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박봉희(Park, Bong-Hee),김승민(Kim, Seung-Min),최주엽(Choi, Ju-Yeop),최익(Choy, Ick),이상철(Lee, Sang-Chul),이동하(Lee, Dong-Ha) 한국태양에너지학회 2013 한국태양에너지학회 학술대회논문집 Vol.2013 No.4
This paper proposes a modeling of fuel cell which replaces dc source during simulation. Fuel cells are electrochemical devices that convert chemical energy in fuels into electrical energy. This system has high efficiency and heat, no environmental chemical pollutions and noise. Proton exchange membrane fuel cells(PEMFC) are commonly used as a residential generator. These fuel cells have different electrical characteristics such as a low voltage and high current compared with solar cells. And there are different behaviors in the V-I curve in the temperature and pressure. Therefore, the modeling of fuel cell should consider wide voltage range and slow current response and the resulting electrical model is applied to power converter system(PCS) with fuel cell as an input source.
박봉희(Park Bong-Hee),최주엽(Choi Ju-Yeop),최익(Choy Ick),이상철(Lee Sang-Cheol),이동하(Lee Dong-Ha) 한국태양에너지학회 2014 한국태양에너지학회 논문집 Vol.34 No.1
This paper proposes a modeling of fuel cell which replaces dc source during simulation. Fuel cells are electrochemical devices that convert chemical energy in fuels into electrical energy. This system has high efficiency and heat, no environmental chemical pollutions and noise. Proton exchange membrane fuel cells(PEMFC) are commonly used as a residential generator. These fuel cells have different electrical characteristics such as a low voltage and high current compared with solar cells. And there are different behaviors in the V-Icurve in the temperature and pressure. Therefore, the modeling of fuel cell should consider wide voltage range and slow current response and the resulting electrical model is applied to boost converter with fuel cell as an input source.
태양광 / 연료전지용 배터리 충·방전 하이브리드 시스템 설계
박봉희(Park Bong-Hee),조영민(Jo Yeong-min),최주엽(Choi Ju-Yeop),조상윤(Cho Sang-Yoon),최익(Choy Ick),이동하(Lee Dong-Ha) 한국태양에너지학회 2014 한국태양에너지학회 논문집 Vol.34 No.4
Photovoltaic and fuel cell systems can be used as power source in mobile robots. At this time the photovoltaic system generally generate power in daytime. The starting time of fuel cell is slower than the lithium battery. To compensate for these disadvantages, a battery charge-discharge system is used. Especially the bi-directional converter is used mainly in the charge-discharge method. The controller in a buck converter controls the input voltage of the converter to meet the maximum power point tracking(MPPT) performance. First of all, the simulations of hybrid system for battery charge-discharge system in each step simulated using solar and fuel cell modeling as input source in PSIM. Experiment of the buck and bi-directional converter system is conducted through using photovoltaic/fuel cel simulator(pCube) instead of solar and fuel cell. This hybrid system for battery charge·discharge using photovoltaic/fuel cell generates emergency power for the communication system in mobile robot.
박봉희(Park, Bong-Hee),김승민(Kim, Seung-Min),최주엽(Choi, Ju-Yeop),최익(Choy, Ick),이상철(Lee, Sang-Chul),이동하(Lee, Dong-Ha),이영권(Lee, Young-Kwon) 한국태양에너지학회 2013 한국태양에너지학회 논문집 Vol.33 No.6
This paper proposes DC offset current compensation method of transformerless fuel cell/PV PCS. DC offset current is generated by the unbalanced internal resistance of the switching devices in full bridge topology. The other cause is the sensitivity of the current sensor, which is lower than DSP in resolution. If power converter system has these causes, the AC output current in the inverter will generate the DC offset. In case of transformerless grid-connected inverter system, DC offset current is fatal to grid-side, which results in saturating grid side transformer. Several simulation results show the difficulties of detecting DC offset current. Detecting DC offset current method consists of the differential amplifiers and PWM is compensated by the output of the Op amp circuit with integrator controller. PSIM simulation verifies that the proposed method is simpler and more effective than using low resolution current sensor alone.
