Enhancement of power system security level through the power flow control of UPFC

This paper presents a new UPFC operation algorithm to find the operating point of UPFCs for the system security level enhancement. The proposed algorithm iteratively minimizes the security index which indicates the overload level of transmission lines. The sensitivity representing the change of the index for a given set of changes in the UPFC real power outputs is derived. In each iteration, with this sensitivity, the proposed algorithm finds a new UPFC opening point that reduces the index or increases the security margin. The algorithm is verified by the IEEE 39 bus system with multiple UPFCs. The study results show that the power flow congestion can be relieved in a normally operating system and the security margin can be guaranteed even in an over loaded or faulted condition by applying the proposed operation algorithm to UPFCs.