• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.3
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• pp.231-235
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• 2008

Thyristor rectifiers are still the preferred choice for large magnet power supplies. However, large harmonic voltages, resulting in large current ripple, and slow dynamic response are major drawbacks of these converters. Joos presented a topology and a control technique for a hybrid large-power high-precision magnet power supply in 1996. The system consists of a phase controlled rectifier (PCR) connected in series with a high-frequency PWM converter. This paper improves the power circuit of the PWM converter using interphase transformer. Simulation result proves effect of the proposed system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.359-362
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• 2001

Phase shifter has been used as a means of power-flow control and for transient stability improvement in AC transmission system. Until now, phase shifters have been based on an injection transformer. Conventional phase shifters with tap changers require regular maintenance and allow only step-like control of the phase an81e. This paper propose a three-phase phase shifter using PWM AC/AC converter, which can improve system response and control stability in the applications. This paper deals with the circuit topology, operating principle so that the features of the phase shifter will be shown through computer simulation, especially using PSIM software.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1015-1019
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• 2001

This paper presents a novel three-phase current-fed Pulse Width Modulation converter with switched capacitor type resonant DC link commutation circuit operating PWM pattern strategy under a design consideration of low-pass filter, which can operate on the basis of the principle of zero current soft switching commutation. In the first place, the steady state operating principle of this converter with a new resonant DC link snubber circuit is described in connection with the equivalent operation circuit, together with the practical design procedure of the switched-capacitor type resonant DC link circuit is discussed from a theoretical viewpoint on the basis of a design example for high-power applications. The actively delayed time correction method to compensate distorted currents due to a relatively long resonant commutation time is newly implemented in the open loop control scheme so as to acquire the new optimum PWM pattern. Finally, the experiment of set-up in laboratory system of this converter is concretely demonstrated herein to confirm a zero current soft-switching commutation of this converter. The comparative evaluations between current-fed hard switching PWM and soft-switching PWM converters are carried out from a viewpoint of their PWM converter characteristics.

• Proceedings of the KIEE Conference
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• 2002.06a
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• pp.55-59
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• 2002

This paper presents a novel three-phase current-fed Pulse Width Modulation converter with switched capacitor type resonant DC link commutation circuit operating PWM pattern strategy under a design consideration of low-pass filter, which can operate on the basis of the principle of zero current soft switching commutation. In the first place, the steady state operating principle of this converter with a new resonant DC link snubber circuit is described in connection with the equivalent operation circuit, together with the practical design procedure of the switched-capacitor type resonant DC link circuit is discussed from a theoretical viewpoint on the basis of a design example for high-power applications. The actively delayed time correction method to compensate distorted currents due to a relatively long resonant commutation time is newly implemented in the open loop control scheme so as to acquire the new optimum PWM pattern. Finally, the experiment of set-up in laboratory system of this converter is concretely demonstrated herein to confirm a zero current soft-switching commutation of this converter. The comparative evaluations between current -fed hard switching PWM and soft-switching PWM converters are carried out from a viewpoint of their PWM converter characteristics.

• Journal of Power Electronics
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• v.12 no.1
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• pp.120-127
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• 2012

Fault diagnosis technique of electrical drives is becoming more and more important, since voltage fed converter system has become industrial standard in many applications. Many studies have been conducted an inverter fault diagnosis for induction motors. However, there are few researches about fault diagnosis of 3-phase ac/dc PWM (Pulse Width Modulation) converter compared to the dc/ ac inverter. The ac/dc converter is the opposite of dc/ac inverter at current flow. Also, inverter and converter have different current patterns under the same condition of IGBT (Insulated gate bipolar transistor) open switch fault. Therefore, it is difficult to apply intact diagnosis methods of inverter to the converter. This paper proposes modified fault detection methods for IGBT open switch fault in 3-phase ac/dc PWM converter by modifying established fault diagnostic methods for dc/ac inverters.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1116-1121
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• 2001

Phase shifter has been used as a means of power-flow control and for transient stability improvement in AC transmission system. Until now, phase shifters have been based on an injection transformer. Conventional phase shifters with tap changers require regular maintenance and allow only step-like control of the phase angle. This paper propose a three-phase phase shifter using PWM AC/AC converter, which can improve system response and control stability in the applications. This paper deals with the circuit topology, operating principle so that the features of the phase shifter will be shown through computer simulation, especially using PSIM software.

• Journal of Power Electronics
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• v.8 no.3
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• pp.201-209
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• 2008

This paper presents the modeling and design of a digital controller for a phase-shifted full-bridge converter (PSFBC) in a discrete-time domain. The discretized PSFBC model is first derived and then analyzed considering the sampling effect and the system parameters. Based on this model, the digital controller is directly designed in a discrete-time domain. The simulation and experimental results are provided to show the validity of the proposed modeling and controller design.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.2
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• pp.173-179
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• 2003

In this paper, a novel on-line dc capacitance estimation method for the three-phase PWM converter is proposed. At no load, input current at a low frequency is injected, which causes dc voltage ripple. With the at voltage and current ripple components of the dc side, the capacitance can be calculated. Experimental result shows that the estimation error is less than 2%.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.5
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• pp.370-379
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• 1989

This paper describes a three-phase active power filter using voltage-source PWM converter, which can eliminate the harmonics and compensate the reactive power in the ac sides of 6-pulse rectifier. The active filter consists of three-phase PWM inverter and a capacitor, and the hysteresis control technique is used to make the compensating current close to the existing harmonic current and also to improve the response of the filter with simple control circuit. As a result the compensated ac line current becomes sinusoidal and the input power factor is improved roughly to unity.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.3
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• pp.145-150
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• 2013

A novel AC to DC PWM converters with unity input power factor are proposed to overcome the above shortcoming. The main function of these converters is to shape the input line current to force it exactly in phase with the input AC voltage. Therefore, the input power factor can be improved to near unity and the input current harmonics can be eliminated. In this paper, half-bridge converter with two active switches and two diodes are utilized for low-cost type UPS configuration. By having only two semiconductors in the current path at any time, losses can be reduced over the conventional boost topology. Also, this converter provides controllable dc-link voltage, high power factor, and low cost type converter by simple power circuits. Simulation results show that the proposed half-bridge converter/inverter control technique can be applied to single-phase low-cost type UPS systems successfully.