CFT based optimal PWM strategy for three phase inverter

Selective Harmonic Eliminated Pulse Width Modulation (SHEPWM) techniques necessitate the solution of non-linear transcendental equations for achieving optimal PWM strategy. Online solution of these equations is very difficult and the conventional method is to store the offline prepared optimal switching angles in memory, which are to be recalled for online generation of PWM waveforms. The need to achieve continuous voltage and frequency control, especially for AC machines, has imposed large memory requirements and computation time for PWM systems. This paper proposes an effective online method to arrive optimal PWM switching angles based on Curve Fitting Technique (CFT) for three phase inverters. Polynomial functions for optimal switching angles are generated using CFT in MATLAB. The correctness and harmonic performance of the proposed method is verified by comparing the results with the Newton-Raphson (N-R) iterative method.

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