Integration of Electric Vehicles in Distribution Network Considering Dynamic Power Imbalance Issue

The continuous growth of the number of electric vehicles (EVs) poses great challenges to distribution networks. Intermittent and stochastic EV access detrimentally affects the security of the power supply. In terms of unplanned events, EV users might dispersedly plug in or out at any available spot instead of ensuring identical distribution across feeders. This uneven deployment may lead to imbalanced loading conditions among the adjacent feeders. The situation may become worse with increased penetration of the distributed photovoltaic (PV) generation due to the intermittent generation characteristic. This article proposes a novel control scheme to manage the imbalanced power among feeders. In the proposed dynamic power balance system, unbalanced power can be transferred from the heavily loaded feeder to the neighboring feeder that is lightly loaded through tie-line voltage-source converters (VSCs). The tie-line VSCs are designed to connect adjacent feeders at the low-voltage side of distribution transformers via an 800 V dc link. In this way, the power variance caused by either EV or PV can be split into joint feeders and transformers so as to mitigate fluctuations. The stochastic variations on EV charging loads are addressed using a Monte-Carlo simulation technique. The effectiveness of the proposed scheme is demonstrated on a typical distribution network with the integration of EVs and PV. It could be used as a supplementary measure to obtain a fast demand balance response without restraining EV users and to considerably curtail the risk of overloading the power distribution equipment.