Frequency Control of a Wind-diesel-generator Hybrid System with Squirrel Search Algorithm Tuned Robust Cascade Fractional Order Controller Having Disturbance Observer Integrated

This paper proposes an optimal cascaded fractional order controller (CC-FOC) having disturbance observer (DOB) to minimize the frequency deviation of an autonomous wind-diesel-generator (WDG) system in the wake of load variation and random wind power output. The model of WDG consists of a variable-speed wind turbine (VSWT) and a diesel engine generator to match the ever-rising load demand. To regulate the frequency of the WDG system, fractional-order proportional-integral-derivative (FOPID) and tilt-integral-derivative (TID) controllers are simultaneously used as master and slave controllers, respectively, for developing the CC-FOC. An improved squirrel search algorithm (SSA) with quasi-oppositional-based learning (QOSSA) is applied to explore the optimum gains of the proposed non-integer controller. The performance of the developed controller is compared with the outputs of FOPID, TID, and PID controllers. The result demonstrates the mastery and effectiveness of the proposed controller against random load and wind power fluctuations. Finally, Kharitonov's stability theorem is applied to ensure the robustness margin of the studied WDG plant for a wide range of system parameters variation.