• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.11
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• pp.1663-1668
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• 2017

A BLDC motor with higher number of phases has several advantages, compared to the conventional three-phase BLDC motors. It can reduce the commutation torque ripple and the iron loss without increasing the voltage per phase and increase the reliability and power density. Higher number of phases increase the torque-per-ampere ratio for the same machine volume and output power by widening the electrical conduction period. In this paper, the proposed seven-phase BLDC motor drive system is made into several functional modular blocks, so that it can be easily extended to other ac motor applications: back-EMF block, hysteresis current control block, pwm inverter block, phase current block, and speed/torque control block. Also in a system of BLDC motor drive, the PI controller has been widely used in the speed controller because of the simple implementation. To obtain a good speed response in a general drive system using the PI controller, the high bandwidth of a controller is established. therefore, in this paper, a Fuzzy controller is applied to the 7-phase BLDC motor drive system in order to improve the speed control performance. The Fuzzy controller is compared with a conventional PI controller through the experiment with respect to speed dynamic responses. These experimental results show that the Fuzzy controller of the 7-phase BLDC motor drive system is superior over the conventional PI controller. The algorithm using the Fuzzy controller can improve a comfortable ride in the field of high performance 7-phase BLDC motor drive applications.

• Journal of Power Electronics
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• v.6 no.3
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• pp.226-234
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• 2006

Photovoltaic (PV) generators have nonlinear V-I characteristics and maximum power points which vary with illumination level and temperature. Using a maximum power point tracker (MPPT) with an intermediate converter can increase the system efficiency by matching the PV systems to the load. This paper presents a maximum power point tracker based on fuzzy logic and a control scheme for a single-phase inverter connected to the utility grid. The fuzzy logic controller (FLC) provides an adaptive nature for system performance. Also the FLC provides excellent features such as fast response, good performance and the ability to change the fuzzy parameters to improve the control system. A single-phase AC-DC inverter is used to connect the PV system to the grid utility and local loads. While a control scheme is implemented to inject the PV output power to the utility grid at unity power factor and reduced harmonic level. The simulation results have shown the effectiveness of the proposed scheme.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.280-282
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• 2002

This paper presents the characteristics and Real Time Digital Simulator(RTDS) model for Seo-deagu Static Var Compensator(SVC) systems installed in 1999. SVC system is a power system controller using power electronics called Flexible AC Transmission Systems (FACTS). RTDS model for Seo-deagu SVC is developed and verified, we recognize to be essential for SVC systems and understand SVC systems through simulation.

• Journal of Power Electronics
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• v.9 no.2
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• pp.288-299
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• 2009

This paper proposes a feedback linearization control scheme of AC/DC PWM converters with LCL input filters using no damping resisters. Feedback linearization techniques use a transformation from nonlinear system models into equivalent linear models in a simpler form. The feedback linearization scheme in this work has cascade structures unlike usual feedback linearization, therefore it has an advantage that it is possible to limit the capacitor current to a certain level. The performance of the proposed controller is validated with simulation and experimental results.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1934-1936
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• 1998

This paper proposes a new control scheme for enhanced power factor in the boost type AC/DC rectifier. The control scheme is to generate duty-cycle pattern without instantaneous measurement of the input line current. With a very simple controller structure the line current is forced to trace a sinusoid in phase with input voltage. The simulation results show the validity of the proposed control scheme.

• Journal of Industrial Technology
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• v.31 no.B
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• pp.75-79
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• 2011

In this paper a new PFC Controller for 3-Phase Modular UPS(Uninterruptible Power Supplies) is proposed. The PFC circuit for 3-Phase Modular UPS is implemented using three 1-phase 3-level boost PFC circuits. To control DC output voltage, single voltage controller considering imbalance of two capacitor voltages and to regulate AC input current three independent current controllers are used in proposed PFC controller. By the proposed method, without additional hardware, THD(Total Harmonic Distortion) of input currents can be readily limited below 5% which is the harmonic current requirements by IEEE std. 519. Its validity is verified by simulations and experiments.

• Journal of the Korean Society for Railway
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• v.10 no.1 s.38
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• pp.51-56
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• 2007

In this paper, control schemes are developed for a propulsion system(Converter/Inverter) in electrical train. A robust controller for PWM converter is proposed. The converter controller consists of a PI controller for DC output voltage and a current controller using error-space approach for maintaining the sinusoidal current waveform and unity power factor. This proposed method is based on characteristic ratio assignment(CRA) method which has the advantage to design the optimal gain to meet the referenced response and overshoot within the limit range. Inverter system is controlled by vector control and slip frequency control. At low speed region, vector control scheme is applied to control instantaneous torque and slip frequency control is performed under overmodulation region and one pulse mode. Because output voltage of converter contains harmonics ripple at twice input ac line frequency, control scheme is developed to reduce the pulsating torque current. The performance of propulsion system will be verified by simulation and prototype experimental results.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.188-189
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• 2016

ITER AC/DC Converter Local Controller는 플라즈마 제어 시스템에서 요구하는 전압 전류 명령에 따라 초전도 코일에 전류를 공급하고 컨버터 System 자체 보호 기능, 초전도 코일시스템 이상 시 Bypass 및 코일 에너지를 계통에 회생하여 에너지를 방전하여야 한다. 코일 별로 플라즈마 제어에 필요한 높은 전압 전류는 전원 장치의 직렬 접속이 요구되고(2직렬, 4직렬, 6직렬) 제어적으로 이들 제어 시스템들은 신뢰도가 높은 디지털 설계를 요구 한다. 본 논문은 다 직렬 전원 장치 제어를 위한 Local Controller의 설계 내용을 논의하고자 한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.8
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• pp.2968-2974
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• 2010

Nowadays, the PV systems have been focused on the grid connection between the power source and the grid. The PV inverter can be considered as the core of the whole system because of an important role in the grid-interfacing operation. An important issue in the inverter control is the load current regulation. In the literature, Proportional Integral (PI) controller, which is normally used in the current-controlled Voltage Source Inverter (VSI), cannot be a satisfactory controller for an AC system because of the steady-sate error and the poor disturbance rejection, especially in high-frequency range. Compared with conventional PI controller, Proportional Resonant (PR) controller can introduce an infinite gain at the fundamental frequency of the AC source; hence it can achieve the zero steady-state error without requiring the complex transformation and the de-coupling technique. Theoretical analyses of both PI and PR controller are presented and verified by simulation and experiment. Both controller are implemented in a 32-bit fixed-point TMS320F2812 DSP processor and evaluated on a 3kW experimental prototype PV Power Conditioning System (PCS). Simulation and experimental results are shown to verify the controller performances.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.755-761
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• 2017

In railways powered by AC power, the main circuit breaker (MCB) is used for supplying the electric power to the catenary of the vehicle. Generally, the main circuit breaker is located between the pantograph and the main transformer, and the phase of the power applied to the vehicle changes according to the operation timing of the main circuit breaker. The operation of the main circuit breaker should be actively controlled according to the phase of the power source, since the phase of the power causes unintended transient states in the vehicle's electrical system in the form of an inrush current and surge voltage. However, the MCB has a delay time when it operates which is not constant. Therefore, an intelligent controller is needed to predict the operation delay time and control the opening and closing of the MCB.