CN105334390B - Outside suitable for multimachine assembly concentrates disturbance formula impedance measurement isolated island detection method - Google Patents
Outside suitable for multimachine assembly concentrates disturbance formula impedance measurement isolated island detection method Download PDFInfo
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Abstract
The present invention relates to Power System Analysis technical field, and disturbance formula impedance measurement isolated island detection method is concentrated suitable for the outside of multimachine assembly more particularly to a kind of, it is characterised in that：Disturbing generating device is concentrated first with separate outer, generates the current perturbation signal i of a certain size and waveformInj；Voltage u at monitoring system point of common couplingPCC, intermittent zero crossing injection control is carried out at system point of common coupling, while voltage u at acquisition system point of common coupling will be measured in injection processPCCWith current perturbation signal iInjData measured after data processing impedance characteristic amount calculating；Island state is differentiated according to Feature change.The present invention is applied to distributed power supply system containing multi-inverter, the power supply that synchronous generator etc. is free of inverter is also applied for simultaneously, improve the impedance measuring and calculating degree of accuracy, reduce the requirement to injection device DC voltage level, the reactance of wide frequency domain high frequency calculates and is exaggerated characteristic quantity difference before and after isolated island, has higher detection sensitivity and precision.
Description
Technical field
The present invention relates to Power System Analysis technical field, is concentrated more particularly to a kind of suitable for the outside of multimachine assembly
Disturbance formula impedance measurement isolated island detection method.
Background technology
The development of demand and Power Electronic Technique that high efficiency of energy utilizes promotes the new energy such as substantial amounts of photovoltaic and wind-powered electricity generation point
Cloth power grid, load nearby is powered.After distributed power source (Distributed Generator, DG) networks, due to master
Net failure and switch malfunction etc. cause DG and load nearby unplanned property islet operation, and entail dangers to power network line safeguards people
Member and the life security of user；Influence equipment normal operation and reclosing action in islanded system.So distributed grid-connected is sent out
Electric system must possess isolated island detectability.
Island detection method is divided into remote method and nation method according to whether relying on communication.Wherein nation method is according to work
Make principle and be divided into active and passive type again：Caused after passive detection method analysis isolated island because DG contributes to mismatch with load nearby
Protect installation place electrical quantity change, had/under-voltage, mistake/under-frequency detection method, phase hit detection method, voltage harmonic inspection
Survey method etc., this kind of method are realized simply, but contributed in distributed power source with check frequency be present during load approximate match nearby；It is main
Dynamic detection method is generally injected using inverter to system to be disturbed, and the front and rear response change of measuring system isolated island, there is impedance measurement, frequency
Check frequency can be reduced or eliminated in rate deflection method, Sandia frequency deviation methods and sliding formwork frequency deviation method etc., active detecting method, but
System power quality can be influenceed or even cause fault coverage to expand.
Traditional impedance measurement isolated island detection based on the disturbance of unit inverter generator terminal, before isolated island at PCC injections
System impedance change afterwards differentiates island operation state.In the system containing distributed power source, due to capacity difference, main power network
Equiva lent impedance is generally more much smaller than the equiva lent impedance of load so that the front and rear system impedance measured in PCC points of island state will be sent out
Raw significant changes, are easy to accurately identify.But this kind of method when being not used to multimachine existing disturbance influence each other problem, also because
It is controlled so as to be limited to power supply type dependent on inverter disturbance.
The main direction of studying detected at present through inverter networking distributed generator islanding is active detection method, to reduce
Or eliminate check frequency.However, as system is to multi-inverter, the grid-connected development of more power supply types, active method disturbing signal energy quilt
Amplify that destruction system is stable and the quality of power supply, can also cancel out each other causes isolated island detection failure, exist disturb between multimachine it is mutually dry
Phenomenon is disturbed, its isolated island detection validity is faced with new challenges, it is therefore desirable to which research is suitable for polymorphic type power supply, more parallel network reverses
The isolated island detection technique of device group system.
The content of the invention
In consideration of it, the shortcomings that it is an object of the invention to overcome prior art, there is provided one kind concentrates disturbance side based on outside
The impedance measurement isolated island detection method of formula, the difference of impedance characteristic is measured using system point of common coupling (PCC) place before and after isolated island, is adopted
Disturbed with the transient short pulse low current containing abundant cline frequency composition, the injection of intermittent zero crossing controls, wide frequency domain is high
Frequency reactance computational methods, avoid multimachine disturbing signal and interfere and fail, improve detection sensitivity and accuracy of detection, and
Reduce influence of the active method to system power quality.Independent concentration disturbing generating device, local prison are installed at system PCC
Survey and injection control system, voltage x current data acquisition device and corresponding data processing computing system, and thus calculating system
Measurement impedance characteristic amount simultaneously detects judgement island operation state.
