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Tuyen, Nguyen Duc,Fujita, Goro,Funabashi, Toshihisa,Nomura, Masakatsu The Korean Institute of Electrical Engineers 2012 The Journal of International Council on Electrical Vol.2 No.1
One operation circumstance in Dispersed Generation (DG) concepts, an island, is formed when one or more DGs and an aggregate of local loads are disconnected from the main grid and then, remain operational as an islanded entity. This condition of islanding is conventionally undesirable. Consequently, the customers will suffer the blackout. Recently, this blackout phenomenon has been eliminating by facilitating islanded operation. This paper presents a passive method in detecting islanding for DGs by measuring the negative-sequence impedance differences between islanded mode and grid-connected mode at the line frequency. Subsequently, the islanded entity is connected to a backup system by Solid State Transfer Switch (SSTS) in order to smoothly and quickly keep electricity available to customers.
A New Boost Type Cascaded Inverter With Single DC Source
Masakazu Muneshima,Hui Zhang,Shohei Tokunaga,Shota Urushibata,Takashi Kodama,Masakatsu Nomura 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
Cascaded multilevel inverters with Y-connection or Delta-connection have been proposed for high voltage applications. However, these topologies always require isolated transformers for each inverter cell, which makes cost high and wiring complex. Furthermore, system weight and volume also increase accordingly. This paper presents two new types of boost type delta-connection cascaded inverters with only a single DC source. Based on it, a suitable voltage control with PWM modulation is also proposed to improve the inverter control performance and DC capacitors voltage fluctuation. Verification has been carried out by simulation with MATLAB.