Adaptive Pitch Control of Variable-Speed Wind Turbines

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Kathryn E. Johnson ◽  
Lee Jay Fingersh
Keyword(s):  
Pitch Angle ◽  
Gain Control ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Variable Speed ◽  
Aerodynamic Efficiency ◽  
Energy Capture ◽  
Pitch Control ◽  
Wind Speeds ◽  
Optimal Efficiency

The aerodynamic efficiency of a variable-speed wind turbine operating in Region 2, or below-rated wind speeds, is greatly affected by the identification of accurate parameters for the controller. In particular, the power coefficient (Cp) surface must be well known for optimal efficiency to be achieved with a constant-gain controller. However, adaptive control can overcome the inefficiencies caused by inaccurate knowledge of the Cp surface. Previous work focused on adaptive torque gain control to cause a variable-speed turbine to operate, on average, at the tip-speed ratio λ* for which the maximum Cp occurs. This paper considers the effects of adaptive blade pitch angle control on a turbine’s aerodynamic efficiency. Computer simulations and tests on a field turbine are used to verify the adaptive pitch control scheme. Simulation and field test results demonstrate that the adaptive pitch controller causes the pitch angle to approach its optimal value. Adaptive pitch control can be used to seek the optimal pitch angle for energy capture in Region 2 operation. Additional field operation is required before a statistically significant improvement in energy capture can be demonstrated.

Influence of Transition Modes and Gravity Loads on Rotor Fatigue and Power Control

2002 ◽  
Author(s):  
A. J. Eggers ◽  
P. Moriarty ◽  
K. Chaney ◽  
R. Digumarthi ◽  
W. E. Holley
Keyword(s):  
Fatigue Life ◽  
Pitch Angle ◽  
Closed Loop ◽  
Closed Loop Control ◽  
Loop Control ◽  
Energy Capture ◽  
Pitch Control ◽  
Wind Speeds ◽  
Start Up ◽  
Transition Modes

Two classes of transition modes are examined. The first class involves rotor start-up and shut-down in turbulent winds with rapidly varying mean wind speeds. In the start-up mode, coupling can occur between the mean and cyclic pitch control systems which leads to large peaks in blade flatwise moments. These peaks can substantially increase overall fatigue damage. They can be reduced by controlling blade pitch solely with the closed loop control system. Allowing the rotor to freely rotate at wind speeds below start-up eliminates blade moment peaks in the transition to low speed operation, with the result that closed loop control further increases blade fatigue life. These control alterations reduce power fluctuations but appear to have no significant effect on overall energy capture. Blade pitch control in the shutdown transition mode is restricted solely to mean pitch angle and no control coupling problems are encountered. The second class of transition modes studied is operation from below to above rated wind speed. This transition was previously idealized as an abrupt change from variable to constant rotor speed operation with mean blade pitch angle increased rapidly to hold mean power constant up to rotor shut down. This causes a very sharp peaking of mean moment at rated wind speed which increases blade fatigue damage. This peaking is reduced by smoothing the controlled variation of mean blade pitch angle over a range of wind speeds from below to above rated. As a result, rotor blade fatigue life is substantially increased, and energy capture is somewhat reduced in both open and closed loop operation. Thus there is a trade-off between energy capture and fatigue life which is examined. The comparative effects on blade fatigue life and weight of turbulence induced and 1P gravity loads are examined for large scale rotor blades. The bending strength of each blade in the out-of-plane and in-plane directions at the critical root location was assumed to be the same for full span pitch control requiring a cylindrical cross-section at the root. It is indicated that turbulence induced fatigue damage dominates over that due to gravity for rotor radii up to about 40m and near 2 MW rated power, depending on the number of rotor blades. This open loop result is unaltered in closed loop operation if blade weight is reduced to maintain the same fatigue life. Tradeoffs between rotor blade weight and energy capture in open and closed loop control operation are examined.

scholarly journals Analysis of Influence of Tilt Angle on Variable-Speed Fixed-Pitch Floating Offshore Wind Turbines for Optimizing Power Coefficient Using Experimental and CFD Models

