A Control Strategy Based on UTT and PBT of Three-Phase, Four-Wire UPQC for Power Quality Improvement

Abstract

This paper presents a novel control strategy of a three-phase four-wire Unified Power Quality (UPQC) for an improvement in power quality. The UPQC is realized by integration of series and shunt active power filters (APFs) sharing a common dc bus capacitor. The shunt APF is realized using a thee-phase, four leg voltage source inverter (VSI) and the series APF is realized using a three-phase, three legs VSI. A control technique based on unit vector template technique (UTT) is used to get the reference signals for series APF, while power balance theory (PBT) is used for the control of Shunt APF. The performance of the implemented control algorithm is evaluated in terms of power-factor correction, load balancing, neutral source current mitigation and mitigation of voltage and current harmonics, voltage sag and swell in a three-phase four-wire distribution system for different combination of linear and non-linear loads. The reference signals for the shunt and series APF of UPQC are derived from the control algorithm and sensed signals are used in a hysteresis controller to generate switching signals for shunt and series APFs. MATLAB/Simulink based simulations are obtained, which support the functionality of the UPQC.