Performance Evaluation of SHE-PWM using a Novel Algorithm and SPWM in Cascaded Seven-Level H-Bridge Inverter for Grid-connected Systems

This paper presents a performance evaluation of Selective Harmonic Elimination Pulse Width Modulation (SHE-PWM) using a novel algorithm and Sinusoidal Pulse Width Modulation (SPWM) in cascaded seven-level H-bridge inverter in grid-connected systems. A novel optimization algorithm is introduced to compute optimal switching angles for the selective harmonic elimination method, effectively reducing total harmonic distortion across a range of modulation indices. The algorithm efficiently resolves the nonlinear transcendental equations that link switching angles, harmonic distortion, and the amplitude of the fundamental waveform. Extensive simulations conducted using MATLAB/Simulink on a resistive-inductive load (45 Ω, 0.025 H) over modulation indices from 0.7 to 1.0 reveal that the selective harmonic elimination using a novel algorithm outperforms the sinusoidal pulse width modulation method in minimizing total harmonic distortion. Specifically, at a modulation index of one, selective harmonic elimination achieves a total harmonic distortion of 11.68% compared to 17.94% for the sinusoidal pulse width modulation approach. Furthermore, the proposed algorithm successfully eliminates targeted lower order harmonics while preserving the desired fundamental voltage component, and the lower switching frequency associated with selective harmonic elimination results in reduced switching losses. These findings underscore the potential of optimized selective harmonic elimination for high-power applications where efficiency and waveform quality are important.