Plug-in hybrid electric vehicles (PHEV), while they are plugged-in, support the grid a distributed storage. With the advent of smart grid along with the developed communications related with it, PHEV could contribute to ancillary services such as frequency adjustment. An excellent service for PHEV is frequency regulation supply as the duration of supply is short. Moreover, with regard to the fact that frequency regulation is the highest priced ancillary service, the owners of vehicles benefit from PHEV financially. A reliable frequency measurements can be achieved by the coordinators of the system that can drive the trustworthy local automatic generation control (AGC) signals for vehicles which are participating in vehicle-to-grid (V2G) operation. A V2G controller as well as PHEV coordinator are extra controllers which estimate the battery state, recommended level of supply, and user preferences for V2G participation. The simulation part uses three sequences of cases for regulation supply when a sudden change in loading is detected: Providing frequency regulation using central generating units, using aggregate PHEVs storage as a contribution to primary regulation, and finally utilizing the storage as a contribution to primary as well as secondary regulation. Keywords: Plug-In Hybrid Electric Vehicle, Frequency Regulation, Automatic Generation Control, Area Control Error.