• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.2
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• pp.150-157
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• 2021

Nowadays, a DC microgrid that can link various distributed power sources is gaining much attention. Accordingly, research on fault situations, such as line-to-line and line-to-ground faults of the DC microgrid, has been conducted to improve grid reliability. However, the blackout of an AC system and the oscillation of a DC bus voltage have not been reported or have not been sufficiently verified by previous research. In this study, a 20 kW DC microgrid testbed using a power HIL simulation technique is proposed. This testbed can simulate various fault conditions without any additional grid facilities and dangerous experiments. It includes the blackout of the DC microgrid caused by the AC utility grid's blackout, a drastic load increment, and the DC bus voltage oscillation caused by the LCL filter of the voltage source converter. The effectiveness of the proposed testbed is verified by using Opal-RT's OP5707 real-time simulator with a 3 kW prototype three-port dual-active-bridge converter.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.203-204
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• 2018

Conventional buck-boost converter has the disadvantage that the output voltage is inverted. The single phase non-inverting buck-boost converter(SPNIBBC) used four swithes has H-bridge type Circuit. The output voltage is not inverted. The SPNIBBC can be controlled by the single carrier method and the dual carrier method according to the modulation method. In this paper, we have fabricated the converter and compared the efficiency according to the modulation method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.5
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• pp.38-44
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• 2002

This paper describes the development of a new voltage recorder for the voltage management of power distribution lines. The voltage characteristics and measurement problems for the power distribution lines are analyzed and the functions required for the recorder are discussed. Applying a dual-slope A/D converter with low noise characteristics the voltage measurement algorithm, design and implementation for the recorder are discussed. Finally, the voltage variations of long-duration over-voltages or under-voltages, and short-duration temporary interruption based on IEEE 1159 are analyzed. It is verified with the experiment.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.143-149
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• 2016

The two-stage converter is widely used in traditional DC/AC inverter. It has several disadvantages such as complex topology, large volume and high loss. In order to overcome these shortcomings, a novel half load-cycle worked dual SEPIC single-stage inverter, which is based on the analysis of the relationship between input and output voltages of SEPIC converters operating in the discontinuous conduction mode (DCM), is presented in this paper. The traditional single-stage inverter has remarkable advantages in small and medium power applications, but it can’t realize boost DC/AC output directly. Besides one pre-boost DC/DC converter is needed between the DC source and the traditional single-stage inverter. A novel DC/AC inverter without pre-boost DC/DC converter, which is comprised of two SEPIC converters, is studied. The output of dual SEPIC converters is connected with anti-parallel and half load-cycle control is used to realize boost and buck DC/AC output directly and work properly, whatever the DC input voltage is higher or lower than the AC output voltage. The working principle, parameter selection and the control strategy of the inverters are analyzed in this paper. Simulation and experiment results verify the feasibility of the new inverter.

• Journal of Power Electronics
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• v.18 no.3
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• pp.662-671
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• 2018

This paper presents a new structure for a step up dc-dc converter, which has several advantageous features. Firstly, the input dc source and the clamped capacitor are connected in series to transfer energy to the load through dual voltage multiplier cells. Therefore, the proposed converter can produce a very high voltage and a high conversion efficiency. Secondly, a double voltage clamped circuit is introduced to the primary side of the coupled inductor. The energy of the leakage inductance of the coupled inductor is recycled and the inrush current problem of the clamped circuits can be shared equally by two synchronous clamped capacitors. Therefore, the voltage spike of the switch tube is solved and the current stress of the diode is reduced. Thirdly, dual voltage multiplier cells can absorb the leakage inductance energy of the secondary side of the coupled inductor to obtain a higher efficiency. Fourthly, the active switch turns on at almost zero current and the reverse-recovery problem of the diodes is alleviated due to the leakage inductance, which further improves the conversion efficiency. The operating principles and a steady-state analysis of the continuous, discontinuous and boundary conduction modes are discussed in detail. Finally, the validity of this topology is confirmed by experimental results.

• Journal of Power Electronics
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• v.18 no.1
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• pp.45-55
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• 2018

It is usually difficult for dual-active-bridge (DAB) dc-dc converters to operate efficiently at light loads. This paper presents an in-depth analysis of a DAB with triple-phase-shift (TPS) control under the light load condition to overcome this problem. A kind of operating mode which is suitable for light load operation is analyzed in this paper. First, an analysis of the zero-voltage-switching (ZVS) constraints for the DAB converter has been carried out and a reasonable dead-band setting method has been proposed. Secondly, the basic operating characteristics of the converter are analyzed. Third, under the condition of satisfying the ZVS constraints, both the reactive power and the root mean square (RMS) value of the current are simultaneously minimized and a particle swarm optimization (PSO) algorithm is employed to analyze and solve this optimization problem. Lastly, both simulations and experiments are carried out to verify the effectiveness of the proposed method. The experimental results show that the converter can effectively achieve ZVS and improved efficiency.

• Journal of Electrical Engineering and Technology
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• v.1 no.3
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• pp.343-350
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• 2006

This paper introduces a new high efficient bi-directional, non-isolated DC/DC converter. Through variations of the topology of the conventional Cuk converter, an optimum bi-directional DC/DC converter is proposed. Voltage and current in the proposed DC/DC converter are continuous. Furthermore, the efficiency in both step-up and step-down mode is improved over that of the conventional bi-directional converter. To prove the validation for the proposed converter, simulations and experiments are executed with a 300W bi-directional converter.

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.109-110
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• 2017

본 논문에서는 듀얼 액티브 브릿지에서 SPWM(Single Pulse Width Modulaton)과 DPWM(Dual Pulse Witdh Modulation)을 적용하였을 때, 인덕터 전류의 특성을 비교하고자 한다. 인덕터 전류의 특성을 이론적으로 분석하고, 실험을 통해서 결과를 분석하였다.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.355-358
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• 2004

Currently, to overcome the limit of a 14V power supply system and to enhance the stability of this system high and to make the fuel efficiency better, a research development of a 42V power supply system is actively the progress. As an intermediate step to change into an unity power supply system, a 42V/14V dual power supply system uses a DC/DC Converter as one of structure elements. Considering the main electric power sources in the next generation of the car is a 42V system a 14V power supply system has advantages as follows : In be managed efficiently and to increase the redundancy at start, to jump start with any vehicles, etc. We need the introduction of a hi-directional converter that can flow the energy each other in a dual 42V-l2V system. This paper proposed the ZVS hi-directional CUK DC/DC converter which decrease the weight with the size of the DC/DC Converter and minimize the loss when the switching happen. In this paper, a circuit design method and an action principle of the circuit was proposed. To verify the proposed circuit, a comprehensive evaluation with theoretical analysis, simulation results is presented.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.4
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• pp.332-338
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• 2002

High current coil power supply for superconductivity coil of tokamak requires fast dynamics performance of di/dt and smooth change over of current direction. To meet the specification high performance DSP-based controller Is designed for 12-pulse thyristor dual converter with interphase transformer(IPT). Not only the total current of Y and $\Delta$ converter units but also the difference for those should be regulated fast and accurately. Proportional and integral controller is designed for current difference control and the controller output is compensated to $\Delta$ converter. The source voltage phase angle detection and gate pulse generation algorithm are implemented in software for higher reliability of current control. The current error Is reduced by selection of appropriate initial gating angle during the transient of change over of current direction between thyristor converters.