• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.122-125
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• 1999

The AC-to-DC single-phase PWM rectifier for traction applications using high power semiconductor, IGCT is made and tested. Parallel operation of two PWM converter is adopted for increasing capacity of converters. For reducing harmonics, the harmonic content is eliminated by the phase shift between two converters switching phase. The output voltage control is achieved by interns calculation without detecting the input current. The part of PLL used for controlling power factor is simply implemented by software.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.576-580
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• 2001

This paper presents a casca multilevel PWM rectifier without the isolation transformers for energy build-up at each inverter modules; The features and advantages of the proposed PWM rectifier can be summarized as follows; 1) It realizes the high power high voltage AC/DC power conversion, 2) It uses no transformer which is bulky and heavy, 3) It has hybrid structure so that switching devices can be effectively utilized, 4) It produces high quality AC current even in high power high voltage applications, 5) The input power factor remains unity by simple modulation index control. The multilevel rectifier is analyzed by using the circuit DQ transformation whereby the characteristics and control equations are obtained. Finally, it will be shown that the system simulation reveals the validity of analyses

• Journal of Industrial Technology
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• v.18
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• pp.323-328
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• 1998

A current controlled VSI-PWM rectifier and inverter with capacitor dc link is regarded as one of the most promising structures for three-phase to three-phase to three-phase power conversion. This type of converter normally requires twelve switches for a rectifier and inverter composed of self turn-off switch such as a bi-polar transistor or IGBT with an anti-parallel diode. In this paper, a new three-phase to three-phase converter for ac motor drives is proposed. The proposed converter employs only eight switches and has the capability of delivering sinusoidal input currents with unity power factor and bidirectional power flow. This paper describes the feasibility and the operational limitations of the proposed structure. A mathematical model of the system is derived using generalized modulation theory and experimental results for steady state and dynamic behavior are presented to verify the developed model.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.280-287
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• 2015

Three-level PWM rectifiers applied in medium voltage applications usually operate at low switching frequency to keep the dynamic losses under permitted level. However, low switching frequency brings a heavy cross-coupling between the current components $i_d$ and $i_q$ with a poor dynamic system performance and a harmonic distortion in the grid-connecting current. To overcome these problems, a mathematical model based on complex variables of the three-level voltage source PWM rectifier is firstly established, and the reasons of above issues resulted from low switching frequency have been analyzed using modern control theory. Then, a novel control strategy suitable for the current decoupling control based on the complex variables for $i_d$ and $i_q$ is designed here. The comparisons between this kind of control strategy and the normal PI method have been carried out. MATLAB and experimental results are given in detail.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1212-1213
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• 2011

PWM(pulse width modulation) rectifier has unit power factor and low harmonic distortion with high power conversion efficiency in entire loading range. These merits of PWM rectifier help the spread of DC distribution system. In addition, if multiple PWM rectifiers can be operated in parallel connection, maintenance process can be simple and reliability of power source can be advanced because of the hot swapping is available. The other way, the load unbalance among rectifiers can force a converter to stop by over current. The surge current by closed circuit composition between rectifiers can force switching devices damage. In this paper, some problems that can occur in case of parallel operation of PWM rectifiers and problem eliminating methods are considered.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.10a
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• pp.573-576
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• 2000

In this paper, analysis of operating characteristics of hybrid cascade multilevel PWM rectifier without bulky and heavy isolation transformers is presented. The multilevel PWM rectifier is analyzed by using the circuit DQ transformation whereby the static and dynamic characteristics and some useful design relationships are obtained. Then, the operating characteristics such as active/reactive power relationships with respect to control variables, DC voltages build up are presented. It will be shown that the DC voltages for the multilevel output generation may be directly built up from AC utility source. Finally, to confirm the validity of the analysis, MATLAB simulations are tarried out.

• 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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2722-2728
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• 2011

3Phase PWM rectifier has become increasingly popular due to its capability of nearly sinusoidal waveform of the input current, and nearly unity power factor operation as a AC/DC rectifier of high capacity telecommunication power supply system. Generally, PI controller is used as a voltage controller of PWM rectifier and voltage controller must be designed to have low overshoot in transient state to get a reliability and stable operation. However, in the application of telecommunication in which load condition is varied very fast, the voltage controller must have a large bandwidth to reduce output voltage variation. The PI controller with large bandwidth arouse the excessive overshoot of the output voltage, and this large output voltage variation degrades the reliability of communication power of the three-phase PWM Rectifier. In this paper, new IP voltage controller for 3 phase PWM rectifier is proposed which has relatively low transient output voltage variation. The improved output characteristics of the transient state voltage responses of the starting and at load changes of the proposed voltage controller are proved by simulations and experiments.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.1
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• pp.34-40
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• 2006

This paper proposed power system for new DC 49[V] telecommunication using forward three-phase PWM rectifier power factor and efficiency for improvement of ripple voltage. Proposed power system for DC 48[V] telecommunication that consists of power conversion devices including switch, inductor and condenser were made between each line, in power inverter device of each switch control turn-on in period of continuity time control to get power factor '1' of sine wave current and on-off of switch lessens peak current that was happened and got conversion efficiency 92.1[%] composing in PWM rectifier of forward form instead of general PWM rectifier. Also, harmonic input regulation value(IEC61000-3-2 Class-As) satisfy input current and reduce ripple factor of output voltage in state that distortion of three-phase supply is overlapped each other.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1119-1122
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• 1992

This paper deals with a novel method of modeling and analyzing multilevel pulse width modulation(PWM) inverter/rectifier, which leads to extraction of equivalent circuit in fundamental frequency domain. By the technique, we can draw out the corresponding linear time invariant circuit even thuogh the actual circuit is switched. A static VAR compensator using five-level inverter is modeled and simulated for the verification of the modeling.