Robust control design of variable speed wind turbine using quantitative feedback theory

Abstract

A robust control design of a three blade, horizontal axis variable speed wind turbine is developed in this paper. The variable speed wind turbine model consists of higher order nonlinear dynamics where uncertainty has been considered in the plant parameters. Quantitative feedback theory is an effective and efficient, robust control technique through which the desired specifications over a specified range of parametric uncertainty can easily be achieved in the frequency domain. The proposed robust torque and pitch control in variable speed wind turbine using quantitative feedback theory satisfy prescribed gain and phase margin, degree of tracking for the robust performance, fast convergence, noise attenuation, and input and output disturbance rejection. The advantages of the proposed robust control design are the consideration of a wide range of performance specifications and achieving effective control over an increased operating frequency range. The simulation results demonstrate the satisfactory performance of proposed quantitative feedback theory-based controller and prefilter which fulfill the necessary conditions such as robust stability and robust tracking. Further, it has been shown that the performance of the quantitative feedback theory-based controller is better than the performance with a standard wind turbine controller and also from the performance by proportional-integral controller.

Design of dynamic surface controller for robust performance of variable speed wind turbine

“…The main objective of this paper is to present the design of torque and pitch control for regions II and III of VSWT. [23] In the MSR, reference generator torque T g, ref is used as a control variable to track the optimal rotor speed ω r opt , in such a way to attain maximum power output from the wind assuming pitch angle θ ref as constant. The ω r opt is related to the optimal tip speed ratio λ opt = R/v w ω r opt which corresponds to a maximum C p λ opt , θ opt = C p max for the extraction of maximum power output.…”

“…The mechanical modelling of the VSWT system in the form of differential equations is considered as [12,23]…”

“…A robust term u s = − K m sgn S 3 has been introduced in control law (24) tackle the uncertainties and hence controller parameters are changing to cope up the effect of uncertainties, K ∈ ℜ 2 × 2 > 0, m = S 3 ᾱ with 0 < ᾱ < 1. Substituting (24) into (23), S˙3 can be rewritten as…”

“…The detailed analysis of the QFT-based controller design for VSWT model has been presented in [23]. The QFT proves to be a robust control technique which can be applied to the linear/non-linear model of VSWT.…”

“…The controller design parameters for both torque and pitch control regions of VSWT are given in Tables 2-4. It was mentioned that the performance of QFT-based control is robust [23] and presently the performance of proposed DSC-based control has been compared with the performance by QFT control. The tracking performances of both the proposed DSC and QFT controllers for the VSWT have been obtained and shown in Figs.…”