}_{\mathrm{C\&beta;}}^{-}\&rsqb;}^T=T_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}{v}_{\mathrm{Cabc}}^{-}=T_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}{T}_{-}{v}_{\mathrm{Cabc}}=T_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}{T}_{-}{T}_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}^T{v}_{\mathrm{C\&alpha;\&beta;}}\end{array}\right.,$

$\left\{\begin{array}{c}{i}_{\mathrm{C\&alpha;\&beta;}}^{+}={\&lsqb;i_{\mathrm{C\&alpha;}}^{+}{i}_{\mathrm{C\&beta;}}^{+}\&rsqb;}^T=T_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}{i}_{\mathrm{Cabc}}^{+}=T_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}{T}_{+}{i}_{\mathrm{Cabc}}=T_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}{T}_{+}{T}_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}^T{i}_{\mathrm{C\&alpha;\&beta;}}\\ i_{\mathrm{C\&alpha;\&beta;}}^{-}={\&lsqb;i_{\mathrm{C\&alpha;}}^{-}{i}_{\mathrm{C\&beta;}}^{-}\&rsqb;}^T=T_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}{i}_{\mathrm{Cabc}}^{-}=T_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}{T}_{-}{i}_{\mathrm{Cabc}}=T_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}{T}_{-}{T}_{\mathrm{abc}\&RightArrow;\mathrm{\&alpha;\&beta;}}^T{i}_{\mathrm{C\&alpha;\&beta;}}\end{array}\right..$

4) positive sequence voltage of PCC Nodes bus $V_{\mathrm{pcc}}^{+}=\sqrt{{\left(v_{\mathrm{C\&alpha;}}^{+}\right)}^2+{\left(v_{\mathrm{C\&beta;}}^{+}\right)}^2}$ , negative sequence voltage $V_{\mathrm{pcc}}^{-}=\sqrt{{\left(v_{\mathrm{C\&alpha;}}^{-}\right)}^2+{\left(v_{\mathrm{C\&beta;}}^{-}\right)}^2}$ 。The real-time voltage degree of unbalance coefficient of micro-electrical network PCC Nodes bus

(2) detect in real time i distributed power source DG in micro-electrical network _inegative phase-sequence output idle

$Q_i^{-}=v_{\mathrm{C\&alpha;}}^{-}{i}_{\mathrm{C\&beta;}}^{-}-v_{\mathrm{C\&beta;}}^{-}{i}_{\mathrm{C\&alpha;}}^{-}.$

(3) work as VUB _pccin the time of>=2%, drop into UVC.If

rated voltage degree of unbalance coefficient for micro-electrical network PCC Nodes bus; n _ifor DG _ithe idle distribution coefficient of negative phase-sequence; k _efor Voltage unbalance degree error proportionality coefficient; k _p, k _iproportionality coefficient and integral coefficient for PI control.DG _ithe negative sequence voltage penalty coefficient of UVC:

${\mathrm{VCR}}_i=(k_P+\frac{k_I}{s})\mathrm{\&Delta;}{\mathrm{VCR}}_i,$ Wherein $\mathrm{\&Delta;}{\mathrm{VCR}}_i=k_e({\mathrm{VUB}}_{\mathrm{pcc}}-{\mathrm{VUB}}_{\mathrm{pcc}}^{*})-n_i{Q}_i^{-}.$

When system enters stable state, vUB due to each DG _pccwith

corresponding same PCC node, and k _efor fixed constant, therefore

(subscript i, j represents respectively two distributed power source DG different in micro-electrical network _iand DG _j), according to DG _ispecified negative phase-sequence reactive capability n is set _i, any two different distributed power sources will be according to the proportional output negative phase-sequence of specified negative phase-sequence reactive capability is idle separately.