2020 ◽  
Vol 10 (2) ◽  
pp. 201-212
Author(s):  
Wongsakorn Wisatesajja ◽  
Wirachai Roynarin ◽  
Decha Intholo
Keyword(s):  
Wind Turbine ◽  
Tilt Angle ◽  
Offshore Wind ◽  
Power Coefficient ◽  
Variable Speed ◽  
Offshore Wind Turbines ◽  
Pitch Control ◽  
Wind Speeds ◽  
Floating Offshore Wind Turbines ◽  
Fixed Pitch

This study focused on optimization of the power coefficient of floating offshore wind turbines (FOWTs) to maintain their wind power performance in order to overcome problems with the tilt angle resulting from an unstable wind turbine platform, which can reduce the effective area of wind turbine energy extraction. FOWTs with a variable-speed fixed-pitch control strategy were investigated using an experimental model in a wind tunnel and a CFD simulation model for analysis and comparison, using wind speeds of 2–5.5 m/s and tilt angles of 3.5–6.1°. The results showed that average rotational speed differences of 16.4% and optimal power coefficients of 0.35–0.36 could be maintained at tip speed ratios of 7.7–9.6 during wind speeds of 3–5 m/s with tilt angles of 3.9–5.8°. The results of this study provide insights into a new concept of power coefficient optimization using variable tilt angle for small to medium fixed pitch FOWTs, to reduce the cost of pitch control systems.

Application of Variable Blade Pitch Control on Improving the Performance of Vertical Axis Wind Turbine

2012 ◽  
Vol 229-231 ◽  
pp. 2339-2342
Author(s):  
J.C. Cheng ◽  
S.J Su ◽  
J.J Miau
Keyword(s):  
Wind Turbine ◽  
Vertical Axis ◽  
Aerodynamic Characteristics ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Energy Capture ◽  
Pitch Control ◽  
Tip Speed Ratio ◽  
Torque Coefficient ◽  
Variable Pitch Control

A three blades vertical axis wind turbine simulation is performed to study the unsteady aerodynamic characteristics with blade pitch control. Several fixed and variable blade pitch models under different tip speed ratio are adopted to improve performance of the wind turbine. Results show that an appropriate pitch control model can effectively decrease the range of negative torque regime to reduce the vibration of the wind turbine. Besides, the average torque coefficient as well as the energy capture efficiency can be also improved, especially for the lower tip speed ratio. The overall efficiency of the wind turbines in power generation will be enhanced. For the cases under the tip speed ratio between 1 and 3, the efficiency can be enhanced 243% and 486% for fixed and variable pitch control models respectively as comparing with non-pitch control cases.

Unintended Stalling of the USW 56-100 During Optimum Pitch Control Operation

1994 ◽  
Vol 116 (3) ◽  
pp. 153-157
Author(s):  
G. McNerney
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Pitch Angle ◽  
Blade Angle ◽  
Control Logic ◽  
Control Operation ◽  
Energy Capture ◽  
Pitch Control ◽  
Power Regulation ◽  
The U.S

The U.S. Windpower 56-100 is a three-bladed, free yaw wind turbine, using full span blade pitch control for power regulation. It is theoretically possible to increase the energy capture of the 56-100 by adjusting the blade angle to the optimum pitch angle on a continuing basis at below rated speeds. This concept was field tested on the 56-100, but it was found that the optimum pitch control logic opens a pathway for the 56-100 to fall into stall operation when the winds are above the rated wind speed. The 56-100 then operates as a stall-regulated wind turbine with an overall reduction of energy capture and an increase in system loads.

scholarly journals Numerical simulation and experimental study of blade pitch effect on Darrieus straight-bladed wind turbine with high solidity: A case study under realistic conditions

2020 ◽  
Author(s):  
Milad Babadi Soultanzadeh ◽  
Alireza Moradi
Keyword(s):  
Wind Turbine ◽  
Numerical Method ◽  
Pitch Angle ◽  
Numerical Results ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Regulation System ◽  
Lower Velocity ◽  
Realistic Condition ◽  
Tip Speed Ratio

