Coordinated Control of Distributed Energy Resources and Conventional Power Plants for Frequency Control of Power Systems

Recently, distributed energy resources (DERs) are becoming more attractive to supply local loads under concept of microgrids. These new parts of the power system have basically different dynamics compared with conventional power plants (CPPs). Some of them do not have any rotating inertia and most of them are connected to the grid by power electronic interfaces. Stability and control of microgrids and the entire power system containing DERs and CPPs is one of the most important challenges of the recent power systems. Interactions between microgrids in grid-connected mode and CPPs should be coordinated to ensure and improve the stability of power system. In this paper, the effect of the increased penetration of DERs on the load frequency problem of power system is studied. Basically, synchronous generators of CPPs determine the dynamic behavior of power system for frequency control and are responsible to compensate load changes of the system. With the high penetration of DERs, these new parts can contribute in the frequency control. It is shown that with appropriate control of DERs in microgrids, the frequency deviation of the power system will decrease and the stability margin can be increased.