Effective control strategy for photovoltaic cascaded H-bridge inverters developed on FPGA platform

In this work a new control strategy for grid-tied photovoltaic cascaded H-bridge multilevel inverters is presented. The topology analyzed in the paper is made by series connected power cells, each supplied by an individual PV source, thus providing a distributed conversion scheme. The algorithm ensures stable operation even in power unbalance condition among cells thanks to a sorting algorithm which properly selects the switching state of each H-bridge. The control is implemented on FPGA in order to obtain dedicated digital circuits in parallel operation, which is mandatory when the cells´ number increases. The effectiveness of the proposed approach is evidenced by means of experimental tests performed on a single phase 7-level laboratory prototype of H-bridge inverter. The results show good performances in terms of maximum power point tracking efficiency, power factor, and total harmonic distortion.