Capacitor Voltage Balancing in Hybrid Cascaded Multilevel Inverter Using Genetic Algorithm at Higher Modulation Indices

In this paper a three-phase, eleven level hybrid cascaded multilevel inverter (HC-MLI) synthesizing an eleven-level output voltage using two dc sources, a precharged capacitor and twelve switches for higher modulation indices is proposed. Genetic algorithm (GA) has been used to compute all the switching angles of the proposed eleven level HC-MLI for eliminating specified odd harmonics (5th, 7th, 11th and 13th) from the output voltage. In the proposed GA optimized HC-MLI, capacitor voltage balance is ensured even at higher modulation indices by utilizing the redundant switching states available at different switching instances. A $d-q$ synchronous reference-frame-based controller has been used in the proposed HC-MLI for regulating both sensed capacitor voltage and ac output voltage. The performance of the proposed three phase, eleven level HC-MLI has been verified through simulation and experimentation on a 1.5-kW prototype using closed-loop control.