• Journal of Power Electronics
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• 제6권1호
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• pp.52-66
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• 2006

This paper proposes a wind energy conversion system connected to a grid using a self-excited induction generator (SEIG) based on the maximum power point tracking (MPPT) control scheme. The induction generator (IG) is controlled by the MPPT below the base speed and the maximum energy can be captured from the wind turbine. Therefore, the stator currents of the IG are optimally controlled using the indirect field orientation control (IFOC) according to the generator speed in order to maximize the generated power from the wind turbine. The SEIG feeds a (CRPWM) converter which regulates the DC-link voltage at a constant value where the speed of the IG is varied. Based on the IG d-q axes dynamic model in the synchronous reference frame at field orientation, high-performance synchronous current controllers with satisfactory performance are designed and analyzed. Utilizing these current controllers and IFOC, a fast dynamic response and low current harmonic distortion are attained. The regulated DC-link voltage feeds a grid connected CRPWM inverter. By using the virtual flux orientation control and the synchronous frame current regulators for the grid connected CRPWM inverter, a fast current response, low harmonic distortion and unity power factor are achieved. The complete system has been simulated with different wind velocities. The simulation results are presented to illustrate the effectiveness of the proposed MPPT control scheme for a wind energy system. In the simulation results, the d-q axes current controllers and DC-link voltage controller give prominent dynamic response in command tracking and load regulation characteristics.

• 한국전산유체공학회지
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• 제10권3호
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• pp.43-47
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• 2005

In this study, the numerical and dynamic simulation on staging problem including forward jet mechanism is conducted. The forward jet plays a vital role in staging, which jets out from aftbody. This staging environment needs full dynamic characteristics study and flow analysis for securing staging safety. Present study performs dynamic simulation of forebody and aftbody with flow analysis using the Chimera grid scheme which is usually used for moving body simulations. As a result, the separation mechanism using forward jet well work in staging for given initial conditions and reverse thrust, chamber pressure variation from experiments. Furthermore, it is found that the technique using forward jets for staging is excellent for securing the separation safety.

• Journal of Information Processing Systems
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• 제4권3호
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• pp.103-112
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• 2008

This paper proposes a policy adjuster-driven Grid workflow management system for collaborative healthcare platform, which supports collaborative heart disease diagnosis applications. To select policies according to service level agreement of users and dynamic resource status, we devised a policy adjuster to handle workflow management polices and resource management policies using policy decision scheme. We implemented this new architecture with workflow management functions based on policy quorum based resource management system for providing poincare geometrycharacterized ECG analysis and virtual heart simulation service. To evaluate our proposed system, we executed a heart disease identification application in our system and compared the performance to that of the general workflow system and PQRM system under different types of SLA.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.458_459
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• 2009

This paper analyzes the dynamic characteristics for doubly-fed induction generator(DFIG) in wind turbine system. This paper presents a modeling and simulation of a grid-connected wind turbine generation system for dynamics analysis on MATLAB/Simulink, and analyzes the responses DFIG wind turbine system for stiffness of linked system. Simulation results show the variations of generator's active/reactive output, terminal voltage, fault current, etc.

• Journal of Computing Science and Engineering
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• 제7권1호
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• pp.44-52
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• 2013

This paper addresses the problem of resource scheduling in a grid computing environment. One of the main goals of grid computing is to share system resources among geographically dispersed users, and schedule resource requests in an efficient manner. Grid computing resources are distributed, heterogeneous, dynamic, and autonomous, which makes resource scheduling a complex problem. This paper proposes a new approach to resource scheduling in grid computing environments, the hierarchical stochastic Petri net (HSPN). The HSPN optimizes grid resource sharing, by categorizing resource requests in three layers, where each layer has special functions for receiving subtasks from, and delivering data to, the layer above or below. We compare the HSPN performance with the Min-min and Max-min resource scheduling algorithms. Our results show that the HSPN performs better than Max-min, but slightly underperforms Min-min.

• 전력전자학회논문지
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• 제22권1호
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• pp.89-93
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• 2017

This study proposes a grid voltage estimation scheme without a phase delay in the voltage-sensorless control of a grid-connected inverter to enhance its economic feasibility, such as manufacturing cost and system complexity. The proposed scheme estimates grid voltages using a disturbance observer (DOB)-based current controller to control the grid-connected inverter without grid-side voltage sensors. The proposed voltage-sensorless control scheme can be applied successfully to grid-connected inverters, which should be operated with synchronization to the grid, considering the phase angle of the grid can be effectively detected through estimating the grid voltages by DOB. However, a problem associated with the phase delay in estimated grid voltages remains because the DOB has dynamic behavior similar to low-pass filter. Hence, the estimated grid voltages are compensated by a phase lead compensator to overcome the limitation. The effectiveness of the proposed control and estimation schemes is proven through simulations and experiments using a 2 kVA prototype inverter.

