جستجوی مقالات مرتبط با کلیدواژه « rate of change of frequency » در نشریات گروه « برق »

In Recent advances in renewable energy technologies as well as the restructuring of the electricity market have increased the use of renewable energy resources. The use of these energy sources has many benefits such as increasing reliability, improving power quality, and peak shaving. However, one of the main disadvantages of these energy sources is the islanding detection. The island mode occurs when the main grid is interrupted for any reason, and the part of the grid that contains distributed generation supplies local loads independently from the main grid. Unintentional islanding causes problems such as protective interference and damage to consumer equipment. As a result, the fast detection and disruption of the distributed generation is essential to prevent equipment damaging. This paper presents a new hybrid islanding detection method for distributed generation resources to activate the real power shift method in case the rate of frequency change, in the first stage, exceeds the threshold. Then, if by changing the real part of the DG output current, the voltage amplitude changed, the islanding event would be detected.  The proposed method is implemented and simulated in the Matlab/Simulink environment.  It was also investigated under various conditions such as load switching, motor starting, and multi-DG mode. The simulation results showed the performance of the proposed method in islanding detection in these conditions.

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.

This paper presents an optimal method of frequency load shedding (UFLS) based on the rate of change of frequency of load (ROCOFL) in islanded distribution networks (DN). The proposed method minimizes the average amount of penalties paid by the independent operator of the network by utilizing the relevant cost function. The function of islanded distribution network occurs after an error in the sub-transmission network and separation from the upstream network, in an emergency condition, is one of the most important facts that has been recently addressed. The use of installed intelligent equipment to measure and send information, related to power, frequency, frequency changes, voltage range, and condition of generator switches makes it possible to provide an appropriate protection for the islanded networks. The under frequency load shedding is used to improve the network frequency due to the imbalance in the network. In this paper, it is tried to use the two proposed control modules to eliminate the optimal load with the consideration of the minimum penalty. The method presented in this paper is evaluated in the sample network of 14-bus Danish distribution network.