Voltage sag is a frequently occurring power quality problem as it may significantly affect industrial production. The unified power quality conditioning system is used to mitigate voltage sag under different fault condition. In this paper to study the operation of MC-UPQC system used in distribution system. The main purpose of multi-converter unified power-quality conditioning system (MC-UPQC) is capable of simultaneous compensation for voltage and current imperfection in multibus/multifeeder systems. In this configuration, one shunt voltage-source converter (shunt VSC) and one series VSCs exist. The system can be applied to adjacent feeders to compensate for supply-voltage imperfections. The IEEE 16 node test feeder, which is a highly loaded unbalanced system, is used in the study. The UPQC consists of a three-level inverter with IGBTs and PWM control. Modelling and simulations are implemented in Mat lab/Simulink.

Keywords - multi-converter unified power-quality conditioning system (MC-UPQC), Unified power-quality conditioner (UPQC), voltage sag, voltage-source converter (VSC), Unbalanced Radial Distribution Systems.