Active Pitch Research Articles

Vibration Characteristics of a Rotating Composite Beam with Pitch Action and Hygrothermal Effects

The blades of helicopters and wind turbines undergo pitch motion in hygrothermal environments. Few works have studied the effect of this movement on blade frequencies. This paper focuses on the bending characteristics of a pitching thin-walled beam, including the effects of hygrothermal environments, rotor speeds, and composite materials. The harmonic pitch function is introduced into the dynamics model of a rotating beam. The method of multiple scales and the Galerkin method are used to solve these equations. Results indicate that the pitch amplitude A dramatically influences natural frequencies. Conclusions are obtained: (1) The flapping frequency varies periodically with pitch amplitude A, and monotonically changes every 2/[Formula: see text]. The pitch amplitude A significantly impacts frequencies, while the pitch frequency [Formula: see text] and pitch phase C don’t influence frequencies. (2) An increase in temperature or humidity will decrease the flapping frequencies of a pitching beam. (3) The ply angle, coupled with the dynamic pitching angle, dramatically influences the flapping frequencies of the composite beam. The larger the ply angle, the greater the effect of pitch amplitude A on frequencies.

On the robustness of a blade-load-based wind speed estimator to dynamic pitch control strategies

Abstract. In the context of wind turbine pitch control for load alleviation or active wake mixing, it is relevant to provide the time- and space-varying wind conditions as an input to the controller. Apart from classical wind measurement techniques, blade-load-based estimators can also be used to sense the incoming wind. These consider blades to be sensors of the flow and rely on having access to the operating parameters and measuring the blade loads. In this paper, we wish to verify how robust such estimators are to the control strategy active on the turbine, as it impacts both operating parameters and loads. We use an extended Kalman filter (EKF) to estimate the incoming wind conditions based on the blade bending moments. The internal model in the EKF relies on the blade element momentum (BEM) theory in which we propose accounting for delays between pitch action and blade loads by including dynamic effects. Using large-eddy simulations (LESs) to test the estimator, we show that accounting for the dynamic effects in the BEM formulation is needed to maintain the estimator accuracy when dynamic wake mixing control is active.

Performance similarities between standard and retrofit LiDAR-assisted control for wind turbines

LiDAR-assisted control has proven to be a highly effective method for mitigating rotor speed deviations and reducing loads in wind turbines. This effectiveness stems from the ability of feedforward controllers to utilize incoming wind speed information obtained from LiDARs, enabling advanced blade pitch actions before the wind disturbs the turbine. However, the standard implementation of LiDAR-assisted control often necessitates modifications to the existing feedback controller, where the feedforward pitch rate is typically integrated into the feedback controller. This process can be challenging in terms of accessibility and may be limited to specific stakeholders, such as turbine manufacturers.A retrofit design provides an ideal solution, where the retrofit LiDAR-assisted controller modifies the rotor speed measurement to induce pitch actions without requiring alterations to the existing feedback controller. This paper aims to demonstrate the performance similarities between the standard LiDAR-assisted controller and its retrofit counterpart. Specifically, we establish that the retrofit LiDAR-assisted controller, with appropriate tuning, is equivalent to its standard counterpart. This equivalence implies that architecturally dissimilar controllers can yield the same performance in terms of rotor speed deviations and tower load reductions. The presented findings are supported by results obtained from high-fidelity closed-loop turbine simulations.

Active power control of wind turbine based on fuzzy pitch control

With the continuous increase in wind power penetration rate, wind turbine generators (referred to as WTGs or wind turbines) need to have the capability of active power control (APC) to respond to grid power commands. To reduce the burden of pitch control on wind turbines, existing studies have adopted a technological approach that uses variable-speed operation of the wind rotor instead of pitch control. Typically, pitch control is only initiated at the speed boundaries to limit variable-speed operation within the speed range. However, due to the influence of factors such as wind speed, rotor speed and control parameters, there is a noticeable saturation phenomenon in pitch control at the speed boundaries, which can affect the variable-speed process of the wind rotor and APC performance within the speed range. Therefore, this paper determines whether blade pitch adjustment needs to be performed in advance when the wind turbine operates within the speed range based on the rotor speed state. This avoids the pitch action at the speed boundaries and the associated pitch saturation problem. The results show that the proposed method in this paper reduces the frequency of the rotor speed reaching the speed boundaries by performing pitch actions within the speed range. This alleviates the influence of pitch saturation on the variable-speed process of the wind rotor, as well as the occurrence of overspeed and electromagnetic power drop, thereby improving the APC performance of the wind turbine.