• 한국정보과학회논문지:정보통신
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• 제32권4호
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• pp.471-482
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• 2005

고속 네트워크의 등장으로 관리 영역을 초월한 계산 자원의 공유가 가능한 그리드 컴퓨팅 개념이 등장하게 되었다. 그리드 컴퓨팅 환경에 포함된 각 자원들은 이질적이기 때문에 고성능을 얻기 위해서는 효과적인 자원 발견 및 자원 선택이 중요하다. 본 논문에서는 그리드 컴퓨팅에서 다양하고 이질적인 자원들을 각 응용 프로그램에서 효율적으로 이용할 수 있도록, 각 참여자들에게 순위를 부여하고 각 작업(Task)에 적절한 자원을 할당하여 전반적인 시스템 성능을 극대화시키는 메커니즘을 제안하였다. 각 참여자의 순위는 초기에 각 참여자별 자원의 시스템 사양(예:CPU 속도, RAM 크기)등 정적 요소를 고려하여 결정되며, 추후에는 각 참여자들이 작업을 마친 후 제공되는 반환 값의 정확도, 응답시간과 같은 요소를 고려하여 동적으로 수행될 수 있도록 하였다. 이러한 순위에 따른 작업 재분배 메커니즘은 전체적인 시스템 성능을 향상시키고 정확도를 높인다.

• 한국시뮬레이션학회논문지
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• 제19권2호
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• pp.81-89
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• 2010

생물학 데이터 마이닝은 생물학 데이터의 볼륨이 급격하게 증가함에 따라 최근 주목받고 있다. 그리드 기술은 계산 자원과 데이터 공유와 활용을 가능하게 한다. 이 논문에서는 생물학 데이터 마이닝과 그리드 기술을 결합한 혼합형 시스템을 제안한다. 특히, 생물학 데이터 마이닝의 처리 효율성을 위해 결정 범위 조정 알고리즘을 사용한다. 우리는 이 알고리즘을 통해 빠르고 자동으로 신뢰할 만한 데이터 마이닝 인식률을 얻는다. 게다가 그리드 환경에서는 지리적으로 분산된 자원들을 연동하기 때문에 통신량과 자원 할당이 이슈가 된다. 우리는 동적 로드 밸런싱을 제안하고 그리드 기반 생물학 데이터 마이닝 기법에 적용한 다. 성능 평가를 위해 우리는 평균 처리 시간, 평균 통신 시간, 평균 자원 활용도를 측정한다. 측정 실험의 결과는 제안된 두 알고리즘을 적용한 우리의 기법이 처리 시간과 비용 측면에서 이점을 제공한다는 것을 보여준다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2009년도 춘계학술대회 논문집
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• pp.105-110
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• 2009

Distributed Generation (DG) is predicted to play a important role in electric power system in the near future. insertion of DG system into existing distribution network has great impact on real-time system operation and planning. It is widely accepted that micro turbine generation (MTG) systems are currently attracting lot of attention to meet customers need in the distributed power generation market In order to investigate the performance of MT generation systems, their efficient modeling is required. This paper presents the modeling and simulation of a MT generation system suitable for grid-connected operation. The system comprises of a permanent magnet synchronous generator driven by a MT. A brief description of the overall system is given, and mathematical models for the MT and permanent magnet synchronous generator are presented. Also, the use of Power electronics in conditioning the power output of the generating system is demonstrated. Simulation studies with MATLAB/Simulink have been carried out in grid-connected operation mode of a DG system. The control strategies for grid connected operation mode of DG system is also presented.

• 조명전기설비학회논문지
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• 제26권8호
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• pp.42-49
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• 2012

Grid-connected photovoltaic generator system requires high performance PCS(Power Conditioning System) according to the standard of 'Distributed Generation Grid-Connected Technology Standards'. This paper presents the MPPT control method which improves output efficiency through fast tracking to the maximum power point of PV and a reduced self-excited vibration. Secondly, in this paper DVR function was applied to PCS to compensate the voltage sag frequently happening for a power system. The proposed PCS control is analyzed and compared to conventional PCS operating characteristic, the various insolation and loads, and voltage sag condition through PSIM tool. It proves the utility.