• Journal of Power Electronics
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• 제18권6호
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• pp.1634-1641
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• 2018

This study focuses on a high-performance direct active and reactive power controller design that is successfully applicable to three-phase pulse width modulation (PWM) AC/DC converters used in renewable distributed energy generation systems. The proposed controller can overcome the sluggish transient dynamic response of conventional controllers to rapid power command changes. Desired active and reactive powers can be thoroughly obtained at the end of each PWM period through a deadbeat solution. The proposed controller achieves an exact nonlinear cross-coupling decoupling of system power without using a predefined switching table or bang/bang hysteresis control. A graphical and analytical analysis that naturally leads to a control voltage vector selection is provided to confirm the finding. The proposed control strategy is evaluated on a 3 kW PWM AC/DC converter in the simulation and experiment.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.104-107
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• 2007

Among the alternative energy sources, the solar energy is recognized as an important energy source and its application is increasing. Especially in future, the hybrid solar energy generation system with battery will be widely used as an independent distributed power generation system. In this paper, a solar power hybrid home generation system using a contact-less power supply (CPS) that can transfer an electric power without any mechanical contact by using magnetic coupling instead of the power transfer by directly supplying the DC power to the home electric system is proposed. The proposed system consists of a ZVS boost converter, a half bridge LLC resonant converter and contact-less transformer.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 추계학술대회 논문집
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• pp.66-67
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• 2014

Stabilization of the DC bus voltage is an important task in DC-AC microgrid system with renewable energy source such as solar system. A battery energy storage system (BESS) has become a general solution to stabilize the DC-bus voltage in DC-AC microgrid. This paper develops the analog BESS controller which requires neither computation nor dc-bus voltage measurement, so that the system can be implemented simply and easily. Even though others methods can stabilize and control the DC-bus voltage, it has complicated structure in control and low adaptive capability. The proposed topology is simple but is able to compensate the solar source variation and stabilize the DC-bus voltage under any loads and distributed generation (DG) conditions. In addition, the design of analog controller is presented to obtain a robust system. In order to verify the effectiveness of the proposed control strategy, simulation is carried out by using PSIM software.

• 전력전자학회논문지
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• 제26권2호
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• pp.150-157
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• 2021

Nowadays, a DC microgrid that can link various distributed power sources is gaining much attention. Accordingly, research on fault situations, such as line-to-line and line-to-ground faults of the DC microgrid, has been conducted to improve grid reliability. However, the blackout of an AC system and the oscillation of a DC bus voltage have not been reported or have not been sufficiently verified by previous research. In this study, a 20 kW DC microgrid testbed using a power HIL simulation technique is proposed. This testbed can simulate various fault conditions without any additional grid facilities and dangerous experiments. It includes the blackout of the DC microgrid caused by the AC utility grid's blackout, a drastic load increment, and the DC bus voltage oscillation caused by the LCL filter of the voltage source converter. The effectiveness of the proposed testbed is verified by using Opal-RT's OP5707 real-time simulator with a 3 kW prototype three-port dual-active-bridge converter.

• Journal of Power Electronics
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• 제15권4호
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• pp.899-909
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• 2015

A dual-input boost-buck converter with coupled inductors (DIBBC-CI) is proposed as a thermoelectric generator (TEG) power conditioner with a wide input voltage range. The DIBBC-CI is built by cascading two boost cells and a buck cell with shared inverse coupled filter inductors. Low current ripple on both sides of the TEG and the battery are achieved. Reduced size and power losses of the filter inductors are benefited from the DC magnetic flux cancellation in the inductor core, leading to high efficiency and high power density. The operational principle, impact of coupled inductors, and design considerations for the proposed converter are analyzed in detail. Distributed maximum power point tracking, battery charging, and output control are implemented using a competitive logic to ensure seamless switching among operational modes. Both the simulation and experimental results verify the feasibility of the proposed topology and control.

• 전력전자학회논문지
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• 제21권6호
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• pp.486-496
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• 2016

The voltage unbalance of an LVDC bipolar distribution system was controlled for high power quality. Voltage unbalance may occur in a bipolar distribution system depending on the operation of the converter and load usage. Voltage unbalance can damage sensitive load and lead to converter accidents. The conditions that may cause voltage unbalance in a bipolar distribution system are as follows. First, three-level AC/DC converters in bipolar distribution systems can lead to voltage unbalance. Second, bipolar distribution systems can be at risk for voltage unbalance because of load usage. In this paper, the output DC link of a three-level AC/DC converter was analyzed for voltage unbalance, and the bipolar voltage was controlled with algorithms. In the case of additional voltage unbalance according to load usage, the bipolar voltage was controlled using the proposed converter. The proposed converter is a dual half-bridge converter, which was improved from the secondary circuit of a dual half-bridge converter. A control algorithm for bipolar voltage control without additional converters was proposed. The balancing control of the bipolar distribution system with distributed power was verified through experiments.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1045_1046
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• 2009

This paper presents an active and reactive power compensator for the wind power system with squirrel-cage induction generator. The developed system is able to continuously compensate the active and reactive power. The 3-phase inverter operates for the compensation of reactive power, while the DC/DC converter with super-capacitors operates for the compensation of active power. The proposed compensator can be expected that developed system may be used to compensated the abrupt power variation due to sudden change of wind speed or sudden power-drop by tower effect. It can be also applied for the distributed generation and the Micro-Grid.

• 전력전자학회논문지
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• 제23권4호
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• pp.265-272
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• 2018

This paper proposes a new control method for the supercapacitor (SC) to compensate the pulsed load and to enhance the power quality of the DC microgrid. By coordinating the operating frequency, the SC is controlled to handle the surge current, while the low-frequency current component is dealt with by the remaining sources in the system. The operation mode of the SC unit is automatically changed based on the state of charge and DC bus voltage level. Meanwhile, the mismatch in the power demand is covered by the SC unit by regulating the DC bus voltage level. The effectiveness of the proposed method is verified experimentally by the prototype with two distributed generators and one SC unit.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 추계학술대회 논문집
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• pp.5-6
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• 2016

This paper introduces a high efficiency bidirectional resonant converter using an additional LC auxiliary circuit for dcdistribution applications. The LC auxiliary circuit operates as a variable inductor and the additional LC circuit helps to increase the effective magnetizing inductance, thereby reducing the turn-off and primary circulating current. A 5 kW bidirectional converter for dc-distribution system is implemented to verify the validity of the proposed method. The experimental results show the high efficiency characteristics of the proposed converter over the wide range of load in both direction of power flow. The maximum efficiency of the proposed system was 98.1 % at 3 kW.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 추계학술대회
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• pp.32-33
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• 2010

This paper describes a droop control method for the autonomous operation of DC distribution system using distributed generations and energy storage. The method suppress the circulating current, and each unit could be controlled autonomously without communication system. Detailed model of wind power generation, photo-voltaic generation, fuel-cell generation and battery was implemented with the user-defined model of PSCAD/EMTDC software that is coded with C-language. The simulation and experimental results confirms that the proposed DC distribution system make it feasible to provide power to the load stably and verify effectiveness of the proposed method.