Performance Analysis of Photovoltaic/Battery Unit Voltage and Frequency Control in Islanded Microgrid Under Several Load Unbalances

Abstract

The concept of autonomous microgrids has strongly increased due to the large penetration of distributed generation into the main grid, mainly photovoltaic systems. Attached to these generation units, Battery Energy Storage Systems (BESS) has been widely used to support voltage and frequency regulation since it provides a fast system response. Therefore, this microgrid configuration has extensively used a grid-forming droop control strategy in order to provide a frequency and voltage controlling interface for islanded operation mode. Although there are several studies in the literature proving that this strategy works properly, performance analyses under several load unbalances have been little addressed. This paper aims to analyze a photovoltaic/battery-based islanded microgrid architecture under the previously mentioned load scenario. The proposed work analysis has been performed through simulations using Matlab/Simulink from the modeling of all microgrid components. It was observed that in a low load power scenario, losses caused by more than 20% of unbalance degree cause BESS to not work properly, discharging instead of charging. With a high load power scenario, an unbalance degree of 45% is enough to make the system unable to control DC-Link voltage and consequently not keep AC voltage level.