Nonlinear ${cal H}_{\infty }$ Constrained Feedback Control for Grid-Interactive WECS Under High Stochasticity

Wind turbine technology has evolved into a unique technical identity with potential to contribute significantly to the global energy mix powered by renewables. Wind energy, being a fluctuating resource, requires tight control management that ad dresses stability issues for it to be integrable with the grid system. Difficulty in controller construction for wind energy conversion systems (WECSs) is reinforced by sensitivity to numerical complexity, fast parameter variations due to wind stochasticity, tight performance requirements, as well as the presence of flexible modes that limit the control bandwidth. Proposed herein is a pitch control scheme and a model-based H_∞ synthesis controller that yields a multivariable control law governing operation of the power electronic converter for a megawatt-class WECS over the entire nominal operating trajectory. The H_∞ control objectives are cast as optimization programs with a unique cost function subject to linear matrix inequality constraints. Simulational analysis confirms the efficacy of the adopted technique: issues regarding uncertain ties with respect to system modeling and possible adverse control due to interactions with highly turbulent winds are handled with precision, while significantly improving the quality of voltage and output power.