Distributed Control of Islanded Series PV-Battery-Hybrid Systems with Low Communication Burden

The series photovoltaic-battery-hybrid (PVBH) system is considered a promising solution to better integrating distributed energy sources. However, the state-of-the-art controls are either highly dependent on the communication, by which real-time control variables should be transmitted among all converters, or only suitable for PVBH systems with unity power factor. Accordingly, a novel distributed control is proposed for islanded PVBH systems in this paper. Firstly, a PQ decoupling control is introduced, enabling the control of individual converters with only local measurements. Then, a droop controller is implemented in the battery converter, allowing the system to participate in regulating the islanded grid (voltage and frequency). A reactive power distribution method is subsequently introduced to equalize power-sharing among the converters. Additionally, two anti-over-modulation loops are developed to address the over-modulation issue of both PV converters and the battery converter. With the proposed method, only a few variables with very slow dynamics should be transmitted, and the communication burden can be significantly reduced, leading to higher reliability to some extent. Experimental results have validated the effectiveness of the proposal.