In order to realize this purpose, the technical scheme that the present invention takes is as follows：
It is a kind of to concentrate disturbance formula impedance measurement isolated island detection method suitable for the outside of multimachine assembly, it is characterised in that described
Method comprises the following steps：
Step 1：Disturbing generating device, generation current perturbation signal i are concentrated using separate outerInj；
Step 2：Voltage u at monitoring system point of common couplingPCC, intermittent zero crossing injection control is carried out, was being injected
Simultaneously voltage u at acquisition system point of common coupling is measured in journey simultaneouslyPCCWith current perturbation signal iInjData；
Step 3：By voltage u at the system point of common coupling collectedPCCWith current perturbation signal iInjBy data processing
After measure impedance characteristic amount calculating；
Step 4：Island state is differentiated according to Feature change；
Disturbing generating device in the step A is independently of unique disturbance occurring source of system, the generation of disturbance and
Injection is terminated at system point of common coupling independent of inverter, device outlet.
Disturbing generating device in the step 1 is by a coupling inductance LcIt is followed by with a cutting-in control switch series connection
Between the parallel circuit for entering single-phase full bridge inverter circuit, load-side connects a direct voltage source composition；Coupling inductance LcValue
By DC voltage VAIESize and required current perturbation signal iInjSize determine, cutting-in control switch control disturbance fill
The break-make with system is put, individual event full bridge inverter uses wholly-controled device IGBT.
Current perturbation signal i in the step 1InjFor the short pulse delta current ripple containing abundant cline frequency composition,
It is passes through the break-make of IGBT in the bridge arm in control disturbance generating means, the caused coupled inductance L of step voltage waveformcAfterwards
The pulse delta current ripple of formation；Can control disturbance electricity by the break-make combination of IGBT in the bridge arm in control disturbance generating means
Flow signal iInjPulse width, by controlling DC voltage VAIEWith coupling inductance LcValue energy control disturbance current signal
iInjPeak value size.
Intermittent zero crossing injection control in the step 2, its method are：At monitoring system point of common coupling
Voltage uPCCZero crossing, in uPCCZero crossing at close cutting-in control switch, control the break-make of IGBT in bridge arm to generate simultaneously
Inject current perturbation signal iInj, current perturbation signal iInjAfter injection terminates, grid-connected switch is disconnected；In injection current perturbation signal
iInjDuring, voltage u at system point of common couplingPCCZero crossing monitoring locking, it is public to avoid the system caused by injection
Voltage u at Coupling pointPCCChange, injection terminate rear lock release；According to the quality of power supply and detection quick-action requirement, flexibly choosing
Select and inject current perturbation signal i to system at each or adjacent several zero crossingsInj；In injection current perturbation signal iInjMistake
Voltage u at acquisition system point of common coupling is measured in journey simultaneouslyPCCWith current perturbation signal iInjData；By public in system
Coupling point voltage uPCCPeriod injection current perturbation signal at zero crossing, makes voltage u at the system point of common coupling that collectsPCC
Central Plains system voltage composition minimizes, and active ingredient is the voltage responsive composition maximization disturbed, to improve signal to noise ratio and resistance
Anti- computational accuracy, while reduce required disturbance injection magnitude；The DC voltage V of disturbing generating deviceAIEOpened higher than cutting-in control
Close voltage u at the system point of common coupling during closingPCCPeak.
The computational methods that impedance characteristic amount is measured in the step 3 are using high frequency reactance X as the feature for judging isolated island
Amount, amplify the characteristic quantity difference before and after isolated island using Δ X=ω Δ L medium-high frequencies ω, under high frequency capacitive reactance greatly weakened so thatWherein Δ X is the variable quantity of high frequency reactance, and Δ L is the change of system equivalent inductance
Change amount, f are frequency, and L is system equivalent inductance, and C is electric capacity, so as to realize that good frequency domain reactance is linearly closed in high band range
System, on this basis, take the data of the high band linear segment, carry out wide frequency domain equivalent reactance calculating, then and indirect take
Certain single-frequency point calculates, but under reduction to certain frequency, the result of calculation of all frequencies in the frequency domain is averaged as measurement
Impedance characteristic amount.
