Cascaded Converter for Large-Scale Solar-BES System with Transformer Isolation

Abstract

In this work a MW size voltage source converter (VSC) is switched at the fundamental frequency. This converter can attain eleven-level from cascaded H-bridge cells. The transformer isolation (11L-TCHB) is implemented with a battery energy storage (BES) that has a rating of 24MW/16SMWh. The BES is used in an 40MW solar PV plant for the support of active power under solar fluctuations. The TCHB-VSC and NAS batteries complement one another as TCHB enables the NAS container to be connected directly with its H-bridges for independent state-of-charge (SOC) control of the battery. The NAS-battery provides DC input source to TCHB VSC for staircase voltage waveform generation and enables NAS-BES to have high voltage integration with the grid. In addition, the fundamental switching gave high conversion efficiency and reduced switching stress over high-frequency schemes. This integrated system is designed and modeled to validate the performance under solar dynamics. Simulation results are discussed in detail to present a solar photovoltaic (SPV) system with improved power quality.