LOAD SHARING REGULATION OF A GRID-CONNECTED SOLAR PHOTOVOLTAIC SYSTEM IN KARBALA CITY

Abstract

Microgrid is an effective solution for increasing the reliability of power distribution system using renewable energy sources. In this research, a solar photovoltaic (PV) power system designed for extraction maximum power, i.e. 100kW (at standard conditions, 1000 W/m2 and 25oC) is simulated for grid utilities. For extraction maximum power, the duty ratio of a DC-DC converter is adjusting based on the specific value of maximum power point (MPP) voltage of the PV array. Thus, the DC voltage of the inverter side is kept constant to meet the grid specifications, e.g. 400V and 50Hz. The PV array is modelled by nonlinear equations which describe the effect of real irradiance levels (for Karbala city) on DC voltage. The PV power system is designed in an actual location in Karbala city for supplying a three-phase load, e.g. about 62 kW. Due to the fluctuations in solar irradiance, a load sharing between the PV power system and the grid is controlled. The load sharing is verified numerically by the Newton-Raphson method for a three-bus ring distribution system. Numerical and simulation results show the capability of the designed PV power system to share the load with grid over the year.