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Liniger, Jesper

PROJECT TITLE: Design of Reliable Fluid Power Pitch Systems for Wind Turbines 

PhD period: 2014.12.31 – 2017.12.30.
Section: Esbjerg Energy Section 
Research Programme: Fluid Power in Wind and Wave Energy  and Offshore Energy Systems
Supervisor: Henrik Clemmensen Pedersen
Co-Supervisor: Mohsen Soltani
Contact information

Collaborator: Hydratech Industries Wind Power.
Funding: EUDP.


In past decades, wind turbines have been a favourable choice in terms of generating green energy. Because of the ever-increasing interest in cheap energy, the key objectives of wind turbine manufactures and buyers are to reduce the Total Cost of Ownership (TCO) and Total Cost of Energy (TCE). Among others, high reliability of a wind turbine is important to increase the amount of energy produced during its lifetime. Emerging historical data indicate that pitch systems are a substantial contributor to the down time of wind turbines, thus directly influencing the TCO and TCE. This project aims to significantly increase the reliability of such pitch systems.

The pitch system is utilized for regulating the power production of the wind turbine. By adjusting the longitudinal blade axis angle, the pitch system determines the amount of wind energy converted to rotation. In the event of an error, the pitch system directs the blades away from the wind, which stops rotation. The pitch system therefore serves as the primary safety system of the turbine. Hence, increasing the reliability of the pitch system positively influences the safety of the turbine.

Either electrical or fluid power actuators normally drive pitch systems. Fluid power pitch systems generally show higher reliability and have been favoured on larger offshore wind turbines. Still general issues as external leakage, fluid contamination and electrical faults make the current systems work sub-optimal.

Fail-safe systems are being used in the aviation and automotive industry. However, not much work has been done in transferring the methodology to pitch systems. The project objective is therefore to determine how fail-safe methods are utilized for increasing the reliability of fluid power pitch systems. The objective is meet by creating a framework that enables analysis of fluid power pitch systems in terms of reliability. Based on the framework, weak spots for current systems are identified and a robust system architecture consisting of best-suited fluid power components and fault handling control system is proposed. Performance of the new system is validated on a 1:1 scale laboratory setup.


Publications in journals and conference papers may be found at VBN