Stand-alone photovoltaic asymmetrical cascade converter

This paper presents a stand-alone photovoltaic (PV) generation system based on an asymmetric cascade H-bridge (ACHB) converter. The system is composed of two H-bridge converters (A and B) series connected, supplying an ac load. To maximize the number of voltage levels, the dc-link voltage ratio is 3:1. The higher dc-link voltage (converter A) is connected to PV panels, and two options are presented for the lower dc-link voltage (converter B): a battery cluster or a floating capacitor. In addition, two pulsewidth modulation (PWM) strategies are proposed: one is based on phase-shifted carrier (PSC) disposition and the other is based on level-shifted carrier (LSC) disposition. The regulation of the dc-link voltage of converter B is performed with the proposed PWM techniques by changing the power distribution between converters A and B, whereas the dc-link voltage of converter A can be regulated by a feedback controller. Finally, simulation and experimental results are shown for validation purposes.