• 한국태양에너지학회 논문집
• /
• 제29권6호
• /
• pp.1-13
• /
• 2009

Photovoltaic conditioning systems normally use a maximum power point tracking (MPPT) technique to deliver the highest possible power to the load continuously when variations occur in the insolation and temperature. A unique method of tracking the maximum power points (MPPs) and forcing the boost converter system to operate close to these points is presented through deriving small-signal model and transfer function of boost converter considering input capacitor. This paper aims at modeling boost converter including fairly large equivalent series resistance(ESR) of input reservoir capacitor by state-space-averaging method and PWM switch model and compares both methods using Bode plots. In the future, properly designed controller for compensation will be constructed in 3kw real system for maximum photovoltaic power tracking control.

• 한국태양에너지학회 논문집
• /
• 제28권5호
• /
• pp.85-95
• /
• 2008

Photovoltaic conditioning systems normally use a maximum power point tracking (MPPT) technique to deliver the highest possible power to the load continuously when variations occur in the insolation and temperature. A unique method of tracking the maximum power points (MPPs) and forcing the boost converter system to operate close to these points is presented through deriving small-signal model and transfer function of boost converter considering input capacitor. This paper aims at modeling boost converter including fairly large equivalent series resistance(ESR) of input reservoir capacitor by state-space-averaging method and PWM switch model. In the future, properly designed controller for compensation will be constructed in 3kw real system for maximum photovoltaic power tracking control.

• 전기학회논문지
• /
• 제65권4호
• /
• pp.684-688
• /
• 2016

The magnetic resonance method requires high quality factor(Q-factor) of resonators. Superconductor coils were used in this study to increase the Q-factor of wireless power transfer(WPT) systems in the magnetic resonance method. The results showed better transfer efficiency compared to copper coils. However, as superconducting coils should be cooled below critical temperatures, they require cooling containers. In this viewpoint, shielding materials for the cooling containers were applied for the analysis of the WPT characteristics. The shielding materials were applied at both ends of the transmitter and receiver coils. Iron, aluminum, and plastic were used for shielding. The electric field distribution and S-parameters (S11, S21) of superconducting coils were compared and analyzed according to the shield materials. As a result, plastic shielding showed better transfer efficiency, while iron and aluminum had less efficiency. Also, the maximum magnetic field distribution of the coils according to the shielding materials was analyzed. It was found that plastic shielding had 5 times bigger power transfer rate than iron or aluminum. It is suggested that the reliability of superconducting WPT systems can be secured if plastic is used for the cooling containers of superconducting resonance coils.

• 한국전자파학회논문지
• /
• 제24권2호
• /
• pp.168-179
• /
• 2013

4-코일 자기 공진 무선 전력 전송 시스템의 해석법 중 critical point analysis(CA)와 impedance matching analysis(IA)를 분석하고, 두 결과를 비교하였다. 4-코일 시스템은 가까운 거리에서는 주파수 분리 현상이 나타나고, 먼 거리에서는 효율이 급격히 감소하는 특징을 나타낸다. 따라서 고정된 주파수에서 사용할 경우, 목표하는 거리와 효율에 따라 최적화가 필요하다. CA는 전체 거리에서 효율이 최대가 되는 critical point를 이용하여 최적화하는 방법이고, IA는 목표 지점에서 임피던스 정합을 이뤄 최대 효율을 만족시키는 방법이다. 기존의 해석은 두 가지 방법을 비교하고 시스템 특성을 이해하는데 부족한 점이 있었기 때문에, 본 논문에서 두 방법의 이론을 좀 더 자세히 분석하고 비교하였다. 두 방법의 비교 결과를 통해 IA가 더 우수함을 보였다. 또한, 한쪽만 정합할 경우 발생되는 트레이드-오프에 대해서도 설명하였다. 스파이럴 공진 코일을 이용한 실험에서는 이론 결과와 동일한 결과를 얻을 수 있었다.

• 한국항공우주학회지
• /
• 제30권6호
• /
• pp.84-91
• /
• 2002

본 연구에서는 열전달 해석을 통하여 발전용 터빈 블레이드의 온도 분포를 계산하였고, 열하중과 원심력에 의한 선형응역 해석을 수행하였다. 정상상태 열전달 해석 결과, 블레이드의 앞전과 끝단에서 높은 온도 분포가 나타났으며 열응력은 다른 부분에 비해 압력면 부분에서 높게 나타났다. 온도의 영향을 고려하지 않은 원심응력 해석에는 fir tree 앞전 부분에서 가장 높은 등가 응력이 나타났다. 온도와 원심력을 모두 고려한 해석 결과에서도 최대 등가 응력은 fir tree부분에서 발생하였다. 열하중과 원심력에 대한 선형응력 해석 결과 GTD111 터빈 블레이드는 항복응력에 도달하지 않아 안전하다.

