Robust Observer-Based Load Extenuation Control for Wind Turbines

2019 ◽  
Author(s):  
M. Hung Do ◽  
Dirk Söffker
Keyword(s):  
Wind Turbines ◽  
Large Scale ◽  
Linear Models ◽  
Simulation Software ◽  
Control Algorithms ◽  
Linear Quadratic ◽  
Robust Observer ◽  
Wind Turbine Control ◽  
Speed Regulation ◽  
The Stability

Abstract Wind energy is currently the fastest growing electricity source. To meet the output demand, wind turbines are becoming larger and more flexible leading to the problems of structural load especially in case of offshore turbines. Advanced control algorithms are developed to reduce the load, allowing to build larger turbines, and expand their lifetime. Observer-based control algorithms such as Linear-Quadratic-Gaussian LQG control which uses LQR to calculate the optimal observer and controller gains are commonly applied to wind turbines in literature. However the approach requires to calculate the observer and control gains separately. In addition, linear models used for parameter calculation may have errors with respect to the nonlinearities of wind turbines and induced to unmodeled dynamical properties. These modeling errors need to be considered to to guarantee the stability of the controlled system. Alternatively a robust design assuming bounds and limits of models have to be realized to guarantee stability while ignoring details of modeling. This paper proposes an optimal robust observer-based state feedback controller for large-scale wind turbines to realize multi objectives, including structural load mitigation and rotor speed regulation. The novel contribution is that the observer gain parameters, control gains, and integral action are optimized at the same time within H∞ mixed sensitivity framework to achieve desired performance with respect to power regulation, structural load mitigation, and also robustness for the wind turbine control system. The control performances have been verified by a high fidelity simulation software and are compared to those of a classical baseline controller.

Nonlinear Systems Analysis and Control of Variable Speed Wind Turbines for Multiregime Operation

2014 ◽  
Vol 137 (4) ◽  
Author(s):  
Greg Semrau ◽  
Sigitas Rimkus ◽  
Tuhin Das
Keyword(s):  
Wind Speed ◽  
Nonlinear Systems ◽  
Wind Turbines ◽  
Control Input ◽  
Variable Speed ◽  
Wind Speeds ◽  
Speed Regulation ◽  
The Stability ◽  
Control Feedback ◽  
Operating Regimes

The key control problems associated with variable speed wind turbines are maximization of extracted energy when operating below the rated wind speed, and power and speed regulation when operating above the rated wind speed. In this paper, we develop a nonlinear systems framework to address these problems. The framework is used to visualize and analyze the equilibria of the wind turbine as its operating regimes and controllers change. For both below rated and above rated wind speeds, we adopt nonlinear controllers, analyze the stability property of the resulting equilibria, and establish the criterion for switching between control regimes. Further, the regions of attraction of the resulting equilibria are determined, and the existence of a common region of attraction, which allows stable switching between operating regimes, is shown. The control input maintains continuity at the point of switching. We next provide a method for blade pitch modulation to control rotor speed at high wind speeds. Through Lyapunov stability analysis, we prove stability of the equilibria in the presence of the two independently functioning torque- and pitch-control feedback loops. Simulation results are presented and the controller is compared with existing works from the literature.

Design of State-Space-Based Control Algorithms for Wind Turbine Speed Regulation

2003 ◽  
Vol 125 (4) ◽  
pp. 386-395 ◽  
Author(s):  
Alan D. Wright ◽  
Mark J. Balas
Keyword(s):  
Wind Turbine ◽  
State Space ◽  
Degrees Of Freedom ◽  
Linear Models ◽  
Pole Placement ◽  
Control Algorithms ◽  
Simulation Code ◽  
Speed Regulation ◽  
Full Load Operation ◽  
Turbine Speed

Control can improve the performance of wind turbines by enhancing energy capture and reducing dynamic loads. At the National Renewable Energy Laboratory, we are beginning to design control algorithms for regulation of turbine speed and power using state-space control designs. In this paper, we describe the design of such a control algorithm for regulation of rotor speed in full-load operation (Region 3) for a two-bladed wind turbine. We base our control design on simple linear models of a turbine, which contain rotor and generator rotation, drive train torsion, rotor flap (first mode only), and tower fore-aft degrees of freedom (DOFs). Wind-speed fluctuations are accounted for using Disturbance Accommodating Control (DAC). We show the capability of these control schemes to stabilize the modeled turbine modes via pole placement, while using state estimation to reduce the number of turbine measurements that are needed for these algorithms. These controllers are incorporated into a simulation code and simulated for various conditions. Finally, conclusions to this work and future studies are outlined.

