• Journal of Power Electronics
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• v.16 no.3
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• pp.823-831
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• 2016

A high-efficiency method is proposed to suppress magnetic core imbalance in phase-shifted full-bridge (PSFB) converters. Compared with conventional solutions, such as controlling peak current mode (PCM) or adding DC blocking capacitance, the proposed method has several advantages, such as lower power loss and smaller size, because the additional current sensor or blocking capacitor is removed. A time domain model of the secondary side is built to analyze the relationship between transformer core imbalance and cathode voltage of secondary side rectifiers. An approximate control algorithm is designed to achieve asymmetric phase control, which reduces the effects of imbalance. A 60 V/15 A prototype is built to verify the proposed method. Experimental results show that the numerical difference of primary side peak currents between two adjacent cycles is suppressed from 2 A to approximately 0 A. Meanwhile, compared with the PCM solution, the efficiency of the PSFB converter is slightly improved from 93% to 93.2%.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.8
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• pp.120-129
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• 1998

In this paper represented uninterruptible power sypply(UPS) equipment maintaining constant output voltage, using a pulse width modulation(PWM) voltage fed inverter, as power source disconnection, voltage variation and output current variation with load variation. This system is driven by being synchronized voltage fed inverter and AC source, and in the steady state of power source charge battery connected to DC side with solar cell using a Photovoltaic (PV) that it was so called constant voltage charge. In addition, better output waveform was generated because of PWM(pulse width Modulation) method, and it was Proved to test by experiment maintained constant output voltage regardless of AC source disconnection, load variation, and voltage variation of AC power source.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1166-1177
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• 2014

A new type of topology with medium-frequency-transformer (MFT) isolation for medium voltage wind power generation systems is proposed in this paper. This type of converter is a high density power conversion system, with high performance features suitable for next generation wind power systems in either on-shore or off-shore applications. The proposed topology employs single-phase cascaded multi-level AC-AC converters on the grid side and three phase matrix converters on the generator side, which are interfaced by medium frequency transformers. This avoids DC-Link electrolytic capacitors and/or resonant L-C components in the power flow path thereby improving the power density and system reliability. Several configurations are given to fit different applications. The modulation and control strategy has been detailed. As two important part of the whole system, a novel single phase AC-AC converter topology with its reliable six-step switching technique and a novel symmetrical 11-segment modulation strategy for two stage matrix converter (TSMC) is proposed at the special situation of medium frequency chopping. The validity of the proposed concept has been verified by simulation results and experiment waveforms from a scaled down laboratory prototype.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.60-70
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• 2014

This paper discusses the impacts of large scale grid-connected wind farm equipped with permanent magnet synchronous generator (PMSG) on power system small signal stability (SSS) incorporating wind generation uncertainty and volatility. Firstly, a practical simplified PMSG model with rotor-flux-oriented control strategy applied is derived. In modeling PMSG generator side converter, the generator-voltage-oriented control strategy is utilized to implement the decoupled control of active and reactive power output. In modeling PMSG grid side converter, the grid-voltage-oriented control strategy is applied to realize the control of DC link voltage and the reactive power regulation. Based on the Weibull distribution of wind speed, the Monte Carlo simulation technique based is carried out on the IEEE 16-generator-68-bus test system as benchmark to study the impacts of wind generation uncertainty and volatility on small signal stability. Finally, some preliminary conclusions and comments are given.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.2
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• pp.29-37
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• 2006

Heavy chemical industries have nonlinear loads including elecrolyzers. AC-DC converters are the most widely used in an elecrolysis in a chemical plant. The electrolysis consists of AC-DC converter groups connected in parallel at the DC side. The converter operations cause harmonic currents and create distortions on the sinusoidal voltage of the AC power system. This paper provides an in depth analysis on harmonics field measurement for the electrolyzer loads and harmonics assessment by the international harmonic standards IEC 61000-3-6 and IEEE 519-1992.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.1119-1124
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• 2014

High temperature superconducting magnetic energy storage (HTS SMES) is known as an effective solution to significantly decrease the voltage and power fluctuations of grid connected wind power generation system (WPGS). This paper implements an effective control scheme of a back-toback converter with shunt-connected HTS SMES for the frequency regulation of an islanded microgrid. The back-to-back converter is used to connect the WPGS to the grid. A large-scale HTS SMES is linked to the DC side of the back-to-back converter through a two-quadrant DC/DC chopper. An adaptive control strategy is implemented for the back-to-back converter and the two-quadrant DC/DC chopper to improve the efficiency of the whole system. The performance of the proposed control system was evaluated in a test power system using PSCAD/EMTDC. The simulation results clearly show that the back-to-back converter with shunt-connected HTS SMES operates effectively with the proposed control strategy for stabilizing the power system frequency fluctuations.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.8
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• pp.102-108
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• 2005

In this paper, authors propose novel boost AC-DC converter of high power factor and analyze for waveform and harmonics component of input current. The input current waveform in the proposed converter is got to be a sinusoidal form of discontinuous pulse in proportion to magnitude of at input voltage under the constant duty cycle switching. Therefore, input power factor is nearly unity. Particularly, the stored energy of loss-less snubber capacitor is recovered with input side and increases input current from resonant operation. The result is that input power factor of the proposed converter is higher than that of conventional converter of high power factor. Some simulative results on computer and experimental results are included to confirm the validity of the analytical results.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.491-494
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• 1994

The 3-level inverter is applied to the induction motor drive as the voltage type inverter for large poller one. This inverter divides the DC link voltage into the two parts and it is supplied to the inverter. The 3-level inverter can reduces the voltage between the each devices, and get more sinusoidal current waveform. This paper presents the new PWM method which can reduces the harmonics. The modulation at the inverter side is implemented using a DSP microprocessor.

• Proceedings of the KIPE Conference
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• 2001.12a
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• pp.194-197
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• 2001

In this paper, the design method of LCL filter at the AC input side of a voltage fed active power filter is proposed. The characteristics of harmonics suppression and current control performance of active power filter are described using the analysis of the relation of these characteristics and DC voltage, switching frequency, and AC inductor values. The design examples are shown and the validity of the proposed design method is verified through the PSIM simulation.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1009-1011
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• 1992

This paper discribes a study on the bridge type power converter for laser high power generator with high frequency and high voltage using MOS-GTO. This converter effectively makes the best of the high frequency HV transformer and input-side equivalent parasitic capacitance of high voltage feeding cable in place of DC output smoothing filter. The cicuit configuration and performance are discussed and design criteria are given. The prototype rated of 10 KW, 100 KHz is implemented and experimental results are given.