A Current Shaping Method for PV-AC Module DCM-Flyback Inverter under CCM Operation

Young-Hyok Ji,Doo-Yong Jung,Jae-Hyung Kim,Tae-Won Lee,Chung-Yuen Won 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

In the grid interconnected photovoltaic power generation system including PV-AC module system, the output current have to be sinusoidal synchronized with the grid voltage. Concerning the voltage-controlled current-source modification requirement and the characteristics of flyback topology, boundary or discontinuous conduction mode operations are suitable for the PV-AC module flyback inverter. However, the flyback inverter can be operated in continuous conduction mode (CCM) due to its operating conditions in spite of it is designed to operate under boundary or discontinuous conduction mode. Unfortunately, it causes unintended distortion to output current. In this paper, a current shaping method to reduce the output current distortion for the DCM-flyback inverter is proposed. Even though the flyback inverter operates under CCM, the output current distortion can be reduced by the unfolding H-bridge switching technique.

A Real Maximum Power Point Tracking Method for Mismatching Compensation in PV Array Under Partially Shaded Conditions

Young-Hyok Ji,Doo-Yong Jung,Jun-Gu Kim,Jae-Hyung Kim,Tae-Won Lee,Chung-Yuen Won IEEE 2011 IEEE transactions on power electronics Vol.26 No.4

<P>Conventional popular maximum power point tracking (MPPT) methods are effective under uniform solar irradiance. However, under solar irradiance mismatching conditions [partially shaded conditions (PSCs)], these MPPTs can fail for real MPPT (RMPPT), because multiple local maxima can be exhibited on the power-voltage characteristic curve. Although some researchers have worked on RMPPT under partial shading conditions, the methods have some drawbacks in terms of complexity and requirements for additional circuits, etc. In this paper, a novel MPPT method capable of RMPPT under PSCs is proposed. The performance of the proposed MPPT method is analyzed according to the RMPP position and is verified by simulation and experimental results.</P>

중성선 영상 고조파 전류 저감을 위한 하이브리드 전력 필터

지용혁(Young-Hyok Ji),박상훈(Sang-Hoon Park),김재형(Jae-Hyung Kim),원충연(Chung-Yuen Won),송상훈(Sang-Hoon Song) 전력전자학회 2008 전력전자학술대회 논문집 Vol.- No.-

According to the development of power switching device technology, the power conversion system is used from the small electric power units to the large industrial instruments. These instruments are operated as harmonic sources in the grid and the harmonics cause zero sequence harmonics in the neutral line. To reduce zero sequence harmonics, the zigzag transformer is used conventionally. But the zigzag transformer can reduce only 60∼70% of harmonics. In this paper, hybrid power filter for zero sequence harmonics reduction and the harmonic detection method are proposed.

단일 센서를 사용한 태양광 Module Integrated Converter의 최대전력점 추종 기법

지용혁(Young-Hyok Ji),김영호(Young-Ho Kim),정두용(Doo-Yong Jung),이수원(Su-Won Lee),원충연(Chung-Yuen Won) 한국조명·전기설비학회 2009 한국조명·전기설비학회 학술대회논문집 Vol.2009 No.10월

DMFC를 사용한 전기자전거 배터리 충전장치

김영호(Young-Ho Kim),지용혁(Young-Hyok Ji),김재형(Jae-Hyung Kim),원충연(Chung-Yuen Won),김영렬(Young-Real Kim) 한국조명·전기설비학회 2008 한국조명·전기설비학회 학술대회논문집 Vol.2008 No.5월

In this paper, the battery charging device using DMFC(Direct Methanol Fuel Cell) for electric bicycle is proposed. In the proposed system, phase-shift full-bridge converter is used as a battery charger by boosting the 12V DMFC output voltage up to 36V. By using the phase-shift technique, the ringing of the transformer is reduced and the efficiency of the converter can be improved. The operation modes of proposed phase-shift full-bridge converter is analyzed and verified by the simulation and the experimental results.

직류가선전압 모의장치를 적용한 지하철용 회생인버터 시스템

지용혁(Ji Young-Hyok),조기현(Cho Ki-Hyun),장수진(Jang Su-Jin),원충연(Won Chung-Yuen),김용기(Kim Yong-Ki) 한국철도학회 2007 한국철도학회 학술발표대회논문집 Vol.- No.-

In this paper, a unified regenerative inverter system for railway with DC line voltage simulator is proposed. In order to determine the operation characteristics of the regenerative inverter, the DC line voltage simulator is proposed. The DC line voltage simulator, which is based on the AC-DC PWM converter, varies the DC voltage according to the fluctuating voltage which is measured in the actual DC line. The suitable operating point of the regenerative inverter can be estimated from the simulation result. The regenerative inverter operates two modes. When the DC line voltage exceed the operating point, already set up, it works as regenerative inverter to return the excessive power of DC line to the grid. When the DC line voltage is under the operating point, it works as active power filter to compensate harmonic currents. In this paper, the control algorithm of the DC line voltage simulator and that of the regenerative inverter is proposed.

