• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.586-594
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• 2015

This paper proposes a maximum efficiency operation strategy for three-level T-type inverter in entire operation areas. The three-level T-type inverter has higher and lower efficiency areas compared with two-level inverter. The proposed strategy aims to operate in the maximum efficiency point for the low-voltage and low-power home appliances. The three-level T-type inverter is analyzed in detail, and the two operation mode selection strategy is developed. The proposed algorithm is verified by theoretical analysis and experimental results.

• Journal of Electrical Engineering and Technology
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• 제3권1호
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• pp.29-35
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• 2008

With long time setting, zone 3 impedance relays are considered insensitive to power swings, and their operation condition during power swings is seldom analyzed. Instead of ti me-consuming simulation to the swing loci, their operation condition is directly quantified by polynominal functions in this paper to find the critical swing angle and frequency for relay operation under different relay settings and system parameters. It is found: (1) the swing loci are more densely populated inside than outside of the protection region, which corresponds to long residence time and possible relay operations; (2) the relays may be sensitive to load encroac hments and stable power swings with different relay settings and system parameters; (3) the critical swing frequency may be in the range of low-frequency power swings.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1383-1386
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• 2005

Non-isolated OSAKA Converter, which removes a three-phase transformer, is described in this paper. The converter switches once in every half cycle of an AC commercial power source. Therefore, it can solve many problems caused by the high frequency operation. The proposed converter achieves the soft-switching operation and the EMI noise can be reduced. In this circuit, the resonant capacitor, which is used for the soft-switching operation, is utilized for the improvement of an input current waveform. To achieve low cost and compact structure, non-isolated OSAKA converter removes a three-phase transformer of the OSAKA converter. By removing the three-phase transformer, three phase currents occur the interferences each other. To avoid the interference, a new switching method for non-isolated OSAKA converter is preposed. The converter can be constructed by the low-speed large power devices. The converter generates the low distorted input current waveforms with high power factor.

• 전기학회논문지
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• 제58권1호
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• pp.199-202
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• 2009

Scan design is currently the most widely used structured Design For Testability approach. In scan design, all storage elements are replaced with scan cells, which are then configured as one or more shift registers(also called scan chains) during the shift operation. As a result, all inputs to the combinational logic, including those driven by scan cells, can be controlled and all outputs from the combinational logic, including those driving scan cells, can be observed. The scan inserted design, called scan design, is operated in three modes: normal mode, shift mode, and capture mode. Circuit operations with associated clock cycles conducted in these three modes are referred to as normal operation, shift operation, and capture operation, respectively. In spite of these, scan design methodology has defects. They are power dissipation problem and test time during test application. We propose a new methodology about scan shift clock operation and present low power scan design and short test time.

• 전기전자학회논문지
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• 제22권3호
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• pp.548-557
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• 2018

In this paper, Asynchronous Self-Power Gating technique (ASPG) is used to reduce consumption power in asynchronous digital watch application. The power gating control signal is automatically generated by internal system operation characteristics instead of using replica circuit delay or four-phase handshaking protocol. Isolation cell is designed to insert it between power gating domain and normal operation domain. By using self-power gating circuit, asynchronous digital watch application consumes very low power and maintains data during sleep mode. The comparison results show the proposed ASPG technique saves leakage power up to 40.47% and delay time is reduced to 71% compared to the conventional circuit.

• 한국정보통신학회논문지
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• 제18권8호
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• pp.1877-1884
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• 2014

원격 무선 네트워크 환경에서의 무인 센서 신호처리기의 임무 수행을 위해서는 한정된 전력 자원으로 인해 무인 원격 센서 무선운용 상황에 적합한 신뢰성 있는 저전력 매체 접속 제어 기법이 요구된다. 저전력 무선 네트워크에서 효과적인 신호 전송을 위해서는 CSMA/CA, X-MAC을 일반적으로 고려한다. 본 논문에서는 고정 노드로 구성되는 무선 네트워크에서 노드 제어를 위한 이동 노드의 망 참여/탈퇴가 유동적인 망 형태에서의 신속한 데이터 전달 및 소모 전력 최소화 달성이 가능한 저전력 성능이 향상된 LP-MAC 동작 기법을 제안한다. 고정노드는 망 자율구성을 수행하여 망에 수시로 참여/탈퇴하는 이동 노드로의 빠른 정보 전달을 위해 비동기 방식으로 동작한다. 이동 노드가 망에서 탈퇴할 경우, 망 전체 운용모드가 소모 전력의 최소화를 위한 동기모드로 천이됨으로써 최소 전력 운용이 가능한 매체접속 제어 기법이다.

