Virtual Synchronous Machine Control of RES Plants in Isolated Power Systems

Because of the increase in renewable energy sources (RESs) share, new control strategies of isolated power systems have been developed to improve the frequency and voltage stability of inverter-interfaced RESs. A voltage source converter (VSC) with a virtual synchronous machine (VSM) is among the most promising control schemes. This paper demonstrates how VSM control of inverter-interfaced RES can be efficiently used to improve the dynamic stability in small isolated power systems. In the proposed analysis, the RESs of a Mediterranean island are assumed interfaced to the grid by VSCs with a swing controller and a vector-current controller (VCC) with two different options for the reference current (RC) to regulate the voltage at the point of common coupling (PCC) and the real power output. The system is modelled in a PSCAD environment, and the behavior of the control is tested in the case of a phase-to-phase fault. The results of the simulations for different scenarios and values for the control parameters show the effectiveness of the control in small isolated grids. Finally, the level of grid power quality is verified via harmonic analysis of the PCC voltage.