건강 검진자에서의 미란성 및 비미란성 위식도역류질환의 임상적 특성 및 위험인자

김현영 ( Hyun Young Kim ),김나영 ( Na Young Kim ),김선미 ( Sun Mi Kim ),서지현 ( Ji Hyun Seo ),박영수 ( Young Soo Park ),황진혁 ( Jin Hyok Hwang ),김진욱 ( Jin Wook Kim ),정숙향 ( Sook Hyang Jung ),이동호 ( Dong Ho Lee ) 대한내과학회 2006 대한내과학회지 Vol.71 No.5

목적: 우리나라에서 미란성 위식도역류와 비미란성 위식도역류에 대한 전향적인 조사연구는 거의 없었다. 본 연구는 건강검진자에서의 미란성 위식도역류와 비미란성 위식도역류 유병률을 알아보고 이에 대한 위험요인과 임상 특성에 대해서 알아보고자 하였다. 방법: 2005년 1월부터 5월까지 분당서울대학교병원 건강증진센터를 방문한 수진자 752명을 대상으로 위내시경 및 위식도역류 증상설문지를 시행하였다. 위식도역류질환의 위험요인들은 각각 성별, 흡연, 알콜, 운동, 체질량지수, 콜레스테롤, 공복혈당, 중성지방과 H. pylori IgG에 대해서 로지스틱 회귀 분석을 시행하였다. 비미란성 위식도역류 진단은 가슴쓰림 그리고/또는 산역류 증상이 일주일에 1회 이상 있는 경우 내지 내시경적 미세변화로 정의하였다. 미란성 위식도역류는 미세변화를 제외한 LA 분류법을 기준으로 하였다. 결과: 1) 752명을 세 군으로 나누어보면, 미란성 위식도역류군이 65명(8.6%), 비미란성 위식도역류군이 66명(8.8%), 정상군 621명(82.6%)으로 위식도역류질환 유병률은 17.4%였다. 2) 65명의 미란성 위식도역류군에서 일주일에 1회 이상의 가슴쓰림 그리고/또는 산 역류 증상이 있었던 경우가 19명(29.2%), 역류증상 빈도가 낮거나 비전형적인 역류증상이 있었던 경우가 38명(58.5%), 무증상인 경우가 8명(12.3%)이었다. 3) 65명의 미란성 위식도역류군에서 LA 분류법에 기초로 해서 A도가 48명(73.8%), B도가 11명(17%), C도가 6명(9.2%)이었는데 각 군에서 증상과 역류 증상 정도는 상관관계가 없었다. 4) 정상군과 비미란성 위식도역류질환에서 H. pylori 혈청학적 유병률은 65.3%, 60%로 차이가 없는 반면 미란성 위식도역류질환에서는 36.4%로 의미있게 낮아(p<0.0001) H. pylori 감염 음성일 때 미란성 위식도역류가 발생할 상대적 위험도는 5.079배(95% 신뢰도구간: 1.907-13.530)이었다. 6) 단변량분석에서 남자에서 역류성 식도염이 발병률이 높은 반면 여자에서는 비미란성 위식도역류질환 발병률이 높았고, 그 외 나이, 흡연, 알콜, 체질량지수, 콜레스테롤, 공복혈당, 중성지방은 의미있는 차이가 없었다. 결론: 이상의 결과에서 볼 때 우리나라 건강검진자에서의 위식도역류질환 유병률은 19.3%였고, 미란성 식도염 정도와 역류 증상은 일치하지 않았으며 미란성 위식도역류질환은 H. pylori 감염군에서 의미있게 낮았다. Background: This study was prospectively performed to evaluate the clinical spectrum and risk factors of gastroesophageal reflux disease (GERD) in health check-up subjects. Methods: A prospective survey was performed for 752 subjects, aged 18-79 years, who visited the health promotion center. The subjects were asked to complete a questionnaire, and the risk of GERD was calculated by logistic regression analysis with regard to several variables, including smoking, alcohol, exercise, body mass index, fasting glucose, cholesterol, triglyceride and anti-H. pylori immunoglobulin G (IgG). Non-erosive reflux disease (NERD) was defined as the presence of heartburn and/or acid regurgitation for at least once per week. Results: 752 subjects were classified into three groups: 65 erosive reflux disease (ERD) subjects (8.6%), 66 NERD subjects (8.8%) and 621 control group subjects (82.6%). For the 65 ERD subjects, typical reflux symptoms were found in 19 (29.2%), less frequent reflux or atypical symptoms were found in 38 (58.5%) and no symptoms were found in 8 (12.3%). A Los Angeles grade A score was noted in 48 subjects (73.8%), a B score was noted in 11 (17.0%), and a C score was noted in 6 (9.2%). There was no correlation between the grade of reflux esophagitis and the severity of symptoms. The positive rate of H. pylori IgG in the ERD was 36.4%, and this was significantly lower than the rates for the NERD (60%) and control groups (65.3%); this resulted in the odds ratio of ERD in the absence of H. pylori infection to be 5.079 (95% CI: 1.907-13.530). Conclusions: The prevalence rate of GERD in health check-up subjects was 17.4%. There was no correlation between the grade of ERD and the severity of the reflux symptoms. The relative risk of GERD in Koreans was significantly low in the H. pylori IgG positive subjects.(Korean J Med 71:491-500, 2006)

