CN104062529B - A kind of island detection method - Google Patents
A kind of island detection method Download PDFInfo
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- CN104062529B CN104062529B CN201410324666.2A CN201410324666A CN104062529B CN 104062529 B CN104062529 B CN 104062529B CN 201410324666 A CN201410324666 A CN 201410324666A CN 104062529 B CN104062529 B CN 104062529B
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Abstract
A kind of island detection method, passive means is engaged with active method, used/under-frequency and mistake/under-voltage method can quick detection go out isolated island, and the quality of power supply is not influenceed；After there is isolated island, and during the matching of islanded system internal power, the capacitor switching method using harmonic detecting as criterion is used, the power match of system can be destroyed so that voltage and frequency in system change, so as to detect isolated island.
Description
Technical field
Concentrate grid-connected anti-isolated island to protect field the invention belongs to extensive new energy, be a kind of passive detection and actively inspection
The anti-isolated island protection detection scheme that survey is combined, more particularly to the isolated island inspection of voltage/frequency detection harmonic detection capacitor switching
Survey method.
Background technology
After isolated island refers to electric network fault, distributed generation system is still to load supplying around, so as to form one cannot control
The local supply network of system.Unplanned isolated island can bring some serious problems to the safe and stable operation of power system, such as lonely
Voltage and frequency in island is uncontrollable, and the equipment of user may be caused to damage；Circuit in isolated island is still powered, may
Personal safety of entail dangers to maintainer etc..The Main Function of isolated island detection be when distributed system and major network depart from, and
When disconnect distributed power source, prevent unplanned islet operation.Conventional island detection method can be divided into remote detection method, quilt at present
Dynamic detection method and active detecting method three major types.
Passive detection method is, by gathering local signal, to carry out isolated island detection in the case of not additional any disturbance, often
There are voltage/frequency detection method, voltage harmonic detection method and voltage-phase abrupt climatic change method etc..Its advantage is simple principle,
Equipment investment is few, it is easy to accomplish, it is noiseless to power network, on the quality of power supply without influence；Under many inverters, detection efficiency will not
Reduce, have the disadvantage that check frequency is larger.
Wherein, voltage/frequency detection method is judged by detecting the voltage and frequency of PCC (power network points of common connection)
Whether grid-connected system there is island state.During normal operation, DG (distributed power generation) system output voltages or frequency receive bulk power grid
Voltage clamp, will not change.When island state, DG systems do not receive bulk power grid voltage clamp, if DG system inverters
Power output and local load power are uneven, and output voltage or frequency will change.If voltage and frequency change exceed
The normality threshold of setting, then can detect isolated island and occur.General combining inverter can configure overvoltage protection (OVR), under-voltage guarantor
Shield (UVR), over frequency protection (OFR), the protection of four kinds of underfrequency protection (UFR), these protections are detect island effect most basic, most
Direct method, when line voltage, frequency is detected more than normal scope, that is, is judged as that isolated island occurs, protection circuit
Combining inverter is just cut off into power network.But when DG system output powers are nearly matching with local bearing power after grid cut-off
The voltage and frequency of PCC points are varied less, and these variable quantities are not enough to start OVR/UVR and OFR/UFR, isolated island detection failure.
Meanwhile, can not set too low for the normal fluctuation for preventing line voltage and frequency causes the threshold value of misoperation, four kinds of protections, lead
There is larger check frequency in cause.
Active detecting method is carried out detection and sentences by artificially introducing small voltage, electric current or frequency disturbance signal to system
Fixed, conventional has impedance measurement, reactance insertion, voltage shift method, power disturbance method, active frequency drift method and sliding formwork frequently
Rate drift etc..Advantage is that active method remains to detect isolated island when distributed power source output power is with power match needed for load,
Blind area is smaller, sensitivity is higher, has the disadvantage that the disturbance control as introduced system is improper, after micro-capacitance sensor can be caused to enter island state
Cannot stable operation.