Differentiate that the method for island state is to differentiate high frequency reactance X as isolated island according to Feature change in the step 4
Characteristic quantity, characteristic quantity threshold value and time limit are set, when the value in line computation characteristic quantity is higher than set characteristic quantity threshold value, and when set
Continuously it is higher than threshold value in limit, then is determined as island operation state.
Disturbance formula impedance measurement isolated island detection method is concentrated by using the outside of multimachine assembly that be applied to of the present invention, can
Had the beneficial effect that：
(1) system only exists a disturbing source, avoids more disturbing signals and influences each other problem, suitable for containing multi-inverter
Distributed power supply system；
(2) because employing independent injection device, disturbing signal is produced independent of inverter in this method, not by power supply type
Limitation, it is also applied for the power supply without inverter；
(3) controlled by injecting, improve the impedance measuring and calculating degree of accuracy, and reduce active method to system disturbance, ensure that
The good quality of power supply, while the requirement to injection device DC voltage level is reduced, it ensure that practicality；
(4) reactance of wide frequency domain high frequency calculates and is exaggerated characteristic quantity difference before and after isolated island, improves detection sensitivity and precision.
Brief description of the drawings
Fig. 1 concentrates disturbance formula to measure impedance isolated island detection method system structure diagram to be outside.
Fig. 2 concentrates disturbance formula to measure impedance isolated island detection method system equivalent schematic diagram to be outside.
Fig. 3 is independent disturbing generating device schematic diagram.
Fig. 4 is that disturbing generating device generates voltage, current disturbing waveform.
Fig. 5 a-5b are that voltage waveform shows at the Injection Current and corresponding PCC gathered according to the specific embodiment of the invention
It is intended to.
Fig. 6 a-6b are to be shown according to frequency domain measurement impedance computation result in the case of specific embodiment of the invention stable state and isolated island
It is intended to.
Fig. 7a-7c is according to specific embodiment of the invention time domain on-line measurement impedance characteristic Dependence Results figure.
Fig. 8 a-8b are according to specific embodiment of the invention time domain on-line measurement impedance in the case of 2 machines and white noise
Indicatrix result figure.
Fig. 9 is according to system harmonicses content analysis result figure before and after specific embodiment of the invention disturbance injection.
Figure 10 applies to the outside flow chart for concentrating disturbance formula impedance measurement isolated island detection method of multimachine assembly.
Embodiment
Below in conjunction with the accompanying drawings, the present invention is elaborated.
The structural representation of distributed power generation grid-connected system distributed power source, local load and power network as shown in figure 1, be made up of.
During normal operation, power supply, load are connected with major network.When failure or system are occurred compared with large disturbances, breaker actuation, distributed power source
Depart from major network, isolated island is formed with load nearby.
Outside concentration disturbance formula measurement impedance method proposed by the present invention, its equivalent constructions signal such as Fig. 2, different from traditional
Inverter generator terminal perturbation scheme, the present invention are injected using independent concentration disturbance is applied at PCC.
Its decanting point measures impedance characteristic and detection general principle is as follows：
In system, usual electric network impedance ZGridMuch smaller than distributed power source impedance ZDGWith load impedance Zload。
ZGrid＜ ＜ ZDG,ZGrid＜ ＜ Zload (1)
In formula, ZIslandingRepresent the systematic survey impedance after isolated island generation.
Measurement impedance Z before isolated island at PCCmeasFor：
Measurement impedance Z after isolated island at PCC 'measFor：
Z′meas=ZΙslanding＞ ＞ ZGrid＞ Zmeas (4)
Formula (3) and formula (4) show, the measurement impedance Z after isolated island at PCC 'measMeasurement noticeably greater than before isolated island at PCC
Impedance Zmeas, therefore impedance measurement isolated island detection is carried out using the difference of this impedance characteristic.System only exists one in this method
Individual disturbing source, avoid more disturbing signals and influence each other problem, suitable for distributed power supply system containing multi-inverter, use simultaneously
The disturbing generating device of independent injection, therefore it is also applied for direct grid-connected power supply.
Disturbing generating device theory structure is as shown in figure 3, by indirect one of the parallel circuit in single-phase full bridge inverter circuit
Coupling inductance L and cutting-in control switch, load-side connect a direct voltage source composition；Coupling inductance L value and direct current
Press VAIE, current perturbation signal iInjSize it is relevant, cutting-in control switch control disturbance generating means and system break-make, produce
Step voltage waveform, pulse delta current ripple is formed after coupled inductance L, as shown in Figure 4.The signal pulsewidth is controllable, can realize
Intermittence injection, Comparatively speaking continuing injection mode with specific frequency can be reduced to system disturbance, and the signal is included and enriched, even
Continuous frequency content, the calculating of high frequency linearity section wide frequency domain can be used for.
