Analysis of Unified Power Quality Conditioner during Voltage Sag and Swell Conditions

This paper deals with a three-phase unified power quality conditioner (UPQC), with a combination of shunt active power filter and series active power filter is used to eliminate supply current harmonics, compensate reactive power, voltage sag and voltage swell compensation on distribution network. The performance of the active power filter mainly depends on control strategy used to generate reference current for shunt active power filter (APF) and generate reference voltage for series active power filter. The unified power quality conditioner can work in zero active power consumption mode, active power consumption mode and active power delivering mode. The mathematical analysis is based on active power flow and reactive power flow through the shunt and series active power filter, where in series active power filter can absorb or deliver the active power whereas the reactive power requirement is totally handle by shunt active power filter alone during all conditions. The effect of load VAR variation and the impact of % sag or swell on the kVA ratings of both shunt and series APF are also analyzed. This analysis can be very useful for selection of device ratings for both shunt APF and series APF .Simulation results of these two active power filters are carried out.