Reconstructing coupled blade pitch moments of large wind turbines using multidimensional copula-based method

Small-scale H-Darrieus turbine ( HDT ) often struggles to reach self-sustained power producing speed due to low start-up torque. Low torque is sometimes manifested in the form of torque plateau or ‘ dead band ’. To improve torque development, turbine design variables such as blade chord-to-radius ratio ( c/r ) and solidity ( σ ) play critical role. To understand the effect of c/r only, this study analyses turbines with identical σ but different c/r using unsteady computational fluid dynamics ( CFD) . Results show that larger c/r enhances torque by influencing the leading-edge flow and vortex formation and convection. Two mechanisms are identified: (i) amplification of the variation of incidence angle along blade chord, effectively acting as aerofoil-camber morphing, and (ii) high blade pitch rate effect, especially at low λ (<1) where intra-cycle pitching is significant. These findings highlight the sensitivity of torque generation to c/r , offering design guidance for improving HDT start-up performance.

The advent of electric propulsion for new aircraft designs necessitates the optimization of propeller aerodynamic performance and the reduction of acoustic signatures. Variable-pitch propellers present a promising solution, offering the flexibility to adjust blade angles in response to different flight conditions. The study investigates the performance of blade pitch configurations tailored to specific flight conditions. Rather than a dynamic pitch change, the research evaluates discrete pitch settings coupled with corresponding advance ratios to identify optimal operating points. Findings show that increasing collective pitch in response to a higher advance ratio (forward flight) successfully maintains aerodynamic efficiency and thrust, with an expected increase in torque. While this adjustment leads to an anticipated rise in noise due to higher aerodynamic loading, results reveal that a collective pitch increment of +5° actively suppresses broadband noise at frequencies above 2 kHz. Analysis of the flow field and surface pressure fluctuations indicates this suppression is directly attributed to the mitigation of outboard propeller stall. Ultimately, this work demonstrates the feasibility of using collective pitch adjustments not only to enhance flight performance but also to actively control and suppress components of the propeller noise signature, such as the broadband noise.

Operational expenditure in wind farms is heavily influenced by unplanned maintenance, much of which stems from undetected rotor system faults. Although many fault-detection methods have been proposed, most remain confined to laboratory test. Blade-root bending-moment measurements are among the few techniques applied in the field, yet their reliability is limited by strong sensitivity to varying operational and environmental conditions. This study presents a data-driven rotor health-monitoring framework that enhances the diagnostic value of blade bending-moments. Assuming that the wind speed profile remains approximately stationary over short intervals (e.g., 20 s), a machine-learning model is trained on bending-moment data from healthy blades to predict the incident wind-speed profile under a wide range of conditions. During operation, real-time bending-moment signals from each blade are independently processed by the trained model. A healthy rotor yields consistent wind-speed profile predictions across all three blades, whereas deviations for an individual blade indicate rotor asymmetry. In this study, the methodology is verified using high-fidelity OpenFAST simulations with controlled blade pitch misalignment as a representative fault case, providing simulation-based verification of the proposed framework. Results demonstrate that the proposed inverse-modeling and cross-blade consistency framework enables sensitive and robust detection and localization of pitch-related rotor faults. While only pitch misalignment is explicitly investigated here, the approach is inherently applicable to other rotor asymmetry mechanisms such as mass imbalance or aerodynamic degradation, supporting reliable condition monitoring and earlier maintenance interventions. Using OpenFAST simulations, the proposed framework reconstructs height-resolved wind profiles with RMSE below 0.15 m/s (R² > 0.997) under healthy conditions, and achieves up to 100% detection accuracy for moderate-to-severe pitch misalignment faults.

