An islanding detection method based on multi-band harmonic voltage and frequency

Abstract

The invention discloses an island detection method based on multi-frequency-band harmonic voltage and frequency, and belongs to the technical field of photovoltaic power generation systems. An islandis determined when an action condition is satisfied since a harmonic voltage rises and the frequency is deviated at a certain degree after the island. Through adoption of the island detection method,misjudgment can be avoided. Moreover, the harmonic voltage is considered, so that wrong frequency judgment is prevented, and a relatively small frequency action threshold can be set. Thus, the sensitivity is increased; the detection blind zone is reduced; and the problems in independent use of over / under-frequency detection and harmonic detection methods are solved.

Description

technical field [0001] The invention belongs to the technical field of photovoltaic power generation systems. More precisely, the invention relates to an islanding detection method based on multi-band harmonic voltage and frequency. Background technique [0002] The island effect refers to the grid-connected photovoltaic power generation system is disconnected from the grid due to grid failure or maintenance, forming an isolated island where the photovoltaic power generation system supplies power to the load, such as figure 1 shown. The occurrence of isolated islands will bring a series of hazards. If the isolated island system does not have the ability to adjust voltage and frequency, the voltage and frequency in the isolated system may fluctuate greatly, causing damage to the equipment; when the isolated island system is connected to the grid again, the photovoltaic The power generation device of the power generation system may not be synchronized with the power grid, whi...

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Problems solved by technology

[0003] Among the common island detection methods, the over / under frequency and over / under voltage island detection methods have relatively large detection blind spots, and cannot detect islands in a timely and effective manner. In addition, when the frequency of the system is low, the anti-islanding over\underfrequency criterion is easy to remove photovoltaics by mistake. At this time, the power grid needs the power support of the power supply most. Worse, even lead to large-scale power outages; harmonic island detection method detection blind area is small, but with the power electronic equipment more and more widely used in the power system, and the nonlinear load in the power grid, resulting in harmonic pollution in the power grid Larger, the existence of background harmonics in the power grid cannot be ignored, which will cause the detection method of harmonic islands to malfunction. If there is a relatively large threat, the islanding detection method should be avoided to remove the photovoltaic power generation system by mistake

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