• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.2
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• pp.106-117
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• 2022

Multiple output converters can be utilized when various output voltages are required in applications. Recently, one of the multiple output converters called fly-buck has been proposed, and has attracted attention due to the advantage that multiple output can be easily obtained with a simple structure. When constant on-time (COT) control is applied, the output ripple voltage must be treated carefully for control stability and voltage regulation characteristics in consideration of the inherent energy transfer characteristics of the fly-buck converter. This study analyzes the operation principle of the fly-buck converter with a ripple generation network and presents the design guideline for the improved output voltage regulation. Validity of the analysis and design guideline is verified using a 5 W prototype of the COT controlled fly-buck converter with a ripple generation network for telecommunication auxiliary power supply.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1833-1842
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• 2016

In grid-connected converter control, grid voltage feedforward is usually introduced to suppress the influence of grid voltage distortion on the converter's grid-side AC current. However, owing to the time-delay in control systems, the suppression effect of the grid voltage distortion is seriously affected. In this paper, the positive effects of the grid voltage feedforward control are analyzed in detail, and the time-delay caused by the low-pass filter (LPF) in the voltage filtering circuits and digital control are summarized. In order to reduce the time-delay effect on the performance of the feedforward control, a voltage feedforward control strategy with time-delay compensation is proposed, in which, a leading correction of the feedforward voltage is used. The optimal leading step used in this strategy is derived from analyzing the phase-frequency characteristics of a LPF and the implementation of digital control. By using the optimal leading step, the delay in the feedforward path can be further counteracted so that the performance of the feedforward control in terms of suppressing the influence of grid voltage distortion on the converter output current can be improved. The validity of the proposed method is verified through simulation and experiment results.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.2
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• pp.149-156
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• 2014

This paper proposes the battery charging algorithm for small-scale wind power generator using three phase PWM converter. it is impossible to control output power of the converter in over wind speed region since back EMF of PMSG is higer than battery voltage. Therefore, battery charging algorithm is proposed to expand battery charging over wind speed region. The suggested method is using the q-axis current for battery charging in the rated wind speed region. In the over wind speed region after it lower back EMF of PMSG using d-axis current it can control output power of the converter. The validity of the proposed algorithm are verified by experiments.

• Journal of Advanced Marine Engineering and Technology
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• v.16 no.4
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• pp.102-112
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• 1992

The three-phase full(6-pulse) bridge controlled rectifier is one of the most widely used types of solid-state converters in DC drive applications for higher performance. In most of the previous designs, the gate control circuits of the converter have been designed with analog method which can be easily affected by noise. Nowdays with advances of microelectronics and power electronics, microprocessor and pheripal LSIs are increasingly used for eliminating this problems. In this paper, a novel general-purpose microprocessor -based firing system and control scheme for a three-phase controlled rectifier bridge has been developed and tested. Using the phase relations between ${\Delta}$-Y transformer in power operation part, gate pulse of the converter is generated with real time process so that microprocessor may share its time to control algorithms efficiently. The firing angle of the converter is smoothly controlled in the range of 0 $^{\dirc}$ to 180$^{\dirc}$ with a fast respone and a constant open loop gain, even for the case where the converter is fed by a weak AC system of unregulated frequency. The hardware and software control circuit implementation built around a 80286 microprocessor is discussed, and the experimental results are given. This scheme uses less hardware components and has higher dynamic performance in variable speed DC drive applications.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.8
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• pp.90-97
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• 2014

This paper presents a compensation method of unbalanced phase currents in interleaved bi-directional converters. Phase currents in interleaved bi-directional converter are apt to be unbalanced due to circuit parameter error and switch operation difference. This problem causes the switch element failure and the reduced efficiency of the converter. Therefore, it is necessary that a certain balance control algorithm is provided in interleaved bi-directional converter system. In this paper, a balance control algorithm based on the circular chain control method is proposed. Further, in order to reduce the number of phase current sensors, this paper shows a simple method in which phase currents can be extracted indirectly through a DC-link current sensor in both charging and discharging modes. The validity and the effectiveness of the proposed phase currents balance control algorithm are illustrated through the simulation results.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.240-243
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• 2001

This paper presents the digital controller using variable gain for single-phase power factor correction (PFC) converter. Generally, the gain of inner current control loop in single-stage PFC converter has a constant magnitude. This is why input current is distorted under low input voltage. In particular, a digital controller has more time delay than an analog controller which degrades characteristics of control loop. So, it causes the problem that the gain of current control loop isn't increased enough. In addition, the oscillation happens in the peak value of the input voltage open loop PFC system gain changes according to ac input voltage. These aspects make the design of the digital PFC controller difficult. In this paper, the improved digital control method for single-phase power factor converter is presented. The variable gain according to input voltage and input current help to improve current shape. The 800W converter is manufactured to verify the proposed control method.

• Journal of Magnetics
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• v.21 no.4
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• pp.644-651
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• 2016

A novel zero voltage switching (ZVS) phase shift full bridge (PSFB) converter used in geophysical exploration is proposed in this paper. To extend the ZVS ranges and increase power density of the converter, external inductor acting as leakage inductance is applied and integrated into the integrated magnetic (IM) transformer with separated secondary winding. Moreover, the loss of ZVS PSFB converter is also decreased. Besides, the analysis and accurate prediction methodology of the leakage inductance of the IM transformer are proposed, which are based on magnetic energy and Lebedev. Finally, to verify the accuracy of analysis and methodology, the experimental and finite element analysis (FEA) results of IM transformer and 40 kW converter prototypes are given.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.470-475
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• 2002

Instantaneous following PWM control technique is pulsed nonlinear dynamic control method. This new control technique using analog integrator is proposed to control the duty ratio D of do-dc converter. In this control method, the duty ratio of a switch is exactly equal In or proportional to the control reference in the steady state or in a transient. Proposed control method compensates power source perturbation in one switching cycle, and the average value of the dynamic reference in one switching cycle. There is no steady state error nor dynamic error between the control reference and the average value of the switched variable. Experiments with buck converter have demonstrated the robustness of the control method and verified theoretical prediction. The control method is very general and applicable to all type PWM

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05a
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• pp.103-105
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• 2002

Instantaneous following PWM control technique is pulsed nonlinear dynamic control method. This new control technique using analog integrator is proposed to control the duty ratio D of Cuk converter. In this control method, the duty ratio of a switch is exactly equal to or proportional to the control reference in the steady state or in a transient. Proposed control method compensates power source perturbation in one switching cycle, and the average value of the dynamic reference in one switching cycle. There is no steady state error nor dynamic error between the control reference and the average value of the switched variable. Experiments with Cuk converter have demonstrated the robustness of the control method and verified theoretical prediction. The control method is very general and applicable to all type PWM.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.3
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• pp.231-239
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• 2017

A novel current control technique with fast response and application in an unbalanced system is proposed in this paper. Contrary to the conventional PI and dead-beat current control techniques, the proposed method is adopted to the valley current mode control (VCMC) and average current mode control (ACMC) methods to overcome the phase delay caused by conventional methods. The advantages of the proposed system are simplicity of structure and ease of implementation. The VCMC and ACMC methods are established and applied to the buck converter, boost converter, three-phase PWM converter, and three-phase inverter. The control performances of the proposed systems are shown by computer simulations and verified by experimental results.