Modeling, evaluation and optimization of vehicle-to-grid operation

Plug-in hybrid electric vehicle (PHEV) is considered as a promising approach to electric transportation. This paper describes a simulation model of PHEV integration with the grid. This model provides primary PHEV charging and discharging scenarios based on the general PHEV owner behaviors and the typical PHEV charging circuitry configuration. Initially, the uncontrolled PHEV charging scenarios are performed to evaluate the impact of the PHEV loading on the distribution grid operation. The night charging scenario is chosen for detailed analysis and the load flow is used to calculate the power distribution and loss on the 33-bus test power network. The results indicate the inadequacy of current system operation to meet the growing electricity demand from PHEVs. Therefore, an optimal algorithm is proposed for PHEV charging and discharging in a distribution system to minimize the total real power loss. During charging period, the power rate of individual battery charging is coordinated according to the optimal objective and constraints of charger, battery and power grid. Compared to the uncontrolled PHEV charging results, the optimal algorithm can achieve the maximum loss reduction for each charging scenarios. Moreover, voltage drop at each node is limited in a tolerable range while the tightened branch current restrictions are satisfied.