• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.1
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• pp.46-52
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• 2021

This study proposes a feedforward compensation control method to reduce 120 Hz output voltage ripple in a single-phase AC/DC rectifier system composed of PFC and LLC resonant converters. The proposed method compensates for the voltage ripple of the DC-link by using the AC input and DC output power difference, and then reduces the final output voltage ripple component of 120 Hz through feedforward compensation based on the linearized frequency gain curve of the LLC resonant converter. Through simulation and experimental results, the validity of the ripple reduction performance was verified by comparing the conventional PI controller and the proposed feedforward compensation method.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.1
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• pp.110-116
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• 2013

This paper proposes a current ripple reduction method to improve the control performance of B4 type inverter that is studied for cost-effective drive systems. B4 inverters employ only four switches and they have a center-tapped connection between the split dc-link capacitors and one phase of a three-phase motor or load. In the B4 topology, unbalanced three-phase voltages will be generated due to the dc-link voltage ripple. To solve this problem, this paper presents a voltage distortion compensation method that adjusts the voltage reference with the consideration of dc-link voltage ripple. The validity of the proposed method is verified by simulation and excremental results with an induction machine.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.317-320
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• 2000

This paper proposes a voltage compensation method to improve the control performance of B4 inverter which is studied for low-cost drive systems. The B4 inverter employs only four switches and it has a center-tapped connection in the split dc-link capacitors to one phase of a three-phase motor. In the B4 topology unbalan-cd three-phase voltages will be generated by the dc link voltage ripple. To solve this problem we present a voltage compensation method which adjusts switching times considering dc link voltage ripple. The proposed method is verified by simulation results,

• Journal of Power Electronics
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• v.10 no.3
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• pp.328-333
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• 2010

A photovoltaic power conditioning system (PV PCS) that contains single-phase dc/ac inverters tends to draw an ac ripple current at twice the output frequency. Such a ripple current perturbs the operating points of solar cells continuously and it may reduce the efficiency of the current based maximum power point tracking technique (CMPPT). In this paper, the ripple current generation in a dc link and boost inductor is analyzed using the ac equivalent circuit of a dc/dc boost converter. A new feed-forward ripple current compensation method to incorporate a current control loop into a dc/dc converter for ripple reduction is proposed. The proposed feed-forward compensation method is verified by simulation and experimental results. These results show a 41.8 % reduction in the peak-to peak ac ripple. In addition, the dc/ac inverter control system uses an automatic voltage regulation (AVR) function to mitigate the ac ripple voltage effect in the dc link. A 3kW PV PCS prototype has been built and its experimental results are given to verify the effectiveness of the proposed method.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.109-117
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• 2004

This paper presents a current control strategy to reduce torque ripple of Brushless DC Motor in commutation period with PWM pattern. The torque ripple is mainly caused by the inequality in the rate of change between rising current and decaying one during commutation. And also it is influenced by the shape of real back EMF. Therefore, in the proposed control strategy, considering real back EMF a compensation voltage is generated to equalize the rate of change in these commutating currents. And then, by providing the compensation voltage in commutation period with PWM pattern, the torque ripple can be reduced. The simulation and experimental results verify that the proposed method can reduce the torque and the current ripples significantly.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.1
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• pp.47-53
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• 2006

In this paper, a simple scheme compensating for the effect of dc-link ripple voltages on output voltage of two-leg and three-phase PWM inverters is proposed, where single-phase half-bridge PWM convertor and two-leg inverter are used. The voltage at neutral point of the dc-link is controlled so that the upper-half of do-link voltage is equal to the lower-half voltage in average concept. However, the effect of the do-link ripple voltage results in the inverter output voltage and current distortion. This effect can be eliminated by introducing a compensation voltage in switching time calculation. Also, the inverter dead time should be compensated for sinusoidal output waveform. The proposed scheme has been verified by experimental results which were obtained from the V/F constant operation of the induction motor fed by two-leg inverter.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.4
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• pp.8-15
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• 2013

This paper proposes a DC-link voltage variation compensation method for a 3-level single phase converter for high-speed trains. Since 3-level NPC(Neutral Point Clamped) type converters have the split DC-link causing the inherent problem of voltage fluctuations in the upper and lower capacitors, reducing the voltage difference between the top and bottom capacitors is required. In this paper, compensation time proportional to the voltage difference is added to PWM switching time to solve the voltage variation. The compensation time is obtained by a PI controller. Simulation results demonstrate the validity of the proposed method.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.572-574
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• 2005

In this paper, a compensation scheme for the effect of dc-link ripple voltages on output voltage of two-leg and three-phase PWM inverters is proposed, without which compensation scheme the three-phase output voltage and current are much distorted. The proposed scheme has been verified by experimental results.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.2B no.3
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• pp.81-89
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• 2002

The sensorless AC motor drive is a popular topic of study due to the cost and reliability of speed and position sensors. Most sensorless algorithms are based on the mathematical modeling of motors including electrical variables such as phase current and voltage. Therefore, the accuracy of such variables largely affects the performance of the sensorless AC motor drive. However, the output voltage of the SVPWM-VSI, which is widely used in sensorless AC motor drives, has considerable errors. In particular, the SVPWM-VSI is error-prone in the low speed range because the constant DC link voltage causes poor resolution in a low output voltage command and the output voltage is distorted due to dead time and voltage drop. This paper investigates a novel high-performance strategy for overcoming these problems in a sensorless ac motor drive. In this paper, a variation of the DC link voltage and a direct compensation for dead time and voltage drop are proposed. The variable DC link voltage leads to an improved resolution of the inverter output voltage, especially in the motor's low speed range. The direct compensation for dead time and voltage drop directly calculates the duration of the switching voltage vector without the modification of the reference voltage and needs no additional circuits. In addition, the proposed strategy reduces a current ripple, which deteriorates the accuracy of a monitored current and causes torque ripple and additional loss. Simulation and experimentation have been performed to verify the proposed strategy.

• Proceedings of the KIPE Conference
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• 2003.07b
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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.