| 1. |
- Stotsky, Alexander, 1960
(författare)
-
A new frequency domain system identification method
- 2011
-
Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 2405-8963. - 9783902661937 ; 18:PART 1, s. 3186-3191
-
Konferensbidrag (refereegranskat)abstract
- A new frequency domain system identification method based on a multi-frequency input signal is proposed. Frequency contents of the oscillating signal are estimated using a modified Kaczmarz algorithm proposed in this paper. Lyapunov stability analysis is performed for this new Kaczmarz algorithm and transient bounds for estimation error are established. Moreover, a new method for estimation of the variance of the measurement noise in Kaczmarz algorithms is also described. A comparison of a transient performance of modified Kaczmarz algorithm and a recursive least-squares algorithm is presented. The results are applied to a frequency domain identification of a DC motor.
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| 2. |
- Stotsky, Alexander, 1960
(författare)
-
A new frequency domain system identification method
- 2012
-
Ingår i: Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering. - : SAGE Publications. - 2041-3041 .- 0959-6518. ; 226:1, s. 111-125
-
Tidskriftsartikel (refereegranskat)abstract
- A new frequency domain system identification method based on a multi-frequencyinput signal is proposed. Frequency contents of the oscillating signal are estimated using amodified Kaczmarz algorithm proposed in this paper. Lyapunov stability analysis is performedfor this new Kaczmarz algorithm and transient bounds for estimation error are established.Moreover, a new method for estimation of the variance of the measurement noise inKaczmarz algorithms is also described. A comparison of a transient performance of modifiedKaczmarz algorithm and a recursive least-squares algorithm is presented. The results areapplied to a frequency domain identification of a DC motor.
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| 3. |
- Stotsky, Alexander, 1960
(författare)
-
Accuracy Improvement in Least-Squares Estimation with Harmonic Regressor: New Preconditioning and Correction Methods
- 2015
-
Ingår i: Proceedings of the IEEE Conference on Decision and Control. - 2576-2370 .- 0743-1546. - 9781479978861 ; 54rd IEEE Conference on Decision and Control,CDC 2015, s. 4035-4040
-
Konferensbidrag (refereegranskat)abstract
- Numerical aspects of least squares estimation have not been sufficiently studied in the literature. In particular, information matrix has a large condition number for systems with harmonic regressor in the initial steps of RLS (Recursive Least Squares) estimation. A large condition number indicates invertibility problems and necessitates the development of new algorithms with improved accuracy of estimation. Symmetric and positive definite information matrix is presented in a block diagonal form in this paper using transformation, which involves the Schur complement. Block diagonal sub-matrices have significantly smaller condition numbers and therefore can be easily inverted, forming a preconditioner for a large scale system. High order algorithms with controllable accuracy are used for solving least squares estimation problem. The second part of the paper is devoted to the performance improvement in classical RLS algorithm, which represents a feedforward estimation procedure with error accumulation. Two correction feedback terms originated from combined high order algorithms are introduced for performance improvement in classical RLS algorithms. Simulation results show significant performance improvement of modified algorithm compared to classical RLS algorithm in the presence of roundoff errors.
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| 4. |
- Stotsky, Alexander, 1960, et al.
(författare)
-
An overview of proactive wind turbine control
- 2013
-
Ingår i: Energy Science and Engineering. - : Wiley. - 2050-0505. ; 1:1, s. 2-11
-
Tidskriftsartikel (refereegranskat)abstract
- Recent achievements in the proactive turbine control, based on the upwind speed measurements, are described in a unified framework (as an extension of the tutorial [1]), that in turn represents a systematic view of the control activity carried out within the Swedish Wind Power Technology Center (SWPTC). A new turbine control problem statement with constraints on blade loads is reviewed. This problem statement allows the design of a new class of simultaneous speed and pitch control strategies based on the preview measurements and look-ahead calculations. A generation of a piecewise constant desired pitch angle profile which is calculated using the turbine load prediction is reviewed in this article as one of the most promising approaches. This in turn allows the reduction of the pitch actuation and the design of the collective pitch control strategy with the maximum possible actuation rate. Two turbine speed control strategies based on one-mass and two-mass models of the drivetrain are also described in this article. The strategies are compared to the existing drivetrain controller. Moreover, postprocessing technique that can be used for estimation of the turbine parameters with improved performance is also discussed. Postprocessing-based estimation of the turbine inertia moment is given as an example. All the results are illustrated by simulations with a wind speed record from the Hönö turbine, located outside of Gothenburg, Sweden. Recent achievements in the proactive turbine control, based on the upwind speed measurements are described in a unified framework that in turn represents a systematic view of the control activity carried out within the Swedish Wind Power Technology Center (SWPTC).
