Reliable Control of Direct PWM AC-AC Buck Converter With Short Circuit Protection

In this paper, a reliable control strategy is proposed for the direct pulse-width-modulation (PWM) ac-ac buck converter, to address the commutation problems and also to offer a handling capability against short circuit faults. A number of states are defined for the switching of the ac-ac converter depending on the sensed input voltage, whereby safe and continuous current paths are maintained at all times including voltage zero-crossing points. Moreover, fault handing switching states are able to protect the converter against short circuit currents. Safe transitions between different states are achieved as well. The realization of the control method is introduced and analyzed in detail. Measured results from experiments confirm that the proposed strategy manages to provide a safe and smooth operation for the ac-ac buck converter even under short circuit faults.