Unit Commitment Considering flexible charging of PHEVs

Abstract

In this paper, some boundary charging cases under unidirectional and bidirectional mode are considered to set the upper and lower bounds of the cumulative power delivery to PHEVs. A new index, V-flex has been proposed to quantify the flexibility provided by PHEV fleet to the power system. Empirical driving dataset is used to set up the numerical value of the boundaries. Then, based on the above idea, power constraints and energy constraints of aggregate PHEV fleet charging behavior are incorporated into the formulation of unit commitment (UC). A 10-unit system with different penetration levels of PHEVs is studied to show the benefit of system scheduling considering flexible PHEVs charging. Our study shows that a PHEV fleet used as load shifter can provide more economic benefits than used as a replacement of spinning reserve. It is also identified that the main bottleneck of flexibly using vehicle to grid technology (V2G) in unit commitment is the capacity of the batteries instead of the charging and discharging ability.