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| 5. |
- Stotsky, Alexander, 1960
(författare)
-
Automotive Engines
- 2009
-
Bok (övrigt vetenskapligt/konstnärligt)abstract
- Increasing demands on the output performance, exhaust emissions, and fuel consumption necessitate the development of a new generation of automotive engine functionality. This monograph is written by a long year developmental automotive engineer and offers a wide coverage of automotive engine control and estimation problems and its solutions. It addresses idle speed control, cylinder flow estimation, engine torque and friction estimation, engine misfire and CAM profile switching diagnostics, as well as engine knock detection. The book provides a wide and well structured collection of tools and new techniques useful for automotive engine control and estimation problems such as input estimation, composite adaptation, threshold detection adaptation, real-time algorithms, as well as the very important statistical techniques. It demonstrates the statistical detection of engine problems such as misfire or knock events and how it can be used to build a new generation of robust engine functionality. This book will be useful for practising automotive engineers, black belts working in the automotive industry as well as for lecturers and students since it provides a wide coverage of engine control and estimation problems, detailed and well structured descriptions of useful techniques in automotive applications and future trends and challenges in engine functionality.
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| 6. |
- Stotsky, Alexander, 1960
(författare)
-
Blade root moment sensor failure detection based on multibeam LIDAR for fault-tolerant individual pitch control of wind turbines
- 2014
-
Ingår i: Energy Science and Engineering. - : Wiley. - 2050-0505. ; 2:3, s. 107-115
-
Tidskriftsartikel (refereegranskat)abstract
- Detection of blade root moment sensor failures is an important problem for fault-tolerant individual pitch control, which plays a key role in reduction of uneven blade loads of large wind turbines. A new method for detection of blade root moment sensor failures which is based on variations induced by a vertical wind shear is described in this paper. The detection is associated with monitoring of statistical properties of the difference between amplitudes of the first harmonic of the blade load, which is calculated in two different ways. The first method is based on processing of the load sensor signal, which contains a number of harmonics. The first harmonic is recovered via least squares estimation of the blade load signal with harmonic regressor and strictly diagonally dominant (SDD) information matrix. The second method is a model-based method of estimation of the first harmonic, which relies on the blade load model and upwind speed measurements provided by multibeam Light Detection and Ranging (LIDAR). This is a new application for future LIDAR-enabled wind turbine technologies. Moreover, adaptation of the load model in a uniform wind field is proposed. This adaptation improves accuracy of the load estimation and hence the performance of the blade load sensor failure detection method.
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| 7. |
- Stotsky, Alexander, 1960
(författare)
-
Combined high-order algorithms in robust least-squares estimation with harmonic regressor and strictly diagonally dominant information matrix
- 2015
-
Ingår i: Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering. - : SAGE Publications. - 2041-3041 .- 0959-6518. ; 229:2, s. 184-190
-
Tidskriftsartikel (refereegranskat)abstract
- This article describes new high-order algorithms in the least-squares problem with harmonic regressor and strictly diagonally dominant information matrix. Estimation accuracy and the number of steps to achieve this accuracy are controllable in these algorithms. Simplified forms of the high-order matrix inversion algorithms and the high-order algorithms of direct calculation of the parameter vector are found. The algorithms are presented as recursive procedures driven by estimation errors multiplied by the gain matrices, which can be seen as preconditioners. A simple and recursive (with respect to order) algorithm for update of the gain matrix, which is associated with Neumann series, is found. It is shown that the limiting form of the algorithm (algorithm of infinite order) provides perfect estimation. A new form of the gain matrix is also a basis for unification method of high-order algorithms. New combined and fast convergent high-order algorithms of recursive matrix inversion and algorithms of direct calculation of the parameter vector are presented. The stability of algorithms is proved and explicit transient bound on estimation error is calculated. New algorithms are simple, fast and robust with respect to round-off error accumulation.
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| 8. |
- Stotsky, Alexander, 1960, et al.
(författare)
-
Control of wind turbines: A tutorial on proactive perspectives
- 2013
-
Ingår i: American Control Conference. - : IEEE. - 0743-1619. - 9781479901777 ; , s. 3429-3436
-
Konferensbidrag (refereegranskat)abstract
- Recent achievements in the proactive turbine control1, based on the upwind speed measurements are described in a unified tutorial fashion (as an extension of the tutorial [1]), that in turn represents a systematic view of the control activity carried out within the Swedish Wind Power Technology Center (SWPTC). A new turbine control problem statement with constraints on blade loads is reviewed. This problem statement allows the design of a new class of simultaneous speed and pitch control strategies based on the preview measurements and look-ahead calculations. A generation of a piecewise constant desired pitch angle profile which is calculated using the turbine load prediction is reviewed in this paper as one of the most promising approaches. This in turn allows the reduction of the pitch actuation and the design of the collective pitch control strategy with the maximum possible actuation rate.
