• Journal of Power Electronics
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• v.8 no.2
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• pp.109-120
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• 2008

In this paper, a novel delta/double-fork transformer based 18-pulse full-wave AC-DC converter is designed, modeled, simulated and developed to feed isolated DC varying loads. The proposed AC-DC converter is used for low voltage and large current DC loads in applications such as electrowinning, where isolation is required mainly for stepping down the supply voltage. The proposed converter improves power quality at AC mains and meets IEEE-519 standard requirements at varying loads.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.5
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• pp.53-60
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• 2002

This paper presents exact autotransformer-fed AC electric railroad system modeling using constant current mode, and single-phase STATCOM(Static Synchronous Compensator) which has an effect on electric railroad system. An AC electric railroad is rapidly changing single-phase feeding electric power. To avoid voltage fluctuation under single phase loads, electric power should be received from a large source. The system modeling theory is based on the solution of algebraic. The AC electric railroad load model is nonlinear. Therefore this paper is considered nonlinear load using PSCAD/EMTDC. And the proposed modeling method is considered the line self-impedances and mutual-impedances that techniques for the AC electric railroad system modeling analysis, and that single-phase STATCOM can reliably compensate the voltage drop. In the case study, the allowance range of feeding voltage is 22.5∼27.5 kV, AT-fed AC electric railroad system circuit is analyzed by loop equation both normal and extension modes. The simulation objectives are to calculate the catenary and rail voltages with respect to ground, as the train moves along a section of line between two adjacent ATs. The results show that single-phase STATCOM can reduce the voltage drop in the feeding circuit and improve the power quality at AC electric railroad system by compensating the reactive power.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.6
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• pp.220-229
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• 2004

The AC railway system is quite differing from the general electric power system because it is single- phase and intermittently heavy loads. Thus, inevitably power quality problems are occurred in the AC railway system, i.e. voltage regulation voltage sags, voltage imbalance, and harmonic distortion. Recently, the power quality of the AC railway system becoming a hot issue because it is affect the control and safety of high-speed traction. In addition it is also affect the power quality of the electric power system. In this paper, single-phase Unified Power Quality Conditioner(UPQS) for the AC railway system is proposed to compensate the voltage sags and harmonic distortion. The configurations and control schemes of the proposed single-phase UPQC are presented. The effectiveness of the proposed single-phase UPQC application is verified by the PSCAD/EMTDC simulation works. It can be shown that the application of UPQC in the AC railway system is very useful to compensate the voltage sags and harmonic distortion from the results of related simulation works.

• Proceedings of the KIEE Conference
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• summer
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• pp.1232-1234
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• 2004

In this paper, we represent both occurrence reason of Surge-voltage and Leakage current of AC drive system which is operated by Voltage-type PWM Inverter. It generates a compensating voltage which has the same amplitude as, but the opposite phase to, the common-mode voltage produced by the PWM inverter. The compensating voltage is superimposed on the inverter output by a common-mode transformer. As a result, the common-mode voltage applied to the load is canceled completely. The design method of the active common-mode noise canceler is also presented in detail. Therefore, we try to describe the method controling both of them and all of the proprieties are proved by our experiment.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1414-1415
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• 2007

200 kV AC high voltage national standard system has been established with a purpose for support of heavy electrical industry. The system consists of high AC voltage source and regulating unit, the standard voltage transformer, voltage transformer comparator, and voltage transformer burden, and voltage transformer under test.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.749-753
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• 2003

This paper presents an output voltage regulation system using PWM Buck-Boost AC-AC converter for power qualify improvement of custom power. This paper proposes dynamic modeling of the system for control object and in addition, a controller design example. Therefore, system state equation is derived whereby the transfer function could be obtained. The paper shows a regulation controller for tracking the output voltage to the reference under specific operating point. Finally, this paper shows validity and practical applicability of the proposed modelling and system design by experimental results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.7
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• pp.1514-1519
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• 2003

This paper presents modeling and analysis of static and dynamic characteristics in three phase PWM Boost AC-AC converter used for input voltage sag compensation of custom power. Especially, using circuit DQ transformation technique, an equivalent circuit in fundamental frequency domain is obtained which has all the system characteristics. Moreover, voltage gain and input power factor is analytically induced and linearized state equation at the specific operating point is given. Finally, PSIM simulation results show the validity of the Nosed modelling and analyses.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.1
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• pp.72-83
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• 2013

The paper proposes a new multilevel variable output voltage AC/DC Converter for power supply of power amplifiers used in underwater acoustic sensors. The proposed multilevel variable output voltage AC/DC Converter is composed of two parts. One as the input section is the high efficiency phase-shifted PWM full bridge DC-DC converter to get multiport power sources. The other as the output section is composed of two flying-capacitor 3-level DC-DC converters and a diode bridge circuit to get fast-response and multilevel variable output voltage for an envelope amplifier. Also the paper suggests the detailed circuit topology and design guideline of multilevel variable output voltage AC/DC converter. It also proposes the power balanced control method between 3-level converters and the voltage balanced algorithm for flying capacitors. Its characteristics should be verified by the detailed simulation results. It is anticipated that the proposed converter will be used very well for power amplifiers used in underwater acoustic sensors.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1293-1302
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• 2014

A flyback inverter using voltage sensorless maximum power point tracking (MPPT) for photovoltaic (PV) AC modules is presented. PV AC modules for a power rating from 150 W to 300 W are generally required for their small size and low price because of the installation on the back side of PV modules. In the conventional MPPT technique for PV AC modules, sensors for detecting PV voltage and PV current are required to calculate the PV output power. However, system size and cost increase when the voltage sensor and current sensor are used because of the addition of the auxiliary circuit for the sensors. The proposed method uses only the current sensor to track the MPP point. Therefore, the proposed control method overcomes drawbacks of the conventional control method. Theoretical analysis, simulation, and experiment are performed to verify the proposed control method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.8
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• pp.1422-1428
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• 2008

In the current PDP technology, one of the most important issues in AC PDP is improvement of luminance and luminous efficacy. To improve luminance and luminous efficacy, new cell structure of PDP containing long discharge path is necessary. However, it causes an increment of firing voltage. In order to decrease firing voltage of AC PDP having long discharge gap, the protrusion electrode is proposed. To drop the firing voltage, the protrusion electrode is inserted into the forward area of the main discharge gap. This paper presents measurements of detailed optical and electrical characteristics of AC PDP with protrusion electrodes. The experimental results show that the proposed structure with gap 80um has lower firing voltage to 27V than that of the conventional long gap structure. Moreover, the ICCD(Intensified Charge Coupled Device) images of the proposed structure show quick discharge generation by 0.07usec and longer continuation by 0.05usec than that of the conventional long gap structure. Therefore, the proposed protrusion electrodes have higher luminance by 12.5% than that of the conventional structure, as having no decrement of Luminous efficacy.