A New Decentralized Control Scheme for Improving Frequency Stability in Islanded Micro-grids

Usually Micro grids (MGs) are portion of low voltage distribution feeder including two type sources: slow response for frequency control such as Micro turbine (MT), diesel generator, Fuel cell (FC) and fast dynamic response source such as Battery storage systems (BSs) that can play an important role in restoring balance between supply and demand. In this paper, a new decentralized method for enhancement power sharing between distributed generation resources (DGs) is presented for transient stats in the islanded MGs. This method by changing the conventional droop characteristic of DGs in load variation times improves the MG stability with no communication link. The Overload (OL) ability of the BS is employed for fast handling of the frequency control at transient times of loads variation. To achieve this purpose, by considering the batteries OL characteristic and slow dynamic of some sources, a new power control scheme is developed for improving power sharing. Using the introduced mechanism, load variations in the MG is automatically detected and the proposed controller acts during transient times until the output power of the prime movers in the slow DGs reaches to the final value. Based on this scheme, the MG ability can be increased to deal with all types of load-changing scenarios. In order to evaluate the proposed pattern, a sample MG has been simulated under the Matlab Simulink environment. The simulation results are well illustrated the improvement of the power sharing and frequency stability in the MG.