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| 9. |
- Stotsky, Alexander, 1960
(författare)
-
Convergence Rate Improvement of Richardson and Newton-Schulz Iterations
- 2020
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Fast convergent, accurate, computationally efficient, parallelizable, and robust matrix inversion and parameter estimation algorithms are required in many time-critical and accuracy-critical applications such as system identification, signal and image processing, network and big data analysis, machine learning and in many others. This paper introduces new composite power series expansion with optionally chosen rates (which can be calculated simultaneously on parallel units with different computational capacities) for further convergence rate improvement of high order Newton-Schulz iteration. New expansion was integrated into the Richardson iteration and resulted in significant convergence rate improvement. The improvement is quantified via explicit transient models for estimation errors and by simulations. In addition, the recursive and computationally efficient version of the combination of Richardson iteration and Newton-Schulz iteration with composite expansion is developed for simultaneous calculations. Moreover, unified factorization is developed in this paper in the form of tool-kit for power series expansion, which results in a new family of computationally efficient Newton-Schulz algorithms.
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| 10. |
- Stotsky, Alexander, 1960, et al.
(författare)
-
Data-driven estimation of the inertia moment of wind turbines: A new ice-detection algorithm
- 2013
-
Ingår i: Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering. - : SAGE Publications. - 2041-3041 .- 0959-6518. ; 227:6, s. 552-555
-
Tidskriftsartikel (refereegranskat)abstract
- Turbine blades accumulate ice under certain atmospheric conditions, such as low temperature and high humidity. This implies additional loads that might damage the turbine. A reliable ice-detection algorithm is required to shut down the turbine and prevent damages. A simple sensorless technique is proposed in this article for detection of both icing and ice shedding events. The technique is based on the estimation of the turbine inertia moment using generator speed measurements, turbine model and robust and fast convergent data-driven algorithms. Estimated inertia moment can be used for both ice detection and adaptation of the parameters of the control system. Implementation of this technique allows a stable turbine operation during hazardous ice conditions via adjustment of the control system parameters or turbine shut down in the extreme icing conditions.
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| 11. |
- Stotsky, Alexander, 1960
(författare)
-
Efficient Iterative Solvers in the Least Squares Method
- 2020
-
Ingår i: Ifac Papersonline. - : Elsevier BV. - 2405-8963. ; 53:2, s. 883-888
-
Tidskriftsartikel (refereegranskat)abstract
- Fast convergent, accurate, computationally efficient, parallelizable, and robust matrix inversion and parameter estimation algorithms are required in many time-critical and accuracy-critical applications such as system identification, signal and image processing, network and big data analysis, machine learning and in many others. This paper introduces new composite power series expansion with optionally chosen rates (which can be calculated simultaneously on parallel units with different computational capacities) for further convergence rate improvement of high order Newton-Schulz iteration. New expansion was integrated into the Richardson iteration and resulted in significant convergence rate improvement. The improvement is quantified via explicit transient models for estimation errors and by simulations. In addition, the recursive and computationally efficient version of the combination of Richardson iteration and Newton-Schulz iteration with composite expansion is developed for simultaneous calculations. Moreover, unified factorization is developed in this paper in the form of tool-kit for power series expansion, which results in a new family of computationally efficient Newton-Schulz algorithms. Copyright (C) 2020 The Authors.
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| 12. |
- Stotsky, Alexander, 1960
(författare)
-
Frequency determination in control applications: excitation-based approach
- 2012
-
Ingår i: Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering. - : SAGE Publications. - 2041-3041 .- 0959-6518. ; 226:8, s. 1142-1148
-
Tidskriftsartikel (refereegranskat)abstract
- New algorithms for estimation of the frequencies of oscillating waveform signals are described. A model of the signals ispresented in the form of a linear difference equation with unknown coefficients, which define the frequencies and amplitudes.Coefficients are estimated utilizing the property of the persistence of excitation of oscillating signals.Exponentially damped and oscillating signals are described in a unified framework. A property of excitation is proved foran exponentially damped signal that contains a single frequency via diagonal dominance of an information matrix. Twoapplications of this frequency estimation technique are considered. The first one is filtering of the wind speed signal inwind turbine control applications, and the second one is the frequency estimation of exponentially damped signals motivatedby the engine knock detection applications.
