• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.397-402
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• 2001

Due to the recent economic growth and the subsequent increase in demand of electricity, the construction of underground transmission line is also on the rise. Especially, in the metropolitan area, we have much obstruction in laying the line to the central district because of difficulties in procurement of construction land and the increase in the construction cost. Therefore, the necessity of increasing the capacity of transmission line has been suggested. In order to increase the capacity, the electric voltage and current intensity in size-limited lines should be also increased. But, eventually, it leads to the generation of unnecessary heat and the heat radiates through insulation cables and backfill concrete. So we need to develop the material that has good heat radiation characteristics. In this study, we developed and tested backfill concrete that can be a substitute for previously used backfill sand.

• 대한전기학회논문지:전력기술부문A
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• 제54권5호
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• pp.212-216
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• 2005

This paper describes the application scheme of resistive HTS-FCL(High Temperature Superconducting-Fault Current Limiter) on future new distribution system. Future new distribution system means the power system to which applies the 22.9kV HTS cable with low-voltage and mass-capacity characteristics replacing the 154kv conventional cable in addition to HTS transformer and HTS-FCL. The fault current of future new distribution system will increase greatly because of the inherent characteristics of HTS transformer/cable and applications of distributed generations and spot networks and so on. This means that the HTS-FCL is necessary to reduce the fault current below the breaking capacity. This paper studies the appropriate location, parameters and the influences of HTS-FCL on future new distribution system. Finally, this paper suggests the reasonable basic parameters of resistive HTS-FCL for future KEPCO new distribution system.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 추계학술대회 논문집
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• pp.60-62
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• 2007

The open circuit voltage (OCV) is widely used to estimate the state of charge (SOC) in many estimation algorithms. However, the relationship between the OCV and SOC can not be exactly same for all batteries. Because the conventional OCV-SOC differs between batteries, there is a problem that the relationship of the OCV-SOC should be measured to accurately estimate the SOC. Therefore, the conventional OCV-SOC is modified to a new relationship in this paper. Thus, problems resulting from the defects of the extended Kalman filter (EKF) can be avoided by preventing the relationship from varying. In this paper, SOC and capacity of the lithium-ion battery are estimated using the dual EKF with the proposed method.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 춘계학술대회 논문집
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• pp.229-230
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• 2007

We investigated the quench characteristics of a superconducting element, two superconducting elements in order to increase the current capacity of flux lock type SFCL. The flux-lock type SFCL consisted of the transformer with a primary winding and a secondary winding connected in parallel, and the superconducting element was connected with secondary winding in series. The applied voltage at that time was 160 ${\sqrt{3}}$. We found that the parallel connection between the superconducting elements increased the power capacity and let quench characteristics improve through their mutual linkage.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(1)
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• pp.82-86
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• 2004

In this paper, a cycler system for the Lithium-Polymer battery with the large capacity of 120Ah is presented. This system is constituted as the two units for the charging and discharging. The Lithium-Polymer battery should be charged in CC and CV mode, and it is required a very high precision control of the voltage and current for the charging unit. To decrease the switching noises and harmonics, parallel operation method is adopted and utilized in the power conversion module. The discharging unit has a link AC system function to return the discharging energy of battery to AC line and has comparatively less thermal loss. These units are designed to be controlled and monitored by personal computer. The total system for the battery charging and discharging is described and presented.

• 대한전기학회논문지
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• 제41권2호
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• pp.125-134
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• 1992

This paper presents a cycloconverter with an LC resonant circuit for an induction motor drive. The cycloconverter can keep input displacement factor at 1.0 by independently controlling real and reactive power under any load conditions. Furthermore it can keep power factor at about 1.0 since input and output current waveforms are nearly sinusoidal. Since it uses high frequency resonant circuit for commutation source, it can produce an output voltage of hundreds of hertz. Since it is also possible to make a system of high capacity using the cycloconverter, it is appropriate to drive motors with high speed and high capacity as well as general purpose motors, In this paper, we describe the operating principles of the cycloconverter and power control algorithms, and analyze its waveforms and present its characteristics. Expermental results are shown for the volts/hertz control of the induction motor and the validity of the proposed model is verified.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.522-524
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• 2000

The installation of small sized Embedded Generator(EG) in parallel with the utility supply was required several technical complications for protection of the system. One of the most important protection is to provide protection against islanding and out of synchronism reclosing with the utility source. This paper explains several current methods of detecting 'Loss Of Mains'(LOM). But they have not proved completely dependable, in particular when the islanded load's capacity matches that of the EG. A new loss of mains protection algorithm is presented in this paper which based on measurement of the reactive power and node voltage for detecting the islanding condition even though the EG operate in the capacity.

• ETRI Journal
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• 제25권5호
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• pp.412-417
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• 2003

Using a galvanostatic charge/discharge cycler and cyclic voltammetry, we investigated for the first time the electrochemical properties of iron-containing minerals, such as chalcophanite, diadochite, schwertmannite, laihuite, and tinticite, as electrode materials for lithium secondary batteries. Lithium insertion into the mineral diadochite showed a first discharge capacity of about 126 mAh/g at an average voltage of 3.0 V vs. $Li/Li^+$, accompanied by a reversible capacity of 110 mAh/g at the 60th cycle. When the cutoff potential was down to 1.25 V, the iron was further reduced, giving rise to a new plateau at 1.3 V. Although the others showed discharge plateaus at low potentials of less than 1.6 V, these results give an important clue for the development of new electrode materials.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 연구회 합동 학술발표회 논문집
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• pp.5-8
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• 1998

The adaptation to vector control theory is so generalized that it is widely used for implementing the high-performance of AC machine. Nowadays, One-Chip microprocessors or DSP chips are being well-used to implement Vector Control algorithm. DSP Chip have less flexibility for memory decoding and I/O rather than One-Chip microprocessor so that is requires more additional circuit and high cost. And the past One-Chip micro processors have difficult of implementation the complex algorithm because of small memory capacity and low arithmetic performance. Therefore we implemented the vector control algorithm of PMSM(Permanent Magnetic Synchronous Motors) using 80296SA form intel , which have many features as 6M memory space, 500MHz clock frequency, including memory decoding circuit and general I/O, Special I/O(EPA, Interrupt controller, Timer/Count, PWM generator) which is proper controller for the complex algorithm or operation program requiring so much memory capacity, So in this paper we fully digitized the vector control of PMSM included SVPWM Voltage controller using the intel 80296SA

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 F
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• pp.2590-2593
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• 1999

This paper describes the development of Emergency Generator Equipments Diagnosis System for monitoring generator equipments and battery system. This system is capable of measuring on up to 20 separate sites of generator, engine and periphral equipment's. Battery system also capable of measure the setting time, float and discharge voltage of up to 240 cells in a single installation, and has the memory capacity to store battery's alarm data information on up to 200 separate sites. This system are easy to maintain and attain cost effectively, so that prepared for meeting the customer's service needs immediately. The system is additionally programmed with a each model, that will enable to accurately determine the generator equipments and remain battery capacity in a system following a short discharge test. It is also equipped with remote interrogation and control facilities.