  This paper presents a method to obtain a convex inner approximation that aims
to improve the feasibility of optimal power flow (OPF) models in distribution
feeders. For a resistive distribution network, both real and reactive power
effect the node voltages and this makes it necessary to consider both when
formulating the OPF problem. Inaccuracy in linearized OPF models may lead to
under and over voltages when dispatching flexible demand, at scale, in response
to whole-sale market or grid conditions. In order to guarantee feasibility,
this paper obtains an inner convex set in which the dispatchable resources can
operate, based on their real and reactive power capabilities, that guarantees
network voltages to be feasible. Test simulations are conducted on a standard
IEEE distribution test network to validate the approach.
