• Journal of Korean Society of Transportation
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• v.23 no.2
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• pp.151-160
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• 2005

In case of public transit such as bus system, the probability concept is used to evaluate the Level-of-Service of the operations. And each levels could be classified according to the linear probability value. (TCQSM: Transit Capacity and Quality of Service Manual-2nd Edition, TRB, Washington DC., 2003) In this case, the drivers or passengers wouldn't think that the service level isn't equivalent to the linear probability value. Thus the linear probability value doesn't exactly reflect the service level. This study shows the problems of using the linear probability value in classifying the service level through the case of evaluation of bus operation's punctuality, presented in TCQSM. To make up for the problems of such case, two methodologies are presented in this study. The method of determining Level-of-Service criteria using probability density of headway variation's distribution, presented in this paper, adequately reflects passenger's expected waiting time. According to the application result to real bus operation data, it tis better than the method of TCQSM to evaluate the reliability of bus operations. However further research about the relations between utility difference and passenger feeling of service level in necessary to apply the method that uses the utility function. It remains as the limitation of this paper.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2515-2517
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• 1999

In this paper we analysis DC bus voltage stress at high line voltage and light load in $S^4$-PFC Isolated AC/DC converter with DC bus voltage feedback using coupling in transformer. In this converter, the principle of operation and the practical problems in the design are considered. Simulation and experimental results are presented to verify the operation and performance of the $S^4$-PFC converter with DC bus voltage feedback. Experimental sets are performed in the conditions; switching frequency 100 kHz, output of 5 V, 60W, and universal line input voltage.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.968-969
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• 2015

This paper proposes a novel analysis method for calculating inverter DC bus capacitance and line reactor parameters. In the realization process, DC bus capacitance parameter, and ripple current, life of DC bus capacitor, interaction between DC bus capacitance can be calculated by using Newton-Raphson procedure. The design scheme of DC bus capacitor and line reactor, specific parameters such as capacitance, loss, ripple current, central average temperature, life, ripple current, loss, size, central temperature of the reactor were given. Simulation results show that this scheme can accurately calculate the DC bus capacitance and line reactor parameters. Compared with calculation result of references, cost and volume are half. The indicators meet the demand of practical engineering. It had affirmed precision of the analytical method and verified correctness and feasibility of this method.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.223-224
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• 2016

본 논문은 상용급 전기버스의 24 V 전장전력공급장치로써 고전압배터리부터 저전압으로 변성하는 전력변환장치인 저전압 직류변환장치 (Low Voltage DC/DC Converter : LDC) 개발에 관하여 기술한다. 제안하는 LDC는 효율을 높이기 위해 트랜스포머 1차 측 위상천이 전브리지 스위칭 소자에 SiC MOSFET을 사용하고, 2차 측에 동기정류방식을 적용하였다. 고효율 성능을 검증하기 위해 시작품을 제작하고 시험을 통해 3 kW 97% 이상의 고효율, 고출력, 고밀도의 특성을 확인하였다.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2484-2486
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• 1999

본 논문에서는 PWM 승압형 컨버터/인버터를 사용한 교류전동기 구동시스템에서 커먼 모드 전압의 크기를 dc 버스 전압 1/3이하로 제한시키는 새로운 공간전압벡터 PWM 기법을 제안한다. Dc 버스 전압의 2/3에 해당하는 커먼 모드 전압 펄스가 발생하는 경우에 대하여 고찰하고 각각의 경우에 대한 인버터 스위칭 시점의 이동을 통한 제거 방법을 제안한다. 제안된 방법은 부가의 하드웨어를 요구하지 않고 소프트웨어적으로 손쉽게 구현될 수 있으며, 전력변환기의 제어성능에 영향을 미치지 않는다는 장점을 가진다.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.116-117
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• 2017

본 논문에서는 전압 민감도를 통해 직류 마이크로그리드의 전압 변동을 최소화하기 위한 드룹 제어 전원의 위치 선정 기법을 제시한다. 전압 민감도를 도출하기 위해 전력 흐름 분석을 수행하였으며, 드룹 제어의 특성을 반영하기 위해 드룹 버스를 도입하였다. 그러나 드룹 버스를 적용함으로써 전력망의 전압 민감도는 드룹 제어 전원의 위치에 의존하게 된다. 따라서 드룹 제어 전원의 위치에 따른 전압 민감도를 분석하고 이를 비교하여 DC MG의 평균 전압 변동이 최소화되는 위치를 결정하였다. 제안한 드룹 제어 전원의 위치 선정 기법의 결과를 PSCAD/EMTDC 시뮬레이션을 통해 검증하였다.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.107-109
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• 2019

본 논문에서는 직류 마이크로그리드의 버스 전압 진동을 감쇠하기 위한 에너지 저장장치의 제어기법을 제시한다. IDA-PBC 이론을 이용한 제어기를 설계하고, 직류 마이크로그리드의 안정도를 해석한다. PSIM 시뮬레이션을 이용하여 제안하는 기법의 타당성을 검증하였다.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.1
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• pp.40-45
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• 2004

This paper presents the parallel distributed control scheme for shaping of the bent glass. The designed system consists of a PC, a main controller and 11 servo-controllers, the precision motion controllers. Each elements are connected by using RS-232C and 8-bit data bus. In order to guarantee the stability and the control performance, we use a precision PID motion controller and a H-bridge on the servo-drivers. PC calculates position values of 11 DC motors by using the pre-determined curvature value and offers the user interface environment operator. The main controller provides the control instructions and parameter values to 11 servo-controllers by chip enable signal, simultaneously. Using the received commands and parameter values, the servo-controllers control the positions of the DC motors based on PID control scheme.

• Proceedings of the KIPE Conference
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• 2019.11a
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• pp.144-145
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• 2019

This paper proposes a design and analysis for a PI-IP hybrid voltage controller with a combination of PI and IP voltage controller for stable voltage control of DC bus voltage, Transient characteristic of DC bus voltage is improved by designed setting variable value and control method in the variable load and power generation conditions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3A
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• pp.319-323
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• 2007

In this paper, the automatic precision measurement of RF voltage has been done using the power and impedance standards [1] in the frequency range of 50 to 1000 MHz. A coaxial microcalorimeter and an automatic network analyzer were used for the determination of the RF-DC differences and the total uncertainty is about 1.0 %. A HP computer, a commodore computer and IEEE-488 interface bus were used for measuring the effective efficiency of thermistor mount and the RF-DC difference of thermal voltage converter, All processes of measurement were accomplished by self-developed program automatically.