A Droop-Based Frequency Controller for Parallel Operation of VSCs and SG in Isolated Microgrids

Microgrids are a novel concept for modern power distribution networks that integrate renewable power sources and increase power control capabilities. This system's essential problem is controlling the frequency in island mode. Using the synchronous generator (SG) control approach, the microgrid frequency is more stable due to the inertial features of the SG. In this regard, this paper presents a control algorithm for voltage source converters (VSC)-based distributed generators (DGs), which emulates the principal behavior of synchronous machines and can support inertia to the grid and reduce frequency gradients considering the parallel operation of the SG. The controller is designed based on droop control theory, and a supervisory center controller is implemented to maintain system frequency close to a nominal value of the whole microgrid. The simulation results demonstrate that the system frequency is stabilized even in different and sudden load changes in the island mode where the microgrid is fed by multiple VSC units and a SG. The Simulink model of the system is designed using MATLAB Simulink Software.