Unified Power Quality Conditioner for three phase four wire distribution system

The current paper presents a role of Unified Power Quality Conditioner (UPQC) in 3 phase 4 wire distribution system to improve the power quality. The UPQC is realized by the integration of series and shunt active power filters (APF) sharing a common dc bus capacitor. The realization of shunt APF is carried out using a three-phase, four-leg Voltage Source Inverter (VSI), and the series APF is realized using a three-phase, three-leg VSI. To extract the fundamental source voltages as reference signals for series APF, d-q-0 theory is used. For the control of shunt APF, Clark transformation concept is applied. The performance of the applied control algorithm is evaluated in terms of source neutral current mitigation, mitigation of voltage and current harmonics in a three-phase, four-wire distribution system for different combinations of linear and non-linear loads. The reference signals and sensed signals are used in a hysteresis controller to generate switching signals for shunt and series APFs. MATLAB/Simulink-based simulations that support the functionality of the UPQC are obtained.