On injecting strategy, the present invention proposes the method that intermittent zero crossing injection controls.It is public by monitoring system
Voltage u at Coupling pointPCCZero crossing, in uPCCZero crossing at close cutting-in control switch, control bridge arm in IGBT break-make
To generate and inject current perturbation signal iInj, current perturbation signal iInjAfter injection terminates, grid-connected switch is disconnected；Disturbed in injection
During current signal, voltage u at system point of common couplingPCCZero crossing monitoring locking, avoid the system caused by injection
Voltage u at point of common couplingPCCChange, injection terminate rear lock release；According to the quality of power supply and detection quick-action requirement, spirit
Selection living injects current perturbation signal i at each or adjacent several zero crossings to systemInj；In injection current perturbation signal iInj
During simultaneously measure voltage u at acquisition system point of common couplingPCCWith current perturbation signal iInjData；By what is collected
Voltage u at system point of common couplingPCCWith current perturbation signal iInjThe calculating of impedance characteristic amount is measured after data processing；
By in system point of common coupling voltage uPCCPeriod injection current perturbation signal at zero crossing, makes the system that collects public
Voltage u at Coupling pointPCCCentral Plains system voltage composition minimizes, and active ingredient is the voltage responsive composition maximization disturbed, with
Signal to noise ratio and impedance computation precision are improved, while reduces required disturbance injection magnitude.
The DC voltage V of conventional grid-connected disturbance injection deviceAIEIt is higher than system point of common coupling voltage uPCC, otherwise note
Entering anti-paralleled diode in device can turn under system voltage, and this proposes very high requirement to DC capacitor and insulation.And this
Invent the disturbing generating device proposed, such as Fig. 3, by voltage u at detecting system point of common couplingPCC, when its horse back is to zero crossing
Close cutting-in control switch, injection current perturbation signal iInj, after short time disturbance terminates, cutting-in control switch is disconnected, as long as so
Seek VAIEHigher than voltage u ' at the system point of common coupling during cutting-in control switch closurePCCPeak.
Meanwhile the present invention uses high frequency reactance X to utilize Δ X=ω Δ L medium-high frequencies ω as the characteristic quantity for judging isolated island
Amplify the characteristic quantity difference before and after isolated island, so as to improve accuracy of detection and sensitivity.Capacitive reactance is greatly weakened under high frequency so thatSo as to realize good frequency domain reactance linear relationship in high band range, such as scheme
Shown in 6.On this basis, the data of the high band linear segment are taken, carry out wide frequency domain equivalent reactance calculating, it is then and indirect
Certain single-frequency point is taken to calculate, but under reduction to certain frequency, so as to improve impedance estimation precision and reliability.
Figure 10 applies to the outside flow chart for concentrating disturbance formula impedance measurement isolated island detection method of multimachine assembly.Use below
More specifical example concentrates the detection of disturbance formula impedance measurement isolated island to illustrate that the present invention is a kind of suitable for the outside of multimachine assembly
The technique effect of method, in this example using circuit model as shown in Figure 1, PMSG blower fans employ the classical type4 of system
Wind turbine models.
PMSG fan capacities 2MW, RLC load capacity 2MW, this causes passive detection method can not when blower fan is identical with load
Detection, system-side power source are ideal voltage source, transmission line of electricity voltage class 110kV, distribution network systems voltage class 35kV, and circuit is equal
Using π models, system side transformer capacity is 50MVA, and blower fan transformer capacity is 2.5MVA.
1. unit scene
It is respectively system point of common coupling voltage u after being injected using the zero crossing injection method of the present invention shown in Fig. 5 a and 5bPCC
With injection current perturbation signal iInjWaveform.Injection Current peak value is 22.5A, much smaller than system running current, uPCCWaveform institute
Show, the disturbance quantity brought to system voltage is smaller and the disturbance time is short.
Cut down by filtering, stable state waveform and fft algorithm is handled, to uPCCIn original system amount composition filtered out, its frequency
Domain impedance computation result is as shown in Figure 6.Impedance Z is carried out into reality/imaginary part (R/X) to decompose, dotted line is inferential impedance value, and solid line is
Using the inventive method and the impedance value of Equivalent Model measuring and calculating.Show that measuring and calculating value maintains less calculate with theoretical value and missed in figure
Difference, especially in high band, the measurement reactance X degree of accuracy ratio resistance R degree of accuracy is high, and X-f curve high bands show well
It is linear.
