Communication-Independent Power Balance Control for Solid State Transformer Interfaced Multiple Power Conversion Systems

A coordinated power balance control strategy independent of communication is proposed in this article, which includes autonomous modes transition control methods for photovoltaic converter, battery energy storage system and their cooperation with solid state transformer. The synthesized multiple power conversion systems contain an internal dc point-of-common coupling (PCC) and an external ac PCC, which form a dc microgrid and an ac microgrid, respectively. In grid-connected mode, the system is able to operate in power regulation pattern corresponding to grid-side response, or secondary dc bus voltage regulation pattern corresponding to local loads response, and switch between them on demand. Grid-connected and islanded/standalone modes can be transferred seamlessly, without the need of control structure reconfiguration through communication links. Moreover, control-related real-time communication is no longer necessary in this scheme, thus improving the reliability and reducing the total costs accordingly. Experimental results are provided to validate the effectiveness of the proposed control scheme.