• Journal of international Conference on Electrical Machines and Systems
• /
• v.2 no.1
• /
• pp.31-39
• /
• 2013

This paper presents small signal stability analysis of a doubly fed induction generator (DFIG) based wind farm including series dynamic braking resistor (SDBR) connected at the stator side. A detailed mathematical model of wind turbine, DFIG machine and converters and SDBR is presented in this paper to derive the complete dynamic equations of the studied system. Small signal stability of this system is carried out by modal and sensitivity analysis, participation factors and eigenvalue analysis. Finally, this paper presents an analysis of the dynamic behavior of DFIG based wind farm under voltage dip condition with and without SDBR.

• Proceedings of the KIEE Conference
• /
• 2001.10a
• /
• pp.301-304
• /
• 2001

Wind power generation system is one of the most useful energy resource using natural environment. One of the biggest problem we encountered is toot the wind speed is fluctuating sharply according to the weather conditions rather than it is stable. In this paper we do the equivalent modeling the mechanical energy of wind power turbine according to wind speed into the synchronous generator. We analyse the equivalent modeling output part of rectifier into DC/DC converter input part theoretically. We analyse a battery charging characteristics for power storage enabling the supply of stable power to the load. We design a system and do the modeling of it analytically so that it supplies a stable power to the load by constructing a DC-AC inverter point. Also we make a small size model usable in actual wind power generation system of 30kw and make an experiment and confirm its validity.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2006.11a
• /
• pp.80-90
• /
• 2006

The influence of waves on the dynamic properties of bending moments at the root of blades of tidal stream vertical axis rotors is reported. Blade theory for wind turbine is combined with linear wave theory and used to analyse this influence. Experiments were carried out to validate the simulation and the comparison shows the usefulness of the theory in predicting the bending moments. The mathematical model is then used to study the importance of waves for the fatigue design of the blade-hub connection.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.2
• /
• pp.487-495
• /
• 2015

This paper proposes a new robust decentralized power oscillation dampers (POD) design of doubly-fed induction generator (DFIG) wind turbine for damping of low frequency electromechanical oscillations in an interconnected power system. The POD structure is based on the practical $2^{nd}$-order lead/lag compensator with single input. Without exact mathematical model, the inverse output multiplicative perturbation is applied to represent system uncertainties such as system parameters variation, various loading conditions etc. The parameters optimization of decentralized PODs is carried out so that the stabilizing performance and robust stability margin against system uncertainties are guaranteed. The improved firefly algorithm is applied to tune the optimal POD parameters automatically. Simulation study in two-area four-machine interconnected system shows that the proposed robust POD is much superior to the conventional POD in terms of stabilizing effect and robustness.

• Journal of Electrical Engineering and Technology
• /
• v.12 no.1
• /
• pp.145-150
• /
• 2017

This paper present a unified method of steady state performance analysis and limits characteristics of an autonomous three-phase self-excited induction generator (SEIG) driven by a wind turbine under different types of loads and speeds. The proposed method is based on a new mathematical function to solve for the real and imaginary components of the complex equation of the mathematical model. Performances limits, regulation and characteristics of different configurations will be thoroughly examined and compared. The proposed system will be modeled and simulated and the performance limits characteristics will be compared with variable speed and variable capacity.

• Smart Structures and Systems
• /
• v.22 no.2
• /
• pp.139-150
• /
• 2018

A variable electromotive-force generator (VEG), which is a modified generator with an adjustable overlap between the rotor and the stator, is proposed to expand the operational range of a regular generator through a simple and robust active control strategy. It has a broad range of applications in hybrid vehicles, wind turbines, water turbines, and similar technologies. A mathematical model of the VEG is developed, and a novel prototype is designed and fabricated. The performance of the VEG with an active control system, which adjusts the overlap ratio based on the desired output power at different rotor speeds for a specific application, is theoretically and experimentally studied. The results show that reducing the overlap between the rotor and the stator of the generator results in reduced torque loss of the generator and an increased rotational speed of the generator rotor. A VEG can improve the fuel efficiency of hybrid vehicles; it can also expand operational ranges of wind turbines and water turbines and harness more power.

