Power system security improvement using the unified power flow controller (UPFC)

This paper presents an algorithm to find the operating point of UPFCs for the enhancement of system security level. The proposed algorithm minimizes the security index iteratively. The security index indicates the overload level of transmission lines. The sensitivity indicating the change of the index due to the changes in the UPFC real power output is calculated. In each iteration, according to this sensitivity, the proposed algorithm finds a new UPFC operating point to reduce the index or increase the security margin. Also two other indices related to system security level are examined after the UPFCs operating points determination. The proposed algorithm is verified by IEEE 14 bus network. The results show that the power flow congestion can be relieved and the security margin increased both in overloaded or faulted condition by applying the suggested operating algorithm to UPFCs