Review of Distribution Network Phase Unbalance: Scale, Causes,
Consequences, Solutions, and Future Research Direction
Abstract
Phase unbalance is widespread in the distribution networks in the UK,
continental Europe, US, China, and other countries. First, this paper
reviews the mass scale of phase unbalance and its causes and
consequences. Three challenges arise from phase rebalancing: the
scalability, data scarcity, and adaptability (towards changing unbalance
over time) challenges. Solutions to address the challenges are: 1) using
retrofit-able, maintenance-free, automatic solutions to overcome the
scalability challenge; 2) using data analytics to overcome the
data-scarcity challenge; and 3) using phase balancers or other online
phase rebalancing solutions to overcome the adaptability challenge. This
paper categorizes existing phase rebalancing solutions into three
classes: 1) load/lateral re-phasing; 2) using phase balancers; 3)
controlling energy storage, electric vehicles, distributed generation,
and micro-grids for phase rebalancing. Their advantages and limitations
are analyzed and ways to overcome the limitations are recommended.
Finally, this paper suggests future research topics: 1) long-term
forecast of phase unbalance; 2) whole-system analysis of the
unbalance-induced costs; 3) phase unbalance diagnosis for data-scarce LV
networks; 4) techno-commercial solutions to exploit the flexibility from
large three-phase customers for phase balancing; 5) the optimal
placement of phase balancers; 6) the transition from single-phase
customers to three-phase customers.