An approach to minimize the VA size of UPQC-S and its performance comparison

The unified power quality conditioner (UPQC) with injection of voltage with respect to supply current at definite angle (UPQC-S) exhibits unique characteristics as opposed to the injection of voltage in-phase (UPQC-P) or in-quadrature (UPQC-Q) of the supply current. The UPQC-S comprises series and shunt converters. The series converter shares the reactive powers of shunt converter and reduces burden of UPQC under normal operating conditions. The reactive power sharing of a series converter depends on phase angle and, therefore, it has been optimized to minimize the VA size of the UPQC-S. In this work an algorithm is proposed to minimize the VA size of the UPQC-S. The optimized angle is verified using graphical approach under different power factor of the load and also under different voltage sag. Moreover, optimized VA size of UPQC-S is compared with the UPQC-Q and UPQC-P for 0% to 50% of the voltage sag. A comparative analysis is presented to understand the worth of various control approaches of the UPQC. A comprehensive mathematical evaluation is also presented under normal and voltage sag/swell conditions of the AC mains.