• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.259-261
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• 2008

The electronic products such as laptop PC, cellular phone, robots and etc. need the DC power source. Recently, the secondary battery is frequently used as the portable DC power source and it needs forming process. In this paper, we proposed the bidirectional converter that the battery can be charged with high power factor and the discharged energy is regenerated into AC power source. In the charging mode, the converter acts as the boost rectifier. And the AC input current is controlled in phase with the AC input voltage. As a result, the power factor is improved nearly to unity. In the discharging mode, the DC power of battery wasted in resistor is regenerated to the AC bus line. Finally, the validity of the proposed bidirectional converter is verified by computer simulations and experimentation.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.3
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• pp.227-233
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• 2011

This paper proposes a design and experiment of three phase interleaved dc-dc converter for 5kW battery charger. The charger consists of a three-phase interleaved dc-dc converter, which interfaces batteries and DC link, and a grid connected inverter. Lead-acid battery is modeled in a simple R-C model by matlab. Parameters of the battery are estimated based on step current discharging test. The battery is connected to three-phase interleaved DC-DC converter in order to reduce the ripple current to the battery and so, increase the lifetime of battery. Controller for charging and discharging mode is designed and tested in a 5kW charger prototype.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.524-525
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• 2012

본 논문은 단상 양방향 PWM 컨버터와 공진형 컨버터를 이용한 AC-DC 전력변환 장치를 제안한다. 공진형 컨버터는 변압기의 누설인덕턴스와 정류부의 커패시터를 이용하여 ZCS, ZVS를 얻는다. 제안된 컨버터 설계를 설명하며 시뮬레이션 결과와 실험 결과를 제시한다.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1629-1638
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• 2016

Differential power processing (DPP) systems are among the most effective architectures for photovoltaic (PV) power systems because they are highly efficient as a result of their distributed local maximum power point tracking ability, which allows the fractional processing of the total generated power. However, DPP systems require a high-efficiency, high step-up/down bidirectional converter with broad operating ranges and galvanic isolation. This study proposes a single, magnetic, high-efficiency, high step-up/down bidirectional DC-DC converter. The proposed converter is composed of a bidirectional flyback and a bidirectional isolated switched-capacitor cell, which are competitively cheap. The output terminals of the flyback converter and switched-capacitor cell are connected in series to obtain the voltage step-up. In the reverse power flow, the converter reciprocally operates with high efficiency across a broad operating range because it uses hard switching instead of soft switching. The proposed topology achieves a genuine on-off interleaved energy transfer at the transformer core and windings, thus providing an excellent utilization ratio. The dynamic characteristics of the converter are analyzed for the controller design. Finally, a 240 W hardware prototype is constructed to demonstrate the operation of the bidirectional converter under a current feedback control loop. To improve the efficiency of a PV system, the maximum power point tracking method is applied to the proposed converter.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.1
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• pp.44-52
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• 2017

This paper describes a 100 kW high-efficiency isolated DC-DC converter for DC distribution system. The DC-DC converter consists of two dual-active-bridge (DAB) converters in parallel. The operating principle of the DAB converter is explained, and the algorithm for parallel operation of the DAB converters is proposed. Simulation and experiments are conducted to verify the performance of the proposed system. Experimental results demonstrate that the developed converter excellently marks 97.4 percent of peak efficiency under its normal operating condition.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.198-199
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• 2010

In this paper, bi-directional DC/DC converter using a LC series resonant converter is proposed. A proposed converter is consisted by adding LC series resonant tank into a conventional bi-directional DC/DC converter and performs soft-switching at both boost and buck mode. A LC series resonance occurs in whole operation mode and switching point is determined by specific condition. Through the theoretical analysis and simulation results, operation modes and characteristics of the proposed topology is verified.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.905-914
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• 2016

This paper proposes a new phase current reconstruction technique for interleaved three-phase bidirectional dc-dc converters using a single current sensor. In the proposed current reconstruction algorithm, a single current sensor is employed at the dc-link, and the dc-link current information is sampled at either the peak or valley point of the pulse-width modulation (PWM) carriers regularly. From the obtained current information, all phase currents are reconstructed in a single PWM cycle. After that, the digital current controller is applied to achieve current balancing in each phase. Compare to the previous multiple current sensor method, the proposed strategy reduces the number of the current sensors in the interleaved three-phase bidirectional converter as well as reducing potential current sensing error caused by non-ideal characteristics of the multiple current sensors. The effectiveness of the proposed method is verified from the experiments based on a 3kW three-phase bidirectional converter prototype for the automotive battery charging application.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.157-158
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• 2011

This paper deals with the minimization of switching loss of a dual full-bridge bidirectional DC-DC converter for supercapacitor. In case of charging mode the switching loss can be minimized with proper switching pattern, and the switching loss in discharging mode can be minimized with soft switching. Simulation results show that the switching loss is reduced considerably.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.13-14
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• 2011

This paper deals with the ZVS characteristics of a bidirectional DC/DC converter in idling mode. Simulations are carried out with the supercapacitor which maximum voltage is 50 V. It is found that the ZVS can be achieved as far as the supercapacitor voltage is below 94% of the maximum voltage in idling mode. Therefore, the switching loss in the mode can be small by control the upper limit of the supercapacitor voltage.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.103-104
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• 2012

In the AC module system, mismatch problem between AC power and constant input power is occurred. To solve this problem, electrolytic capacitor is utilized for diminishing power pulsation in PV side. However, it has disadvantages of low life span and weak in temperature. Decoupling method has been studied to reduce the capacitance and replaces electrolytic capacitor to film capacitor. This paper proposes design method for decoupling circuit which bidirectional DC-DC converter using soft switching. Proposed system is verified by design optimization and simulation results.