• 전기학회논문지
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• 제58권7호
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• pp.1313-1320
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• 2009

This paper analyzes the steady-state operating characteristics of doubly-fed induction generator(DFIG) and fixed-speed induction generator(FSIG) in wind turbine system. It also presents a modeling and simulation of a grid-connected wind turbine generation system for dynamics analysis on MATLAB/Simulink, and compares the responses between DFIG and FSIG wind turbine systems with respect to wind speed variation, 3-phase fault and 1-phase ground fault of the network. Simulation results show the variations of generator's active/reactive output, rotor speed, terminal voltage, fault current, etc. Case studies demonstrate that DFIG illustrates better performance compared to FSIG.

• 한국추진공학회지
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• 제3권4호
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• pp.104-108
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• 1999

삼성항공(주)은 국내 유일의 가스터빈 전문업체로서 가스터빈과 터보기기 분야에서 다양한 사업들을 펼쳐왔다. 그 중에서 가스터빈 정비조립 사업, 부품제조 사업, 그리고 터보기기 사업의 현황과 생산, 기술, 개발 측면에서 현재의 능력과 수준을 조망해보고 향후의 사업 전개 방향에 대해서 간략히 소개하여 관련분야에 종사하는 분들에게 국내 가스터빈 산업의 현주소를 파악하는데 도움이 되고자 하였다.

• 전기학회논문지
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• 제58권12호
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• pp.2402-2409
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• 2009

This paper proposed a simple and helpful analysis model of voltage variation in order to predict the voltage variation at PCC (Point of Common Coupling), when a wind turbine is connected in an isolated grid. The PCC voltage flucuates when the wind turbine outputs active power to an isolated grid. This voltage variation is proportional to the product of the line impedance from the ideal generator to the PCC and the wind turbine output current. And It is different according as where wind turbine is connected. To solve the problem of voltage variation, this paper proposed the reactive power control. To verify the proposed analysis model, this paper utilized PSCAD/EMTDC Simulation and the field measurement data of the voltage variation during the wind power generation.

• Journal of Electrical Engineering and Technology
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• 제11권4호
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• pp.801-809
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• 2016

The electrically excited synchronous generator (EESG) is applied in wind turbine systems recently. In an EESG control system, electrical torque is affected by stator flux and rotor current. So the control system is more complicated than that of the permanent-magnet synchronous generator (PMSG). Thus, the higher demanding of the control system is required especially in case of wind turbine mechanical resonance. In this paper, the mechanism of rotor speed resonant phenomenon is introduced from the viewpoint of mechanics firstly, and the characteristics of an effective damping torque are illustrated through system eigenvalues analysis. Considering the variables are tightly coupled, the four-order small signal equation for torque is derived considering stator and rotor control systems with regulators, and the bode plot of the closed loop transfer function is analyzed. According to the four-order mathematical equation, the stator flux, stator current, and electrical torque responses are derived by torque reference step and ramp in MATLAB from a pure mathematical deduction, which is identical with the responses in PSCAD/EMTDC simulation results. At last, the simulation studies are carried out in PSCAD software package to verify the resonant damping control strategy used in the EESG wind turbine system.

• 한국기계가공학회지
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• 제17권5호
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• pp.52-57
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• 2018

Most current ships have adopted on-board diesel generators to produce electricity, but the overall efficiency of equipment is down to about 50% due to thermal losses from operations such as exhaust gas, jacket water cooler, scavenge air cooler, etc. Recently, fuel cells have been highlighted as a promising technology to reduce the effect on the environment and have a higher efficiency. Therefore, this paper suggested a solid oxide fuel cell (SOFC)-gas turbine (GT) using waste heat from a SOFC and SOFC-GT-steam turbine (ST) with Rankine cycle. To compare both configurations, the fuel flow rate, current density, cell voltage, electrical power, and overall efficiency were evaluated at different operating loads. The overall efficiency of both SOFC hybrid systems was higher than the conventional system.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.80-90
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• 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 Power Electronics
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• 제15권1호
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• pp.235-245
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• 2015

This paper proposes a reactive current assignment and control strategy for a doubly-fed induction generator (DFIG) based wind-turbine generation system under generic grid voltage sag or swell conditions. The system's active and reactive power constrains during grid faults are investigated with both the grid- and rotor-side convertors (GSC and RSC) maximum ampere limits considered. To meet the latest grid codes, especially the low- and high-voltage ride-through (LVRT and HVRT) requirements, an adaptive reactive current control scheme is investigated. In addition, a torque-oscillation suppression technique is designed to reduce the mechanism stress on turbine systems caused by intensive voltage variations. Simulation and experiment studies demonstrate the feasibility and effectiveness of the proposed control scheme to enhance the fault ride-through (FRT) capability of DFIG-based wind turbines during violent changes in grid voltage.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.357-358
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• 2015

This paper provides a comparison of power converter loss and thermal description for voltage source and current source type 5MW-class medium voltage topologies of wind turbines. Neutral-point clamped three-level converter is adopted for voltage source type topology while two-level converter is employed for current source type topology considering the popularity in the industry. In order to match the required voltage level of 4160V with the same switching device of IGCT as in voltage source converter, two active switches are connected in series for the case of current source converter. The loss analysis is confirmed through PLECS simulations. In addition, the loss factors due to di/dt and dv/dt snubber and ac input filter are presented. The comparison result shows that VSC-based wind turbine system has a higher efficiency than that of CSC under the rated operating conditions.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.130-133
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• 2006

It is well-known that the resources for tide and tidal current energy are abundant in Korea. The south coast in Korea is recognized as one of the most appropriate places in the world for developing tidal current energy. The target site for harnessing tidal current energy is the Uldolmok, where the strongest tidal current in Korea occurs. In order to commercialize and industrialize the tidal current power generation, the construction of pilot tidal current power plant of 1MW has been started in April 2006, and is expected to be completed by May 2007. Extensive works including field investigation, field experiment for evaluating the efficiency of helical turbine and numerical analysis have been performed. This paper present the several design parameters for constructing the Uldolmok pilot tidal current power plant.

• Journal of Advanced Marine Engineering and Technology
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• 제35권7호
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• pp.914-920
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• 2011

For a hydro turbine electricity generation system in river or bay, a venturi system could be applied to accelerate flow speed at the inlet of the turbine system in a flow field. In this study, a steady flow simulation was conducted to understand the effect of venturi system on the acceleration of current speed at the inlet of a hydro turbine system. According to the continuity equation, the flow speed is inversely proportional to the cross-section area in a conduit flow; however, it would be different in an open region because the venturi system would be an obstruction in the flow region. As the throat area is 1/5 of the inlet area of the venturi, the flow velocity is accelerated up to 2.1 times of the inlet velocity. It is understood that the venturi system placed in an open flow region gives resistance to the upcoming flow and disperses the flow energy around the venturi system. The result of the study should be very important information for an optimum design of a hydro turbine electricity generation system.