Power Quality Enhancement with UPQC Systems Based on Multi-level (NPC) Inverters

This paper proposes a novel control scheme for Unified Power Quality Conditioner (UPQC) based on five-level (NPC) inverter able to mitigate source current harmonics and compensate all voltage disturbances. The UPQC is designed by the integration of series and shunt active filters (AFs) sharing a common dc bus capacitor. The dc voltage is maintained constant using conventional proportional integral voltage controller. The synchronous reference frame strategy control is used to get the reference signals for shunt APFs and the instantaneous reactive power theory for a series APFs. The reference signals for the shunt and series APFs are derived from the control algorithm and sensed signals are injected in two LS-SPWM controllers to generate switching signals. The performance of proposed UPQC system is evaluated using MATLAB-Simulink program and SimPowerSystem Toolbox for different disturbances condition. The simulation results show that the proposed UPQC system can improve the power quality.