A New Under-Frequency Load Shedding Scheme for Islanded Distribution Network

High penetration of distributed generation (DG) in distribution level has open an opportunity for islanding operation of distribution networks. Through proper islanding operation, the reliability of the system can be improved by continuously supplying power from DG. However, an effective protection schemes for an islanded network are still an issue to be solved. Specifically to balance DG generation and load demand in order to maintain system frequency. Hence, an effective under-frequency load shedding scheme is required for an islanded distribution network which is not as strong as the grid. This paper presents a new under-frequency load shedding scheme for an islanded distribution network. A combination of adaptive under-frequency load shedding and state estimation is proposed for efficient and precise load shedding scheme. In this proposed method, overload is anticipated by utilizing an adaptive under-frequency load shedding scheme. Meanwhile, State estimation is used to estimate the load value. Finally, the estimated value of overload will be shed according to the estimated value of each bus demand.