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Cha H.,Chungnam National University | Lee W.,Chungnam National University | An T.-P.,ENTEC Electrical and Electronic Co.
Proceedings of the 2011 14th European Conference on Power Electronics and Applications, EPE 2011 | Year: 2011

In this paper, a 50kW multi-string photovoltaic power conditioning system (PV PCS) and control schemes are proposed and analyzed. The PV PCS consists of five 10kW three-phase interleaved dc-dc converters and a 50kW centralized inverter with LCL-filter, whose controllers are connected through CAN communication for synchronization and ripple current reduction. Prototype of multi-string PV PCS is implemented and tested for the proposed several control schemes. © 2011 EPE Association - European Power Electr. Source


Lee S.-H.,Chungnam National University | An T.-P.,ENTEC Electrical and Electronic Co. | Cha H.,Chungnam National University
Journal of Power Electronics | Year: 2010

A photovoltaic power conditioning system (PV PCS) that contains single-phase dc/ac inverters tends to draw an ac ripple current at twice the output frequency. Such a ripple current perturbs the operating points of solar cells continuously and it may reduce the efficiency of the current based maximum power point tracking technique (CMPPT). In this paper, the ripple current generation in a dc link and boost inductor is analyzed using the ac equivalent circuit of a dc/dc boost converter. A new feed-forward ripple current compensation method to incorporate a current control loop into a dc/dc converter for ripple reduction is proposed. The proposed feed-forward compensation method is verified by simulation and experimental results. These results show a 41.8 % reduction in the peak-to peak ac ripple. In addition, the dc/ac inverter control system uses an automatic voltage regulation (AVR) function to mitigate the ac ripple voltage effect in the dc link. A 3kW PV PCS prototype has been built and its experimental results are given to verify the effectiveness of the proposed method. Source


Patent
ENTEC Electrical AND ELECTRONIC CO. | Date: 2013-05-24

The disclosure relates to a permanent magnet actuator comprising: a stator iron core having a space therein-side, and having a first wall and a second wall opposing the first wall; a movable element moving reciprocally between the first wall and the second wall, along a moving axis which connects the first wall and the second wall inside the space; a first magnetomotive force supplying body and a second magnetomotive force supplying body disposed respectively on the first wall and the second wall, so as to supply a magnetomotive force to the movable element for the reciprocal movement thereof, wherein, at least one of the first magnetomotive force supplying body and the second magnetomotive force supplying body selectively produces a bidirectional magnetomotive force; a permanent magnet disposed between the first magnetomotive force supplying body and the second magnetomotive force supplying body, and providing a coercive force to the movable element for maintaining the state thereof; and a driving circuit comprising a control unit for controlling a voltage or current that is supplied to the first magnetomotive force supplying body and the second magnetomotive force supplying body.


Jung H.,Korea Railroad Research Institute | Kim H.,Korea Railroad Research Institute | Chang S.-H.,Korea Railroad Research Institute | Kim J.,Korea Railroad Research Institute | And 3 more authors.
Journal of Electrical Engineering and Technology | Year: 2015

Generally, an autotransformer(AT) feeding system consists of double tracks, up and down, with the trolley wire and feeder wire of the up and down tracks connected in the sectioning post(SP). Consequently, load current or fault current flows on two tracks based on catenary impedance characteristics, making it difficult to estimate catenary impedance accurately. This paper presents a technique for the estimation of catenary impedance using boosting current compensation based on the current division characteristics of an AT feeding system to improve the operation performance of impedance relay. To verify the technique, we model an AT feeding system through a power analysis program (PSCAD/EMTDC) and simulate various operation and fault conditions. Through the simulation, we confirmed that the proposed technique has estimated catenary impedance with a similar degree of accuracy to the actual catenary impedance. © The Korean Institute of Electrical Engineers. Source


Jung H.,Korea Railroad Research Institute | Kim J.,Korea Railroad Research Institute | Shin S.,Korea Railroad Research Institute | Kim H.,Korea Railroad Research Institute | And 2 more authors.
Transactions of the Korean Institute of Electrical Engineers | Year: 2012

This paper presents to verify the selective grounding fault protective relaying technique for the ungrounded DC traction power supply system. This system selectively blocks fault section when grounding fault occurred. In order to perform this verification, field test facilities have been installed on Oesam substation and Worldcup-Stadium substation, and field test process has been suggested. Also, selective grounding fault protective relaying components and rail voltage reduction device have been tested with the various trial examinations. In order to compare and evaluate performance of the selective grounding fault protective relaying function, field test system was modeled and the system fault simulation results were compared and evaluated with the field test result. Performance of selective grounding fault protective relaying function was evaluated with the above-mentioned process, and the fact that the system recognizes fault section irrespective of insulation between rail and ground and fault resistance from grounding fault. Source

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