A study of tower shadow effect on fixed-speed wind turbines
16 Dec 2008-pp 1-5
TL;DR: In this paper, the impact of tower shadow effect on the power output of a fixed-speed wind farm was investigated. But the authors focused on the effect of the tower shadow on power fluctuation and did not consider the effects of the synchronisation of turbine blades around the tower.
Abstract: This paper studies the impact of tower shadow effect on the power output of a fixed-speed wind farm. A data acquisition unit was placed at a wind farm in Northern Ireland which consists of ten fixed-speed wind turbines. The recording equipment logged the wind farmpsilas electrical data, which was time stamped using the global positioning network. Video footage of the wind farm was recorded and from it the blade angle of each turbine was determined with respect to time. Using the blade angle data and the wind farmpsilas power output, studies where performed to ascertain the extent of tower shadow effect on power fluctuation. This paper presents evidence that suggests that tower shadow effect has a significant impact on power fluctuation and that this effect is increased due to the synchronising of turbine blades around the tower region.
Citations
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TL;DR: A detailed time-domain upwind fixed speed wind turbine model which includes the turbine's aerodynamic, mechanical, electrical, as well as tower shadow and wind shear components is developed.
Abstract: Tower shadow and wind shear contribute to periodic fluctuations in electrical power output of a wind turbine generator. The frequency of the periodic fluctuations is 𝑛 times the blade rotational frequency 𝑝, where 𝑛 is the number of blades. For three-bladed wind turbines, this inherent characteristic is known as the 3𝑝 effect. In a weak-power system, it results in voltage fluctuation or flicker at the point of common coupling of the wind turbine to the grid. The phenomenon is important to model so as to evaluate the flicker magnitude at the design level. Hence, the paper aims to develop a detailed time-domain upwind fixed speed wind turbine model which includes the turbine's aerodynamic, mechanical, electrical, as well as tower shadow and wind shear components. The model allows users to input factors such as terrain, tower height, and tower diameter to calculate the 3𝑝 oscillations. The model can be expanded to suit studies involving variable speed wind turbines. Six case studies demonstrate how the model can be used for studying wind turbine interconnection and voltage flicker analysis. Results indicate that the model performs as expected.
35 citations
Cites background from "A study of tower shadow effect on f..."
...However, in a wind farm, if many wind turbine blades synchronize, the magnitude of voltage flicker would be severe [2]....
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...In a system with significant wind generation wherein wind farms supply majority of the power to the grid, synchronization of the blades in the wind farm contribute to larger power and voltage fluctuations [2]....
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...For a three-bladed wind turbine, each of the blades experience minimum wind in one complete rotation and hence tower shadow contributes to the 3p effect [1, 2]....
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...The 3p fluctuations are due to two effects known as wind shear and tower shadow [1, 2]....
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TL;DR: In this paper, an adaptive neuro-fuzzy controller for static VAR compensator, used in power networks integrated with WECS, is presented to address the torque oscillation problem.
Abstract: Wind shear and tower shadow produce a periodic pulse reduction in mechanical torque captured from wind energy resulting in wind energy conversion system (WECS) active power oscillations. In this study, an adaptive neuro-fuzzy controller for static VAR compensator, used in power networks integrated with WECS, is presented to address the torque oscillation problem. The proposed controller consists of a radial basis function neural network representing a third-order auto-regressive and moving average system model and performing the prediction, and a main controller with adaptive neuro-fuzzy inference system providing the damping signal. A modified two-area four-machine power network with WECS integration is applied to validate the proposed implementation, compared with conventional lead/lag compensation. Time-domain simulations prove that the proposed controller can provide a damping signal to improve the active power oscillation and system dynamic stability, influenced by torque oscillations under WECSs synchronised operating condition.
21 citations
TL;DR: The downwind wind turbines are considered here as their tower shadow effects are more significant compared to the upwind counterpart as their wind speed deficit due to this nonideal effect is significant.
