A new method to determine the droop of inverter-based DGs

This paper proposes a new method to determine the droop of the inverter-based distribution generations (DGs). Conventionally, inverter-based DGs have droop controller with fixed slope according to their capacity. Some additional control methods have been proposed in order to enforce the maximum or minimum limit of a unit. However, in some severe cases, the frequency deviation during the islanded mode becomes larger with the existing methods. To overcome this problem, the proposed method, namely “variable droop,” determines the droop of DGs according to their operating points. Using the proposed method, the frequency can be maintained within the predetermined limits and the load demand can be properly shared by the DGs. The effectiveness of the method is verified by the PSCAD/EMTDC simulation.