Non-integer disturbance observer-aided resilient frequency controller applied to hybrid power system

Abstract

This work made the earliest effort to investigate the performance of a non-integer disturbance observer (NiDob)-aided non-integer sliding mode controller (NiSMC)/second-order SMC (SOSMC) for frequency regulation of an islanded hybrid power system with matched/mismatched uncertainties. The unavoidable presence of unknown system disturbances, uncertainties, and practical limitations of control inputs are considered while developing the proposed resilient nonlinear controllers. Firstly, a NiDob is designed to estimate unknown bounded aggregated plant uncertainties. Subsequently, an improved NiSMC/SOSMC is developed by conveniently augmenting disturbance estimation. Quasi-oppositional marine predators' algorithm (QOMPA) is applied to obtain the near-optimum gains of the proposed frequency controllers minimizing an integral error-based objective function. The finite-time convergence of NiDob and closed-loop asymptotic stability of the studied power system has been established using the Mittag-Leffler/Lyapunov argument. The usefulness and practicability of the applied frequency have been demonstrated by performing a comparative study with SMC, NiSMC (without NiDob), NiDob-aided NiSMC, and other results reported in the literature. The numerical simulations showcase the efficacy of the applied control methodology regarding minimal chattering, faster disturbance rejection, and improved transient performance. The proficiency of the developed control methodology is validated on an IEEE-39/IEEE-68 bus testbed. Finally, the ability of the suggested resilient control algorithm in the detection and mitigation of deception-type cyber-attacks has been tested and affirmed in cyber-physical environments.