  This paper addresses the problem of voltage regulation in a power
distribution grid using the reactive power injections of grid-connected power
inverters. We first discuss how purely local voltage control schemes cannot
regulate the voltages within a desired range under all circumstances and may
even yield detrimental control decisions. Communication and, through that,
coordination are therefore needed. On the other hand, short-range peer-to-peer
communication and knowledge of electric distances between neighbouring
controllers are sufficient for this task. We implement such a peer-to-peer
controller and test it on a 400~V distribution feeder with asynchronous
communication channels, confirming its viability on real-life systems. Finally,
we analyze the scalability of this approach with respect to the number of
agents on the feeder that participate in the voltage regulation task.