Research on Dynamic Capture and Pattern Recognition Technology of Pitching Technology in Baseball Sports

Abstract This paper proposes a baseball pitching action recognition algorithm based on a spatiotemporal graph convolutional neural network and constructs an error action correction algorithm on this basis. The dynamic skeleton model ST-GCN is used to combine the positional information of human movement with the temporal dynamic information. The action contour sequence is extracted to determine the funding for the erroneous action. Finally, the machine learning method is used to realize the adaptive corrective analysis of the erroneous action. Example analysis shows that the action correction algorithm proposed in this paper improves the recognition accuracy by 20.78%, 16.67%, and 9.11%, 9.73% in the two datasets, and the pitching accuracy of the experimental group is 12.5% higher than that of the control group, and the standardized degree score of the pitching technical action is 1.1 points higher than that of the control group. Therefore, the practical effectiveness of the pitching action identification and correction method in this paper has been effectively verified.

Research on wind turbine variable pitch control based on wind speed estimation

With the continuous promotion of the “double carbon” strategy, the capacity of wind turbines is increasing, and the dimensions of key parts such as the diameter of the wind turbine wheel, the height of the tower, and the radius of the tower tube are also increasing. Large wind turbines have a large inertia, so the execution time of the pitch actuator and the response time of the pitch action are usually longer, which leads to large fluctuations in the output power of the wind turbine when the wind speed changes rapidly under the working conditions above the rated wind speed and leads to complex loading problems. Therefore, in this paper, the design of pitch control is carried out by estimating the effective wind speed at the wind turbine surface and using the inverse system method to transform the nonlinear wind turbine system into a linear decoupled form. This method improves the pitch response speed, reduces the output power fluctuation, and better suppresses the load of the turbine to ensure the safe and stable operation of the turbine

Enhancing the Grid Support From DFIG-Based Wind Farms During Voltage Events

With the increasing penetration of renewable energy generators, the world is positively progressing toward the goal of sustainable development. However, the grid strength and inertia are decreasing due to the associated technological limitations. To this end, this research paper proposes a novel approach to enhance the support from DFIG-based wind farms with their existing capacity during critical events like voltage-ride-through. The effectiveness of the method is tested with a reactive power-prioritizing grid code of India. The proposed optimization framework achieves this objective in three stages. The first stage maximizes the wind farm's reactive power reserve in maximum power and de-loaded modes. The second stage uniquely distributes the control references to achieve minimal transitional pitch action between these modes for reduced wear and tear while honoring the maximum reactive power capability. The third stage generates lookup tables of control limits for maximal active power support within the grid code and the system constraints. The optimization is a one-time process for a specified farm geometry. Since the method is lookup table-based, the mode transitions are real-time feasible. The simulation test cases with the benchmark model demonstrate the efficacy of the proposed strategy, especially when the Wake Effect is prominent.

