• Journal of Power Electronics
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• v.10 no.5
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• pp.461-467
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• 2010

This paper proposes a new soft-switched Sepic converter. It has low switching losses and low conduction losses due to its auxiliary communicated circuit and synchronous rectifier operation, respectively. Because of its positive and buck/boost-like DC voltage transfer function (M=D/(1-D)), the proposed converter is desirable for use in distributed power systems. The proposed converter has versions both with and without a transformer. The paper also suggests some design guidelines in terms of the power circuit and the control loop for the proposed converter.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1610-1620
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• 2015

A major problem in conventional multilevel inverter is that an increase in power semiconductor switches causes an increase in cost and switching losses of the inverter. The multicarrier strategy adopted for the multilevel inverters has become more popular due to reduced cost, lower harmonic distortion, and higher voltage capability than the conventional switching strategy applied to inverters. Various topologies and modulation strategies have been reported for utility and drive applications. Level shifted based pulse width modulation techniques are proposed to investigate the performance of the multilevel inverter. The proposed work focuses on reducing the utilized switches so that the cost and the switching losses of the inverter do not go up and the consistent efficiency could be achieved. This paper presents the detailed analysis of these topologies. The analysis is based on the number of switches, DC sources, output level, maximum voltage, and the efficiency. As an illustration, single phase cascaded multilevel inverter topologies are simulated using MATLAB/SIMULINK and the experimental results demonstrate the viability of these inverters.

• Journal of IKEEE
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• v.19 no.1
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• pp.73-79
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• 2015

In this paper, maximum boost space vector pulse-width modulation(MBSVPWM) strategy of Z-Source Inverters(ZSIs) is proposed. Conventional space vector pulse-width modulation(SVPWM) method of Voltage Source Inverters(VSIs) is modified to produce unique PWM patterns that realize the maximum boost control of ZSIs. This proposed method minimizes the switching power losses of ZSIs by reducing the numbers of the shoot-through states. Moreover, some switches keep ON state and the switching transitions do not occur during the specific sectors. An experimental system has been built and tested to verify the effectiveness of the proposed strategy.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.918-919
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• 2008

This paper deals with the DC-DC converter with high efficiency using the minimum reactor. In this paper, the proposed convert uses the air core reactor for ZCS(zero currunt switching) which can minimize the core losses and removes the over switching losses by soft switching. The proposed converter is verified by the modes analysis and computer simulation to prove the theoretical background and adequacy.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1348-1350
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• 2000

Zero-voltage and zero-current switched single-stage approach with high power factor is presented to reduce the switching losses and to achieve sinusoidal, unity power factor input currents. This single-stage approach, which combines a boost converter used as PFC with a half-bridge converter used as do to do conversion into one power stage, has a simple structure and low cost. At the same time, since the switches of the proposed converter are designed to be turned on at zero-voltage and off at zero-current, the switching losses could be reduced considerably. Detailed analysis and experimental results are presented on the proposed converter, which is operated at constant switching frequency and in discontinuous conduction mode.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.211-214
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• 2001

This paper introduces a ZC-ZVS PWM(Pulse-Width -Modulation) boost converter. The IGBT(main switch) of the proposed converter is always switched at ZCS and soft switching of MOSFET(auxiliary switch) as well. Therefore, the proposed converter minimized the turn on/turn off switching losses of switches and reduced conduction losses by using IGBT switch. Moreover, using paralleled IGBT-MOSFET switch overcame the switching frequency limitation. Therefore high power density system can be realized. As mentioned above, the characteristics are verified through experimental results.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.129-131
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• 1993

Power conversion system of high performance requires high switching frequency power converter. In order to minimize commutation stress and switching losses, in this paper, AC-DC converter is embedded a partial resonant DC-Link circuit with the object of ZVCS(zero voltage switching and zero current switching). The partial resonant occurs just before converter switch operates. Thus, VA ratings of the elements and their dissipations due to effective series resistance (ESR) are very low. Some simulative results on computer are included to confirm the validity of the analytical results.

• KEPCO Journal on Electric Power and Energy
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• v.4 no.2
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• pp.47-53
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• 2018

VSC technology is now well established in HVDC and is, in many respects, complementary to the older Line Commutated Converter (LCC) technology. Despite the various advantages of VSC technology, VSC HVDC stations have higher power losses than LCC stations. Although the relative advantages and disadvantages are well known within the industry, there have been very few attempts to quantify these factors on an objective basis. This paper describes methods to determine the operating losses of every component in the valve of VSC-HVDC system. The losses of the valve, including both conduction losses and switching losses, are treated in detail.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.541-543
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• 1997

In this paper, a proposed resonant PWM switching technique makes the boost AC/DC converter to high input power factor and less switching loss. Also, the switching control scheme is used which minimize harmonic components employing novel PWM technique. In addition, an employment of resonant circuit for switching makes zero current switching(ZCS) and zero voltage switching(ZVS) for control switches without switching losses. The result shows that high power factor is still for varying load and switching loss is very low.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.5
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• pp.434-441
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• 2016

This paper deals with transformer turns ratio design with the consideration of loss minimization in isolated bidirectional DC-DC converter. Generally, the rms value of current, magnitude of current at switching instance, and duty ratio of a converter vary according to the turns ratio of an isolation transformer in the converter under the same voltages and output power level. Therefore, the transformer turns ratio has an effect on the total loss in a converter. The switching and conduction losses of IGBTs and MOSFETs consisting of dual-active bridge converter are analyzed, and iron and copper losses in an isolation transformer and inductor are calculated. Total losses are calculated and measured in cases of four different transformer turns ratios through simulation and experiment with 3-kW converter, and an optimum turns ratio that provides minimum losses is found. The usefulness of the proposed transformer turns ratio design approach is verified through simulation and experimental results.