Design of State-Space-Based Control Algorithms for Wind Turbine Speed Regulation

2002 ◽  
Author(s):  
Alan D. Wright ◽  
Mark J. Balas
Keyword(s):  
Wind Turbine ◽  
State Space ◽  
Degrees Of Freedom ◽  
Linear Models ◽  
Pole Placement ◽  
Control Algorithms ◽  
Speed Regulation ◽  
Full Load Operation ◽  
Turbine Speed ◽  
Speed Fluctuations

Control can improve the performance of wind turbines by enhancing energy capture and reducing dynamic loads. At the National Renewable Energy Laboratory, we are beginning to design control algorithms for regulation of turbine speed and power using state-space control designs. In this paper, we describe the design of such a control algorithm for regulation of rotor speed in full-load operation (region 3) for a two-bladed wind turbine. We base our control design on simple linear models of a turbine, which contain rotor and generator rotation, drivetrain torsion, and rotor flap degrees of freedom (first mode only). We account for wind-speed fluctuations using disturbance-accommodating control. We show the capability of these control schemes to stabilize the modeled turbine modes via pole placement, while using state estimation to reduce the number of turbine measurements that are needed for these control algorithms. We incorporate these controllers into the FAST_AD code and show simulation results for various conditions. Finally we report conclusions to this work and outline future studies.

scholarly journals Development and Characterization of Two Types of Surface Displayed Levansucrases for Levan Biosynthesis

Catalysts ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 757
Author(s):  
Huiyi Shang ◽  
Danni Yang ◽  
Dairong Qiao ◽  
Hui Xu ◽  
Yi Cao
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Molecular Weight ◽  
Large Scale ◽  
Surface Display ◽  
Yeast Surface Display ◽  
Fusion Partner ◽  
Whole Cell ◽  
Food Industries ◽  
Yeast Surface ◽  
The Stability

Levan has wide applications in chemical, cosmetic, pharmaceutical and food industries. The free levansucrase is usually used in the biosynthesis of levan, but the poor reusability and low stability of free levansucrase have limited its large-scale use. To address this problem, the surface-displayed levansucrase in Saccharomyces cerevisiae were generated and evaluated in this study. The levansucrase from Zymomonas mobilis was displayed on the cell surface of Saccharomyces cerevisiae EBY100 using a various yeast surface display platform. The N-terminal fusion partner is based on a-agglutinin, and the C-terminal one is Flo1p. The yield of levan produced by these two whole-cell biocatalysts reaches 26 g/L and 34 g/L in 24 h, respectively. Meanwhile, the stability of the surface-displayed levansucrases is significantly enhanced. After six reuses, these two biocatalysts retained over 50% and 60% of their initial activities, respectively. Furthermore, the molecular weight and polydispersity test of the products suggested that the whole-cell biocatalyst of levansucrase displayed by Flo1p has more potentials in the production of levan with low molecular weight which is critical in certain applications. In conclusion, our method not only enable the possibility to reuse the enzyme, but also improves the stability of the enzyme.

scholarly journals Optimal Design of Novel Blade Profile for Savonius Wind Turbines

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3484
Author(s):  
Tai-Lin Chang ◽  
Shun-Feng Tsai ◽  
Chun-Lung Chen
Keyword(s):  
Wind Energy ◽  
Drag Force ◽  
Wind Turbines ◽  
Rural Areas ◽  
Large Scale ◽  
Design Method ◽  
Angular Position ◽  
Vertical Axis ◽  
Blade Profile ◽  
Main Concept

Since the affirming of global warming, most wind energy projects have focused on the large-scale Horizontal Axis Wind Turbines (HAWTs). In recent years, the fast-growing wind energy sector and the demand for smarter grids have led to the use of Vertical Axis Wind Turbines (VAWTs) for decentralized energy generation systems, both in urban and remote rural areas. The goals of this study are to improve the Savonius-type VAWT’s efficiency and oscillation. The main concept is to redesign a Novel Blade profile using the Taguchi Robust Design Method and the ANSYS-Fluent simulation package. The convex contour of the blade faces against the wind, creating sufficient lift force and minimizing drag force; the concave contour faces up to the wind, improving or maintaining the drag force. The result is that the Novel Blade improves blade performance by 65% over the Savonius type at the best angular position. In addition, it decreases the oscillation and noise accordingly. This study achieved its two goals.

scholarly journals The Relationships Between Serum DHEA-S and AMH Levels in Infertile Women: A Retrospective Cross-Sectional Study

2021 ◽  
Vol 10 (6) ◽  
pp. 1211
Author(s):  
Li-Te Lin ◽  
Kuan-Hao Tsui
Keyword(s):  
Generalized Linear Models ◽  
Large Scale ◽  
Linear Models ◽  
Positive Association ◽  
Cross Sectional Study ◽  
Dehydroepiandrosterone Sulphate ◽  
Sectional Study ◽  
Cross Sectional ◽  
Infertile Women ◽  
The Relationship

