Island detection method based on binary tree complex wavelet transformation

Abstract

The invention provides an island detection method based on binary tree complex wavelet transformation, and belongs to the field of electric power systems. The island detection method comprises the following steps of acquiring control variables of a three-phase voltage type inverter, and establishing a PQ decoupling control mathematical model of a grid-connected inverter based on the acquired control variables; acquiring electrical change characteristics of a public connection point of a microgrid island under a power matching condition according to the established PQ decoupling control mathematical model; extracting voltage and current harmonic signals at the common connection point by means of a wave trap, decomposing the voltage and current harmonic signals based on binary tree complex wavelet transformation to construct a characteristic vector corresponding to the micro-grid; and improving a support vector machine on the basis of a support vector selection and genetic algorithm, andadopting the improved support vector machine to identify the island state of the microgrid. By virtue of improvement of the support vector selection and genetic algorithm, damage of the active detection method to the electric energy quality can be eliminated, and the problem of detection blind areas existing in the traditional passive detection method also can be solved.

Description

technical field [0001] The invention belongs to the field of power systems, in particular to an island detection method based on binary tree complex wavelet transform. Background technique [0002] Based on the consumption rate of fossil energy and the proven energy reserves in 2016, the usable life of the remaining oil, coal and natural gas reserves in the world is 50 years, 114 years and 52 years respectively. These fossil energy resources, which human beings rely on for long-term survival, are facing the danger of depletion at an accelerated rate. [0003] Major countries in the world have realized that in order to promote the sustainable development of the world economy and resolve the severe energy crisis, it is necessary to intensify the development of renewable energy. The Distributed Generation (DG) system and the microgrid composed of wind power, photovoltaic power generation, hydropower and other renewable energy sources as micro-power sources are becoming a resea...

AI Technical Summary

Problems solved by technology

If the DG island state cannot be detected in time and the corresponding control strategy adjusted, the unplanned island may cause serious hazards such as power quality degradation, damage to electrical equipment, and harm to maintenance personnel.

[0005] Researchers at home and abroad have done extensive research on the islanding detection technology of microgrids, and have successively proposed many islanding detection methods such as passive voltage and frequency detection methods, active even-order harmonic injection methods, and negative-sequence component positive feedback methods. Algorithms, but there are more or less theoretical or application deficiencies, such as not considering the harmonic interference brought by nonlinear loads, passive detection algorithms have detection blind spots when power matching, active detection algorithms have damage to power quality, and Some algorithms are complex and difficult to apply in practice, etc.

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