A fleet of vehicles can provide regulation services at 30-second intervals by controlling the rate of charging. We show how to choose the size of the regulation contract such that cars in a fleet will still meet their charging demands on time, while still making the most money by doing so. Access the paper here:

H. Zarkoob, S. Keshav, and C. Rosenberg. Optimal Contracts For Providing Load-Side Frequency Regulation Service Using Fleets of Electric Vehicles, J. Power Sources, vol. 241, pp. 94-111, November 2013.