CN103969549A - Island detection method and device for electrical power device - Google Patents
Island detection method and device for electrical power device Download PDFInfo
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- CN103969549A CN103969549A CN201410159413.4A CN201410159413A CN103969549A CN 103969549 A CN103969549 A CN 103969549A CN 201410159413 A CN201410159413 A CN 201410159413A CN 103969549 A CN103969549 A CN 103969549A
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Abstract
The invention discloses an island detection method and device for an electrical power device. The method includes the steps that the actual working frequency f0 of a power distribution system is obtained, and a corresponding power frequency period T is calculated according to the formula T=1/ f0; then the sampling frequency fc of the point of common coupling (PCC) of the power distribution system and a distributed power supply or a microgrid is obtained; according to the sampling frequency fc, the power frequency period T is divided into N time periods, and the formula N= fc/ f0 is met, wherein the formula delta t =T/N=1/ fc is met; corresponding voltage sampling data u(n delta t) (n=0,1,2...,N) of the PCC in each time period n delta t (n=0,1,2...,N) are collected; integral operation is performed on the voltage sampling data to obtain integral values L, and the formula of L is expressed in the specification; L is compared with the threshold value beta of the island phenomenon, and if L is larger than beta, it is proved that the island phenomenon happens. The detection method is not affected by conventional interference factors in the detection process, and the integration of the whole power frequency period starting from any time can serve as a judgment criterion; only one power frequency period is needed for obtaining a judgment result, the detection speed is high, and the island detection method and device are beneficial for rapidly isolating faults and guaranteeing operation reliability of the power distribution system.
Description
Technical field
The present invention relates to power domain, particularly a kind of island detection method of power-supply device and isolated island detecting device.
Background technology
At present, the distributed power source taking wind-powered electricity generation, solar electrical energy generation as representative, because of its flexibly, the advantage such as low-carbon environment-friendly, be subject to the extensive concern of academia and industry member, meanwhile, the permeability of distributed power source in distribution system improves year by year.Distributed power source can disperse to access distribution system, also can be with the form access distribution system of microgrid.For distribution system, most distributed power sources are uncontrollable power supply, and its output power is often subject to the impact of natural conditions and has stronger random character.For safeguards system reliability of operation, require distributed power source or microgrid to possess isolated island measuring ability, so that timely isolated fault in the time of distribution network or microgrid internal fault.In numerous island detection methods, phase shift method is widely applied because of its good sensitivity.Can in half power frequency cycle, obtain rapidly waveform phase by the zero crossing that detects grid-connected point voltage waveform, detect thereby complete fast isolated island.This zero passage detection method accuracy of detection in the time that tested waveform is smoother is higher, and electrical network inevitably can be subject to the impact of the various interference such as load change, element switching, electric motor starting in actual moving process, thereby make check point voltage waveform distortion, produce burr, before and after power-frequency voltage zero crossing, may be consecutively detected several points of zero voltage like this, cause the inaccurate even mistake of phase-detection, very easily cause the misoperation of isolated island detecting unit, and then affect the reliability service of distribution system.
Summary of the invention
For addressing the above problem, the object of the present invention is to provide a kind of island detection method and isolated island detecting device of power-supply device, automatically eliminate the impact that gathers burr in voltage, and improve the precision that isolated island detects.
The present invention solves the technical scheme that its problem adopts:
The island detection method of power-supply device, described power-supply device comprises the microgrid power supply of the access distribution system of disperseing the distributed power source of access distribution system or be made up of distributed power source, described method comprises:
(1) obtain the actual operating frequency of distribution system
, and calculate corresponding power frequency period
;
(2) obtain the sample frequency at distribution system and distributed power source or microgrid points of common connection PCC place
, and according to sample frequency
by power frequency period
be divided into
the individual period, and
, each period
;
(3) gather PCC point in each period
corresponding voltage sample data
;
(4) voltage sample data carried out to integral operation and obtain integrated value
, described in
;
(5) detect
threshold value with the generation of isolated island phenomenon
size, if
>
, show to occur isolated island phenomenon, otherwise, proceed to step (3) cycle detection.
The isolated island detecting device of power-supply device, described power-supply device comprises the microgrid power supply of the access distribution system of disperseing the distributed power source of access distribution system or be made up of distributed power source, described device comprises:
Parameter initial module, for obtaining the actual operating frequency of distribution system
, calculate corresponding power frequency period
, and according to the sample frequency at points of common connection PCC place
, by power frequency period
be divided into
the individual period, and
, each period
;
Acquisition module, for gathering PCC point in each period
corresponding voltage sample data
;
Processing module, for carrying out voltage sample data integral operation and obtaining integrated value
, described in
, and judge integrated value
threshold value with the generation of isolated island phenomenon
size;
Alarm module, for detecting in processing module
>
, send isolated island warning message.
