Adaptive robust integral sliding mode pitch angle control of an electro-hydraulic servo pitch system for wind turbine

A new electro-hydraulic servo pitch system is proposed to enhance pitch angle control performances and hence to smooth generator power fluctuations for wind turbines. The pitch system mainly consists of a variable-speed hydraulic pump, a hydraulic motor and a pitch gear set. The hydraulic pump is employed to directly regulate the direction and rotational speed of the hydraulic motor that achieves the final pitch angle control through the gear set. An adaptive robust integral sliding mode pitch angle controller and a projection type adaptation law are synthesized to accurately track the desired pitch angle trajectory and compensate for model uncertainties and uncertain disturbances. The proposed controller and the adaptation law have their achievable performances in practice. Comparative results verify that the proposed pitch angle controller, together with the adaptation scheme, gives improved performances for the accurate pitch angle tracking and generator power control regardless of various uncertainties and disturbances. (C) 2018 Published by Elsevier Ltd.