Analysis of message sequences and encoding efficiency for electric vehicle to grid interconnections

Grid compatibility is a major issue for charging infrastructures of electric vehicles especially in low voltage systems. In order to respect dynamic grid limitations during the charging process, electric vehicles and charging infrastructures have to negotiate charge and grid parameters autonomously. The ISO/IEC Joint Working Group 15118 is working on the Vehicle to Grid Communication Interface enabling user-friendly plug & charge functionality and also allowing for grid compatible charging processes. This paper describes current efforts being conducted in the standardization group, discusses the current state of the protocol in terms of message specifications, and maps various V2G use cases to the current protocol draft. The evaluation focuses on the message exchange patterns between the electric vehicle and the charge spot. Due to the adoption of highly embedded devices in electric vehicles an analysis on the application layer protocol efficiency is provided in this work. It focuses on data encoding efficiency with respect to the current state of the protocol specification. Detailed investigations on physical and data link layers are not part of this work.