Stabilization of floating offshore wind turbines by artificial muscle based active mooring line force control

2016 ◽  
Author(s):  
Yaoyu Li ◽  
Zhongyou Wu
Keyword(s):  
Wind Turbines ◽  
Force Control ◽  
Artificial Muscle ◽  
Offshore Wind ◽  
Mooring Line ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Line Force

Wind/Wave Misalignment Effects on Mooring Line Tensions for a Spar Buoy Wind Turbine

2018 ◽  
Author(s):  
Luigia Riefolo ◽  
Fernando del Jesus ◽  
Raúl Guanche García ◽  
Giuseppe Roberto Tomasicchio ◽  
Daniela Pantusa
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Wave ◽  
Offshore Wind ◽  
Mooring Line ◽  
Ultimate Limit State ◽  
International Electrotechnical Commission ◽  
Wave Loads ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

The design methodology for mooring systems for a spar buoy wind turbine considers the influence of extreme events and wind/wave misalignments occurring in its lifetime. Therefore, the variety of wind and wave directions affects over the seakeeping and as a result the evaluation of the maxima loads acting on the spar-buoy wind turbine. In the present paper, the importance of wind/wave misalignments on the dynamic response of spar-type floating wind turbine [1] is investigated. Based on standards, International Electrotechnical Commission IEC and Det Norske Veritas DNV the design of position moorings should be carried out under extreme wind/wave loads, taking into account their misalignments with respect to the structure. In particular, DNV standard, in ‘Position mooring’ recommendations, specifies in the load cases definition, if site specific data is not available, to consider non-collinear environment to have wave towards the unit’s bow (0°) and wind 30° relative to the waves. In IEC standards, the misalignment of the wind and wave directions shall be considered to design offshore wind turbines and calculate the loads acting on the support structure. Ultimate Limit State (ULS) analyses of the OC3-Hywind spar buoy wind turbine are conducted through FAST code, a certified nonlinear aero-hydro-servo-elastic simulation tool by the National Renewable Energy Laboratory’s (NREL’s). This software was developed for use in the International Energy Agency (IEA) Offshore Code Comparison Collaborative (OC3) project, and supports NREL’s offshore 5-MW baseline turbine. In order to assess the effects of misaligned wind and wave, different wind directions are chosen, maintaining the wave loads perpendicular to the structure. Stochastic, full-fields, turbulence simulator Turbsim is used to simulate the 1-h turbulent wind field. The scope of the work is to investigate the effects of wind/wave misalignments on the station-keeping system of spar buoy wind turbine. Results are presented in terms of global maxima determined through mean up-crossing with moving average, which, then, are modelled by a Weibull distribution. Finally, extreme values are estimated depending on global maxima and fitted on Gumbel distribution. The Most Probable Maximum value of mooring line tensions is found to be influenced by the wind/wave misalignments. The present paper is organized as follows. Section ‘Introduction’, based on a literature study, gives useful information on the previous studies conducted on the wind/wave misalignments effects of floating offshore wind turbines. Section ‘Methodology’ describes the applied methodology and presents the spar buoy wind turbine, the used numerical model and the selected environmental conditions. Results and the corresponding discussion are given in Section ‘Results and discussion’ for each load case corresponding to the codirectional and misaligned wind and wave loads. Results are presented and discussed in time and frequency domains. Finally, in Section ‘Conclusion’ some conclusions are drawn.

scholarly journals Digital twins of the mooring line tension for floating offshore wind turbines to improve monitoring, lifespan, and safety

2021 ◽  
Author(s):  
Jake Walker ◽  
Andrea Coraddu ◽  
Maurizio Collu ◽  
Luca Oneto
Keyword(s):  
Wind Turbines ◽  
Wind Farm ◽  
Mechanical Response ◽  
Offshore Wind ◽  
Mooring Line ◽  
Offshore Wind Turbines ◽  
Axial Tension ◽  
Floating Offshore Wind Turbines ◽  
Extreme Load ◽  
Operational Data

