• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1202-1209
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• 2014

A novel integrated optimization method is proposed to combine both generation and transmission line expansion problem considering bus voltage limit. Most of the existing researches on the combined generation and transmission expansion planning cannot consider bus voltages and reactive power flow limits because they are mostly based on the DC power flow model. In this paper the AC power flow model and nonlinear constraints related to reactive power are simplified and modified to improve the computation time and convergence. The proposed method has been successfully applied to Garver's six-bus system which is one of the most frequently used small scale sample systems to verify the transmission expansion method.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1147-1149
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• 1992

A novel 3$\phi$ ZVS PWM VSI topology employing a simple dc bus subcircuit that provides soft switching commutations is proposed in this paper. The main advantage of the proposed inverter commutation schem is that the dc bus subcircuit is activated only when required, that is, when dictated by the respective PWM. Detailed analysis is provided and simmulation results are presented to verify the principles of operation of the proposed inverter schem.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.377-382
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• 2005

This paper presents two new circuit topologies of DC bus lineside active edge resonant snubber assisted soft-switching PWM full-bridge DC-DC converter acceptable for either utility AC 200V-rms or AC 400V-rms input voltage source. One topology of proposed DC-DC converters is composed of a typical voltage source-fed full-bridge high frequency PWM inverter using DC busline side series power semiconductor switching devices with the aid of a parallel capacitive lossless snubber. All the active power switches in the full-bridge arms and DC busline can achieve ZCS turn-on and ZVS turn-off commutations and the total turn-off switching power losses of all active switches can be reduced for high-frequency switching action. It is proved that the more the switching frequency of full-bridge soft switching inverter increases, the more soft-switching PWM DC-DC converter with a hish frequency transformer link has remarkable advantages for its efficiency and power density as compared with the conventional hard-switching PWM inverter type DC-DC converter

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.535-537
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• 2008

This paper proposes a modularized two-stage charge equalization converter for a series-connected lithium-ion battery string. In this paper, the series-connected battery sting is modularized into M modules, and each module has K cells in series. With this modularization, low voltage stress on the electronic devices can be achieved. A two-stage dc-dc converter with cell selection switches is employed. The first stage dc-dc converter steps down the high bus voltage to about 10 V. The second stage dc-dc converter integrated with selection switches equalizes the cell voltages. A prototype for 88 lithium-ion battery cells is optimally designed and implemented. Experimental results verify that the proposed equalization method has good cell balancing performance showing low voltage stress, small size, and low cost.

• Journal of Power Electronics
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• v.1 no.2
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• pp.107-116
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• 2001

Two AC-DC PWM full-bridge converters that can input current to improve input power factor while performing dc-dc conversion are investigated in this paper. Both converters are simple in that they are similar to the standard PWM full-bridge converter with a diode rectifier/LC low-pass filter input, and both can operate with a simple method of PWM control. In the paper, the operation of the converters is explained and their steady-state characteristics are discussed. The feasibility of the converters and their ability to meet EN61000-3-2 Class D Standards for electrical equipment are shown with results obtained from experimental prototypes. The performance of both converters in terms of dc bus voltage level, input power factor and efficiency is compared and discussed.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.289-290
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• 2013

소규모 전력망에서 계통에 이상이 발생하면 ESS의 양방향 컨버터는 배터리 충 방전 동작을 멈추고 DC-Bus 전압을 제어하는 기능이 요구된다. 이 경우 양방향컨버터는 배터리측 제어에서 DC-Bus측 고전압제어로의 신속한 전환이 요구된다. 본 논문에서는 양방향컨버터의 끊김없는 입 출력 절환을 위한 새로운 제어기법을 제안한다. 제안하는 기법은 가변리미터를 이용하여 저전압 및 고전압제어기를 하나로 통합하였고 상위제어기의 지령없이 자율적인 판단으로 절환이 가능하다. 제안한 알고리즘은 2kW급 시작품을 제작하여 타당성을 검증하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.2
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• pp.194-200
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• 2014

In DC micro-grid system energy storage systems (ESS) are responsible for storing energy and balancing power. Also, control target of the bidirectional DC-DC converter(BDC) for ESS should be changed depending on the operating mode. During the grid connected mode, the BDC controls the battery current or voltage. When a grid fault occurs, the BDC should change the control target to regulate the DC-bus. The BDC with conventional control method may experience large transient state during the mode change. This paper proposes a control method of BDC for ESS. The proposed control method is able to provide autonomous and seamless mode transfer by a variable current limiter. To validate the proposed concept, simulation results using PSIM and experimental results from a 2kW prototype are provided.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.4
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• pp.319-328
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• 2020

The recent use of distributed power generation systems constructed with DC-DC converters has become extremely popular owing to the rising need for environment friendly energy generation power systems. In this study, a new single-phase five-level inverter for off-grid applications constructed with a multilevel DC-DC step-up converter is proposed to boost a low-level DC voltage (36 V-64 V) to a high-level DC bus (380 V) and invert and connect them with a single-phase 230 V rms AC load. Compared with other traditional multilevel inverters, the proposed five-level inverter has a reduced number of switching devices, can generate high-quality power with lower THD values, and has balanced voltage stress for DC capacitors. Moreover, the proposed topology does not require multiple DC sources. Finally, the performance of the proposed topology is presented through the simulation and experimental results of a 400 W hardware prototype.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.281-283
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• 2006

This paper presents two new circuit topologies of DC bus lineside active edge resonant snubber assisted soft-switching PWM full-bridge DC-DC converter acceptable for either utility AC 200V-rms or AC 400V-rms input voltage source. All the active power switches in the full-bridge arms and DC busline can achieve ZCS turn-on and ZVS turn-off commutations and the total turn-off switching power losses of all active switches can be reduced for high-frequency switching action. The effectiveness of these new DC-DC converters topologies is proved for low voltage and large current high efficiency DC-DC power supplies as TIG arc welding machine from a practical point of view.

• Journal of Power Electronics
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• v.11 no.4
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• pp.479-489
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• 2011

The bidirectional dc-dc converter, being the interface between Energy Storage Element (ESE) and DC bus, is an essential component of the power management system for vehicle applications including electric vehicle (EV), hybrid electric vehicle (HEV), and fuel cell vehicle (FCV). In this paper, a novel multiphase bidirectional dc-dc converter interfacing with battery to supply and absorb the electric energy in the FCV system was studied with the help of real time digital simulator (RTDS). The mathematical models of fuel cell, battery and dc-dc converter were derived. A power management strategy was developed and first simulated in RTDS. A Power Hardware-In-the-Loop (PHIL) simulation using RTDS is then presented. The main challenge of this PHIL is the requirement for a highly dynamic bidirectional Simulation-Stimulation (Sim-Stim) interface. This paper describes three different interface algorithms. The closed-loop stability of the resulting PHIL system is analyzed in terms of time delay and sampling rate. A prototype bidirectional Sim-Stim interface is designed to implement the PHIL simulation.