Power Quality Improvement Meeting Important Grid Codes Using Three-Phase Five-Level CHB Inverter With Improved Quarter and Half-Wave Symmetry Based Optimized SHM-PAM

Selective harmonic minimization-pulse amplitude modulation (SHM-PAM) scheme suppresses more number of selected voltage harmonic components of a predefined voltage waveform pattern for a wider range. This article presents formulations of some improved five-level pulse patterns based on both quarter-wave symmetry (QWS) and half-wave symmetry (HWS) with a low number of switching instants using the optimized SHM-PAM scheme to meet the CIGRE WG36-05/EN 50160 and IEC 61000-3-6 grid codes. The switching angles and normalized value of dc voltage sources are calculated by the recently reported dragonfly algorithm based optimization technique. The performance of the proposed schemes has been verified through simulation and experimentation on a three-phase five-level cascaded H-bridge (CHB) inverter. A comparison between the proposed two types of formulations has been carried out based on various aspects, such as waveform quality, dc power conversion capability, and power loss in the power semiconductor devices of the CHB inverter and efficiency. It is observed that QWS formulations exhibit better waveform quality than the HWS formulations sacrificing the efficiency of CHB inverter due to higher switching losses. Moreover, the effectiveness of the proposed schemes has been compared with some prior conventional modulation schemes.