CN103645416B - A kind of microgrid non-destructive island detection method based on self-adaptation reactive disturbance - Google Patents

Abstract

The invention belongs to electric system micro-capacitance sensor protection and control field, relate to a kind of microgrid non-destructive island detection method based on self-adaptation reactive disturbance, comprise: the reactive disturbance of additional cycle in the reference value of the idle output of IBDG, the peak value value of triangular wave reactive disturbance part and the IBDG method of operation and in the upper disturbance cycle, reactive disturbance numerical value is zero time system frequency relevant; If detect, the absolute value of frequency change rate equals preset value, and the duration reaches time setting value, be then judged to be island state.The present invention is simple, and and can be down to minimum on the impact of the quality of power supply by disturbance total amount.

Description

A kind of microgrid non-destructive island detection method based on self-adaptation reactive disturbance

Art

The invention belongs to electric system micro-capacitance sensor protection and control field, relate to a kind of microgrid non-destructive island detection method.

Background technology

The appearance of the unplanned islet operation of micro-capacitance sensor has contingency and uncertainty, brings series of problems can to the safe and stable operation of electric system.In order to ensure the reliability and stability of powering, the distributed power source (DG) in micro-capacitance sensor needs can adjust its control strategy flexibly in time, thus makes micro-capacitance sensor be islet operation pattern by unplanned islet operation Mode change.Islanding detect is the prerequisite that DG adjusts its control strategy, and to the configuration protected in micro-capacitance sensor with coordinate important role.Existing island detection method comprises on off state monitoring method, passive detection method and active detecting method three major types.Wherein, on off state monitoring method sends to DG to judge the operational mode of micro-capacitance sensor the folding condition of power distribution network side isolating switch based on mechanics of communication, and the method does not exist check frequency, does not also affect the quality of power supply, but realize comparatively complicated, less economical.Whether passive detection method judges isolated island by detecting the basic electric parameters such as voltage, phase place, frequency and rate of change thereof within permission variation range, the method can not impact system power quality, but there is larger check frequency, usual and active detecting method R. concomitans.Active detecting method judges isolated island by introducing disturbing signal in the control signal of DG, this approach reduces check frequency, but also causes certain influence to the quality of power supply simultaneously.In addition, active detecting method needs to force the electric parameters such as voltage, frequency to exceed its threshold value usually, destroys micro-capacitance sensor normal table service condition, is unfavorable for conversion and the micro-capacitance sensor islet operation of DG control strategy.

Summary of the invention

The object of the invention is to overcome the deficiency that prior art destroys micro-capacitance sensor normal table service condition, provide a kind of island detection method that can not destroy micro-capacitance sensor islet operation condition.The method is based on the self-adaptation disturbance of the idle output of IBDG, simple, and and can be down to minimum on the impact of the quality of power supply by disturbance total amount.Substantive distinguishing features of the present invention is: by the reactive disturbance to the idle output additional cycle of IBDG, when there is unplanned isolated island in micro-capacitance sensor, system frequency still changes in allowed band, by detecting whether the absolute value of frequency change rate is setting value, thus realize microgrid non-destructive islanding detect.Technical scheme of the present invention is as follows:

Based on a microgrid non-destructive island detection method for self-adaptation reactive disturbance, comprise step below:

The first step: the reactive disturbance of additional cycle in the reference value of the idle output of IBDG, if T is the reactive disturbance cycle, Δ Q _magfor the peak value of triangular wave reactive disturbance part, then the reactive disturbance in the complete disturbance cycle is:

$\mathrm{\&Delta;}{Q}_{\mathrm{rao}}=\left\{\begin{array}{cc}\frac{\mathrm{\&Delta;}{Q}_{\mathrm{mag}}}{\frac{1}{3}T}t,& 0\&le;t<\frac{1}{3}T\\ \frac{\mathrm{\&Delta;}{Q}_{\mathrm{mag}}}{\frac{1}{3}T}(\frac{2}{3}T-t),& \frac{1}{3}T\&le;t<\frac{2}{3}\\ 0,& \frac{2}{3}T\&le;t<T\end{array}\right.$

