Control Strategies of a Hybrid Multilevel Converter for Expanding Adjustable Output Voltage Range

This paper proposes a new arrangement and new control strategies for a hybrid multilevel converter, aiming at a high-power high-efficiency converter system being free from harmonic distortion. The strategies enable one to expand the adjustable output voltage range up to 100% by keeping a very low harmonic distortion of the output voltage. The triangular-carrier-based pulsewidth modulation (PWM) and space-vector-based PWM strategies are applied to voltage control. The effectiveness is verified by simulation and experimental results. The proposed hybrid multilevel converter is applicable to medium-voltage networks as a high-power grid-interface converter.