Single phase cascaded multilevel photovoltaic sources for power balanced operation

Abstract

Recent developments and researches on cascaded H-bridge multilevel inverters (MLI) have led to its application for rooftop photovoltaic (PV) micro inverters feeding isolated loads. The topology provides transformer less operation where separate DC links at each bridge are fed from individual PV units. The traditional control techniques using battery supported PV panels lead to non uniform operation and utilization of each H-bridge, where some bridges are under high stress as compared to others. This paper presents control techniques which will levels the utilization and storage of power generated by PV panels of same capacity and same size of battery connected at each level. The control method utilizes rotation policy for operation of each bridge at each level in three fundamental cycles, to enhance both the life time of battery, H-bridges and PV panels used. PV units are integrated with incremental conductance (IC) based MPPT charge controllers to extract maximum power at all time of operation. A MATLAB based simulation has been carried out and various waveforms are analyzed. The presented results shows the effectiveness of the proposed scheme in power balanced operation of each panel, battery and the hardware for proper resource utilization with enhanced efficiency.