• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.518-520
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• 1996

High frequency switching converters are becoming more popular because of several benefits which are essential in power conversion system. This paper introduces a high speed digital controller using TMS320C40 DSP chip which can be used for high frequency switching converters and demonstrates its performance by operating three-phase PWM AC/DC converter with unity power factor at 20kHz sampling frequency. TMS320C40 DSP chip operates with 40-ns instruction cycle times and is capable of 275 MOPS. The running time of real time control loop at the three-phase PWM AC/DC converter is $44.6{\mu}sec$.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1626-1634
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• 2015

LCL filters are widely used in three-phase PWM converter for its advantages of small volume, low cost and inhibition of high frequency current harmonic. However, it is difficult to optimize its design because its parameters are mutually influenced while the value of each parameter for LCL filter has impacts on the converter's cost and size. In this paper, the target of optimization is to minimize the parameter values of LCL filter, and an optimization method for parameters of LCL filter of three-phase PWM converter based on least square method is proposed. With this method, a quantitative calculation of the harmonic component of the converter’s side phase voltage is performed first, and then the quantitative relationship between phase voltage harmonics and grid phase current harmonics is analyzed. After that, the attenuation requirement of each harmonic is obtained by taking into account the requirements for each harmonic component of grid current. Then according to the optimization objective, the objective function with minimum harmonic attenuation deviation is established, and least squares method is adopted for three-dimensional global searching of parameters for LCL filter. Thus, the designed harmonic attenuation curve approximates the minimum attenuation requirements, and the optimized LCL filter parameters are obtained. Finally, the effectiveness of the method is verified by the experiments.

• 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 the Korean Institute of Telematics and Electronics S
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• v.34S no.11
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• pp.156-163
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• 1997

Recently, the three phase AC to DC boost converter has become one of the most widely used power converters as DC power source in the industry applications. In this paepr, a three phase PWM AC toDC boost converter that operates with unity power factor and sinusodial input currents is presented. The current control of the converter is based onthe predicted current control strategy with fixed switching frequency and the input current tracks the reference cuent within one sampling time interval. Therefore, by using this control strategy low ripples in the output voltage, low harmonics in the input current and fast dynamic responses are achieved with a small capacitance in the DC link.

• 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 the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.3
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• pp.96-106
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• 2007

The terminal voltage of a synchronous generator is maintained by the field current control of excitation system. Generally AC/DC converter which is component of AVR(Automatic Voltage Regulator) system for excitation current control is connected to diode rectifier and DC/DC converter system. In the case of diode rectifier system of phase controlled converter as AC/DC converter have low power factor and harmonics of lower order in the line current. In this paper, two stage three phase PWM AC/DC converter is studied to solve these problems. The characteristics of a proposed converter reduces the harmonics and reactive power of the distribution line and has fast dynamic response in transient period using boost converter and current control mode buck converts. The proposed method is verified by the computer simulation and experimental results in prototype generation system.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.2
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• pp.158-165
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• 2012

In this paper, the test bed using three-phase PWM converter connected with single phase inverter in series is set up to configure an active AC electric load. Since the two topologies, three-phase PWM converter and single-phase inverter, can be operated bidirectionally, the system not only re-generates surplus power to grid but also prevents power dissipation. However, the construction of system has a drawback. That is, ripple components two times of inverter operation frequency occur at DC-Link due to cascade connection, it can be cause of three phase unbalance Since the operational characteristic of the active AC electric load, the power frequency entered into the electric load can be varied, and the ripple of DC-Link is changed as well. In this paper, the three-phase PWM converter using a variable notch filter is proposed, and the reduction of three-phase current unbalance is presented. the validity of the proposed PWM converter using a variable notch filter is verified by the simulation and experimental results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.6
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• pp.1283-1290
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• 2003

Recently, PWM Buck AC-AC Converter is widely employed in various industrial applications such as voltage and power regulator, electronic transformer, phase shifter and so on. This paper presents static and dynamic modeling and complete characteristic analysis of a PWM Buck AC-AC converter. Firstly, the three phase converter system is modelled by using DQ transformation whereby we can obtain basic characteristic equations such as voltage gain and power factor as well as state equation and transfer function for control. Secondly, based on the analysis, the feedforward-feedback control technique is also proposed to obtain instantaneous duty level change whereby very fast dynamic response is achieved. Finally, the experimental results show the validity of the modeling, analysis and control.

• 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%.