Hybrid fractional order PIλDµ-PD control scheme for power system with modelling non-linearities and renewable resources

In an integrated power network, the frequency variations and unscheduled tie-line power interchanges are damped using a load frequency control (LFC) mechanism. However, due to system non-linearities and various parametric uncertainties, the effectiveness of conventional LFC strategies suffers significantly. Different non-linearities, such as governor dead band (GDB), generation rate constraint (GRC), boiler dynamics (BD), and communication delays (CD), together deteriorate controller performance and system stability under dynamic operating conditions. To address these difficulties in LFC, this paper presents a robust hybrid control scheme combining a proportional, fractional-order integral and derivative (FOPID) controller with an integer-order proportional and derivative (PD) controller. The proposed hybrid fractional order controller offers more flexibility in design by increasing the controller's degree of freedom, resulting in fine-tuned control over a wide range of system dynamics. The performance of the control scheme is tested on a two-area solar and wind-integrated power system, considering all the realistic non-linearities. The paper's main contribution is tuning the hybrid FOPID scheme using a novel and straightforward graphical tuning method. The proposed controller has been observed to be superior to conventional PI, PID, and FOPID controllers, particularly under diverse and uncertain operating conditions in terms of various time domain specifications like maximum overshoot and settling time.