Voltage collapse issue in a photovoltaic source operating in an islanded microgrid

Microgrids provide an effective way to integrate distributed energy sources, particularly renewable energy sources, into the power system. Renewable energy sources differ from traditional microsources as their generation is variable depending on weather conditions. To achieve the highest renewable energy utilisation, photovoltaic (PV) panels tend to be operated at their maximum power point which also forms the boundary for stable operation. In this arrangement the DC bus voltage can collapse should the PV panels be overloaded. In an islanded microgrid, a droop controller is adopted to limit reactive power as well as distribute real power demand amongst the microsources. This paper proposes a modification to the droop controller to ensure a PV source remains within its maximum power limit. Simulation results are presented to demonstrate the controller's effectiveness.