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| 13. |
- Stotsky, Alexander, 1960
(författare)
-
Frequency determination in control applications: Excitation based approach
- 2012
-
Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 2405-8963. - 9783902823038 ; 7:PART 1, s. 45-50
-
Konferensbidrag (refereegranskat)abstract
- New algorithms for estimation of the frequencies of oscillating waveform signals are described. Model of the signals is presented in the form of linear difference equation with unknown coefficients, which define the frequencies and amplitudes. Coefficients are estimated utilizing the property of the persistence of excitation of oscillating signals. Exponentially damped and oscillating signals are described in a unified framework. A property of excitation is proved for exponentially damped signal that contains a single frequency via diagonal dominance of an information matrix. Two applications of this frequency estimation technique are considered. The first one is filtering of the wind speed signal in wind turbine control applications, and the second one is the frequency estimation of exponentially damped signal motivated by the engine knock detection applications.
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| 14. |
- Stotsky, Alexander, 1960
(författare)
-
Frequency Regulation in Smart Microgrids Based on Load Estimation
- 2018
-
Ingår i: Journal of Control, Automation and Electrical Systems. - : Springer Science and Business Media LLC. - 2195-3880 .- 2195-3899. ; 29:4, s. 525-533
-
Tidskriftsartikel (refereegranskat)abstract
- The desired frequency is maintained in Smart Microgrid (SMG) when the generated power matches the grid load. Variability of wind power and fluctuations of the load are the main obstacles for performance improvement of frequency regulation in SMG. Active Power Control (APC) services provided by wind power generators is one of the main sources for performance improvement in frequency regulation. New coordinated APC architecture, which involves simultaneous speed and pitch control actions delivers desired power to the grid despite significant variations of the wind power. A tool-kit with discrete-time input estimation algorithms, which estimate input quantity using output measurements is presented. Unmeasurable load fluctuations are estimated with input estimation method using measurements of grid frequency deviation. Desired power for APC is driven by estimated and a priori known loads. This observer-based control method reduces the risk of overshoots and oscillations in frequency regulation loop compared to PID controllers driven directly by the frequency deviation. The stability of the closed loop frequency control system is proved, and simulation results show that observer-based control architecture provides significant improvement of the frequency regulation in SMG.
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| 15. |
- Stotsky, Alexander, 1960
(författare)
-
Grid Frequency Estimation Using Multiple Model with Harmonic Regressor: Robustness Enhancement with Stepwise Splitting Method
- 2017
-
Ingår i: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963. ; 50:1, s. 12817-12822
-
Konferensbidrag (refereegranskat)abstract
- Reduction of inertia in electricity networks due to high penetration level of renewable energy sources will require wind turbines to participate in frequency regulation via Active Power Control. The performance of frequency regulation and protection system depends strongly on the performance of network frequency estimation. Fast frequency variations and uncertainties associated with unknown harmonics and measurement noise in the network signals are the main obstacles to performance improvement of frequency estimation with classical zero crossing method, which is widely used in industry. The same uncertainties introduce challenges in model based frequency estimation. These challenges are addressed in this paper within the framework of multiple model with harmonic regressor. Additional challenges associated with computational complexity of matrix inversion algorithms and accuracy of inversion of ill-conditioned matrices in the multiple model are also discussed in the paper. New high order algorithms with reduced computational complexity are presented. Instability mechanism is discovered in Newton-Schulz and Neumann matrix inversion techniques in finite precision implementation environment. A new stepwise splitting method is proposed for elimination of instability and for performance improvement of matrix inversion algorithms in the multiple model. All the results are confirmed by simulations.
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| 16. |
- Stotsky, Alexander, 1960
(författare)
-
Harmonic regressor: Robust solution to least-squares problem
- 2013
-
Ingår i: Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering. - : SAGE Publications. - 2041-3041 .- 0959-6518. ; 227:8, s. 662-668
-
Tidskriftsartikel (refereegranskat)abstract
- A new robust and computationally efficient solution to least-squares problem in the presence of round-off errors is proposed. The properties of a harmonic regressor are utilized for design of new combined algorithms of direct calculation of the parameter vector. In addition, an explicit transient bound for estimation error is derived for classical recursive least-squares algorithm using the Lyapunov function method. Different initialization techniques of the gain matrix are proposed as an extension of the recursive least-squares algorithm. All the results are illustrated by simulations.
