Optimized control of modulation strategy for hybrid H-bridge cascaded multilevel inverter

To improve the operational performance of hybrid H-bridge cascaded multilevel inverter, a hybrid modulation strategy with staggered and phase-shifted saw-tooth carriers is proposed. The complicated hybrid topology is converted into the topology with well-known modulation strategy and modulated by the recomposed modulation wave. It makes full use of the freedoms of the modulation wave and injects the special hybrid components into the three-phase sine wave for optimized control, which ensures the quality of output line voltage though there is no phase voltage PWM modulation within one third of fundamental period. The optimized control not only brings the increase of 15.5% in DC voltage utilization and the decrease of 1/3 in switching number of high frequency power switch, but also enhances the operating performance of inverter system. Experimental results verify its feasibility and validity.