A Distributed Coordination Approach for the Charge and Discharge of Electric Vehicles in Unbalanced Distribution Grids
Nanduni Nimalsiri, Elizabeth L. Ratnam, David B. Smith, Chathurika P. Mediwaththe, Saman Halgamuge
Abstract
Distributed-optimization-based approaches for electric vehicle (EV) charging coordination are becoming increasingly important to enable a massive-scale EV rollout without driving costly distribution network reinforcement. This article proposes an algorithm called Dis-Net-EVCD for distributedly coordinated, network-aware EV charging and discharging in unbalanced distribution grids, incorporating both EV customer economics (least cost charging) and distribution network awareness. The alternating direction method of multipliers underpins the development of Dis-Net-EVCD, wherein we seek to remove the need for central coordinating agents and allow EVs to iteratively determine their charge–discharge profiles locally via peer-to-peer communication. Numerical simulations carried out on the IEEE 13-node test feeder with 600 residential EVs demonstrate that EV customers implementing Dis-Net-EVCD yield a total operational cost reduction of 78% compared to uncoordinated EV charging, while conforming with the voltage regulatory requirements and fulfilling all of the EV charging demands ahead of their expected departure times. Moreover, Dis-Net-EVCD is shown to be approximately 60 times computationally faster than its centralized counterpart.