Power quality control of unregulated non-linear loads

Abstract

Increasing non-linear loads cause various undesirable effects and power quality problems on utility supply, like low system efficiency, poor power factor, derating of power supply equipments, disturbance to other consumers and interference in nearby communications networks etc. This work proposes a parallel power processing scheme to improve the power quality of uncontrolled diode bridge rectifier nonlinear loads. In this scheme a single phase synchronous link converter (SLC) is used as an auxiliary converter, in parallel to the diode bridge rectifier having DC capacitor supplying a resistive load, as main converter. Bulk amount of active power flows through the main converter; whereas the auxiliary converter takes care of the harmonics and reactive power requirement of main converter. A power transformer with 2:1 turn ratio is used at the input of the auxiliary converter in order to match the DC output voltages of two converters. The source current reference is derived using a PI controller which uses the output DC voltage feedback. The regulated output voltage is achieved using inner current control loop. The auxiliary converter current is controlled using HCC such as the summation of main and auxiliary converter input currents are sinusoidal and in phase with source voltage. A laboratory prototype experimental set-up with dedicated LabVIEW based controller is developed and tested in laboratory for experimentation. The simulation and experimental results obtained are in agreement.