Δ Q _magvalue and the IBDG method of operation and in the upper disturbance cycle, reactive disturbance numerical value is zero time system frequency relevant;

Second step: system frequency is more than or equal to 50Hz if detect, then when the sloping portion of triangular wave reactive disturbance starts, start the size of the absolute value detecting frequency change rate, until terminate the detection of frequency change rate absolute value at the end of triangular wave reactive disturbance rising part simultaneously simultaneously; If detect, system frequency is less than 50Hz, when the rising part of triangular wave reactive disturbance starts, start the size of the absolute value detecting frequency change rate, until terminate the detection of frequency change rate absolute value at the end of the sloping portion of triangular wave reactive disturbance simultaneously simultaneously;

3rd step: the absolute value of frequency change rate equals 1.5/T if detect ₁, and the duration reach time setting value t ^*, then island state is judged to be.Otherwise, be back to the first step, repeat above-mentioned testing process.

Preferably, in the first step,

If IBDG is that unity power factor is run under grid-connect mode, then the peak value of triangular wave reactive disturbance is:

$\mathrm{\&Delta;}{Q}_{\mathrm{mag}}=\left\{\begin{array}{c}{P}_{\mathrm{DG}}{Q}_f(\frac{f}{50.5}-\frac{50.5}{f}),f\&GreaterEqual;50\mathrm{Hz}\\ P_{\mathrm{DG}}{Q}_f(\frac{f}{49.5}-\frac{49.5}{f}),f<50\mathrm{Hz}\end{array}\right.$

If under grid-connect mode IBDG for local load provide idle but not unity power factor run, then the peak value of triangular wave reactive disturbance is:

$\mathrm{\&Delta;}{Q}_{\mathrm{mag}}=\left\{\begin{array}{c}{P}_{\mathrm{DG}}{Q}_f(f-50.5)(\frac{50}{50.5f}+\frac{1}{50}),f\&GreaterEqual;50\mathrm{Hz}\\ P_{\mathrm{DG}}{Q}_f(f-49.5)(\frac{50}{49.5f}+\frac{1}{50}),f<50\mathrm{Hz}\end{array}\right.$

Wherein P _dGwork value is had, Q for IBDG exports _ffor loaded quality factor, f was system frequency when reactive disturbance numerical value is zero in the upper disturbance cycle; In addition, reactive disturbance cycle T is the self-adaptative adjustment according to f numerical value also, and concrete numerical value is shown below:

$T=\left\{\begin{array}{c}\frac{50.5-f}{50.5-50}{T}_1,f\&GreaterEqual;50\mathrm{Hz}\\ \frac{f-49.5}{50-49.5}{T}_1,f<50\mathrm{Hz}\end{array}\right.$

Wherein, T ₁for the cycle of reactive disturbance when system frequency is 50Hz, while additional cycle reactive disturbance, T is set ₁numerical value and time setting value t ^*.

The present invention compared with prior art, propose a kind of microgrid non-destructive island detection method based on self-adaptation reactive disturbance, the good effect that the method can produce is: first, the present invention is by the reactive disturbance to the idle output additional cycle of IBDG, after unplanned isolated island is occurred, system frequency still changes in allowed band, by detecting whether frequency change rate is setting value and matching state duration whether reach setting valve to judge isolated island, micro-capacitance sensor islet operation condition can not be destroyed, for taking over seamlessly of IBDG control strategy provides advantage, secondly, system frequency when the present invention is zero according to reactive disturbance, the peak value of self-adaptative adjustment reactive disturbance and cycle, and can be down to minimum on the impact of the quality of power supply by disturbance total amount, finally, the present invention has versatility, has both been applicable to the IBDG that unity power factor is run, and is also applicable to the IBDG for local load provides the non-unity power factor of reactive-load compensation to run simultaneously.

