Abstracto

?HARMONIC REDUCTION IN AC DRIVES AND IT?s WAVELET ANALYSIS?

Chetan Bhale, K.B. Porate

Variable speed AC drives are finding their place in all types of industrial and commercial loads. This work covers the current source converter technologies, including pulse width-modulated current-source inverters (CSIs) and in addition, this also addresses the present status of the direct converters & gives an overview of the commonly used modulation schemes for VFD systems. The proposed work flow is that to work with the simulation of three phase PWM Current Source Inverter fed Induction Motor (CSI-IM) drive systems using Matlab/Simulink simulation software. This work primarily presents a unified approach for generating pulse width-modulated patterns for three-phase current-source rectifiers and inverters (CSR/Is) that provides unconstrained selective harmonic elimination and fundamental current control. This conversion process generates harmonics in the motor current waveform. This project deals with the analysis of motor current harmonics using FFT analysis and use of filter for mitigating them for smooth operation of motor. The filter used for reduction of harmonics is passive filter. The filter is such it reduces only the 5th & 7th order harmonics. Thus the analysis of motor current harmonics is done firstly without filter & then it has been compared with the results after the addition of filter. It is found that the 5th & 7th order harmonics has reduced considerably. Also the project deals with study of signal in the form of motor current and performing Wavelet Analysis. The Wavelet Analysis is totally different approach than the FFT Analysis. Wavelet Analysis is done by two ways one by using wavelet programming & by using graphical method. Wavelet programming is done by using M-file where program is written for analysis of motor current with & without filter & then results are compared. The only focus of this research work is an improvement over existing techniques.