• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
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• pp.860-863
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• 2003

In this paper high power SMU(Source Measurement Unit) having 50V/1.5A source/measure range has been designed and implemented. The SMU has two operation mode, voltage mode and current mode. The SMU can be used as variable voltage source, variable current source, voltage meter, or current meter. Combining two different unit, output power can be doubled as 100V/1.5A. The developed SMU tan be used many semiconductor testing system and electronic device inspecting system.

• 한국초전도ㆍ저온공학회논문지
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• 제2권2호
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• pp.15-19
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• 2000

The stability of variable cross-sectional area HTS current lead is considered. The cross-sectional area is varied to have a constant safety factor which is defined as the ratio of operating current and critical current of superconductor. As the constant area HTS lead, the variable cross-sectional area HTS lead also has three steady states above the bifurcation point and only one steady state below the bifurcation point. The temperature profiles and current sharing ratios for each steady state are calculated. The heat dissipation into cryogenic system for super-conducting, intermediate, and upper states are compared. For Bi-2333 sheathed with silver-gold alloy 2m length of current lead, and the maximum temperature of upper state seems to be burn-out free below 5m length.

• 전력전자학회논문지
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• 제16권3호
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• pp.258-265
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• 2011

본 논문은 다이어프램의 공기압력을 제어하기 위한 가변 주파수 전류 제어기를 제안한다. 제안된 제어기는 기존의 다이어프램의 공기압력을 제어하는 방법과는 달리 단상 인버터를 이용하여 상 전류와 주파수를 제어한다. 한 상의 전류는 다이어프램의 지령 공기 압력을 추종하도록 조절되고, 전류 주파수는 기계적인 진동을 줄이기 위해 변화한다. 일정한 공기압력으로 부드럽게 변화하기 위해서 전류 주파수는 전류 제어기에서 제어전압에 따라 제어되며, 이 때의 상전류가 일정한 공기압력에 만족하게 되면 전류주파수는 다이어프램의 진동을 줄이기 위해 증가된다. 제어 전압에 의한 상 전류가 지령값보다 높게 되면 전류 주파수는 공기압력을 추종하기 위해 감소된다. 제안된 제어방식은 상용 다이어프램을 이용한 실험을 통해 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.504-507
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• 1997

It is well known that Variable Structure Controller(VSC) is robust to parameters variation and disturbance but its performance depends on the design parameters such as switching gain and slope of sliding surface. This paper proposes a more robust VSC that is composed of local VSC's. Each local VSC considers the local system dynamics with narrow parameter variation and disturbance. First we optimize the local VSC's by use of Evolution Strategy, and next we use Artificial Neural Network to generalize the local VSC's and construct the overall VSC in order to cover the whole range of parameter variation and disturbance. Simulation on BLDC motor current control shows that the proposed VSC is superior to the conventional VSC.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.57-59
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• 2018

This paper presents a novel reference variable speed control scheme of a BLDC motor for the high-speed blender machine according to the current limit. Because of a pulsating load variation of a high-speed blender machine, the actual speed is pulsated by the current limit in the high-speed region. The proposed control scheme uses a variable reference speed to reduce the speed variation from the current limit in the constant power region. The pulsated load is occurred at the material crushing, then the pulsated load is reduced after grinding. The reference speed is smoothly reduced at the pulsated load variation, then the enough torque can make a constant speed during crushing. When the pulsating load is reduced, the reference speed is automatically increased to the original speed value. The proposed control scheme is verified by experimental result by practical blender machine.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 전력전자학술대회 논문집
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• pp.184-185
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• 2013

In this paper, design of a variable inductor using MR Fluid Gap is proposed for wide load range efficiency improvement of a bidirectional DC-DC converter. As compared to conventional constant value inductor designed to have negative current for ZVS at heavy load but suffers high losses at light load due to its small inductance, the proposed variable inductor not only have small inductance at high current for ZVS but also it has large inductance at low current to decrease light load losses.

• ETRI Journal
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• 제28권3호
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• pp.386-388
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• 2006

Monolithic SiGe heterojunction bipolar transistor (HBT) variable gain amplifiers (VGAs) with a feedforward configuration have been newly developed for 5 GHz applications. Two types of the feedforward VGAs have been made: one using a coupled-emitter resistor and the other using an HBT-based current source. At 5.2 GHz, both of the VGAs achieve a dynamic gain-control range of 23 dB with a control-voltage range from 0.4 to 2.6 V. The gain-tuning sensitivity is 90 mV/dB. At $V_{CTRL}$= 2.4 V, the 1 dB compression output power, $P_{1-dB}$, and dc bias current are 0 dBm and 59 mA in a VGA with an emitter resistor and -1.8 dBm and 71mA in a VGA with a constant current source, respectively.

• Journal of Power Electronics
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• 제11권3호
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• pp.285-293
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• 2011

This paper proposes two SRM driving systems using a variable dc-link voltage controlled by a single-phase inverter. Two SRM converter topologies of a half bridge type and a full bridge type are proposed according to the power circuits of an inverter. The phase current can be controlled by means of a PWM controller at the inverter, and the turn-on/off angle at the phase switches can be controlled by a position sensor at the converter in the drive system. The inverter acts as a peak-current limiter if the transient current exceeds its maximum value. SRMs using the proposed topologies maintain high efficiency due to energy regeneration after the turn-off of power switches. The operational modes of the proposed topologies are verified by simulation and experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.240-243
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• 2001

This paper presents the digital controller using variable gain for single-phase power factor correction (PFC) converter. Generally, the gain of inner current control loop in single-stage PFC converter has a constant magnitude. This is why input current is distorted under low input voltage. In particular, a digital controller has more time delay than an analog controller which degrades characteristics of control loop. So, it causes the problem that the gain of current control loop isn't increased enough. In addition, the oscillation happens in the peak value of the input voltage open loop PFC system gain changes according to ac input voltage. These aspects make the design of the digital PFC controller difficult. In this paper, the improved digital control method for single-phase power factor converter is presented. The variable gain according to input voltage and input current help to improve current shape. The 800W converter is manufactured to verify the proposed control method.

• Journal of Power Electronics
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• 제14권2호
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• pp.302-314
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• 2014

Due to advancements in power electronics and inverter topologies, the current controlled multilevel voltage-source pulse width modulated (PWM) inverter is usually preferred for accurate control, quick response and high dynamic performance. A multilevel topology approach is found to be best suited for overcoming many problems arising from the use of high power converters. This paper presents a comprehensive review and comparative study of several current control (CC) techniques for multilevel inverters with a special emphasis on various approaches of the hysteresis current controller. Since the hysteresis CC technique poses a problem of variable switching frequency, a ramp-comparator controller and a predictive controller to attain constant switching frequency are described along with its quantitative comparison. Furthermore, various methods have been reviewed to achieve hysteresis current control PWM with constant switching frequency operation. This paper complies various guidelines to choose a particular method suitable for application at a given power level, switching frequency and dynamic response.