Simulation of unified static VAR compensator and power system stabilizer for arresting subsynchronous resonance

In the literature, co-ordination of Static Var Compensator (SVC) and Power System Stabilizer (PSS) using generator speed deviation or modal speeds as stabilizing signals is shown to damp the system oscillations. Though such s chemes are able to damp the SSR modes for small disturbances, they are unab le to damp transient SSR due to large disturbances. Here in this report imp rovement in the control aspect of the SVC at the midpoint of the transmissi on line is suggested. This scheme attempts different auxiliary signals that include Line Current, Computed Internal Frequency, Bus Angle deviations. A system of configuration similar to IEEE First Bench Mark model is consider ed, eigen value analysis has been carried out, and results indicate that Bu s Angle deviation signal as auxiliary control signal for SVC was able to da mp most of the modes leaving some of them still oscillatory. The main featu re of the proposed work is to use combination of deviation in speed and ele ctrical power output of the generator as input signals to PSS which operate s simultaneously along with SVC. Such simultaneous PSS and SVC scheme is fo und to improve the damping under large disturbances i.e. the growth of syst em oscillations is arrested. The simulations are carried out on PSCAD. The efficacy of controllers to damp SSR under steady state and faulted conditio ns where one of the torsional modes gets excited is presented and discussed .