• Journal of Power Electronics
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• v.18 no.3
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• pp.879-891
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• 2018

A bidirectional dc-dc converter is used in battery energy storage systems owing to the growing requirements of a charging and discharging mode of battery. The magnetic coupling of output or input inductors in parallel-connected multi modules of a bidirectional dc-dc converter is often utilized to reduce the peak-to-peak ripple size of the inductor current. This study proposes a novel design guideline to achieve minimal ripple size of the inductor current under bidirectional power flow. The newly proposed design guideline of optimized coupling factor is applicable to the buck and boost operation modes of a bidirectional dc-dc converter. Therefore, the coupling factor value of the coupled inductor does not have to be optimized separately for buck and boost operation modes. This new observation is explained using the theoretical model of coupled inductor and confirmed through simulation and experimental test.

• Journal of Power Electronics
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• v.19 no.3
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• pp.613-624
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• 2019

Digital current control techniques are an attractive option for DC-DC converters. In this paper, a digital predictive peak current control algorithm is presented for buck converters that allows the inductor current to track the reference current in two switching cycles. This control algorithm predicts the inductor current in a future period by sampling the input voltage, output voltage and inductor current of the current period, which overcomes the problem of hardware periodic delay. Under the premise of ensuring the stability of the system, the response speed is greatly improved. A real-time parameter identification method is also proposed to obtain the precision coefficient of the control algorithm when the inductance is changed. The combination of the two algorithms achieves adaptive tracking of the peak inductor current. The performance of the proposed algorithms is verified using simulations and experimental results. In addition, its performance is compared with that of a conventional proportional-integral (PI) algorithm.

• Journal of Electrical Engineering and Technology
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• v.8 no.5
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• pp.1086-1095
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• 2013

The main issue of parallel three-phase boost converters is reduction of the low- and high frequency circulating currents. Most present technologies concentrate on low frequency circulating current because the circulating current controller cannot mitigate the high frequency circulating current. In this paper, analytical approach of three-phase coupled inductor applied to parallel system becomes an important objective to effectively reduce the low- and high frequency circulating currents. The characteristics of three-phase coupled inductor based on a structure and voltage equations are mathematically derived. The modified voltage equations are then applied to parallel three-phase boost converters to develop averaged models in stationary coordinates and rotating coordinates. Based on the averaged modeling approach, design of the circulating current controller is presented. Simulation and experimental results demonstrate the effectiveness of the analysis and modeling for the parallel three-phase boost converters using three-phase coupled inductor.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.502-504
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• 2008

A new output inductor less phase shift full bridge converter with current reduction technique for server power application is proposed in this paper. The proposed converter can reduce the current stress by using the auxiliary circuit. Since the auxiliary circuit causes the additional resonance between the leakage inductor and auxiliary capacitor before the powering period, the proposed converter has lower current stress even no output filter inductor. Small size and circulating energy can be also the merits of the proposed converter. The operational principles and analysis are presented. Experimental results demonstrate that the current stress can be reduced effectively by using the auxiliary circuit without large output filter inductor.

• Journal of the Korea Society of Computer and Information
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• v.29 no.6
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• pp.143-151
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• 2024

In this paper, the inductor current distortion in a boost PFC (Power Factor Correction) converter under light load is mathematically analyzed, and its reasons are defined. In the average current mode control under light load, the inductor current is discontinuous, resulting in an inaccurate inductor current average value being reflected in the current control. In predictive current mode control, the current ripple is relatively large compared to the inductor current, leading to severe current distortion. In addition, the switch is turned off near the peak of the inductor current when model predictive current control is applied. Inductor current distortion must be addressed because it leads to an increase in total harmonic distortion and a decrease in power factor. In this paper, the design procedure to mitigate the light load current distortion in boost PFC converter is selected based on the mathematical analysis. Finally, a comparative analysis of control methods under light load is performed using hardware-in-the-loop simulation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.12
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• pp.9-16
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• 2010

In this paper, we have proposed a new dimmable magnetic ballast for HID(High Intensity Discharge) lamps consisted of AC switches to variate inductance value by using Silicon Controlled Rectifiers and the isolated zero current detector on inductor. Conventional dimming ballast has used relays or Solid State Relays in AC switches. However, a relay is difficult to zero current switching, because it has long operating time(10[ms]), and price competitiveness of SSR is very low. The proposed AC switches are suitable to switch at zero inductor current and it is accurately detected by using a opto-coupler. SCR is cheaper than SSR, and it is suitable to switch at zero inductor current because SCR is automatically turned off under holding current at no gate signal. Operating principles, simulation results and experimental results of the proposed ballast are described.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.4
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• pp.15-21
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• 2002

This paper presents parallel operation of ZVT(Zero Voltage Transition) FUll Bridge Converter with Dynamic Current Shared Inductor. In the conventional method, CT(Current Transformer) have been used tn share the load current equally with converters. In this system, at parallel operation of ZVT Full Bridge Converter, dynamic current shared inductor divides the same current of unit converter and ZVT circuit aids to high efficiency. Superiority of the characteristics is verified through the experiment with a 2[㎾], 50[㎑] prototype converter.

• Journal of Power Electronics
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• v.12 no.5
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• pp.715-722
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• 2012

New discrete time domain models for the peak current controlled (PCC) power LED drivers in continuous conduction mode include for the first time the effects of the time delay in the pulse-width-modulator. Realistic amounts of time delay are found to have significant effects on the average output LED current and on the critical inductor value at the boundary between the two conduction modes. Especially, the time delay can provide an accurate LED current for the PCC buck converter with a wide input voltage. The models can also predict the critical inductor value at the mode boundary as functions of the input voltage and the time delay. The overshoot of the peak inductor current due to the time delay results in the increase of the average output current and the reduction of the critical inductor value at the mode boundary in all converters. Experimental results are presented for the PCC buck LED driver with constant-frequency controller.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.330-331
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• 2011

The interleaving method is usually used to reduce the ripple of output current of filter inductor in parallel operation of PWM DC/DC converter. Although the current ripple of filter inductor decreases, each current ripple of filter inductor is not decreased. In this study, the operation of interleaved buck converter with coupled inductor is analyzed in each operation mode. It is verified through experiment. The possibility of application to grid connected inverter with parallel operation is identified.

• Journal of Power Electronics
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• v.14 no.5
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• pp.827-833
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• 2014

This study proposes a coupled inductor method for the parallel operation of a power conditioning system (PCS). When primary and secondary currents flow in the same direction in a coupled inductor, total flux and inductance are cancelled; when currents flow in opposite directions, each flux becomes an individual inductor. These characteristics are applied in the parallel operation of a PCS. To connect at a grid code, abnormal current, which is barred under the grid connection code, is blocked by using a coupled inductor. A design based on the capacity and current duration time of a PCS is verified through hardware implementation. Experiment results show the effectiveness of variance reduction.