Research and Development of Solid Static Transfer Switching for Duplex Feeding

Voltage sag has become the main culprit to high quality power supply. Solid Static Transfer Switch (SSTS) for duplex feeding is a kind of power device which can effectively alleviate the voltage sags. SSTS will switch sensitive loads to the alternate source with better power quality when the preferred source is suffering voltage sags or interruption. In this paper, the operational principle of SSTS is introduced at first. The dq transfer + low frequency pass filter will be employed for voltage sag detection. The detection technique finds a balance between the fast response and robustness. Authors will give a novel switching technique to speed up the switching performance based on forced commutating and thyristor voltage detection. Finally, the validity and efficiency of the strategy is verified by using the electromagnetic transients simulation. The switching period can be limited within 5 ms which will not cause malfunction of sensitive loads.