• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.9
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• pp.1239-1248
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• 2018

This paper proposes a fault tolerant and high efficiency operation algorithm for a 4 LEG DC/DC converter for a battery energy storage system(BESS) forming a main power source in a standalone DC micro grid. The BESS for the main power supply in the stand-alone DC micro-grid is required to operate at high speed according to fault tolerant control and load by operating at all times. Fault-tolerance control changes the short-circuit fault to an open-circuit fault by using a fuse in case of leg fault in 4 legs, and operates stably through phase shift control. In addition, considering the loss of the power semiconductor, the number of LEG operation is adjusted to operate at high efficiency in the full load region. In this paper, fault tolerant control and high efficiency operation algorithm of DC/DC converter for BESS in standalone DC micro grid is presented and it is proved through simulation and experiment.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.2
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• pp.140-149
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• 2017

This study proposes a new type of active-clamp forward-flyback converter with two transformers that operate in forward and flyback modes during on and off times, respectively, instead of not using an output inductor. The main switch can be turned on with zero-voltage switching (ZVS) using the leakage inductance of the transformer and the output capacitor of the main switch. The leakage inductance should be increased to ZVS. However, the ringing between the leakage inductance of the transformer and the parasitic output capacitance of the secondary side rectifier switches results in a serious voltage spike. A forward-flyback converter employing auxiliary inductor and auxiliary diode is proposed to overcome the problem. The operational principles are analyzed in detail and validated through experiments with a 385 V-to-53 V/37 A prototype.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.289-290
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• 2012

This paper proposes a new active snubber boost PFC converter to provide a zero-voltage-switching (ZVS) turn-on condition and reduce electromagnetic interference (EMI) noise in home appliances and renewable energy applications, including solar or fuel cell electric systems. The proposed active snubber circuit enables a main boost switch of the boost-type PFC or grid converter to turn on under a ZVS condition and reduce the switching losses of the main boost switch. Moreover, for the purpose of a specialized intelligent power module (IPM) fabrication, the proposed boost circuit is designed to satisfy some design aspects such as space saving, low cost, and easy fabrication. Simulation and experimental results of a 2kW IPM boost-type PFC converter are provided to verify the effectiveness of the proposed active snubber boost circuit.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1094-1096
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• 2002

A new technique for improving the efficiency of single-phase high-frequency boost converter is proposed. This converter includes an additional low-frequency boost converter which is connected to the main high-frequency switching device in parallel. The additional converter is controlled at lower frequency. Most of the current flows in the low-frequency switch and so, high-frequency switching loss is greatly reduced accordingly. Both switching device are controlled by a simple method; each controller consists of a comparator, a frequency generator and an error amplifier. The converter works cooperatively in high efficiency and acts as if it were a conventional high-frequency boost converter with one switching device, The proposed method is verified by simulation and experiment. This paper describes the converter configuration and design, and discusses the steady-state performance concerning the switching loss reduction and efficiency improvement.

• Journal of the Institute of Convergence Signal Processing
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• v.3 no.3
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• pp.70-75
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• 2002

This paper proposes new single stage power factor correction (PFC) full bridge converter. The proposed converter is combined previous ZVS full bridge DC/DC converter with two inductors, two diodes, two magnetic coupling transformer for PFC. This process of power is isolated from the source and also regulate stable DC output voltage in a category. In this topology, the voltage stress of main switches is reduced by zero voltage switching. Moreover, the proposed converter doesn't need active PFC switch and auxiliarly circuits, like control and gating board, so it could decrease the size and cost and increase the efficiency.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.6
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• pp.556-563
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• 2001

In this paper a new zero current transition pulse width modulation (ZCT-PWM) buck converter is proposed to combine the desirable feature of both the conventional buck converter and resonant converters. In this proposed scheme an auxiliary circuit is added to the conventional buck converter and used to achieve soft-switching for both the main switch and the freewheeling diode while not incurring any additional losses due to auxiliary circuit And this converter operates exactly like the conventional PWM converter except for a short particular time interval. The operation of the proposed converter is explained and analyzed. and design guidelines are presented. To validate the feasibility of the proposed converter, a 100KHz 180-W prototype is built and tested.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.6
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• pp.618-626
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• 2011

Solar cell is one of the most important new renewable energy for future energy generation. This paper presents a novel two stage DC/DC converter topology for PV PCSs. The proposed converter consists of an interleaved boost converter and a two-tank LLC resonant converter which is connected in parallel in primary and series in secondary. The main idea of this topology is that the system can achieve either unilateral or bilateral operations due to the input voltage level of the PV module, which leads to a better performance. The operating schemes on the proposed converter are analyzed and described. A 2.2kW prototype product is built, tested and verified.

• Journal of Electrical Engineering and Technology
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• v.3 no.2
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• pp.152-161
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• 2008

This paper deals with a new wave shaping technique for cost effective harmonic mitigation in ac-dc converter feeding Vector Controlled Induction Motor Drives(VCIMD's) for improving power quality at the point of common coupling(PCC). The proposed harmonic mitigator consists of a polygon connected autotransformer based twelve-pulse ac-dc converter and a small rating passive shunt filter tuned for $11^{th}$ harmonic frequency. This ac-dc converter eliminates the most dominant $5^{th},\;7^{th},\;and\;11^{th}$ harmonics and imposes the reduction of other higher order harmonics from the ac main current, thereby improving the power quality at ac mains. The design of autotransformer is carried out for the proposed ac-dc converter to make it suitable for retrofit applications, where presently a 6-pulse ac-dc converter is used. The effect of load variation on VCIMD is also studied to demonstrate the effectiveness of the proposed ac-dc converter in a wide operating range of the drive. Experimental results obtained on the developed laboratory prototype of the proposed harmonic mitigator are used to validate the model and design of the ac-dc converter.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.2
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• pp.133-141
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• 2020

The use of high-gain-voltage step-up converters for distributed power generation systems is being popularized because of the need for new energy generation and power conversion technologies. In this study, a new constructed high-gain-boost DC-DC converter was proposed to coordinate low voltage output DC sources, such as PV or fuel cell systems, with high DC bus (380 V) lines. Compared with traditional boost DC-DC converters, the proposed converter can create higher gain and has wider input voltage range and lower voltage stress for power semiconductors and passive elements. Moreover, the proposed topology produces multilevel DC voltage output, which is the main advantage of the proposed topology. Steady-state analysis in continuous conduction mode of the proposed converter is discussed in detail. The practicability of the proposed DC-DC converter is presented by experimental results with a 300 W prototype converter.

• Journal of Power Electronics
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• v.19 no.6
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• pp.1413-1428
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• 2019

In this paper, a novel zero-voltage and zero-current switching (ZVZCS) interleaved two switch forward converter is proposed. By using a coupled-inductor-type smoothing filter, a snubber capacitor, the parallel capacitance of the leading switches and the transformer parasitic inductance, the proposed converter can realize soft-switching for the main power switches. This converter can effectively reduce the primary circulating current loss by using the coupled inductor and the snubber capacitor. Furthermore, this converter can reduce the reverse recovery loss, parasitic ringing and transient voltage stress in the secondary rectifier diodes caused by the leakage inductors of the transformer and the coupled inductance. The operation principle and steady state characteristics of the converter are analyzed according to the equivalent circuits in different operation modes. The practical effectiveness of the proposed converter was is illustrated by simulation and experimental results via a 500W, 100 kHz prototype using the power MOSFET.