Design of Double Integral Sliding Mode Control for Variable Speed Wind Turbine at Partial Load Region

Abstract

This work discusses the design of a nonlinear controller for a single mass model of a variable speed wind turbine without measurement of wind speed. Dynamic load on the drive train shaft plays a vital role in turbine lifespan. So the design of the nonlinear controller should pay more care in mitigation of transient load on the drive train shaft. The objective of the controller is to extract the optimal power with limited dynamic loads on the shaft. The above objectives are satisfied by tracking the reference rotor speed which is done by a nonlinear controller. Effective wind speed is obtained by Modified Newton Raphson (MNR), which is used for deriving the reference rotor speed. In this paper, a nonlinear controller, i.e. double integral sliding mode controller (DISMC) is proposed for the single mass model of a wind turbine at partial load region (below rated wind speed). Lyapunov candidate function is used for analyzing the stability of the proposed controller. The performance of the proposed controller is compared with conventional integral sliding mode controller (ISMC) in terms of performance parameters. The robustness of the controllers are analyzed in the presence of different input disturbances and different wind speed profiles. From results, it is found that DISMC can able to accommodate various input disturbance level up to 5kNm.