Wherein, external switch capacitance detecting method is added on the relay of the areas adjacent matched with local load capacity in DG
Dress can automatic switching electric capacity, change system load impedance, when municipal power failure, will electric capacity be incorporated to, it is broken by reactive power
Bad system balancing, can by detect voltage, frequency ANOMALOUS VARIATIONS come judge whether occur isolated island.This method has two kinds
Implementation, one kind is periodicity switching capacitance, that is, a time interval is set, every one or several cycle capacitance switch
State by being disconnected to closure, by after certain hour disconnect, so repeatedly, if capacitance switch close during there is isolated island,
Electric capacity will change the power output of islanded system.But the method for periodically putting into capacitor is used, if the electric capacity of input is larger,
Voltge surge may be uninterruptedly caused to the less distribution network system of capacity, there is certain shadow to the quality of power supply when being incorporated into the power networks
Ring；Secondly, this method is higher to switch reliability requirement, and periodicity switching can shorten the service life of switch.Second
It is then to be engaged with being switched at PCC points, such as Fig. 1 breaker in middle S1, when switching S1 and disconnecting, switch S2 closures, external capacitor is simultaneously
Enter system, destroy the power-balance of system.The shortcoming of the method is that the switching of electric capacity will coordinate with the switch at PCC points, it is necessary to
Detect PCC points switch to have disconnected and could put into electric capacity, if detection means breaks down, isolated island detection will fail.In addition, the party
Method has to look for power match point, but the trend of power system is often change, it is difficult to find fixed power match point.
In summary analysis understands that voltage/frequency detection method can be in the power output of DG system inverters and local load
Effective detection goes out isolated island during unbalanced power, but when the power output of DG system inverters and local load power are balanced, should
Method fails.And external switch capacitance detecting method can have when the power output of DG system inverters and local load power are balanced
Effect detection isolated island, but to switching, performance requirement is high or needs are switched with PCC points and coordinated.Therefore, it can be detected with reference to voltage/frequency
Method and the respective advantage of external switch capacitance detecting method, and be suitably modified, search out a kind of more effective practical isolated island inspection
Survey method, realizes detection non-blind area.
The content of the invention
To ensure the stationarity of micro-capacitance sensor running state conversion, while considering accuracy of detection, sensitivity and disturbance to system
The influence of stable operation, the application proposes a kind of suitable for micro-capacitance sensor feature, the group based on passive detection, supplemented by active detecting
Close decision-making isolated island detection scheme：The passive means of this programme used/under-frequency and mistake/under-voltage detection method, active method used with harmonic wave
Aberration rate is the capacitor switching method of criterion.The mistake that the program is carried first with inverter/under-frequency device and mistake/under-voltage device reality
When detection PCC points frequency and voltage, DG systems any place install harmonic measurement device, real-time detection percent harmonic distortion,
Need not again look for power match point that installation is set.Capacitor is connected by switch with harmonic measurement device, and is controlled by it.It is former
Reason figure is shown in Fig. 2, if harmonic measurement device detects threshold value of the percent harmonic distortion beyond setting, and mistake/under-frequency device and mistake/owe
The frequency of pressure device detection, voltage and not less than threshold value, now may the reason for be：
1st, system disturbance in itself, such as nearby has high ferro process or large steel-making plant making steel or there occurs transient fault
Deng；
2nd, there occurs isolated island when the power output of DG system inverters and local load power are balanced.
In view of the possibility that system disturbance occurs, the time delay for setting 1s is cut escaping ringing action time and failure
Reclosure time after removing, in 1s time delays, if percent harmonic distortion is less than threshold value, voltage, frequency also without departing from threshold value, are then said
Bright original harmonic distortion is that disturbance by system in itself causes or automatic reclosing switchs PCC to overlap, without occurring
Isolated island；After 1s time delays terminate, percent harmonic distortion still exceeds threshold value, and voltage, frequency are then illustrated now without departing from threshold value
Isolated island is may have occurred, and the power that inverter sends is matched with local load power, by switch S2 closures, puts into electric capacity,
Destruction system balancing so that voltage, frequency have greatly changed, inverter is able to detect that these change, and is detected in 2s
Go out isolated island, stop power supply and (requirement of GB/T 19939-2005 is required according to China's photovoltaic system interconnection technology, when isolated island occurs
When, isolated island should be detected in 2s, if isolated island cannot be detected in 2s, it is considered as detection failure).
