Statistical evaluation of voltage unbalance in residential distribution networks with a high penetration level of small wind turbines

Voltage unbalance (VU) in residential distribution networks (RDNs) is mainly caused by the load unbalance in three phases, resulting from network configuration and time variation of the loads. The increasing penetration of small wind turbines (SWTs) and their non-uniform distribution over the three phases have introduced difficulties in evaluating possible VU. In this paper, the point estimate method (PEM) is applied to evaluate the possible VU in RDNs with different SWT penetration and distribution scenarios. Randomness of load switching by customers and time-variation of wind speeds have been taken into account. The methodology has been applied to a generic UK distribution network. Results show that a balanced penetration of SWTs over three phases reduces the VU of a RDN. A scenario where 40% of homes in one phase have SWTs installed would result in a voltage unbalance factor (VUF) out of UK statutory limits.