CN102590663A - Improved intermittent reactive power disturbance island detection method - Google Patents
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Abstract
The invention discloses an improved intermittent reactive power disturbance island detection method. The method applies periodic reactive power disturbance on an inverter controller, and each reactive power disturbance period is divided into reactive power disturbance time and non-reactive power disturbance time. At the starting time of each reactive power disturbance period, the voltage frequency detected by a frequency detection module is bestowed on a reactive power disturbance quantity calculating module, the minimum reactive power disturbance quantity required for the period is then calculated by the reactive power quantity calculating module, the reactive power disturbance quantity can ensure that the frequency of a common coupling point deviates out of an allowed range when an island phenomenon occurs, an intermittent reactive power disturbance signal module generates an intermittent reactive power disturbance signal of the period according to the calculated reactive power disturbance quantity, and periodic intermittent reactive power disturbance is applied on the inverter controller so as to achieve the purpose of detecting the island. According to the improved intermittent reactive power disturbance island detection method, the island phenomenon can be timely and effectively detected, the reactive power disturbance quantity required for the island detection can be reduced, and the influence on the grid-tied power factor is smaller.
Description
Technical field
The present invention relates to the island detection technology in distributed generation system and the combining inverter application, especially a kind of no improved intermittent reactive power disturbance island detection method.
Background technology
Because the quick consumption of non-renewable energy resources such as fossil energy and environmental problem is serious day by day, the new forms of energy distributed power generation has received gradually widely and having paid close attention to.In the new forms of energy distributed power generation, wind energy, photovoltaic, the electric energy that fuel cell etc. produce is transformed into qualified electric energy through power converter and is connected to the grid.Combining inverter can carry out conversion and carry out quality of power supply control as the interface between new forms of energy and the electrical network electric energy.Usually distributed generation system comprises single-phase or three-phase grid-connected inverter, isolating switch, local load and public electric wire net.Combining inverter is connected with public electric wire net through isolating switch with local load, and tie point is point of common coupling (PCC).When external power grid breaks down and when breaking off, combining inverter and local load break away from electrical network and form the electric network composition that the part has TRT, be referred to as isolated island.The reason that isolated island produces is a lot, comprises that mainly the circuit that electric network fault, isolating switch damage and disaster etc. cause destroys.The generation of isolated island generally is unpredictable, may bring distributed power generation device and local load because of voltage or the frequency damage that causes out of control, even personal safety is constituted certain threat.So distributed generation system must adopt a kind of effective island detection method to detect the generation of isolated island.
Island detection method is divided into three types usually: (1) passive island detection method; (2) active island detection method; (3) PERCOM peripheral communication island detection method.Usually weigh the validity of island detection method with non-detection zone (NDZ), what non-detection zone was represented is specific island detection method can not detect island state under given local load characteristic condition zone.
System's electrical parameters such as the voltage magnitude of passive island detection method through detecting point of common coupling, frequency, phase place harmonic are judged the generation of isolated island.Cross/under-voltage method (OVP/UVP), ultra/under-frequency method (OFP/UFP) is the most frequently used passive island detection method.Cross/whether the under-voltage method exceeds the generation that the line voltage allowed band is judged isolated island through detecting the point of common coupling voltage magnitude, and whether ultra/under-frequency method exceeds the generation that the mains frequency allowed band is judged isolated island through detecting the point of common coupling electric voltage frequency.GB/T 19939-2005 (requirement of photovoltaic system interconnection technology) regulation mains frequency can not exceed the scope of 49.5Hz to 50.5Hz.Passive island detection method is realized simple, does not influence and network electric energy quality, but meritorious with reactive power and load consumption meritorious and idle approaching the time when inverter output, passive island detection method possibly lose efficacy, and fell into non-detection zone.
Active island detection method is through combining inverter point of common coupling to be introduced disturbance, impels the electrical parameter (comprising voltage magnitude, frequency etc.) that the back system takes place isolated island to exceed allowed band, thereby judges the generation of isolated island.Active island detection method comprises frequency departure method (AFD), sliding formwork frequency deviation method (SMS),
SandiaFrequency deviation method, reactive power method of perturbation (RPV) etc.Active island detection method reduces even eliminates non-detection zone, simultaneously can to and network electric energy quality certain influence is arranged.Traditional intermittent reactive power perturbation motion method is the just idle disturbance and negative idle disturbance of in a disturbance cycle, introducing constant basis, can eliminate non-detection zone.But traditional reactive power perturbation motion method can be introduced bigger disturbance quantity to the reactive power of combining inverter output, reduces the inverter output power factor, exists bigger defective.