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| 17. |
- Stotsky, Alexander, 1960
(författare)
-
High order algorithms in robust least-squares estimation with SDD information matrix: Redesign, simplification and unification
- 2015
-
Ingår i: Proceedings of the IEEE Conference on Decision and Control. - 2576-2370 .- 0743-1546. ; , s. 271-276
-
Konferensbidrag (refereegranskat)abstract
- This paper describes new high order algorithms in the least-squares problem with harmonic regressor and SDD (Strictly Diagonally Dominant) information matrix. Estimation accuracy and the number of steps to achieve this accuracy are controllable in these algorithms. Simplified forms of the high order matrix inversion algorithms and the high order algorithms of direct calculation of the parameter vector are found. The algorithms are presented as recursive procedures driven by estimation errors multiplied by the gain matrices, which can be seen as preconditioners. A simple and recursive (with respect to order) algorithm for update of the gain matrix, which is associated with Neumann series is found. It is shown that the limiting form of the algorithm (algorithm of infinite order) provides perfect estimation. A new form of the gain matrix is also a basis for unification method of high order algorithms. New combined and fast convergent high order algorithms of recursive matrix inversion and algorithms of direct calculation of the parameter vector are presented. The stability of algorithms is proved and explicit transient bound on estimation error is calculated. New algorithms are simple, fast and robust with respect to round-off error accumulation.
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| 18. |
- Stotsky, Alexander, 1960, et al.
(författare)
-
Individual pitch control of wind turbines: Model-based approach
- 2013
-
Ingår i: Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering. - : SAGE Publications. - 2041-3041 .- 0959-6518. ; 227:7, s. 602-609
-
Tidskriftsartikel (refereegranskat)abstract
- Significant fore-and-aft tower vibrations of large wind turbines due to wind shear can be reduced using individual pitch control, in which the pitch angle of each blade is adjusted individually. A short survey of the existing individual pitch control strategies is presented, and a new architecture with preview measurements of the wind speeds at different heights is proposed in this article for the turbine tilt moment reduction. The approach includes look-ahead calculations of the desired blade loads and pitch angles as well as preprocessing algorithms for calculation of the derivative of the desired pitch angle. Wind speed measurement records, performed at two different heights with Risoe P2546 cup anemometer, are directly used in the turbine simulations. It is shown that the variations of tilt moment can be essentially reduced using the approach described in this article.
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| 19. |
- Stotsky, Alexander, 1960
(författare)
-
Kaczmarz Projection Algorithms with Rank Two Gain Update
- 2024
-
Ingår i: Journal of Signal Processing Systems. - 1939-8018. ; 96:4-5, s. 327-332
-
Tidskriftsartikel (refereegranskat)abstract
- New Kaczmarz algorithms with rank two gain update, extended orthogonality property and forgetting mechanism which includes both exponential and instantaneous forgetting (implemented via a proper choice of the forgetting factor and the window size) are introduced and systematically associated in this paper with well-known Kaczmarz algorithms with rank one update. The parameter convergence was proved using Lyapunov method and convergence of the inverse of the information matrix can be used for further performance improvement. The performance of new algorithms is examined in the problem of estimation of the grid events in the presence of significant harmonic emissions.
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| 20. |
- Stotsky, Alexander, 1960, et al.
(författare)
-
Model-based control of wind turbines: look-ahead approach
- 2012
-
Ingår i: Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering. - : SAGE Publications. - 2041-3041 .- 0959-6518. ; 226:8, s. 1029-1038
-
Tidskriftsartikel (refereegranskat)abstract
- A new composite turbine control architecture that consists of feedforward and feedback parts based on the upwind speed measurements and wind speed measurements at the turbine site, respectively, is described. The algorithm starts with preprocessing of a low-rate sampled upwind speed via the spline interpolation method. A run-ahead model driven by the signals from a preprocessing block models the turbine response and produces the feedforward part of turbine controller. The turbine control system is driven by both the feedforward part that comes from the run-ahead model and feedback part based on the wind speed measured at the turbine site. It is proved that the controller is stable despite the difference between the time-shifted preview measurements (expected wind speed) and the actual wind speed measured at the turbine site. Existing industrial proportional-integral-derivative turbine controllers can easily be upgraded with the preview part of the control architecture described in this article. Improved blade load regulation via the blade pitch angle control guarantees a hard upper bound on the flapwise bending moment. The results are confirmed by simulation with a wind speed record from the Hono turbine outside Gothenburg, Sweden.
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| 21. |
- Stotsky, Alexander, 1960, et al.
