Control of SSR oscillations through a quasi-optimum dynamic braking strategy

Dynamically switched resistor banks connected to the generator transformer bus axe. generally, known to improve transient stability of power systems. In this article, an optimum dynamic braking resistor control strategy is proposed to damp the slowly growing subsynchronous resonant (SSR) frequency oscillations. The control strategy employs feedback of generator speed variation, rotor angle, and power variation signals. The control is designed so as to eliminate the system oscillations as quickly as possible. The proposed control is tested on the IEEE second benchmark model for subsynchronous resonance studies. The dynamically switched braking resistors are found to control unstable SSR modes very effectively. The power requirements of the brakes are demonstrated to be very small. The control algorithm is simple, and its realization will require very little hardware.