  Photovoltaic (PV) smart inverters can regulate voltage in distribution
systems by modulating reactive power of PV systems. In this paper, an
optimization framework for optimal coordination of reactive power injection of
smart inverters and tap operations of voltage regulators for multi-phase
unbalanced distribution systems is proposed. Optimization objectives are
minimization of voltage deviations and tap operations. A novel linearization
method convexifies the problem and speeds up the solution. The proposed method
is validated against conventional rule-based autonomous voltage regulation
(AVR) on the highly-unbalanced IEEE 37 bus test system. Simulation results show
that the proposed method estimates feeder voltage accurately, voltage deviation
reductions are significant, over-voltage problems are mitigated, and voltage
imbalance is reduced.