The island detection method being engaged with voltage/frequency detection based on harmonic detecting capacitor switching is comprised the following steps,
Its flow chart is shown in Fig. 3：
Step one：/ frequency and voltage of under-frequency device and mistake/under-voltage device real-time detection PCC points were utilized, using actively
Formula detection method, i.e. harmonic measurement device real-time detection percent harmonic distortion；
Step 2：Judge whether the frequency for detecting, voltage have exceeded the threshold value of setting, if it is, step 5 is carried out, such as
Whether fruit is not to judge percent harmonic distortion beyond threshold value, if it is, carrying out step 3；If it is not, carry out step one；
Step 3：Start-up study 1S, if detect voltage, frequency, percent harmonic distortion after time delay 1S terminates do not surpassed
Go out threshold value, then return to step one；If detecting percent harmonic distortion after time delay 1S terminates still beyond threshold value, and voltage, frequency
Without departing from threshold value, then step 4 is carried out；
Step 4：Closure switch S1, puts into electric capacity, the voltage and frequency of islanded system is measured using inverter, if electric
Pressure and frequency exceed threshold values, then step 5 is performed, if without departing from threshold values, return to step one；
Step 5：It is judged to isolated island.
Beneficial effects of the present invention are：The application is a kind of isolated island detection scheme that passive means is engaged with active method,
In most cases, islanded system internal power is mismatched after there is isolated island, and voltage and frequency can have greatly changed, now
Using/method of under-frequency and mistake/under-voltage can quick detection go out isolated island, and the quality of power supply is not influenceed；When generation isolated island
Afterwards and islanded system internal power match when, use the capacitor switching method using harmonic detecting as criterion, the work(of system can be destroyed
Rate is matched so that voltage and frequency in system change, so as to detect isolated island.Compared with traditional passive detection method,
This programme is capable of detecting when power matching state, and has put into electric capacity in power match, can breakdown power matching, do not exist
Check frequency；Compared with traditional active detecting method, this programme does not influence the quality of power supply when grid-connected inverters run, and only
Need to simply be transformed in net side, the mistake/under-frequency and mistake/under-voltage protection that usable inverter has in itself are capable of achieving detection,
New algorithm need not be installed additional on every inverter, it is easy to accomplish；Compared with traditional capacitor switching method, this programme uses harmonic wave
Aberration rate as start-up criterion, without coordinating with PCC on off states, the point without finding power match, and detection efficiency and dress
The position for putting installation is unrelated, it is easy to accomplish.Therefore, new method does not exist check frequency, influences small to the quality of power supply, it is possible to achieve
Fast and effectively isolated island detects function, with practical meaning in engineering.
Brief description of the drawings
Fig. 1 is traditional external switch capacitance detecting method schematic diagram；
Fig. 2 is the schematic diagram based on harmonic detecting capacitor switching island detection method；
Fig. 3 is the flow chart of the island detection method being engaged with voltage/frequency detection based on harmonic detecting capacitor switching；
The island detection method being engaged with voltage/frequency detection based on harmonic detecting capacitor switching when Fig. 4 (a) is isolated island
Harmonic wave analogous diagram；
The island detection method being engaged with voltage/frequency detection based on harmonic detecting capacitor switching when Fig. 4 (b) is isolated island
Common point voltage analogous diagram；
The island detection method being engaged with voltage/frequency detection based on harmonic detecting capacitor switching when Fig. 4 (c) is isolated island
Public dot frequency analogous diagram.
Specific embodiment
The present invention is further described below in conjunction with the accompanying drawings.