(författare)
-
Model based control of wind turbines: Look-ahead approach
- 2012
-
Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 2405-8963. - 9783902823038 ; 7:PART 1, s. 639-646
-
Konferensbidrag (refereegranskat)abstract
- A new composite turbine control architecture that consists of feedforward and feedback parts based on the upwind speed measurements and wind speed measurements at the turbine site, respectively, is described. The algorithm starts with preprocessing of a low rate sampled upwind speed via spline interpolation method. A run-ahead model driven by the signals from a preprocessing block models the turbine response and produces the feedforward part of turbine controller. The turbine control system is driven by both feedforward part which comes from the run-ahead model, and feedback part based on the wind speed measured at the turbine site. It is proved that the controller is stable despite the difference between the time shifted preview measurements (expected wind speed) and actual wind speed measured at the turbine site. Existing industrial PI/PID turbine controllers can easily be upgraded with the preview part of the control architecture described in this paper. Improved blade load regulation via the blade pitch angle control guarantees a hard upper bound on the flapwise bending moment. The results are confirmed by simulation with a wind speed record from the Hönö turbine outside Gothenburg, Sweden.
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| 22. |
- Stotsky, Alexander, 1960
(författare)
-
Modified Flipped Classroom Model in Chalmers Professional Education
- 2017
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper is the final report for the project inthe course ’Blended Learning and Digital Media in HigherEducation’ given by Elisabeth Saalman and Thommy Eriksson.This paper proposes new implementation-ready concept ofvideo education in the wind energy area for Chalmers Professional Education. Modified Flipped Classroom Model with video feedback is proposed in this paper as a new pedagogical concept. The model allows video education without skilled Instructor in the classroom and includes a number of components:1) video lecture in wind energy, 2) quizzes, 3) discussions and 4)video summary of the discussions and 5) video feedback from skilled Instructor.Video Lecture ’Lesson on Wind Turbine Control’ was developedwithin this project, recorded in Camtasia and supplied with the ’Guide’ and ’Slides’.
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| 23. |
- Stotsky, Alexander, 1960
(författare)
-
Modified SOLO Taxonomy Model for Constructive Alignment in Automatic Control & Signal Processing Education
- 2017
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Controls is the engineering field that deals withmodeling, regulation and performance assessment of dynamicsystems so that they behave according to the desired specifications.Signal processing is the area, which develops methodsfor processing of sensory data in different areas.Achievements in applied mathematics, new sensors and actuator technologies, developments of new IT tools and software create new opportunities in control and signal processing engineering.This in turn implies new challenges and developments in control and signal processing education.New modified SOLO (Structure of the Observed LearningOutcome) Taxonomy model is developed for automatic controland signal processing education. New model provides a simple, reliable and robust concept, which is well associated with the method of constructive alignment for five levels of understanding.The model is applied for constructive alignment of basiccourse in automatic control and to mini-lesson in digital signal processing.
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| 24. |
- Stotsky, Alexander, 1960
(författare)
-
Nonlinear speed and yaw control for wind turbine powered vessels
- 2016
-
Ingår i: Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering. - 2041-3041 .- 0959-6518. ; 230:3, s. 255-265
-
Tidskriftsartikel (refereegranskat)abstract
- The application of conventional wind turbines on board a vessel creates a number of new challenges for turbine control systems. Thrust force is used in marine applications as an additional control variable for propulsion of the vessel.Variability of the wind speed and wind direction, together with the yaw rate and range constraints, impose strong requirements on the turbine control system. A new projection algorithm that projects the turbine thrust force on the heading direction of vessel is proposed in this paper for controlling propulsion. Variations in the wind direction and wind speed are counteracted via turbine yaw angle, making the turbine thrust force always aligned with the heading direction of the vessel. The conventional Kv2 speed controller is modified for varying yaw offset and a combined algorithm for simultaneous control of the turbine speed and thrust force is proposed. Stability of the Kw^2 speed controller for varying yaw offset is proved via the Lyapunov method. The controller also takes into account the constraints on the yaw rate and minimizes the turbine gyroscopic effects via a proper choice of the virtual upper bound of the input voltage of the yaw motor. All of the results are illustrated by simulations using measurement data acquired from the Hönö turbine.
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| 25. |
- Stotsky, Alexander, 1960, et al.
(författare)
-
Proactive control of wind turbine with blade load constraints
- 2012
-
Ingår i: Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering. - : SAGE Publications. - 2041-3041 .- 0959-6518. ; 226:7, s. 985-993
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes an easy-to-implement, proactive control strategy for wind turbines, incorporating constraints onblade loads. The control strategy is aimed for rejecting wind gusts and is based on upwind speed measurements and anew statistical wind gust detection mechanism. The control action comprises simultaneous driveline and collective pitchcontrol with constraints on flapwise bending moment. The controller is evaluated by simulation on a transient betweentwo steady-state operational modes of the wind turbine. A new driveline backstepping-based controller with integralaction for compensation of steady-state errors is also proposed and verified by simulations.