Accompanying drawing explanation

Fig. 1 is standard isolated island test macro main circuit topology figure;

Fig. 2 is the PQ uneoupled control block diagram of IBDG;

Fig. 3 is after unplanned isolated island occurs when making system frequency be respectively 49.5Hz and 50.5Hz, the graph of a relation of system frequency and the required idle not amount of coupling before unplanned isolated island occurs;

Fig. 4 be unplanned isolated island occur after according to system frequency when reactive disturbance is zero in the upper disturbance cycle reactive disturbance figure in self-adaptative adjustment disturbance peak value and cycle and the frequency plot of correspondence thereof.

Fig. 5 is the process flow diagram of the microgrid non-destructive island detection method based on self-adaptation reactive disturbance.

Embodiment

Be described in detail below in conjunction with embodiment and with reference to the technical scheme of accompanying drawing to this invention.

The present invention can the idle control strategy of IBDG of self-adaptative adjustment reactive disturbance cycle and triangular wave disturbance peak value thereof by adopting, and provides a kind of micro-grid island detection method not destroying micro-capacitance sensor islet operation condition.The method and can be down to minimum on the impact of the quality of power supply by disturbance total amount, and is applicable to the IBDG that unity power factor is run and non-unity power factor is run simultaneously, ensure that non-destructive and the versatility of method.

1. for isolated island test macro and the PQ decoupling control policy of IBDG

According to the difference of the method for operation, distributed power source generally can be divided into tradition to rotate type DG and inverse type DG(IBDG).Wherein, IBDG is in parallel with electrical network by power electronic equipment, be the grid-connected principal mode of current DG, the standard isolated island test macro of the distributed power source specified in IEEEStd.929-2000 and IEEEStd.1547-2003 and combining inverter as shown in Figure 1 [1,2].Under the pattern of being incorporated into the power networks, IBDG is connected with power distribution network by point of common coupling (PCC), and simultaneously for load provides power, the relational expression between meritorious and the idle and load equivalent impedance of load consumption is respectively:

$P_{\mathrm{Load}}=P_{\mathrm{DG}}+P_{\mathrm{Grid}}=3\frac{V_{\mathrm{PCC}}^2}{R}---\left(1\right)$

$Q_{\mathrm{Load}}=Q_{\mathrm{DG}}+Q_{\mathrm{Grid}}=3V_{\mathrm{PCC}}^2(\frac{1}{2\mathrm{\&pi;}{f}^{*}L}-2\mathrm{\&pi;}{f}^{*}C)---\left(2\right)$

Wherein V _pCCfor the voltage at PCC place, f ^*for the frequency of PCC place voltage time grid-connected.When shown in Fig. 1 during switch opens, IBDG and load form isolated island, and needed for load, electric energy is provided by IBDG completely.When there is unplanned isolated island, if the power that IBDG provides equals or close to the power required for load consumption, then PCC place voltage and frequency will be run within allowed band normal, passive detection method overvoltage/under-voltage method (OVP/UVP) and overfrequency/under-frequency method (OFP/UFP) cannot detect the generation of unplanned isolated island, thus enter check frequency.

Based on instantaneous power theory, IBDG adopts PQ decoupling control policy, thus can realize non-destructive islanding detect by the idle control strategy by IBDG.The control block diagram of PQ decoupling control policy as shown in Figure 2, comprises phaselocked loop, power outer shroud and current inner loop [3,4].By introducing the three-phase voltage at PCC place, phaselocked loop can provide the voltage phase angle realizing synchronous Park Transformation, and can calculate the frequency of PCC place voltage.In power outer shroud, by one group of proportional integral (PI) regulator, meritorious and between idle reference value and real power error is modulated to respectively the reference value of the meritorious of inverter output current and idle component.Current inner loop, then by feed-forward control algorithm, realizes the uneoupled control to the meritorious of inverter output current and idle component.The formula of the active power that inverter exports and reactive power is as follows:

$P_{\mathrm{DG}}=\frac{3}{2}{u}_d{i}_d---\left(3\right)$

$Q_{\mathrm{DG}}=\frac{3}{2}{u}_d{i}_q---\left(4\right)$

From above-mentioned two formula, by the adjustment to the meritorious of output current and idle component, can realize controlling its meritorious and idle independence, and reach set value and power reference P _refand Q _ref[4,5].

