Choice of Frequency Ratio and Its Optimization for PWM Inverter Harmonic Distortion Control

Abstract

In this paper, application of numerical-fuzzy logic to choose frequency ratio for pulse width modulated (PWM) inverter is presented.  The PWM inverter is a naturally sampled bipolar double-edge modulated. The choice of frequency ratio is based on the total harmonic distortion (THD) and impedance scan of a grid. The THD provides information about harmonic distortion limits. The impedance scan provides information about principle harmonic voltage (PHV) in utility grid that is to be mitigated. The spectral model of PWM waveform to realize the significance of choice of frequency ratio, harmonic impedance scan procedure of radial grid, and numerical-fuzzy logic applied for choice of frequency ratio are described in detail. The data for numerical-fuzzy controller implemented using MATLAB is obtained from time-domain simulation of the system using PSCAD/EMTDC. The individual harmonic distortion profile and instantaneous waveform plot for the choice of frequency ratio using this proposed method demonstrates mitigation of PHV and hence minimization of THD. The Shuffled Frog Leap Algorithm (SFLA) based optimization for the choice of frequency ratio for a global minimum of THD is also presented.