• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1184-1186
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• 2003

In this paper, a charge controlled asymmetrical half-bridge (ASHB) dc-to-dc converter is presented. For ASHB do-to-dc converter, the peak current-mode control was found to be problematic primarily due to the oscillatory behavior of the current feedback signal. To resolve this problem, a charge control method is applied to the ASHB do-to-dc converter. A 50W prototype ASHB dc-to-dc converter was built, and successfully tested.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.7
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• pp.1012-1016
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• 2009

This paper describes the control and monitoring system for OWEC (Overtopping Wave Energy Converter) which shows the characteristic of power stabilization in overtopping wave energy converter system. Overtopping waves generates different water pressure and the turbine is rotated by this pressure. As a result, overtopping wave energy converter is able to convert wave energy into electricity. Small size of overtopping wave energy converter is developed to simulate the control monitoring system which is able to control power generation and also monitor the system condition. The result shows the reduction of fluctuation from the overtopping wave energy system by the developed control monitoring system. In addition, the DB(Data Base) of test results are contributed to the research and development for OWEC.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.6
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• pp.122-128
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• 2011

This paper proposes a new control scheme of lithium ion battery units based on single phase multi-level converter. In the DC/AC converter applications using battery storage system, it is necessary to control the balancing voltage of individual battery units for high efficiency utilization. Using the proposed control scheme, the DC/AC single phase converter system is applied. To verify the effectiveness of the proposed control scheme, computer simulation is accomplished. In the computer simulation, lithium-ion battery units and single phase multi-level converter system are modeled and carried out using Psim simulation program. It will be helpful for design and applications of energy storage system with lithium-ion battery.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.97-105
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• 2013

The control method of the bidirectional DC/DC converter for instantaneous regenerative current control is described in this paper. The general method to control the DC/DC converter is the output voltage control. However, the regenerative current cannot be controlled to be constant with this control method. To improve the performance of the conventional control method, the DC-link voltage of the inverter is controlled within the tolerance range by the instantaneous boost and buck operations of the bidirectional DC/DC converter. By the proposed control method, the battery current can be controlled to be constant regardless of the motor speed variation. The improved performance of the DC/DC converter controlled by the proposed control method is verified by the experiment and simulation of the system with the inverter and IPMSM(Interior Permanent Magnet Synchronous Motor) which is operated by the reduced practical speed profile.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.7
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• pp.662-668
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• 2015

This paper presents an improved predictive control of an induction machine fed by a matrix converter using N-switching vectors as the control action during a complete sampling period of the controller. The conventional model predictive control scheme based matrix converter uses a single switching vector over the same period which introduces high torque ripple. The proposed switching scheme for a matrix converter based model predictive control of an induction machine drive selects the appropriate switching vectors for control of electromagnetic torque with small variations of the stator flux. The proposed method can reduce the ripple of the electrical variables by selecting the switching state as well as the method used in the space vector modulation techniques. Simulation results are presented to verify the effectiveness of the improved predictive control strategy for induction machine fed by a matrix converter.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.3
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• pp.190-198
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• 2018

This paper proposes a nonisolated, bidirectional, soft-switching DC - DC converter with PWM plus phase shift (PPS) control. The proposed converter has an input-parallel/output-series configuration and can achieve the interleaving effect and high voltage gains, resulting in decreased voltage ratings in all related devices. The proposed converter can operate under zero-voltage switching (ZVS) conditions for all switches in continuous conduction mode. The power flow of the proposed converter can be controlled by changing the phase shift angle, and the duty is controlled to balance the voltage of four high voltage side capacitors. The PPS control device of the proposed converter is simple in structure and presents symmetrical switching patterns under a bidirectional power flow. The PPS control also ensures ZVS during charging and discharging at all loads and equalizes the voltage ratings of the output capacitors and switches. To verify the validity of the proposed converter, an experimental investigation of a 2 kW prototype is performed in both charging and discharging modes under different load conditions and a bidirectional power flow.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.6
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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.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.5
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• pp.366-372
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• 2018

Three-port dual-active bridge (DAB) converter in a DC microgrid was studied due to its high power density and cost-effectiveness. The other advantages of DAB include galvanic isolation and bidirectional power conversion capability using simple control modulation. The three-port DAB converter consists of a three winding transformer and three bridges. The transformer has three phases, which means that the ports are coupled. Thus, the three-port DAB converter causes unwanted power flows when the load connected to each port changes. The basic operational principles of the three-port DAB converter are presented in this study. The decoupling control strategy of the independent port power transfer is presented with a mathematical power model to overcome the unexpected power flow problem. The validity of the proposed analysis and control strategy is verified with PSIM simulation and experiments using a 1-kW prototype power converter.

• Journal of Power Electronics
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• v.18 no.5
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• pp.1595-1607
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• 2018

In this paper, a hierarchical control strategy is introduced to control a new three-port multidirectional DC-DC converter for integrating an energy storage system (ESS) to a bipolar DC microgrid (BPDCMG). The proposed converter provides a voltage-balancing function for the BPDCMG and adjusts the states of charge (SoC) of the ESS. Previous studies tend to balance the voltage of the BPDCMG buses with active sources or by transferring power from one bus to another. Furthermore, the batteries available in BPDCMGs were charged equally by both buses. However, this power sharing method does not guarantee efficient operation of the whole system. In order to achieve a higher efficiency and lower energy losses, a triple-layer hierarchical control strategy, including a primary droop controller, a secondary voltage restoration controller and a tertiary optimization controller are proposed. Thanks to the multi-functional operation of the proposed converter, its conversion stages are reduced. Furthermore, the efficiency and weight of the system are both improved. Therefore, this converter has a significant capability to be used in portable BPDCMGs such as electric DC ships. The converter modes are analyzed and small-signal models of the converter are extracted. Comprehensive simulation studies are carried out and a BPDCMG laboratory setup is implemented in order to validate the effectiveness of the proposed converter and its hierarchical control strategy. Simulation and experimental results show that using the proposed converter mitigates voltage imbalances. As a result, the system efficiency is improved by using the hierarchical optimal power flow control.

• Journal of Power Electronics
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• v.19 no.1
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• pp.220-233
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• 2019

This work aims to study and analyze the various operating modes of universal power converter which is powered by solar and thermoelectric generators. The proposed converter is operated in a DC-DC (buck or boost mode) and DC-AC (single phase) inverter with high efficiency. DC power sources, such as solar photovoltaic (SPV) panels, thermoelectric generators (TEGs), and Li-ion battery, are selected as input to the proposed converter according to the nominal output voltage available/generated by these sources. The mode of selection and output power regulation are achieved via control of the metal-oxide semiconductor field-effect transistor (MOSFET) switches in the converter through the modified stepped perturb and observe (MSPO) algorithm. The MSPO duty cycle control algorithm effectively converts the unregulated DC power from the SPV/TEG into regulated DC for storing energy in a Li-ion battery or directly driving a DC load. In this work, the proposed power sources and converter are mathematically modelled using the Scilab-Xcos Simulink tool. The hardware prototype is designed for 200 W rating with a dsPIC30F4011 digital controller. The various output parameters, such as voltage ripple, current ripple, switching losses, and converter efficiency, are analyzed, and the proposed converter with a control circuit operates the converter closely at 97% efficiency.