An intelligently optimized SEDC for multimodal SSR mitigation

This paper presents an intelligently optimized multimodal supplementary excitation damping control (OMSEDC) to depress subsynchronous resonance (SSR) that may occur in series-compensated power systems. In the proposed OMSEDC, each torsional mode is controlled through an independent feedback path in order to achieve better and multimodal damping. To make OMSEDC feasible and robust, the control parameters are optimized on a number of linearized system models over a set of carefully selected operating conditions. During system modeling, the time-delay of the firing control in the thyristor-based excitation system is taken into consideration for the first time, making OMSEDC practicable in real systems. The task of simultaneously tuning for stable control parameters considering multiple torsional modes and under different system conditions is formulated into a constrained nonlinear optimization problem, which is generally difficult for traditional methods. In this paper, the genetic and simulated annealing algorithm (GASA) is adapted and implemented to obtain the optimal parameters with high efficiency. A practical series-compensated system is employed to evaluate the effectiveness of OMSEDC. Both eigenvalue analysis and nonlinear electromagnetic simulations have demonstrated a satisfactory damping performance of the controller on multiple torsional modes and in different system conditions.