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.

Nonlinear Control of Variable Speed Wind Turbines With Switching Across Operating Regimes

2011 ◽  
Author(s):  
Tuhin Das ◽  
Greg Semrau ◽  
Sigitas Rimkus
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Equilibrium Points ◽  
Control Input ◽  
Variable Speed ◽  
Nonlinear Controller ◽  
Wind Speed Profile ◽  
Control Laws ◽  
Wind Speeds ◽  
Operating Regimes

One of the key control problems associated with variable speed wind turbine systems is maximization of energy extraction when operating below the rated wind speed and power regulation when operating above the rated wind speed. In this paper, we approach these problems from a nonlinear systems perspective. For below rated wind speeds we adopt existing work appearing in the literature and provide further insight into the characteristics of the resulting equilibrium points of the closed-loop system. For above rated wind speeds, we propose a nonlinear controller and analyze the stability property of the resulting equilibria. We also propose a method for switching between the two operating regimes that ensures continuity of control input at the transition point. The control laws are verified using a wind turbine model with a standard turbulent wind speed profile that spans both operating regimes.

SHAPING OF AN AUTONOMOUS POWER SYSTEM FOR GUARANTEED POWER SUPPLY WITH THE PREDOMINANCE WIND ENERGY

2018 ◽  
pp. 28-50
Author(s):  
S. G. Ignatiev ◽  
S. V. Kiseleva
Keyword(s):  
Energy Storage ◽  
Wind Speed ◽  
Wind Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Energy Demand ◽  
Diesel Generator ◽  
Average Wind Speed ◽  
Wind Speeds ◽  
Average Wind

Optimization of the autonomous wind-diesel plants composition and of their power for guaranteed energy supply, despite the long history of research, the diversity of approaches and methods, is an urgent problem. In this paper, a detailed analysis of the wind energy characteristics is proposed to shape an autonomous power system for a guaranteed power supply with predominance wind energy. The analysis was carried out on the basis of wind speed measurements in the south of the European part of Russia during 8 months at different heights with a discreteness of 10 minutes. As a result, we have obtained a sequence of average daily wind speeds and the sequences constructed by arbitrary variations in the distribution of average daily wind speeds in this interval. These sequences have been used to calculate energy balances in systems (wind turbines + diesel generator + consumer with constant and limited daily energy demand) and (wind turbines + diesel generator + consumer with constant and limited daily energy demand + energy storage). In order to maximize the use of wind energy, the wind turbine integrally for the period in question is assumed to produce the required amount of energy. For the generality of consideration, we have introduced the relative values of the required energy, relative energy produced by the wind turbine and the diesel generator and relative storage capacity by normalizing them to the swept area of the wind wheel. The paper shows the effect of the average wind speed over the period on the energy characteristics of the system (wind turbine + diesel generator + consumer). It was found that the wind turbine energy produced, wind turbine energy used by the consumer, fuel consumption, and fuel economy depend (close to cubic dependence) upon the specified average wind speed. It was found that, for the same system with a limited amount of required energy and high average wind speed over the period, the wind turbines with lower generator power and smaller wind wheel radius use wind energy more efficiently than the wind turbines with higher generator power and larger wind wheel radius at less average wind speed. For the system (wind turbine + diesel generator + energy storage + consumer) with increasing average speed for a given amount of energy required, which in general is covered by the energy production of wind turbines for the period, the maximum size capacity of the storage device decreases. With decreasing the energy storage capacity, the influence of the random nature of the change in wind speed decreases, and at some values of the relative capacity, it can be neglected.

Determination of rated wind speed for maximum annual energy production of variable speed wind turbines

2017 ◽  
Vol 205 ◽  
pp. 781-789 ◽  
Author(s):  
Ahmad Sedaghat ◽  
Arash Hassanzadeh ◽  
Jamaloddin Jamali ◽  
Ali Mostafaeipour ◽  
Wei-Hsin Chen
Keyword(s):  
Wind Speed ◽  
Wind Turbines ◽  
Energy Production ◽  
Variable Speed

scholarly journals Wind Turbulence Intensity at La Ventosa, Mexico: A Comparative Study with the IEC61400 Standards

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3007 ◽  
Author(s):  
C. Lopez-Villalobos ◽  
O. Rodriguez-Hernandez ◽  
R. Campos-Amezcua ◽  
Guillermo Hernandez-Cruz ◽  
O. Jaramillo ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Turbines ◽  
Turbulence Intensity ◽  
Structural Damage ◽  
Atmospheric Stability ◽  
Design Parameters ◽  
Power Sector ◽  
Wind Speeds ◽  
Technical Solutions ◽  
Large Wind

