Fuzzy control algorithm for universal active filter

Abstract

In this paper, a fuzzy algorithm is employed to control a three-phase unified power quality conditioner (UPQC). The UPQC is an active filter (AF) and it compensates the reactive power and harmonics in both the voltage and current caused by nonlinear loads. The UPQC makes use of two back-to-back connected IGBT-based voltage source inverters (VSIs) with a common DC bus. One inverter is connected in series while other is placed in shunt with the nonlinear load. The shunt inverter works as a current source and compensates current harmonics caused by nonlinear loads. The series inverter works as a voltage source and helps in compensating the voltage harmonics caused by nonlinear loads. A diode bridge rectifier feeding an R-L load is considered as a nonlinear current load while a source of voltage harmonics is considered in shunt with the load. With a view to examining the steady state and transient performance of the UPQC, a suitable mathematical model of the system is developed. The capability of the UPQC is demonstrated in the filtering of voltage and current harmonics along with the reactive power compensation of nonlinear loads. Simulated results are given and discussed in detail. Experimental results are also given.