Compensation of voltage sags in a radial network feeding a thyristor bridge controlled load

Voltage sags are very frequent events associated with faults in the network, or with common operations like the energization of transformers or the starting of large size motors. Although their duration is very short, they can represent a critical problem for industrial plants, especially for those characterized by the presence of adjustable speed drives or, more generally, of sensitive loads, like power electronics devices. In this paper, a static series compensator (SSC) has been connected in a radial network feeding a thyristor bridge rectifier controlled load, for the compensation of voltage sags. The whole system has been simulated with the aid of the electromagnetic code PSCAD-EMTDC and the obtained results show that it is particularly suitable for those cases where the unsymmetrical faults are the responsible for the failure of the thyristor pulse logic, thus resulting in a substantial decrease of the DC voltage.