• Journal of Power Electronics
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• 제11권1호
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• pp.82-89
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• 2011

Differences in the frequency characteristic applied to a ripple current may shorten fuel cell life span and worsen the fuel efficiency. Therefore, this paper presents an experimental analysis of the ripple current applied variable frequency characteristic in a polymer electrolyte membrane fuel cell (PEMFC). This paper provides the first attempt to examine the impact of ripple current through immediate measurements on a single cell test. After cycling for hours at three frequencies, each polarization and impedance curve is obtained and compared with those of a fuel cell. Through experimental results, it can be absolutely concluded that low frequency ripple current leads to long-term degradation of a fuel cell. Three different PEMFC failures such as membrane dehydration, flooding and carbon monoxide (CO) poisoning that lead to an increase in the impedance magnitude at low frequencies are simply introduced.

• 전력전자학회논문지
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• 제22권5호
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• pp.449-456
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• 2017

This study proposes a method for compensating for the commutation torque ripple of delta-connected brushless DC motors with low inductance based on a current predictions. At the commutation instant, a phase current at the next sampling period is predicted and compared with the reference phase current to determine whether torque ripples will occur or not. If the predicted current cannot reach the reference phase current, the reference current is modified and the relevant voltage reference is produced to reduce the torque ripple. The validity of the proposed method has been verified by simulation and experimental results. The commutation torque ripple has been decreased by 17.7% at 1,000 rpm and 80% load conditions.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권9호
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• pp.490-497
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• 1999

This paper presents a novel current control method to reduce the current ripple due to commutation in brushless DC motor fed with unipolar PWM voltage source inverter. The proposed current control method can reduce the current ripple due to commutation in high speed range where the DC link voltage of the inverter is less than four times of the phase back-emf. The effectiveness of the proposed current control method is verified with digital simulations and experiments on the 250W brushless DC motor drive systems.

• 전기학회논문지
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• 제62권10호
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• pp.1425-1435
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• 2013

The useful method for determining parameters of weighting functions used to design the $H_{\infty}$ current controller for attenuating the current ripple due to saliencies which SPMSM(Surface Permanent Magnet Synchronous Motor) also incorporates is described. To analyze the effect, the current ripple due to the structural and the saturation saliencies, the SPMSM model with nonlinear inductance function depending on the two independent variables, rotor position and stator current is simulated. After analysis, parameters of the weighting functions for $H_{\infty}$ current controller is selected to satisfy the robust stability, robust performance and specific performance in time and frequency domain by using the PSO(Particle Swarm Optimization) algorithm in the linear SPMSM model. Especially, the robust performance is proved that the selected weighting functions play a role in reducing the current ripple caused by the saliencies of SPMSM at the desired frequency range by the simple experiment.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.575-578
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• 2003

This paper presents a new current control method to reduce torque ripple of Brushless DC Motor during commutation. In the proposed control strategy, the current slopes of rising and decaying phase during commutation is equalized by the compensation voltage. By adding the compensation voltage for it to the current controller output, the reduced torque ripple can be obtained. The simulation and experimental results show that the proposed method reduces the torque and the current ripples significantly.

• 한국전기전자재료학회논문지
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• 제25권1호
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• pp.53-57
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• 2012

In this paper, by designing 20 W class driving circuit for driving high-power LED (Light Emitting Diode), we are going to comparatively carry out the analysis of characteristics for power circuit according to each design method. In this case, 200 V 60 Hz was performed as input data. The electrical characteristics such as voltage, current and ripple are checked for constant current circuit and constant voltage circuit in the LED module. In addition, as the ripple has an influence on illumination of LED light, low temperature working (-20 [$^{\circ}C$]) and high temperature working(80 [$^{\circ}C$]) are measured to make sure the ripple characteristics in accordance with temperature. In low temperature operation -20 [$^{\circ}C$] measurements, both constant current circuit and constant-voltage circuit were less impacted on input fluctuation, whereas in the high temperature operation 80 [$^{\circ}C$], current voltage in constant voltage circuit was surge after 430 [hour]. Voltage current ripple of constant current circuit was much less than constant voltage circuit, therefore we can show that constant current circuit is more stable.

• 전기전자학회논문지
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• 제27권4호
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• pp.477-485
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• 2023

본 논문에서는 AC 리플이 리튬 이온 배터리의 수명에 미치는 영향을 실험적으로 분석한다. 에너지 저장 시스템(ESS)의 이용 효율을 높이기 위해 양방향 전력변환시스템(PCS)이 사용되며, 계통 연계 시 구조상 계통 주파수의 2배의 주파수를 갖는 전류 리플이 배터리에 인가되게 된다. 따라서, AC 리플이 Li-ion 배터리의 노화에 미치는 영향에 대해 분석하기 위해 DC 및 DC+AC 리플 사양의 충/방전 프로파일을 적용하여 노화 실험이 수행되었다. 실험 결과를 바탕으로 직류 내부 저항(DCIR), 증분 용량(IC), 표면 온도를 분석하였다. 결과적으로 AC 리플이 노화에 직접적으로 영향을 미치지 않으며 특정 주기 이 후 배터리 노화가 둔화되는 것을 확인하였다. 이러한 결과는 AC 리플이 발생하는 어플리케이션에서 전류 리플을 줄이기 위해 적용된 필터를 개선하는 데 도움이 될 수 있다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.142-145
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• 2001

In this paper the electromagnetic torque developed in IPMSM(Interior Permanent Magnet Synchronous Motor) is analyzed. If flux distributions in the motor are not sinusoidal, a sinusoidal current produces important torque ripple. Torque ripple causes vibration and noise of motors. The optimized current waveforms for ripple free is able to be obtained by analysis of Back-EMF and torque equation. The method to find the optimal current is based on numerical predetermination. In this paper proposes current waveform which can eliminate the torque ripple, and the validity is verified through the simulation.

• Journal of Magnetics
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• 제20권2호
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• pp.166-175
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• 2015

In this study, we describe the design method of a Brush-less DC (BLDC) motor with delta winding connection. After designing delta winding connection model with the $60^{\circ}$ flat-top region of the Back Electro-Motive Force (BEMF), an ideal current source analysis and a voltage source analysis, with a 6-step control, were conducted primarily employing Finite Element Method. In addition, as a current controller, we considered the Current Regulator with PI controller using Simulink for the comparison of torque characteristics. When the input current is controlled, the switching regions and reference signals are determined by means of the phase BEMF zero-crossing point. In reality, the input current variation depends on the inductance as well as input voltage, and it causes a torque ripple after all. Therefore, each control method considered in this research showed different torque ripple results. Based on the comparison, the causes of the torque ripple have been verified in detail.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 전력전자학술대회 논문집
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• pp.335-336
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• 2014

This paper investigates the design of coupled inductor for minimum inductor current ripple in rapid traction battery charger systems. Based on the general circuit model of coupled inductor together with the operating principles of dc-dc converter, the relationship between the ripple size of inductor current and the coupling factor is derived under the different duty ratio. The optimal coupling factor which corresponds to a minimum inductor ripple current becomes -1, i.e. a complete inverse coupling without leakage inductance, as the steady-state duty ratio operating point approaches 0.5. In an opposite manner, the optimal coupling factor value of zero, i.e. zero mutual inductance, is required when the steady-state duty ratio operating point approaches either zero or one. Coupled inductors having optimal coupling factor can minimize the ripple current of inductor and battery current resulting in a reliable and efficient operation of battery chargers.