AbstractThe number of installed floating offshore wind turbines (FOWTs) has doubled since 2017, quadrupling the total installed capacity, and is expected to increase significantly over the next decade. Consequently, there is a growing consideration towards the main challenges for FOWT projects: monitoring the system’s integrity, extending the lifespan of the components, and maintaining FOWTs safely at scale. Effectively and efficiently addressing these challenges would unlock the wide-scale deployment of FOWTs. In this work, we focus on one of the most critical components of the FOWTs, the Mooring Lines (MoLs), which are responsible for fixing the structure to the seabed. The primary mechanical failure mechanisms in MoLs are extreme load and fatigue, both of which are functions of the axial tension. An effective solution to detect long-term drifts in the mechanical response of the MoLs is to develop a Digital Twin (DT) able to accurately predict the behaviour of the healthy system to compare with the actual one. Moreover, we will develop another DT able to accurately predict the near future axial tension as an effective tool to improve the lifespan of the MoLs and the safety of FOWT maintenance operations. In fact, by changing the FOWT operational settings, according to the DT prediction, operators can increase the lifespan of the MoLs by reducing the stress and, additionally, in the case where FOWT operational maintenance is in progress, the prediction from the DT can serve as early safety warning to operators. Authors will leverage operational data collected from the world’s first commercial floating-wind farm [the Hywind Pilot Park (https://www.equinor.com/en/what-we-do/floating-wind/hywind-scotland.html.)] in 2018, to investigate the effectiveness of DTs for the prediction of the MoL axial tension for the two scenarios depicted above. The DTs will be developed using state-of-the-art data-driven methods, and results based on real operational data will support our proposal.

scholarly journals Assessment of Wind Turbine Aero-Hydro-Servo-Elastic Modelling on the Effects of Mooring Line Tension via Deep Learning

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2264 ◽  
Author(s):  
Zi Lin ◽  
Xiaolei Liu
Keyword(s):  
Deep Learning ◽  
Wind Turbines ◽  
Environmental Conditions ◽  
Line Tension ◽  
Offshore Wind ◽  
Mooring Line ◽  
Offshore Wind Turbines ◽  
Wind Speeds ◽  
Study Results ◽  
Floating Offshore Wind Turbines

As offshore wind turbines are moving to deeper water depths, mooring systems are becoming more and more significant for floating offshore wind turbines (FOWTs). Mooring line failures could affect power generations of FOWTs and ultimately incur risk to nearby structures. Among different failure mechanics, an excessive mooring line tension is one of the most essential factors contributing to mooring failure. Even advanced sensing offers an effective way of failure detections, but it is still difficult to comprehend why failures happened. Unlike traditional parametric studies that are computational and time-intensive, this paper applies deep learning to investigate the major driven force on the mooring line tension. A number of environmental conditions are considered, ranging from cut in to cut out wind speeds. Before formatting input data into the deep learning model, a FOWT model of dynamics was simulated under pre-defined environmental conditions. Both taut and slack mooring configurations were considered in the current study. Results showed that the most loaded mooring line tension was mainly determined by the surge motion, regardless of mooring line configurations, while the blade and the tower elasticity were less significant in predicting mooring line tension.

Hybrid Model Predictive Control of Floating Offshore Wind Turbines with Artificial Muscle Actuated Mooring Lines

2022 ◽  
Author(s):  
Zhongyou Wu ◽  
Yaoyu Li
Keyword(s):  
Model Predictive Control ◽  
Hybrid Model ◽  
Predictive Control ◽  
Wind Turbines ◽  
Artificial Muscle ◽  
Offshore Wind ◽  
Half Cycle ◽  
Platform Motion ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

Abstract Floating offshore wind turbines (FOWTs) are subject to undesirable platform motion and significant increase in fatigue loads compared to their onshore counterparts. We have recently proposed using the Fishing Line Artificial Muscle (FLAM) actuators to realize active mooring line force control (AMLFC) for platform stabilization and thus load reduction, which features compact design and no need for turbine redesign. However, as for the thermally activated FLAM actuators, a major control challenge lies in the asymmetric dynamics for the heating and the cooling half cycle of operation. In this paper, for a tension-leg platform (TLP) based FOWT with FLAM actuator based AMLFC, a hybrid dynamic model is obtained with platform pitch and roll degrees of freedom included. Then a hybrid model predictive control (HMPC) strategy is proposed for platform motion stabilization, with preview information on incoming wind and wave. A move blocking scheme is used to achieve reasonable computational efficiency. FAST based simulation study is performed using the NREL 5 MW wind turbine model. Under different combinations of wind speed, wave height and wind directions, simulation results show that the proposed control strategy can significantly reduce the platform roll and tower-base side-to-side bending moment, with mild level of actuator power consumption.

scholarly journals Global analysis of floating offshore wind turbines with shared mooring system

