Power-quality improvement by static voltage booster

Among all the various types of possible disturbances affecting power quality in an electric supply (L e. spikes, frequency shift, harmonics etc.), the voltage dips are one of the most concerning because they can affect the regular operation of several widely diffused sensitive loads categories. Experience proves that most dips are characterized by a residual voltage at the delivery bus, where full outages (or micro-interruptions) are only a small share. A remarkable improvement in the power-supply quality can then be obtained by means of a cheap and simple static voltage booster (SVB), without energy storage, just able to sustain the voltage at the load bus bar during sag transients. In the paper this particular subject is investigated, trying to develop, among the various possible solutions, the most suitable SVB device to meet the target. The SVB dynamic performance has been tested by computer simulation, including the sag detection, control and firing system. In order to estimate the booster practical effectiveness in reducing the voltage sag's consequences, improving so the apparent utility power quality, the standard immunity characteristics of sensitive loads, like computers, and the SVB-compensated voltage transients are compared and discussed.