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The floating offshore wind turbines (FOWTs) have many more advantages than the onshore wind turbines, but they also have more complicated aerodynamic characteristics due to complex platform motions. The research objective of this paper is to investigate unsteady aerodynamic characteristics of a FOWT under the pitch, yaw, and coupled pitch–yaw platf...
Citations
... The energy from photovoltaic installations is considered one of the most promising renewable sources [1]. However, the variable nature of production in photovoltaic installations, similar to wind power plants, significantly affects the quality of the energy transmitted in power grids [2,3]. The quality of electricity supply is a set of parameters that describe the features of the process of supplying energy to the user under normal operating conditions [4]. ...
Over the last few years, a dynamic increase in the installed capacity of distributed energy sources has been observed, with the largest share being photovoltaic sources. The power grid is a system of connected vessels, and changing the structure of electricity production has a specific impact on the operation of this network, which makes it necessary to study the impact of the sources on the power system. The current and projected increase in the number of connected installations will make the issues of interaction and cooperation of distributed sources with the network extremely important. The article presents an analysis of the impact of a photovoltaic farm on selected parameters of the quality of electricity supply. This analysis was made on the basis of simulation results in a computer program and measurement tests carried out on a real photovoltaic farm with a capacity of 1.8 MW connected to the medium voltage power grid. The impact of the farm-generated power on the values of fundamental indicators of the quality of electricity supply, such as voltage deviations, voltage asymmetry factors, and voltage distortions factors, is presented. These relationships were determined based on the correlation and regression analysis of individual electrical quantities.
... Wang et al. [32] proposed a dynamic yaw model to study the changes of AOA and force on blade sections; besides, the variation of rotor power during start-stop yawing rotation was also considered in details. Chen et al. [33] developed a coupled pitch-yaw wind turbine motion model based on their previous study, and it is noted that the mean values of thrust and power are independent of the motion frequency while the corresponding amplitudes are affected. ...
... This phenomenon is not considered previously to the best knowledge of the authors. Besides, even though the aerodynamic analyses of a horizontal-axis wind turbine were widely conducted previously [27][28][29][30][31][32][33][34][35][36][37][38], the effects of yawed inflow and tower on the local aerodynamic characteristics (e.g., local blade load, AOA, induce factor) of different blade sections within a rotation period are still not investigated, which is of great significance to capture the aerodynamic performance of a wind turbine and evaluate the fatigue damage of a blade accurately. In this study, these issues mentioned in the above will be clarified in details. ...
The aerodynamic characteristics of a wind turbine change dramatically under the influence of complex inflow and interaction between blade and tower. In this study, detailed full-scale CFD models of NREL 5 MW wind turbine are developed to investigate the specific aerodynamic characteristics with varying yaw angles and wind speeds based on OpenFOAM tool box. The total and local blade aerodynamic loads are analyzed by incorporating the effects of yawed inflow and tower. It is clearly noted that the blade load fluctuation amplitude and influence range due to the presence of tower gradually increase when the yaw angle becomes larger. Moreover, the three-point method is employed to extract the angle of attack (AOA) and induce factor of different blade sections within a rotation period. Generally, the fluctuation amplitudes of AOA and induce factor increase with the increase of yaw angle by ignoring the abrupt change induced by the tower shadow effect. Subsequently, the effects of blade rotation on the aerodynamic force of tower for varying wind speeds and yaw angles are considered, and a “negative pressure” state is observed when the blade passes in front of the tower. Finally, the wake effect under yawed inflow is revealed in details.
... Compared to BEM, FVM effectively simulated the unsteady flow around the rotor blades. Chen et al. (2021) employed computational fluid dynamics (CFD) technique in unsteady Reynolds Averaged Navier-Stokes (URANS) simulations for investigation of unsteady aerodynamic characteristics of a floating offshore wind turbine operating under pitch, yaw, and coupled pitch-yaw platform motions. Angle of attack (AOA) on the rotors was observed to be more sensitive to yaw motion; normal and tangential forces on the rotors were induced by pitch motion while aerodynamic loads were more sensitive to pitch motion, which was confirmed from the thrust force and torque of the rotors during the platform motions. ...