The invention has the beneficial effects as follows:
The present invention adopts a kind of island detection method and isolated island detecting device of power-supply device, the sampled voltage gathering is adopted to the method for orthogonal integration, automatically eliminate the impact of burr in waveform, and the criterion detecting the result of numerical integration as isolated island, the degree of accuracy detecting improved; The present invention is without using zero crossing as phase reference, and any time plays the integration of power frequency complete cycle and can serve as basis for estimation; The present invention only needs a power frequency period can draw differentiation result, is conducive to quick isolated fault and ensures distribution system reliability of operation.
Brief description of the drawings
Below in conjunction with accompanying drawing and example, the invention will be further described.
Fig. 1 is the schematic diagram of island detection method of the present invention;
Fig. 2 is the point of PCC described in the present invention phase voltage waveform figure of place;
Fig. 3 is the orthogonal integration schematic diagram of the present invention while there is isolated island phenomenon.
Embodiment
Shown in Fig. 1, isolated island phenomenon refers to when mains supply is because of failure accident or have a power failure maintenance when escape, the distributed grid-connected electricity generation system (as: photovoltaic generation, wind-power electricity generation, fuel cell power generation etc.) of each user side fails immediately to detect power down mode and will self cut off electricity network, and forms the isolated island of the self-energizing being made up of distribution electric station grid connection electricity generation system and load around.Now, independent distributed power source DG can power alone.Once isolated island produces the safety of maintenance personal on entail dangers to power grid transmission line road; Affect the operation program of the protection switch in distribution system, impact electric network protection Zhuan Ge; Affect electric energy transmitting quality, the supply voltage in electric power isolated island region and frequency are by unstable; The phase place that can cause after mains supply recovers is asynchronous; Single-phase distributed generation system can cause system threephase load to owe to power mutually.Therefore anti-island effect detection must can be carried out for a grid-connected system.
In numerous island detection methods, phase shift method is widely applied because of its good sensitivity.Can in half power frequency cycle, obtain rapidly waveform phase by the zero crossing that detects grid-connected point voltage waveform, detect thereby complete fast isolated island.This zero passage detection method accuracy of detection in the time that tested waveform is smoother is higher, and electrical network inevitably can be subject to the impact of the various interference such as load change, element switching, electric motor starting in actual moving process, thereby make check point voltage waveform distortion, produce burr, before and after power-frequency voltage zero crossing, may be consecutively detected several points of zero voltage like this, cause the inaccurate even mistake of phase-detection, very easily cause the misoperation of isolated island detecting unit, and then affect the reliability service of distribution system.Shown in Fig. 2, this is the voltage oscillogram of actual detection voltage gained in the time that distribution system is normally moved, as can be seen from the figure, power-frequency voltage is in the time of zero crossing, the voltage that the points of common connection PCC place of distributed power source records is not the power frequency sine wave of standard, but contain certain harmonic wave, these harmonic waves have multiple zero-point voltages while causing voltage waveform zero crossing, with reference to amplifying in Fig. 2 shown in figure, three zero-point voltage P1 in enlarged drawing, are produced, P2, P3, if now adopt phase-detection, obviously can cause detecting the inaccurate mistake that even causes detecting.
Shown in Fig. 3, under normal circumstances, the voltage that points of common connection PCC place records
waveform as shown in FIG., is considered harmonic voltage, the voltage that points of common connection PCC place is recorded
express by Fourier series exhibition formula, as represented with following formula (1):
Wherein,
for DC component,
with
be respectively
the amplitude of subharmonic voltage and phase angle,
for power frequency angular frequency.Order
,
,
,
, formula (1) can be rewritten as:
, using this as formula (2).
Be constructed as follows trigonometric function system according to formula (2):
, this is formula (3).
Known above
can regard that by trigonometric function be the trigonometric series producing as.Be the feature of orthogonality according to trigonometric function, be tied to form vertical just like ShiShimonoseki:
(4)
(5)
In formula,
for the initial time of sense cycle,
for the cycle of power-frequency voltage,
with
for nonnegative integer.
Therefore, any one in the trigonometric function system of modus ponens (3), is designated as
, the left and right sides of same multiplier (2), and at a power frequency period
interior integration, will obtain a time-independent definite value, and this integral result is designated as
.Such as getting
, have:
(6)
When getting
time, have:
(7)
For reducing the calculated amount of numerical integration, the present invention gets
, carry out integration by formula (7).In formula
.
Like this, in the time that distribution system is normally moved, be 0 containing non-smooth waveform value after the integral operation of a power frequency period of integral frequency harmonizing wave.
When distribution system breaks down, after corresponding feeder switch tripping, because distributed power source does not mate with the load in isolated island, cause the fundamental frequency of isolated island to change, thereby the voltage waveform of PCC check point distort, in Fig. 3
shown in, in figure
represent the moment that isolated island occurs.
According to above description, in like manner, will
also expand into the form of Fourier series:
(8)
In formula,
for
dC component,
with
be respectively the waveform after isolated island occurs
's
the amplitude of subharmonic voltage and phase angle,
for
fundamental frequency.
