Oscillation analysis of doubly-fed unit considering wind speed variation

Abstract Tower shadow effect and wind shear may cause power oscillation of the unit. In order to study the influence of tower shadow effect and wind shear on the output power of wind turbine, a doubly-fed turbine was taken as an example. Firstly, the influence of tower shadow effect and wind shear was considered to study the periodic power fluctuation characteristics of wind turbines. Then, according to the dynamic model of mechanical transmission mechanism, the influences of the inertia constants of generator, fan and the stiffness coefficient of the shaft system on the transient performance of the wind power generation system were considered respectively. Finally, a single machine infinite bus system model including wind speed model is built on PSCAD/EMTDC platform for simulation. The results show that the tower shadow effect and wind shear component can cause the power fluctuation of the turbine. When the power fluctuation frequency of the turbine is equal to the natural oscillation frequency of the wind turbine shafting, the resonance of the turbine occurs, and the amplitude of oscillation is the largest. Changing the transmission parameters will affect the power fluctuation amplitude and speed response speed of the unit.

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Dynamic Modeling of Wind Turbines Based on Estimated Wind Speed under Turbulent Conditions

Energies ◽

10.3390/en12101907 ◽

2019 ◽

Vol 12 (10) ◽

pp. 1907 ◽

Cited By ~ 5

Author(s):

Ahmed G. Abo-Khalil ◽

Saeed Alyami ◽

Khairy Sayed ◽

Ayman Alhejji

Keyword(s):

Wind Speed ◽

Wind Turbine ◽

Wind Turbines ◽

Wind Shear ◽

Large Scale ◽

Estimation Error ◽

Turbine Rotor ◽

Average Wind Speed ◽

Rotating Speed ◽

Tower Shadow

Large-scale wind turbines with a large blade radius rotates under fluctuating conditions depending on the blade position. The wind speed is maximum in the highest point when the blade in the upward position and minimum in the lowest point when the blade in the downward position. The spatial distribution of wind speed, which is known as the wind shear, leads to periodic fluctuations in the turbine rotor, which causes fluctuations in the generator output voltage and power. In addition, the turbine torque is affected by other factors such as tower shadow and turbine inertia. The space between the blade and tower, the tower diameter, and the blade diameter are very critical design factors that should be considered to reduce the output power fluctuations of a wind turbine generator. To model realistic characteristics while considering the critical factors of a wind turbine system, a wind turbine model is implemented using a squirrel-cage induction motor. Since the wind speed is the most important factor in modeling the aerodynamics of wind turbine, an accurate measurement or estimation is essential to have a valid model. This paper estimates the average wind speed, instead of measuring, from the generator power and rotating speed and models the turbine’s aerodynamics, including tower shadow and wind shear components, without having to measure the wind speed at any height. The proposed algorithm overcomes the errors of measuring wind speed in single or multiple locations by estimating the wind speed with estimation error less than 2%.

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Characteristic Analysis of DFIG Wind Turbine under Blade Mass Imbalance Fault in View of Wind Speed Spatiotemporal Distribution

Energies ◽

10.3390/en12163178 ◽

2019 ◽

Vol 12 (16) ◽

pp. 3178 ◽

Cited By ~ 1

Author(s):

Shuting Wan ◽

Kanru Cheng ◽

Xiaoling Sheng ◽

Xuan Wang

Keyword(s):

Wind Speed ◽

Theoretical Analysis ◽

Wind Shear ◽

Natural World ◽

Spatiotemporal Distribution ◽

Characteristic Analysis ◽

Mass Imbalance ◽

Shadow Effect ◽

Electromagnetic Power ◽

Tower Shadow

The blade mass imbalance fault is one of the common faults of the DFIG (Doubly-Fed Induction Generator) wind turbines (WTs). In this paper, considering the spatiotemporal distribution of natural wind speed and the influence of wind shear and tower shadow effect, the influence of blade mass imbalance faults on the electrical characteristics of DFIG WTs is analyzed. Firstly, the analytical expressions and variation characteristics of electromagnetic torque and electromagnetic power under blade mass imbalance are derived before and after consideration of the spatiotemporal distribution of wind speed. Then simulations on the MATLAB/Simulink platform were done to verify the theoretical analysis results. The theoretical analysis and simulation results show that, considering the spatiotemporal distribution of wind speed and the influence of wind shear and tower shadow effect, the blade mass imbalance fault will cause fluctuation at the frequency of 1P (P = the frequency of rotor rotation), 3P, and 6P on electromagnetic power. Fluctuation at 1P is caused by mass imbalance while fluctuation at 3P and 6P are caused by wind speed spatiotemporal distribution; the amplitude of fluctuation at 1P is proportional to the degree of the imbalance fault. Since the equivalent wind speed has been used in this paper instead of the average wind speed, the data is more suitable for the actual operation of the WT in the natural world and can be applied for fault diagnosis in field WT operation.

