An Effective Power Management Scheme for Grid connected and Islanded PV/DG Hybrid Microgrid

PV based Microgrid presents more difficulties to achieve desire control objective in grid connected mode as well as in islanding mode. In grid connected mode PV source connected inverter is operated as controlled current source using P-Q control method. In islanding mode main control objective is to control voltage and frequency within a nominal range for stable operation. V-f Control based droop control method is used in islanding mode by operating inverter as controlled voltage source. Also in PV based MG it is necessary to maintain DC bus voltage stability that occurs due to load change or grid disconnection. In islanding mode it is essential to maintain DC bus voltage stability to avoid overloading of PV source by accurate power balance. In this paper modified power management scheme is proposed so that PV source can work as controlled voltage source in grid connected mode as well as in islanding mode which is capable of maintaining dc bus voltage stability during load change or during grid disconnection. Using proposed method desire power transfer in grid connected mode and stable islanding operation as well as smooth transition between both modes are achieved. Simulations results are presented to validate the effectiveness of the control approach.