The relationship between serum dehydroepiandrosterone sulphate (DHEA-S) and anti-Mullerian hormone (AMH) levels has not been fully established. Therefore, we performed a large-scale cross-sectional study to investigate the association between serum DHEA-S and AMH levels. The study included a total of 2155 infertile women aged 20 to 46 years who were divided into four quartile groups (Q1 to Q4) based on serum DHEA-S levels. We found that there was a weak positive association between serum DHEA-S and AMH levels in infertile women (r = 0.190, p < 0.001). After adjusting for potential confounders, serum DHEA-S levels positively correlated with serum AMH levels in infertile women (β = 0.103, p < 0.001). Infertile women in the highest DHEA-S quartile category (Q4) showed significantly higher serum AMH levels (p < 0.001) compared with women in the lowest DHEA-S quartile category (Q1). The serum AMH levels significantly increased across increasing DHEA-S quartile categories in infertile women (p = 0.014) using generalized linear models after adjustment for potential confounders. Our data show that serum DHEA-S levels are positively associated with serum AMH levels.

scholarly journals INTRACISTRONIC MAPPING OF ELECTROPHORETIC SITES IN DROSOPHILA MELANOGASTER: FIDELITY OF INFORMATION TRANSFER BY GENE CONVERSION

Genetics ◽  
1974 ◽  
Vol 76 (2) ◽  
pp. 289-299
Author(s):  
Margaret McCarron ◽  
William Gelbart ◽  
Arthur Chovnick
Keyword(s):  
Drosophila Melanogaster ◽  
Information Transfer ◽  
Large Scale ◽  
Genetic Basis ◽  
Xanthine Dehydrogenase ◽  
Specific Protein ◽  
Wild Type ◽  
Electrophoretic Variation ◽  
The Stability ◽  
Recombination Experiments

ABSTRACT A convenient method is described for the intracistronic mapping of genetic sites responsible for electrophoretic variation of a specific protein in Drosophila melanogaster. A number of wild-type isoalleles of the rosy locus have been isolated which are associated with the production of electrophoretically distinguishable xanthine dehydrogenases. Large-scale recombination experiments were carried out involving null enzyme mutants induced on electrophoretically distinct wild-type isoalleles, the genetic basis for which is followed as a nonselective marker in the cross. Additionally, a large-scale recombination experiment was carried out involving null enzyme rosy mutants induced on the same wild-type isoallele. Examination of the electrophoretic character of crossover and convertant products recovered from the latter experiment revealed that all exhibited the same parental electrophoretic character. In addition to documenting the stability of the xanthine dehydrogenase electrophoretic character, this observation argues against a special mutagenesis hypothesis to explain conversions resulting from allele recombination studies.

scholarly journals EEG Data Quality: Determinants and Impact in a Multicenter Study of Children, Adolescents, and Adults with Attention-Deficit/Hyperactivity Disorder (ADHD)

2021 ◽  
Vol 11 (2) ◽  
pp. 214
Author(s):  
Anna Kaiser ◽  
Pascal-M. Aggensteiner ◽  
Martin Holtmann ◽  
Andreas Fallgatter ◽  
Marcel Romanos ◽  
...  
Keyword(s):  
Data Quality ◽  
Large Scale ◽  
Linear Models ◽  
Spectral Power ◽  
Control Group ◽  
Continuous Performance Task ◽  
Related Data ◽  
Eyes Closed ◽  
Eeg Data ◽  
Eyes Open

Electroencephalography (EEG) represents a widely established method for assessing altered and typically developing brain function. However, systematic studies on EEG data quality, its correlates, and consequences are scarce. To address this research gap, the current study focused on the percentage of artifact-free segments after standard EEG pre-processing as a data quality index. We analyzed participant-related and methodological influences, and validity by replicating landmark EEG effects. Further, effects of data quality on spectral power analyses beyond participant-related characteristics were explored. EEG data from a multicenter ADHD-cohort (age range 6 to 45 years), and a non-ADHD school-age control group were analyzed (ntotal = 305). Resting-state data during eyes open, and eyes closed conditions, and task-related data during a cued Continuous Performance Task (CPT) were collected. After pre-processing, general linear models, and stepwise regression models were fitted to the data. We found that EEG data quality was strongly related to demographic characteristics, but not to methodological factors. We were able to replicate maturational, task, and ADHD effects reported in the EEG literature, establishing a link with EEG-landmark effects. Furthermore, we showed that poor data quality significantly increases spectral power beyond effects of maturation and symptom severity. Taken together, the current results indicate that with a careful design and systematic quality control, informative large-scale multicenter trials characterizing neurophysiological mechanisms in neurodevelopmental disorders across the lifespan are feasible. Nevertheless, results are restricted to the limitations reported. Future work will clarify predictive value.

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