A New Control Strategy of Active Clamped Flyback Inverter for a Photovoltaic AC Module System

Young-Ho Kim,Jun-Gu Kim,Young-Hyok Ji,Chung-Yuen Won,Tae-Won Lee 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

In this paper, a new control strategy of an active clamped flyback inverter for a photovoltaic AC module system is proposed. In the flyback inverter, a voltage spike across a main switch is generated from a resonance between a leakage inductance and an output capacitance across the main switch. For reducing the voltage spike of the main switch, a snubber circuit is used. In case of the active clamp technique, the circuit has a conduction loss, switching loss and gate drive loss because the switch is turned on and off with a hard switching. Therefore, a consideration reducing the losses of the active clamp circuit is required. If the new control strategy is used, the active clamp switch is not operated during a low voltage in an utility line period. Therefore, the losses of the active clamp circuit can be reduced. In order to verify these, theoretical analysis and simulations are performed.

항문주위 괴사근막염 수술 후 발생한 두덩결합 골수염의 경험

김지연,김태형,추은주,전민혁,이은정,김종화,박의주,이재철,진소영 대한감염학회 2009 감염과 화학요법 Vol.41 No.3

Osteomyelitis of the pubic symphysis is not common and has often been reported to occur after urological or gynecological procedures, It can be spontaneous in origin but it also is associated with trauma, athletic exertion, pregnancy, and parturition. The early symptoms of osteomyelitis of the pubic symphysis mimic those of osteitis pubis and therefore, the differential diagnosis between these two entities is of clinical importance. A fifty nine-year-old man who had previously received debridement and wide excision of perianal necrotizing fasciitis visited our hospital with pain on both inguinal areas. The core biopsy of the pubic symphysis and aspiration culture were performed, from which Pseudomonas aeruginosa was recovered. He was treated with parenteral ceftazidime for 5 days followed by cefepime for 7 weeks and showed favorable clinical response. To our knowledge this is the first report on osteomyelitis of pubic symphysis resulting from debridement and wide excision of perianal necrotizing fasciitis in Korea.

Development of PCR and TaqMan PCR Assays to Detect Pseudomonas coronafaciens, a Causal Agent of Halo Blight of Oats

An, Ji-Hye,Noh, Young-Hee,Kim, Yong-Eon,Lee, Hyok-In,Cha, Jae-Soon The Korean Society of Plant Pathology 2015 Plant Pathology Journal Vol.31 No.1

Pseudomonas coronafaciens causes halo blight on oats and is a plant quarantine bacterium in many countries, including the Republic of Korea. Using of the certificated seed is important for control of the disease. Since effective detection method of P. coronafaciens is not available yet, PCR and TaqMan PCR assays for specific detection of P. coronafaciens were developed in this study. PCR primers were designed from the draft genome sequence of P. coronafaciens LMG 5060 which was obtained by the next-generation sequencing in this study. The PCR primer set Pc-12-F/Pc-12-R specifically amplified 498 bp from the 13 strains of P. coronafaciens isolated in the seven different countries (Canada, Japan, United Kingdom, Zimbabwe, Kenya, Germany, and New Zealand) and the nested primer set Pc-12-ne-F/Pc-12-ne-R specifically amplified 298 bp from those strains. The target-size PCR product was not amplified from the non-target bacteria with the PCR and nested primer sets. TaqMan PCR with Pc-12-ne-F/Pc-12-ne-R and a TaqMan probe, Pc-taqman, which were designed inside of the nested PCR amplicon, generated Ct values which in a dose-dependent manner to the amount of the target DNA and the Ct values of all the P. coronafaciens strains were above the threshold Ct value for positive detection. The TaqMan PCR generated positive Ct values from the seed extracts of the artificially inoculated oat seeds above 10 cfu/ml inoculation level. PCR and TaqMan PCR assays developed in this study will be useful tools to detect and identify the plant quarantine pathogen, P. coronafaciens.