The PERCOM peripheral communication detection method is through setting up the generation that communication contact detects isolated island between electrical network and distributed power generation device, still too high cost has limited the application of PERCOM peripheral communication detection method.
Summary of the invention
The present invention is directed to the deficiency of prior art, proposed a kind of fundamental purpose and be to propose a kind of improved intermittent reactive power disturbance island detection method.This method detects the point of common coupling electric voltage frequency through the initial time in the idle disturbance cycle, calculates the minimum idle disturbance quantity of required introducing of this cycle, thereby successfully detects the generation of isolated island.
A kind of improved intermittent reactive power disturbance alone island detection system comprises isolated island test main circuit, frequency detection module, reactive power perturbation control loop, circuit control device and frequency determination module; Isolated island test main circuit comprises single-phase/three-phase combining inverter, the RLC load of modulating based on PWM, isolating switch and the electrical network that is used to connect electrical network; Frequency detection module is used for per sampling period detection point of common coupling electric voltage frequency; Circuit control device is used for the reactive power amount of control inverter output appointment; The frequency determination module is used to judge whether isolated island takes place; Intermittent reactive power perturbation control loop comprises reactive power disturbance quantity computing module and intermittent reactive power disturbing signal module.
This method specifically detects step and comprises:
Step 2, at the initial time of each idle disturbance cycle T, reactive power disturbance quantity computing module is according to frequency values that this moment, frequency detection module was provided
f, calculate the idle disturbance quantity that inverter should be exported in the idle disturbance time in this cycle
Q, when
fDuring≤50Hz, this cycle exports idle disturbance quantity and is:
When
f>During 50Hz, export idle disturbance quantity and be:
Wherein
PBe the inverter active power of output,
Q f Be the load quality factor,
f Min Be the minimum value that mains frequency allowed,
f Max Be the maximal value that mains frequency allowed;
Simultaneously, the frequency values that frequency detection module records is judged the frequency values of point of common coupling voltage by the frequency determination module, if frequency, is then assert electrical network and combining inverter disengagement at this moment greater than 50.5Hz or less than 49.5Hz, isolated island takes place.
Beneficial effect: the island detection method simple possible that the present invention proposes; Compare traditional reactive power disturbance island detection method; Only need in software, to increase a reactive power perturbation control loop; Before exporting idle disturbance in phase weekly, the point of common coupling electric voltage frequency that obtains according to frequency detection module calculates the reactive power disturbance quantity in this cycle, and the idle disturbance quantity of gained is when isolated island, to impel squint out the minimum value of frequency allowed band of point of common coupling electric voltage frequency.Thereby compare with traditional intermittent bilateral reactive power perturbation motion method, the phase only need be introduced monolateral idle disturbance weekly, and can idle disturbance quantity be reduced.Finally make grid-connected system obtain higher be incorporated into the power networks power factor and effective island detection ability; The present invention is applicable to new forms of energy distributed generation systems such as sun power, wind-force, fuel cell; The generation that detects combining inverter isolated island phenomenon of ability success; Satisfy the island detection time that GB requires, and less to the influence of the power factor that is incorporated into the power networks.
Description of drawings
The improved intermittence of Fig. 1 is idle, and the disturbance alone island detection system constitutes synoptic diagram;
The improved intermittent reactive power perturbation motion method output reactive power sequential chart of Fig. 2;
The improved intermittence of Fig. 3 is idle disturbance island detection method implementing procedure figure.
Embodiment
Below in conjunction with accompanying drawing technical scheme of the present invention further is discussed in more detail.
As shown in Figure 1, a kind of improved intermittent reactive power disturbance alone island detection system comprises isolated island test main circuit, frequency detection module 5, reactive power perturbation control loop, circuit control device 8 and frequency determination module 9; Isolated island test main circuit comprise based on the PWM modulation single-phase or three-phase grid-connected inverter 1, RLC load 2, be used to connect the isolating switch 3 and the public electric wire net 4 of electrical network; Frequency detection module 5 is used for per sampling period detection point of common coupling electric voltage frequency; Circuit control device 8 is used for the reactive power amount of control inverter output appointment; Frequency determination module 9 is used to judge whether isolated island takes place; Intermittent reactive power perturbation control loop reactive power disturbance quantity computing module 6 and intermittent reactive power disturbing signal module 7.
