Phase deviation based auto-disturbance rejection isolated island detecting method
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A technology of island detection and phase shift, applied in the phase angle between voltage and current, measurement device, measurement of electrical variables, etc., to avoid secondary islanding and reduce detection blind spots.
Inactive Publication Date: 2013-02-06
XI AN JIAOTONG UNIV
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[0004] The purpose of the present invention is to propose an active disturbance rejection islanding detection algorithm based on phase offset, so as to ensure fast and effective detection of the islanding phenomenon when secondary islanding occurs, and to prevent misjudgment due to the influence of system transient disturbances and other defects
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Embodiment 1
[0054] For a parallel RLC load, if its resonant frequency f 0 Equal to grid voltage frequency f grid , which is a resistive load, there are R = 48.4Ω, L = 6mH, C = 1700μF. At this time, the change of the voltage frequency at the PCC before and after the occurrence of islanding by the ADRC islanding detection method is shown in the attached figure 2 shown. It can be seen that even if islanding occurs under the worst conditions, the active disturbance rejection islanding detection method can quickly and effectively detect the islanding.
Embodiment 2
[0056] If the parallel RLC load is an inductive load at the grid voltage frequency, that is, f 0 > f grid , the selected load parameters are: R=48.4Ω, L=6mH, C=1400μF. At this time, the change of the voltage frequency at the PCC before and after the occurrence of islanding by the ADRC islanding detection method is shown in the attached image 3 shown. It can be seen that if the load is an inductive load, when islanding occurs, under the action of the inverter output current phase angle control function, the voltage frequency at the PCC will shift upward until it exceeds the range set by the threshold.
Embodiment 3
[0058] If the parallel RLC load is a capacitive load at the grid voltage frequency, that is, f 0 grid , the selected load parameters are: R=48.4Ω, L=6mH, C=4700μF. At this time, the ADRC island detection method changes the voltage frequency at the PCC before and after the island occurs, as shown in the attached Figure 4 shown. It can be seen that if the load is a capacitive load, the voltage frequency at the PCC will shift downward under the action of the phase angle control function of the inverter output current when islanding occurs, until it exceeds the range set by the threshold.
[0059] Implementation Effect:
[0060] From the analysis of the above simulation results, it can be seen that once the islanding occurs, the voltage frequency at the PCC shifts toward the resonance frequency, and the islanding detection method proposed in the present invention can confirm the occurrence of the islanding in the next cycle after the islanding occurs. In addition, islanding is...
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Abstract
The invention discloses a phase deviation based auto-disturbance rejection isolated island detecting method, which realizes periodic disturbance on the output current of an inverter by constructing an output current phase angle control function of the inverter so as to ensure that the voltage frequency of the position of a point of common coupling (PCC) deviates after the isolated island happens, and the occurrence of an isolated island phenomenon can be ensured to be effectively detected in time. The phase angle control function of the output current of the inverter consists of two parts, wherein one part is a homeostatic control function theta 0[k] which mainly plays roles in destroying a stable running point possibly existing in the system and ensuring effectiveness of disturbance, while the other part is a main function of the phase angle of the output current of the inverter which plays roles in ensuring that the method can effectively detect the isolated island when a secondary isolated island happens, and avoiding misjudgment caused by transient disturbance influence of the system, so that the normal operation of the system can be ensured. Therefore, compared with the prior art, the isolated island detecting method not only can avoid misjudgment caused by the effect of transient disturbance, and ensure the operation security of the system, but also can ensure that the isolated island can be quickly and accurately detected when the isolated island happens in an extremely hard condition, and greatly reduce the dead zone of detection.
Description
technical field [0001] The invention relates to an islanding detection method of a distributed grid-connected power generation system, in particular to an active disturbance rejection islanding detection method based on a phase offset. Background technique [0002] With the increasingly serious energy shortage and environmental problems, solar energy, wind energy, etc. The inevitable trend of utilization. While the distributed grid-connected power generation system meets people's electricity demand, it also brings many safety hazards and accidents to the power grid, among which the safety problems caused by isolated islands are also particularly prominent. The so-called island phenomenon means that when the large power grid loses power, the distributed grid-connected power generation system connected to it fails to detect the power outage in time and separates from the large power grid, and continues to provide power to local loads, thus forming a self-sufficient power supp...
Claims
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