Active disturbance rejection control and multi-objective optimization for wind turbine active power regulation

Wind energy is anticipated to become a backbone of the future energy system and provide active power ancillary services. In this paper, a novel active power control (APC) scheme is proposed to deal with the active power regulation problem for the wind turbine. Firstly, an APC strategy dual-activating the pitch action and the rotor kinetic energy is designed to specify the reference signals of pitch angle and rotor speed. Next, a multi-variable controller based on active disturbance rejection control (ADRC) theory is proposed to implement the APC strategy, wherein the theoretical proof of the convergence result is provided. Then, a multi-objective coronavirus herd immunity optimization algorithm is proposed to find out the Pareto solution of controller parameter tuning, in which the power tracking accuracy and fatigue load mitigation are considered. Finally, the performance superiority of the proposed APC strategy is verified on a 5 MW OpenFAST wind turbine simulator in case of the IEC turbulence wind field and the reg-D standard test signal into account. Compared with the conventional pitch angle control and rotor speed control strategies, our APC scheme is able to accomplish the task of power regulation with smaller tracking root mean square error, shorter pitch travel and lighter fatigue load.

Peak shaving strategy for load reduction of wind turbines based on model predictive control

The protection control system determines the operation safety of wind turbines. The peak shaving controller can protect wind turbines by mitigating the thrust peak near the rated wind speed. However, the traditional controller is designed in the form of a look-up table, which leads to limitations in stability and regulation capability. Therefore, an improved strategy based on model predictive control is proposed to enhance the performance of peak shaving regulation. During each control period, the allowable pitch range is improved by solving the optimization problem in real-time. Firstly, the traditional peak shaving controller is introduced and analyzed in detail. Then, a peak shaving strategy based on model predictive control is put forward for thrust peak protection by providing additional pitch action. The controller is established in a closed-loop control framework by solving an open-loop optimization problem. Finally, systematic simulations are implemented based on a high fidelity model in Bladed. As a result, it is demonstrated that the strategy can reduce the thrust peak to the safe range at the expense of acceptable output power. In addition, the proposed controller can relieve the alternating load in the peak shaving range and mitigate fatigue loads of key components.

On LiDAR-assisted wind turbine retrofit control and fatigue load reductions

The use of upstream wind speed measurement has motivated the development of LiDAR-assisted control for enhancing rotor speed tracking and fatigue structural load reductions. However, conventional LiDAR-assisted control designs often require altering the existing controller architecture, for example, by sending an additional feed-forward pitch angle signal to the pitch actuator or by incorporating the feed-forward pitch rate into the feedback controller. This work proposes LiDAR-assisted retrofit control solutions that can be implemented without any prior knowledge or modifications of the existing feedback controller. Specifically, the feed-forward pitch action is provoked by modifying the rotor speed measurement. Three retrofit methods are proposed according to the level of retrofit requirement and complexity. Numerical simulation results showed that all three LiDAR-assisted retrofit solutions could achieve good thrust-related load reductions. Thus, the proposed LiDAR-assisted retrofit solutions present a simple control upgrade to extend the lifetime of existing turbines.

Medial elbow joint space gapping associated with repetitive baseball pitching in preadolescent baseball players.

The baseball pitching motion creates valgus stress to the medial elbow, which contributes to increased medial elbow joint space gapping. The musculoskeletal systems of preadolescent baseball players are immature compared with those of adults, but it is unclear whether the repetitive pitching action causes an increase in medial elbow joint space gapping. This study aimed to examine differences in medial elbow joint space gapping based on the pitch count of preadolescent baseball players compared with those of adult players. The participants were 11 healthy preadolescent baseball players and 12 college students with baseball experience. They threw 60 maximal-effort pitches arranged into 4 sets of 15 pitches. The medial elbow joint space was measured ultrasonographically with the forearm weight before pitching and following every set of 15 pitches. Repeated-measures analysis of variance and the Bonferroni post hoc test were used to compare the medial elbow joint space among the 5 pitching sets (before pitching and after 15, 30, 45, and 60 pitches) and between the groups of preadolescent baseball players and college students. There was no significant change in the medial elbow joint space gapping of the dominant elbow based on age/pitch count (F=0.42, P=.796). There was a significant effect of pitch count (F=30.28, P<.001) and between-group effects (F=4.56, P=.045). The medial elbow joint space gapping increased significantly after 60 pitches in preadolescent baseball players (P=.023) and college students (P=.021). The medial elbow joint space gapping in preadolescent baseball players was significantly wider than that in college students (P=.007 before pitching, P=.027 at 15 pitches). Sixty repetitive pitches contributed to an increase in the medial elbow joint space gapping, regardless of age. The results of this study provide further evidence when considering pitching limitations.

