Robust non-fragile approach to resilient design of PID-based blade pitch control for wind energy conversion system

The design of a blade pitch controller (BPC) for wind energy conversion system (WECS) applications is load-dependent and has to be adjusted for each operating condition. Thus, BPC robustness is important for coping with the endless variations in operating conditions. The boundaries of a robust stability region are determined in regards to the controller parameters plane using their relevant set of polynomial inequalities via Referential Integrity between Routh-Hurwitz criterion and Root-Locus (RI-RH/RL) approach. Constrained and unconstrained stability regions respectively are defined through a novel hybrid control technique based on the combination of both RI-RH/RL and Kharitonov (Kh) theorem. The hybrid RI-Kh method is used for globally analyzing all vertex plants to ensure the proposed controller robustness, non-fragility, and resilience by selecting its parameters at the center of the robust stability region. The optimal BPC-PID parameters estimated using different optimization techniques are always located within the specified stability region. Thus, the capability of the RI-Kh approach in determining the most robust, non-fragile and resilient controller is verified. Through simulation results, the effectiveness of the proposed approach and its applicability to WECS' global stabilization are validated.