Dynamic Stability Enhancement by Static Synchronous Series Compensator based Supplementary Damping Controller

Oscillations of power systems are generally associated with transmission system disturbances such as step changes in load, sudden change of generator output, transmission line switching, and short circuits etc. Depending on the characteristics of the power system, the oscillations may last for 3-20 seconds after a severe fault. During such angular oscillation period, significant cycle variations in voltages, currents, and transmission line flows will take place. It is important to damp these oscillations as quickly as possible because they cause mechanical wear in power plants and many power quality problems. Although power system stabilizers(PSS) provides supplementary feedback stabilizing signals they are liable to cause great variation in voltage profile and may result in system instability under severe disturbances. To overcome this problem Static Synchronous Series Compensator (SSSC) based supplementary damping controllers are introduced. SSSC damping controller can contribute to damping of low frequency oscillations. The design problem of the SSSC based damping controller is formulated as an optimization problem and Simulated annealing algorithm (SA) is employed to search for optimal controller parameters.