• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.736-741
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• 2005

This paper presents electric characteristics analysis and safe configuration for extension power supply between existent 6.6kV ungrounded distribution system and establishment and improvement 22.9kV direct grounding distribution system. For this, we model 6.6kV ungrounded and 22.9kV direct grounding distribution system of urban underground, ground region. and rural electrical, unelectrical region using PSCAD/EMTDC and analyze voltage drop, charging current, ground and short fault through simulation. To analyze electric characteristics of extension power supply, we simulate extension power supply of overhead line of 6.6kV ungrounded system and underground line of 22.9kV direct grounding system of rural electrical region and propose operation condition for safe extension power supply through result of analysis. Characteristics of voltage drop, charging current, ground and short fault appear almost similarly with electrical characteristic of direct power supply. However, because unbalance of phases may cause relay's malfunction of ungrounded system and ground fault current of direct grounding system may demage facilities of ungrounded system, we propose safe system configuration such as impedance grounding system of neutral point.

• 한국산학기술학회논문지
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• 제8권6호
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• pp.1343-1354
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• 2007

카메라, 휴대전화, 노트북 등과 같이 휴대 가능한 전기전자기기들은 대부분 2차 전지로부터 전원을 공급받고 있다. 2차 전지로서는 타 전지에 비하여 고 에너지 밀도와 고 전압의 특성을 갖고 있는 리튬2차전지가 가장 많이 활용되고 있으며, 이 특성 때문에 전기자동차, 우주왕복선, 분산전원의 한 형태인 전력 저장장치에까지 그 이용이 확대되고 있다. 그러나, 시스템의 최적성능을 보장하기 위해서는 용도별 싸이클 수명성능을 고려한 충방전 설계 및 이를 위한 전기적 등가모델의 정확성이 필수적이다. 따라서, 본 논문에서는 상용 리튬이차전지의 실제 실험 데이터에 근거하여 충/방전 심도 함수를 도출하고, 리튬이차전지의 수명성능평가를 위한 충/방전 특성 모델을 제안하고, 이의 타당성을 입증하였다.

• 한국재료학회지
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• 제31권2호
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• pp.75-83
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• 2021

To cope with automobile exhaust gas regulations, ISG (Idling Stop & Go) and charging control systems are applied to HEVs (Hybrid Electric Vehicle) for the purpose of improving fuel economy. These systems require quick charge/discharge performance at high current. To satisfy this characteristic, improvement of the positive electrode plate is studied to improve the charge/discharge process and performance of AGM(Absorbent Glass Mat) lead-acid batteries applied to ISG automotive systems. The bonding between grid and A.M (Active Material) can be improved by applying the Sand-Blasting method to provide roughness to the surface of the positive grid. When the Sand-Blasting method is applied with conditions of ball speed 1,000 rpm and conveyor speed 5 M/min, ideal bonding is achieved between grid and A.M. The positive plate of each condition is applied to the AGM LAB (Absorbent Glass Mat Lead Acid Battery); then, the performance and ISG life characteristics are tested by the vehicle battery test method. In CCA, which evaluates the starting performance at -18 ℃ and 30 ℃ with high current, the advanced AGM LAB improves about 25 %. At 0 ℃ CA (Charge Acceptance), the initial charging current of the advanced AGM LAB increases about 25 %. Improving the bonding between the grid and A.M. by roughening the grid surface improves the flow of current and lowers the resistance, which is considered to have a significant effect on the high current charging/discharging area. In a Standard of Battery Association of Japan (SBA) S0101 test, after 300 A discharge, the voltage of the advanced AGM LAB with the Sand-Blasting method grid was 0.059 V higher than that of untreated grid. As the cycle progresses, the gap widens to 0.13 V at the point of 10,800 cycles. As the bonding between grid and A.M. increases through the Sand Blasting method, the slope of the discharge voltage declines gradually as the cycle progresses, showing excellent battery life characteristics. It is believed that system will exhibit excellent characteristics in the vehicle environment of the ISG system, in which charge/discharge occurs over a short time.

• 한국재난정보학회 논문집
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• 제16권2호
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• pp.392-401
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• 2020

연구목적: 본 연구는 비상시의 예비전원장치로 사용 가능한 리튬이온커패시터의 동작 특성을 분석하고, 충·방전시의 선형비례특성을 이용하여 전압을 측정하는 것으로도 예비전원장치의 동작 이상 유무를 판단 할 수 있는 실험근거의 제공을 목적으로 한다. 연구방법: 본 연구를 위한 방법으로 먼저 기존 예비전원장치와 리튬이온커패시터에 대한 동작원리 및 특성을 분석하고, 다음으로 실험에 사용한 유도등의 구성도와 시스템 블록도에 따라 리튬이온커패시터의 전압 측정을 통해 배터리의 보유 전력량을 확인하는 전압대역별 방전전력량 측정 값 테스트와 유도등을 이용한 동작 테스트 실험으로 진행한다. 연구결과: 리튬이온커패시터의 선형비례특성을 이용한 충전전압을 확인하는 것만으로도 정확하게 유도등 램프의 유효동작 시간을 추론 할 수 있는 근거를 제시하고 있다. 결론: 재난 상황 시 리튬이온커패시터를 비상유도등의 예비전원장치로 사용함으로써 비상유도등의 완전 방전을 미연에 방지하고, 예비전원장치의 정상 작동 수행의 문제가 발생하지 않게 하며, 간단한 전압측정만으로도 예비전원장치의 이상 유무를 확인 할 수 있게 하여 향후 피난설비 적용에 많은 활용도를 제시하고자 하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제35권6호
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• pp.835-841
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• 2011