Different forces and loads are induced on turbine blade geometric coordinates as a result of multi-rotational motions of an offshore wind which expose the rotor blades to fatigue stresses. In this study, multi-rotational motions (yaw, pitch and roll) in a Windfield domain acting across an offshore wind turbine blade was simulated (using Aerodynamic and Aeroelastic FAST simulation module in QBlade software), and the resultant forces they induce on the geometric coordinates of the blade at various wind velocities ranging from 0-3.9, 0-8.1, 0-12.3 and 0-16.4 m/s were considered. From the results, roll motion which developed the highest aerodynamic forces and induced highest stresses on the blade is responsible for axial forces acting on the vertical direction (x-axis), yaw motion is responsible for vertical forces acting on the vertical direction (z-axis) of the blade while pitch motion is responsible for lateral forces acting on the lateral direction (y-axis) of the blade during rotation. It was observed that resultant forces at each of the aforementioned range of wind velocities increased significantly at mid-span of the rotor blade, moderately at the root of the blade and almost insignificantly at the blade tip. These translated to maximum stress concentrations of 1.16, 2.30, 5.62 and 11.2 MPa induced by yaw motion, 1.31, 3.12, 7.38 and 13.6 MPa induced by pitch motion and 2.41, 3.84, 10.5 and 15.5 induced by roll motion. These stresses were observed to occur around the mid-section of the blade at each of the aforementioned wind velocities. Hence, the mid-section of a wind turbine blade is highly prone to aerodynamic forces due to wind velocities which induce fatigue stresses that eventually expose the blade to unforeseen failure depending on severity of the forces. Hence, the mid-span of a wind turbine rotor blade should be reinforced with spars and shear webs characterised by high resistance to shear force.
... As a result, wind energy has also become a trendy field of research. Research topics can be divided into wind prediction and productivity forecasts [1,2], efficiency (optimization) of power generation [3][4][5][6][7], and the impact of power plants on the environment [8,9]. The subject matter of this paper falls within the scope of research concerning the influence of wind power plants on the quality of energy supplied to consumers located in the direct vicinity of the power plant. ...
Wind power plants are an increasingly common source of electricity located in rural areas. As a result of the high variability of wind power, and thus the generated power, these sources should be classified as unstable sources. In this paper, the authors attempted to determine the impact of wind turbine operation on the parameters of electricity supplied to farms located near the source. As a result of the conducted field tests, variability courses of the basic parameters describing the supply voltage were obtained. The influence of power plant variability on the values of voltage, frequency, and voltage distortion factor was determined. To estimate the capacity of the transmission lines, the reactive power produced in the power plant and its effect on the value of the power factor were determined. The conducted research and analysis showed that the wind power plant significantly influences voltage fluctuations in its immediate vicinity (the maximum value registered was close to 2%, while the value required by law was 2.5%). Although all the recorded values are within limits specified by the current regulations (e.g., the THD value is four times lower than the required value), wind turbines may cause incorrect operation of loads connected nearby. This applies mainly to cases where consumers sensitive to voltage fluctuations are installed in the direct vicinity of the power plant.
... Fang [20,21] applied a 1:50 model FOWT to explore the aerodynamics and characteristics of its wake under surge and pitch motions. Chen [22,23] investigated the aerodynamic characteristics of the wind turbine under surge-pitch coupling and pitch-yaw coupling by the combination of dynamic mesh and sliding mesh. The results show that the fluctuation of the overall aerodynamic performance of the wind turbine dramatically with the increase of amplitude and frequency. ...
The aerodynamic performance of the floating offshore wind turbine (FOWT) is obviously affected by the motion of the platform, and becomes much more complicated considering the effect of tower shadow. In view of this, this paper aims at investigating the aerodynamic performance of the floating offshore wind turbine with and without a tower under the three most influential motions (surge, pitch and yaw) by computational fluid dynamic (CFD). The results show that the power of the wind turbine is reduced by 1.58% to 2.47% due to the tower shadow effect under the three motions, and the pressure difference distribution is most obviously interfered by the tower shadow effect under yaw motion and concentrates at the root and tip of the blade. In addition, the degree of interference of the tower shadow effect on the wake flow field is different under the three motions, resulting in a more complex wake structure. These conclusions can provide a theoretical basis and technical reference for the optimal design of floating offshore wind turbines.
... With the development of floating offshore wind turbines over the world, their reliability and dynamic performance requirements have gradually increased [13,14]. Although vector control theory can be used to convert a doubly-fed floating offshore wind turbine system into a linear system. ...
This paper proposes a current decoupling controller for a Doubly-fed Induction Generator (DFIG) based on floating offshore wind turbine and power to gas. The proposed controller realizes Maximum Power Point Tracking (MPPT) through integral sliding mode compensation. By using the internal model control strategy, an open-loop controller is designed to ensure that the system has good dynamic performance. Furthermore, using the integral Sliding Mode Control (SMC) strategy, a compensator is designed to eliminate the parameter perturbation and external disturbance of the open-loop control. The parameters of the designed controller are designed through Grey Wolf Optimization (GWO). Simulation results show that the proposed control strategy has better response speed and smaller steady-state error than the traditional control strategy. This research is expected to be applied to the field of hydrogen production by floating offshore wind power.
