Comparison of wind turbine LQG controllers using Individual Pitch Control to alleviate fatigue loads
23 Jun 2010-pp 1591-1596
TL;DR: In this article, the design of linear quadratic Gaussian (LQG) controllers for variable-speed horizontal axis wind turbine (WT) is studied. And the main control objectives are to reduce structural dynamic loads and to regulate the power of the WT.
Abstract: This paper focuses on the design of Linear Quadratic Gaussian (LQG) controllers for variable-speed horizontal axis Wind Turbines (WT). These turbines use blade pitch angle and electromagnetic torque control variables to meet specified objectives for Full Load (FL) zone. The main control objectives are to reduce structural dynamic loads and to regulate the power of the WT. The controllers are designed in order to optimize a trade-off between several control objectives. Four different LQG using Individual Pitch Control (IPC) are designed, with Wireless-Sensors (WS) placed at the end of the blades for the last one. Their control model is progressively more complex. The first one takes into account a rigid simple behavior, the second control model considers the first mode of the drive-train flexibility, the third model takes into account the drive-train and tower flexibilities and the fourth that of the blades. Likewise, their optimization criteria consider for each controller a new control objective to alleviate fatigue loads in the drive-train, then, also in the tower and finally also in the blades. The evaluation of the fatigue loads affecting the WT components are based on a Rainflow Counting Algorithm (RFC) and the Miner's rule. The results indicate a significant reduction of fatigue loads especially in the drive-train and the blades when its flexibility is taken into account in the control models.
Citations
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13 Jul 2003
TL;DR: In this article, the authors proposed two modeling procedures for wind speed simulation, which could be implemented on the structure of a wind turbine simulator during studies concerning stand-alone or hybrid wind systems.
Abstract: In this paper we propose two modeling procedures for wind speed simulation. These procedures could be implemented on the structure of a wind turbine simulator during studies concerning stand-alone or hybrid wind systems. The evolution of a horizontal wind speed has been synthesized taking into account two components. The medium- and long-term component is described by a power spectrum associated to a specific site. The turbulence component is assumed to be dependent on the medium- and long-term wind speed evolution. It is considered as a nonstationary process. Two simulation methods for this component, using rational and nonrational filters are proposed. In both procedures, the turbulence model is defined by two parameters, which are either obtained experimentally, or adopted a priori, according to information from the considered site. Numerical results and implementation aspects are also discussed.
217 citations
TL;DR: This paper shows how to model the Coleman transformation in a form that is amenable to IPC analysis and synthesis, and explains why traditional design parameters of gain and phase margin are poor indicators of robust stability and hence motivate the need for a multivariable design approach.
Abstract: As the size of wind turbines increases, the effects of dynamic loading on the turbine structures become increasingly significant. There is therefore a growing demand for turbine control systems to alleviate these unsteady structural loads in addition to maintaining basic requirements such as power and speed regulation. This has motivated the development of blade individual pitch control (IPC) methodologies, many of which employ the Coleman transformation to simplify the controller design process. However, and as is shown in this paper, the Coleman transformation significantly alters the rotational system dynamics when these are referred to the non-rotating frame of reference, introducing tilt–yaw coupling in the process. Unless this transformation is explicitly included in the model employed for IPC design, then the resulting controllers can yield poor performance. Therefore, in this paper, we show how to model the Coleman transformation in a form that is amenable to IPC analysis and synthesis. This enables us to explain why traditional design parameters of gain and phase margin are poor indicators of robust stability and hence motivate the need for a multivariable design approach. The robust multivariable IPC approach advocated in this paper is based upon H∞ loop shaping and has numerous desirable properties, including reliable stability margins, improved tilt–yaw decoupling and simultaneous rejection of disturbance loads over a range of frequencies. The design of a robust multivariable IPC is discussed, and simulation results are presented that demonstrate the efficacy of this controller, in terms of load reduction on both rotating and non-rotating turbine parts. Copyright © 2014 John Wiley & Sons, Ltd.
61 citations
Cites methods from "Comparison of wind turbine LQG cont..."
...Studies such as [22] and [23] designed IPCs based on LTI turbine models that did not employ a coordinate transform....
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...In [22], the dynamics associated with changes in rotor azimuthal position were not included in a two-bladed WTG model that subsequently formed the basis for a LQG-based IPC design....
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10 Jun 2012
TL;DR: The derived TS model shall be used as a basis for the design of fault detection and isolation (FDI) concepts and the small deviations obtained demonstrate the high model quality of the control-oriented TS model.
Abstract: For a horizontal-axis wind turbine (HAWT), a dynamic nonlinear model with four degrees of freedom is derived and transformed into a Takagi-Sugeno (TS) model structure using the sector nonlinearity approach. Thereby, an exact transformation of the nonlinear model is obtained as a weighted combination of linear models. This structure allows for a convenient design of controller and observer structures. The maps of the rotor thrust and torque coefficients can be implemented in the model as look-up tables or, alternatively, as analytical nonlinear functions. Open-loop simulation results of the derived TS model for a reference model turbine are compared to those obtained with the aero-elastic code FAST. The small deviations obtained demonstrate the high model quality of the control-oriented TS model. In future work, the derived TS model shall be used as a basis for the design of fault detection and isolation (FDI) concepts.
52 citations
TL;DR: The comparisons between the proposed strategy and the traditional gain scheduling PI one show the effectiveness and several suggestions are also concluded for industrial wind turbines with MPC implementations.
