• Journal of Power Electronics
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• v.14 no.4
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• pp.764-777
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• 2014

This study analyzes the mathematical relationship between DC-link voltage and system parameters for shunt active power filters (APFs). Analysis and mathematical deduction are used to determine the required minimum DC-link voltage for APF. A novel adaptive DC-link voltage controller for the three-phase four-wire shunt APF is then proposed. In this controller, the DC-link voltage reference value will be maintained at the required minimum voltage level. Therefore, power consumption and switching loss will effectively decrease. The DC-link voltage can also adaptively yield different DC-link voltage levels based on different harmonic currents and grid voltage levels and thus avoid the effects of harmonic current and grid voltage fluctuation on compensation performance. Finally, representative simulation and experimental results in a three-phase four-wire center-split shunt APF are presented to verify the validity and effectiveness of the minimum DC-link voltage design and the proposed adaptive DC-link voltage controller.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.1944-1953
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• 2014

This paper shows the design and control methods of the bidirectional DC-DC converter to generate the proper DC-link voltage of a PMSM drive. Conventionally, because the controllable power of the PWM based voltage source inverter is limited by its DC-link voltage, the DC-DC converter is used for boosted DC-link voltage if the inverter source cannot generate enough operating voltage for the PMSM drive. In this paper, to obtain more utilization of this DC-DC converter, optimal DC-link voltage control for PMSM drive will be explained. First, the process and current path of the DC-DC converter will be illustrated, and a control method of this converter for variable DC-link voltage will then be explained. Finally, an improvement analysis of the optimal DC-link voltage control method, especially on the deadtime effect, will be explained. The DC-DC converter of the proposed control method is verified by the experiments by comparing with the conventional constant voltage control method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.9
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• pp.1297-1305
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• 2015

This paper proposes a power feedforward technique for the performance improvement of DC-link voltage control in the dynamic voltage restorer (DVR). The DC-link Voltage is able to be unstable for an instant owing to any change in the load and voltage sag. The distortion of the DC-link voltage leads to the negative influence on the performance of DVR. To mitigate the distortion of the DC-link voltage, the power feedforward component is calculated by the load power and the grid voltage, and then it is added to the reference current of the conventional DC-link voltage controller. By including output power feedforward component on the DC-link controller, the DC-link voltage can settle down more quickly than when the conventional DC-link voltage controller applied. The proposed technique was validated through the simulation and experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.2
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• pp.120-126
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• 2021

DC-link capacitors are one of the main components in two-level three-phase voltage source inverters (VSIs); they provide the pulsating input current and stabilize the vacillating DC-link voltage. Ideally, the larger the capacitance of DC-link capacitors, the better the DC-link voltage stabilizes. However, high capacitance increases the cost and decreases the power density of VSI systems. Therefore, the capacitance should be chosen carefully on the basis of the DC-link voltage ripple requirement. However, the DC-link voltage ripple is dependent on the pulse-width modulation (PWM) strategy. This study especially presents a DC-link voltage ripple analysis when the minimum loss discontinuous PWM strategy is applied. Furthermore, an equation for the selection of the minimum capacitance of DC-link capacitors is proposed. Experimental results with R-L loads are also provided to verify the effectiveness of the presented analysis.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.179-183
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• 2013

This paper report on experimental results of 5-level inverter by DC divided link voltage. We have alreday reported that DC divided link valtage comes to be able to reduse harmonic of out line voltage. So we tested whether DC divided link voltage can reduce harmonics in experimental setup. This paper shows simulation results and experimental results. And we confirmed that DC divided link voltage can also apply in experimental setup.

• Journal of Power Electronics
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• v.3 no.4
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• pp.205-214
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• 2003

This paper proposes a simple control strategy based on the discontinuous PWM (DPWM) to balance the DC-link voltage of three-level neutral-point-clamped (NPC) inverter at low modulation index. It introduces new DPWM methods in multi-level inverter and one of them is used for balancing the DC-link voltage. The current flowing in the neutral point of the DC-link causes the fluctuation of the DC-link voltage of the NPC inverter. The proposed DPWM method changes the path and duration time of the neutral point current, which makes the overall fluctuation of the DC-link voltage zero during a sampling time of the reference voltage vector. Therefore, by using the proposed strategy, the voltage of the DC-link can be balanced fairly well and the voltage ripple of the DC-link is also reduced significantly. Moreover, comparing with conventional methods which have to perform the complicated calculation, the proposed strategy is very simple. The validity of the proposed DPWM method is verified by the experiment.

• Journal of Power Electronics
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• v.15 no.3
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• pp.763-774
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• 2015

This study investigates the inherent influence of a DC-link voltage controller on both DC-link voltage control and the compensation performance of a three-phase, four-wire shunt active power filter (APF). A nonlinear variable-parameter DC-link voltage controller is proposed to satisfy both the dynamic characteristic of DC-link voltage control and steady-state compensation performance. Unlike in the conventional fixed-parameter controller, the parameters in the proposed controller vary according to the difference between the actual and the reference DC-link voltages. The design procedures for the nonlinear voltage controller with variable parameters are determined and analyzed so that the proposed voltage controller can be designed accordingly. Representative simulation and experimental results for the three-phase, four-wire, center-spilt shunt APF verify the analysis findings, as well as the feasibility and effectiveness of the proposed DC-link voltage controller.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.19-21
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• 2006

This paper presents the control method that inverter output keeps to linear to reference voltage of Synchronous Reluctance Motor using DC Link voltage Synthesis. The Inverter output voltage cannot be displayed to linear about inverter reference voltage if Real DC Link voltage is different from DC Link voltage of PWM amplitude. Also, the overmodulation that there is linearity broken if reference voltage is out of range that inverter can output voltage. Torque ripple generates the vibration and noise of a motor. This paper proposes the control method so that torque ripple decreases and the linearity of inverter output keeps using the DC Link voltage Synthesis.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1233-1235
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• 2000

A new control method of three phase converter without measuring input phase-voltage and DC-link voltage is proposed. Input phase-voltage of these required voltages is estimated using EKF(Extended Kalman Filter) and DC-link voltage is estimated from the measured line currents and the estimated input phase-voltage. This control method is achieved without PLL(Phase Locked Loop) which senses the angle of input phase-voltage and DC-link voltage sensor. In addition, the proposed method controls high power factor and DC-link voltage utilizing the estimated phase angle. This paper describes the effectiveness of the proposed estimated algorithm through simulations.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.227-230
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• 2001

A new control method of three phase converter without measuring input Phase-voltage and DC-link voltage is Proposed. Input Phase-voltage of these required voltages is estimated using EKF(Extended Kalman Filter) and DC-link voltage is estimated from the measured line currents and the estimated input phase-voltage. This control method is achieved without PLL(Phase Locked Loop) which senses the angle of input phase-voltage and DC-link voltage sensor. In additon, the proposed method controls high power factor and DC-link voltage utilizing the estimated phase angle. This paper describes the effectiveness of the proposed estimated algorithm through simulations.