This review comprehensively examines advancements in Computational Fluid Dynamics (CFD) applications within the context of Floating Offshore Wind Turbines (FOWTs). It highlights the role of CFD in both hydrodynamics and aerodynamics, underscoring its significance in analyzing FOWT performance. The discussion includes a range of prototypes, encompassing various FOWT platforms and wind turbines, along with a comparative assessment of scale effects. Distinct features of diverse CFD software, comprising open-source, commercial, and in-house solvers, are critically analyzed. The review delves deeply into hydrodynamic CFD applications, addressing aspects like viscous damping, numerical wave tanks, and wave-induced motions. In aerodynamics, it explores wake flow, complex inflow, blade-tower interactions, etc. The intricate challenges of coupled aero-hydrodynamics in FOWTs are also summarized, emphasizing the confluence of aerodynamic and hydrodynamic forces. Concluding with an outlook on future trends and emerging challenges in FOWT dynamics, the paper proposes directions for ongoing research and development in this swiftly progressing sector. This review aims to be a valuable reference for both researchers and engineers, providing a comprehensive overview of current CFD applications and their crucial contribution to the advancement of FOWT technology.
An accurate prediction of the unsteady loads acting on floating offshore wind turbines (FOWTs) under consideration of wave excitation is crucial for a resource-efficient turbine design. Despite a considerable number of simulation studies in this area, it is still not fully understood which unsteady aerodynamic phenomena have a notable influence on the loads acting on a wind turbine rotor in motion. In the present study, investigations are carried out to evaluate the most relevant unsteady aerodynamic phenomena for a wind turbine rotor in surge motion. As a result, inflow conditions are determined for which a significant influence of these phenomena on the rotor loads can be expected. The experimental and numerical investigations are conducted on a two-bladed wind turbine rotor subjected to a tower-top surge motion. A specialised wind tunnel test rig has been developed to measure the aerodynamic torque response of the rotor subjected to surge motions with moderate frequencies. The torque measurements are compared to two free-vortex-wake (FVW) methods, namely a panel method and a lifting-line method. Unsteady contributions that cannot be captured using quasi-steady modelling have not been detected in either the measurements or the simulations in the covered region of motions ranging from a rotor reduced frequency of 0.55 to 1.09 and with motion velocity amplitudes of up to 9 % of the wind speed. The surge motion frequencies were limited to a moderate range (5 to 10 Hz) due to vibrations occurring in the experiments. Therefore, a numerical study with an extended range of motion frequencies using the panel and the lifting-line method was performed. The results from both FVW methods reveal significant unsteady contributions of the surge motions to the torque and thrust response that have not been reported in the recent literature. Furthermore, the results show the presence of the returning wake effect, which is known from helicopter aerodynamics. Additional simulations of the UNAFLOW scale model and the IEA 15 MW rotor demonstrate that the occurrence of the returning wake effect is independent from the turbine but determined by the ratio of 3P and surge motion frequency. In the case of the IEA 15 MW rotor, a notable impact of the returning wake effect was found at surge motion frequencies in the range of typical wave periods. Finally, a comparison with OpenFAST simulations reveals notable differences in the modelling of the unsteady aerodynamic behaviour in comparison to the FVW methods.
An accurate prediction of the unsteady loads acting on floating offshore wind turbines (FOWT) under consideration of wave excitation is crucial for a resource-efficient turbine design. Despite a considerable number of simulation studies in this area, it is still not fully understood, which unsteady aerodynamic phenomena have a notable influence on the loads acting on a wind turbine rotor in motion. In the present study, investigations are carried out to evaluate of the most relevant unsteady aerodynamic phenomena for a wind turbine rotor in surge motion. As a result, inflow conditions are determined for which a significant influence of these phenomena on the rotor loads can be expected. The experimental and numerical investigations are conducted on a two-bladed wind turbine rotor subjected to a tower top surge motion. A specialised wind tunnel test rig has been developed to measure the aerodynamic torque response of the rotor subjected to surge motions with moderate frequencies. The torque measurements are compared to two free vortex wake methods, namely a panel and a lifting-line method. Unsteady contributions that cannot be captured using quasi-steady modelling have not been detected in either the measurements or the simulations in the covered region of motion frequencies. The surge motion frequencies were limited to a moderate range due to vibrations occurring in the experiments. Therefore, a numerical study with an extended the range of motion frequencies using the panel and the lifting-line method was performed. The results reveal significant unsteady contributions of the surge motions to the torque and thrust response that cannot be modelled in a quasi-steady way. Furthermore, the results show the presence of the returning wake effect, which is known from helicopter aerodynamics. Additional simulations of the UNAFLOW scale model and the IEA 15 MW rotor demonstrate that the occurrence of the returning wake effect is independent from the turbine, but determined by the ratio of rotor speed and surge motion. In case of the IEA 15 MW, a notable impact of the returning wake effect was found at surge motion frequencies in the range of typical wave periods. Finally, a comparison with OpenFAST simulations reveals notable differences in the modelling of the unsteady aerodynamic behaviour in comparison to a FVW method.