Relationship between scapular control during isometric shoulder flexion and scapular motion during baseball pitching: a cross-sectional study

BackgroundA baseball pitcher with decreased scapular control may not be able to achieve suitable scapular motion at maximum shoulder external rotation (MER) of baseball pitching during the pitching action. It is common clinically to compare scapular control of the throwing and non-throwing arms to detect side-to-side differences. However, it remains unclear whether scapular control is different between the throwing and non-throwing arms. Moreover, no data exist on the relationship between scapular control and scapular motion at MER of pitching. Primarily, this study aimed to compare scapular control during isometric shoulder flexion between the throwing and non-throwing arms. Secondly, this study aimed to investigate the relationship between scapular control during isometric shoulder flexion and scapular motion at MER of pitching.MethodsFifteen healthy collegiate baseball pitchers (age, 20.2 ± 1.9 years; height, 1.76 ± 0.05 m; body mass, 73.3 ± 6.7 kg) were recruited. An optical motion tracking system was used to assess scapular motion. Scapular control was defined as the amount of change in the scapular internal rotation angle, downward rotation angle, and anterior tilt angle during isometric shoulder flexion. We assessed scapular position at MER of pitching.ResultsNo significant differences were detected for any of the scapular angles during isometric shoulder flexion between the throwing and non-throwing arms. The amount of change in the scapular internal rotation angle, scapular downward rotation angle, and scapular anterior tilt angle during isometric shoulder flexion had a significant relationship with the scapular downward rotation angle at MER.ConclusionsNo side-to-side difference was noted in scapular control during isometric shoulder flexion in healthy collegiate baseball pitchers at the group level. Further studies are required to understand the side-to-side differences at the individual level. Additionally, there was a relationship between scapular control during isometric shoulder flexion and scapular position at MER. These findings suggest that clinicians may consider using isometric shoulder flexion to assess scapular control in baseball pitchers.

Real-Time testing of novel robust digital pitch controller for digital hydraulic pitch system in wind turbine

ABSTRACT This research work draws insight on developing a novel digital hydraulic pitch system for a large-scale wind turbine. Digital hydraulic pitching can be appropriate for wind turbine application due to its high response, high power-to-weight ratio, and robustness. To perform digital pitch control, a machine learning-based robust digital pitch controller was designed and implemented in the developed real-time test setup. The proposed real-time test setup consist of sub-systems such as digital hydraulic system hardware, real-time interface, robust digital pitch controller, and 5 MW benchmark wind turbine model. Real-time testing was conducted on proposed controller using the developed test setup. Robustness test exhibited robust pitch control tracking when subjected to high wind gusts/fluctuations. In this test, the proposed controller reduced the pitch control error (mean absolute) by 68.10% and 51.75% when compared to feed forward and Elman controller, respectively. Subsequently, a power regulation test was performed on the proposed controller under real-time turbulence wind speed. Relative to the feed-forward and Elman controller, the proposed controller regulates power close to the rated value and improved the mean generator power by 3.39%, and 3.72%, respectively. A comparative study conducted with existing controllers (in the literature) demonstrate the superior performance of the proposed controller. This study reports that intelligent digital pitching action of proposed controller generates power close to rated power when compared to existing controllers in the literature.