해상에서 운영되는 해양 시설물용 파력 발전시스템은 대용량 계통 연계형으로 개발되어 왔다. 그러나 등부표용 파력 발전시스템에는 소용량의 발전시스템이 운영 측면에서 효과적이다. 소형 파력 발전의 경우 단순히 전파 정류하여 축전지에 충전하는 방식(직결 방식)을 주로 사용한다. 본 논문에서는 소형 웰스터빈의 발전 특성을 고려하여 부스터 컨버터 기반의 파력 발전전력제어기를 개발하였다. 직결 방식과 부스터 컨버터 방식의 제어기를 설계하고, 실험을 통하여 그 특성을 비교하였다. 실험 결과 제안하는 제어기가 발전기의 출력전압이 낮은 구간에서 출력특성이 개선되었다.

• Journal of electromagnetic engineering and science
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• 제17권4호
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• pp.191-196
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• 2017

Microwave wireless power transmission (MWPT) is a promising technique for low and medium power applications such as wireless charging for sensor network or for biomedical chips in case with long ranges or in dispersive media such. A key factor of the MWPT technique is its efficiency, which includes the wireless power transmission efficiency and the radio frequency (RF) to direct current (DC) voltage efficiency of RF-DC converter (which transforms RF energy to DC supply voltage). The main problem in designing an RF-DC converter is the nonlinear characteristic of Schottky diodes; this characteristic causes low efficiency, higher harmonics frequency and a change in the input impedance value when the RF input power changes. In this paper, rather than using harmonic termination techniques of class E or class F power amplifiers, which are usually used to improve the efficiency of RF-DC converters, we propose a new method called "optimal input impedance" to enhance the performance of our design. The results of simulations and measurements are presented in this paper along with a discussion of our design concerning its practical applications.

• Journal of Electrical Engineering and Technology
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• 제13권5호
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• pp.1927-1934
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• 2018

In this paper, we studied the state of charge (SOC) estimation algorithm of a high-capacity lithium secondary battery for electric vehicles (EVs) considering temperature characteristics. Nonlinear characteristics of high-capacity lithium secondary batteries are represented by differential equations in the mathematical form and expressed by the state space equation through battery modeling to extract the characteristic parameters of the lithium secondary battery. Charging and discharging equipment were used to perform characteristic tests for the extraction of parameters of lithium secondary batteries at various temperatures. An extended Kalman filter (EKF) algorithm, a state observer, was used to estimate the state of the battery. The battery capacity and internal resistance of the high-capacity lithium secondary battery were investigated through battery modeling. The proposed modeling was applied to the battery pack for EVs to estimate the state of the battery. We confirmed the feasibility of the proposed study by comparing the estimated SOC values and the SOC values from the experiment. The proposed method using the EKF is expected to be highly applicable in estimating the state of the high-capacity rechargeable lithium battery pack for electric vehicles.

• 한국항해항만학회지
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• 제31권10호
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• pp.839-844
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• 2007

본 논문은 벅, 부스터, 벅-부스트 등의 부이용 DC-DC 컨버터 성능에 대하여 기술하였다. PV 시스템과 연계한 컨버터에 관한 특성이 고려된 동작특성 및 충전효율에 대하여 분석하였다. 그것은 MPPT 알고리즘과 더불어 수행되었다. 컨버터를 위한 기본 스위칭 방정식을 기술하고, 스위칭 상태에 따른 방정식을 해석하였다. 이 해석은 부이선택에 초점을 맞추고 있으며, 또한 컨버터 동작 및 제안한 알고리즘의 성능을 관찰하였다. 마지막으로 부이에 적합한 DC-DC 컨버터를 제안하였으며, 벅 컨버터에 대한 특성실험도 수행하였다.

• Journal of Mechanical Science and Technology
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• 제16권11호
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• pp.1457-1469
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• 2002

This paper is the first of several companion papers, which investigate axial stratification process and its effects in an Sl engine. The axial stratification is very sophisticate phenomenon, which results from combination of fuel injection, port and in-cylinder flow and mixing. Because of the inherent unsteady condition in the reciprocating engine, it Is impossible to understand the mechanism through the analytical method. In this paper, the ports were characterized by swir and tumble number in steady flow bench test. After this, lean misfire limit of the engines, which had different port characteristic, were investigated as a function of swirl ratio and injection timing for confirming the existence of stratification. In addition, gas fuel was used for verifying whether this phenomenon depends on bulk air motion of cylinder or on evaporation of fuel. High-speed gas sampling and analysis was also performed to estimate stratification charging effect. The results show that the AFR at the spark plug and LML are very closely related and the AFR is the results of bulk air motion.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1156-1158
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• 1995

Charge decay, thermally stimulated current(TSC), charging and discharging currents(I) are measured for negatively corona-charged polymers. In this study, we will make an experiment in charge decay on polymer surface, TSC, polarity effect and the others in order to analysis it's mechanism. Especially polyvinylidene fluoride(PVDF) film is the best functional material which has been so far. Therefore, It's worthy of notice to investigate it's characteristic. And then some other functional polymers will be focused on. An experimental result was missed out for the shortage of setting. So, this thesis will be explained on the theory and direction of reseach hereafter.