Abstract
Abstract. The business case for compact hydraulic wind turbine drivetrains is becoming ever stronger, as offshore wind turbines are getting larger in terms of size and power output. Hydraulic transmissions are generally employed in high-load systems and form an opportunity for application in multi-megawatt turbines. The Delft Offshore Turbine (DOT) is a hydraulic wind turbine concept replacing conventional drivetrain components with a single seawater pump. Pressurized seawater is directed to a combined Pelton turbine connected to an electrical generator on a central multi-megawatt electricity generation platform. This paper presents the control design, implementation, and evaluation for an intermediate version of the ideal DOT concept: an in-field 500 kW hydraulic wind turbine. It is shown that the overall drivetrain efficiency and controllability are increased by operating the rotor at maximum rotor torque in the below-rated region using a passive torque control strategy. An active valve control scheme is employed and evaluated in near-rated conditions.
Highlights
The drivetrain of horizontal-axis wind turbines (HAWTs) generally consists of a rotor–gearbox–generator configuration in the nacelle, which enables each wind turbine to produce and deliver electrical energy independent of other wind turbines
The rotor power and torque extraction capabilities from the wind are characterized in respective power and torque coefficient curves. These curves of the actual DOT500 rotor are generated by mapping the actual blade airfoils and applying blade element momentum (BEM) theory (Burton et al, 2011); they are given in Fig. 6 at the blade fine-pitch angle
Due to the predicted consistent mechanical efficiency of the hydraulic drivetrain, the nozzle area can be fixed and no active torque control is needed in the below-rated region
Summary
The drivetrain of horizontal-axis wind turbines (HAWTs) generally consists of a rotor–gearbox–generator configuration in the nacelle, which enables each wind turbine to produce and deliver electrical energy independent of other wind turbines. As offshore wind turbines are getting ever larger, this results in a lower rotation speed and higher torque at the rotor axis This inevitably leads to design challenges when scaling up conventional turbine drivetrains for the high-load subsystems (Kotzalas and Doll, 2010). Integration of hydraulic transmission systems in offshore wind turbines seems to be an interesting opportunity, as they are generally employed in high-load applications and have the advantage of a high power-to-weight ratio (Merritt, 1967). It is concluded in Silva et al (2014) that hydrostatic transmissions could lower drivetrain costs, improve system reliability, and reduce the nacelle mass.
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call