• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 1995년도 추계 학술대회논문집
• /
• pp.90-103
• /
• 1995

최근 전산 유체 역학은 Navier-Stokes 방정식을 보다 복잡한 유동장 형상에 대해 풀 수 있을 만큼 발달해 왔으나 아직도 유동장 형상이 복잡할 때는 많은 애로를 느끼고 있다. 특히 격자 구성 문제에 있어서 많은 시간과 노력을 기울이고 있으며 심지어 격자 구성 문제를 해결하지 못해 유동해석을 하지 못하는 경우가 많은 실정이다. 따라서 본 연구에서는 주로 내부 유동인 변형 도관를 예로 유동장 형상에 따라 격자구성이 어떻게 달라지는가를 살펴 보았다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2015년도 제46회 하계학술대회
• /
• pp.251-252
• /
• 2015

The designed hybrid generation system (HGS) not only consider the voltage condition of grid connection point but also do reactive power support according to the transmission system operator's directions. The PCS operation plan in HGS should be supported by precise transferred quantity expectation about reactive power because the system has large physical areas and also be interconnected with grid through long transmission system. Therefore, the realistic measuring process about transferred reactive power quantity by utilizing HGS is required to consider additional compensation plan. In this paper, an reactive power transferred capability of HGS with expected parameter is analyzed, and imposed to the simulation process that is performed on EMTDC environment. Basically, grid information and system characteristics were utilized with Jeju island in Korea, and the performance analysis is carried out based on the composed layout in ongoing project.

• 한국군사과학기술학회지
• /
• 제12권5호
• /
• pp.549-556
• /
• 2009

One of the basic technology for implementing the autonomy of UGV(Unmanned Ground Vehicle) is a path planning algorithm using obstacle and raw terrain information which are gathered from perception sensors such as stereo camera and laser scanner. In this paper, we propose a generation method of DVGM(Directional Velocity Grid Map) which have traverse speed of UGV for the five heading directions except the rear one. The fuzzy system is designed to generate a resonable traveling speed for DVGM from current patch to the next one by using terrain slope, roughness and obstacle information extracted from raw world model data. A simulation is conducted with world model data sampled from real terrain so as to verify the performance of proposed fuzzy inference system.

• 한국항해학회지
• /
• 제19권2호
• /
• pp.13-22
• /
• 1995

This paper presents the numerical analysis results of the viscous flow for a full ship model. The mass and momentum conservation equations are used for governing equations, and the flow field is discretized by the Finite-Volume Method for the numerical calculation. An algebraic grid and elliptic grid generation techniques are adopted for generation of the body-fitted coordinates system, which is suitable to ship's hull forms. Time-marching procedure is used to solve the three-dimensional unsteady problem, where the convection terms are approximated by the QUICK scheme and the 2nd-order central differencing scheme is used for other spatial derivatives. A Sub-Grid Scale turbulence model is used to approximate the turbulence, and the wall function is used at the body surface. Pressure and velocity fields are calculated by the simultaneous iteration method. Numerical calculations were accomplished for the Crude Oil Tanker(DWT 95,000tons, Cb=0.805) model. Calculation results are compared to the experimental results and show good agreements.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제9권2호
• /
• pp.77-84
• /
• 2001

Experimental and computational studies were carried out to investigate the turbulent heat transfer enhancement of the cooling system in nuclear reactor by large scale vortex generation. The large scale vortex motion was generated by rearranging the inclination angels of mixing vanes to the coordinate direction. Axial development of mean and turbulent velocities in the subchannels were measured by the 2-color LDV system. Eddy diffusivity concept based on $\kappa{-}\varepsilon$ model was employed to calculate the turbulent heat and momentum transfers in the subchannel. The turbulences generated by split mixing vanes has small length scales so that they maintain only about $10D_H$ after the spacer grid. On the other hand, the turbulences generated by the large scale vortex motions continue longer and remain up to $25D_H$ after the spacer grid.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 A
• /
• pp.31-33
• /
• 1999

In this paper, a operating characteristics of the 50 kW grid-connected Photovoltaic(PV) Power system which is by means of initial PV datum analyzing is reported. The development of a 50 kW class photovoltaic power generation system including a DC/AC inverter is suggested to investigate the system performance for grid connection. The results of the demonstration test of a 50 kW class grid-connected PV system show that the system utilization rate is 15.6% and the inverter efficiency is 94% at 80% load.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제53권11호
• /
• pp.671-679
• /
• 2004

This paper presents the on-line current controller tuning method of grid-connected inverter using PSO(particle swarm optimization) technique for minimizing the harmonic current. Synchronous frame PI current regulator is commonly used in most distributed generation. However, due to the source voltage distortion, specially in weak AC power system, current may contain large harmonic components, which increase THD(total harmonic distortion) and deteriorates power quality. Therefore, some tuning method is necessary to improve response of current controller. This paper used the PSO technique to tune the current regulator and through simulation and experiments, usefulness of the tuning method has been verified. Especially in simulating the tuning process, ASM(average switching model) of inverter is used to shorten execution time.

• 전기학회논문지
• /
• 제60권7호
• /
• pp.1372-1377
• /
• 2011

This paper proposes the control method of MPPT(maximum power point tracking) for the wind energy generation system using the duty ratio control of boost type DC-DC converter. For a lower cost and a higher reliability, the wind and the generator velocity sensors are removed. MPPT control is implemented by changing the duty ratio of the boost converter. Chain rule is applied by using each function. The grid side inverter is controlled to regulate unity power factor. The proposed control method was analyzed mathematically and verified by the computer simulation using PSIM.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2015년도 전력전자학술대회 논문집
• /
• pp.53-54
• /
• 2015

A new simple and effective scheme to improve power quality for a grid-connected inverter in distributed generation systems under distorted grid voltages will be presented. The proposed scheme is constructed with two controllers to regulate fundamental and harmonic components separately. In order to accomplish the proposed control scheme, the fourth order band pass filter is used to extract harmonic components from distorted gird voltages. Then, the undesired harmonic components are excellently suppressed by proportional decoupling controller. Experimental results are presented to verify the simplicity and effectiveness of proposed scheme.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 추계학술대회 논문집 전력기술부문
• /
• pp.17-20
• /
• 2004

This paper presents a modeling and simulation of a grid-connected wind turbine generation system with respect to wind variations and three-phase fault in the system. It describes the modeling of the wind turbine system including the drive train model, induction generator model, and grid-interface model on MATLAB/Simulink. Case studies demonstrate that the pitch angle control is carried out to achieve maximum power extraction for wind speed variations and the duration of a fault on the system influences on the output of the wind turbine generator.