Coordinated PEV charging and its effect on distribution system dynamics

Increased market penetration of plug-in electric vehicles (PEVs) will enable a shift in the transportation sector towards more sustainable energy options. However, PEV battery charging represents a significant additional burden on power systems, especially at the distribution level where the radial structure of the network may accentuate the effects of load variations. Furthermore, uncoordinated PEV charging could cause transformers to regularly operate beyond their thermal limits, increasing their likelihood of failure. Coordinated charging, based on distributed control methods, has been proposed as a means of mitigating voltage fluctuations and transformer overloads. Recent research can be divided into two categories: studies into the effects of static PEV loads on distribution networks, and development of control algorithms that vary PEV charging to accomplish specific goals. This paper combines these two ideas by analyzing distribution network load flow dynamics in response to a large population of coordinated PEVs. An IEEE 34-node distribution test feeder is simulated in conjunction with a fleet of PEVs under Additive-Increase Multiplicative-Decrease (AIMD) control. The resulting scheme ensures that all loads are satisfied, while controlling PEV demand to meet secondary considerations such as voltage regulation and transformer capacity limits. However, detrimental oscillations may develop under certain conditions. The paper investigates the cause of these unwanted variations.