This method specifically detects step and comprises:
Step 2 is at the initial time (t of each idle disturbance cycle T
0), reactive power disturbance quantity computing module 6 is according to frequency values that this moment, frequency detection module 5 was provided
f, calculate the idle disturbance quantity that inverter should be exported in the idle disturbance time in this cycle
Q, when
fDuring≤50Hz, this cycle exports idle disturbance quantity and is:
When
f>During 50Hz, export idle disturbance quantity and be:
Wherein
PBe the inverter active power of output,
Q f Be the load quality factor,
f Min Be the minimum value that mains frequency allowed,
f Max Be the maximal value that mains frequency allowed;
Simultaneously, the frequency values that frequency detection module records is judged by the frequency values of 9 pairs of point of common coupling voltages of frequency determination module; If frequency is greater than 50.5Hz or less than 49.5Hz; And continue 1 power frequency period, then assert electrical network and combining inverter disengagement at this moment, isolated island takes place.
The sequential that the inventive method output is idle is with reference to Fig. 2, and principle is following:
Combining inverter output reactive power is periodically variable, and each reactive power disturbance cycle T is divided into idle disturbance time T
1With non-idle disturbance time T
2, in idle disturbance time T
1In, the idle disturbance quantity of output is a fixed value
Q, non-idle disturbance time T
2The idle disturbance quantity of interior output is zero.As shown in Figure 2, the expression formula that can get inverter output reactive power
is:
Consider that the island detection time can not be greater than 2s; Set the disturbance cycle
; The idle disturbance time
, the quiescent interval
.Above embodiment is merely explanation technological thought of the present invention, can not limit protection scope of the present invention with this, and is every according to design procedure of the present invention, and any modification to time parameter and idle parameter are made all falls within the protection domain of the present invention.
The inventive method workflow diagram is as shown in Figure 3, and principle is following:
Each sampling period gets into interrupt routine, and frequency detection module detects the frequency of point of common coupling voltage, carries out island state by the frequency determination module and judges.Concrete decision method is: frequency detection module obtains the frequency of point of common coupling voltage; If this frequency is greater than 50.5Hz or less than 49.5Hz; It is unusual to think that electrical network takes place; If mains frequency is in ERST in continuous 1 power frequency period always, assert that then isolated island takes place, the isolated island protection module is closed inverter.If this moment, mains frequency did not exceed allowed band, the circuit control device operate as normal.Counter is the power frequency period counter in the process flow diagram, and initial value is 0, and every at a distance from 20ms, count value adds 1.The cycle T that can make intermittent idle disturbance is 2s, and when then counter count down to 100 cycles, set was 0 again, exported idle disturbance time T
1Be decided to be 200ms, promptly counter is 0 to 9 o'clock, export idle disturbance, and counter is at 10 to 99 o'clock, does not export idle disturbance.The PCC dot frequency is relevant before the idle disturbance quantity of the intermittent reactive power method of perturbation that the present invention proposes and the idle disturbance, thus when counter is 0, the general at this moment the PCC dot frequency obtain and compose to
f, according to
fSize can calculate the idle disturbance quantity of required minimum of this cycle with different formula
Q, when counter is 0 to 9, exports idle disturbance quantity and do
Q, when counter was 10 to 99, exporting idle disturbance quantity was 0, when counter count down to 100 cycles, set was 0 again.Through process flow diagram shown in Figure 3, can obtain reactive power output timing as shown in Figure 2, and effectively detect the generation of isolated island.
Claims (1)
1. improved intermittent reactive power disturbance island detection method, system comprises isolated island test main circuit, frequency detection module, reactive power perturbation control loop, circuit control device and frequency determination module; Isolated island test main circuit comprises single-phase or three-phase grid-connected inverter, the RLC load of modulating based on PWM, isolating switch and the public electric wire net that is used to connect electrical network; Frequency detection module is used for per sampling period detection point of common coupling electric voltage frequency; Circuit control device is used for the reactive power amount of control inverter output appointment; The frequency determination module is used to judge whether isolated island takes place; Intermittent reactive power perturbation control loop comprises reactive power disturbance quantity computing module and intermittent reactive power disturbing signal module, it is characterized in that this method specifically detects step and comprises:
Step 1, in each sampling period, frequency detection module detects the electric voltage frequency of point of common coupling;
Step 2, at the initial time of each idle disturbance cycle T, reactive power disturbance quantity computing module is according to frequency values that this moment, frequency detection module was provided
f, calculate the idle disturbance quantity that inverter should be exported in the idle disturbance time in this cycle
Q, when
fDuring≤50Hz, this cycle exports idle disturbance quantity and is:
When
f>During 50Hz, export idle disturbance quantity and be:
Wherein
PBe the inverter active power of output,
Q f Be the load quality factor,
f Min Be the minimum value that mains frequency allowed,
f Max Be the maximal value that mains frequency allowed;
Step 3, intermittent reactive power disturbing signal module is according to idle disturbance quantity
QThe intermittent reactive power disturbing signal in this cycle of generation, each reactive power disturbance cycle T is divided into idle disturbance time T
1With non-idle disturbance time T
2, in idle disturbance time T
1In, the idle disturbance quantity of output is a fixed value
Q,
QFor reactive power disturbance quantity computing module calculates the idle disturbance quantity of gained, non-idle disturbance time T according to this disturbance cycle initial time electric voltage frequency
2The idle disturbance quantity of interior output is zero;
Step 4, circuit control device sends intermittent reactive power according to the intermittent reactive power disturbing signal control inverter that generates; The frequency values that frequency detection module records is judged the frequency values of point of common coupling voltage by the frequency determination module, if frequency, is then assert electrical network and combining inverter disengagement at this moment greater than 50.5Hz or less than 49.5Hz, isolated island takes place.
