Robust Frequency Control for Varying Inertia Power Systems

Increased penetration of fluctuating Renewable Energy Sources (RES) adds a significant uncertainty in the dynamic behavior of the power system. Varying power infeed from RES significantly affects the number of conventional generators to be dispatched at any time instant. As a result, system parameters, such as inertia and damping can no longer be considered constants, but instead they obtain a time-varying profile. In this paper, a robust frequency control scheme is introduced to account for the time-varying system inertia and damping under increased RES penetration. The proposed method is based on an H
_∞
loop-shaping design procedure, and it guarantees good frequency response for varying levels of inertia and damping. After presenting the impact of varying system parameters to the system dynamic behavior, the design method for the proposed controller is presented, and its performance is demonstrated in case studies.