Single-Stage Isolated PV-Battery-Hybrid (PVBH) Cascaded Grid-Connected System Based on Multiplexing Converter

The photovoltaic-battery-hybrid (PVBH) cascaded converter has become an attractive energy integration scheme, which has the advantages of modularity, module-level maximum power point tracking (MPPT) operation, output power without fluctuation components and so on. However, during the heavy load demand period at night, the PVBH cascaded converter is idle due to no photovoltaic (PV) power input, resulting in low utilization of the converter. This paper proposes an PVBH cascaded grid-connected system by multiplexing converter in its idle state. The proposed system can flexibly be switched to an energy storage (ES) power station that provides active frequency and voltage support for the power grid without additional ES converters, thus improving the asset utilization of the distribution network. First, the structure of the proposed system and the working principles of its cascaded submodules are introduced. Then, the operation mode selection conditions between "PVBH grid-connected mode"and "ES power station mode"of the system are given. Additionally, the corresponding control strategies are designed for the two operation modes of the system. Finally, the effectiveness of the proposed control strategies is verified through a 10-kV/3-MW full power simulation platform, and a 150-V/1-kW scaled-down experimental prototype is built to further demonstrate the correctness of the proposed system.