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Cited By (9)
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| CN102830312A (en) * | 2012-08-29 | 2012-12-19 | 江苏兆伏新能源有限公司 | Islanding detection method of grid-connected inverter |
| CN102841279A (en) * | 2012-08-31 | 2012-12-26 | 天津大学 | Micro-grid island detection method |
| CN103257298A (en) * | 2013-05-14 | 2013-08-21 | 合肥工业大学 | Grid-connected inverter island detection method based on parameter adaptive Sandia frequency shift (SFS) |
| CN103645416A (en) * | 2013-08-30 | 2014-03-19 | 天津大学 | Microgrid non-destructive island detection method based on adaptive reactive disturbance |
| CN103728504A (en) * | 2012-10-10 | 2014-04-16 | Abb公司 | Method for detecting islanding operation of distributed power generator |
| CN103941118A (en) * | 2014-03-26 | 2014-07-23 | 中国科学院电工研究所 | Island detecting method for photovoltaic power generation grid-connected inverter trunking system |
| CN106019010A (en) * | 2016-05-23 | 2016-10-12 | 南昌大学 | Mixed island detection method based on combination of slide mode frequency shift method and passive method |
| US9520819B2 (en) | 2014-02-28 | 2016-12-13 | General Electric Company | System and method for controlling a power generation system based on a detected islanding event |
| CN112782501A (en) * | 2020-12-02 | 2021-05-11 | 合肥工业大学 | Parameter-adaptive improved active frequency shift type island detection method |
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Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102830312A (en) * | 2012-08-29 | 2012-12-19 | 江苏兆伏新能源有限公司 | Islanding detection method of grid-connected inverter |
| CN102830312B (en) * | 2012-08-29 | 2014-11-05 | 江苏兆伏新能源有限公司 | Islanding detection method of grid-connected inverter |
| CN102841279A (en) * | 2012-08-31 | 2012-12-26 | 天津大学 | Micro-grid island detection method |
| CN102841279B (en) * | 2012-08-31 | 2014-10-15 | 天津大学 | Micro-grid island detection method |
| CN103728504A (en) * | 2012-10-10 | 2014-04-16 | Abb公司 | Method for detecting islanding operation of distributed power generator |
| US9494637B2 (en) | 2012-10-10 | 2016-11-15 | Abb Oy | Method for detecting islanding operation of distributed power generator |
| CN103257298B (en) * | 2013-05-14 | 2015-08-26 | 合肥工业大学 | Based on the combining inverter island detection method of parameter adaptive Sandia frequency deviation method |
| CN103257298A (en) * | 2013-05-14 | 2013-08-21 | 合肥工业大学 | Grid-connected inverter island detection method based on parameter adaptive Sandia frequency shift (SFS) |
| CN103645416A (en) * | 2013-08-30 | 2014-03-19 | 天津大学 | Microgrid non-destructive island detection method based on adaptive reactive disturbance |
| US9520819B2 (en) | 2014-02-28 | 2016-12-13 | General Electric Company | System and method for controlling a power generation system based on a detected islanding event |
| CN103941118A (en) * | 2014-03-26 | 2014-07-23 | 中国科学院电工研究所 | Island detecting method for photovoltaic power generation grid-connected inverter trunking system |
| CN106019010A (en) * | 2016-05-23 | 2016-10-12 | 南昌大学 | Mixed island detection method based on combination of slide mode frequency shift method and passive method |
| CN112782501A (en) * | 2020-12-02 | 2021-05-11 | 合肥工业大学 | Parameter-adaptive improved active frequency shift type island detection method |
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