36 citations
13 Oct 2011
TL;DR: This paper considers a static wind model for a three-bladed, horizontal-axis, pitch-controlled wind turbine and shows that very similar performance can be achieved by using only load measurements, with no knowledge of the wind field or wind turbine model.
Abstract: We consider a static wind model for a three-bladed, horizontal-axis, pitch-controlled wind turbine. When placed in a wind field, the turbine experiences several mechanical loads, which generate power but also create structural fatigue. We address the problem of finding blade pitch profiles for maximizing power production while simultaneously minimizing fatigue loads. In this paper, we show how this problem can be approximately solved using convex optimization. When there is full knowledge of the wind field, numerical simulations show that force and torque RMS variation can be reduced by over 96% compared to any constant pitch profile while sacrificing at most 7% of the maximum attainable output power. Using iterative learning, we show that very similar performance can be achieved by using only load measurements, with no knowledge of the wind field or wind turbine model.
30 citations
Cites background from "Comparison of wind turbine LQG cont..."
...Many studies [1], [2], [3], [4], [5] have been performed which attempt to reduce fatigue loads while also generating sufficient power by dynamically controlling blade pitching....
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References
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TL;DR: In this article, a new equivalent definition of the rainflow cycle counting method is presented, which expresses the rain flow cycle amplitudes in explicit analytical formulae, and attaches to each maximum of the strain function the amplitude of a corresponding cycle or two half cycles, which are evaluated independently from each other.
423 citations
"Comparison of wind turbine LQG cont..." refers methods in this paper
...A cumulative damage law is used to estimate the fatigue damage and hence life time [7], [8], [9]....
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01 Jan 1971
TL;DR: In this article, a cumulative damage procedure is developed to predict the fatigue failure of engineering metals subjected to complicated stress-strain histories, which is used to make life predictions for a wide variety of complicated history tests on 2024-T4 aluminum.
Abstract: : A cumulative damage procedure is developed to predict the fatigue failure of engineering metals subjected to complicated stress-strain histories. Histories with plastic strainings and cycles not completely reversed in stress are considered. The relationship between stress-strain behavior and fatigue life is investigated for unnotched axially loaded specimens for which the stresses and strains can be measured for the duration of all tests. Since either the stress history or the strain history was known before each test was conducted, the other could be estimated and a life prediction made. A general cumulative damage procedure is used to make life predictions for a wide variety of complicated history tests on 2024-T4 aluminum.
418 citations
TL;DR: In this paper, the authors proposed two modeling procedures for wind speed simulation, which could be implemented on the structure of a wind turbine simulator during studies concerning stand-alone or hybrid wind systems.
Abstract: In this paper, the authors propose two modeling procedures for wind speed simulation. These procedures could be implemented on the structure of a wind turbine simulator during studies concerning stand-alone or hybrid wind systems. The evolution of a horizontal wind speed has been synthesized taking into account two components. The medium- and long-term component is described by a power spectrum associated to a specific site. The turbulence component is assumed to be dependent on the medium- and long-term wind speed evolution. It is considered as a nonstationary process. Two simulation methods for this component, using rational and nonrational filters are proposed. In both procedures, the turbulence model is defined by two parameters, which are either obtained experimentally, or adopted a priori, according to information from the considered site. Numerical results and implementation aspects are also discussed.
296 citations
TL;DR: A newly designed integrated wireless monitoring system that supports real-time data acquisition from multiple wireless sensing units that has been fabricated, assembled, and validated in both laboratory tests and in a large-scale field test conducted upon the Geumdang Bridge in Icheon, South Korea.
Abstract: Structural health monitoring (SHM) has become an important research problem which has the potential to monitor and ensure the performance and safety of civil structures. Traditional wire-based SHM systems require significant time and cost for cable installation. With the recent advances in wireless communication technology, wireless SHM systems have emerged as a promising alternative solution for rapid, accurate and low-cost structural monitoring. This paper presents a newly designed integrated wireless monitoring system that supports real-time data acquisition from multiple wireless sensing units. The selected wireless transceiver consumes relatively low power and supports long-distance peer-to-peer communication. In addition to hardware, embedded multithreaded software is also designed as an integral component of the proposed wireless monitoring system. A direct result of the multithreaded software paradigm is a wireless sensing unit capable of simultaneous data collection, data interrogation and wirele...
238 citations
"Comparison of wind turbine LQG cont..." refers methods in this paper
...A wireless structural monitoring system is assembled using a wireless-sensor and is designed by [5] to offer high quality data acquisition, which provides more information for the control system and also for the risk of damage to be reduced or eliminated within the WT....
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13 Jul 2003
TL;DR: In this article, the authors proposed two modeling procedures for wind speed simulation, which could be implemented on the structure of a wind turbine simulator during studies concerning stand-alone or hybrid wind systems.
Abstract: In this paper we propose two modeling procedures for wind speed simulation. These procedures could be implemented on the structure of a wind turbine simulator during studies concerning stand-alone or hybrid wind systems. The evolution of a horizontal wind speed has been synthesized taking into account two components. The medium- and long-term component is described by a power spectrum associated to a specific site. The turbulence component is assumed to be dependent on the medium- and long-term wind speed evolution. It is considered as a nonstationary process. Two simulation methods for this component, using rational and nonrational filters are proposed. In both procedures, the turbulence model is defined by two parameters, which are either obtained experimentally, or adopted a priori, according to information from the considered site. Numerical results and implementation aspects are also discussed.
217 citations
Additional excerpts
...It contains the following components : A one dimensional wind speed which respects the stochastic properties of the Von Karman model [6]....
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