Aggregation of plug-in electric vehicles in distribution networks for primary frequency control

Plug-in electric vehicles (PEVs) have great potential in the near future to be connected in a large number to the power systems. This will lead to influence the overall dynamic behavior of power systems, specifically when PEVs participate in the primary frequency control (PFC). Modeling a large number of PEVs for PFC can be a complex and time consuming task. In order to reduce computational complexity, in [1], we proposed that a large number of PEVs was represented by an aggregate model which was connected to the transmission system. In [1], in the aggregate model of PEVs for the frequency stability analysis, the distribution network has been neglected, although in reality PEVs will be dispersedly connected to the distribution network. This paper proposes an aggregate model of PEVs that incorporates distribution network characteristics, i.e. the power losses. Thus, the proposed aggregate model represents the active power response of PEVs taking into consideration distribution network power losses (DNPL). To achieve this goal, the DNPL increment, which is caused by the participation of PEVs in the PFC, is mathematically formulated with respect to the active power variation of PEVs following a disturbance. Then, the proposed aggregate model of PEVs is obtained according to the PEV fleet behavior and also the calculated power loss variation. In order to compare the detailed model and the proposed aggregate model, the simulations are carried out in Matlab / Simulink. Finally, the simulation results show high level of correspondence between the detailed and the proposed aggregate model of PEVs following a disturbance in the power system.