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Amir Khan, Umer,Jong-Geon Lee,Amir, Faisal,Bang-Wook Lee Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.6
<P>The key obstacle in integrating high-voltage direct current (HVDC) point-to-point networks into meshed multiterminal HVDC networks (MTDC) is the absence of dc circuit breakers (DCCBs), which can timely and reliably isolate the faulty HVDC network from the MTDC. In this paper, a novel hybrid-type superconducting DCCB model (SDCCB) is proposed. The SDCCB has a superconducting fault current limiter (SFCL) located in the main line, to limit the fault current until the final trip signal to the SDCCB is given. After the trip signal, insulated-gate bipolar transistor (IGBT) switches located in the main line will commutate the fault current into a parallel line, where dc current is forced to zero by combination of IGBTs and surge arresters. DC fault current behavior in MTDC and fundamental requirements of DCCB for MTDC were described, followed by an explanation of the working principles of the SDCCB. To prove the viability of the SDCCB, a simulation analysis demonstrating SDCCB current interruption performance was done for changing the intensity of dc fault current. It was observed that the passive current limiting by SFCL caused significant reduction in fault current interruption stress for SDCCB. Furthermore, fundamental design requirements for SFCL, including the effect of SFCL quenching impedance on SFCL voltage rating and energy dissipation capacity, were investigated. Finally, advantages and limitations of the SDCCB were highlighted.</P>
Khan, Umer-Amir,Lee, Sang-Hwa,Seong, Jae-Kyu,Lee, Bang-Wook The Korean Society of Superconductivity and Cryoge 2010 한국초전도저온공학회논문지 Vol.12 No.2
A considerable amount of research material discussing designs and properties of High Temperature Superconducting Fault Current Limiter (HTS FCL) is available. However, a shortage of research concerning positioning of HTS FCL in power grid is felt. In this paper a feasibility study of HTS FCL positioning in Smart Grid through simulation analysis is carried out. A complete power network (including generation, transmission and distribution) is modeled in Simulink / SimPowerSystems. A generalized HTS FCL is also designed by integrating Simulink and SimPowerSystem blocks. The distribution network of the model has a wind turbine attached to it forming a micro grid. Three phase fault have been simulated along with placing FCL models at key points of the distribution grid. It is observed that distribution grid, having distributed generation sources attached to it, must not have a single FCL located at the substation level. Optimized HTS FCL location regarding the best fault current contribution from wind turbine has been determined through simulation analysis.
움아르 아미르(Umer Amir Khan),성재규(Jae-Kyu Seong),오석호(Seok-Ho Oh),신우주(Woo-Ju Shin),이상화(Sang-Hwa Lee),이방욱(Bang-Wook Lee) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.7
The practical effectiveness of DC distribution system and efficieny of LED lighting system makes them a highly feasible solution for home lighting requirements. A DC distribution system having a integrated Photo Voltaic Energy system running LED light load for an average Korean house is modeled using Simulink/SimPowerSystems. An AC to DC convertor and a PV charge controller running Maximum Power Point Tracking algorithm is designed. Power efficiency and performance of the LED lighting system is evaluated and compared with conventional AC lighting system. The benefits of using PV system are highlighted.
움아르 아미르(Umer Amir Khan),오석호(Seok-Ho Oh),성재규(Jae-Kyu Seong),신우주(Woo-Ju Shin),이상화(Sang-Hwa Lee),이방욱(Bang-Wook Lee) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.7
This paper discusses the benefits of DC LED lighting system and the challenges that are hindering its large scale adoption in Korea. Despite providing high efficiency, long life span and easy integration with renewable energy resources the price and installation costs are so high that it is beyond the reach of domestic users. In the end suggestions are provided about how the prices of DC LED systems can be brought down.
Seo, In-Jin,Khan, Umer Amir,Hwang, Jae-Sang,Lee, Jong-Geon,Koo, Ja-Yoon Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3
<P>High-voltage direct current (HVDC) technology is considered to have some important advantages over traditional high-voltage alternating current, such as higher overall efficiency and smaller power losses for long-distance transmission. In addition, applications of superconducting cables in dc electric power networks may realize real zero impedance, and the economic and technical advantages could be maximized. Therefore, many research institutes have tried to develop advanced superconducting cables for HVDC grids with higher reliability, by considering insulation diagnosis in order to avoid unexpected failures. As one of the plausible diagnostic methods for power cables applied to the ac grid, the detection of partial discharges (PDs) taking place inside the apparatus has been widely investigated. With regard to the related PD pattern analysis, a phase resolved PD analysis (PRPDA), which was first developed in the early 1970s, accounts for the phase information of the applied ac voltage. In 2001, we also proposed a method for pattern recognition, i.e., chaotic analysis of PD (CAPD), that considers three normalized parameters obtained from the values between two consecutive PD pulses: amplitude difference <inline-formula> <TEX-math notation='LaTeX'><TEX>$(P_{t})$</TEX></tex-math></inline-formula>, occurring time difference <inline-formula> <TEX-math notation='LaTeX'><TEX>$(T_{t})$</TEX></tex-math></inline-formula>, and applied voltage difference <inline-formula> <TEX-math notation='LaTeX'><TEX>$(V_{t} ) $</TEX></tex-math></inline-formula>. However, none of the proposed methods of pattern analysis can be employed for PD under dc stress. Therefore, in this paper, we propose a modified CAPD for the related pattern recognition of possible defects inside a joint box and termination of an HVDC superconducting cable. PDs are produced from four artificial defects and are then detected by a self-designed and fabricated sensor, for which the analysis was performed based on our newly modified CAPD.</P>