Modular Multilevel VSC for Solar PV Plant with Battery Energy Storage

This paper presents a large-scale grid-connected solar photovoltaic (PV) plant featuring DC-coupled battery energy storage (BES) and distributed maximum power point tracking, achieved through a utilization of 96-pulse voltage source converters (VSCs). The 96-pulse VSC comprises four sets of modular 24-pulse VSCs, all employing identical power circuit designs. These 24-pulse VSCs utilize medium voltage transformers equipped with fundamental switched neutral point clamped (NPC) converters. The transformer's high-voltage (HV) windings are arranged in a zigzag configuration with a phase shift differing from that of low-voltage (LV) windings. LV windings are interconnected in a delta open configuration, where NPCs are connected. Both selective harmonics elimination and multi-pulse transformer configurations are used to achieve the harmonics elimination. The MATLAB-Simulink software is used to obtained 240 MW solar PV-BES plant dynamic and steady-state responses. These responses are further validated in real-time using the OPAL-RT platform.