A NOVEL MULTI LEVEL CONVERTER UNIFIED POWER - QUALITY (MC - UPQC) CONDITIONING SYSTEM ON LINE LOADING, LOSSES, AND VOLTAGE STABILITY OF RADIAL DISTRIBUTION SYSTEMS

This paper presents a new unified power - quality conditioning system (MC - UPQC), capable of simultaneous compensation for voltage and current in multi - bus/multi - feeder systems. In this configuration, one shunt voltage - source converter (shunt VSC) and two or more series VSCs exist. The system can be applie d to adjacent feeders to compensate for supply - voltage and load current imperfections on the main feeder and full compensation of supply voltage imperfections on the other feeders. In the proposed configuration, all converters are connected back to back on the dc side and share a common dc - link capacitor. Therefore, power can be transferred from one feeder to adjacent feeders to compensate for sag/swell and interruption. The proposed topology can be used for simultaneous compensation of voltage and current imperfections in both feeders by sharing power compensation capabilities between two adjacent feeders which are not connected. The system is also capable of compensating for interruptions without the need for a battery storage system and consequently witho ut storage capacity limitations. The performance of the MC - UPQC as well as the adopted control algorithm is illustrated by simulation. The simulation results show that a significant amount of power - loss reduction, under voltage mitigation, and the enhancem ent of voltage stability margin can be obtained with an appropriate placement of the MC - UPQC in a distribution network. The performance comparison of the MC - UPQC with one previously reported design approach shows that it is more efficient in under voltage mitigation .