Wind speed turbulence intensity is a crucial parameter in designing the structure of wind turbines. The IEC61400 considers the Normal Turbulence Model (NTM) as a reference for fatigue load calculations for small and large wind turbines. La Ventosa is a relevant region for the development of the wind power sector in Mexico. However, in the literature, there are no studies on this important parameter in this zone. Therefore, we present an analysis of the turbulence intensity to improve the understanding of local winds and contribute to the development of reliable technical solutions. In this work, we experimentally estimate the turbulence intensity of the region and the wind shear exponent in terms of atmospheric stability to analyze the relation of these design parameters with the recommended standard for large and small wind turbines. The results showed that the atmosphere is strongly convective and stable in most of the eleven months studied. The turbulence intensity analysis showed that for a range of wind speeds between 2 and 24 m/s, some values of the variable measured were greater than those recommended by the standard, which corresponds to 388 hours of turbulence intensity being underestimated. This may lead to fatigue loads and cause structural damage to the technologies installed in the zone if they were not designed to operate in these wind speed conditions.

Analysis of Wind Field Fan Based on Performance Enhancement Method

2014 ◽  
Vol 986-987 ◽  
pp. 235-238
Author(s):  
Xiao Long Tan ◽  
Jia Zhou ◽  
Wen Bin Wang
Keyword(s):  
Wind Speed ◽  
Wind Turbines ◽  
Performance Enhancement ◽  
Aerodynamic Performance ◽  
Wind Load ◽  
Wind Speeds ◽  
Enhancement Method ◽  
Changes Over Time ◽  
Load Simulation ◽  
Single Constant

For the simulation of wind turbine, the wind speed is extremely important parameters and indicators to measure the output power of the unit is the wind load. Therefore, in the airflow dynamics and simulation of wind loads before establishing an accurate wind speed model is crucial. At present, the application for wind turbines COMSOL fan, fan blades and wind load simulation field, the extremely important wind speed model is not perfect, most of the research is confined to a single constant wind speed, wind speed virtually ignored the magnitude and direction of change, on changes over time and space at the same time is one of the few studies of wind, so find a way to accurately describe the range of wind speeds, and can be combined well with COMSOL method can greatly improve the aerodynamic performance of wind turbines the overall level of .

scholarly journals Analysis of the Patent of a Protective Cover for Vertical-Axis Wind Turbines (VAWTs): Simulations of Wind Flow

2020 ◽  
Vol 12 (18) ◽  
pp. 7818
Author(s):  
Jose Alberto Moleón Baca ◽  
Antonio Jesús Expósito González ◽  
Candido Gutiérrez Montes
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Turbines ◽  
High Speed ◽  
Experimental Tests ◽  
Weather Conditions ◽  
Vertical Axis ◽  
Good Alternative ◽  
Wind Speeds ◽  
Vertical Axis Wind Turbines

This paper presents a numerical and experimental analysis of the patent of a device to be used in vertical-axis wind turbines (VAWTs) under extreme wind conditions. The device consists of two hemispheres interconnected by a set of conveniently implemented variable section ducts through which the wind circulates to the blades. Furthermore, the design of the cross-section of the ducts allows the control of the wind speed inside the device. These ducts are intended to work as diffusers or nozzles, depending on the needs of the installation site. Simulations were performed for the case of high-speed external wind, for which the ducts act as diffusers to reduce wind speed and maintain a well-functioning internal turbine. Four different patent designs were analyzed, focusing on turbine performance and generated power. The results indicate that the patent allows the generation of electric power for a greater range of wind speeds than with a normal wind turbine. The results support that this patent may be a good alternative for wind power generation in geographic areas with extreme weather conditions or with maintained or strong gusty wind. Experimental tests were carried out on the movement of the blades using the available model. Finally, the power curve of the model of this wind turbine was obtained.

Disturbance Observer-Based Pitch Control of Wind Turbines for Enhanced Speed Regulation

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Yuan Yuan ◽  
X. Chen ◽  
J. Tang
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Disturbance Observer ◽  
Low Frequency ◽  
Time Varying ◽  
Control Loop ◽  
Wind Speeds ◽  
Speed Regulation ◽  
Guaranteed Stability ◽  
Linearized Model

