• Transactions of the Korean hydrogen and new energy society
• /
• 제24권1호
• /
• pp.12-19
• /
• 2013

A gasification process with pre-combustion $CO_2$ capture process, which converts coal into environment-friendly synthetic gas, might be promising option for sustainable energy conversion. In the coal gasification for power generation, coal is converted into $H_2$, CO and $CO_2$. To reduce the cost of $CO_2$ capture and to maximize hydrogen production, the removal of CO and the additional production of hydrogen might be needed. In this study, a 2l/min water gas shift system for a coal gasifier has been studied. To control the concentration of major components such as $H_2$, CO, and $CO_2$, MFCs were used in experimental apparatus. The gas concentration in these experiments was equal with syngas concentration from dry coal gasifiers ($H_2$: 25-35, CO: 60-65, $CO_2$: 5-15 vol%). The operation conditions of the WGS system were $200-400^{\circ}C$, 1-10bar. Steam/Carbon ratios were between 2.0 and 5.0. The commercial catalysts were used in the high temperature shift reactor and the low temperature shift reactor. As steam/carbon ratio increased, the conversion (1-$CO_{out}/CO_{in}$) increased from 93% to 97% at the condition of CO: 65, $H_2$: 30, $CO_2$: 5%. However the conversion decreased with increasing of gas flow and temperature. The gas concentration from LTS was $H_2$: 54.7-60.0, $CO_2$: 38.8-44.9, CO: 0.3-1%.

• Proceedings of the KIPE Conference
• /
• 전력전자학회 2016년도 추계학술대회 논문집
• /
• pp.9-10
• /
• 2016

최근 급속한 산업 발달로 인하여 기존의 수 MW급 대용량 인버터가 산업용 팬, 컴프레서, 고속 철도 시스템 등 여러 분야에 사용되면서 이와 관련된 대용량 인버터 연구가 활발히 진행 중이다. 이런 대용량 인버터는 고효율과 직병렬의 구성된 전력용반도체 소자를 동시다발적으로 제어되어야하기 때문에 멀티레벨 인버터의 구조가 가장 적합하다. Cascaded H-bridge 멀티레벨 인버터는 커패시터와 다이오드를 사용하지 않고 스위치만으로 구성하며, 필터를 따로 구성하지 않아도 정현파와 유사하게 전압을 출력할 수 있다. 이로 인해 고주파 감소 및 각 셀을 직렬로 연결하여 입력전압보다 높은 출력전압을 얻을 수 있다. 또한, 스위칭 방법에 따라 동일한 Cascaded H-bridge 멀티레벨인버터 토폴로지에서도 각 THD와 온도에 따른 손실이 달라질 수 있다. Cascaded H-bridge 멀티레벨 인버터에서 이용하는 스위칭 방식은 첫 번째로 유니폴라 방식을 기본으로 한 Phase-shift가 있다. 이는 180도 위상차를 갖는 2개의 레퍼런스 파형과 위상천이가 된 캐리어 파형의 비교로 PWM (Pulse Width Modulation) 을 수행한다. 두 번째 방식으로는 Level-shift가 있다. 이는 캐리어 파형을 IPD (In-Phase Disposition) 방식으로 수직적으로 대역폭이 연속적이게 나열하여 레퍼런스 파형과 비교하는 PWM방식이다. 본 논문에서는 Phase-shift와 Level-shift 방식에 따른 Cascaded H-bridge 인버터와 NPC (Neutral Point Clamped) 인버터를 결합한 토폴로지에서의 온도에 따른 손실을 분석하고, 시뮬레이션을 통하여 비교 분석하였다.

• The Journal of the Acoustical Society of Korea
• /
• 제41권2호
• /
• pp.159-165
• /
• 2022

In this paper, a frame synchronization structure for the Binary Phase Shift Keying (BPSK) modulation method in underwater acoustic communication was proposed. The proposed frame synchronization structure is largely divided into two. First, the approximate position and frequency offset of the frame are obtained by non-coherent correlation and sliding Fast Fourier Transform (FFT) method. Second, after compensating for the frequency error to the received signal, the exact position of the frame is obtained by coherent correlation method. Maritime experiments were conducted to confirm the performance of the 2-STEP frame synchronization structure. It was showed that the limitations of the non-coherent correlation and sliding FFT method can be verified when the power of the received signal was greatly reduced due to the channel characteristics. As a result, stable frame synchronization could be obtained by compensating for the frequency error and then using the coherent correlation method.

• Journal of the Korean Society of Costume
• /
• 제56권5호
• /
• pp.89-104
• /
• 2006

The purpose of this study is to explain how a power group in a society forms features of sexuality in dress. As for the research methodology, first, historical research was undertaken to study in socioeconomic context in which sexuality has been formed and transformed. Second, demonstrative studies on sexual-image styles were undertaken through the analysis of pictures and photos. Third, analysis of the relationship between the power and sexuality in dress was done by literature research. Masculinity in dress, such as simplicity and concealment, corresponds to the attributes of the viewer, and femininity in dress, such as decoration and exposure, corresponds to the attributes of the viewee. Power struggle is the complex process of forming of the viewer-viewee relationship. The one who grasps the power becomes the viewer. In the shift from the Industrial Society to the Information and Technology Society, powers are horizontally spread over the society and the stereotype of sexuality in both women's and men's dress is fading out. In the field of design, standards and certainty described by absolute power are losing their importance. The 'chaotic' view of a world filled with mutual exchange of masculinity and femininity and uncertainty of sexuality will be sure to be a dominant trend in fashion.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• 제24권10호
• /
• pp.2477-2486
• /
• 2000