ABSTRACT There are versatile design scenarios for load assessment of an offshore wind turbine. Under an accidental scenario of earthquakes, extreme structural loads may occur during an emergency shutdown characterized by fast blade pitching. The present study investigates the effect of sensor thresholds on dynamic responses during emergency shutdowns. Nacelle accelerometers in fore-aft and side-side directions are assumed to be the sensors triggering shutdown and two thresholds (1 m/s2 and 2 m/s2) are considered. Fully coupled numerical simulations are carried out for a 5-megawatt offshore wind turbine under wind, waves, and an earthquake. Dynamic characteristics of the wind turbine are compared for the shutdown scenario and the reference scenario of normal operation during the earthquake. Observations are discussed using spectral plots and load ratios evaluated for time segments before threshold crossing (detection delay) and shutdown duration. Results demonstrate that code guidelines for implementing a shutdown during the strong ground motion part of the earthquake may not be physically pragmatic and consistent across possible shutdown scenarios. The tower-top loads under the shutdown scenario can be approximately 1.7 times higher than those under the reference scenario. Results indicate that the nacelle fore-aft sensor with the lower threshold has the lowest structural loads. It is recommended to use the sensor in the side-side direction to trigger shutdown for early detection of seismic behavior for adequate decoupling of maximum seismic loads and the shutdown procedure.

Blade Pitch Control Strategy for Floating Wind Turbines Based on Fractional Order PIDD2

This paper investigates the amplitude-dependent characteristics of the TiltRotor Aeroelastic Stability Testbed. The recovery rate, multiple decay Prony averaging, and Stockwell transform methods are employed to account for system nonlinearities, which are neglected by conventional test data analysis methods based on linear assumptions. A comprehensive study of ground vibration and wind tunnel test data highlights reduced local damping and frequency at larger response amplitudes for various blade materials, rotor speeds, and pitch–flap coupling parameters. This study demonstrates novel analysis capabilities to investigate nonlinear dynamics in tiltrotors and support their design.

The development of offshore wind power projects is gradually shifting from shallow waters to deep waters. However, in the transitional water-depth areas between the two, both traditional fixed and floating offshore wind turbines have certain technical and cost drawbacks. This manuscript proposes an articulated foundation offshore wind turbine suitable for transitional water depths of approximately 40–70 m, builds an aerodynamic–hydrodynamic–structural multibody coupling model with ADRT program, and analyzes its responses under normal and extreme conditions. The results indicate that under power generation conditions, wave loads dominate the foundation pitch angle, tower-top offset, and blade flapwise deformation. Meanwhile, the second-order difference-frequency wave force in the wave loads amplifies the low-frequency pitch response, and the sum-frequency force excites the high-frequency natural vibration of the tower column. The tower-top displacement and blade edgewise response are mainly affected by the aerodynamic load of the rotor. Turbulent winds significantly increase the response standard deviation and induce low-frequency resonance. Under survival conditions, the system response is dominated by wave loads. The blade stopping position and turbulent wind have a relatively small impact on the system response, while gravity has a significant effect on the blade edgewise deformation.

Vibration suppression in floating offshore wind turbines after blade pitch control system failure using tuned mass damper

Blade Pitch Control for Floating Wind Turbines via Event-Triggered Model-Free Adaptive Control Strategy

Improving vertical axis wind turbine starting performance by active control blade pitching to combined using lift-drag force

ABSTRACT This paper presents a grid connected Brushless Doubly‐Fed Reluctance Generator (BDFRG) based wind energy conversion system. It offers a reliable and cost‐effective solution since its brushless and cage‐less rotor structure eliminates the need for slip rings, reducing maintenance costs, improving efficiency, robust in nature, and more reliable than other wind turbine generators. The BDFRG has two separate windings which are mounted on the stator namely the power winding and control winding: power winding connects to grid whereas the control winding connects to grids via partially‐rated back‐to‐back converter. This partially‐rated converter comprises of dual separately converters namely Grid Side converter (GSC) and Machine Side Converter (MSC). A field‐oriented vector control scheme is proposed for MSC to Variable Speed Constant Frequency (VSCF) action at fluctuating velocity of wind and a grid voltage‐oriented vector control scheme is considered for GSC to maintain constant voltage across DC‐link capacitor and also to obtain unity power factor of the system by managing no reactive power drift between grid and GSC. Maximum power point tracker (MPPT) and blade pitch angle control technique are also incorporated with the control structure of the MSC to obtain full power from the variable wind velocity and limit the winds generated power at its desired rate when the wind speed exceeds its rated value. The study system is modeled mathematically and implemented in MATLAB/Simulink (2021a) environment to observe the efficacy of the proposed control schemes under rated, below rated and above rated wind velocity. The hardware set‐up is developed for the study system and both control schemes are successfully executed in the Field‐Programmable Gate Array (FPGA) platform for experimental set‐up. Results show the efficacy of the proposed scheme and also provide good responses by showing reduced oscillation during transient, also it offers minimal steady‐state error in response to variations in input sources.

