An effective SSC control scheme for voltage sag compensation

Voltage sags are very frequent events associated with faults in the network, with energization of transformers or starting of large motors. Although their duration is very short, they can represent a big problem for industrial plants, especially for those characterized by the presence of sensitive loads, like power electronics devices. In this paper, the problem of the design of a device able to compensate voltage sags, namely a Static Series Compensator (SSC), is thoroughly analyzed, both from the point of view of the choice of the components and their rating and from the stand-point of the control system. The model has been implemented with the aid of the electromagnetic code PSCAD-EMTDC and has been tested in a radial distribution network for the protection of a nonlinear load consisting of a diode rectifier.