A modular multilevel converter based battery-ultracapacitor hybrid energy storage system for photovoltaic applications

Abstract

To smooth the output power of a Photovoltaic (PV) system, the integration of the Hybrid Energy Storage System (HESS) has been considered as an effective solution. In this paper, a Modular Multilevel Converter (MMC) is proposed for the HESS that combines battery and UltraCapacitor (UC), and a two-layer framework is proposed to control the proposed HESS system. Compared to traditional HESSs and other MMCs for HESS applications, the proposed MMC based HESS increases the overall system efficiency, reduces the cost of dc side passive components, and is favorable for grid energy storage systems. Simulation results are provided to verify the theoretical analysis.