At present, few studies focus on variable-pitch fans for small-to-medium turbofan engines, with most relying on hydraulic actuation that fails to meet strict environmental and efficiency demands. This paper analyzes an electrically actuated lead-screw servo-motor-driven variable-pitch fan rotor: at 1×10⁷ N/m support stiffness, the first critical speed exceeds the operational range and pitch angle’s influence is negligible, peak unbalance response is 1.22×10⁻⁶ m linearly decreasing with pitch angle, and vibration analysis avoids resonance. Results confirm the electric pitch-change concept’s feasibility.

Collective and individual blade pitch control strategy for floating wind turbines based on improved ALO and fractional order PIDD2

The growing demand for renewable energy has amplified the need for efficient and reliable wind turbine technologies, where understanding aerodynamic performance and aeroelastic behavior plays a critical role. In this study, a high-fidelity computational fluid dynamics (CFD) model was developed to analyze the aerodynamic loads and structural responses of a 2 kW horizontal-axis wind turbine, while an artificial neural network (ANN) was trained using CFD-generated data to predict power output and aeroelastic characteristics. The work combines ANN predictions and CFD simulations to determine the feasibility of machine learning as a surrogate model, which is much less expensive in terms of computational costs and time, with no negative effects on the accuracy. Findings indicate ANN predictions are closely comparable to CFD results with under 5–7% deviation at optimal blade pitch angles, which was shown to be very reliable in capturing nonlinear aerodynamic trends at different wind speeds and blade pitch angles. In addition, the obtained result emphasizes the example of the trade-off between aerodynamic efficiency and structural safety, where the largest power coefficient (0.42) was achieved at 0° pitch and the tip deflections were reduced by almost 60% as the pitch was raised to 5°. Such results substantiate the usefulness of ANN-based methods in the rapid aerodynamic and aeroelastic simulation of wind turbines and provide a prospective direction for effectively designed wind power generation and optimization.

Abstract Gas turbine operation requires air to be extracted from the primary compressor flow path for a variety of purposes, including turbine cooling and off-design stage matching. This “bleed air” is typically extracted through the compressor casing using either: a continuous circumferential slot; or discrete holes, each with a diameter on the order of a blade pitch. In this article, the benefits of extracting air through an array of holes on the stator blade suction surface, each with a diameter on the order of 1% of the blade chord, are identified. Such blades are referred to as aspirated compressor blades. Using a combined experimental and computational approach, two findings are presented. First, the operating range of the aspirated compressor blade is widened through the control of corner separations. The aspiration reduces the streamline curvature of the surface limiting streamlines, inhibiting corner separation formation. This control is sensitive to air removal through aspiration holes close to the endwall where the separation is expected to occur, with increased air extraction in this region further extending the stator operating range. The second finding is that the loss of the integrated compressor passage and bleed system can be reduced by extracting air via a combined circumferential bleed slot and aspirated compressor blade approach. This article shows that using aspirated compressor blades can increase the operating range of a stator by 1.8 deg in experimental measurements, and, in simulations, increase the adiabatic efficiency of a three-stage representative industrial gas turbine compressor by 3 percentage points.