Active Power Control of Wind Turbine Generators Based on the Maximum Disturbance Range of Nonpitch Regulation

Wind turbine generators (WTG) are expected to provide active power control (APC) to track active power instructions from the power grid or wind farm operators. Because the regulation of turbines’ mechanical dynamics strongly depends on pitch angle regulation, mitigating frequent pitch adjustments is a key issue, and accordingly, several rotor speed variation-first APC methods have been proposed to decrease pitch servo fatigue. However, due to the lack of a quantitative description on the utilization of rotor speed variation (RSV), the ability of reducing pitch action through RSV can hardly be analyzed and compared among the existing APC methods. Hence, the disturbance range of nonpitch regulation (DRNP) and the maximum DRNP are defined in this paper. The former represents the effect of pitch action mitigation through RSV with a specific APC strategy and provides a unified foundation for quantitatively evaluating and selecting APC methods from the perspective of pitch servo serviceability. The latter, which depends on the turbine specifications and is independent of the control method, represents the maximum effect that can be achieved for a WTG. On this basis, an improved APC method is proposed to further reduce pitch servo fatigue. Finally, the DRNP indicators and the effectiveness and feasibility of the proposed method are verified by the wind turbine simulator-based experiments.

Full Operational Envelope Control of a Wind Turbine Using Model Predictive Control

This study presents a full operational envelope controller for a full nonlinear 5 MW Supergen exemplar wind turbine based on multivariable model predictive control (MPC). Below the rated wind speed, the primary objective of the controller is to maximize the energy capture. Above the rated wind speed, the controller maintains the rated power. The controller switches between control modes according to the prevailing wind speed to maintain control over the full envelope of operating regions. A linearized model is derived from a model of an exemplar 5 MW Supergen wind turbine in state-space form. The linearized model is then used to realize a feedback MPC (FB-MPC) and feedforward MPC (FF-MPC) to consider the lack and incorporation, respectively, of wind speed information. The switching strategy is tracked on the torque–speed plane. Simulations are performed at multiple wind speeds to evaluate the robustness and switching performances of the designed controllers by applying them to a full nonlinear 5 MW Matlab/SIMULINK model of the same exemplar Supergen wind turbine. Improved tracking is achieved over the full envelope with FF-MPC rather than FB-MPC. Simulation results are presented in the time and frequency domain in addition to the torque–speed plane demonstrating that the control performance is improved without an increase in the control activity (i.e., pitch action) of the turbine; that is, the controller’s gain crossover frequency remains within the acceptable range, around 1 rad/s. Note that most work presented in the literature focus on specific wind speeds only; that is, either only below rated wind speed or above rated wind speed. In contrast, the controllers reported here cover the full envelope of operation regions, making this work more practical and novel.

Flutter Suppression of Wind Turbine Blade based on Adaptive Fuzzy Sliding Mode Control

Aiming at the divergent unstable vibration of wind turbine blades, an adaptive fuzzy sliding mode control algorithm based on sliding mode control is proposed to solve the classic flutter fracture failure problem of blades. The structural model is a typical blade section model based on spring-mass-damper, and the aeroelastic equation is obtained by combining the steady aerodynamic model suitable for pure pitch motion. The adaptive fuzzy sliding mode controller gives the pitch signal, and the second-order pitch actuator performs the pitch action to suppress flutter. The saturation function with variable boundary layer thickness is used instead of symbolic function, and the approach rate parameter is adjusted appropriately by fuzzy rules, so as to realize variable-parameter adaptive fuzzy sliding mode control. Simulation results show that, compared with the traditional sliding mode controller, the proposed control algorithm can not only suppress the classical flutter, but also effectively reduce the amplitude and frequency of chattering, and has good robustness.

Fuzzy Logic-based Digital Hydraulics Control of Blade Pitch Angle in Wind Turbines

The pitch control system is generally employed in a wind turbine to mitigate load and maintain uniform power generation at above-rated wind speed regions. The hydraulic system has more power to weight ratio and so it is incorporated in the pitch system of large scale wind turbines. Some of the issues related to the usage of conventional valves in the Hydraulic Pitch System (HPS) are: internal leakage, throttling losses, high power loss, less fault-tolerant, requires high manufacturing tolerance, and more sensitive to contamination. To overcome these issues, digital hydraulics technology should be introduced as Digital Hydraulics Pitch System (DHPS). Commercially, Proportional Integral Derivative (PID) controller is used as a pitch controller but these controller performances don’t hold good when excessive disturbance or change in operating point occurs in the system. So, heuristic-based Fuzzy Logic Controller (FLC) is preferred which can surpass the PID problems. In this paper, a heuristic FLC based control strategy is proposed for a novel DHPS configuration to control the pitching action. The simulation model of DHPS is developed and system simulations are conducted. The comparative study on the effectiveness of FLC for DHPS and conventional valve controlled HPS is conducted.

