A New Control Strategy to Mitigate the Impact of Inverter-Based DGs on Protection System

Despite their undoubted advantages, Distributed Generation (DG) systems can negatively impact some aspects of the distribution system operation. In this paper, impacts of inverter-based DGs on fuse-recloser coordination in the fuse-saving protection scheme are thoroughly studied. Various fault conditions with different fault resistances and the effects of different DG locations are investigated. Also, the effects of DG reactive power injection, known as a DG potential ancillary service, on the protection scheme are studied. Furthermore, in order to mitigate the impact of DG on the protection coordination, a simple and effective control strategy is proposed. This strategy limits the DG output current according to the DG terminal voltage. Extensive simulations at different fault conditions and different DG penetration levels showed that the proposed control method is able to eliminate DG's contribution during the fault, and consequently eliminate its impact on the fuse-recloser coordination. In comparison to other methods, this strategy is inexpensive, easy to implement, does not limit DG capacity during normal condition, and does not require any change in the original protection system. The simulation results also demonstrated that the proposed method is robust against non-fault transient disturbances such as load switching, starting of induction motors, etc.