• 대한기계학회논문집A
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• 제26권6호
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• pp.1060-1068
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• 2002

Compound continuously variable transmission(CVT) mechanisms are proposed, which can offer a backward mode, a geared neutral, an underdrive mode and an overdrive mode. They are composed of a 2K-H I type differential gear unit, a V-belt type continuously variable unit(CVU), a few friction clutches and gears, and not required of a starting device as a torque converter. Compound CVT mechanisms developed here present two distinct operating modes which are a power circulation mode and a power split mode. The transition of two modes takes place at the particular CVU speed ratio. For these CVT mechanisms, performance analysis related to speed ratio, power ratio and efficiency are executed and proven by experimental studies.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.739-742
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• 1997

Continuously variable transmission(CVT) mechanisms are proposed, which can offer a backward mode, a geared neutral, an underdrive mode and an overdriver mode. They are not required of a starting device as a torque converter. CVT mechanisms developed here present two distinct operating modes which are a power circulation mode and a power split mode. The transition of two modes takes place at the particular CVU speed ratio. For these CVT mechanisms, performance analysis related to speed ratio, power ratio and theoretical efficiency are executed.

• 전력전자학회논문지
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• 제21권4호
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• pp.364-372
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• 2016

In this paper, a voltage controller for the seamless transition of a grid-connected inverter for ESS is proposed. The single-phase inverter is operated as a current controller when the grid is connected and as a voltage controller in the stand-alone mode when the grid is disconnected. Generally, in the case of grid recovery, the overcurrent may flow into the system because of the mismatch phase between the inverter output and grid voltages. The proposed controller resolves the overcurrent problem through phase delay problems with initial value feed-forward control of the integrator when the grid voltage is restored. The effects of the control method are simulated through PSIM, and the usefulness of the control method is verified through experiments.

• 전력전자학회논문지
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• 제9권1호
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• pp.10-16
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• 2004

본 논문에서는 공진 에너지 회생율을 최대화하여 전체적인 효율을 증가시킨 개선된 전파형 ZVT(Zero-Voltage-Transition) PWM(Pulse-Width-Modulation) DC-DC 컨버터를 소개한다. 개선된 회로는 단지 기존 컨버터의 보조스위치와 공진형 인덕터 사이에 직렬로 역공진 저지 다이오드를 추가로 달아서 모든 스위칭 소자들이 소프트 스위칭 조건에서 턴온/턴오프하여 스위칭 손실을 최소화하고, 공진 에너지를 완전히 입력으로 회귀시켜 전도손실을 절감하여 효율의 증감을 이루었다. 본 논문에서는 부스터 컨버터를 이용하여 개선된 컨버터의 동작을 분석하고, 실험결과를 바탕으로 제안된 회로의 타당성을 입증하였다.

• 전력전자학회논문지
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• 제25권5호
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• pp.333-342
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• 2020

Power exchanges between the grid and the battery through a bidirectional DC-DC converter are essential for DC microgrid systems. In general, the battery is charged when the grid is connected, and the system is powered by the battery when the grid is disconnected. In this mode transition, the saturation of the voltage controller slows down output response and produces large transient errors in DC link voltage. To solve this problem, a novel anti-windup design is proposed to improve anti-windup performance further. The proposed method stabilizes DC bus voltage through a wider range of battery voltage with faster transition compared with that of conventional methods. The proposed method is verified through an experimental setup composed of a 125 W laboratory-scale DC microgrid system.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2008년도 하계학술대회 논문집
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• pp.18-20
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• 2008

An electrical balance of plant(EBOP) of a 600kW molten carbonate fuelcell (MCFC) has to transit from grid-connected(GC) mode to grid-independent(GI) mode when a grid is in a fault conditions. A minimum transition time is limited by four cycle for a 600kW MCFC to ride through a grid fault. In this paper, we propose a control algorithm of a 600kW EBOP for a MCFC system. The EBOP has three operation modes, i.e., GC mode, GI mode, and grid-synchronized(GS) mode. The EBOP controls output currents in a GC mode and regulates output voltages in GI or GS mode. GS mode is defined as an interface between GC mode and GI mode to make a mode transition smooth, i.e., limitation of inrush currents, regulation of output voltages within ANSI standard. Simulations and experiments carried out to verify the effectiveness of the proposed control algorithm.

• Journal of Power Electronics
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• 제8권1호
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• pp.35-50
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• 2008

A zero-voltage-transition (ZVT) pulse width modulated (PWM) converter is a PWM converter with a single main power switch that has an auxiliary circuit to help it turn on with zero-voltage switching (ZVS). There have been many ZVT-PWM converters proposed in the literature as they are the most popular type of ZVS-PWM converters. In this paper, the properties and characteristics of several types of ZVT-PWM converters are reviewed. A new type of ZVT-PWM converter is then introduced, and the operation of a sample converter of this type is explained and analyzed in detail. A procedure for the design of the converter is presented and demonstrated experimentally. The feasibility of the new converter is confirmed with results obtained from an experimental prototype. Conclusions on the performance of ZVT-PWM converters in general are made based on the efficiency results obtained from the experimental prototypes of various ZVT-PWM converters of different types.

• 정보통신설비학회논문지
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• 제9권4호
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• pp.124-130
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• 2010

This paper considers a power saving technique of set-top box (STB) that turns the signal into content which is then displayed on the television (TV) screen. A traditional power saving scheme, Auto Power Down (APD), was devised to reduce the power consumption of STB. APD checks whether the user is watching TV over a period of time and enforces STB into stand-by mode when the check result reveals the user is not watching TV. This paper proposes an enhanced power saving scheme that transits STB operation mode to 'stand-by' immediately when STB recognizes the change of TV's external input signal. The proposed scheme does not require the monitoring time to check the users' watching TV, and transits to standby mode faster than the conventional APD, which results in better performance in power saving. The simulation result shows that the proposed scheme achieves 2 to 11% improvement in power consumption compared with the conventional APD.

• Journal of electromagnetic engineering and science
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• 제17권1호
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• pp.9-13
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• 2017

In this work, a broadband composite right/left-handed (CRLH) half-mode substrate integrated waveguide (HMSIW) quadrature Wilkinson power divider is proposed. The proposed CRLH-HMSIW quadrature power divider includes a microstrip Wilkinson power divider on the transition structure between the microstrip and HMSIW, and two thru transmission lines for the HMSIW and the CRLH-HMSIW. The measured amplitude, phase difference and isolation between the two output ports of the proposed structure have 1 dB, ${\pm}5^{\circ}$ and less than -15 dB in a wide frequency range of 4.1-6.68 GHz with 47.9% bandwidth, respectively.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1495-1505
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• 2002

As combining the functions of a 2K-H B type differential gear unit and a V-belt type continuously variable unit(CVU), 16 different mechanisms are presented. Some useful theoretical formula related to speed ratio, power flow and efficiency are derived and analyzed. Continuously variable transmission(CVT) mechanisms are proposed, which can of ffr a backward mode, a geared neutral, an underdrive mode and an overdrive mode. They are not required of a starting device as a torque converter. CVT mechanisms developed here present two distinct operating modes which are a power circulation mode and a power split mode. The transition of two modes takes place at the particular CVU speed ratio. For these CVT mechanisms, performance analysis related to speed ratio, power ratio and theoretical efficiency are executed.