Modelling and control design of three phase-four wire UPQC for power quality improvement

Unified power quality conditioner is the combination of series active power filter and shunt active power filter. the purpose of series active power filter is to compensate source side distortions. purpose of using shunt active power filter is to compensate load side distortions. the neutral current flow is considered to be major distortion in distribution system.inorder to harmony the load current and neutral current flow,three phase four wire distribution is used. fourth leg is used in the shunt part of the inverter for neutral flow current. unbalance is considered to be serious issue in transmission and distribution system. by using upqc above problem can be overcome. hysteresis controller is mainly used to control the gating pulses of the inverter. the simulation results based on matlab/simulink are presented to show the effectiveness of the balanced load current in three phase four wire distribution.