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Operation Scheme for a Wind Farm to Mitigate Output Power Variation
Lee, Sung-Eun,Won, Dong-Jun,Chung, Il-Yop The Korean Institute of Electrical Engineers 2012 Journal of Electrical Engineering & Technology Vol.7 No.6
Because of the nature of wind, the output power of wind turbines fluctuates according to wind speed variation. Therefore, many countries have set up wind-turbine interconnection standards usually named as Grid-Code to regulate the output power of wind farms to improve power system reliability and power quality. This paper proposes three operation modes of wind farms such as maximum power point tracking (MPPT) mode, single wind turbine control mode and wind farm control mode to control the output power of wind turbines as well as overall wind farms. This paper also proposes an operation scheme of wind farm to alleviate power fluctuation of wind farm by choosing the appropriate control mode and coordinating multiple wind turbines in consideration of grid conditions. The performance of the proposed scheme is verified via simulation studies in PSCAD/EMTDC with doubly-fed induction generator (DFIG) based wind turbine models.
Calculation of the Post-arc Current in a Supersonic Nozzle by using the k-e Turbulence Model
Ki-Dong Song,Kyong-yop PARK,Byeong-Yoon Lee 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.3
This paper describes the eect of the k- turbulence parameter on the arcing phenomena in a supersonic nozzle. Simulations of the arcing phenomena were carried out in the following order; a steady-state 1000-A dc arc and a transient arc generated by the current with falling rates of di/dt = 27.0 and 13.5 A/s before current-zero and by the hot-gas ow after current-zero. The post-arc current was calculated during the hot-gas ow analysis after current-zero. The turbulence parameter in the k- turbulence model was varied from 1.44 to 1.57 to investigate its eects on the post-arc current. The thermal recovery characteristics were estimated from the calculated post-arc current. The optimum value of the turbulence parameter could be determined by comparing the calculated thermal recovery characteristics with the test results presented by a research group of General Electric Company.
김동훈(Dong-hun Kim),한송엽(Song-Yop Hahn),박관수(Gwan-Soo Park),이기식(Ki-Sik Lee) 한국자기학회 1994 韓國磁氣學會誌 Vol.4 No.1
Magnetic fluid is ferromagnetic material in liquid state, so the surface configuration of magnetic fluid affects the magnetic field, and vice versa. To analyze the devices with magnetic fluid, the magnetic field equations and hydrodynamic equation should be solved simultaneously. This paper presents the numerical algorithm to obtain the surface configuration of fluid under the influence of gravity, pressure and magnetic field without conventional simplified assumption[1-6]. The algorithm consists of nonlinear finite element method and ferro-hydrodynamics, such as Poisson equations and Bernoulli equations, respectively. The simulated configurations of fluid are compared with experimental results, and the influence of the amount of fluid and pole piece shape on the seal capacities are analyzed.