Islanding Detection Method Based on Pattern Recognition of Harmonic Impedance Characteristic Function

Abstract

The invention discloses a method for islanding detection based on harmonic impedance characteristic function pattern recognition and relates to the technical field of electrical property testing methods. The method comprises a step (1) of collecting voltage at a public coupling point and an access current of a distributed type grid-connected power generation system when the distributed type grid-connected power generation system is in an islanding state and a non-islanding state; a step (2) of establishing a harmonic impedance characteristic function phi(k) according to a voltage value and a current value collected in the step (1), and obtaining a characteristic vector space; a step (3) of performing training on a learning sample through pattern recognition, and obtaining the distinguishing capability of the distributed type grid-connected power generation system in the islanding state and the non-islanding state. According to the method, on the premise that electric energy quality is not affected, islanding is accurately detected and islanding protection is performed so as to reduce or even eliminate an islanding detection blind area.

Description

technical field [0001] The invention relates to the technical field of testing methods for electrical properties, in particular to an islanding detection method based on harmonic impedance characteristic function pattern recognition. Background technique [0002] With the global energy crisis and the concern of the world on the global warming, the distributed grid-connected power generation system has been greatly developed. However, there are still many core technical problems to be solved urgently in the distributed grid-connected power generation system, especially the detection of islanding phenomenon. The so-called isolated island phenomenon means that in the distributed grid-connected power generation system, when the grid power supply trips due to a fault accident or power outage maintenance, the distributed grid-connected power generation system at each user end fails to detect the power failure state in time and cuts itself off from the mains. Finally, a self-suppl...

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Problems solved by technology

Active island detection needs to add a disturbance to the system, and use the corresponding changes in system voltage, frequency, impedance, etc. caused by the disturbance to detect the occurrence of islands. Its advantage is that it can effectively reduce the non-detectable zone (NDZ), but it will affect the power. the quality of

The existing passive islanding detection mainly detects the occurrence of islanding by detecting variables such as the terminal voltage and current signal of the grid-connected device. The advantage is that the detection method is easy to implement and has no impact on the power quality of the system. The disadvantage is that the threshold is difficult to determine and There is a large detection blind spot

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