Byung-Kwon Lee

These results suggest that empathy is associated with personality traits, such as RD, C, and SC, and medical education curriculum contributes incrementally to empathy for students. The difference in test scores for empathy between MC students and MS students might be due to differences in personality traits, such as SC.

This paper presents the theory and practice required to implement a novel sensorless operation technique for the brushless DC (BLDC) motor. The proposed new sensorless drive method breaks through the chronic problem of the sensorless BLDC motor drives, lack of low speed operation, so that it ensures highly accurate, robust sensorless operation from near zero to high speed. For this purpose, a physically insightful, speed-independent function, based on a new flux linkage function, is used. A simu

The paper proposes a new topology for photovoltaic DC/DC converter with high efficiency under wide input voltage range is proposed. Photovoltaic DC/DC is a very crucial part of power conditioning system(PCS). Considering that output characteristic of photovoltaic cell has wide voltage range, depending on the operating conditions of photovoltaic cell, the DC/DC converter also needs to have wide input voltage range to regulate the constant output voltage. In addition, a high rated voltage of power

In this paper, a hybrid control of IPT system is proposed in limited operating frequency range according to coupling coefficients. The coupling coefficient k and self-inductance of pad vary according to misalignment and vertical distance condition in inductive power transfer (IPT) system. Those variation cause change of output voltage and zero phase angle (ZPA) frequency. Proposed method enables the system to operate in zero voltage switching (ZVS) region close to ZPA frequency for low VA rating

In this paper, a mixed algorithm is proposed to overcome the limitations of the conventional algorithms, which cannot be applied in various driving patterns of drivers. The proposed algorithm based on the coulomb counting method is mixed with reset algorithms that consist of the enhanced OCV reset method and the DCIR iterative calculation method. It has many advantages, such as a simple model structure, low computational overload in various profiles, and a low accumulated SOC error through the f

This paper suggests loss analysis and calculation methods for efficiency improvement of power conversion equipment in detail. The detailed loss analysis and calculation has been conducted for 3.3kW On-board Battery Charger considering temperature condition. The validity of the analysis and calculation method is verified by simulation model.

This paper proposes a maximum efficiency operation strategy for three-level T-typeinverter in entire operation areas. The three-level T-type inverter has higher and lower efficiency areascompared with two-level inverter. The proposed strategy aims to operate in the maximum efficiencypoint for the low-voltage and low-power home appliances. The three-level T-type inverter is analyzedin detail, and the two operation mode selection strategy is developed. The proposed algorithm isverified by theoreti

직류철도의 회생제동 시 발생되는 회생에너지는 급전선로의 직류가선전압의 상승에 의해 시스템의 오동작이나 차량 정류기의 파손, 또는 급전 시스템의 전력변환 장치의 고장을 일으키는 원인이 될 수 있다. 슈퍼 커패시터를 이용한 회생에너지 저장장치는 직류가선전압을 안정화 하게하는 방법이다. 본 논문에서는 슈퍼 커패시터 뱅크를 이용하여 직류철도 시스템의 에너지 저장장치를 구현하였고, 지하철 2호선 N역과 S역의 실측값을 이용하여 가선전압이 전동차에 의한 회생에너지 발생에 따른 동작 특성과 슈퍼 커패시터의 충․방전 특성을 확인하였다. 본 논문을 통하여 직류철도 시스템에 설치된 회생에너지 저장시스템용 슈퍼 커패시터 뱅크의 동작 특성을 알 수 있고, 향 후 직류철도 모든 변전소의 직류 가선전압 실측 데이터를 이용한다면, 특정 직류철도 운행 구간에 대한 회생에너지 저장장치의 운전특성과 슈퍼커패시터의 용량 및 수명 예측으로 가격을 절감 할 수 있고 전체 시스템의 안정도 와 신뢰성을 향상시킬 수 있다.

본 논문은 전기자동차 (Electric Vehicles, EVs) 및 플러그인 하이브리드 자동차 (Plug-In Hybrid Electric Vehicles, PHEVs)용 리튬 이온 (Li-Ion) 배터리 충전을 위한 3.3 kW급 차량 탑재형 (On-Board) 충전기 하드웨어의 설계 및 제작에 대하여 기술한다. 차량 실장 특성을 고려하여 부하직렬공진형 dc-dc 컨버터를 적용하고, 80-130kHz의 고주파 스위칭 및 ZVS (Zero-Voltage Switching) 기법을 통해 수동소자의 크기를 최적화하여 5.84L, 5.8kg의 저부피, 경량을 달성한다. 전자부하를 대상으로 정전류 (Constant Current, CC) 및 정전압 (Constant Voltage, CV) 제어를 수행하여 92.5%의 고효율 획득 및 성능을 검증한다.

In this paper, dynamics modeling of a PEMFC is performed by electro-chemical equations. The developed PEMFC simulation model is implemented using MATLAB Simulink in order to design an optimal PCS for fuel cell systems. In addition, by use of the developed model as an input source of PCS, the validity of the proposed dynamic characteristic model of the PEMFC is verified by various simulation and experimental results.

The continuous growth of electric vehicles has caused electric power shortages inconventional utilities owing to the charging of electric-vehicle batteries. In order to increase thecapacity of these utilities, photovoltaic systems may be an appropriate solution because of theirbenefits. However, a large amount of loss is generated in a conventional charging structure usingphotovoltaic sources owing to the many power conversion processes. This paper describes a simpleintegrated battery charger th

In the present paper, the characteristics of Mega-Flux®, JNEX-Core®, amorphous and ferrite cores are compared to the inductor of buck-boost converters for Hybrid Electric Vehicles. Core losses are analyzed at the condition of 10 kHz sine wave excitations, and permeability fluctuations vs. temperature and magnetizing force will be analyzed and discussed. Under the specifications of the buck-boost converter for 20 kW THS-II, the power inductor will be designed with Mega-Flux® and JNEX-Core®, and i

The gallium nitride high electron mobility transistors (GaN HEMT) are among the most promising power semiconductor devices. However, these transistors have a small gate voltage margin compared with conventional power devices. In this paper, the gate voltage of GaN HEMTs is mathematically analyzed when it is applied to a zero voltage switching (ZVS) phase-shift full bridge (PSFB) DC–DC converter. The analysis accounts for nonlinear capacitance characteristics under the ZVS switching condition, an

This paper describes the process of optimal resonant frequency design with full-bridge series-loaded resonant dc-dc converter in a high efficiency 3.3 kW on-board battery charger application for Electric Vehicles and Plug-in Hybrid Electric Vehicles. The optimal range of resonant frequency and switching frequency used for ZVS are determined by considering trade-off between loss of switching devices and resonant network with size of passive/magnetic devices. In addition, it is defined charging re

The analysis and design process of the LCL filter with passive damping circuits for threephase grid-connected inverter are presented based on the generalized model of LCL filter. Several types of the passive damping circuits in previous studies could be compared and analyzed by using the generalized model considering various design criteria of passive damping circuits. According to the analysis in this paper, a reasonable configuration of passive damping circuits for three-phase gridconnected in