(4) by the VCR calculating in step (3) _iwith DG _ithe negative sequence voltage of output multiply each other obtain negative sequence voltage compensation reference value (by VCR _iwith DG _ithe negative sequence voltage of output multiplies each other and guarantees DG _ithe reference value of negative sequence voltage compensation consistent with the phase place of the actual negative sequence voltage of micro-grid system PCC Nodes bus):

$v_{\mathrm{C\&alpha;\&beta;}}^{-*}={\mathrm{VCR}}_i\&CenterDot;v_{\mathrm{C\&alpha;\&beta;}}^{-}.$

(5) obtain after the reference value of negative sequence voltage compensation, coordinate positive sequence to gain merit/frequency and REACTIVE POWER/VOLTAGE droop control [3], virtual impedance is controlled [4], and the reference voltage of synthetic inverter, through interior loop voltag double current loop modulation ^[5]laggard horizontal pulse width modulated.

1) positive sequence of gain merit/frequency of positive sequence and REACTIVE POWER/VOLTAGE droop control is meritorious with the idle method for solving of positive sequence is:

$\left\{\begin{array}{c}{P}_i^{+}=v_{\mathrm{C\&alpha;}}^{+}{i}_{\mathrm{C\&alpha;}}^{+}+v_{\mathrm{C\&beta;}}^{+}{i}_{\mathrm{C\&beta;}}^{+}\\ Q_i^{+}=v_{\mathrm{C\&alpha;}}^{+}{i}_{\mathrm{C\&beta;}}^{+}-v_{\mathrm{C\&beta;}}^{+}{i}_{\mathrm{C\&alpha;}}^{+}\end{array}\right..$

Obtained the meritorious and positive sequence of positive sequence idle after, the control method of meritorious/frequency and REACTIVE POWER/VOLTAGE droop control is:

$\left\{\begin{array}{c}{\mathrm{\&omega;}}_i^{*}={\mathrm{\&omega;}}_0-m_{\mathrm{pi}}{P}_i^{+}\\ E_i^{*}=E_0-n_{\mathrm{qi}}{Q}_i^{+}\end{array}\right.,$

Wherein,

reference value and amplitude reference value for DGi output positive sequence voltage; ω ₀and E ₀for DG _irated frequency and rated voltage amplitude; m _piand n _qibe respectively meritorious and idle sagging coefficient.Obtained DG _ithe reference value of output positive sequence voltage

with amplitude reference value after, by abc → α β conversion, obtain DG _ithe reference value of output positive sequence voltage

2) virtual impedance is controlled by additional impedance in distributed electrical source control system and is guaranteed the control effect that positive sequence voltage, frequency droop are controlled, and its control method is:

$\left\{\begin{array}{c}{v}_{\mathrm{Cf\&alpha;}}=i_{\mathrm{C\&alpha;}}{R}_{\mathrm{vi}}-i_{\mathrm{C\&beta;}}{\mathrm{\&omega;}}_i^{*}{L}_{\mathrm{fi}}\\ v_{\mathrm{Cf\&beta;}}=i_{\mathrm{C\&beta;}}{R}_{\mathrm{vi}}+i_{\mathrm{C\&alpha;}}{\mathrm{\&omega;}}_i^{*}{L}_{\mathrm{fi}}\end{array}\right.,$

Wherein, v _{cf α β}=[v _{cf α}v _{cf β}] ^tfor the output reference value that virtual impedance is controlled, R _viand L _fifor equivalent output resistance and the outputting inductance value fictionalizing in controlling unit.

3) positive sequence of comprehensive every distributed power source is gained merit/frequency and REACTIVE POWER/VOLTAGE droop control, and virtual impedance is controlled and Voltage unbalance inhibitory control, obtains the input reference of outer voltage

$U_{\mathrm{\&alpha;\&beta;}}^{*}=v_{\mathrm{C\&alpha;\&beta;}}^{+*}-v_{\mathrm{Cf\&alpha;\&beta;}}-v_{\mathrm{C\&alpha;\&beta;}}^{-*}.$

4) electric current and voltage dicyclo is controlled and has been adopted ratio resonant controller (PR),

and v _{c α β}by PR controller, obtain the current reference value under static coordinate

deduct i _{l α β}, through PR controller, obtain the PWM control inputs signal U under rest frame _{pWM α β}; U _{pWM α β}through α β → abc, conversion obtains the PWM control inputs signal U under three phase coordinate systems _pWMabc, input value PWM generation unit carries out pulse width modulation.The transfer function that PR controls is:

