Analysis and characterization of an active bypass switch for series connected power conditioners

The thyristor crowbar plays an important role in series connected power converters, as dynamic voltage restorers and active filters, since it allows the bypass of the converter and a direct connection between utility and load in case of failures. In general, the crowbar is specified taking into account the energy that it will be subjected to during a short-circuit downstream the converter, leading to thyristors with current ratings greatly higher than the converter nominal current. The weight, volume and price of the crowbar increase in comparison with a specification based only on the steady-state current. This paper proposes a new methodology for crowbar thyristors specification independently of the short-circuit power of the system where the series converter is installed. Experimental results on a thyristor crowbar under short-circuit corroborate the procedure applicability and effectiveness.