Abstract
This paper investigates the effects of forced commutation mechanism on the solid-state transfer switches of the uninterrupted power supplies (UPSs). The economical mode provides a solution to effectively reduce the loss induced by the switching devices. However, the SCR based bypass switches have a worse dynamics in turn-off characteristic, so the critical load may suffer from severe grid faults for a long time. In this paper, a control mechanism is presented to force thyristor-based switches to be commutated. Besides, this study also shows how different grid faults affect the performance of forced commutation. Finally, the simulation result and laboratory test results are provided to validate its effectiveness.