Design of an optimal aggregator for vehicle-to-grid regulation service

Since a possibility for grid-side use of electric-drive vehicles was first claimed, regulation has been proved to be most feasible service by many earlier studies. Moreover, with the emergence of Plug-in HEV, an actual introduction of the regulation service is getting more realistic. To launch the practical service, however, the development of a smart control interface called an aggregator between the grid and the vehicles should be preceded. The main role of the aggregator is, as the name indicates, to synchronize the charge and the discharge operations of multiple vehicles to provide significant amount of power capacity for the regulation service. Consequently, the aggregator has to hold the control of each vehicle. Meanwhile, from the perspective of a vehicle owner, the primary goal of plugging the vehicle into the grid is charging the battery to serve next drive. Since a vehicle that joined the regulation is following the command from the aggregator, it is also the responsibility of the aggregator to perform the desired amount of battery charging. Therefore, the aggregator should have an appropriate strategy to provide regulation service while performing battery charging. In this paper, we assess various aspects of the aggregator, and develop an optimal control strategy for the aggregator regarding a performance measure. Finally, proprieties of the suggested aggregator are verified with simulations.