$G\left(s\right)=k_{\mathrm{PRp}}+\frac{{2k}_{\mathrm{PRr}}{\mathrm{\&omega;}}_{c}s}{s^2+{2\mathrm{\&omega;}}_{c}s+{\left({\mathrm{\&omega;}}_i^{*}\right)}^{2}s},$

Wherein, k _pRpand k _pRrrespectively proportionality coefficient and the resonance gain that PR controls, ω _cfor cut-off frequency.

2. in order to verify the correctness of institute of the present invention extracting method, with reference to Fig. 3, on PSCAD emulation platform, built the micro-grid system that contains two distributed power sources, system voltage is 400V, load is one and is connected on the 10 Ω resistance between mutually of A phase and B on PCC bus, and degree of unbalance is 2.5%.The system parameters of two distributed power sources is identical, controls parameter and loading condition as shown in table 1.At t=0.5, during second, add negative sequence voltage compensating controller.Carrier frequency is made as 12.8kHz.As seen from the figure, after adding negative sequence voltage compensating controller, Voltage unbalance degree is reduced to the idle ratio of negative phase-sequence of 1.6%, two distributed power source output contrary with the ratio of the idle distribution coefficient of negative phase-sequence, proved the validity of institute of the present invention extracting method.Table 1 control system parameter:

Claims (2)

1. a micro-electrical network common bus Voltage unbalance inhibition method, it is characterized in that, the method is located bus negative sequence voltage to micro-grid system points of common connection (PCC) and is carried out direct compensation, each distributed power source in micro-electrical network can be located from the micro-electrical network points of common connection of dynamic response (PCC) variation of busbar voltage degree of unbalance, self adaptation is adjusted negative sequence voltage compensating controller (UVC), make each distributed power source idle according to its specified negative phase-sequence reactive capability output negative phase-sequence, the balance of voltage degree that maintains PCC Nodes bus, comprises the following steps:

1) step 1, detects the positive sequence voltage of micro-electrical network PCC Nodes bus in real time

and negative sequence voltage

calculate the real-time voltage degree of unbalance coefficient of micro-electrical network PCC Nodes bus

2) step 2, detects i distributed power source DG in micro-electrical network in real time _inegative phase-sequence output idle

3) step 3, works as VUB _pccwhile being greater than certain default percentage, drop into negative sequence voltage compensating controller (UVC): establish

rated voltage degree of unbalance coefficient for micro-electrical network PCC Nodes bus; n _ifor DG _ithe idle distribution coefficient of negative phase-sequence; k _efor Voltage unbalance degree error proportionality coefficient; k _p, k _ifor proportionality coefficient and the integral coefficient of PI control, DG _ithe negative sequence voltage penalty coefficient of UVC:

${\mathrm{VCR}}_i=(k_P+\frac{k_I}{s})\mathrm{\&Delta;}{\mathrm{VCR}}_i,$

Wherein, $\mathrm{\&Delta;}{\mathrm{VCR}}_i=k_e({\mathrm{VUB}}_{\mathrm{pcc}}-{\mathrm{VUB}}_{\mathrm{pcc}}^{*})-n_i{Q}_i^{-};$

4) step 4, by VCR _iwith DG _ithe negative sequence voltage of output multiplies each other and obtains DG _ithe reference value of negative sequence voltage compensation;

5) step 5, obtains DG _ithe reference value of negative sequence voltage compensation after, coordinate its positive sequence meritorious/frequency and REACTIVE POWER/VOLTAGE droop control, virtual impedance is controlled, synthetic DG _ithe reference voltage of control system, controls laggard horizontal pulse width modulated through electric current and voltage dicyclo.

2. micro-electrical network common bus Voltage unbalance inhibition method according to claim 1, is characterized in that, works as VUB _pccin the time of>=2%, drop into negative sequence voltage compensating controller (UVC).

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