A control strategy based on UTT and I Cos&#920 theory of three-phase, fourwire UPQC for power quality improvement

Abstract

This paper presents a control strategy for a three-phase four-wire Unified Power Quality (UPQC) for an improvement of different power quality (PQ) problems. 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 ICosO theory 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 and voltage dips in a three-phase four-wire distribution system for different combination of linear and non-linear loads. In this control scheme, the current/voltage control is applied over the fundamental supply currents/voltages instead of fast changing APFs currents/voltages, thereby reducing the computational delay and the required sensors. MATLAB/Simulink based simulations results are obtained, which support the functionality of the UPQC.