Energy Balance Control of a Cascaded Multilevel Inverter for Standalone Solar Photovoltaic Applications

Abstract

This paper presents a clock phase-shifting (CPS) energy balance control (EBC) method for cascaded half-bridge multilevel inverters in standalone solar photovoltaic (PV) systems. It is based on the conservation of energy in each cascaded unit. By shifting the phase of the clock pulse of each cascaded unit, a staircase-like output voltage is obtained. The CPS EBC not only regulates the staircase-like output voltage of the cascaded multilevel inverters accurately under static conditions, but also suppresses the fluctuations of DC sources and improves its dynamic responses to load steps. Thus, the problems existing in solar PV systems using the cascaded multilevel inverters are avoided. Results obtained from simulations and experiments are presented to verify the feasibility and advantages of the proposed control method.