《Seamless Transfer of Single_Phase Grid_Interactive Inverters》.pdf

IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 25, NO. 6, JUNE 2010 1597 Seamless Transfer of Single-Phase Grid-Interactive Inverters Between Grid-Connected and Stand-Alone Modes Zhilei Yao, Lan Xiao, Member, IEEE, and Yangguang Yan Abstract—This paper presents a novel seamless transfer of restored. Grid-interactive inverters play an important part in the single-phase grid-interactive inverters between grid-connected and distributed generation [1]–[12]. stand-alone modes. The grid-connected inverter should operate in The grid-connected inverter should operate in grid-tied and grid-tied and off-grid modes in order to provide power to the emer- gency load during system outages. However, the grid current con- off-grid modes in order to provide power to the emergency troller and the output voltage controller are switched between the load during system outages. Moreover, the transition between two modes, so the outputs of both controllers may not be equal the two modes should be seamless to minimize any sudden during the transfer instant, which will cause the current or volt- voltage change across the emergency load or any sudden current age spikes during the switching process. The transfer between the change to the grid. A seamless transfer between both modes has two controllers does not exist in the proposed method. In grid-tied mode, the voltage controller is used for compensating the filter ca- been proposed in [11]. However, the grid current controller pacitor current, and the current controller is used to control the and the output voltage controller must be swit