The island detection method being engaged with voltage/frequency detection based on harmonic detecting capacitor switching is comprised the following steps：
Step one：/ frequency and voltage of under-frequency device and mistake/under-voltage device real-time detection PCC points were utilized, using actively
Formula detection method, i.e. harmonic measurement device real-time detection percent harmonic distortion；
Step 2：Judge whether the frequency for detecting, voltage have exceeded the threshold value of setting, if it is, step 5 is carried out, such as
Whether fruit is not to judge percent harmonic distortion beyond threshold value, if it is, carrying out step 3；If it is not, carry out step one；
Step 3：Start-up study 1S, if detect voltage, frequency, percent harmonic distortion after time delay 1S terminates do not surpassed
Go out threshold value, then return to step one；If detecting percent harmonic distortion after time delay 1S terminates still beyond threshold value, and voltage, frequency
Without departing from threshold value, then step 4 is carried out；
Step 4：Closure switch S1, puts into electric capacity, the voltage and frequency of islanded system is measured using inverter, if electric
Pressure and frequency exceed threshold values, then step 5 is performed, if without departing from threshold values, return to step one；
Step 5：It is judged to isolated island.
Detection criteria is as follows：
(1) specify in GB12326-90, it is ± the 5% of rated value to weigh point for points of common connection voltage allows skew, if
Perunit value is converted, isolated island is judged to when common point voltage is detected more than 1.05 or less than 0.95.
(2) specify in GB/T15945-95, for the deviation that power system is allowed, normally allow to be ± 0.2Hz, for small
Capacity system can be loosened to ± 0.5Hz, and microgrid belongs to low capacity system, and frequency detecting criterion is set as fmin=49.5Hz,
Fmax=50.5Hz, that is, the common point electric voltage frequency for detecting is judged to isolated island less than 49.5Hz or more than 50.5Hz.
(3) specify in GB/T14549-93, the measurement point of 380V voltage class is the mains by harmonics distortion of points of common connection
Rate THD is 5% (0.05), that is, when detecting percent harmonic distortion more than 5% (0.05), judge that power network occurs abnormal.
Fig. 4 show the isolated island detection simulation figure obtained using the inventive method, and isolated island, the 5th second took place from the 4th second
Input electric capacity C=0.0001F.Fig. 4 (a) gives the harmonic wave analogous diagram based on the method, is as can be seen from the figure sent out at the 4th second
Percent harmonic distortion has just exceeded 5% after raw isolated island, and 1 second percent harmonic distortion of time delay is still above 5%；Fig. 4 (b) gives and is based on being somebody's turn to do
The common point voltage analogous diagram of method, after as can be seen from the figure there is isolated island at the 4th second, due to system power matching, voltage
Substantially unchanged, voltage is still unchanged after time delay 1 second, without departing from threshold value；Fig. 4 (c) is given based on the public of the method
Dot frequency analogous diagram, after as can be seen from the figure there is isolated island at the 4th second, due to system power matching, frequency is varied less, prolonged
When 1 second after frequency change still very little, without departing from threshold value.Electric capacity was put at the 5th second, as can be seen that harmonic wave from analogous diagram
Aberration rate is smaller than before not throwing on the contrary after electric capacity is put into, and illustrates that the capacitance of selection is appropriate, there is provided system reactive power,
Reduce percent harmonic distortion；Common point voltage reduces rapidly after electric capacity is put into, beyond threshold value；Public dot frequency also subtracts rapidly
It is small, beyond threshold value.Voltage/frequency detection means starts the rapid action of isolated island protection, and isolated island is detected successfully.
