Improved EMD decomposition-based draft tube pressure pulsation comprehensive evaluation method

Abstract

The invention provides an improved EMD decomposition-based draft tube pressure pulsation comprehensive evaluation method, and relates to fault feature extraction and state evaluation of pressure pulsation signals of draft tubes of water wheels. According to the method, multi-point pressure pulsation signal features of draft tubes of water wheels are extracted by utilizing an improved empirical mode decomposition (EMD) method, index energy and a multi-scale feature entropy theory, a comprehensive evaluation index is established, and the index is used for evaluating the pressure pulsation degrees of the draft tubes. Though an EMD interval threshold value-based denoising method, background noise interference in the pressure pulsation signals of the draft tubes are removed, intrinsic mode functions IMP expressing different time scales are decomposed through EMD, effective components are extracted by utilizing a correlation coefficient theory, the index energy (IER) is selected to serve as feature parameters so as to carry out feature extraction on the effective components, and a mapping relationship between pressure pulsation energy and a system state confusion degree is established on the basis of the multi-scale feature entropy value theory, so that the pressure pulsation states of the draft tubes are comprehensively evaluated from a new perspective.

Description

technical field [0001] The invention relates to the technical field of signal processing and fault diagnosis, in particular to signal processing of hydraulic turbine draft tube pressure pulsation and monitoring of its vibration state, in particular to a comprehensive evaluation method for draft tube pressure pulsation based on an improved EMD decomposition method. Background technique [0002] A hydroelectric unit is a complex and special rotating machine. With the continuous increase of its installed capacity, the equipment of the unit is more complicated. When the operating condition deviates from the optimal area, the flow velocity at the outlet of the runner blades has a large component in the circumferential direction. After the component enters the draft tube, it will form a relatively obvious circulation in the draft tube, and then develop into a Rotating vacuum vortex. The eccentric vortex will cause hydraulic instability in the flow channel of the turbine, and pres...

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Problems solved by technology

[0005] In view of the strong background noise interference of the draft tube pressure pulsation signal of the hydraulic turbine and the nonlinear and time-varying characteristics of the pressure pulsation signal, the present invention proposes a new multi-scale state evaluation method for the pressure pulsation of the draft tube of the hydraulic turbine, which is based on the improved empirical mode decomposition Draft tube pressure fluctuation evaluation method based on multi-scale characteristic entropy theory and index energy characteristics

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