A reliability constrained load balancing procedure for neutral current reduction in distribution systems

An important problem to address in radial distribution systems (RDS) is unbalanced loading among the phases. Unbalanced loading causes unequal phase currents, which in turn give rise to deviation in phase voltages and neutral current. A methodology to address unbalance is proposed in this work. Residential consumers are modeled to have rephasing capability with a momentary interruption in service, which is used for the strategic rephasing of residences. This rephasing capability is exploited starting from the terminal buses, where residences are rephased from overloaded to underloaded phases. Any unresolved unbalance is addressed in upstream buses. Type-III distributed generators (DGs) are allocated at highly unbalanced locations. DGs are installed to supply a current proportional to the unbalance present in each phase and address the current unbalance locally. The system is reconfigured using particle swarm optimization (PSO) with minimization of neutral current as the primary objective. When residential buses are relocated to relatively downstream positions, balancing is able to perform better. These three steps are performed in four different sequences, and the best solution is chosen. Finally, the reliability of the system is quantified in the context of momentary interruptions due to rephasing. The effectiveness is demonstrated using the IEEE 33-Bus system.