  The high R/X ratio of typical distribution systems makes the system voltage
vulnerable to the active power injection from distributed energy resources
(DERs). Moreover, the intermittent and uncertain nature of the DER generation
brings new challenges to the voltage control. This paper proposes a two-stage
stochastic optimization strategy to optimally place the PV smart inverters with
Volt-VAr capability for distribution systems with high photovoltaic (PV)
penetration to mitigate voltage violation issues. The proposed optimization
strategy enables a planningstage guide for upgrading the existing PV inverters
to smart inverters with Volt-VAr capability while considering the
operationstage characteristics of the Volt-VAr control. One advantage of this
planning strategy is that it utilizes the local control capability of the smart
inverter that requires no communication, thus avoiding issues related to
communication delays and failures. Another advantage is that the Volt-VAr
control characteristic is internally integrated into the optimization model as
a set of constraints, making placement decisions more accurate. The objective
of the optimization is to minimize the upgrading cost and the number of the
smart inverters required while maintaining the voltage profile within the
acceptable range. Case studies on an actual 12.47kV, 9km long Arizona utility
feeder have been conducted using OpenDSS to validate the effectiveness of the
proposed placement strategy in both static and dynamic simulations. Index Terms