Abstract: This paper presents the modeling and characterization of the tower shadow effects using a wind turbine emulator in a laboratory environment. In particular, the downwind wind turbines are considered here as their tower shadow effects are more significant compared to the upwind counterpart. Simulation and experimental results have shown that the wind speed deficit due to this nonideal effect is significant. In addition, the tower shadow effects occur typically two to three times per revolution, depending on the number of blades. The modeling of the tower shadow profiles for tubular and four-leg tower configurations is presented. Typically, these towers are used in small wind turbine applications. The tower shadow profiles are emulated experimentally using a wind turbine emulator with its characteristics being explained. The limitations of emulating the tower shadow effects using a wind turbine emulator are demonstrated through the frequency response test performed in this study. In this study, the wind turbine emulator is connected to an isolated grid which is formed by three single-phase inverters. Finally, this paper concludes with a sensitivity analysis of the power oscillations for different widths and magnitudes of the tower shadow profile.
20 citations
25 Jul 2010
TL;DR: In this article, a flicker mitigation scheme for the doubly-fed induction generator (DFIG) during variable wind conditions was developed based on the distribution line X/R ratio and the active power deviation from the average active power during variable Wind conditions.
Abstract: This paper presents a flicker mitigation scheme for the doubly-fed induction generator (DFIG) during variable wind conditions. The flicker mitigation strategy was developed based on the distribution line X/R ratio and the active power deviation from the average active power during variable wind conditions. Flicker emission was analyzed using a flicker meter based on the IEC standards. Both short-term and long-term flicker severities were analyzed during the time period of study. The flicker mitigation strategy was evaluated under different system conditions such as X/R ratio, distribution line length, short-circuit capacity (SCC), and wind variability. It is shown that the proposed control scheme mitigates flicker severity with different X/R ratios, distribution line lengths and different wind conditions. However, the proposed strategy is less effective with relatively low SCCs at the point of grid connection, due to large fluctuations of the voltage at the point of grid connection.
19 citations
Cites background from "A study of tower shadow effect on f..."
...The major wind generation based power quality issues are 3p/2p power oscillations due to the tower shadow effect [2-3] (especially with fixed-speed wind turbines), voltage fluctuations/flicker due to variable wind conditions [4,7], and harmonics due to power electronics components [8-9] in wind generation systems (doubly-fed induction generator (DFIG) and direct-drive synchronous generator (DDSG) wind generators)....
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22 Dec 2014
TL;DR: In this article, the authors presented a new method of modeling and combined simulating of aerodynamic, mechanical, control and electrical systems in two simulation software platforms: GH Bladed and MATLAB/Simulink.
Abstract: Wind power has reached a significant penetration level in the power system worldwide. Grid codes are proposed to safe guard power system with large scale wind power integration. To verify grid code compliance, wind turbine integration characteristics should be verified based on test and simulation results. Therefore, accurate simulation model need to be developed. Since wind turbine model are generally developed to fulfill specific purpose, there are three categories as follow: electromechanical transient model for the study of wind power integration in power system; electromagnetic transient model for the purpose of analyzing wind turbine electrical transient characteristics; and model used to vindicate wind turbine design and control strategy concerning load calculation, mechanical dynamic analyzing etc. However, neither of these models aims at analyzing the interaction between mechanical components and electrical components. This paper introduces a new method of modeling and combined simulating of aerodynamic, mechanical, control and electrical systems in two simulation software platforms. The wide used software tools GH Bladed and MATLAB/Simulink were utilized. According to the method, mechanical, aerodynamic and control (pitch control and torque control) model is specified in GH Bladed, while electrical model (concerning grid, generator and converter) was implemented in MATLAB. In the process of simulation, the two separate models were synchronized via a communication interface which was based on TCP/IP protocol. A 2.5MW wind turbine was modeled and simulated using the presented combined simulation method. Wind turbine simulation results during grid fault were verified with low voltage ride through test data to certify the accuracy of the combined simulation model. Based on the simulation results, mechanical dynamic on blades and drive train during grid fault was presented and the simulation method's further application in analyzing the interact between wind turbine and grid system was proposed.
