Damping subsynchronous resonance in power systems

An idea is presented for damping SSR in power systems using a double-order SVS auxiliary controller in combination with continuous controlled series compensation (CCSC) and an induction machine damping unit (IMDU) coupled with the T-G shaft. A linearised dynamic model of continuous controlled series compensation has been derived and incorporated. The eigenvalue analysis using the linearised model for continuous operation of CSC in combination with an induction machine damping unit (IMDU) and a double-order SVS auxiliary controller (DOAC) has been applied. It is seen that all the unstable torsional modes of various frequencies are stabilised effectively. A time-domain modulation study has also been performed using the nonlinear model to demonstrate the effectiveness of the proposed scheme under large disturbance conditions. The scheme enhances the system performance considerably and torsional oscillations are damped out at all levels of series compensation and effective control of power flow is obtained.