Hybrid Control of Cascaded H-Bridge Multilevel Converters for Multiple Capacitor Voltage Balancing

Cascaded h-bridge multilevel converters present many benefits such as high modularity, level optimization and low common-mode voltage, but require one independent bidirectional voltage source per h-bridge, increasing cost and reducing reliability. This paper presents a three stage asymmetric multilevel converter using independent power sources in the main h-bridge and floating capacitors in the two auxiliar h-bridges. A hybrid control method is proposed to balance multiple capacitors, combining a fundamental-voltage-control through modulation index and a model predictive control. Simulation results show the feasibility of the proposed hybrid control in steady-state and dynamic operation.