2021 ◽  
Vol 1201 (1) ◽  
pp. 012024
Author(s):  
H Munir ◽  
C F Lee ◽  
M C Ong
Keyword(s):  
Wind Turbines ◽  
Time Domain ◽  
Global Analysis ◽  
Cost Effective ◽  
Offshore Wind ◽  
Mooring Line ◽  
Mooring System ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Restoring Stiffness

Abstract Floating wind turbines (FWTs) with shared mooring systems can be one of the most cost- effective solutions in reducing mooring costs. First, the static configuration of a shared line is estimated using the elastic catenary equation. The present study investigates the global responses of two FWT with a shared mooring system. Two shared mooring configurations with different horizontal distances between the FWTs are considered. In the first configuration, the FWTs are placed 750m apart; and in the second configuration, they are placed 1000m apart. Two different environmental conditions (ECs) are used to simulate the global responses of the system in time domain. The shared mooring line results in higher extreme motions in surge and sway (degree of freedoms) DOFs due to the reduction of mooring restoring stiffness. The lower mooring restoring stiffness can be attributed to the reduction of one seabed anchoring point for each FWT as compared to a single FWT with three anchors installed. In the rotational DOFs, the shared mooring line configurations result in slight mean offset in each direction and significant increase in the motion standard deviations. This is caused by the reduced mooring stiffness associated with the change in platform orientation.

Pitch Angle Control of Floating Offshore Wind Turbines by H∞ Control

2014 ◽  
Vol 134 (8) ◽  
pp. 1096-1103 ◽  
Author(s):  
Sho Tsujimoto ◽  
Ségolène Dessort ◽  
Naoyuki Hara ◽  
Keiji Konishi
Keyword(s):  
Wind Turbines ◽  
Pitch Angle ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines

scholarly journals Impact of Typhoons on Floating Offshore Wind Turbines: A Case Study of Typhoon Mangkhut

2021 ◽  
Vol 9 (5) ◽  
pp. 543
Author(s):  
Jiawen Li ◽  
Jingyu Bian ◽  
Yuxiang Ma ◽  
Yichen Jiang
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Safety Evaluation ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Motion Response ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Coupling Motion

A typhoon is a restrictive factor in the development of floating wind power in China. However, the influences of multistage typhoon wind and waves on offshore wind turbines have not yet been studied. Based on Typhoon Mangkhut, in this study, the characteristics of the motion response and structural loads of an offshore wind turbine are investigated during the travel process. For this purpose, a framework is established and verified for investigating the typhoon-induced effects of offshore wind turbines, including a multistage typhoon wave field and a coupled dynamic model of offshore wind turbines. On this basis, the motion response and structural loads of different stages are calculated and analyzed systematically. The results show that the maximum response does not exactly correspond to the maximum wave or wind stage. Considering only the maximum wave height or wind speed may underestimate the motion response during the traveling process of the typhoon, which has problems in guiding the anti-typhoon design of offshore wind turbines. In addition, the coupling motion between the floating foundation and turbine should be considered in the safety evaluation of the floating offshore wind turbine under typhoon conditions.

scholarly journals Performance Analysis on the Use of Oscillating Water Column in Barge-Based Floating Offshore Wind Turbines

Mathematics ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 475
Author(s):  
Payam Aboutalebi ◽  
Fares M’zoughi ◽  
Izaskun Garrido ◽  
Aitor J. Garrido
Keyword(s):  
Wind Turbines ◽  
Positive Impact ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Water Columns ◽  
Numerical Tools ◽  
Oscillating Water Columns ◽  
The Given ◽  
The Waves

Undesired motions in Floating Offshore Wind Turbines (FOWT) lead to reduction of system efficiency, the system’s lifespan, wind and wave energy mitigation and increment of stress on the system and maintenance costs. In this article, a new barge platform structure for a FOWT has been proposed with the objective of reducing these undesired platform motions. The newly proposed barge structure aims to reduce the tower displacements and platform’s oscillations, particularly in rotational movements. This is achieved by installing Oscillating Water Columns (OWC) within the barge to oppose the oscillatory motion of the waves. Response Amplitude Operator (RAO) is used to predict the motions of the system exposed to different wave frequencies. From the RAOs analysis, the system’s performance has been evaluated for representative regular wave periods. Simulations using numerical tools show the positive impact of the added OWCs on the system’s stability. The results prove that the proposed platform presents better performance by decreasing the oscillations for the given range of wave frequencies, compared to the traditional barge platform.

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