• 한국산업융합학회 논문집
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• 제21권6호
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• pp.361-368
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• 2018

This paper proposes a grid - connected CTTS system that can be soft switched to meet the government's effective resource allocation policy for emergency generator. In order to eliminate the system instability caused by the large inrush current generation in the system switching, a new virtual rotation coordinate method for the dissimilar power source is proposed. The proposed virtual rotation coordinate method improves the voltage detection accuracy of the voltage difference of the dissimilar power supply, and it is proved that the synchronous switching characteristic is excellent. In addition, zero current and system stabilization can be achieved by realizing zero current when blocking CTTS with instantaneous reactive power control. Simulation was carried out to verify the validity of the proposed method, and the 500[kVA] system was fabricated and verified to demonstrate the superiority of the proposed method.

• 한국전기전자재료학회논문지
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• 제33권2호
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• pp.109-113
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• 2020

A power device is a component used as a switch or rectifier in power electronics to control high voltages. Consequently, power devices are used to improve the efficiency of electric-vehicle (EV) chargers, new energy generators, welders, and switched-mode power supplies (SMPS). Power device designs, which require high voltage, high efficiency, and high reliability, are typically based on MOSFET (metal-oxide-semiconductor field-effect transistor) and IGBT (insulated-gate bipolar transistor) structures. As a unipolar device, a MOSFET has the advantage of relatively fast switching and low tail current at turn-off compared to IGBT-based devices, which are built on bipolar structures. A superjunction structure adds a p-base region to allow a higher yield voltage due to lower R_DS (on) and field dispersion than previous p-base components, significantly reducing the total gate charge. To verify the basic characteristics of the superjunction, we worked with a planar type MOSFET and Synopsys' process simulation T-CAD tool. A basic structure of the superjunction MOSFET was produced and its changing electrical characteristics, tested under a number of environmental variables, were analyzed.

• 조명전기설비학회논문지
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• 제17권5호
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• pp.51-59
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• 2003

전력회사와 수용가들은 유도성 부하에 무효전력을 공급하여 역률(수용가)이나 전압(전력회사)을 조절하기 위해 커패시터 뱅크(전력회사는 스타콘이라 함)를 설치 운영하고 있다. 본 논문에서는 전력회사의 스타콘 투입시 발생되는 과도 전압 상승과 고조파를 분석하고자 한다. 과도 전압과 고조파를 저감시키는 간단한 수단중의 하나는 수용가의 커패시터 뱅크를 전력회사의 스타콘을 투입한 후에 과도상태가 지난뒤에 투입하는 방법이다. EDSA프로그램으로 컴퓨터 시뮬레이션을 수행하여 수용가에서의 과도 전압 상승과 고조파 저감 효과를 검증 하였다. 그리고 수용가에서 발생하는 고조파를 잘 알려진 국제 고조파 관리 기준인 IEEE 519와 IEC 1000으로 비교해 보았다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.705-708
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• 2000

Switched Reluctance motors(SRM) attract much attention in motor because they are reliable and inexpensive. With advance in power electronics and high-speed processors the performance of SRM has been enhanced greatly. But they require rotor position information to operate, In many systems rotor position sensors are undesirable and have disadvantages. To overcome the disadvantages include by position sensors a number of sensorless methods for SRM's have been proposed by researchers. This paper describes a method for indirect sensing of rotor position in SRM's pulsewidth modulation voltage control. The method required no priori knowledge of motor parameters excepts for the number of stator and rotor poles. The detection method uses the change of the derivative of the phase current to detect the position.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.1103-1104
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• 2008

In this paper, authors propose a novel step-up AC-DC chopper operated with power factor correction (PFC) and with high efficiency. The proposed chopper behaves with discontinuous current control (DCC) of input current. The input current waveform in the proposed chopper is got to be a discontinuous sinusoid form in proportion to magnitude of ac input voltage under the constant duty cycle switching. Therefore, the input power factor is nearly unity and the control method is simple. In the general DCC chopper, the switching devices are turned-on with the zero current switching, but turn-off of the switching devices is switched at current maximum value. To achieve a soft switching of the switching turn-off, the proposed chopper is used a new partial resonant circuit. The result is that the switching loss is very low and the efficiency of chopper is high.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.558-561
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• 2005

This paper describes a novel method of detecting excitation position in switched reluctance motor(SRM) drive. Some strategies of position sensorless control methods for the motor include the measurement of phase current and applied pulse voltage in an unexcited phase is suggested. The principle of the estimation of a rotor position is based on the detection of inductance by pulse currents. This sensorless method is very simple to detect excitation position estimation and gives efficient control of drive system. Suggested method is verified by some simulations.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.137-139
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• 2001

This paper describes a new methods of detecting rotor position in SRM(switched reluctance motor). The Conventional method of position sensorless control for SRM is measuring phase current and pulse voltage applied in unexcited phase. The estimation of rotor position based on the detection of inductance by pulse current. Implementation is via low-cost electronic circuits with DSP320F241. Test results show that this technique is a possible approach to detect the rotor position of an SRM.

• Journal of Electrical Engineering and information Science
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• 제1권1호
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• pp.51-57
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• 1996

An improved predictive current control technique for a zero current switched(ZCS) buck-boost series resonant inverter(SRI) is proposed to overcome the inherent disadvantages such as the uncontrollable large overshoot and the large current ripple. Using the proposed technique, four quadrant operations of the output voltage and current for an uninterrutible power supply(URS) application are guaranteed and the buck-boost operation can also be obtained without an additional bidirectional switch.

• 전력전자학회논문지
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• 제18권3호
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• pp.232-239
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• 2013

This paper proposes an improved stator flux estimator through ensuring conventional PLPF to act as a pure integrator for sensorless control of induction motors. Conventional PLPF uses the estimated synchronous speed as a cut-off frequency and has the gain and phase compensators. The gain and phase compensators are determined on the assumption that the estimated synchronous angular speed is coincident with the real speed. Therefore, if the synchronous angular speed is not same as the real speed, the gain and phase compensation will not be appropriate. To overcome the problem of conventional PLPF, this paper analyzes the relationship between the synchronous speed error and the phase lag error of the stator flux. Based on the analysis, this paper proposes the synchronous speed error compensation scheme. To achieve a start-up without speed sensor, the current model is used as the stator flux estimator at the standstill. When the motor starts up, the current model should be switched into the voltage model. So a stable transition between the voltage model and the current model is required. This paper proposes the simple transition method which determines the initial values of the voltage model and the current model at the transition moment. The validity of the proposed schemes is proved through the simulation results and the experimental results.

• Journal of Power Electronics
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• 제12권5호
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• pp.787-799
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• 2012

Real and reactive power flows on a transmission line interact inherently. This situation degrades power flow controller performance when independent real and reactive power flow regulation is required. In this study, a quasi multi-pulse interline power flow controller (IPFC), consisting of eight six-pulse voltage source converters (VSC) switched at the fundamental frequency is proposed to control real and reactive power flows dynamically on a transmission line in response to a sequence of set-point changes formed by unit-step reference values. It is shown that the proposed hybrid fuzzy-PI commanded IPFC shows better decoupling performance than the parameter optimized PI controllers with analytically calculated feed-forward gains for decoupling. Comparative simulation studies are carried out on a 4-machine 4-bus test power system through a number of case studies. While only the fuzzy inference of the proposed control scheme has been modeled in MATLAB, the power system, converter power circuit, control and calculation blocks have been simulated in PSCAD/EMTDC by interfacing these two packages on-line.