Blade Pitch Angle Control for Floating Offshore Wind Turbines by Model Predictive Control

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.

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Model predictive control for floating offshore wind turbines with failure compensation using individual blade pitch control

2015 15th International Conference on Control, Automation and Systems (ICCAS) ◽

10.1109/iccas.2015.7364584 ◽

2015 ◽

Cited By ~ 1

Author(s):

Flavien Thiery ◽

Naoyuki Hara ◽

Keiji Konishi

Keyword(s):

Model Predictive Control ◽

Predictive Control ◽

Wind Turbines ◽

Offshore Wind ◽

Offshore Wind Turbines ◽

Pitch Control ◽

Floating Offshore Wind Turbines

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

IEEJ Transactions on Electronics Information and Systems ◽

10.1541/ieejeiss.134.1096 ◽

2014 ◽

Vol 134 (8) ◽

pp. 1096-1103 ◽

Cited By ~ 8

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

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Fatigue Damage to the Spar-Type Offshore Floating Wind Turbine Under Blade Pitch Controller Faults

Volume 9A: Ocean Renewable Energy ◽

10.1115/omae2014-23235 ◽

2014 ◽

Cited By ~ 1

Author(s):

Mahmoud Etemaddar ◽

Elaheh Vahidian ◽

Otto Skjåstad

Keyword(s):

Wind Turbine ◽

Fatigue Damage ◽

Wind Turbines ◽

Pitch Angle ◽

Offshore Wind ◽

Offshore Wind Turbines ◽

Composite Blade ◽

Floating Wind Turbine ◽

Offshore Floating Wind Turbine ◽

Blade Pitch Angle

The safety and reliability margin of offshore floating wind turbines need to be higher than that of onshore wind turbines due to larger environmental loads and higher operational and maintenance costs for offshore wind turbines compared to onshore wind turbines. However rotor cyclic loads coupled with 6 DOFs motions of the substructure, amplifies the fatigue damage in offshore floating wind turbines. In general a lower fatigue design factor is used for offshore wind turbines compared to that of the stationary oil and gas platforms. This is because the consequence of a failure in offshore wind turbines in general is lower than that of the offshore oil and gas platforms. In offshore floating wind turbines a sub-system fault in the electrical system and blade pitch angle controller also induces additional fatigue loading on the wind turbine structure. In this paper effect of selected controller system faults on the fatigue damage of an offshore floating wind turbine is investigated, in a case which fault is not detected by a fault detection system due to a failure in the fault detection system or operator decided to continue operation under fault condition. Two fault cases in the blade pitch angle controller of the NREL 5MW offshore floating wind turbine are modeled and simulated. These faults include: bias error in the blade pitch angle rotary encoder and valve blockage or line disconnection in the blade pitch angle actuator. The short-term fatigue damage due to these faults on the composite blade root, steel low-speed shaft, tower bottom and hub are calculated and compared with the fatigue damage under normal operational conditions considering same environmental conditions for both cases. This comparison shows that how risky is to work under the fault conditions which could be useful for wind turbine operators. The servo-hydro-aeroelastic code HAWC2 is used to simulate the time domain responses of the spar-type offshore floating wind turbine under normal and faulty operational conditions. The rain-flow cycle counting method is used to calculate the load cycles under normal operational and fault conditions. The short term fatigue damage to the composite blade root and steel structures are calculated for 6-hour reference period. The bi-linear Goodman diagram and a linear SN curve are used to estimate the fatigue damage to the composite blade root and the steel structures respectively. Moreover the fatigue damage for different mean wind speeds, sea states and fault amplitudes are calculated to figure out the region of wind speeds operation with the highest risk of damage.

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A study on the platform-pitching vibration of floating offshore wind turbines based on classical control theory

Wind Engineering ◽

10.1177/0309524x19862761 ◽

2019 ◽

Vol 44 (6) ◽

pp. 610-630

Author(s):

Hiromu Kakuya ◽

Shigeo Yoshida ◽

Iku Sato ◽

Tomoaki Utsunomiya

Keyword(s):

Transfer Function ◽

Vibration Control ◽

Pitch Angle ◽

Offshore Wind ◽

Floating Platform ◽

Offshore Wind Turbines ◽

Floating Offshore Wind Turbines ◽

Classical Control ◽

The Impact ◽

Blade Pitch Angle

One of the issues of floating offshore wind turbines is the platform-pitching vibration generated by the blade pitch angle motion of the variable speed control. This study investigated the platform-pitching vibration based on the classical control theory using a transfer function between the generator speed and the nacelle pitch angle. This study also investigated the impact of the floating platform vibration control, which can suppress the vibration by adjusting the blade pitch angle according to the nacelle pitch angle, by using a transfer function to which floating platform vibration control is added. The stabilities of these transfer functions were determined using the Nyquist stability criterion, and the impact of the floating platform vibration control parameters was investigated using Bode diagrams.

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