Enhancing voltage optimization in distribution networks through flexible operation of EV parking lots

This study focuses on the use of consumption flexibility provided by a parking lot (PL) equipped with charging stations for electric vehicles to improve the voltage control in distribution networks. A methodology is presented in which PL offers both upward and downward flexibility of power consumption, provided that energy recovery is guaranteed in subsequent time intervals. To define the flexibility offered by the PL, the proposed approach uses a stochastic optimization model that computes the day-ahead absorption profiles and the maximum allowable flexibility for each 15-minute interval, expressed in terms of the power adjustment capability of the PL in response to the distribution system operator (DSO) request. The DSO then optimizes the voltage profile of the distribution network using the power flexibility offered by the PLs, as well as by other distributed energy resources (DERs). A multiperiod horizon is used in the voltage optimization problem to account for the effects of energy recovery in subsequent intervals. The results are presented for simulations of 24-hour operation of the IEEE 123-node test feeder with four flexible PLs and 15 DERs, whose reactive powers can be varied. The results for two days show an improvement of approximately 70% in terms of voltage profiles in comparison with the case without any voltage optimization, with 30% of the specific contribution of PLs compared to only DERs optimization. The full recovery in terms of the energy provided by each PL is verified, and a cost analysis from the DSO perspective is presented.