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 flo ws over the two parallel corridors connecting the two areas are rather disp roportionate to their thermal limits due to different conductor sizes. Plac ing series capacitors on the corridor which is lightly loaded seems to be a reasonable means to enhance the overall transfer capability of the paralle l corridors without overloading the other corridor which is already close t o its thermal limit. A joint research project is conducted by the researche rs at National Taiwan University and the engineers at Taiwan Power Company (TPC) in order to examine the feasibility of installing a combination of co nventional series capacitors and thyristor-controlled series compensators ( TCSCs) at TPC's 345 kV transmission system. Extensive power flow studies ar e conducted to investigate how the power flows over the two corridors are a ffected 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 deter mined based on requirements on both steady-state power transfer level and i nter-area mode damping. To improve sq stem dynamic performance, a supplemen tary TCSC damping controller is designed. It is concluded from the results of this work that good damping characteristic can be achieved by coordinate d application of the designed TCSC damping controller and the power system stabilizers.