  Increasing distributed energy resources (DERs) may result in reactive power
imbalance in a transmission power system (TPS). An active distribution power
system (DPS) having DERs reportedly can work as a reactive power prosumer to
help balance the reactive power in the TPS. The reactive power potential (RPP)
of a DPS, which is the range between the maximal inductive and capacitive
reactive power the DPS can reliably provide, should be accurately estimated.
However, an accurate estimation is difficult because of the network
constraints, mixed discrete and continuous variables, and the nonnegligible
uncertainty in the DPS. To solve this problem, this paper proposes a robust RPP
estimation method based on two-stage robust optimization, where the uncertainty
in DERs and the boundary-bus voltage is considered. In this two-stage robust
model, the RPP is pre-estimated in the first stage and its robust feasibility
for any possible instance of the uncertainty is checked via a tractable problem
in the second stage. The column-and-constraint generation algorithm is adopted,
which solves this model in finite iterations. Case studies show that this
robust method excels in yielding a completely reliable RPP, and also that a
DPS, even under the uncertainty, is still an effective reactive power prosumer
for the TPS.
