• Journal of Electrical Engineering and Technology
• /
• 제9권5호
• /
• pp.1447-1453
• /
• 2014

This paper proposes the new method based on the availability of three points measurement and convexity of photovoltaic (PV) curve characteristic at the maximum power point (MPP). In general, the MPP tracking (MPPT) function is the important part of all PV systems due to their power-voltage (P-V) characteristics related with weather conditions. Then, the analog-to-digital converter (ADC) and low pass filter (LPF) are required to measure the voltage and current for MPPT by the digital controller, which is used to implement the PV power conditioning system (PCS). The measurement and quantization error due to rounding or truncation in ADC and the delay of LPF might degrade the reliability of MPPT. To overcome this limitation, the proposed method is proposed while improving the performances in both steady-state and dynamic responses based on the detailed investigation of its properties for availability and convexity. The performances of proposed method are evaluated with the several case studies by the PSCAD/EMTDC$^{(R)}$ simulation. Then, the experimental results are given to verify its feasibility in real-time.

• 전력전자학회논문지
• /
• 제16권1호
• /
• pp.20-29
• /
• 2011

본 논문에서는 동특성이 느린 용융탄산염 연료전지 (Molten Carbonate Fuel Cell, MCFC) 스택을 사용하여 계통사고 시 추가적인 UPS (Uninterruptible Power Supply) 없이 비상부하 (Critical Load)로 전력 공급이 가능하고, 사고 발생 후에도 정격전력으로 발전 가능한 비상부하 추종형 백업 시스템을 제안한다. 제안된 MCFC 발전 시스템용 비상부하 추종형 백업 시스템은 3상 인버터로 구성된 PCS (Power Conditioning System) 출력단에 3상 PWM 컨버터를 연결한 구조이고, 비상부하 추종이 가능한 추가적인 제어 알고리즘을 가지는 Load Leveler를 제어한다. 제안된 비상부하 추종형 백업 시스템의 회로와 제어 알고리즘의 타당성을 5kW 기반의 컴퓨터 시뮬레이션을 통하여 검증한다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
• /
• pp.1339-1342
• /
• 2005

This paper presents a simple AC-DC power conditioner for a squirell-cage induction generator(IG) operating under variable shaft speeds. The necessary reactive power for the IG system is supplied by means of a capacitor bank and a voltage-source PWM converter. Using a capacitor bank to transfer the reactive power to the IG under the rated speed and no-load conditions starts the IG operation and reduces the PWM power converter size. A simple control compensating for changes in the electrical loads as well as the variation in speed was developed to regulate the voltages of the IG system by controlling the rotor flux through its reactive and active currents control implementation. This proposed power conditioning scheme can be used efficiently as a wind power generation system where the output voltage of the IG is maintained constant voltage despite the variable frequency and the DC bus voltage of the PWM converter can be used for either DC applications such as battery charging or AC power applications with 60/50 Hz by connecting a stand alone inverter. The experimental and simulated operating performance results of a 5 kW IG scheme at various speeds and leads are presented.

• 태양에너지
• /
• 제20권1호
• /
• pp.97-108
• /
• 2000

The purpose of this study is to minimize the heat transfer surface area and cold fluid exit temperature of heat exchanger which applied to the refrigeration and air-conditioning system by utilizing the thermoelectric principle. Both uniform and non-uniform current distribution methods which applied to the analysis of the TE elements that incorporates heat exchanger were investigated. The non-uniform current distribution method had the better coefficient of performance and had the lower cold fluid exit temperature of the TE cooling system than the uniform current distribution method. It was found that if a TE cooling system incorporates a heat exchanger, a non-uniform current distribution should guarantee to the lowest cold fluid exit temperature. Also, the hybrid method (combination of the uniform and non-uniform current distribution method) is investigated to achieve the best results by combining the uniform and non-uniform current distributions. The results show that it can lower the cold fluid exit temperature and reduce the heat transfer surface area for the parallel flow arrangement if we apply the constant current in some entry region and the non-uniform increasing current in the direction of the cold fluid flow afterwards.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2006년도 하계학술발표대회 논문집
• /
• pp.325-330
• /
• 2006

Modern people spend more and more time in an automobile in their daily life. In this life, drivers and passengers should create HVAC environment in the automobile interior which is not only for convenient transportation but also give comfortable feeling with dwelling culture. Also, the latest cars give much importance for the role of HVAC system that controls the environment of the area for passengers more than just basic capability. There are solar radiant heat, surface temperature, refrigeration system(temperature, humidity, air current, velocity), and dust for the factor which have an effect on the HVAC environment in the automobile interior, also these are being carried for the HVAC environment delivered an individual character. In this study, we drew the automobile interior as three dimension and arranged a method of numerical analysis on HVAC environment in the automobile interior displaying air current distribution and temperature distribution through simulation of the automobile interior on the ventilation volume and outlet area. The aim of this study is to develop the estimated method for HVAC environment. in the automobile interior.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2006년도 하계학술발표대회 논문집
• /
• pp.707-712
• /
• 2006