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Bumpless Transfer of Parametrized Multivariable Disturbance Observer Based Controller to Reduce Cyclic Loads of Wind Turbine

10.20944/preprints201801.0222.v1 ◽

2018 ◽

Author(s):

Raja Muhammad Imran ◽

Dil Muhammad Akbar Hussain ◽

Bhawani Shanker Chowdhry ◽

Arbab Waleed

Keyword(s):

Wind Turbine ◽

Wind Shear ◽

Disturbance Observer ◽

Smooth Transition ◽

Cyclic Loads ◽

Power Fluctuation ◽

Pitch Control ◽

Full Load ◽

Full Load Operation ◽

Tower Shadow

This paper is concerned with bump-less transfer of parametrized disturbance observer based controller (DOBC) with Individual Pitch Control (IPC) strategy for full load operation of wind turbine. Aerodynamic cyclic loads are reduced by tuning multivariable DOBC with the objective to reduce output power fluctuation, tower oscillation and drive-train torsion. Furthermore tower shadow and wind shear effect are also mitigated using parametrized controller. A scheduling mechanism between two DOBC is developed and tested on Fatigue, Aerodynamics, Structures, and Turbulence ( FAST) code model of National Renewable Energy Laboratory (NREL)’s 5 MW wind turbine. The closed-loop system performance is assessed by comparing the simulation results of proposed controller with a fixed gain and Linear Parameter Varying (LPV) DOBC with Collective Pitch Control (CPC) for full load operation. It is tested with step changing wind to see the behavior of the system under step change with wind shear and tower shadow (cyclic load) effects. Also turbulent wind is applied to see the smooth transition of the controllers. It can be concluded from the results that the proposed parametrized control DOBC with IPC shows smooth transition from one controller to another by interpolation. Moreover fatigue of the gear and tower due to wind shear and tower shadow effects are reduced considerably by the proposed controller as compared to collective pitch control.

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Simulation of Wind Speed for an Large Offshore Wind Turbine

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.971-973.709 ◽

2014 ◽

Vol 971-973 ◽

pp. 709-713

Author(s):

Yong Zhi Xie ◽

An Le Mu

Keyword(s):

Wind Speed ◽

Power Spectrum ◽

Wind Turbine ◽

Wind Shear ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Superposition Method ◽

Computing Power ◽

Special Points ◽

Tower Shadow

According to the wind shear and tower shadow effect, wind speed model was established for large offshore wind turbine .Simulation of the wind speed has been fulfilled by the harmonic superposition method on the 4 special points of the offshore wind turbine, and the split-Radix FFT was introduced to improve the computational efficiency. The consistency of theoretical power spectrum and computing power spectrum of pulsating wind speed verified the rationality and validity of simulation of the wind speed.

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Development of Hardware-in-the-Loop-Simulation Testbed for Pitch Control System Performance Test

Energies ◽

10.3390/en12102031 ◽

2019 ◽

Vol 12 (10) ◽

pp. 2031

Author(s):

Jongmin Cheon ◽

Jinwook Kim ◽

Joohoon Lee ◽

Kichang Lee ◽

Youngkiu Choi

Keyword(s):

Control System ◽

Wind Speed ◽

Wind Turbine ◽

Wind Shear ◽

Performance Test ◽

Control Function ◽

Hardware In The Loop ◽

Rotor Speed ◽

Test Bed ◽

Pitch Control

This paper deals with the development of a wind turbine pitch control system and the construction of a Hardware-in-the-Loop-Simulation (HILS) testbed for the performance test of the pitch control system. When the wind speed exceeds the rated wind speed, the wind turbine pitch controller adjusts the blade pitch angles collectively to ensure that the rotor speed maintains the rated rotor speed. The pitch controller with the individual pitch control function can add individual pitch angles into the collective pitch angles to reduce the mechanical load applied to the blade periodically due to wind shear. Large wind turbines often experience mechanical loads caused by wind shear phenomena. To verify the performance of the pitch control system before applying it to an actual wind turbine, the pitch control system is tested on the HILS testbed, which acts like an actual wind turbine system. The testbed for evaluating the developed pitch control system consists of the pitch control system, a real-time unit for simulating the wind and the operations of the wind turbine, an operational computer with a human–machine interface, a load system for simulating the actual wind load applied to each blade, and a real pitch bearing. Through the several tests based on HILS test bed, how well the pitch controller performed the given roles for each area in the entire wind speed area from cut-in to cut-out wind speed can be shown.

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Time-Domain Modeling of Tower Shadow and Wind Shear in Wind Turbines

ISRN Renewable Energy ◽

10.5402/2011/890582 ◽

2011 ◽

Vol 2011 ◽

pp. 1-11 ◽

Cited By ~ 12

Author(s):

Swagata Das ◽

Neeraj Karnik ◽

Surya Santoso

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Time Domain ◽

Wind Shear ◽

Electrical Power ◽

Rotational Frequency ◽

Domain Modeling ◽

Periodic Fluctuations ◽

Electrical Power Output ◽

Tower Shadow

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 times the blade rotational frequency , where is the number of blades. For three-bladed wind turbines, this inherent characteristic is known as the 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 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.

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