A Comparison between the UPFC and the IPFC in Optimal Power Flow Control and Power Flow Regulation

This paper presents a comparison study between the applications of the unified power flow controller (UPFC) and the interline power flow controller (IPFC) in optimal power flow (OPF) control. The power injection models of the flexible AC transmission systems (FACTS) devices are reviewed and incorporated in the OPF problem without active power generation redispatching, which minimizes the overall generating cost. The FACTS devices are planned for power flow regulation and their additional degrees of freedom act as additional potential in optimizing the power system. The performance of the UPFC and the IPFC is compared from the viewpoint of the total active power losses and their necessary capacities through numerical examples. The feasibility of a gradient-based algorithm, namely sequential quadratic programming (SQP), is tested, and the importance and some techniques of proper selection of the initial optimization conditions are also presented.