Power system frequency control of an islanded distribution network connected to distributed generation based on under-frequency load shedding

In this article; an islanded distribution network, which is connected with Distributed Generation (DG), is investigated. A distribution network that be able of operating in both grid connected or islanded condition, will improve reliability and power quality of the customers. In this case, the DG will be maximized to supply and feed the distribution network loads, even in islanded mode. Therefore, for the operation of the islanded distribution network, the frequency and voltage of the network should be kept within their optimal range. During the islanding mode voltage and frequency are very sensitive in distribution network connected with DG and the system frequency is determined by the power balance in the islanded system. This research adopt an Under Frequency Load Shedding (UFLS) scheme in response based and event based methods to improve the system stability and security by enhancing the frequency and voltage response of the system on occurrence of contingency in distribution network. Proposed method is performed based on frequency and Rate of Change of Frequency (RoCoF) for islanded distribution network. Developed UFLS scheme provide a fast decision to prevent the frequency decline in the system. Hence, after calculating the amount of load needed to be shed; this method will shed the required load in one-step to find a better response. The proposed method functionality has been investigated and an acceptable stability for the voltage and frequency of the network has been obtained.