• Journal of Power Electronics
• /
• 제17권2호
• /
• pp.453-463
• /
• 2017

This paper discusses the measurement of frequency response functions for various dc-dc converters. The frequency domain identification procedure is applied to the measured frequency responses. The identified transfer functions are primarily used in developing behavioral models for dc-dc converters. Distributed power systems are based upon such converters in cascade, parallel and several other configurations. The system level analysis of a complete system becomes complex when the identified transfer functions are of high order. Therefore, a certain technique needs to be applied for order reduction of the identified transfer functions. During the process of order reduction, it has to be ensured that the system retains the dynamics of the full order system. The technique used here is based on the Hankel singular values of a system. A systematic procedure is given to retain the maximum energy states for the reduced order model. A dynamic analysis is performed for behavioral models based on full and reduced order frequency responses. The close agreement of results validates the effectiveness of the model order reduction. Stability is the key design objective for any system designer. Therefore, the measured frequency responses at the interface of the source and load are also used to predict stability of the system.

• 전기학회논문지
• /
• 제58권3호
• /
• pp.437-443
• /
• 2009

In recent years, electric power systems have been experiencing a rapid change due to the increasing electricity market. For the effective use of power system under the deregulated environment, it is important to make a fast and accurate calculation of the maximum available transfer capability (ATC) from a supply point to a demand point. In this paper, the purpose of this research is to calculate ATC fast and accurately for securing the stability of system and raising the efficiency as a result of anticipating transmission congestion according to transmission open access progressed in the future under the regulated environment of electricity market. In this paper, a study utilized a relation of the potential energy and energy function by which calculated CCT and then utilized a relation of PEBS for transient stability ATC calculation. In this paper, ATC was calculated as RPF and Energy Function method and calculation results of each method was compared. Contingence ranking method decided the weak bus by the Eigenvalues of Jacobian matrix and overloading branches by PI-index. As a result, a study proved the fast and accurate ATC calculation method considering transient stability suggested in this paper. Through the case study using New England 39 bus system, it is confirmed that the proposed method can be used for real time operation and the planning of electric market.

• 대한전자공학회논문지SD
• /
• 제48권10호
• /
• pp.1-5
• /
• 2011

근접 통신 시스템(NFC)의 전력 전송 효율과 수동형 RFID의 동작 거리 향상을 위해 자기 공명 공진코일을 이용한 무선전력전송 방식을 근접 통신 단말에 적용하였다. 소스코일과 디바이스코일 사이에 공진코일을 배치시켜 시스템을 구성하였으며, 효율을 13.56MHz 대역의 RFID 리더와 태그 시스템을 사용하여 측정하였고, 3차원 시뮬레이터를 통하여 시뮬레이션 하였다. RFID 리더와 태그를 통해 측정한 결과, 자기 공명 공진코일을 적용한 경우 신호의 송수신 최대 거리는 96.72%, RFID 태그의 수신된 전압은 17.95% 증가함을 보였다.

• 한국유체기계학회 논문집
• /
• 제18권1호
• /
• pp.29-36
• /
• 2015

Recently, Stirling engines are emerging as a key device for power conversion of renewable energy or waste energy. This study develops a LTDSE(Low Temperature Differential Stirling Engine) using a water spray for higher heat transfer and performs load performance tests for various flow rates and temperatures of hot water spray for variable engine loads emulated by a mechanical friction device. Internal temperature and pressure, working frequency and inlet and outlet temperature of the supply water are measured. As a result, the increases in flow rate and temperature of hot water respectively enhance the power output, efficiency and the working frequency, while the increasing engine load leads to decreases in working frequency but increases in the pressure amplitude. Eventually, it is revealed there exists a maximum shaft power of the test engine.

• Nuclear Engineering and Technology
• /
• 제25권1호
• /
• pp.166-177
• /
• 1993

사용후 핵연료 건식 저장 캐니스터의 핵연료 바스켓 안에 있는 CANDU 37소자 핵연료 다발의 최대 온도를 계산하기 위한 단순화된 열해석 방법과 함께 대기 조건 인자들이 캐니스터 내부의 최대 핵연료 온도에 미치는 영향을 조사하기 위해 수행한 표본 해석 결과를 제시하였다. 3가지 모우드(mode)의 열전달이 공존하는 캐니스터 내부핵연료 다발의 복잡한 기하학적 구조에 대한 다차원열전달 문제를 풀기 위하여 건식저장 캐니스터에 저장된 CANDU 사용후 핵연료 다발들을 등가 및 동심의 핵연료 실린더(cylinder)로 대치하였다. 추가적인 입력 자료 및 열전달 상관식을 이용하여 등가 핵연료 실린더의 단순화된 축대칭, 2차원, 복수 모우드(multi-mode)의 열전달 문제를 기존의 컴퓨터 코드인 HEATING5로 해석하였다. 예측한 온도 분포와 식물 모형 실험 결과의 비교는 만족스러울 정도로 일치함을 보여주고 있다.