domingo, 8 de junho de 2014
Operation Analysis of Bipolar Low-Voltage DC distribution system based on Distributed Generation
Operation Analysis of Bipolar Low-Voltage DC distribution system based on Distributed Generation Han, Tae Hee
Department of Electrical Engineering Graduate School, Myongji University
Supervised by Prof. Byung Moon Han
The DC distribution has higher efficiency than the AC distribution because it easily controls the power flow in the distributed generators, DC load, and battery storage using single power conversion. However, the DC distribution is not easy to block the fault current and it does not have specific standards compared with the AC distribution, which should be prepared through a lot of technical efforts. The DC distribution is divided into unipolar type and bipolar type. The unipolar type has a positive terminal and a negative terminal, while the bipolar type has a positive terminal, a negative terminal, and the ground terminal. Although the structure of unipolar type is simple, the reliability against fault is rather low. On the other hand, the bipolar type has higher transmission capacity and lower rated voltage of the converter, which secures the cost effectiveness. Also it is possible to form a neutral point with advantages of high reliability and stability. In this thesis, many problems that can occur from the operation of bipolar DC distribution in connection with the AC/DC interconnection operation were analyzed. The energy management method for the AC/DC power trade and the operational principle of distributed generator and energy storage were analyzed. In order to analyze the operation and performance of unipolar distribution system, a 3kW-class hardware simulator was built, which is composed of the grid-tied three-level inverter, battery storage, super capacitors, and the voltage balancer. Also the various analysis results through experiments with hardware simulator were described by a variety tests of produces hardware are described.