Effects of randomly charging electric vehicles on voltage unbalance in micro grids

Unscheduled charging of Electric Vehicles (EVs) may shift voltage unbalance beyond the desired limit. Effects of uncoordinated charging of EVs were assessed by calculating voltage magnitudes and voltage unbalances at the end node of a residential feeder. The assessment was illustrated by presenting loading conditions of distribution transformers and distribution lines. Power losses of these components also have been recorded. Four uptakes of EVs were considered based on the number of EVs per phase. These cases were simulated considering daily profiles of residential loads and EV loads. A 50% EVs uptake has led to an excessive voltage unbalance with a 3-phase 4-wire connection. However, only a 25% EVs uptake caused the violation of voltage unbalance with a 3-phase 3-wire connection. Therefore, 4-wire connections permit more uptake of EVs on the network than 3-wire connections, before voltage unbalances exceed their limits.