Time-varying unknown wind disturbances influence significantly the dynamics of wind turbines. In this research, we formulate a disturbance observer (DOB) structure that is added to a proportional-integral-derivative (PID) feedback controller, aiming at asymptotically rejecting disturbances to wind turbines at above-rated wind speeds. Specifically, our objective is to maintain a constant output power and achieve better generator speed regulation when a wind turbine is operated under time-varying and turbulent wind conditions. The fundamental idea of DOB control is to conduct internal model-based observation and cancelation of disturbances directly using an inner feedback control loop. While the outer-loop PID controller provides the basic capability of suppressing disturbance effects with guaranteed stability, the inner-loop disturbance observer is designed to yield further disturbance rejection in the low frequency region. The DOB controller can be built as an on–off loop, that is, independent of the original control loop, which makes it easy to be implemented and validated in existing wind turbines. The proposed algorithm is applied to both linearized and nonlinear National Renewable Energy Laboratory (NREL) offshore 5-MW baseline wind turbine models. In order to deal with the mismatch between the linearized model and the nonlinear turbine, an extra compensator is proposed to enhance the robustness of augmented controller. The application of the augmented DOB pitch controller demonstrates enhanced power and speed regulations in the above-rated region for both linearized and nonlinear plant models.

Design of Controls to Attenuate Loads in the Controls Advanced Research Turbine

2004 ◽  
Vol 126 (4) ◽  
pp. 1083-1091 ◽  
Author(s):  
Alan D. Wright ◽  
Mark J. Balas
Keyword(s):  
Wind Speed ◽  
Wind Turbines ◽  
Control Method ◽  
Maximum Energy ◽  
Drive Train ◽  
Control Input ◽  
Pitch Control ◽  
Additional Control ◽  
Bending Modes ◽  
Turbine Speed

The wind industry seeks to design wind turbines to maximize energy production and increase fatigue life. To achieve this goal, we must design wind turbines to extract maximum energy and reduce component and system loads. This paper applies modern state-space control design methods to a two-bladed teetering-hub upwind machine located at the National Wind Technology Center. The design objective is to regulate turbine speed in region 3 (above rated wind speed) and enhance damping in several low-damped flexible modes of the turbine. The controls approach is based on the Disturbance Accommodating Control method and provides accountability for wind-speed disturbances. First, controls are designed with the single control input rotor collective pitch to stabilize the first drive-train torsion as well as the tower first fore-aft bending modes. Generator torque is then incorporated as an additional control input. This reduces some of the demand placed on the rotor collective pitch control system and enhances first drive train torsion mode damping. Individual blade pitch control is then used to attenuate wind disturbances having spatial variation over the rotor and effectively reduces blade flap deflections caused by wind shear.

scholarly journals Results from a wake-steering experiment at a commercial wind plant: investigating the wind speed dependence of wake-steering performance

2021 ◽  
Vol 6 (6) ◽  
pp. 1427-1453
Author(s):  
Eric Simley ◽  
Paul Fleming ◽  
Nicolas Girard ◽  
Lucas Alloin ◽  
Emma Godefroy ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Direction ◽  
Wind Farm ◽  
Poor Performance ◽  
Power Production ◽  
Wind Rose ◽  
Wind Speeds ◽  
Variability Model

Abstract. Wake steering is a wind farm control strategy in which upstream wind turbines are misaligned with the wind to redirect their wakes away from downstream turbines, thereby increasing the net wind plant power production and reducing fatigue loads generated by wake turbulence. In this paper, we present results from a wake-steering experiment at a commercial wind plant involving two wind turbines spaced 3.7 rotor diameters apart. During the 3-month experiment period, we estimate that wake steering reduced wake losses by 5.6 % for the wind direction sector investigated. After applying a long-term correction based on the site wind rose, the reduction in wake losses increases to 9.3 %. As a function of wind speed, we find large energy improvements near cut-in wind speed, where wake steering can prevent the downstream wind turbine from shutting down. Yet for wind speeds between 6–8 m/s, we observe little change in performance with wake steering. However, wake steering was found to improve energy production significantly for below-rated wind speeds from 8–12 m/s. By measuring the relationship between yaw misalignment and power production using a nacelle lidar, we attribute much of the improvement in wake-steering performance at higher wind speeds to a significant reduction in the power loss of the upstream turbine as wind speed increases. Additionally, we find higher wind direction variability at lower wind speeds, which contributes to poor performance in the 6–8 m/s wind speed bin because of slow yaw controller dynamics. Further, we compare the measured performance of wake steering to predictions using the FLORIS (FLOw Redirection and Induction in Steady State) wind farm control tool coupled with a wind direction variability model. Although the achieved yaw offsets at the upstream wind turbine fall short of the intended yaw offsets, we find that they are predicted well by the wind direction variability model. When incorporating the expected yaw offsets, estimates of the energy improvement from wake steering using FLORIS closely match the experimental results.

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