The source of list of references involved in above-mentioned paragraph is as follows:

[1]IEEE Standard929-2000.IEEE Recommended Practice for Utility Interface of Photovoltaic(PV)Systems，2000.

[2]IEEE Standard1547-2003.IEEE Standard for Interconnecting Distributed Resources with Electric PowerSystems，2003.

[3] Tian little He, the control and scheduling co-design of light storage commingled system: [master thesis], Tianjin: University Of Tianjin, 2011.

[4]Zeineldin H.H.AQ-f droop curve for facilitating islanding detection of inverter-based distributedgeneration.IEEE Transactions on Power Electronics,2009,24(3):665-673.

[5]Schauder C,Mehta H.Vector analysis and control of advanced static VAR compensators.IEE ProceedingsC–Generation,Transmission and Distribution,1993,15(3):299-306.

2. based on the microgrid non-destructive island detection method of self-adaptation reactive disturbance

IBDG based on PQ uneoupled control can run with unity power factor or non-unity power factor.Under normal circumstances, IBDG exports idle reference value Q _refbe set as zero, namely IBDG runs according to unity power factor, to improve the operational efficiency of inverter to greatest extent.But, when load reactive requirement in PCC place is large or reactive power fluctuation time, grid-connected place voltage will be had a strong impact on.Therefore, by IBDG, reactive-load compensation is carried out to load, can reduce power distribution network to PCC place load provide idle, improve the power factor of load, reduce simultaneously conveying the idle voltage-drop caused.When there is unplanned isolated island, no matter IBDG runs according to unity power factor or runs according to non-unity power factor, if its power provided equals or close to the power required for load consumption, then PCC place voltage and frequency will be run within allowed band normal, OVP/UVP and OFP/UFP all cannot detect the generation of unplanned isolated island, thus enter check frequency.But after unplanned isolated island is detected, IBDG needs its control strategy of adjustment in time, such as controls to be converted to permanent Vf by permanent PQ and controls, thus voltage and frequency is provided to support, to realize micro-capacitance sensor islet operation for micro-capacitance sensor.Therefore, one must be explored there is nondestructive micro-grid island detection method, not only to the IBDG that unity power factor and non-unity power factor are run, there is versatility, eliminate check frequency, and system frequency still changes in allowed band after unplanned isolated island can be made to occur, thus provide advantage for taking over seamlessly of IBDG control strategy, while effectively judging isolated island, also can ensure micro-capacitance sensor stably islet operation.

When unplanned isolated island occurs, run if IBDG is unity power factor, then idle do not mate for unplanned isolated island occur before load consumption idle, be shown below:

$\mathrm{\&Delta;Q}=-3V_{\mathrm{PCC}}^2(\frac{1}{2\mathrm{\&pi;}{f}^{*}L}-2\mathrm{\&pi;}{f}^{*}C)=P_{\mathrm{DG}}{Q}_f(\frac{f^{*}}{f_0}-\frac{f_0}{f^{*}})---\left(5\right)$

Wherein f ^*for front system frequency occurs isolated island, f ₀for resonance frequency, Q _ffor load quality factor, be shown below:

$f_0=\frac{1}{2\mathrm{\&pi;}\sqrt{\mathrm{LC}}}---\left(6\right)$

$Q_f=R\sqrt{\frac{C}{L}}---\left(7\right)$

Because IBDG does not have idle output, therefore the final stationary value of rear system frequency occurs unplanned isolated island is resonance frequency f ₀.If this resonance frequency is within normal allowed band, then passive detection method OFP/UFP cannot detect isolated island.

