Method for detecting voltage sag based on generalized hyperbolic S-transformation

Abstract

The invention relates to a method for detecting voltage sag based on generalized hyperbolic S-transformation, which comprises the following steps of (1) sampling detected voltage signals; (2) carrying out generalized hyperbolic S-transformation on the sampled signals; (3) calculating a fundamental frequency voltage amplitude value according to an S-model matrix; (4) comparing the fundamental frequency voltage amplitude value with a set voltage sag threshold value, and judging whether voltage sag occurs or not; and (5) extracting a characteristic value if voltage sag occurs, and carrying out detection and analysis on start and stop moments and phase jumps of the voltage sag. Compared with an existing detection method, the method provided by the invention adopts the generalized hyperbolic S-transformation, improvement is carried out on an original hyperbolic window function, and a window width factor and a window width change rate adjustment factor are introduced, thereby being capable of flexibly adjusting the time-frequency resolution, reducing the sensitivity of detection signals for noises, and being capable of accurately detecting the amplitude value, the start and stop moments and the phase jumps of the voltage sag. The method provided by the invention has wide application prospects in fault detection of an electric power system.

Description

technical field [0001] The invention relates to a voltage sag detection method based on generalized hyperbolic S transform, belonging to the field of power quality signal analysis and processing. Background technique [0002] In recent years, with the development of the power industry and high-tech, various highly automated and intelligent modern industrial equipment are widely used in power systems, and their dependence on high-quality power supply is increasing. Power interruptions or voltage dips will affect the normal operation of these sensitive devices. Among various power quality problems, voltage sag is the main factor for abnormal operation of sensitive equipment. It is generally believed that more than 70% of power quality problems are caused by voltage sags. Voltage sag may cause computer program disorder, production process stop, speed regulating device failure and protection equipment malfunction, etc., which not only cause economic losses to users, but may al...

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Problems solved by technology

Although the traditional RMS method and dq transformation method can quickly track the change of voltage amplitude, they cannot accurately locate the start and end moments of voltage sags; discrete wavelet transform can locate sag disturbances, but it is difficult to locate them from The characteristics of the sag amplitude are extracted from the wavelet coefficients; the short-time Fourier transform has the defects that the window type needs to be selected and the window width is fixed; the S transform is the development of the wavelet transform and the short-time Fourier transform, which not only overcomes the two The defect of the former, and the transformation process is lossless and reversible. The hyperbolic S transform has improved the S transform to a certain extent. Its window function is asymmetric and has higher resolution in the high frequency part, but there is still time-frequency resolution. The change mode is fixed, and the disadvantage of being easily affected by noise

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