Variable Loop Gain Using Excessive Regeneration Detection for a Delayed Wide-Area Control System

Excessive time delay in the implementation of a wide-area damping controller may lead to poor time-domain response or instability of an otherwise stable closed loop system. Careful monitoring of the controller output reveals the relative phase margin as it tends toward a vanishingly small value. Design and analysis of the excessive regeneration detector for system stability migration is presented. Details of degradation are followed by the description of a variable loop gain controller to ensure stability in the presence of significant delay, with nominal controller design developed using loop shaping theory. Linear and nonlinear stability of the system is assessed with the variable loop gain controller in place. Simulations of multiple disturbance environments and time delay conditions validate the developed theory using a detailed nonlinear model of the western North American power system. Finally, a GPS spoofing algorithm is employed to demonstrate the efficacy of the approach to a malicious phasor measurement unit attack.