Abstract. This paper presents the state-of-the-art technologies and development trends of wind turbine drivetrains – the system that converts kinetic energy of the wind to electrical energy – in different stages of their life cycle: design, manufacturing, installation, operation, lifetime extension, decommissioning and recycling. Offshore development and digitalization are also a focal point in this study. Drivetrain in this context includes the whole power conversion system: main bearing, shafts, gearbox, generator and power converter. The main aim of this article is to review the drivetrain technology development as well as to identify future challenges and research gaps. The main challenges in drivetrain research identified in this paper include drivetrain dynamic responses in large or floating turbines, aerodynamic and farm control effects, use of rare-earth material in generators, improving reliability through prognostics, and use of advances in digitalization. These challenges illustrate the multidisciplinary aspect of wind turbine drivetrains, which emphasizes the need for more interdisciplinary research and collaboration.

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This paper presents a multi-degree of freedom torsional model of drivetrain system as the digital twin model for monitoring the remaining useful lifetime of the drivetrain components. An algorithm is proposed for the model identification, which receives the torsional response and estimated values of rotor and generator torques, and calculates the drivetrain dynamic properties, e.g. eigenvalues, and torsional model parameters. The applications of this model in prediction of gearbox remaining useful lifetime is discussed. The proposed method is computationally fast, and can be implemented by integrating with the current turbine control and monitoring system without a need for a new system and sensors installation. A test case, using 5 MW reference drivetrain, has been demonstrated.

This paper presents an in depth evaluation and comparison of three different drivetrain choices based on permanent-magnet synchronous generator (PMSG) technology for 10-MW offshore wind turbines. The life cycle approach is suggested to evaluate the performance of the different under consideration drivetrain topologies. Furthermore, the design of the drivetrain is studied through optimized designs for the generator and gearbox. The proposed drivetrain analytical optimization approach supported by numerical simulations shows that application of gearbox in 10-MW offshore wind turbines can help to reduce weight, raw material cost, and size and simultaneously improve the efficiency. The possibility of resonance with the first torsional natural frequency of drivetrain for the different designed drivetrain systems, the influence of gear ratio, and the feasibility of the application for a spar floating platform are also discussed.This study gives evidence on how gearbox can mitigate the torque oscillation consequences on the other components and how the latter can influence the reliability of drivetrain. KEYWORDSdrivetrain optimization, floating offshore wind turbine, life cycle assessment, permanent-magnet synchronous generator INTRODUCTIONThe capacity of offshore wind turbines and the distance from shores is rising rapidly, so that multigigawatt offshore wind farms based on multimegawatt floating turbines show potentials to be one of the dominant sources of power production in the future. The latter is due to availability of better wind resources, less turbulence, steadier winds, and less wind shear; easier transportation of larger turbines on the sea; technological developments in power electronic converters and direct current (DC) power transmission technologies; the establishments of required market infrastructures; and technological achievements in installation of turbines in deep waters, which lead to a considerable drop in the levelized cost of energy (LCOE) of offshore wind turbines. In spite of significant improvements, there are still no unanimous decision about the drivetrain system technology in offshore wind turbines. 1,2 Offshore wind reaches to 10-MW turbines or even higher, but there are still different interests between manufacturers in the selection of drivetrain technology. One reason is that the drivetrain in wind originally comes from available experiences in other industries, which has been modified over time. The latter has then been upscaled for higher powers with some modifications to reduce the production costs and improve the dynamic response. Because the wind turbines are developed for a wide range of power in various onshore/offshore, fixed/floating, two-/three-bladed rotors, upwind/downwind, high/medium/low wind, fix/variable speed, stall/active yaw, and stall/active pitch applications, a customized design of the drivetrain for the cost reduction and performance improvement is inevitable. Therefore, there is a need for a special drivetrain design for each power class for different applicati...

Abstract. This paper presents the state-of-the-art technologies and development trends of wind turbine drivetrains – the energy conversion systems transferring the kinetic energy of the wind to electrical energy – in different stages of their life cycle: design, manufacturing, installation, operation, lifetime extension, decommissioning, and recycling. Offshore development and digitalization are also a focal point in this study. The main aim of this article is to review the drivetrain technology development as well as to identify future challenges and research gaps. Drivetrain in this context includes the whole power conversion system: main bearing, shafts, gearbox, generator, and power converter. The paper discusses current design technologies for each component along with advantages and disadvantages. The discussion of the operation phase highlights the condition monitoring methods currently employed by the industry as well as emerging areas. This article also illustrates the multidisciplinary aspect of wind turbine drivetrains, which emphasizes the need for more interdisciplinary research and collaboration.