• Journal of Power Electronics
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• v.6 no.1
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• pp.67-72
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• 2006

This paper introduces two different types of AC current control methods for an indirect vector controlled induction motor using a matrix converter. The proposed methods combine the advantages of matrix converters with the advantages of the indirect vector AC current control methods. The first proposed method explains the basic idea of the hysteresis current control method for matrix converters and shows its capability and stability in comparison to the conventional method usually used for VSI. With the aid of the special configuration of the matrix converter, we also propose another current method which is modified from the first one in order to reduce both current ripple and torque ripple. Simulation results have verified the feasibility and the effectiveness of the proposed methods.

• Journal of IKEEE
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• v.16 no.4
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• pp.335-342
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• 2012

This paper is studied on a new DCM-ZVS step up-down AC-DC converter of high performance, that is, high system efficiency and power factor correction (PFC). The switching devices in the proposed converter are operated by soft switching technique using a new quasi-resonant circuit, and are driven with discontinuous conduction mode (DCM) according to pulse width modulation (PWM). The quasi-resonant circuit uses a step up-down inductor and a loss-less snubber capacitor. The proposed converter with DCM also simplifies the requirement of control circuits and reduces the number of control components. The input AC current waveform in the proposed converter becomes a quasi-sinusoidal waveform proportional to the magnitude of input AC voltage under constant switching frequency. As a result, the proposed converter obtains low switching power loss and high efficiency, and its input power factor is nearly in unity. The validity of the analytical findings is confirmed by some computer simulation results and experimental results.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1634-1641
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• 2018

This study focuses on a high-performance direct active and reactive power controller design that is successfully applicable to three-phase pulse width modulation (PWM) AC/DC converters used in renewable distributed energy generation systems. The proposed controller can overcome the sluggish transient dynamic response of conventional controllers to rapid power command changes. Desired active and reactive powers can be thoroughly obtained at the end of each PWM period through a deadbeat solution. The proposed controller achieves an exact nonlinear cross-coupling decoupling of system power without using a predefined switching table or bang/bang hysteresis control. A graphical and analytical analysis that naturally leads to a control voltage vector selection is provided to confirm the finding. The proposed control strategy is evaluated on a 3 kW PWM AC/DC converter in the simulation and experiment.

• Journal of Power Electronics
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• v.11 no.4
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• pp.561-567
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• 2011

This paper presents a high-efficiency power conditioning system (PCS) for grid-connected photovoltaic (PV) modules. The proposed PCS consists of a step-up DC-DC converter and a single-phase DC-AC inverter for the grid-connected PV modules. A soft-switching step-up DC-DC converter is proposed to generate a high DC-link voltage from the low PV module voltage with a high-efficiency. A DC-link voltage controller is presented for constant DC-link voltage regulation. A half-bridge inverter is used for the single-phase DC-AC inverter for grid connection. A grid current controller is suggested to supply PV electrical power to the power grid with a unity power factor. Experimental results are obtained from a 180 W grid-connected PV module system using the proposed PCS. The proposed PCS achieves a high power efficiency of 93.0 % with an unity power factor for a 60 Hz / 120 Vrms AC power grid.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.9
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• pp.1288-1296
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• 2015

The ac side current of a line commutated converter(LCC) high voltage direct current (HVDC) is characterized by highly non-sinusoidal waveform. If the harmonic current is allowed to flow in the connected ac network, it may cause unacceptable levels of distortion. Therefore, ac side filters are required as part of the total HVDC converter station, in order to reduce the harmonic distortion of the ac side current and voltage to acceptably low levels. The ac filters are also employed to compensate the requested reactive power because LCC HVDC also consume substantial reactive power. Among different types of filters, triple-tuned filters have been widely utilized for HVDC system. This paper presents two design methods of triple-tuned filter; equivalent method and parametric method. Using a parametric method, in particular this paper proposes a design algorithm for a triple tuned filter. Finally, the performance of the design algorithm is evaluated for a 250kV HVDC system in Jeju island. The results cleary demonstrate the effectiveness of proposed design method in harmonics reduction.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.10a
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• pp.327-331
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• 2008

The problems of power factor and harmonics are occurred in converter system which used to SCRs and diodes as power semiconductor devices IGBT was solved that problem, maintain the input line current with sinusoidal wave current of input power source voltage. In this paper, three phase AC to DC boost converter that operates with unity power factor and sinusoidal input currents is presented. The current control of the converter is based on the space vector PWM strategy with fixed switching frequency and the input current tracks the reference current within one sampling time interval. Space vector PWM strategy for current control was materialized as a digital control method. By using this control strategy low ripples in the output voltage, low harmonics in the input current and fast dynamic responses are achieved with a small capacitance in the dc link.

• Journal of Power Electronics
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• v.19 no.2
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• pp.394-402
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• 2019

This paper proposes a single-phase non-isolated onboard battery charger (OBC) for electric vehicles (EVs) that only uses small film capacitors at the DC-link of the AC-DC converter. In the proposed charger, an isolated DC-DC converter for low-voltage batteries is used as an active power decoupling (APD) circuit to absorb the ripple power when a high-voltage (HV) battery is charged. As a result, the DC-link capacitance in the AC-DC converter of the HV charging circuit can be significantly reduced without requiring any additional devices. In addition, some of the components of the proposed circuit are shared in common for the different operating modes among the AC-DC converter, LV charging circuit and active power filter. Therefore, the cost and volume of the onboard battery charger can be reduced. The effectiveness of the proposed topology has been verified by the simulation and experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.4
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• pp.382-395
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• 2011

In this paper, for adapter with power level below approximately 60W, a novel LLC resonant converter preceded by diode rectifier with a capacitor filter is presented. Due to the switching operation of the auxiliary switching device, the proposed LLC resonant converter can deliver power with the high efficiency characteristics from the universal line($110V_{AC}$/ $220V_{AC}$) and load conditions. The operating schemes on the proposed converter are analyzed and described. A 60W prototype product is built, tested and verified.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.5
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• pp.507-511
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• 2019

The use of regenerative energy in AC drive systems has been an issue since the system became an industry standard in the 1990s. According to the quantity of the regenerative energy, the braking resistor in the case of low capacity was common. However the use of such low amount of energy is actively discussed, and the method of mounting the regenerative converter is becoming popular. In this paper, an isolated regenerative converter for reducing the circulating current which is mentioned as the biggest disadvantage of the conventional power regenerative converter system is proposed. In order to save energy, employing a power regenerative converter system for utilizing regenerative energy in an AC drive system is common. However due to the structure of the system, a circulating current is generated, which inevitably causes a decrease in efficiency. In this paper, an isolated regenerative power converter system is proposed to solve the circulating current and computer simulation to verify the possibility. The simulation results show that 20% of the circulating current of the conventional system does not appear in the proposed system, and the validity of the proposed system is confirmed.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.3
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• pp.459-466
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• 2022

Switching surges are a common type of phenomenon that occur on any sort of power system network. These are more pronounced on long transmission lines and in high voltage converter stations. At AC/DC hybrid transmission lines, the insulation coordination of such lines is mainly dictated by the peak level of switching surges, the most dangerous of which include three phase line energization and AC/DC converter station. The power system structure consist of AC/DC hybrid transmission lines which is combination of AC 765kV and ±500kV HVDC 1 bipole system for contingency analysis. The power system under study and its components are simulated using EMTDC software package, the effects of the various AC/DC mixing power lines are reviewed. The developed models of EMTDC conversion lines based on combination of AC/DC system are simulated and the characteristics of switching surge over-voltage from its results are discussed.