Robust Stability Analysis of Time-Delayed LFC Systems Considering Variable-Speed Wind Turbines with Deloading Operation

This work investigates the delay-dependent stability of a load frequency control (LFC) system enhanced by wind turbine (WT) with rotor speed control. Advances in energy conversion technologies for variable-speed WTs enable the provision of inertia support, derived from rotational kinetic energy, and primary frequency reserves to the grid. However, the integration of communication networks for data exchange in generation units' management introduces network-induced delays, which can negatively impact frequency stability. Although the inclusion of WTs in LFC systems enhances dynamic stability, it also increases system complexity. Consequently, it is essential to apply robust controller design techniques to maintain stability. This study utilizes Kharitonov's Theorem to account for parametric uncertainties and communication delays within the LFC system, including WT dynamics, and to define robust stability regions (RSRs) in the parameter space of the Proportional-Integral controller. Results show that incorporating WTs with inertia and deloading control into the LFC system significantly improves RSRs.