• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.960-961
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• 2006

In this paper, a static var compensator using three phase PWM Watkins-Johnson AC-AC converter is presented. The PWM Watkins-Johnson AC-AC converter is modelled by using circuit DQ transformation whereby the basic DC characteristics equation is analytically obtained. Finally, the PSIM simulation shows the validity of the modelling and analysis.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.116-118
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• 2005

In this paper, a three phase PWM noninverting Buck-Boost AC-AC converter for WCF applications is presented. The PWM noninverting Buck-Boost AC-AC converter is modelled by using vector DQ transformation whereby the basic DC characteristics equation is analytically obtained. Finally, the PSIM simulation shows the validity of the modelling and analysis.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.119-121
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• 2005

In this paper, a three phase PWM Watkins-Johnson AC-AC converter for VVCF applications is presented. The PWM Watkins-Johnson AC-AC converter is modelled by using vector DQ transformation whereby the basic DC characteristics equation is analytically obtained. Finally, the PSIM simulation shows the validity of the modelling and analysis.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.122-124
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• 2005

In this paper, a three phase PWM Zeta AC-AC converter for VVCF applications is presented. The PWM Zeta AC-AC converter is modelled by using vector DQ transformation whereby the basic DC characteristics equation is analytically obtained. Finally, the PSIM simulation shows the validity of the modelling and analysis.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.8
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• pp.1544-1550
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• 2009

In this paper, a new single phase voltage sag/swell compensator using direct power conversion is proposed. A new compensator consists of input/output filter, series transformer and direct ac-ac converter, which is a single-phase back-to-back PWM converter without dc-link capacitors. Advantages of the proposed compensator include: simple power circuit by eliminating dc link electrolytic capacitors and thereby, improved reliability and increased life time of the entire compensator; simple PWM strategy or compensating voltage sag/swell at the same time and reduced switching losses in the ac-ac converter. Further, the proposed scheme is able to adopt simple switch commutation method without requiring complex four-step commutation method that is commonly employed in the direct power conversion. Simulation and experimental results are shown to demonstrate the advantages of the new compensator and PWM strategy. A 220V, 3kVA single-phase compensator based on the digital signal processor controller is built and tested.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.6
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• pp.496-503
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• 2009

In this paper, a new three-phase interleaved isolated high efficiency boost dc-dc converter with active clamp is proposed. The converter is capable of increased power transfer due to its three-phase power configuration, and it reduces the rms current per phase, thus reducing conduction losses. Further, interleaved operation of three-phase boost converter reduces overall ripple current, which is imposed into fuel cells and realizes smaller sized filter components, increasing effective operating frequency and leading to higher power density. Each output current of three-phase boost converter is combined by the three-phase transformer and flows in the continuous conduction mode by the proposed three-phase PWM strategy. An efficiency of above 96% is mainly achieved by reducing conduction losses and switching losses are reduced by the action of active clamp branches, as well. The proposed converter and three-phase PWM strategy are analyzed, simulated and implemented in hardware. Experimental results are obtained on a 500 W prototype unit, with all of the design verified and analyzed.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.52 no.2
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• pp.49-55
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• 2003

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 the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.105-112
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• 2003

Diode rectifier which can't be controlled output voltage and phase control converter as AC/DC converter have low power factor and harmonics of lower order in the line current. In this paper, three phase PWM(Pulse Width Modulation) AC/DC boost converter is studied to solve these problems. The characteristics of a proposed converter are to control the phase of current without current sensor as a very simple control algorithm using circuit parameters only and to apply sinusoidal PWM method with fixed switching frequency due to a difficult design of input filter and switching device. We simulate for the proposed algorithm that high power factor is achieved and DC link voltage has fast dynamic response without ripple in rectifying and regenerating operation. As a result of experiment with circuit parameter(inductor, capacitor) decided in simulation, the proposed converter had high power factor and reduction of low order harmonics as against diode rectifier.

• Journal of Power Electronics
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• v.3 no.4
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• pp.249-258
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• 2003

This paper presents a high-efficient and cost effective three-phase AC/DC-DC/AC power conversion system with a single two-switch type active Auxiliary Resonant DC Link (ARDCL) snubber circuit, which can minimize the total power dissipation. The active ARDCL snubber circuit is proposed in this paper and its unique features are described. Its operation principle in steady-state is discussed for the three phase AC/DC-DC/AC converter, which is composed of PWM rectifier as power factor correction (PFC) converter, sinewave PWM inverter. In the presented power converter system not only three-phase AC/DC PWM rectifier but also three-phase DC/AC inverter can achieve the stable ZVS commutation for all the power semiconductor devices. It is proved that the proposed three-phase AC/DC-DC/AC converter system is more effective and acceptable than the previous from the cost viewpoint and high efficient consideration. In addition, the proposed two-switch type active auxiliary ARDCL snubber circuit can reduce the peak value of the resonant inductor injection current in order to maximize total system actual efficiency by using the improved DSP based control scheme. Moreover the proposed active auxiliary two-switch ARDCL snubber circuit has the merit so that there is no need to use any sensing devices to detect the voltage and current in the ARDCL sunbber circuit for realizing soft-switching operation. This three-phase AC/DC-DC/AC converter system developed for UPS can achieve the 1.8% higher efficiency and 20dB lower conduction noise than those of the conventional three-phase hard-switching PWM AC/DC-DC/AC converter system. It is proved that actual efficiency of the proposed three-phase AC/DC-DC/AC converter system operating under a condition of soft switching is 88.7% under 10kw output power.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.6
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• pp.530-537
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• 2016

This work deals with a switching method for minimizing overcurrent in a three-phase interleaved bidirectional DC-DC converter with frequency modulation. Generally, a three-phase interleaved DC-DC converter is used to reduce a current ripple component. The combined operation of three-phase and two-phase converters can significantly reduce the ripple component. However, the conventional PWM method cannot solve severe overcurrent during phase transfer or frequency variation for power control. To overcome this problem, this work proposes a new PWM switching method. A 3 kW DC-DC power converter is designed and implemented, and the converter is operated in discontinuous current mode with varying switching frequencies for power control. Simulation and experimental results show the validity of the proposed switching method. The proposed switching method can be widely used in the field of current ripple reduction for three-phase interleaved bidirectional DC-DC converters.