Found out by frequency domain measurement impedance after isolated island in Fig. 6, even if the system fundamental frequency electrical quantity dynamic change feelings after isolated island
Under scape, the measurement impedance computation value of the inventive method still has the very high degree of accuracy.From the measurement impedance of higher frequency band, shape
The measurement impedance characteristic curve of time domain is as shown in Figure 7 before and after into isolated island.Impedance computation employs wide frequency domain high frequency set forth above
Reactance aspect quantity algorithm, result of calculation are high frequency X reduction value of the reduction to 4kHz.
In Fig. 7, isolated island occurred at the 5s moment, figure a) be online impedance computation R indicatrixes, figure is b) using between fixed
Every the high frequency reactance X indicatrixes under injection mode, figure is c) height controlled using intermittent zero crossing injection method of the present invention
Frequency reactance X indicatrixes.Theoretical value, measuring and calculating value contrast to when each subgraph in figure, obtain, using intermittent zero crossing injection method
Calculating system high frequency reactance X, there is higher measurement accuracy, detected suitable for isolated island.And high frequency reactance characteristic quantity calculates are notable
The characteristic quantity difference being exaggerated before and after isolated island, improves isolated island detection sensitivity.
2. multimachine scene and noise analysis, power quality analysis
Fig. 8 a) it show under 2 machine scenes, using under different control strategies, different power output scenes, using this
The isolated island detection simulation result of literary method.Add and impedance computation result such as Fig. 8 b measured under 1% white noise) shown in.With Fig. 7 c) no
The original results of measuring of white noise is added to contrast, because system itself waveform (including noise) is minimized when zero crossing injects, this
The measuring and calculating value of inventive method still maintains higher identical property with theoretical value.
Proactive would generally bring the influence of the quality of power supply to system.In one cycle, having, containing without injection time-harmonic wave
Amount contrast is as shown in Figure 9.Voltage harmonic content, dotted line are the harmonic content after injection at system PCC when solid line is without injection, are
Facilitate harmonic contrast, 50Hz fundamental wave components have been rejected in figure.When system is without injection normal operation, system total harmonic distortion factor THD
For 0.020292%, THD is 0.024654% after injection, and this method influences little on system power quality.
Therefore, the detection of disturbance formula impedance measurement isolated island is concentrated by using the outside of multimachine assembly that be applied to of the present invention
Method, system only exist a disturbing source, avoid more disturbing signals and influence each other problem, suitable for distributed electrical containing multi-inverter
Source system；Cause employs independent injection device, and disturbing signal is produced independent of inverter in this method, not by power supply type office
Limit, it is also applied for the power supply that synchronous generator etc. is free of inverter；Controlled by injecting, improve the impedance measuring and calculating degree of accuracy, and
Active method is reduced to system disturbance, ensure that the good quality of power supply, while reduce to injection device DC voltage level
Requirement, ensure that practicality；The reactance of wide frequency domain high frequency calculates and is exaggerated characteristic quantity difference before and after isolated island, has higher detection
Sensitivity and precision.
It should be noted that above-mentioned embodiment is only the preferable embodiment of the present invention, it is impossible to is understood as to this
The limitation of invention protection domain, under the premise of without departing from present inventive concept, to any minor variations that the present invention is done and modification
Belong to protection scope of the present invention.
Claims (6)
1. a kind of concentrate disturbance formula impedance measurement isolated island detection method suitable for the outside of multimachine assembly, it is characterised in that the side
Method comprises the following steps：
Step 1：Disturbing generating device, generation current perturbation signal i are concentrated using separate outerInj；
Step 2：Voltage u at monitoring system point of common couplingPCC, intermittent zero crossing injection control is carried out, in injection process
Voltage u at measurement simultaneously and acquisition system point of common couplingPCCWith current perturbation signal iInjData；
Step 3：By voltage u at the system point of common coupling collectedPCCWith current perturbation signal iInjIt is laggard by data processing
Row measurement impedance characteristic amount calculates；
Step 4：Island state is differentiated according to Feature change；
Disturbing generating device in the step A is independently of unique disturbance occurring source of system, the generation and injection of disturbance
Independent of inverter, device outlet is terminated at system point of common coupling.
