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.