GCDSC-PLL and PAC Based Control of Three-Phase Four-Wire UPQC for Power Quality Improvement

This paper presents amodified p-q theory based unified power quality conditioner (UPQC) connected into a three-phase four-wire (3P4W) distribution system to handle the significant power quality problems viz. voltage and current harmonics, voltage sags and swells, voltage unbalancing, load unbalancing and low power factor due to excessive reactive power demand. A UPQC, which is the consecutive connection of shunt and series active power filters (APFs) combinedly connected to a dc link, is capable of rectifying all the above power quality problems concurrently. The concept of fundamental frequency positive sequence (FFPS) extraction derived from generalized cascaded delayed signal cancellation (GCDSC) technique and p-q theory are integrated in the UPQC control which results into its robust performance under highly undesirable conditions. To lighten the burden of reactive power on shunt APF, reactive power apportion between shunt and series APF is successfully accomplished with the power angle control (PAC)algorithm without hindering the major function of UPQC. The triggering signals for both converters are generated with the help of hysteresis band controller. An elaborated analysis of UPQC performance under dynamic loading condition with linear and non-linear single-phase and three-phaseloads is carried out in the simulation work done on the MATLAB/SIMULINK platform.