Design of UPFC controllers and supplementary damping controller for power transmission control and stability enhancement of a longitudinal power system

The application of unified power flow controllers (UPFCs) to redistribute the power flows over two disproportionate parallel corridors and to boost the low-voltage profile on the transmission networks of the Taiwan power system is examined. A detailed dynamic generator model is used for a UPFC controller design to give more accurate controller parameters. A power system supervisor and conditioner (PSSC) is proposed to determine proper reference busbar voltages and series power flows for the UPFC control system. To improve system dynamic performance under disturbance conditions, a systematic approach based on the root locus method and pole assignment is developed to reach proper proportional-integral (PI) controller gains for the UPFC control system. In addition, a supplementary damping controller is designed to improve the damping for low-frequency electromechanical mode oscillations. To demonstrate the effectiveness of the proposed UPFC control system, computer simulations are performed to reach the steady-state and dynamic responses of the Taiwan power system. It is concluded from the simulation results that not only the requirements on steady-state power transfer and voltage profile can be obtained, but also the satisfactory system dynamic responses can be achieved by co-ordinated application of the designed UPFC control system.