Multivariable robust control of a horizontal wind turbine under various operating modes and uncertainties: A comparison on sliding mode and [formula omitted] control

Abstract

Wind turbines are generally controlled for the objectives of the turbine protection and generation of the acceptable power for the utility grid. In this paper, a nonlinear multivariable model of the wind turbine with a DFIG generator is considered. The rotor speed and the d-axis rotor current, as the controlled variables, are controlled via manipulation of the two generator voltages, as the control signals. Two robust control strategies including the sliding mode control and H∞ robust control, designed via μ-synthesis based on DK-iteration algorithm, are presented for switching between various operating modes. Development of an acceptable dynamic model and two innovative control strategies that lead to the good performance and stability against various sources of uncertainty and noise rejection, are some of the advantageous points of the designed controllers. Performance of these control strategies are evaluated and compared. During the wind turbine operation, obtaining a maximum active power and suppressing the reactive power are the control objectives. Results are presented for various profiles of the wind velocity. It is observed that the sliding mode controller has a better performance in the transient time response. Moreover, in comparison with H∞, sliding mode control approach leads to the less tracking error and settling time, but minor acceptable chattering exists.