• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.176-179
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• 2005

This paper proposed the two-transistor forward circuit using PFC, lossless snubber and synchronous rectifier for low voltage and high current output. The principle of operation, feature and design considerations is illustrated and verified through the experiment with a 200W(5V, 40A) 100kHz MOSFET based experimental circuit.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.5-6
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• 2017

이 논문에서는 경 부하 레귤레이션 역량을 키우기 위한 새로운 동기정류기 제어 방법을 제안한다. 제안하는 방법은 동기정류기의 턴-온 시간을 늘려줌으로써 동기정류기에 음의 방향으로 전류를 흘려주는 방식을 사용한다. 동기정류기의 턴온 시간에 따른 전압이득의 변화를 확인하여 경 부하 레귤레이션 특징을 분석한다. 이를 통하여 추가적인 소자 없이 경 부하시의 레귤레이션 문제를 해결한다.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.150-152
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• 1998

ZVS Half-Bridge converter is proposed. This converter is operating in fixed switching frequency to regulate output voltage. The ZVS is maintained by Partial resonance during the OFF interval of both switches. Using self-driven synchronous rectifier, this circuit minimizes the Power loss in the rectification circuit. 50[W] ZVS Half-Bridge converter is simulated and built. Two results has been compared.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.35 no.12
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• pp.541-554
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• 1986

This paper presents the results of driving performance analysis of permanent magnet synchronous motor using a microprocessor based control system. The system consists of three phase power transistor inverters, three phase controlled rectifier, three central processing units, and sensors. The three CPUs are, respectively, used to generate PWM control signals for the inverter generating three phase sine wave, to generate the gate control signals for firing the converter, and to supervise other two CPUs. The supervisor is used to compute PI control algtorithm to three phase reference sine wave for the inverter. It is also used to maintain a constant voltage frequency ratio for the converter operating as a constant torque controller. The inverter CPU retrieves precomputed PWM patterns from look up tables because of computation speed limitations found in almost available microprocessors. The converter CPU also retrieves precomputed gate control patterns from another look-up tables. For protecting the control ststem from any damage by extraordinary over currents, the supervisor receives the data from current sensor, CT, and break down the CB to isolate the circuits from source. A resolver has a good performance characteristics of overall speed range, especially on low speed range. Therefor the speed control accuracy is impoved. The microprocessor based PM synchronous motor control system, thus, has many advantages such as constant torque characteristics, improvement of wave, limitation on extraordinary over currents, improvement of speed control accuracy, and fast response speed control using multi-CPU and look-up tables.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.3
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• pp.378-386
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• 2012

For reduction of the amount of CO2 emitted from ships, power generation characteristics of two power generation systems consisting of a high-efficiency permanent magnet synchronous generator and diode bridge rictifiers are discussed in this paper. One of the discussed systems has three-phase stator windings, and the other has two sets of three-phase (six-phase) stator windings to reduce pulsation in the electromagnetic torque and DC current. Experimental results reveal that the power generation efficiency of the system having six-phase stator windings is higher than that of the system having three-phase stator windings for a light load. The maximum power generation efficiency of the system having six-phase stator windings is almost the same as that of the system having three-phase stator windings. For the electromagnetic torque of the system having six-phase stator windings, the width of pulsation is about one-fifth compared to the system having three-phase stator windings.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.12
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• pp.609-615
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• 2005

A 30kW electrical power conversion system is developed for a variable speed wind turbine. In the wind energy conversion system(WECS) a synchronous generator with field current excitation converts the mechanical energy into electrical energy. As the voltage and the frequency of the generator output vary according to the wind speed, a 6-bridge diode rectifier and a PWM boost chopper is utilized as an ac-dc converter maintaining the constant dc-link voltage with only single switch control. An input current control algorithm for maximum power generation during the variable speed operation is proposed without any usage of speed sensor. Grid connection type PWM inverter converts dc input power to ac output currents into the grid. The active power to the grid is controlled by q-axis current and the reactive power is controlled by d-axis current with appropriate decoupling. The phase angle of utility voltage is detected using software PLL(Phased Locked Loop) in d-q synchronous reference frame. Experimental results from the test of 30kW prototype wind turbine system show that the generator power can be controlled effectively during the variable speed operation without any speed sensor.

