A method for damping Torsional stresses due to SSR in a series compensated power system

Damping of Torsional stresses due to sub synchronous resonance (SSR) using a new static var system (SVS) control strategy is investigated in this paper. In order to damp out torsional oscillations, a proportional integral (PI) controller in coordination with auxiliary control signal is employed to modulate the reactive power output of SVS in accordance to locally measurable signals such as combined active power & reactive power, combined voltage angle & active power and combined derivative of active power & derivative of reactive power. In order to enhance the damping further an induction machine-damping unit (IMDU), coupled with IP turbine is also incorporated. All the signals being local, the proposed controller is relatively simple for practical use. Eigenvalue analysis and digital simulation using non-linear system model is performed in order to demonstrate the effectiveness of the proposed controller under disturbance conditions.