A Quarter Wave Symmetry Based Modified Harmonic Minimization Scheme for 3-Phase 7Level Cascaded H-Bridge Multilevel Inverter

In this study, a modified SHM PAM scheme is proposed for a 7-level cascaded H-bridge (CHB) multilevel inverter (MLI), which eliminates all the 5<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> harmonic components of the inverter line voltage while minimizing other lower-order harmonics. In this aspect, a new angular constraint is developed to satisfy four stringent grid code standards using a 7-level quarter wave symmetric voltage waveform. To determine the optimal switching angles and per-unit voltages of the proposed voltage pattern, the fitness function (FF), is formulated with comparatively minimal number of variables; thereby expediting and simplifying the overall computational process. The particle swarm optimization (PSO) algorithm is used to estimate the optimal solutions of the FF. Finally, the applicability of the proposed scheme is validated by MATLABsimulation & experimentation to a CHB MLI setup. An FPGA based controller is used to generate the digital gate pulses of the hardware device.