13 citations
References
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TL;DR: In this article, a theoretical analysis and explanation of synchronization phenomena in wind parks with asynchronous generators is presented, and a theoretical model of the synchronization phenomenon is presented for wind power systems.
Abstract: In this paper, a theoretical analysis and explanation of synchronization phenomena in wind parks with asynchronous generators is presented.
40 citations
"A study of tower shadow effect on f..." refers background in this paper
...Several theories have been researched into why turbines synchronise in this way; however, it is beyond the scope of this paper [2, 3]....
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...However, studies to date have largely centred on the theoretical impact of the synchronisation of turbines [2, 3]....
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01 Jul 2007
TL;DR: In this paper, the impact of tower shadow on the output power from a wind farm was analyzed using data recorded on site, and the effect on the system of the removal of a large fixed-speed wind farm is investigated.
Abstract: The impact of power fluctuations arising from fixed-speed wind turbines on the magnitude and frequency of inter-area oscillations has been investigated. The authors introduced data acquisition equipment to record the power flow on the interconnector between the Northern Ireland and Republic of Ireland systems. Through monitoring the interconnector oscillation using a fast Fourier transform, it was possible to determine the magnitude and frequency of the inter-area oscillation between the two systems. The impact of tower shadow on the output power from a wind farm was analysed using data recorded on site. A case study investigates the effect on the system of the removal of a large fixed-speed wind farm. Conclusions are drawn on the impact that conventional generation and the output from fixed-speed wind farms have on the stability of the Irish power system.
15 citations
"A study of tower shadow effect on f..." refers background in this paper
...So depending on blade rotational speed the generator will experience a periodic dip in mechanical torque typically in the frequency order of a couple of Hz [1]....
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TL;DR: In this paper, the synchronization phenomena of wind turbines in a wind farm were discussed and the authors obtained a differential equation that describes the phenomena with output power, voltage, and slip fluctuations of a wind turbine, examining dependence of the phenomena on the related parameters.
Abstract: This paper discusses the synchronization phenomena of wind turbines in a wind farm. The phenomena illustrate the situation where a blade revolution of a wind turbine is pulled into phase with that of the other turbines in a wind farm. If blades of many turbines simultaneously pass in front of their towers, output power fluctuations of the turbines due to tower shadow effects also become synchronized. This causes voltage fluctuation to increase and may give rise to voltage flicker problems.
The purpose of this paper is to examine the phenomena theoretically. Obtaining a differential equation that describes the phenomena with output power, voltage, and slip fluctuations of a wind turbine, we examine dependence of the phenomena on the related parameters. We also prove the validity of the equation through simulation analyses. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(1): 9–18, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20201
8 citations
TL;DR: In this paper, the synchronization phenomena of wind turbines in a wind farm were discussed theoretically and the authors obtained a differential equation that describes the phenomena with output power, voltage and slip fluctuations of a wind turbine, examined dependence of the phenomena on the related parameters.
Abstract: This paper discusses the synchronization phenomena of wind turbines in a wind farm. The phenomena denote the situation that a blade revolution of a wind turbine is pulled into phase with that of the other turbines in a wind farm. If blades of many turbines simultaneously pass in front of their towers, output power fluctuations of the turbines due to tower shadow effects also become synchronized. This causes voltage fluctuation to increase and may give rise to voltage flicker problems. The purpose of this paper is to examine the phenomena theoretically. Obtaining a differential equation that describes the phenomena with output power, voltage and slip fluctuations of a wind turbine, we examine dependence of the phenomena on the related parameters. We also prove the validity of the equation through simulation analyses.
8 citations
"A study of tower shadow effect on f..." refers background in this paper
...The periodic dip for a single generator had previously been assumed to be cancelled out by the relative random blade positions of other turbines in a wind farm [2]....
[...]
...Several theories have been researched into why turbines synchronise in this way; however, it is beyond the scope of this paper [2, 3]....
[...]
...However, studies to date have largely centred on the theoretical impact of the synchronisation of turbines [2, 3]....
[...]