Application of thyristor-controlled series compensators to enhance oscillatory stability and transmission capability of a longitudinal power system

Power transfer capability between the Northern area and the Central area of the Taiwan power system is severely limited by the fact that the power flows over the two parallel corridors connecting the two areas are rather disproportionate to their thermal limits due to different conductor sizes. Placing series capacitors on the corridor which is lightly loaded seems to be a reasonable means to enhance the overall transfer capability of the parallel corridors without overloading the other corridor which is already close to its thermal limit. A joint research project is conducted by the researchers at National Taiwan University and the engineers at Taiwan Power Company (TPC) in order to examine the feasibility of installing a combination of conventional series capacitors and thyristor-controlled series compensators (TCSCs) at TPC´s 345 kV transmission system. Extensive power flow studies are conducted to investigate how the power flows over the two corridors are affected by different locations and capacities of the series capacitors. In addition to steady-state power transfer levels over the two corridors, the eigenvalues for the inter-area oscillation modes are also computed for the system with various compensation plans. A proper compensation plan is determined based on requirements on both steady-state power transfer level and inter-area mode damping. To improve system dynamic performance, a supplementary TCSC damping controller is designed. It is concluded from the results of this work that good damping characteristic can be achieved by coordinated application of the designed TCSC damping controller and the power system stabilizers