• 전기학회논문지
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• 제56권4호
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• pp.651-659
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• 2007

This paper proposes an improved fault indication algorithm in a distribution automation system. A conventional fault indication method, so called YES-NO algorithm, could generate wrong informations under certain conditions such as line to ground fault, large motor double circuit line. In order to prevent mal-operation of fault indicator, direction of fault current are used as well as magnitude. The feasibility of the proposed algorithm has been testified by computer simulation using Matlab power system toolbox.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 추계학술대회 논문집
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• pp.107-108
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• 2012

This paper presents design and implementation of the LDC(1.8 kW DC-DC Converter for Electric Vehicles). For Implementation of the LDC, the adapted topology is ZVS(Zero Voltage Switching) PSFB(Phase Shift Full Bridge) with Digital Control is adopted. Also, for the purpose of stable operation of the LDC in vehicle with variable electrical load condition, Continuous Voltage and Current Limit Control scheme based on PI controller are developed. According to real-car test mode, the prototype of proposed the LDC is verified with performance and stability. Thus, optimizing design and implement of the LDC are discussed, and experimental results are presented.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 추계학술대회 논문집
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• pp.201-202
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• 2012

This paper presents design and implementation of the PCU(150 kVA 3-Phase PWM Inverter for Electric Vehicles). For Implementation of the PCU, it is consist with Case, Connectors, IGBT module for PWM switching, DC-capacitor for dc-source, resolver for sensing of speed & position, and PCB board for control & gate-driver. Also, for the purpose of stable operation of the PCU in vehicle with variable torque condition in motor, current control scheme based on torque-map are developed. According to real-car test mode, the prototype of proposed the PCU is verified with performance and stability. Thus, design and implement of the PCU are discussed, and experimental results are presented in this paper.

• 대한전기학회논문지:전력기술부문A
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• 제53권2호
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• pp.80-86
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• 2004

During magnetic inrush or over-excitation, saturation of the core in a transformer draws a large exciting current, which can cause mal-operation of a differential relay. This paper proposes a modified current differential relay for transformer protection. The relay calculates core-loss current from the induced voltage and the core-loss resistance; the relay calculates the magnetizing current from the core flux and the magnetization curve. Finally, the relay obtains the modified differential current by subtracting the core-loss and the magnetizing currents from the conventional differential current. Comparison study with the conventional differential relay with harmonic blocking is also shown. The proposed technique not only discriminates magnetic inrush and over-excitation from an internal fault, but also improves the speed of the conventional relay.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.356-358
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• 2001

Voltage sags are known as a serious problem causing mal-operation of equipment, process controllers and adjustable-speed drives. We understand problems of the voltage sag that have a bad effect to the load and then we design for a new model of the compensator. We accomplished system modeling for both sensorless part and sensing part, and compare the merits and demerits of both.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.371-375
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• 2009

The distribution control of refrigerant flow is one of the basic technique to enhance system efficiency. However, if engineers forget to control the refrigerant flow speed in all operation range, refrigerant flow mal distribution becomes a noise source. The refrigerant flow noise should be checked and controlled at the lowest air flow mode which is the most silent mode and frequently used in night time.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.195-196
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• 2008

Output of wind generators are changed by windy level. The change of the output also affects the amplitude of fault current. And this fault current causes OCR's mal-operation. To solve the problem, this paper adopts that Over Current Relay adapted for Decentralized generator algorithm.

• 품질경영학회지
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• 제38권2호
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• pp.202-211
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• 2010

Many Asian countries operate the national quality award systems. Most of the evaluation criteria of the award systems are generally based on the MalCom Baldrige National Quality Award System of U.S.A. which started since 1987. But their operation systems for awards are different by countries. Comparing the differences among them can give a good benchmark for Korean Quality Award systems. There are poor empirical results that the Korean Quality Awards systems improve the performances of the organizations awarded. This paper proposes some suggestions for the effective operations of Korean quality award systems through the comparison among Asian countries' awarding systems.

• KIEE International Transactions on Power Engineering
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• 제4A권3호
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• pp.122-128
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• 2004

With the advent of distributed generation, power systems are fundamentally impacted in regards to stability and power quality. Distributed generation has a positive impact on system restoration following a fault, higher reliability, and mitigation of effect due to voltage sag. However, distributed generation also has a negative impact on decrease of reliability such as changes of protective device setting and mal-operation. Because bulk power systems consist of various sources and loads, it becomes complicated to analyze a power system with distributed generation. The types of distributed generation are usually classified by both rotating machinery and the inverter-based system. In this paper, distributed generation is designed by rotating machinery, and the distributed system having a model of the distributed generation is simulated using EMTP. In addition, this paper presents the simulation results according to the types of distributed generation.

• KIEE International Transactions on Power Engineering
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• 제4A권4호
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• pp.201-206
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• 2004

With the advent of distributed generation, power systems in general are impacted in regards to stability and power quality. Distributed generation has positive impacts on system restoration following a fault, higher reliability, and mitigation of effect due to voltage sag. However, distributed generation also has negative impacts on the decrease of reliability such as changes of protective device setting and mal-operation. Because bulk power systems consist of various sources and loads, it is complicated to analyze power systems that have distributed generation. The types of distributed generation usually are classified as the rotating machinery system and the inverter-based system. In this paper, distributed generation is designed as a synchronous generator, and the distribution system with its distributed generation model is simulated using EMTP. In addition, this paper shows the simulation results according to the types of distributed generation