Claims (4)
1. a kind of island detection method, comprises the following steps：
Step one：/ frequency and voltage of under-frequency device and mistake/under-voltage device real-time detection PCC points were utilized, using harmonic detecting
Device real-time detection percent harmonic distortion；
Step 2：Judge whether the frequency for detecting, voltage have exceeded the threshold value of setting, if it is, step 5 is carried out, if not
Whether it is to judge percent harmonic distortion beyond threshold value, if it is, carrying out step 3；If it is not, carry out step one；
Step 3：Start-up study 1S, if detect voltage, frequency, percent harmonic distortion after start-up study 1S terminates do not surpassed
Go out threshold value, then return to step one；If detecting percent harmonic distortion after time delay 1S terminates still beyond threshold value, and voltage, frequency
Without departing from threshold value, then step 4 is carried out；The percent harmonic distortion is 5%；
Step 4：Closure switch S1, put into electric capacity, using inverter measure islanded system voltage and frequency, if voltage and
Frequency exceeds threshold values, then step 5 is performed, if without departing from threshold values, return to step one；
Step 5：It is judged to isolated island.
2. island detection method according to claim 1, it is characterised in that the threshold value of frequency described in step 2 is fmin=
49.5Hz, fmax=50.5Hz.
3. island detection method according to claim 1, it is characterised in that the threshold value of voltage described in step 2 is public company
The side-play amount that junction voltage is allowed, in the range from ± the 5% of rated value.
4. island detection method according to claim 1, it is characterised in that the electric capacity C=put into described in step 4
0.0001F。
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| CN104267317B (en) * | 2014-10-21 | 2017-02-22 | 华北电力大学 | Islanding detection method based on reactance layered switching |
| CN104655957B (en) * | 2015-01-28 | 2018-05-04 | 东南大学 | It is a kind of to lead the mixed type island detection method passively combined |
| CN105974238B (en) * | 2016-06-20 | 2019-07-23 | 重庆瑜欣平瑞电子股份有限公司 | Gasoline engine inverter automatic test approach and system |
| CN107765108B (en) | 2016-08-18 | 2020-01-21 | 华为技术有限公司 | Island detection method and device of inverter and power supply system |
| CN107918082B (en) * | 2016-10-10 | 2021-01-15 | 中国电力科学研究院 | Island detection method for parallel operation of inverters |
| CN107422196B (en) * | 2017-02-27 | 2019-12-06 | 国电南瑞科技股份有限公司 | Island detection method based on harmonic distortion rate and frequency |
| CN107526009B (en) * | 2017-09-13 | 2019-04-05 | 国电南瑞科技股份有限公司 | It is a kind of that Interlocking Methods are detected according to the isolated island of frequency and curent change timing |
| CN110632413B (en) * | 2019-09-02 | 2022-02-11 | 国网吉林省电力有限公司 | Reactive power disturbance island detection method triggered in delayed mode |
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| JP2563647B2 (en) * | 1990-06-12 | 1996-12-11 | 関西電力株式会社 | Accident point location system for parallel two-line power system |
| CN101847876A (en) * | 2010-05-28 | 2010-09-29 | 上海理工大学 | Three-phase photovoltaic grid connected inverter system |
| CN101944746B (en) * | 2010-07-20 | 2013-06-05 | 深圳市红岩电控设备有限公司 | Island detection method, device and system of photovoltaic grid-connected power generating system |
| CN102255329B (en) * | 2011-04-14 | 2013-11-20 | 东南大学 | Island detection method of photovoltaic grid connected system |
| KR101354895B1 (en) * | 2012-06-01 | 2014-01-23 | 엘에스산전 주식회사 | A power monitoring system and a method for displaying information of a power system |
| CN103064035B (en) * | 2013-01-08 | 2015-05-13 | 天津大学 | Active island detection method of multi-distributed power supply tied-grid |
| CN103138268B (en) * | 2013-02-25 | 2015-02-25 | 国家电网公司 | Low-voltage anti-island device of distributed photovoltaic power generation systems |
| CN103323695B (en) * | 2013-05-16 | 2016-01-20 | 国家电网公司 | Anti-island protect test macro automatic loading device and method thereof |
| CN103412207B (en) * | 2013-07-11 | 2015-08-05 | 华北电力大学（保定） | Based on the method for detecting island of photovoltaic grid-connected inverter that negative-sequence current injects |
| CN103645404B (en) * | 2013-12-16 | 2016-03-23 | 辽宁工业大学 | A kind of micro-grid island detection method and detection system |
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