• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.2
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• pp.126-133
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• 2016

This paper proposes a new PWM method to reduce the common mode voltage change in three-level Vienna rectifier. This new proposed PWM method uses medium voltage vector for the three-level Vienna rectifier to determine the sum of three-phase voltage zero, and the common mode voltage variation is decreased. Using the carrier comparison method, the switching function generator for three-level Vienna rectifier has been proposed. The effects of the proposed PWM method have been verified through simulation using the PSIM.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.1
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• pp.29-36
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• 2020

In this study, a variable step algorithm is proposed on the basis of the perturb and observe method. The proposed algorithm can follow the maximum power point (MPP) quickly when solar irradiance changes rapidly. The proposed technique uses the voltage change characteristic at the MPP when the environment changes because of insolation or temperature. The MPP is tracked through the voltage control using a variable step method. This method determines the sudden change of solar irradiance by setting the threshold value and operates in fast tracking mode to track the MPP rapidly. When the operation point reaches the MPP, the mode switches to the variable step mode to minimize the steady state error. In addition, the output disturbance is decreased through the optimization of the control method design. The performance of the proposed MPPT algorithm is verified through simulation and experiment.

• Journal of Power Electronics
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• v.12 no.2
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• pp.276-284
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• 2012

AC/AC power conversion is widely used to feed AC loads with a variable voltage and/or a variable frequency from a constant voltage constant frequency power grid or to connect critical loads to an unreliable power supply while delivering a very balanced and accurate sinusoidal voltage system of constant amplitude and frequency. The load specifications will clearly impose the requirements for the inverter stage of the power converter, while wider ranges of choices are available for the rectifier. This paper investigates the utilization of a buck-type current source rectifier as the active front-end stage of an AC/AC converter for applications that require an adjustable DC-link voltage as well as elimination of the low-frequency common mode voltage. The proposed solution is to utilize a combination of two or more zero current vectors in the Space Vector Modulation (SVM) technique for Current Sources Rectifiers (CSR).

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.1
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• pp.19-26
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• 2016

In this study, a bidirectional DC-DC converter for idle stop and go (ISG) is developed to reduce fuel consumption. A three-phase non-isolated half-bridge converter is selected through a design method by considering efficiency and volume. According to the state of charge of the batteries at both the low-voltage and high-voltage sides, buck mode, which charges a low-voltage battery from the generated motor energy, and boost mode, which provides power to the motor from the low- and high-voltage battery sides, are required in the ISG system. Hence, an autonomous and seamless bidirectional control method using a variable current limiter is proposed for mode change. A 1.8 kW engineering sample of the proposed converter has been built and tested to verify the validity of the proposed concept. The maximum efficiencies, including gate driver and control circuit losses, are 96.4% in charging mode and 96.1% in discharging mode.

• Journal of Power Electronics
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• v.11 no.4
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• pp.449-455
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• 2011

Electric drive vehicles (EDV) have received much attention recently because of their environmental and energy benefits. In an EDV, the motor drive system directly influences the performance of the propulsion system. However, the available DC voltage is limited, which limits the maximum speed of the motors. At high speeds, the inverter voltage increases if the square wave (SW) voltage (six-step operation) is used. Although conventional direct torque control (DTC) has several advantages, it cannot work in the six-step mode required in high-speed applications. In this paper, a single-mode seamless DTC for AC motors is proposed. In this scheme, the trajectory of the reference flux changes continuously between circular and hexagonal paths. Therefore, the armature voltage changes smoothly from a high-frequency switching pattern to a square wave pattern without torque discontinuity. In addition, because multi-mode controllers are not used, implementation is more straightforward. Simulation results show the voltage pattern changes smoothly when the motor speed changes, and consequently, torque control without torque discontinuity is possible in the field weakening area even with a six-step voltage pattern.

• Journal of Power Electronics
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• v.14 no.1
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• pp.40-47
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• 2014

An average current mode control scheme that consistently offers good dynamic performance for LLC series resonant DC-to-DC converters irrespective of the changes in the operational conditions is presented in this paper. The proposed control scheme employs current feedback from the resonant tank circuit through an integrator-type compensation amplifier to improve the dynamic performance and enhance the noise immunity and reliability of the feedback controller. Design guidelines are provided for both current feedback and voltage feedback compensation. The performance of the new control scheme is demonstrated through an experimental 150 W converter operating with 340 V to 390 V input voltage to provide a 24 V output voltage.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.4
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• pp.364-372
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• 2016

In this paper, a voltage controller for the seamless transition of a grid-connected inverter for ESS is proposed. The single-phase inverter is operated as a current controller when the grid is connected and as a voltage controller in the stand-alone mode when the grid is disconnected. Generally, in the case of grid recovery, the overcurrent may flow into the system because of the mismatch phase between the inverter output and grid voltages. The proposed controller resolves the overcurrent problem through phase delay problems with initial value feed-forward control of the integrator when the grid voltage is restored. The effects of the control method are simulated through PSIM, and the usefulness of the control method is verified through experiments.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.2
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• pp.138-144
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• 2013

Most of the DC loads have had the sensitive characteristics electrically for input voltage. In this system, power converter is operated after connecting with DC loads to minimize the overshoot of the control voltage that may occur during connection of the loads. But whenever starting the power converter, parameters in circuit are different because power converter has been connected with diverse load types at each startup time. This is cause of a disadvantage to PI controller design of power converter. In this paper, the novel voltage control method using sliding mode control theory has proposed. This control method minimizes the overshoot of control voltage at startup of power converter. Despite the variations of the system parameters, the proposed voltage controller has fast response and robustness characteristics such as PI and sliding mode controllers. The proposed controller was applied to the three-phase AC/DC converter and each performance of controller was verified.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.94-97
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• 2008

In this paper, A Digital Voltage Mode Controller is designed for the Photovoltaic power converter applications. The designed Digital Voltage Mode Controller is derived analytically from the continuous time small signal model of the boost converter. Due to the small signal model based derivations of the control law, the designed control method can be applicable to K-factor Approach method and bilinear transformation. In order to show the usefulness of a designed controller, and the simulation results are verified.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1064-1070
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• 2007

This paper presents a grid-interactive current controlled voltage source inverter (CCVSI) with uniterruptible power supply (UPS), which uses an inner current control loop (polarized ramp time (PRT)) and outer feedback control loops to improve grid power quality and UPS. To reduce the complexity, cost and number of power conversions, which results in higher efficiency, a single stage CCVSI is used. The operation of this system could be divided into the power quality control (PQC) state mode and the UPS state mode. In PQC mode, the system operated to compensate the reactive power demand by nonlinear load or variation in load. In UPS mode. the system is controlled to provide a sinusoidal voltage at the rated value for the load when the gird fail. To verify the proposed system, a comprehensive evaluation with theoretical analysis, simulation and experimental results for 1KVA load capacity is presented.