When unplanned isolated island occurs, run if IBDG is non-unity power factor, then IBDG provides idle in whole or in part for local load.Now, load is idle to be provided by IBDG completely, the Q before being occurred by isolated island _loadbecome Q _dG, simultaneity factor frequency is by f ^*become f ^*, the load namely after reactive-load compensation is idle to be expressed from the next:

$Q_{\mathrm{DG}}=3V_{\mathrm{PCC}}^2(\frac{1}{2\mathrm{\&pi;}{f}^{**}L}-2\mathrm{\&pi;}{f^{**}}_{2}C)---\left(8\right)$

Idlely do not mate the change causing system frequency before and after unplanned isolated island, can be obtained by formula (2) and (8):

$\mathrm{\&Delta;Q}=Q_{\mathrm{DG}}-Q_{\mathrm{Load}}=3V_{\mathrm{PCC}}^2(\frac{1}{2\mathrm{\&pi;}{f}^{**}L}-2\mathrm{\&pi;}{f}^{**}C)-3V_{\mathrm{PCC}}^2(\frac{1}{2\mathrm{\&pi;}{f}^{*}L}-2\mathrm{\&pi;}{f}^{*}C)---\left(9\right)$

Through abbreviation, formula (9) can be expressed as:

$\mathrm{\&Delta;Q}=P_{\mathrm{DG}}{Q}_f(f^{*}-f^{**})(\frac{f_0}{f^{*}{f}^{**}}+\frac{1}{f_0})---\left(10\right)$

In formula (10), due to f ₀the numerical value impact of formula being set up when changing near system nominal frequency negligible, therefore can be taken as the numerical value 50 of system nominal frequency, namely formula (10) can be equivalent to further:

$\mathrm{\&Delta;Q}=P_{\mathrm{DG}}{Q}_f(f^{*}-f^{**})(\frac{50}{f^{*}{f}^{**}}+\frac{1}{50})---\left(11\right)$

The main target of non-destructive micro-grid island detection method, accurately detects isolated island exactly under the prerequisite not destroying micro-capacitance sensor isolated island stable operation condition.According to national grid standard regulation, the normal operation range of system frequency is 49.5Hz ~ 50.5Hz.According to IEEEStd.929-2000 standard regulation, load quality factor q _fbe no more than 2.5, can be taken as 2.5.If the active-power P that IBDG exports _dGbe 1, according to formula (5) and (11) known, if system frequency reaches normal operation range threshold value 49.5Hz or 50.5Hz after making unplanned isolated island, then unplanned isolated island occur before system frequency f ^*and required idlely do not mate relation between numerical value Δ Q as shown in Figure 3.As shown in Figure 3,1) f is worked as ^*when being less than 50Hz, with 49.5Hz for the target frequency after reactive-load compensation, and f should be worked as ^*when being more than or equal to 50Hz, should, with 50.5Hz for the target frequency after reactive-load compensation, required idle unmatched numerical value so just can be made less, ensure within the scope of ± 5%PDG; 2), after unplanned isolated island occurs, idlely do not mate and there is linear approximate relationship between caused frequency change.

Do not mate due to idle and there is linear approximate relationship between caused frequency change, therefore the system frequency after can utilizing idle triangular wave disturbance that unplanned isolated island is occurred also presents the change of triangle shape within normal allowed band, when idle triangular wave disturbance reaches peak value, corresponding system frequency is also changed to threshold value 49.5Hz or 50.5Hz of normal allowed band, thus detects isolated island under the prerequisite not destroying micro-capacitance sensor stable operation condition.In addition, after unplanned isolated island generation, the system frequency of different numerical value needs the reactive-load compensation of varying number to make it reach threshold value as shown in Figure 3, and system frequency may be any number in normal allowed band after isolated island, need the certainty annuity frequency when not additional reactive disturbance and reactive disturbance are zero, just can calculate the peak value of required idle triangular wave disturbance on this basis.Further, in order to and be down to minimum on the impact of the quality of power supply by reactive disturbance total amount, reactive disturbance needs can the peak value of its cycle of self-adaptative adjustment and triangular wave disturbance part.

