Distributed power flow controller(DPFC)is flexible and convenient in deploying distributed flexible AC transmission system(D-FACTS)device that can effectively improve the distribution of power flow and enhance system loadability. However

the ability of DPFC in power flow control is extremely dependent on its configuration scheme. A two-stage optimal placement method is proposed to maximize the system loadability and find the optimal location of DPFC based on the mixed integer linear programing. The first stage of optimization model determines the maximum system loadability considering traditional power grid constraints and DPFC's physical and operational constraints; whereas the second stage of optimization model takes the maximum system loadability obtained as an operation constraint to determine the optimal location and capacity placement of DPFC by optimizing the DPFC investment costs. The simulation results in IEEE-RTS79 system and an actual power grid demonstrate that the proposed method is effective and reasonable.