Perturbation attenuation in Load Frequency Control

This article addresses the problem of robust stabilisation of uncertain systems with linear nominal part suffering from perturbations. The proposed composite con-troller, consisting of a linear state feedback (LQR) and a nonlinear Integral Sliding Mode Control (iSMC), guarantees that despite the presence of unmatched perturbations the closed loop system enters the sliding mode in finite time. The matched perturbations are rejected while the unmatched ones are attenuated in a quantifiable way. The suggested controller is applied on the Load Frequency Control (LFC) of power systems with two and three fully interconnected control areas. Problem specific tuning rules are offered enabling the stabilizing controller to handle also partial stability objectives. The numerical examples corroborate the applicability of the proposed nonlinear methodology.