H-infinity based non-linear sliding mode controller for frequency regulation in interconnected power systems with constant and time-varying delays

Load frequency control (LFC) scheme communicates from remote terminal units to control centre, followed by control centre action on the corresponding plant units. The conventional dedicated communication channels have constant time delay, while open communication channel, i.e. shared one has time-varying delay. These delays degrade the dynamic performance or even lead to system instability. In an interconnected system, communications delays cannot be ignored and therefore the time delay is introduced in the area control error signal. In this study, a time delay-dependent H ∞-based non-linear sliding mode controller for LFC scheme has been proposed for N area power system. The approach uses Lyapunov–Krasovskii functional based on time delay-dependent stability criteria and linear matrix inequalities optimisation. Simulation studies are presented for two-area LFC scheme against step and random step load disturbance and generation rate constraints. Comparison is also made with recently reported; two-term controller design. The simulation results establish the superiority and applicability of the proposed design for LFC application. The results illustrate that the proposed scheme can effectively enhance the frequency stability via improving the damping of the system.