Conceptual Study of Unified Power Quality Conditioner (UPQC)

This paper deals with conceptual study of unified power quality conditioner (UPQC) during voltage sag and swell on the power distribution network. One of the peculiarities of UPQC is that it can inject voltage from 0deg to 360deg. Based on this injected voltage phase angle with respect to the utility or PCC voltage phase angle, UPQC can absorb or inject active power. Thus the UPQC can work in zero active power consumption mode, active power absorption mode and active power delivering mode. The series active power filter (APF) part of UPQC works in active power delivering mode and absorption mode during voltage sag and swell condition, respectively. The shunt APF part of UPQC during these conditions helps series APF by maintaining dc link voltage at constant level. In addition to this the shunt APF also compensates the reactive power required by the load and harmonics generated by them. The MATLAB / SIMULINK results are provided in order to verify the analysis