• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.12
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• pp.609-615
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• 2005

A 30kW electrical power conversion system is developed for a variable speed wind turbine. In the wind energy conversion system(WECS) a synchronous generator with field current excitation converts the mechanical energy into electrical energy. As the voltage and the frequency of the generator output vary according to the wind speed, a 6-bridge diode rectifier and a PWM boost chopper is utilized as an ac-dc converter maintaining the constant dc-link voltage with only single switch control. An input current control algorithm for maximum power generation during the variable speed operation is proposed without any usage of speed sensor. Grid connection type PWM inverter converts dc input power to ac output currents into the grid. The active power to the grid is controlled by q-axis current and the reactive power is controlled by d-axis current with appropriate decoupling. The phase angle of utility voltage is detected using software PLL(Phased Locked Loop) in d-q synchronous reference frame. Experimental results from the test of 30kW prototype wind turbine system show that the generator power can be controlled effectively during the variable speed operation without any speed sensor.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_3
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• pp.1259-1267
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• 2023

In recent years, as the demand for distributed power has increased, the need for microgrids connected to grid power and renewable power generation sources has emerged. In the case of DC microgrids, reactive power does not occur, and power conversion losses are reduced compared to AC when connecting to the load and power grid[2]. With the revitalization of the DC distribution network industry, various studies and demonstrations of DC microgrids have been carried out. In the case of the recent unit distribution, its stability and effectiveness have been verified through empirical and research analysis. However, there is a lack of empirical tests to prevent chain accidents for the protection of the power grid circuits and the misoperation of the distributed power system caused by individual accidents when connecting various distributed power sources and power grids. In this paper, the operation plan of a stable multi-circuit DC distribution connection for the demonstration site was verified through the protection cooperation and operation algorithm for the stable linkage management of the DC distribution network composed of such a multi-circuit.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.5
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• pp.22-33
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• 2021

In the case of open phase faults caused by the disconnection of distribution feeders interconnected to a PV system, many problems can occur depending on the core type and wiring method of the grid-connected transformers. Moreover, open phase faults are difficult to detect because the open phase voltage of the existing protection relay (Open Phase Relay (47)) can be maintained, even though a disconnection fault occurred, depending on the wiring method and the iron core type of the grid-connected transformer for a PV system. Therefore, this paper proposes a novel algorithm to detect open phase faults by comparing the currents and phases between the primary and secondary sides of a grid-connected transformer. In addition, this paper presents the modeling of a distribution system and protection devices for detecting open phase faults using PSCAD/EMTDC S/W, and implements a test protection device for detecting open phase faults based on the above-mentioned modeling. The simulation and test results confirmed that the proposed algorithm is useful for detecting open phase faults according to the wiring method and iron core type of grid-connected transformer for a PV system because operation slope and unbalance rate of the primary current exceed the setting value (30[%]) of the protection device.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.548-553
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• 2003

The frequency and phase angle of the utility voltage are important in many industrial systems. this paper present a detailed analysis of single-phase digital PLL control for utility connected systems. and its performance under utility conditions with noise is discussed. The experimental results demonstrate phase tracking capability in the single-phase grid-connected operation.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.230-231
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• 2010

In this paper, a fault detection algorithm for an UPS operation of power station is proposed. By adapting the algorithm, a grid-connected power station performs a UPS operation when faults such as sag, swell are occurred. Through a computer simulation, grid faults are simulated and the proposed fault detection algorithm using d, q axis observation method is verified.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.5
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• pp.46-53
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• 2013

This paper introduces a grid-interactive storage system to operate the customers without voltage source inverters as a microgrid. The proposed storage system does not require any modification of the control scheme of the inverters existing within the customers. Novel control scheme of the grid-interfacing storage system according to its new structure ensures the seamless transition between the grid-connected and islanded operation of the microgrid.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.677-681
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• 2005

This Paper presents a 6 pulse shift operation control mode of current-source-inverter to make improvement of efficiency and to reduce the frequency of inverter switching for photovoltaic generation system using PWM current-source-inverter. This system is connected solar cell energy directly without using a storage cell. The proposed circuit can maintain maximum voltage of photovoltaic generation of take advantage of six Buck-Boost converter and a full-bridge inverter determines the polarity of AC output. That is controlled by using digital signal processor TMS320F2812 for operation about a 6 pulse shift operation control of current-source-inverter, and it is verified through the experimental results.

• Proceedings of the KIPE Conference
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• 2001.12a
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• pp.59-62
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• 2001

New grid connected PV system of high-frequency link with soft-switching is proposed to solve problems related with transformer and switching loss. The operation of suggested equipment using the soft switching that consists of high frequency transformer is confirmed by computer simulation and experiment that it can improve its efficiency and solve the problems mentioned above.

• Journal of Power Electronics
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• v.10 no.5
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• pp.555-562
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• 2010

This paper presents the development of a hardware simulator for a 3-parallel grid-connected PMSG wind power system. With the development of permanent magnetic materials in recent years, the capacity of a PMSG based wind turbine system, which requires a full-scale power converter, has been raised up to a few MW. Since it is limited by the available semiconductor technology, such large amounts of power cannot be delivered with only one power converter. Hence, a parallel connecting technique for converters is required to reduce the ratings of the converters. In this paper, a hardware simulator with 3-parallel converters is described and its control issues are presented as well. Some experimental results are given to illustrate the performance of the simulator system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.2
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• pp.309-314
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• 2002

New grid connected PV(Photovoltaic) system of high-frequency link with soft-switching is proposed to solve problems related to the loss of transformer and switch. The operation of Proposed system using the soft switching that consists of high frequency transformer is confirmed by computer simulation and experiment. It can improve its efficiency and solve the Problems mentioned above.