2. disturbance formula impedance measurement isolated island detection method is concentrated according to the outside of multimachine assembly that be applied to described in claim 1,
Characterized in that, the disturbing generating device in the step 1 is by a coupling inductance LcAfter a cutting-in control switch series connection
Access between the parallel circuit of single-phase full bridge inverter circuit, load-side connects a direct voltage source composition；Coupling inductance LcTake
Value is by DC voltage VAIESize and required current perturbation signal iInjSize determine that cutting-in control switchs control disturbance
The break-make of device and system, single-phase full bridge inverter circuit use wholly-controled device IGBT.
3. disturbance formula impedance measurement isolated island detection method is concentrated according to the outside of multimachine assembly that be applied to described in claim 2,
Characterized in that, the current perturbation signal i in the step 1InjFor the short pulse delta current containing abundant cline frequency composition
Ripple, it is passes through the break-make of IGBT in the bridge arm in control disturbance generating means, the caused coupled inductance of step voltage waveform
LcThe pulse delta current ripple formed afterwards；It can be controlled and disturbed by the break-make combination of IGBT in the bridge arm in control disturbance generating means
Streaming current signal iInjPulse width, by controlling DC voltage VAIEWith coupling inductance LcValue energy control disturbance electric current letter
Number iInjPeak value size.
4. disturbance formula impedance measurement isolated island detection method is concentrated according to the outside of multimachine assembly that be applied to described in claim 2,
Characterized in that, the intermittent zero crossing injection control in the step 2, its method are：Pass through monitoring system point of common coupling
Locate voltage uPCCZero crossing, in uPCCZero crossing at close cutting-in control switch, control the break-make of IGBT in bridge arm to generate
And inject current perturbation signal iInj, current perturbation signal iInjAfter injection terminates, cutting-in control switch is disconnected；In injection disturbance electricity
Flow signal iInjDuring, voltage u at system point of common couplingPCCZero crossing monitoring locking, avoid be caused by injection
Voltage u at system point of common couplingPCCChange, injection terminate rear lock release；Required according to the quality of power supply and detection quick-action,
Flexibly selection injects current perturbation signal i at each or adjacent several zero crossings to systemInj；In injection current perturbation signal
iInjDuring simultaneously measure voltage u at acquisition system point of common couplingPCCWith current perturbation signal iInjData；By
System point of common coupling voltage uPCCPeriod injection current perturbation signal at zero crossing, makes the system point of common coupling collected
Locate voltage uPCCCentral Plains system voltage composition minimizes, and active ingredient is the voltage responsive composition maximization disturbed, to improve letter
Make an uproar than with impedance computation precision, while reduce needed for disturbance injection magnitude；The DC voltage V of disturbing generating deviceAIEHigher than simultaneously
Voltage u at system point of common coupling during net controlling switch closurePCCPeak.
5. disturbance formula impedance measurement isolated island detection method is concentrated according to the outside of multimachine assembly that be applied to described in claim 1,
Characterized in that, the computational methods that impedance characteristic amount is measured in the step 3 are using high frequency reactance X as the spy for judging isolated island
Sign amount, amplify the characteristic quantity difference before and after isolated island using Δ X=ω Δ L medium-high frequencies ω, under high frequency capacitive reactance greatly weakened, make
Wherein Δ X is the variable quantity of high frequency reactance, and Δ L is system equivalent inductance
Variable quantity, f are frequency, and L is system equivalent inductance, and C is electric capacity, so as to realize that good frequency domain reactance is linear in high band range
Relation, on this basis, the data of the high band linear segment are taken, carry out wide frequency domain equivalent reactance calculating, it is then and indirect
Certain single-frequency point is taken to calculate, but under reduction to certain frequency, the result of calculation of all frequencies in the frequency domain is averaged as survey
Measure impedance characteristic amount.
6. disturbance formula impedance measurement isolated island detection method is concentrated according to the outside of multimachine assembly that be applied to described in claim 1,
Characterized in that, differentiate that the method for island state is using high frequency reactance X as isolated island according to Feature change in the step 4
Differentiate characteristic quantity, characteristic quantity threshold value and time limit are set, when the value in line computation characteristic quantity is higher than set characteristic quantity threshold value, and in institute
If being continuously higher than threshold value in the time limit, then it is determined as island operation state.
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| CN107121609B (en) * | 2017-05-22 | 2023-04-07 | 广西大学 | Power grid impedance online identification method and device based on PRBS disturbance injection |
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