Real and reactive power flows in a distribution feeder due to inverters with unity power factor

Under the current practice of IEEE 1547-2003, inverters in distribution systems are not permitted to regulate voltage at the point of common connection; that is, they do not injection reactive power, only real power. In distribution feeders with high levels of inverter penetration, this can lead to a situation where some or most of the real power needed by the feeder is provided by the local inverters but all of the reactive power is provided by conventional sources (shunt capacitors and/or the local substation). This counter-flow of real and reactive power is an unusual situation and this paper seeks to examine this scenario and determine if feeder operation needs to be altered in any way due to this counter-flow. The study is performed by running a variety of cases on the IEEE Comprehensive Feeder Model, varying the amount and location of real power injection. The results from these simulations show that real and reactive counter-flow is not a significant issue and that no significant changes to feeder operation need to be made at high levels of inverter penetration.