Modeling Power Electronic Equipment to Improve Distribution Feeder Current and Voltage Balance

Abstract

Distribution feeder currents and voltages are never perfectly balanced due to unequal load distribution across phases, unbalanced circuit impedances, etc. Excessive current unbalance can increase losses and reduce power transfer capacity. High voltage unbalance is a power quality problem that adversely impacts some loads. Variable single-phase Distributed Energy Resources (DER) have the potential to increase the magnitude and variability of current unbalance potentially making conventional phase balancing approaches ineffective. This paper presents the modeling and analysis of three-phase shunt-connected power electronics equipment that balances voltages and currents by removing the negative- and zero-sequence components. The equipment could be dedicated for phase balancing, or also be used as inverters for other DERs. The effectiveness and requirements of this phase balancing approach are demonstrated using the highly unbalanced IEEE 8500-Node test feeder.