Abstract Numerical and experimental studies were performed to examined the influence of pitch angle on the aerodynamic performance of a small Darrieus straight blade vertical axis wind turbine with high solidity and pitch regulation system under a realistic condition. By comparing experimental and numerical results, numerical results were validated. The power coefficient was measured and calculated at different tip speed ratios and for two pitch angles 0 and 5. The results revealed that 5 degrees increase in the pitch angle led to 25% elevation in the maximum value of the power coefficient (performance coefficient). Also, the numerical results showed higher accuracy at lower tip speed ratios for both pitch angles. After numerical method validation, numerical method employed to calculate the coefficient of performance and coefficient of torque function of Azimuth position as well as the flow field in the rotor affected zone and lateral distance. According to the numerical results, vorticity generation increased by the rise in the pitch angle at a constant tip speed ratio; the maximum performance coefficient occurred at a lower tip speed ratio with elevation in the pitch angle; finally, the increment in the pitch angle led to lower velocity profile in lateral distances of the rotor.

Simulating the Dynamic and Steady State Response of a Rotor Resistive Controlled 1.5 MW Variable Speed Wind Turbine

2010 ◽  
Author(s):  
Jared B. Garrison ◽  
Michael E. Webber
Keyword(s):  
Steady State ◽  
Wind Speed ◽  
Dynamic Response ◽  
Wind Turbine ◽  
Power Output ◽  
Pitch Angle ◽  
Maximum Power ◽  
Variable Speed ◽  
Wind Speeds ◽  
Variable Speed Wind Turbine

Currently, wind and solar technologies only generate 0.77% and 0.014% of the U.S. electricity consumption, respectively [1]. Though only a small portion of total U.S. electricity production, both sources have seen significant growth recently. For instance, Texas has more than quadrupled its installed wind capacity over the period from 2005–2009 with new installations totaling over 9400 MW [2, 3]. These two resources are globally available and have the potential to generate massive amounts of electricity. As the amount of installed wind turbines continues to grow, gaining better knowledge of their operation and their dynamic response to changing wind conditions is important to ensure their smooth integration and safe operation. The goal of this research is to analyze the dynamic and steady state operations of a 1.5 MW variable speed wind turbine that uses an external rotor resistive control mechanism. The addition of the external generator rotor resistance allows for adjustment of the generator slip and employs a feedback controller that maintains constant power output at all air velocities between the rated wind speed and cut-out wind speed. Using the electronic programming language PSCAD/EMTDC the model simulates the dynamic response to changing wind conditions, as well as the performance under all wind conditions. The first task of the model was to determine which blade pitch angle produces a maximum power output of 1.5 MW. A sweep was used where the simulation runs over the entire range of wind speeds for a selected pitch angle to find which speed resulted in maximum power output. This sweep was used for numerous blade pitch angles until the combination of wind speed and pitch angle at 14.4 m/s and −0.663°, respectively, resulted in a maximum power of 1.5 MW. The second task was to evaluate the model’s dynamic response to changes in wind conditions as well as steady state operation over all wind speeds. The dynamic response to an increase or decrease in wind speed is important to the safety and life expectancy of a wind turbine because unwanted spikes and dips can occur that increase stresses in the wind turbine and possibly lead to failure. In order to minimize these transient effects, multiple controllers were implemented in order to test each ones’ dynamic response to increasing and decreasing changes in wind velocity. These simulations modeled the characteristics of a variable-speed wind turbine with constant power rotor resistive control. First, through calibrating the model the design specifications of blade pitch and wind speed which yield the peak desired output of 1.5 MW were determined. Then, using the method of controlling the external rotor resistance, the simulation was able to maintain the 1.5 MW power output for all wind speeds between the rated and cutout speeds. Also, by using multiple controllers, the dynamic response of the control scheme was improved by reducing the magnitude of the initial response and convergence time that results from changes in wind speed. Finally, by allowing the simulation to converge at each wind speed, the steady state operation, including generator power output and resistive thermal losses, was characterized for all wind speeds.