Knowing the ground thermal conductivity is very importnat in designing ground heat exchangers. Knowledge of the ground soil and rock composition information dose not guarantee the prediction of accurate thermal information. In Situ testing of ground heat exchangers is becoming popular. However, in situ testing are performed at construction sites in real life. Adequate data collection and analysis are not easy mainly due to poor power quality. Power fluctuation also causes the fluctuation of received data. The power quality must be maintained during the entire in situ testing processes. To accurately analyse the test data, the understanding of the response of the power fluctuation is essential. Testing under the power quality varied by tester is very difficult. Analyzing power variation by numerical simulation is a realistic option. By varying power in a sinosuidal manner, its effects on predicting thermal conductivity from thermal response plots made from the test data are examined.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2006년도 하계학술발표대회 논문집
• /
• pp.1087-1092
• /
• 2006

Recently, traffic noise level is rapidly increasing, and it is crowed caused by recently overcrowded and overgrown cities, and increasing traffic volume is emerging as a major factor of disrupting the living and working environment. In this situation, citizens are increasingly complaining about the traffic noise. The noise level of in major cities in Korea is serious and affects on citizens physically and psychologically. Many people live in residential areas around crowed roads in major cities, such as Seoul. Accordingly, the purpose of this study is to predict outside noise distribution of building through survey and simulation to make better sound insulation performance research. The result of this study shows that the traffic noise is influenced from ground 50m and analyzed that form of building and arrangement type must be considered to the level of noise decrease.

• 한국태양에너지학회 논문집
• /
• 제39권2호
• /
• pp.81-92
• /
• 2019

When Photovoltaic inverter is connected to grid and used as PVPCS (Photovoltaic Power Conditioning System), 120 Hz AC ripple occurs at the dc-link capacitor voltage. This AC ripple reduces the efficiency of PVPCS and shortens the lifetime of the capacitor. In this paper, we design a notch filter to remove AC ripple. As a result, the AC voltage ripple was removed from the dc link and the THD of the PVPCS output current with the notch filter was lowered. This notch filter is determined by the damping coefficient, the bandwidth coefficient, and the switching frequency. Among these, the switching frequency determines the switching loss and the size of the LC filter, and the PVPCS with the high switching frequency has a greater efficiency loss due to the switching loss than the efficiency improvement by the notch filter. Therefore, it is important to set the optimum switching frequency in the PVPCS with the notch filter applied. In this paper, THD and switching loss of PVPCS output current with notch filter are calculated through simulation, and cost function to calculate optimum switching frequency through data is proposed.

• 한국산업보건학회지
• /
• 제32권2호
• /
• pp.111-115
• /
• 2022

Objectives: The purpose of this study is to verify whether droplet-induced propagation, the main route of infectious diseases such as COVID-19, can occur in semiconductor FAB (Fabrication), based on research results on general droplet propagation. Methods: Through data surveys droplet propagation was modeled through simulation and experimental case analysis according to general (without mask) and mask-wearing conditions, and the risk of droplet propagation was inferred by reflecting semiconductor FAB operation conditions (air current, air conditioning system, humidity, filter conditions). Results: Based on the results investigated to predict the possibility of spreading infectious diseases in semiconductor FAB, the total amount of droplet propagation (concentration), propagation distance, and virus life in FAB were inferred by reflecting the management parameter of semiconductor FAB. Conclusions: The total amount(concentration) of droplet propagation in the semiconductor fab is most affected by the presence or absence of wearing a mask and the line air dilution rate has some influence. when worn it spreads within 0.35~1m, and since the humidity is constant the virus can survive in the air for up to 3 hours. as a result the semiconductor fab is judged to be and effective space to block virus propagation due to the special environmental condition of a clean room.

• Structural Engineering and Mechanics
• /
• 제83권4호
• /
• pp.465-473
• /
• 2022

In this research, a numerical study has been provided for examining the nonlinear stability behaviors of sandwich beams having a cellular core and two face sheets made of nanocomposites. The nonlinear stability behaviors of the sandwich beam having geometrically perfect/imperfect shapes have been studied when it is subjected to a compressive buckling load. The nanocomposite face sheets are made of epoxy reinforced by graphene oxide powders (GOPs). Also, the core has the shape of a honeycomb with regular configuration. Using finite element method based on a higher-order deformation beam element, the system of equations of motions have been solved to derive the stability curves. Several parameters such as face sheet thickness, core wall thickness, graphene oxide amount and boundary conditions have remarkable influences on stability curves of geometrically perfect/imperfect sandwich beams.