• Journal of Power Electronics
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• v.19 no.6
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• pp.1536-1543
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• 2019

This paper presents an improved torque predictive control (TPC) for permanent magnet synchronous motors (PMSMs) using an indirect matrix converter (IMC). The IMC has characteristics such as a high power density and sinusoidal waveforms of the input-output currents. Additionally, this configuration does not have any DC-link capacitors. Due to these advantages of the IMC, it is used in various application field such as electric vehicles and railway cars. Recently, research on various torque control methods for PMSM drives using an IMC is being actively pursued. In this paper, an improved TPC method for PMSM drives using an IMC is proposed. In the improved TPC method, the magnitudes of the voltage vectors applied to control the torque and flux of the PMSM are adjusted depending on the PMSM torque control such as the steady state and transient response. Therefore, it is able to reduce the ripples of the output current and torque in the low-speed and high-speed load ranges. Additionally, the improved TPC can improve the dynamic torque response when compared with the conventional TPC. The effectiveness of the improved TPC method is verified by experimental results.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.207-216
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• 2017

Wind energy conversion systems (WECS) which consist of wind turbines with permanent magnet synchronous generator (PMSG) and full-power converters have become widespread in the field of renewable power systems. Generally, conventional diode bridge rectifiers have used to obtain a constant DC bus voltage from output of PMSG based wind generator. In recent years, together advanced power electronics technology, Pulse Width Modulation (PWM) rectifiers have used in WECS. PWM rectifiers are used in many applications thanks to their characteristics such as high power factor and low harmonic distortion. In general, L, LC and LCL-type filter configurations are used in these rectifiers. These filter configurations are not exactly compensate current and voltage harmonics. This study proposes a hybrid passive filter configuration for PWM rectifiers instead of existing filters. The performance of hybrid passive filter was tested via MATLAB/Simulink environment under various operational conditions and was compared with LCL filter structure. In addition, neuro-fuzzy controller (NFC) was preferred to increase the performance of PWM rectifier in DC bus voltage control against disturbances because of its robust and nonlinear structure. The study demonstrates that the hybrid passive filter configuration proposed in this study successfully compensates current and voltage harmonics, and improves total harmonic distortion and true power factor.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.984-985
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• 2008

In this paper, MPPT(maximum power point tracking) control method of the seaflow generation system using DC-DC converters is proposed. This system consists of a variable speed seaflow generation system with permanent magnet synchronous generator, diode rectifier and DC-DC converter. In this proposed seaflow generation system, diode rectifier and DC-DC converter use for converting AC to DC and maximum power generation control, respectively. Advantages of MPPT control method presented in this paper don’t need to use the characteristic of the seaflow turbine at various seaflow speed and measure the seaflow speed and the rotating speed of seaflow turbine. Therefore, the proposed system has the characteristics of lower cost, lower complexity and higher efficiency. The effectiveness of algorithm is simulated and confirmed through Matlab Simulink.

• The Transactions of the Korean Institute of Power Electronics
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• v.2 no.3
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• pp.26-36
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• 1997

An single stage AC/DC converter based on half bridge topology suitable for low power level applications is proposed. The proposed converter has high power factor, low harmonic distortion, and tight output regulations. Asymmetrical control and synchronous rectification are adopted to reduce the switching loss and rectification loss, respectively. The modelling employing average modelling method and detailed analysis are performed to derive the design equations. According to these design equations, a prototype converter has been designed and experimented. This prototype meets the IEC 555-2 regulations with near unity power factor and high efficiency.