Aerodynamic Design and Wind Tunnel Tests of Small-scale Horizontal-axis Wind Turbines for Low Tip Speed Ratio Applications

2022 ◽  
pp. 1-34
Author(s):  
Ojing Siram ◽  
Neha Kesharwani ◽  
Niranjan Sahoo ◽  
Ujjwal K. Saha
Keyword(s):  
Wind Tunnel ◽  
Wind Turbines ◽  
Pitch Angle ◽  
Horizontal Axis ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Small Scale ◽  
Wind Tunnel Tests ◽  
Tip Speed Ratio ◽  
Horizontal Axis Wind Turbines

Abstract In recent times, the application of small-scale horizontal axis wind turbines (SHAWTs) has drawn interest in certain areas where the energy demand is minimal. These turbines, operating mostly at low Reynolds number (Re) and low tip speed ratio (λ) applications, can be used as stand-alone systems. The present study aims at the design, development, and testing of a series of SHAWT models. On the basis of aerodynamic characteristics, four SHAWT models viz., M1, M2, M3, and M4 composed of E216, SG6043, NACA63415, and NACA0012 airfoils, respectively have been developed. Initially, the rotors are designed through blade element momentum theory (BEMT), and their power coefficient have been evaluated. Thence, the developed rotors are tested in a low-speed wind tunnel to find their rotational frequency, power and power coefficient at design and off-design conditions. From BEMT analysis, M1 shows a maximum power coefficient (Cpmax) of 0.37 at λ = 2.5. The subsequent wind tunnel tests on M1, M2, M3, and M4 at 9 m/s show the Cpmax values to be 0.34, 0.30, 0.28, and 0.156, respectively. Thus, from the experiments, the M1 rotor is found to be favourable than the other three rotors, and its Cpmax value is found to be about 92% of BEMT prediction. Further, the effect of pitch angle (θp) on Cp of the model rotors is also examined, where M1 is found to produce a satisfactory performance within ±5° from the design pitch angle (θp, design).

Characteristic Analysis of Three-Bladed Darrieus Wind Turbine Based on the Multiple Streamtube Model

2014 ◽  
Vol 651-653 ◽  
pp. 663-667 ◽  
Author(s):  
Jing Ru Chen ◽  
Zhen Zhou Zhao ◽  
Tao Li
Keyword(s):  
Wind Turbine ◽  
Pitch Angle ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Characteristic Analysis ◽  
Negative Power ◽  
Tip Speed Ratio ◽  
Maximum Value ◽  
Blade Pitch Angle ◽  
Ratio Range

The paper analyzes the effect of airfoil thickness, camber and blade pitch angle on the performance of the three-bladed Darrieus wind turbines. The research results show that the increase of airfoil thickness, camber and pitch angle of blade, can improve power coefficient when the wind turbine tip speed ratio between zero and four. The increase of thickness and camber of the airfoil leads to running tip speed ratio range of wind turbine get narrowed, and reduces the power coefficient when wind turbine runs in high tip speed ratio range. When the pitch angle of blade is 1˚, power coefficient reaches the maximum value. Negative pitch angle has a bad impact on power coefficient and even creates negative power coefficients.

scholarly journals Robust Active Disturbance Rejection Control Approach to Maximize Energy Capture in Variable-Speed Wind Turbines

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Horacio Coral-Enriquez ◽  
John Cortés-Romero ◽  
Germán A. Ramos
Keyword(s):  
Wind Turbine ◽  
Control Strategy ◽  
Disturbance Rejection ◽  
Optimal Trajectory ◽  
Control Technique ◽  
Power Coefficient ◽  
Variable Speed ◽  
Control Approach ◽  
Energy Capture ◽  
Active Disturbance Rejection

This paper proposes an alternative robust observer-based linear control technique to maximize energy capture in a 4.8 MW horizontal-axis variable-speed wind turbine. The proposed strategy uses a generalized proportional integral (GPI) observer to reconstruct the aerodynamic torque in order to obtain a generator speed optimal trajectory. Then, a robust GPI observer-based controller supported by an active disturbance rejection (ADR) approach allows asymptotic tracking of the generator speed optimal trajectory. The proposed methodology controls the power coefficient, via the generator angular speed, towards an optimum point at which power coefficient is maximum. Several simulations (including an actuator fault) are performed on a 4.8 MW wind turbine benchmark model in order to validate the proposed control strategy and to compare it to a classical controller. Simulation and validation results show that the proposed control strategy is effective in terms of power capture and robustness.

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