Therefore, based on three parts that each reactive disturbance cycle is divided into the duration equal by the microgrid non-destructive island detection method of self-adaptation reactive disturbance.The front two parts in each reactive disturbance cycle are respectively rising edge and negative edge that initial value is the symmetric triangular ripple reactive disturbance of zero, and Part III is reactive disturbance numerical value perseverance is zero.The duration in each reactive disturbance cycle and the peak value of triangular wave disturbance part thereof, all determined according to system frequency when reactive disturbance numerical value is zero in the upper disturbance cycle, thus by total disturbance quantity and be down to minimum on the impact of the quality of power supply.When under grid-connect mode, IBDG unity power factor is run, from formula (5), the peak value of triangular wave reactive disturbance can calculate according to following formula:

$\mathrm{\&Delta;}{Q}_{\mathrm{mag}}=\left\{\begin{array}{c}{P}_{\mathrm{DG}}{Q}_f(\frac{f}{50.5}-\frac{50.5}{f}),f\&GreaterEqual;50\mathrm{Hz}\\ P_{\mathrm{DG}}{Q}_f(\frac{f}{49.5}-\frac{49.5}{f}),f<50\mathrm{Hz}\end{array}\right.---\left(12\right)$

When under grid-connect mode IBDG for local load provide idle but not unity power factor run time, from formula (11), the peak value of triangular wave reactive disturbance calculates according to following formula:

$\mathrm{\&Delta;}{Q}_{\mathrm{mag}}=\left\{\begin{array}{c}{P}_{\mathrm{DG}}{Q}_f(f-50.5)(\frac{50}{50.5}+\frac{1}{50}),f\&GreaterEqual;50\mathrm{Hz}\\ P_{\mathrm{DG}}{Q}_f(f-49.5)(\frac{50}{49.5}+\frac{1}{50}),f<50\mathrm{Hz}\end{array}\right.---\left(13\right)$

Wherein P _dGwork value is had, Q for IBDG exports _ffor loaded quality factor, f was system frequency when reactive disturbance numerical value is zero in the upper disturbance cycle, 50.5Hz and 49.5Hz Wei the threshold value of frequency normal operation range.Therefore, after the peak value of triangular wave reactive disturbance part was determined according to system frequency when reactive disturbance numerical value is zero in the upper disturbance cycle, the reactive disturbance in the complete disturbance cycle is shown below:

$\mathrm{\&Delta;}{Q}_{\mathrm{rao}}=\left\{\begin{array}{cc}\frac{\mathrm{\&Delta;}{Q}_{\mathrm{mag}}}{\frac{1}{3}T}t,& 0\&le;t<\frac{1}{3}T\\ \frac{\mathrm{\&Delta;}{Q}_{\mathrm{mag}}}{\frac{1}{3}T}(\frac{2}{3}T-t),& \frac{1}{3}T\&le;t<\frac{2}{3}T\\ 0,& \frac{2}{3}T\&le;t<T\end{array}\right.---\left(14\right)$

Wherein T is the reactive disturbance cycle.From formula (12), (13) and (14), when f is more than or equal to 50Hz, the front two parts in next reactive disturbance cycle present the triangle shape first declining and rise afterwards; When f is less than 50Hz, front two parts of next disturbance idle period present the triangle shape first rising and decline afterwards; When f changes, the peak value of next disturbance triangular wave idle period disturbance part is also different.In addition, determined the same with the peak value of triangular wave reactive disturbance by f, reactive disturbance cycle T is the self-adaptative adjustment according to f numerical value also, and concrete correction is shown below:

$T=\left\{\begin{array}{c}\frac{50.5-f}{50.5-50}{T}_1,f\&GreaterEqual;50\mathrm{Hz}\\ \frac{f-49.5}{50-49.5}{T}_1,f<50\mathrm{Hz}\end{array}\right.---\left(15\right)$

Wherein T ₁for the cycle of reactive disturbance when system frequency is 50Hz.Therefore, the system frequency f when reactive disturbance numerical value is zero in the upper disturbance cycle once determine, then the peak delta Q of next periodical triangular waveform reactive disturbance _magand the cycle T of whole reactive disturbance is also according to f numerical value and formula (12), (13) and (15) and determine, and all no longer change with the change of system frequency within this disturbance cycle.

