Negative Harmonics Injection Cuddled Equal Area Criteria Based Selective Harmonic Elimination Pulse Width Modulation Techniques for Multilevel Cascaded Inverters

Abstract

Selective Harmonics Elimination (SHE) technique of power electronic converters can be generally defined as calculation of the optimized switching angles at any desired output (fundamental) voltage component to eliminate a set of preferred lower order harmonic components. This low switching frequency method adds values to Multilevel Inverter (MLI) based systems for the reason that MLI’s have the ability to synthesize waveforms closer to sinusoidal with a better harmonics spectrum. The traditional method for finding the optimized switching angles is by solving the Fourier non-linear transcendental equations of the MLI output voltage and various algorithms like Newton-Raphson (NR) algorithm, Genetic algorithm (GA), Resultant theory, Walsh function etc. are available. This paper proposes a novel approach for performing SHE in MLI working with both equal and unequal dc voltages. The basic principle in which the proposed technique works is a combined effect of equal area criteria and negative harmonics injection techniques. The major advantage is that the proposed methodology comprises of four simple equations for performing SHE instead of solving the complex non-linear transcendental equation. The computational efficiency of this algorithm is evaluated through comparison with traditional NR and GA. In addition, a prototype of three-phase seven-level cascaded MLI is designed through which several informative results are investigated and the effectiveness of the proposed algorithm is proved.