Multi-MPPT 72-Pulse VSC Based High-Power Grid Interfaced Solar PV Plant With Distributed DC-Coupled Battery Energy Storage

This article presents a 120 MW capacity solar photovoltaic (PV) plant with a battery energy storage (BES). This plant has utilized high-power 72-pulse voltage source converters (VSCs), developed using six multi-winding transformers and twelve three-level neutral-point-clamped (NPC) converters. 72-pulse operation of the VSC is realized by suitably selecting the transformers phase-shifting and NPCs switching phase-displacement angles. The multi-MPPT approach is applied in the VSC to optimize energy generation from the solar PV array. This solar PV plant has utilized DC-coupled BES, which is distributed along with the solar PV array field in the plant area. The excess PV energy is stored in the BES locally and dispatched the same during nighttime when PV array is not generating using the same solar VSC and DC and AC electrical equipments. Thus, it offers a saving on investment cost. Additionally, the VSC is utilized to provide reactive power to the grid. A developed MATLAB model of the solar PV and BES plant is presented along with the OPAL-RT real-time implementation strategy, and steady-state, harmonics and dynamic responses are obtained.