Abstract—The power-transfer capability of long transmission lines is usually limited by large signal stability. Economic factors, such as the high cost of long lines and revenue from the delivery of additional power, give strong incentives to explore all economically and technically feasible means of raising the stability limit. The Flexible AC Transmission Systems (FACTS) devices could provide fast control of active and reactive power through a transmission line. We have tried to introduce a new model for transient stability prediction of a power system with a Unified Power Flow Controller (UPFC) to add a contribution to the subject. For this reason we applied so called, Committee Neural Networks (CNNs) methods as tools for Transient Stability Assessment (TSA) of power system. We use the “Mixture of Experts” (ME) in which, the problem space is divided into several subspaces for the experts, and then the outputs of experts are combined by a gating network to form the final output. In this paper, ME is used to assess the transient stability of power system with a UPFC after faults occur on transmission lines. Simulations were carried out on the IEEE 9-bus with and without a UPFC tests systems considering three phase faults on the systems. The data collected from the time domain simulations are then used as inputs to the ME in which is used as a classifier to determine whether the power systems are stable or unstable.

Index Terms—Transient stability assessment , Mixture of the Experts, Time domain simulation method , flexible AC transmission systems and Unified Power Flow Controller.

The Authors are with the Shahid Rajaee Teacher Training University,Department of Electrical and Computer Engineering, Lavizan, 16788,Tehran, Iran. Tel/Fax: +98 (21) 22970006; Emails:rebrahimpour@srttu.edu,e63kazemi@gmail.com,{motiebirjandiSmoussavi}@srttu.edu

Cite: Reza Ebrahimpour, Easa Kazemi Abharian, Ali Akbar Motie Birjandi and Seyed Zeinolabedin Moussavi, "Transient Stability Assessment of a Power System with a UPFC by Mixture of Experts," International Journal of
Computer and Electrical Engineering vol. 2, no. 4, pp. 643-648, 2010.