  We present a method and tool for evaluating the placement of Distributed
Energy Resources (DER) on distribution circuits in order to control voltages
and power flows. Our previous work described Phasor-Based Control (PBC), a
novel control framework where DERs inject real and reactive power to track
voltage magnitude and phase angle targets. Here, we employ linearized power
flow equations and integral controllers to develop a linear state space model
for PBC acting on a three-phase unbalanced network. We use this model to
evaluate whether a given inverter-based DER configuration admits a stable set
of controller gains, which cannot be done by analyzing controllability nor by
using the Lyapunov equation. Instead, we sample over a parameter space to
identify a stable set of controller gains. Our stability analysis requires only
a line impedance model and does not entail simulating the system or solving an
optimization problem. We incorporate this assessment into a publicly available
visualization tool and demonstrate three processes for evaluating many control
configurations on the IEEE 123-node test feeder (123NF).
