Resistive optimization with enhanced PLL based nonlinear variable gain fuzzy hysteresis control strategy for unified power quality conditioner

Abstract

This paper proposes a Resistive Optimization Technique (ROT) incorporated with enhanced phase-locked loop (EPLL) based Nonlinear Variable Gain Fuzzy (NVGF) hysteresis control strategy for three-phase, three-wire Unified Power Quality Conditioner (UPQC) for compensating current harmonics, reactive power, voltage sag/swell, voltage harmonics and voltage unbalance present in the power system distribution network. This novel resistive optimization control strategy is exploited for reference signal generation for both shunt and series inverter. This proposed algorithm adaptively regulates the DC-link capacitor voltage without utilizing additional controller circuit and makes the control system simple as it does not involve any complex optimization methods. Furthermore, a nonlinear variable gain fuzzy based hysteresis controller is proposed for controlling the hysteresis band, which effectively reduces the band violation and improves the tracking behavior of UPQC during load transient, distortion and unbalanced supply conditions of power system. The proposed control strategy of UPQC is validated through MATLAB/SIMULINK followed by the experimental setup accomplished with real-time-hardware-in the loop (HIL) system OPAL-RT simulator and adequate results are reported after a comparative assessment with the conventional PI and hysteresis controller.