Passive structural control of offshore wind turbines

Abstract

The application of control techniques to offshore wind turbines has the potential to signifi cantly improve the structural response of these systems. A new simulation tool is developed that can be utilized to model passive, semi-active and active structural control systems in wind turbines. Two independent, single degree of freedom (DOF) tuned massdamper (TMD) devices are incorporated into a modifi ed version of the aero-elastic code FAST (Fatigue, Aerodynamics, Structures and Turbulence). The TMDs are located in the nacelle of the turbine model, with one TMD translating in the fore-aft direction, and the other in the side-side direction. The equations of motion of the TMDs are incorporated into the source code of FAST, yielding a more realistic system for modeling structural control in wind turbines than has previously been modeled. The stiffness, damping and commanded force of each TMD are controllable through the FAST-Simulink interface, and so idealizations of semi-active and active control approaches can be implemented. A parametric study is performed to determine the optimal parameters of a passive single DOF, fore-aft, TMD system in both a barge-type and monopile support structure. The wind turbine models equipped with TMDs are then simulated and the performance of these new systems is evaluated. The results indicate that passive control approaches can be used to improve the structural response of offshore wind turbines. The results also demonstrate the potential for active control approaches. CopyrightSimulations of the systems are performed, and the impact of passive structural control on the performance and loads of offshore wind turbines is highlighted. The results demonstrate the promise that structural control holds for offshore wind turbine structures, as well as the need for more advanced control approaches. Previous work Control of structuresThe control of civil engineering structures has been an active research area for over two decades. [15][16][17][18][19][20] The goal of this body of work has been to protect structures from dynamic loading due to earthquakes, wind, waves and other sources. 21 In the context of wind turbines and in this paper, 'structural control' refers to any device or material that is utilized in a wind turbine structure either to enhance damping or to generate forces to control the structural response. Thus, structural control is contrasted with approaches that utilize the existing control system to improve the structural response; instead, when structural control is implemented, it indicates that an additional degree of freedom (DOF) has been added explicitly to infl uence the structural behavior.There are three major categories of control methods for structures: passive, semi-active and active. 16 Passive structural control techniques are the most simple, as the systems have constant parameters and no energy input to the system. A simple example of a passive system is a mass-spring-damper that is tuned to absorb energy at one of the natural frequencies of the entire struc...

Passive Control of a Pentapod Offshore Wind Turbine Under Earthquakes by Using Tuned Mass Damper

“…The TMD control method applied to OWT and embedded in FAST was presented in [13]. For a multi DOFs system, the equation of motion can be expressed in terms of Kane's theory.…”

“…Recently some scholars applied the TMD and MTMD in the research of vibration control of OWTs, e.g. Dinh [11], Stewart [12] and Lackner [13] investigated the behaviour of OWTs under operational loads in consideration of TMD, and summarized the influence of TMD mass, amount and locations. Colwell [14] and Chen [15] validate the effects of TLCD on the OWT response by using numerical and experimental methods, respectively.…”

Structural Control for an Offshore Wind Turbine with a Tuned Mass Damper in Floating Platform

“…Jonkman et al [3] investigated the use of the aero-hydro-servo-elastic code FAST developed by National Renewable Energy Laboratory (NREL) to simulate the structural responses for barge-type offshore floating wind turbines in different working conditions. Through integrating a passive control code into FAST, Lackner et al [4] proposed an approach using a TMD configuration in the nacelle of the barge-type offshore floating turbines to achieve the structural vibration mitigation, and the control effectiveness of TMD for Spar and TLP-type were also studied. He et al [5,6] proposed the use of TMDs in nacelle to reduce the structure vibration for the barge-type floating turbines, and the results showed that the tower fore-aft displacements suppression rate was 38.7%.…”

Emerging trends in vibration control of wind turbines: a focus on a dual control strategy

“…Passive control techniques have been investigated for structural control of both onshore and offshore wind turbines [11][12][13]. One of the issues associated with the use of passive devices for wind turbine structural control is that they may become ineffective as a result of environmental/operational changes or in the presence of parametric variations.…”