Non-linear optimal controller for unified power quality conditioners

A new optimal control strategy for unified power quality conditioners (UPQC) is presented. This strategy is based on feedback linearisation. The UPQC consists of series and shunt converters, where the series converter usually works as a voltage source, and the shunt converter works as a current source. However, it is possible to use the series converter as a current source, and the shunt converter as a voltage source, as utilised in this study. As for this scheme, an optimal voltage angle at load terminals, in order to minimise the converter losses, is proposed. A comparison with the traditional UPQC, where series and shunt converters are considered to be voltage and current sources, respectively, is also presented.