Fuzzy Logic based Digital Hydraulics Control of Blade Pitch Angle in Wind Turbines

Pitch control system is generally employed in wind turbine to mitigate load and maintain uniform power generation at above-rated wind speed regions. Hydraulic system has more power to weight ratio and so it is incorporated in the pitch system of large scale wind turbines. Some of the issues related to the usage of conventional valves in Hydraulic Pitch System (HPS) are: internal leakage, throttling losses, high power loss, less fault-tolerant, requires high manufacturing tolerance and more sensitive to contamination. In order to overcome these issues, digital hydraulics technology should be introduced as Digital Hydraulics Pitch System (DHPS). Commercially, Proportional Integral Derivative (PID) controller is used as pitch controller but these controller performance doesn’t hold good when excessive disturbance or change in operating point occurs in the system. So, heuristic-based Fuzzy Logic Controller (FLC) is preferred which has the ability to surpass the PID problems. In this paper, heuristic FLC based control strategy is proposed for a novel DHPS configuration to control the pitching action. Simulation model of DHPS is developed and system simulations are conducted. The comparative study on the effectiveness of FLC for DHPS and conventional valve controlled HPS is conducted.

Design and implementation of an intelligent digital pitch controller for digital hydraulic pitch system hardware-in-the-loop simulator of wind turbine

ABSTRACT Digital hydraulics is a potential technology for the Hydraulic Pitch System (HPS) in Wind Turbine (WT). Digital Hydraulics Pitch System (DHPS) uses Digital Flow Control Units (DFCU) to develop the precise pitching action. In this paper, a novel Intelligent Digital Pitch Controller (IDPC) is proposed. The proposed controller is designed and implemented on a developed lab-scale DHPS Hardware-in-the-Loop (HIL) simulator. The various parameters of DHPS-hardware were designed using the bottom-up design methodology. The IDPC comprises Machine Learning (ML)-based WECS and DHPS controllers in the outer and inner loop respectively. HIL simulations were conducted with the implemented IDPC. The ML-based WECS controller predicts the reference pitch angle close to its desired value. The ML-based DHPS controller predicts the states of DFCU to develop real-time pitching action in DHPS-hardware. Several case studies were conducted to validate the effectiveness of the proposed IDPC. A study shows that IDPC controlled DHPS exhibits better performance than an ML-Proportional Integral (PI) controlled HPS with proportional flow control valve. Subsequently, the performance of the IDPC is compared with PI-ML cascade controller. This study shows that the Maximum Absolute Error (MAE) between the generator speed and its rated speed is 0.87% and 19.29% for the proposed controller and PI-ML cascade controller, respectively. Similarly, MAE (error between generator torque and its rated torque) of torque is 0.85% and 5.46% for the proposed controller and PI-ML cascade controller, respectively. Thus, the implementation of the IDPC develops optimal power with minimal speed/torque fluctuations.

A Comparison of Multi-Objective Optimisation of Two Wind Turbine Controller Designs

This paper presents a comparison between two pitch controllers for a 10MW wind turbine, a baseline using PI and a state-space model, where each controller’s parameters have been chosen using Bayesian optimization. Four objectives are simultaneously examined: energy output; pitch action; blade load; and tower load. First, it is shown that, for both controllers, using parameters selected from the obtained Pareto fronts achieves higher energy production with less energy consumption of pitch activities and with less load in blade and tower, compared with settings chosen by an expert. Second, in this robust comparison of the capabilities of both controllers, the increased degrees of freedom and reduced simplification in the more advanced controller are seen to have greater potential to improve each of the objectives.