Stability Criteria for Power Systems with Damping Control and Asymmetric Feedback Delays

Power system inter-area oscillations can be damped using distributed control of multiple power injections within the interconnection. This type of control traditionally requires system-wide measurements which are transmitted from dispersed, sometimes remote, locations and are subject to delays. This paper evaluates the effect that delayed feedback signals have on the stability of a two-area power system and presents delay-dependent criteria for stability using two different implementations of a damping controller. The controllers are based on a uniform proportional control action and use two feedback signals one from each area of the two-area power system. Each of these signals is subject to an independent delay. Using a Lyapunov-based approach, sufficient conditions for stability that depend on each time delay are found for a range of proportional control gains. Numerical results show that the regions of time delays for which the system is stable are reduced as the proportional gain increases. Time domain simulations validate these stability regions and show the varying responses for the two control implementations and different values of the proportional gain.