Stability Delay Margin Computation of Load Frequency Control System with Demand Response

This paper investigates the impact of dynamic demand response (DR) loop including a communication time delay on the stability delay margin of a single-area load frequency control (LFC) system considering both gain and phase margins (GPMs). A gain-phase margin tester (GPMT) is added to the DR loop of the LFC system as to include GPMs in the calculation of stability delay margins. A direct method in the frequency-domain is employed to compute stability delay margins in terms of system and controller parameters. For a large range of proportional - integral (PI) controller parameters, time delays for which LFC system with DR loop is both stable and has required stability margin quantified by GPMs are determined. Simulation results that delay margins should be computed by taking into account of both gain and phase margins to achieve faster damping of oscillations, less overshoot and settling time.