• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.6
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• pp.551-554
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• 2017

This paper proposes a three-level LLC resonant converter using integrated magnetics (IM). Given that the switch voltage stress of the proposed converter is guaranteed to be half of the input voltage, the switching losses can be greatly reduced, thereby benefitting the high-frequency operation. To reduce the volume of reactive components such as transformers, high-frequency driving and planar core are applied. However, two resonant inductors and one transformer are required because of the three-level structure and the limited leakage inductance of the planar transformer for the resonant operation. Therefore, the effect of volume reduction is not very large. In order to solve these drawbacks, this paper proposes a new IM that integrates all magnetic elements used in the proposed three-level resonant converter by using the magnetizing inductor as a resonant inductor. The experimental results are presented by conducting a theoretical analysis of a prototype with 350 W to 800 kHz.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.611-614
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• 1991

In variable speed driving system of three phase induction motor controlled by an inverter, because of the switching of semiconductor devices in inverter, an appreciable amount of harmonic components of voltage waveform can cause the motor to generate losses, torque ripple, acoustic noise and oscillation of semiconductor devices. In this paper a new PAM type PWM inverter using IGBT is described. The output waveforms in the proposed PAM type PWM inverter are investigated both theoretiically and experimentally. The line-voltage waveform is composed of fundamental component and the sidebands of carrier frequency. The lower order harmonics are not included in the output wave form. As each inverter arm does not operate during two-thirds period, the heats, generated in the devices are reduced. That is, the size of the inverter system can he minimized because of the reduction in the heat dissipating equipment.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1524-1532
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• 2015

Conventional space vector pulse width modulation based asymmetrical dual inverter configuration produces high common mode voltage (CMV) variations. This CMV causes the flow of common mode current, which adversely affects the motor bearings and electromagnetic interference of nearby electronic systems. In this study, a simple and generalized carrier based pulse width modulation (PWM) technique is proposed for dual inverter configuration. This simple approach generates various continuous and discontinuous modulating signals based PWM algorithms. With the application of the discontinuous modulating signal based PWM algorithm to the asymmetrical dual inverter configuration, the CMV can be reduced with a slightly improved quality of output voltage. The performance of the continuous and discontinuous modulating signals based PWM algorithms is explored through both theoretical and experimental studies. Results show that the discontinuous modulating signal based PWM algorithm efficiently reduces the CMV and switching losses.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.1096-1099
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• 2001

The basic design structure of RC-GCTs (Reserve-Conducting Gate-Commutated Thyristors) is firstly given in this paper. The bulk of wafer is punch-through (PT) type with high resistivity and narrow N-base width. The photo-mask was designed upon the turn-off characteristics of GCT and solution of separation between GCT and diode part. The center part of Si wafer is free-wheeling diode (FWD) and outer is GCT part which has 240 fingers totally. The switching performance of GCT was investigated by Dessis of ISE. The basic manufacture process of 2500V-4500V RC-GCTs was given in this work. Additionally, the local carrier lifetime control by 5Mev proton irradiation was adopted so as to not only to have the softness of reverse recovering for FWD but for reduction of turn-off losses of GCT as well.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.587-590
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• 2003

The first attention in designing a transformer for low temperature rise should be to reduce losses. Leakage inductance and temperature rise are two of the more impotent problems facing the magnetic core technology of today's high frequency transformers. Excessive leakage inductance increases the stress on the switching transistors and limits the duty-cycle, and excessive temperature rise can lead the design limitation of high frequency transformer with high current. The flat transformer technology provides a very good solution to the problems of leakage inductance and thermal management for high frequency power. The critical magnetic components and windings are optimized and packaged within a completely assembled module. The turns ratio in a flat transformer is determined as the product of the number of elements or modules times the number of primary turns. The leakage inductance increase proportionately to the number of elements, but since it is reduced as the square of the turns, the net reduction can be very significant. The flat transformer modules use cores which have no gap. This eliminates fringing fluxes and stray flux outside of the core. The secondary windings are formed of flat metal and are bonded to the inside surface of the core. The secondary winding thus surrounds the primary winding, so nearly all of the flux is captured.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.5
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• pp.96-104
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• 2004

This paper proposes a dc power regenerating systems, which can generate the excessive dc power from dc bus line to ac supply in substations for traction system The proposed regeneration inverter system for dc traction can be used as both an inverter and an active power filter(APF). As an regeneration inverter mode, it can recycle regenerative energy caused by decelerating tractions and as an active power filter mode, it can compensate for harmonic distortion produced by the rectifier substation. From the viewpoint of both power capacity and switching losses, the system is designed on the basis of three phase PWM inverters and composed of parallel inverters, output transformers, and an LCL filter.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1609-1618
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• 2015

DC microgrids are considered as prospective systems because of their easy connection of distributed energy resources (DERs) and electric vehicles (EVs), reduction of conversion loss between dc output sources and loads, lack of reactive power issues, etc. These features make them very suitable for future industrial and commercial buildings' power systems. In addition, the bipolar-type dc system structure is more popular, because it provides two voltage levels for different power converters and loads. To keep voltage balanced in such a dc system, a bidirectional dual buck-boost voltage balancer with direct coupling is introduced based on P-cell and N-cell concepts. This results in greatly enhanced system reliability thanks to no shoot-through problems and lower switching losses with the help of power MOSFETs. In order to increase system efficiency and reliability, a novel burst-mode control strategy is proposed for the dual buck-boost voltage balancer. The basic operating principle, the current relations, and a small-signal model of the voltage balancer are analyzed under the burst-mode control scheme in detail. Finally, simulation experiments are performed and a laboratory unit with a 5kW unbalanced ability is constructed to verify the viability of the bidirectional dual buck-boost voltage balancer under the proposed burst-mode control scheme in low-voltage bipolar-type dc microgrids.