MMC-Based Grid Integration of PV-BESS with Power Grid Support Capabilities

Renewable energy integration in the smart grid - including solar photovoltaic (PV) systems - presents stability and reliability challenges due to their intermittent behavior. Integrating battery energy storage systems (BESS) with PV systems is one of the key solutions to these grid challenges, which improves the grid-tied PV systems' performance. Due to scalable and modular structure, modular multilevel converters (MMC) have been recently considered as a promising power electronic technology for grid integration of PV-BESS. This paper proposes a novel full-bridge submodule MMC (FBMMC)-based PV-BESS, where each full-bridge submodule (FBSM) is interfaced with a PV module through a DC-DC converter to realize independent maximum power point tracking (MPPT) and full control over the MMC DC-link where a large BESS is connected to support grid ancillary services. This BESS is used to cover the mismatch between the PV system power output and the grid demand. The proposed topology and its control systems are tested for a 13-level MMC system under different solar irradiance conditions and grid power demand.