Study On DSP-Controlled Switching No-Load Power Transformer

Owing to the fact that the power system scope expands, the transformer quantity in the power system is more and more. Thus the operation times to Energize the no-load transformer also largely grows in number. Transformer inrush currents are high-magnitude, harmonic-rich currents generated when transformer cores are driver into saturation during energization. These currents have undesirable effects, including protective relay misoperation, imposed sever mechanical stressed on the transformer windings and reduced power quality on the system. Whether effectively restraining the inrush current becomes the key problem of transformer protection.Therefore this thesis researches the transformer structure, principle and the transient state during energizing idle power transformer. Afterwards I put forward my own method which simultaneous applies controlled switching technology and signal processing technology to energizing No-load transformer. The major work and the conclusion are as follows:Firstly, this dissertation concretely analyses and studies the transformer core flux transient state, then we can know that the inrush current amplitude value relates with the phase angle of energization and transformer windings resistance. Based on this conclusion, corresponding closing strategies are proposed and applied in restraining inrush currents according as no-load transformer different residual core flux models.Secondly, On the aspect of the signal processing course, adopting Interpolation Discrete Fourier Transform (IDFT) technique to process data. Then, we can accurately tell apart the radix-frequency signal which includes real-frequency,amplitude value as well as the initial phase angle of sampling begin moment. According as these parameters, the energizing time can be educed.Lastly, according to differently residual core flux models, detailed MATLAB/Simulation about some modules' function are made, which indicates that the controlled switching method based on DSP can be used to potentially eliminate the inrush currents when energizing No-load power transformer.