Variable nonlinear gain fuzzy with improved synchronous reference frame control strategy for performance enhancement of unified power quality conditioner

Abstract

This paper proposes a variable nonlinear gain fuzzy (VNGF) controller and negative-feedback based phase-locked loop (NFPLL) with improved synchronous reference frame (ISRF) control strategy for unified power quality conditioner (UPQC). Several power quality (PQ) problems present in the power distribution network can be exterminated through the proposed VNGF-NFPLL-ISRF control method. The VNGF method employs Takagi-Sugeno Fuzzy (TSF) type numerical consequent rule with a nonlinear alteration of variable control gain for controlling dc-bus capacitor voltage of UPQC, which limits the voltage deviances through the power system perturbations and delivers quick settling time for dc-bus voltage. The scheme of NFPLL based synchronization is built upon presenting a negative-feedback control action in the interior loop of conventional PLL and hence a greater extent of protection to grid as well as load disturbances, unresponsive to noise, harmonics and additional contaminations existing through the signal can be attained. Moreover, the novelty of ISRF control method relies upon nonintervention with low pass filter (LPF) and high pass filter (HPF). As a consequence, the proposed VNGF-NFPLL-ISRF control technique quickly and accurately extracts the reference signal during power system perturbations. The effectiveness of the proposed approach is experimentally validated and a comparative survey has been accomplished with conventional TSF controller based SRF method (TSF-SRF).