박봉희(Park Bong-Hee),김승민(Kim Seung-Min),최주엽(Choi Ju-Yeop),최익(Choy Ick),이상철(Lee Sang-Cheol),이동하(Lee Dong-Ha),이영권(Lee Young-Kwon) 한국태양에너지학회 2013 한국태양에너지학회 학술대회논문집 Vol.2013 No.11
This paper proposes DC offset current compensation method of trans-less fuel cell/PV PCS. DC off set current is generated due to the unbalanced internal resistance of the switching devices in full bridge topology. The other cause of DC off set current is that the sensitivity of the current sensor is lower than the resolution of the DSP. If inverter is controlled by the current including DC offset, it"s AC output current will generate DC offset. In case of trans-less grid-connected inverter system, DC offset current is fatal to grid, which results in saturating grid side transformer. Several simulation results with different unbalanced conditions show the difficulties of detecting of DC offset current. Op amp circuit detecting DC offset current functions both amplifier and differential. It provides compensated DC offset component PWM circuit. PSIM simulation verifies that the proposed method is simpler and more effective than using low resolution current sensor alone.
박봉희(Park Bong-Hee),정승환(Seung-Whan Jeon),최주엽(Ju-Yeop Choi),최익(Choy Ick),이상철(Lee Sang-Cheol),이동하(LeeDong-Ha) 한국태양에너지학회 2014 한국태양에너지학회 논문집 Vol.34 No.2
Generally, buck converter controller is designed to control the output voltage of the converter. However, design of the controller in a photovoltaic power conditioning system is different from theoretical design guideline. The controller in a photovoltaic power conditioning system controls the input voltage of the converter (the output voltage of the solar cell) to meet a maximum power point tracking (MPPT) performance. In this study, a new model for buck converter used in a photovoltaic power conditioning system is proposed, which is linearized after state-space averaging in each period. Also, mathematical expression of the modeled buck converter is interpreted separately as small and large signals; therefore its appropriateness is measured to design linear voltage and current controller.
전립선비대증 환자에서 경요도전립선절제술 후 요도협착의 발생에 영향을 주는 예측인자들
박봉희 ( Bong Hee Park ),정영범 ( Young Beom Jeong ),박영경 ( Young Kyung Park ) 전북대학교 의과학연구소 2005 全北醫大論文集 Vol.29 No.2
Purpose: To evaluate possible factors affecting urethral stricture development after TURP in patients with BPH. Materials and Methods: We reviewed retrospectively medical records of patients who underwent TURP due to BPH for past 5 years. All operations were performed by 2 experienced doctors who have minimum 200 practices. Patients were classified into 2 groups. Group A included patients with urethral stricture required periodic urethral dilation in outpatient basis postoperatively. Group B included those without urethral stricture development after TURP. We analyzed all possible factors such as resection time, prostate volume, resection volume, resectoscope size, preoperative catheterization duration due to AUR, postoperative catheterization duration, preoperative and postoperative pyuria, prostate needle biopsy performed preoperatively and PSA level, age and co-morbid systemic diseases. We also compared patients with narrow urethral caliber preoperatively (Group I) those who were inserted 22Fr resectoscope without resistance (Group II) in terms of aforementioned factors. Results: 518 patients underwent TURP between 2000 and 2004. 69 of them were categorized into group I and 449 into group II. And Of the group II 100 were categorized into group A and 349 into group B. There was no statistical difference between group A and B with respect to age, preoperative catheterization duration in patients with AUR, postoperative catheterization duration, prostate volume, resection volume, preoperative PSA level, preoperative pyuria, postoperative pyuria, preoperative biopsy history, resectoscope size (22F vs 24F) and anesthesia method (general vs spinal), respectively. However, there is significant difference between group A and B in comparison of resection time (58.5±21.6min vs 50.5±23.2min, p=0.02) There was no statistical difference between group I and II with respect to all factors, except urethral stricture development (p<0.05). Conclusions: Our data suggest that the shortening of resection time is the most important single factor to decrease urethral stricture formation after TURP in patients with BPH. Also, we think that the innate urethral caliber is a significant factor about urethral stricture development after TUR-P.
박봉희(Park, Bong-Hee),김승민(Kim, Seung-Min),최주엽(Choi, Ju-Yeop),최익(Choy, Ick),이상철(Lee, Sang-Chul),이동하(Lee, Dong-Ha) 한국태양에너지학회 2012 한국태양에너지학회 학술대회논문집 Vol.2012 No.11
This paper proposes a modeling of fuel cell which replaces dc source during simulation. Fuel cells are electrochemical devices that convert chemical energy in fuels into electrical energy. This system has high efficiency and heat, no environmental chemical pollutions and noise. These fuel cells are consisted of many different materials such as solid oxide fuel cell(SOFC) and proton exchange membrane fuel cell(PEMFC). But these fuel cells have similar electrical characteristics such as a low voltage and high current compared with solar cells. However, there are different behaviors in the V-I curve in the high temperature. Therefore, the modeling of fuel cell should consider wide voltage range and slow current response and the resulting electrical model is applied to power converter system(PCS) with fuel cell as an input source.