When unplanned isolated island occurs, due to frequency change with idle do not mate between linear approximate relationship, then the change along with triangular wave reactive disturbance is also presented the change of triangle shape by system frequency, when f value is different, the cycle of self-adaptation reactive disturbance, the peak value of triangular wave disturbance part and the frequency change caused by disturbance are as shown in Figure 4.Concrete change procedure is: when upper a disturbance cycle, reactive disturbance was zero time system frequency be more than or equal to 50Hz time, then in this disturbance cycle, system frequency rises along with the decline of triangular wave reactive disturbance, through T/3 when triangular wave reactive disturbance is down to peak delta Q _magtime, system frequency rises to the threshold value 50.5Hz of frequency normal operation range, rising along with triangular wave reactive disturbance declines by system frequency afterwards, system frequency when reactive disturbance numerical value is zero is reduced to again through T/3 system frequency, if in the process, there is not removal of load or IBDG and go out fluctuation etc. and can cause the unmatched situation of new power in micro-capacitance sensor, then this value and in the upper disturbance cycle, reactive disturbance numerical value is zero time system frequency equal and opposite in direction.When upper a disturbance cycle, reactive disturbance was zero time system frequency be less than 50Hz time, under reactive disturbance system frequency change procedure and said process similar, difference is that first system frequency declines along with the rising of triangular wave reactive disturbance, until the threshold value 49.5Hz of frequency normal operation range, rise along with the decline of reactive disturbance more afterwards, until system frequency when reactive disturbance numerical value is zero.In above-mentioned change procedure, system frequency change cycle the same with the cycle of reactive disturbance, all along with upper a disturbance cycle, reactive disturbance was zero time system frequency and adaptive change.Therefore, no matter the negative edge of frequency triangular wave or the initial value (namely going up a system frequency when disturbance cycle, reactive disturbance was zero) of rising edge are the arbitrary numerical value in normal operation range, be that in the process of triangle shape change, the absolute value of frequency change rate is constant in frequency.The absolute value of frequency change rate equals 1.5/T ₁(Hz/s), with T ₁size relevant, work as T ₁value pre-set time, then the absolute value of frequency change rate is fixed value.

In sum, based on the microgrid non-destructive island detection method of self-adaptation reactive disturbance process flow diagram as shown in Figure 5, its concrete steps are as follows:

The first step: according to IBDG type, to the reference value additional cycle reactive disturbance of its idle output, the cycle of reactive disturbance and peak value are arranged as shown in formula (12), (13), (14) and (15), and set T ₁numerical value and time setting value t ^*;

Second step: system frequency is more than or equal to 50Hz if detect, then when the sloping portion of triangular wave reactive disturbance starts, start the size of the absolute value detecting frequency change rate, until terminate the detection of frequency change rate absolute value at the end of triangular wave reactive disturbance rising part simultaneously simultaneously; If detect, system frequency is less than 50Hz, when the rising part of triangular wave reactive disturbance starts, start the size of the absolute value detecting frequency change rate, until terminate the detection of frequency change rate absolute value at the end of the sloping portion of triangular wave reactive disturbance simultaneously simultaneously.

3rd step: the absolute value of frequency change rate equals 1.5/T if detect ₁, and the duration reach time setting value t ^*, then island state is judged to be.Otherwise, be back to the first step, repeat above-mentioned testing process.

The above-mentioned microgrid non-destructive island detection method based on self-adaptation reactive disturbance is by the disturbance to the idle output additional cycle of IBDG, after unplanned isolated island is occurred, system frequency still changes in allowed band, thus provide advantage for taking over seamlessly of IBDG control strategy, while effectively judging isolated island, also ensure that micro-capacitance sensor can stably islet operation.In addition, by the cycle of self-adaptative adjustment reactive disturbance and the peak value of triangular wave disturbance part, and can be down to minimum on the impact of the quality of power supply by disturbance total amount.Meanwhile, the present invention has versatility, has both been applicable to the IBDG that unity power factor is run, and is also applicable to as local load provides the IBDG of reactive-load compensation.