A planetary gear assembly is a key component to combine and/or split a power from the source. With a planetary gear assembly, a continuously variable unit extends its capacity by means of power bra nching mechanism. Power branching with one planetary gear assembly and one continuously variable unit is categorized into 12 basic types. Each type represents peculiar power transmitting characteristics. Additionally, a multi-mode (range) continuously variable transmission can be designed with accompanying clutches. A multi-mode continuously variable transmission changes the path through which the source power is transmitted. Each path has its own features, such as high efficiency. In this paper, some design principles are examined such as, criteria to guarantee the minimum power efficiency, and constraints to guarantee the smooth mode shift after discussing well-known features of multi-mode M mathematically.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• 제18권3호
• /
• pp.135-141
• /
• 2004

A sterilizer equipment by using electrical energy has metrits that no process of chemical and no second environmental pollution, Also, the power conversion circuit for sterilizer equipment has mertis that are reducing switching loss for soft switching topology by using zero current and zero voltage switching, and miniaturizing size of equipment. The proposed power device which has lower output current than other devices is possible to be compacted in it's size reduced it's price if the proposed power device is used for power system. Therefore, it is adapted for both less power consumption and sudden power conversion

• Journal of Power Electronics
• /
• 제8권4호
• /
• pp.332-344
• /
• 2008

High frequency AC (HFAC) power distribution systems delivering power through a high frequency AC link with sinusoidal voltage have the advantages of simple structure and high efficiency. In a multiple module system, where multiple resonant inverters are paralleled to the high frequency AC bus through connection inductors, it is necessary for the output voltage phase angles of the inverters be controlled so that the circulating current among the inverters be minimized. However, the phase angle of the resonant inverters output voltage can not be controlled with conventional phase shift modulation or pulse width modulation. The phase angle is a function of both the phase of the gating signals and the impedance of the resonant tank. In this paper, we proposed a pulse phase modulation (PPM) concept for the resonant inverters, so that the phase angle of the output voltage can be regulated. The PPM can be used to minimize the circulating current between the resonant inverters. The mechanisms of the phase angle control and the PPM were explained. The small signal model of a PPM controlled half-bridge resonant inverter was analyzed. The concept was verified in a half bridge resonant inverter with a series-parallel resonant tank. An HFAC power distribution system with two resonant inverters connected in parallel to a 500kHz, 28V AC bus was presented to demonstrate the applicability of the concept in a high frequency power distribution system.

• The Transactions of the Korean Institute of Power Electronics
• /
• 제23권5호
• /
• pp.345-351
• /
• 2018

A distributed control method is proposed to improve the power sharing performance of bidirectional distributed generators and the voltage regulation performance of a DC bus in a DC microgrid. Voltage sensitivity analysis based on power flow analysis is conducted to analyze the structural characteristics of a DC microgrid. A distributed control method using a voltage sensitivity matrix is proposed on the basis of this analysis. The proposed method uses information received through the communication system and performs the droop gain variation method and voltage shift method without additional PI controllers. This approach achieves improved power sharing and voltage regulation performance without output transient states. The proposed method is implemented through a laboratory-scaled experimental system consisting of two bidirectional distributed generators, namely, a load and a non-dispatchable distributed generator in a four-bus ring-type model. The experimental results show improved power sharing accuracy and voltage regulation performance.

• Proceedings of the KIPE Conference
• /
• 전력전자학회 2012년도 전력전자학술대회 논문집
• /
• pp.183-184
• /
• 2012

본 논문에서는 출력 인덕터 리플과 2차 측 정류기의 공진 전압을 저감할 수 있는 다중 위상천이 풀 브리지 컨버터를 제안한다. 제안된 회로는 총 8개의 스위치가 사용되며, 각 4개의 스위치가 하나의 위상천이 풀 브리지 인버터 부를 구성하는 구조이다. 기존 위상천이 풀 브리지 컨버터의 경우, 진상레그와 지상레그의 위상차이를 조절하여 출력전압을 제어하는데 반해, 제안된 회로는 진상레그와 지상레그의 위상차이 뿐만 아니라 각 풀 브리지 인버터 부의 위상차이를 동시에 조절하여 출력전압을 제어하는 것이 특징이다. 이를 통하여 제안회로는 출력 인덕터 전류 리플 및 2차 측정류기의 공진 전압을 크게 저감시킬 수 있어 고 효율화에 유리하다. 본 논문에서는 제안된 회로의 이론적 해석 및 PSIM 모의실험을 수행하며, 450W급 시작품을 제작하여 제안회로의 타당성을 검증하였다.

• Current Photovoltaic Research
• /
• 제6권4호
• /
• pp.124-132
• /
• 2018

The Korean electric power supply plan was prepared by greatly enhancing the environmental and safety with considering the economical efficiency of the electric equipment, the impact on the environment and the public safety. As a result, the fossil energy-based power generation sector is accelerating the paradigm shift to eco-friendly energy such as solar power and wind. Also the solar power industry is expected to grow into a super large-sized industry by converging the energy storage and electric vehicle industry. Generally, a levelized cost of electricity (LCOE) is used to calculate the power generation cost for different generation power generation efficiency, operating cost, and life span. In this paper, we have studied the future research and development direction of photovoltaic technology development for the era of massive utilization of photovoltaic solar power, and have studied the LCOE of major countries including China, USA, Germany, Japan and Korea. Finally we have reviewed USA and Japan research programs to reduce the LCOE.