• 전기학회논문지P
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• 제55권1호
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• pp.35-40
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• 2006

Heat-pump system has a special feature that provides heating operation in winter season and cooling operation in summer season with a single system. It also has a merit that absorbs and makes use of wastewater heat, terrestrial heat, and heat energy from the air. Because heat-pump system uses midnight electric power, it decreases power peak load and is very economical as a result. By using the property that energy source is converted to low temperature when losing the heat, high temperature energy source is used to provide heating water and low temperature energy source is used to provide cooling water simultaneously in summer season. This study made up a heat-pump system with 4 air heat sources and a water heat source and implemented the optimal operation algorithm that works with numbers of heat pumps to operate them efficiently. With the heat-pump system, we applied it to cooling and heating operation in summer season operation mode in a real building.

• Journal of Power Electronics
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• 제8권1호
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• pp.51-59
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• 2008

This paper addresses several issues concerning the analysis, design, modeling, simulation and development of single-phase, single-switch, power factor corrected AC-DC high frequency switching converter topologies with transformer isolation. A detailed analysis and design is presented for single-switch topologies, namely forward buck, flyback, Cuk, Sepic and Zeta buck-boost converters, with high frequency isolation for discontinuous conduction modes (DCM) of operation. With an awareness of modem design trends towards improved performance, these switching converters are designed for low power rating and low output voltage, typically 20.25W with 13.5V in DCM operation. Laboratory prototypes of the proposed single-switch converters in DCM operation are developed and test results are presented to validate the proposed design and developed model of the system.

• 한국압력기기공학회 논문집
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• 제15권1호
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• pp.33-39
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• 2019

An 1,500MW advanced power reactor required the standard design approval by a Korean regulatory body in 2014. The reactor has been designed to have a 4-train independent safety concept and a passive auxiliary feedwater system (PAFS). The full power risk or core damage frequency (CDF) of 1,500MW advanced power reactor has been reduced more than that of APR1400. However, the risk during the low power and shutdown (LPSD) operation should be reduced because CDF of LPSD is about 4.7 times higher than that of internal full power. The purpose of paper is to analysis design alternatives to reduce risk during the LPSD. This paper suggests design alternatives to reduce risk and presents sensitivity analysis results.

• Nuclear Engineering and Technology
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• 제34권5호
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• pp.502-516
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• 2002

Wolsong NPP are CANDU6 type reactors and there are 4 CANDU6 type reactors in commercial operation. CANDU type reactors require on-power refuelling by two remote controlled F/Ms (Fuelling Machines). Most of channels, fuel bundles are float by channel coolant flow and move toward downstream, however in about 30% of channels the coolant flow are not sufficient enough to carry fuel bundles to downstream. For those channels a special device, FARE (Flow Assist Ram Extension) device, is used to create additional force to push fuel bundles. It has been showing that during fuelling operation of some channels the channel coolant flow rate is reduced below specified limit (80% of normal), and consequently trip alarm signal turns on. This phenomenon occurs on selected channels that are instrumented for the channel flow and required to use the FARE device for refuelling. Hence it is believed that the FARE device causes the problem. It is also suspected that other channels that do not use the FARE device for refuelling might also go into channel flow low state. The analysis revealed that the channel How low occurs as the FARE device is introduced into the core and disappears as the FARE device is removed from the core. This paper presented the FARE device behavior, detailed fuelling operation sequence with the FARE device and effect on channel flow low phenomena. The FARE device components design changes are also suggested, such as increasing the number or now holes in the tube and flow slots in the ring orifice.