• Journal of IKEEE
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• v.24 no.3
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• pp.867-876
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• 2020

This paper proposes a neutral-point voltage ripple reduction of high frequency injection sensorless control of IPMSM fed by a three-level inverter. The high frequency voltage injection method has been successfully applied to sensorless control for IPMSM at low speed region. In the process of high frequency voltage injection sensorless control for IPMSM, the neutral-point voltage ripple is increased. It should be reduced because it distorts the output current and decreases a life time of DC-link capacitor. The proposed method in this paper reduces the neutral-point voltage ripple by compensating the reference voltage, and the compensation value is calculated simply with reference voltages and currents. The effectiveness of 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.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.542-546
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• 2004

This paper presents a technique to reduce the low frequency ripple voltage of the dc output in a BIFRED converter with a small-sized energy storage capacitor. The proposed pulse width control method can be effectively used to suppress the low frequency ripple appeared in the dc output and still shows generally good performance such as low THD of input line current and high power factor. Using the small-sized energy storage capacitor, it has better merits of low cost and small size than a conventional BIFRED converter. The proposed technique is illustrated its validity and effectiveness through simulations.

• Journal of Power Electronics
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• v.5 no.3
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• pp.190-197
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• 2005

This paper presents a technique to reduce the low frequency ripple voltage of the dc output in a BIFRED converter with a small-sized energy storage capacitor. The proposed pulse width control method can be effectively used to suppress the low frequency ripple appeared in the dc output and still maintains generally good performance such as low THD of input line current and a high power factor. Using the small-sized energy storage capacitor, it has better merits of low cost and smaller size than a conventional BIFRED converter. The proposed technique is illustrated its validity and effectiveness through simulations.

• Journal of Power Electronics
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• v.19 no.4
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• pp.881-893
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• 2019

This paper proposes a practical sliding-mode controller design for shaping the impedances of cascaded boost-converter power decoupling circuits for reducing the second order harmonic ripple in photovoltaic (PV) current. The cascaded double-boost converter, when used as power decoupling circuit, has some advantages in terms of a high step-up voltage-ratio, a small number of switches and a better efficiency when compared to conventional topologies. From these features, it can be seen that this topology is suitable for residential (PV) rooftop systems. However, a robust controller design capable of rejecting double frequency inverter ripple from passing to the (PV) source is a challenge. The design constraints are related to the principle of the impedance-shaping technique to maximize the output impedance of the input-side boost converter, to block the double frequency PV current ripple component, and to prevent it from passing to the source without degrading the system dynamic responses. The design has a small recovery time in the presence of transients with a low overshoot or undershoot. Moreover, the proposed controller ensures that the ripple component swings freely within a voltage-gap between the (PV) and the DC-link voltages by the small capacitance of the auxiliary DC-link for electrolytic-capacitor elimination. The second boost controls the main DC-link voltage tightly within a satisfactory ripple range. The inverter controller performs maximum power point tracking (MPPT) for the input voltage source using ripple correlation control (RCC). The robustness of the proposed control was verified by varying system parameters under different load conditions. Finally, the proposed controller was verified by simulation and experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.2
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• pp.94-100
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• 2018

Generally, in a single-phase energy storage system (ESS) for households, AC ripple component with twice the fundamental frequency exists inevitably in the DC link voltage of single-phase PCS. In the grid-connected mode of a single-phase inverter, the AC ripple component in the DC link voltage causes low-order harmonics on grid-side current that deteriorates power quality on an AC grid. In this work, a control system adopting a feedforward controller is established to eliminate the AC ripple interference on the DC link side. Optimal battery nominal voltage design method is also proposed by considering the voltage loss and AC ripple voltage on DC link side in a single-phase ESS. Finally, the control system and battery nominal voltage design method are verified through simulations and experiments.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1851-1860
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• 2016

The traction motors in electric multiple unit (EMU) trains are powered by AC-DC-AC converters, and the DC link voltage is generated by single phase PWM converters, with a fluctuation component under twice the frequency of the input catenary AC grid, which causes fluctuations in the motor torque and current. Traditionally, heavy and low-efficiency hardware LC resonant filters parallel in the DC side are adopted to reduce the ripple effect. In this paper, an analytical model of the ripple phenomenon is derived and analyzed in the frequency domain, and a ripple control scheme compensating the slip frequency of rotor vector control systems without a hardware filter is applied to reduce the torque and current ripple amplitude. Then a relatively simple discretization method is chosen to discretize the algorithm with a high discrete accuracy. Simulation and experimental results validate the proposed ripple control strategy.

• Journal of the Korean Solar Energy Society
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• v.32 no.6
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• pp.106-112
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• 2012

As a fuel cell converts the chemical energy of the fuel cell into electrical energy by electrochemical reaction, the fuel cell system is uniquely integrated technique including fuel processor, fuel cell stack, power conditioning system. The residential fuel cell-PCS(Power Conditioning System) needs to convert efficiently the DC current produced by the fuel cell into AC current using single-phase DC-AC inverter. A single-phase DC-AC inverter has naturally low frequency ripple which is twice frequency of the output current. This low frequency(120Hz) ripple reduces the efficiency of the fuel cell. This paper presents notch filter with IP voltage controller to reject specific 120Hz current ripple in single-phase inverter. The notch filter is designed that suppress just only specific frequency component and no phase delay. Finally, the proposed notch filter design method has been verified with computer simulation and experimentation.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.1
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• pp.9-15
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• 2006

The conventional hysterysis band DTC(Direct Torque Control) strategy have relatively high torque ripple at low speed and variable switching frequency according to motor speed even though it provides a fast torque response with very simple scheme consisted with only two hysteresis band comparators and a switching table for torque and flux control. In this paper, author proposed a new DTC scheme based on the torque slope and reference voltage control. The new scheme can maintain the minimized torque ripple and constant switching frequency. Experimental tests carried out with an 1.5kW induction motor drive system show improved dynamic characteristics and prove the feasibility of proposed strategy.

• Korean Journal of Digital Imaging in Medicine
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• v.13 no.1
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• pp.27-32
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• 2011

The conventional types of X-ray generators were bulky in physical size and heavy in weight, and the control accuracies of the output voltages were not always satisfactory. The high frequency switching inverter and converter technology on power conversion and control systems have been greatly closed up introducing power semiconductor devices. To decreasing the volume and the weight of high voltage transformer, and to stabilize ripple. In this paper, the newly developed x-ray generator in a low cost using duty modulation PWM inverter. This system verify improved performance by stabilize ripple of X-ray tube voltage and compared the reproducibility, linearity and dose in single phase, three phase and PSU.