Analysis and Verification of the Stability for PV Series-Connected Power Optimizer System

Photovoltaic (PV) energy generation gets more and more attention in the last decades. Among many structures of PV system, series-connected power optimizer (SCPO) system is regarded as a promising one. However, the cross-coupling effect introduced by the series-connected structure cannot be avoided, which would weaken the stability of the system, resulting in failure of operation of the system. Therefore, it is significant to analysis the stability of the series-connected system and suppress the effect by improving the closed-loop control strategy and compensation design. In this paper, the small-signal ac model consisting of three optimizers is derived and the criterions of stability and compensation design are proposed. Computer simulation and hardware experiment are used to verify the validity of the proposed theories.