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| 26. |
- Stotsky, Alexander, 1960
(författare)
-
Recursive trigonometric interpolation algorithms
- 2010
-
Ingår i: Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering. - 2041-3041 .- 0959-6518. ; 224:1, s. 65-77
-
Tidskriftsartikel (refereegranskat)abstract
- Two new recursive algorithms for the calculation of the coefficients of thetrigonometric polynomial that is fitted to measured data in the least-squares sense in awindow of a sufficiently large size that is moving in time are proposed. Both algorithms use thestrictly diagonally dominant property of the information matrix for a sufficiently large windowsize. The first one is based on a recursive inversion of the information matrix and the secondone uses a priori estimate of the coefficients of the polynomial obtained from the Kaczmarzprojection method. The algorithms are computationally suitable for selection of the order of atrigonometric polynomial in each step of a moving window in real-time applications. Theresults are verified by simulations.
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| 27. |
- Stotsky, Alexander, 1960
(författare)
-
Recursive versus nonrecursive Richardson algorithms: systematic overview, unified frameworks and application to electric grid power quality monitoring
- 2022
-
Ingår i: Automatika. - : Informa UK Limited. - 0005-1144 .- 1848-3380. ; 63:2, s. 328-337
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Tidskriftsartikel (refereegranskat)abstract
- Sufficiently accurate, fast and computationally efficient solution of the system of linear equations is required in many estimation problems. Richardson iteration is one of the main solvers for linear equations, which provides optimization possibilities for time critical and accuracy critical applications. Convergence rate improvement and reduction of the computational complexity of the Richardson iteration are the most important problems in the area. The introduction of Newton-Schulz iterations is the efficient way for convergence rate improvement and the paper starts with systematic overview of the high-order Newton-Schulz matrix inversion algorithms. In addition, the unified framework for recursive computationally efficient convergence accelerators and error models for a number of combinations of Richardson and Newton-Schulz iterations is developed. A new nonrecursive parameter estimation concept is introduced and compared in this paper with recursive estimation. Recursive and nonrecursive Richardson algorithms together with the standard LU decomposition method were applied to the electric grid power quality monitoring problem. The algorithms were tested for the detection of the sag and swell signatures in the voltage and current signals on real data in three-phase power system. Nonrecursive Richardson algorithms which save close to half of the computational time compared to LU decomposition method were recommended for power quality monitoring applications.
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| 28. |
- Stotsky, Alexander, 1960
(författare)
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Robust least-squares estimation with harmonic regressor: High order algorithms
- 2013
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Ingår i: Proceedings of the IEEE Conference on Decision and Control. - 2576-2370 .- 0743-1546. - 9781467357173 ; , s. 6516-6521
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Konferensbidrag (refereegranskat)abstract
- A new robust and computationally efficient solution to least-squares problem in the presence of round-off errors is proposed. The properties of a harmonic regressor are utilized for design of new combined algorithms of direct calculation of the parameter vector. In addition, an explicit transient bound for estimation error is derived for classical recursive least-squares (RLS) algorithm using Lyapunov function method. Different initialization techniques of the gain matrix are proposed as an extension of RLS algorithm. All the results are illustrated by simulations.
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| 29. |
- Stotsky, Alexander, 1960, et al.
(författare)
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Robust Proactive Control of Wind Turbines with Reduced Blade Pitch Actuation
- 2013
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Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - 2405-8963. - 9783902823250 ; , s. 695-700
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Konferensbidrag (refereegranskat)abstract
- A new simultaneous speed and pitch control of wind turbines with the previewmeasurements and look-ahead calculations is considered. The desired piecewise constant pitchangle profile which is calculated using turbine load prediction, allows the reduction of pitchactuation that in turn, increases the lifetime of actuator. The robust collective pitch controlarchitecture with the maximum possible actuation rate is proposed.Moreover, a new postprocessing technique that provides the high quality estimate of the turbineinertia moment is also described. The results are confirmed by simulation with a wind speedrecord from the Hönö turbine located outside Gothenburg, Sweden.