Above content is only embodiments of the invention, and its object is not for the restriction to system and method proposed by the invention, and protection scope of the present invention is as the criterion with claim.Without departing from the spirit and scope of the present invention; those skilled in the art are not when departing from scope and spirit of the present invention, and all apparent amendment about form and details carry out it or change all should drop within protection scope of the present invention.

Claims (1)

1., based on a microgrid non-destructive island detection method for self-adaptation reactive disturbance, comprise step below:

The first step: the reactive disturbance of additional cycle in the reference value of the idle output of IBDG, if T is the reactive disturbance cycle, Δ Q _magfor the peak value of triangular wave reactive disturbance part, then the reactive disturbance in the complete disturbance cycle is:

${\mathrm{\&Delta;Q}}_{\mathrm{rao}}=\left\{\begin{array}{cc}\frac{{\mathrm{\&Delta;Q}}_{\mathrm{mag}}}{\frac{1}{3}T}t,& 0\&le;t<\frac{1}{3}T\\ \frac{{\mathrm{\&Delta;Q}}_{\mathrm{mag}}}{\frac{1}{3}T}(\frac{2}{3}T-t),& \frac{1}{3}T\&le;t<\frac{2}{3}T\\ 0,& \frac{2}{3}T\&le;t<T\end{array}\right.$

Δ Q _magvalue and the IBDG method of operation and in the upper disturbance cycle, reactive disturbance numerical value is zero time system frequency relevant;

Second step: system frequency is more than or equal to 50Hz if detect, then when the sloping portion of triangular wave reactive disturbance starts, start the size of the absolute value detecting frequency change rate, until terminate the detection of frequency change rate absolute value at the end of triangular wave reactive disturbance rising part simultaneously simultaneously; If detect, system frequency is less than 50Hz, when the rising part of triangular wave reactive disturbance starts, start the size of the absolute value detecting frequency change rate, until terminate the detection of frequency change rate absolute value at the end of the sloping portion of triangular wave reactive disturbance simultaneously simultaneously;

3rd step: the absolute value of frequency change rate equals 1.5/T if detect ₁, and the duration reach time setting value t ^*, then island state is judged to be;

In the first step wherein,

If IBDG is that unity power factor is run under grid-connect mode, then the peak value of triangular wave reactive disturbance is:

${\mathrm{\&Delta;Q}}_{\mathrm{mag}}=\left\{\begin{array}{cc}{P}_{\mathrm{DG}}{Q}_f(\frac{f}{50.5}-\frac{50.5}{f}),& f\&GreaterEqual;50\mathrm{Hz}\\ P_{\mathrm{DG}}{Q}_f(\frac{f}{49.5}-\frac{49.5}{f}),& f<50\mathrm{Hz}\end{array}\right.$

If under grid-connect mode IBDG for local load provide idle but not unity power factor run, then the peak value of triangular wave reactive disturbance is:

${\mathrm{\&Delta;Q}}_{\mathrm{mag}}=\left\{\begin{array}{cc}{P}_{\mathrm{DG}}{Q}_f(f-50.5)(\frac{50}{50.5f}+\frac{1}{50}),& f\&GreaterEqual;50\mathrm{Hz}\\ P_{\mathrm{DG}}{Q}_f(f-49.5)(\frac{50}{49.5f}+\frac{1}{50}),& f<50\mathrm{Hz}\end{array}\right.$

Wherein P _dGwork value is had, Q for IBDG exports _ffor loaded quality factor, f was system frequency when reactive disturbance numerical value is zero in the upper disturbance cycle; In addition, reactive disturbance cycle T is the self-adaptative adjustment according to f numerical value also, and concrete numerical value is shown below:

$T=\left\{\begin{array}{cc}\frac{50.5-f}{50.5-50}{T}_1,& f\&GreaterEqual;50\mathrm{Hz}\\ \frac{f-49.5}{50-49.5}{T}_1,& f<50\mathrm{Hz}\end{array}\right.$

Wherein, T ₁for the cycle of reactive disturbance when system frequency is 50Hz, while additional cycle reactive disturbance, T is set ₁numerical value and time setting value t ^*.