Structured Control of LPV Systems with Application to Wind Turbines

Abstract — This paper deals with structured control of linear parameter varying systems (LPV) with application to wind turbines. Instead of attempting to reduce the problem to linear matrix inequalities (LMI), we propose to design the controllers via an LMI-based iterative algorithm. The proposed algorithm can synthesize structured controllers like decentralized, static output and reduced order output feedback for discrete-time LPV systems. Based on a coordinate decent, it relies on a sufficient matrix inequality condition extended with slack variables to an upper bound on the induced L2-norm of the closed-loop system. Algorithms for the computation of feasible as well as optimal controllers are presented. The general case where no restrictions are imposed on the parameter dependence is treated here due to its suitability for modeling wind turbines. A comprehensive numerical example of a gain-scheduled LPV controller design with prescribed pattern for wind turbines illustrate the utilization of the proposed algorithm. I

Adaptive control algorithm for improving power capture of wind turbines in turbulent winds

Abstract — The standard wind turbine (WT) control law modifies the torque applied to the generator as a quadratic function of the generator speed (Kω 2) while blades are positioned at some optimal pitch angle (β ∗). The value of K and β ∗ should be properly selected such that energy capture is increased. In practice, the complex and time-varying aerodynamics a WT face due to turbulent winds make their determination a hard task. The selected constant parameters may maximize energy for a particular, but not all, wind regime conditions. Adaptivity can modify the controller to increase power capture under variable wind conditions. This paper present new analysis tools and an adaptive control law to increase the energy captured by a wind turbine. Due to its simplicity, it can be easily added to existing industry-standard controllers. The effectiveness of the proposed algorithm is assessed by simulations on a high-fidelity aeroelastic code. Index Terms — Wind Turbines, Adaptive Control, efficiency. I

Structured control of affine linear parameter varying systems

Abstract — This paper presents a new procedure to design structured controllers for discrete-time affine linear parameter-varying systems (A-LPV). The class of control structures in-cludes decentralized of any order, fixed-order output feedback, simultaneous plant-control design, among others. A parameter-varying non-convex condition for an upper bound on the induced L2-norm performance is solved by an iterative linear matrix inequalities (LMI) optimization algorithm. Numerical examples demostrate the effectiveness of the proposed ap-proach. I