Design of a single stage transformerless VSI in a smart microgrid for PV-STATCOM/ESS operations

In recent years, the microgrid has emerged as a promising concept and gained significant attention along with different renewable energy sources in the distribution network. Proper power coordination and strategic controller selection can extend the horizon of applications of the traditional microgrid system. This paper demonstrates the multi-operations from a single stage transformerless voltage source inverter (VSI) in the ac-dc microgrid. The designed VSI coordinates active power from the Photovoltaic (PV) system, acts as a rectifier for the dc loads, performs VAR compensation as a static synchronous compensator (STATCOM) and reduces voltage and power oscillation as STATCOM/ESS (energy storage system) operation under divergent operating conditions, such as, sudden radiation changing, random load changing, different faults effects etc. The developed microgrid model represents the commercial smart microgrid built at Griffith University, Nathan campus, which consists of PV, battery energy storage system (BESS) and single stage transformer-less STATCOM. Performance analysis of the smart microgrid model is carried out in power system computer aided design (PSCAD) /electromagnetic transient dc (EMTDC) software environment. The results prove that the designed VSI can coordinate individual power profiles distinctively maintaining system stability and the excess PV generated power contributes similarly as an ESS for STATCOM/ESS operations in the microgrid.