Nonlinear Adaptive Switching Control And Its Application To Wind Power Generation

In practical control processes, the control plants always have parametric uncertainties and some nonlinear characteristics. When parameters change, the controller which is designed by accurate mathematical models can’t achieve a desired control performance. Nonlinear adaptive switching control is an effective method to solve problems of complex system, including nonlinear property, strong disturbance and parametric uncertainties. Wind turbines are nonlinear system with parametric uncertainties, at the same time, wind has some complicated properties, such as low energy density, randomness and instability. Regular controller of industrial field can’t obtain a satisfying performance.Supported by State Key Laboratory of Synthetical Automation for Process Industries, the paper tries to apply the idea of nonlinear adaptive switching control to the two-mass drive train of wind turbines. The main contributions of this thesis are listed as follows:(1) This thesis presents a nonlinear adaptive switching control method for a class of discrete-time non-minimum phase nonlinear systems with parametric uncertainties. The proposed control strategy consists of a linear adaptive controller, a nonlinear adaptive controller and a switching mechanism. By using the switching scheme, we can not only ensure the BIBO property of closed-loop system, but also improve the system performance. The thesis requires the higher order nonlinear part of the systems satisfying a linear growth condition, which relaxes the widely used global boundedness condition on the higher order nonlinear term, the analysis of stability and convergence of the adaptive control method are established. The simulation results illustrate the effectiveness of the proposed method.(2) In this thesis, nonlinear adaptive switching control algorithm is developed and applied on wind turbines. By analyzing the characteristics of control plant, the two-mass drive-train of wind turbines has integrated complexities, such as parametric uncertainties, high nonlinearities and time-varying dynamics with different operation conditions. The author gives an optimal tip-speed-ratio adaptive control method for wind turbines based on the nonlinear adaptive switching control method.(3) By comparing the simulation results of the methods, the proposed method can make the output signals track settings of system and improve performance. The experiment results indicate the effectiveness and applicability of the proposed control methods in engineering.