，
，
，
Get
, to the voltage waveform in Fig. 3 from
arrive
carry out integration, integral result is designated as
, due to voltage waveform from
arrive
change, therefore:
(9)
Due to
, therefore integral result
non-vanishing, as shown in the dash area in Fig. 3.Due to
size relevant with the degree of frequency shift (FS) or phase deviation, therefore, can carry out isolated island differentiation by this feature.
Just Given this, adopt above isolated island method of discrimination, the invention provides a kind of island detection method of power-supply device, power-supply device comprises the microgrid power supply of the access distribution system of disperseing the distributed power source of access distribution system or be made up of distributed power source, and described method comprises:
(1) obtain the actual operating frequency of distribution system
, and calculate corresponding power frequency period
;
(2) obtain the sample frequency at distribution system and distributed power source or microgrid points of common connection PCC place
, and according to sample frequency
by power frequency period
be divided into
the individual period, and
, each period
;
(3) gather PCC point in each period
corresponding voltage sample data
;
(4) voltage sample data carried out to integral operation and obtain integrated value
, described in
;
(5) detect
threshold value with the generation of isolated island phenomenon
size, if
>
, show to occur isolated island phenomenon, otherwise, proceed to step (3) cycle detection.
Detection method provided by the invention is not subject to the impact of conventional disturbing factor (as normal load fluctuation) in the time detecting, and solved zero passage detection method and be subject to the impact of waveform burr phenomena; Relatively zero crossing detects, the present invention's flexible and convenient more in the time detecting, and without using zero crossing as phase reference, and any time plays the integration of power frequency complete cycle and can serve as basis for estimation; Detection method of the present invention only needs a power frequency period can draw differentiation result, and detection speed is very fast, is conducive to quick isolated fault and ensures distribution system reliability of operation.
As another protection form of the present invention, the invention provides a kind of isolated island detecting device of power-supply device, described device comprises:
Parameter initial module, for obtaining the actual operating frequency of distribution system
, calculate corresponding power frequency period
, and according to the sample frequency at points of common connection PCC place
, by power frequency period
be divided into
the individual period, and
, each period
;
Acquisition module, for gathering PCC point in each period
corresponding voltage sample data
;
Processing module, for carrying out voltage sample data integral operation and obtaining integrated value
, described in
, and judge integrated value
threshold value with the generation of isolated island phenomenon
size;
Alarm module, for detecting in processing module
>
, send isolated island warning message.
The concrete implementation method of described device is with reference to content described in above method; described device is a kind of physical protection to adopting the method for the invention; any power-supply device, the device of every employing the method for the invention, system are all within protection scope of the present invention.
The above, be preferred embodiment of the present invention, and the present invention is not limited to above-mentioned embodiment, as long as it reaches technique effect of the present invention with identical means, all should belong to protection scope of the present invention.
Claims (2)
1. the island detection method of power-supply device, described power-supply device comprises the microgrid power supply of the access distribution system of disperseing the distributed power source of access distribution system or be made up of distributed power source, it is characterized in that, described method comprises:
(1) obtain the actual operating frequency of distribution system
, and calculate corresponding power frequency period
;
(2) obtain the sample frequency at distribution system and distributed power source or microgrid points of common connection PCC place
, and according to sample frequency
by power frequency period
be divided into
the individual period, and
, each period
;
(3) gather PCC point in each period
corresponding voltage sample data
;
(4) voltage sample data carried out to integral operation and obtain integrated value
, described in
;
(5) detect
threshold value with the generation of isolated island phenomenon
size, if
>
, show to occur isolated island phenomenon, otherwise, proceed to step (3) cycle detection.
2. the isolated island detecting device of power-supply device, described power-supply device comprises the microgrid power supply of the access distribution system of disperseing the distributed power source of access distribution system or be made up of distributed power source, it is characterized in that, described device comprises:
Parameter initial module, for obtaining the actual operating frequency of distribution system
, calculate corresponding power frequency period
, and according to the sample frequency at points of common connection PCC place
, by power frequency period
be divided into
the individual period, and
, each period
;
Acquisition module, for gathering PCC point in each period
corresponding voltage sample data
;
Processing module, for carrying out voltage sample data integral operation and obtaining integrated value
, described in
, and judge integrated value
threshold value with the generation of isolated island phenomenon
size;
Alarm module, for detecting in processing module
>
, send isolated island warning message.
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|---|---|---|---|
| CN201410159413.4A CN103969549B (en) | 2014-04-18 | 2014-04-18 | The island detection method of power-supply device and isolated island detecting device |
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|---|---|---|---|
| CN201410159413.4A CN103969549B (en) | 2014-04-18 | 2014-04-18 | The island detection method of power-supply device and isolated island detecting device |
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| CN103969549B CN103969549B (en) | 2016-08-17 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108899935A (en) * | 2018-08-16 | 2018-11-27 | 广州供电局有限公司 | And off-network switching equipment and system |
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| Publication number | Publication date |
|---|---|
| CN103969549B (en) | 2016-08-17 |
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