Investigation on the Performance of UPQC System based on Five and Seven-level NPC Inverter Topologies

This article presents an investigation on the performance of unified power quality conditioner (UPQC) system based on five and seven-level neutral point clamped (NPC) inverters, using similar strategy to identified current or voltage references and analogue control approaches for switching pulses generation via combined phase disposition-sinusoidal pulse width modulation (PD-SPWM) and fuzzy logic control scheme. The UPQC system is adopted to compensate the current source harmonics and all voltage disturbances simultaneously. It is designed by the combination of series and shunt active power filters (APFs) connected by a common DC link capacitor. The DC voltage bus is maintained constant, using proportional integral voltage controller. The synchronous reference frame (SRF) detection method is used to get the shunt APF reference signals and the instantaneous reactive power (p-q) theory for the series APF. The shunt and series active power filter (APF) reference signals, derived from the control algorithm, are injected in fuzzy controllers to generate switching signals. The functionality of both UPQC systems is evaluated using Matlab-Simulink software and SimPowerSystem Toolbox in presence of various voltage disturbances. The numerical simulation results show the efficacy of proposed UPQC based on five and seven converter topologies and confirm the superiority of UPQC system using seven-level (NPC) inerter in term of harmonic current compensation compared to UPQC system based on five-level (NPC) topologies.