Sliding mode controller design via H∞ theory for windmill power systems

The method of variable structure control (VSC) using frequency criteria of H^∞ control theory for sliding surface design in windmill power systems is proposed. Using the quasi-linearization transform technique, we develop a type of equation which is suitable for the H^∞ control full information problem. In the design of sliding mode control, the stability of the sliding surface and the reachability to it should be certified. We use Riccati equations arising in linear H^∞ control to find a stable sliding surface. Then the reachability to the sliding surface is realized by designing a nonlinear controller for the windmill power system. The capability of the proposed controller to damp out the oscillations of power and the robustness with respect to the system parameter variations and model errors are evaluated in the simulation study