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| 30. |
- Stotsky, Alexander, 1960
(författare)
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Simultaneous Frequency and Amplitude Estimation for Grid Quality Monitoring : New Partitioning with Memory Based Newton-Schulz Corrections
- 2022
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Ingår i: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963 .- 2405-8963. ; 55:9, s. 42-47
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Konferensbidrag (refereegranskat)abstract
- High penetration level of renewable energy sources and introduction of controllable loads will result in significant harmonic emissions and sag and swell events in the future electricity networks. Development of the methods for high performance simultaneous estimation of the frequency and amplitude events is required for stable operation of the future electricity networks since zero crossing frequency detection method (which is widely used nowadays in industry) is not accurate enough and does not allow estimation of the amplitude events. The multiple model method which is suitable for simultaneous estimation of the frequency and amplitude is extended in this paper with introduction of a new decomposition technique based on stepwise partitioning, which allows simultaneous construction and accurate and computationally efficient inversion of the information matrix. Recursive calculations of the inverse introduce error accumulation and a new general high order memory based Newton-Schulz iteration is proposed in this paper for correction and reduction of the accumulated error. Moreover, parallel Richardson iterations which are based on partitioning method are proposed in this paper for reduction of the computational complexity. The methods are especially efficient for approximation of the signals with large number of harmonics. The approaches were tested for simultaneous estimation of the frequency and sag and swell signatures in the one-phase synchronized voltage waveform measured at the wall outlet. Simulation results show that the multiple model method provides more accurate frequency estimation in comparison to zero crossing method. In addition, the cascade multiple model method which is based on the multi-windowing technique (where the components of the signals are separated via a proper choice of the window sizes) is introduced in this paper for estimation of the significantly separated frequencies of the electrical signals. The approach was tested in the problem of frequency estimation using the measurement record from the electric vehicle with on-board charger connected to the supply voltage in the laboratory.
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| 31. |
- Stotsky, Alexander, 1960
(författare)
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Towards accurate estimation of fast varying frequency in future electricity networks: The transition from model-free methods to model-based approach
- 2016
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Ingår i: Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering. - : SAGE Publications. - 2041-3041 .- 0959-6518. ; 230:10, s. 1164-1175
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Tidskriftsartikel (refereegranskat)abstract
- Accurate estimation of fast varying fundamental frequency in the presence of harmonics and noise will be required for effective frequency regulation in future electricity networks with high penetration level of renewable energy sources. Two new algorithms for network frequency tracking are proposed. The first algorithm represents a robust modification of classical zero crossing method, which is widely used in industry. The second algorithm is a multiple model algorithm based on the systems with harmonic regressor. Algorithm allows complete reconstruction of the frequency content of the signal, using information about the upper bound of the number of harmonics only. Moreover, new family of high-order algorithms together with new stepwise splitting method are proposed for parameter calculation in systems with harmonic regressor for the accuracy improvement. Statistical methods are introduced for comparison of two new algorithms to classical zero crossing algorithm. The modified algorithm provides significant improvement compared to the classical algorithm, and the algorithm with harmonic regressor provides further improvement of the statistical performance indexes with respect to the modified algorithm.
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| 32. |
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| 33. |
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| 34. |
- Stotsky, Alexander, 1960
(författare)
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Wind turbine model validation: Fusion of simulation and measurement data
- 2014
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Ingår i: Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering. - : SAGE Publications. - 2041-3041 .- 0959-6518. ; 228:9, s. 734-737
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Tidskriftsartikel (refereegranskat)abstract
- A new turbine model validation technique that is based on adaptation of look-up tables is described in this article. Simulation results from the VIDYN turbine simulation program and measurements from Big Glenn wind turbine, located outside Gothenburg, Sweden, are used as an input to this new model validation technique. The models of the flapwise bending moment and power coefficient are validated for Big Glenn turbine. Measurement data are acquired during normal turbine operation. Verification results show good agreement between model outputs and measured data. The method allows prediction in a wide range of turbine operating variables, using only few measured points.
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| 35. |
- Stotsky, Alexander, 1960
(författare)
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Wind turbine model validation: Fusion of simulation and measurement data
- 2014
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Ingår i: IFAC Proceedings Volumes (IFAC-PapersOnline). - : Elsevier BV. - 2405-8963 .- 1474-6670. - 9783902823625 ; 19, s. 3629-3632
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Konferensbidrag (refereegranskat)abstract
- A new turbine model validation technique that is based on adaptation of look-up tables is described this paper. Simulation results from the VIDYN turbine simulation program and measurements from Big Glenn wind turbine, located outside Gothenburg, Sweden are used as an input to this new model validation technique. The models of the flapwise bending moment and power coefficient are validated for Big Glenn turbine. Measurement data are acquired during normal turbine operation. Verification results show good agreement between model outputs and measured data. The method allows prediction in a wide range of turbine operating variables, using only few measured points.
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