At low wind speeds, H-Darrieus wind turbines suffer from pronounced cyclic variations in the blade angle of attack (AoA), triggering premature dynamic stall and impeding self-starting capability. These aerodynamic instabilities, combined with high cyclic loading, compromise both energy extraction efficiency and structural durability, presenting a critical barrier to the adoption of H-Darrieus technology. While fixed or dynamic pitch control strategies can mitigate excessive AoA fluctuations, their comparative effectiveness remains poorly characterized. This study systematically evaluates four pitch control strategies including zero-pitch, fixed-pitch, sinusoidal pitch, and helical blade configurations to assess their impact on the aerodynamic performance of a small-scale, three-bladed H-Darrieus rotor operating at 7 m/s wind speed. A high-fidelity 3D unsteady aerodynamic model, combining a lifting line approach with a free vortex wake method, is employed to resolve transient flow phenomena and blade-wake interactions. Results demonstrate that a sinusoidal pitch modulation strategy amplifies torque generation by almost six times compared to the zero-pitch baseline, while fixed-pitch configurations show negligible efficiency gains. Notably, negative fixed-pitch angles outperform their positive counterparts in torque production. Furthermore, blade helicity is shown to reduce aerodynamic load fluctuations by 22%, offering dual benefits in efficiency enhancement and structural load mitigation. These findings provide actionable insights for optimizing pitch control strategies in small-scale vertical-axis wind turbines, particularly in urban and low-wind environments.

Sediment erosion is a persistent problem that leads to the deterioration of hydro-turbines over time, ultimately causing blade failure. This paper analyzes the dynamics of sediment in water and its effects on a small Kaplan turbine. Flow data is obtained independently and transferred to a separate Lagrangian-based finite element code, which tracks particles throughout the computational domain to determine local impacts and erosion rates. This solver uses a random walk approach, along with statistical descriptions of particle sizes, numbers, and release positions. The turbine runner features significantly twisted blades with rounded corners, and complex three-dimensional (3-d) flow related to leakage and secondary flows. The results indicate that flow quality, particle size, concentration, and the relative position of the blades against the vanes significantly influence the distribution of impacts and erosion intensity, subsequently the local eroded mass is cumulated for each element face and averaged across one pitch of blades. At the highest concentration of 2500 mg/m3, the results show a substantial erosion rate from the rotor blades, quantified at 4.6784 × 10−3 mg/h and 9.4269 × 10−3 mg/h for the nominal and maximum power operating points, respectively. Extreme erosion is observed at the leading edge (LE) of the blades and along the front part of the pressure side (PS), as well as at the trailing edge (TE) near the hub corner. The distributor vanes also experience erosion, particularly at the LE on both sides, although the erosion rates in these areas are less pronounced. These findings provide essential insights into the specific regions where protective coatings should be applied, thereby extending the operational lifespan and enhancing overall resilience against sediment-induced wear.

In this study, the effect of various parameters on the power coefficient (CP) performance of a vertical axis wind turbine (VAWT) was optimized using the Taguchi method. The optimization was conducted with the Taguchi method, employing three control factors: blade-spoke connection (BSC), turbine blade pitch angle (β) and turbine blade pitch direction (φ). Subsequently, the Analysis of Variance (ANOVA) method was employed to determine the contribution ratio of each control factor. Regression Analysis (RA) was applied to develop an empirical equation predicting the CP of the VAWT, incorporating the control factors. The results indicated an optimal parameter configuration of BSC=0.5c, β=2°, and φ= (-), which maximizes the system's performance. The performance of the optimal model was observed to exceed that of the conventional VAWT (B1) by a 5.82%. Using the ANOVA method, the contribution of parameters on the CP performance of the VAWT was ranked as follows: φ > BSC > β. The φ parameter has the most significant effect at 82.07%, whereas the β parameter with the least effect of 1.17%. Moreover, the predictive accuracy of the developed regression model was validated, yielding R² values of 0.9221 for the training data and 0.9908 for the test data.

Adaptive Integral Backstepping Control for Blade Pitch Angle Tracking in a Distributed Electric Propulsion Based Cycloidal Rotor