• Journal of Advanced Research in Ocean Engineering
• /
• v.1 no.1
• /
• pp.55-62
• /
• 2015

Floating structure such as tension leg platform, semi-submersible and spar are widely used in field of oil exploration and renewable energy system. All of these structures have the base cylinder support structure which have effective rule in overall dynamic of response. So the accurate and reliable modeling is needed for optimum design and understanding the physical background of these systems. The aim of this article is an analytical discussion on stochastic modeling of floating cylinder based support structure but an applicable one. Due to this a mathematical mass-damper-spring system of a floating cylinder of HAWAII WTG offshore wind as an applicable and innovative system is adopted to model a coupled degrees using random vibration in analytical way. A fully develop spectrum is adopted to solve the stochastic spectrum analytically by a proper approximation. Some acceptable assumption is adopted. The simplified but analytical and innovative hydrodynamic analysis of this study not only will help researcher to concentrate more physically on hydrodynamic analysis of floating structures but also can be useful for any quick, simplified and closed form analysis of a complicated problem in offshore engineering.

• Steel and Composite Structures
• /
• v.50 no.1
• /
• pp.25-43
• /
• 2024

In this article, a mathematical model is developed to predict the dynamic behavior of bio-inspired composite beam with helicoidal orientation scheme under variable axial load using a unified higher order shear deformation beam theory. The geometrical kinematic relations of displacements are portrayed with higher parabolic shear deformation beam theory. Constitutive equation of composite beam is proposed based on plane stress problem. The variable axial load is distributed through the axial direction by constant, linear, and parabolic functions. The equations of motion and associated boundary conditions are derived in detail by Hamilton's principle. Using the differential quadrature method (DQM), the governing equations, which are integro-differential equations are discretized in spatial direction, then they are transformed into linear eigenvalue problems. The proposed model is verified with previous works available in literatures. Parametric analyses are developed to present the influence of axial load type, orthotropic ratio, slenderness ratio, lamination scheme, and boundary conditions on the natural frequencies of composite beam structures. The present enhanced model can be used especially in designing spacecrafts, naval, automotive, helicopter, the wind turbine, musical instruments, and civil structures subjected to the variable axial loads.

• New & Renewable Energy
• /
• v.9 no.3
• /
• pp.5-13
• /
• 2013

In the previous research, dynamic results have been analyzed in the time and frequency regions. Time and frequency region can be transformed by the Fourier transform. This transform is very useful about analyzing system behaviors. However, because of coupling, it cannot give clear results in the real system including lots of defects. In this paper, we introduced the analysis based on quefrency region to represent physical means clearly from complicated results. We simulated the drive train system which has defects, and compared between frequency and quefrency region to show its excellence. To do this process, We established mathematical model. The equation of motion was derived by the Lagrange equation and constraint equations. The constraint equation included relationships about gear mesh, flexibility of shaft. About numerical analysis, the Newmark beta method was used to get results. And FFT (Fast Fourier Transform) which converts results from time domain to frequency, qufrequency was used.

• Geomechanics and Engineering
• /
• v.10 no.5
• /
• pp.577-598
• /
• 2016

This paper presents a numerical study of pile force distribution in a pile group foundation subjected to vertical load and large moment. The physical modeling of a pile foundation for a wind turbine is analyzed using 3D finite element software, PLAXIS 3D. The soil profile consists of several clay layers, which are modeled as Mohr-Coulomb material in an undrained condition. The piles in the pile group foundation are modeled as special elements called embedded pile elements. To model the problem of a pile group foundation, a small gap is created between the pile cap and underlying soil. The pile cap is modeled as a rigid plate element connected to each pile by a hinge. As a result, applied vertical load and large moment are transferred only to piles without any load sharing to underlying soil. Results of the study focus on pile load distribution for the square shape of a pile group foundation. Mathematical expression is proposed to describe pile force distribution for the cases of vertical load and large moment and purely vertical load.