Microgrid for Low Voltage Distribution Systems and a Model for Optimum Power Sharing

Abstract

Grid-connected microgrids have become financially and technically feasible due to the high integration of renewable-based distributed generators and the fast development of battery technology. The formation of microgrids facilitates the integration of multiple sources of energy including renewables such as solar and wind at the distribution level. Since the solar irradiation level in Sri Lanka is sufficient for electricity generation using solar photovoltaics throughout the year, the paper proposes forming microgrids for existing low voltage feeders utilizing solar PV as one of the main micro-sources of energy for the microgrids. Other than solar PV, the proposed microgrid consists of a grid supply, battery energy storage device, and diesel generator. Within this study, an algorithm has been developed to optimally share the energy demand of the low voltage distribution system between utility grid, solar photovoltaics, battery energy storage device, and diesel generator. Based on the proposed algorithm, microgrid simulation software has been developed in the MATLAB-Simulink environment. Formula for the determination of most suitable capacities of micro-sources and battery energy storage device were proposed. The proposed model was tested to transform an existing low voltage distribution system into a microgrid. Optimum power dispatch between the sources of the microgrid during 24 hours of a day has been presented using the developed software. The results show that depending on the time of the day the use of solar PV, battery energy storage device, and diesel generator have more financial benefits than the use of grid energy alone throughout the day.