A PSO-Based Optimized Hybrid PWM Strategy for a Binary Asymmetric Cascaded H-Bridge Photovoltaic Inverter With Single PV Source Per Phase

This article presents a study on hybridization of nearest level (NL) and carrier-based (CB) pulsewidth modulation (PWM) techniques for a cascaded H-bridge (CHB) multilevel inverter (MLI) with binary asymmetry ratio for photovoltaic (PV) inverter applications. The MLI topology needs one PV source in each phase with the remaining H-bridges being supplied from self-balancing floating capacitors which ensure the topology to remain independent of any closed-loop voltage balancing controller irrespective of the number of H-bridges in cascade. The effect of hybridizing the PWM techniques based on power loss dissipated in the MLI and harmonic contents in its output voltage is thoroughly analyzed for the cases of without and with third-harmonic injection (THI) in its phase voltage waveform. A particle swarm optimization (PSO)-based hybrid PWM strategy is constructed to minimize switching loss of MLI and maintain total harmonic distortion (THD) of its line voltage within grid code standard. The validity and effectiveness of the proposed PWM technique are confirmed on a laboratory-based experimental prototype for the MLI operating under different modulation indices.