Abstract: With the Yi-Feng transmission system containing the thyristor controlled reactance series compensation by adjustable coupling(TCSCAC)as the research object,following the process of TCSC for transient stability control simulation analysis and tests are performed on TCSCAC for transient stability control and power oscillation damping.During the power oscillation damping process taking the state variable as control parameter of XT,damping action of XT to power oscillation is proved,and rotor motion equation containing XT is built again.Simulation of transient stability control is conducted by regulating thyristor controlled reactance by adjustable coupling.Adopting control method of simulation system,the tests of transient stability control and power oscillation damping are carried out on the dynamic analog device containing TCSCAC.The results of simulation analysis and test show that TCSCAC is proper and effective for transient stability control and power oscillation damping,and the damping effect is remarkable.