An Improved Methodology for the Hierarchical Coordination of PEV Charging

Angel M. Sanchez,Gustavo E. Coria,Andres A. Romero,Sergio Raul Rivera

doi:10.1109/access.2019.2943295

Abstract

This paper proposes an improved methodology for the hierarchical coordination of daily Plug-in Electric Vehicle (PEV) charging. The aim is to limit the power supplied by the primary distribution transformer (PDT) while minimizing the energy costs of the aggregators. This methodology consists of an iterative optimization of the total aggregated power at the PDT level, considering the local power constraints of the aggregators and the PEVs with a reduced number of decision variables and constraints which only depend on the number of time intervals. Moreover, it defines the energy boundaries of the optimization problem in each iteration through a proposed method for simulating early charging and delayed charging, considering the power constraints of the aggregators. Otherwise, it evenly distributes the total power among the aggregators, and the local power of each aggregator among the PEVs, maximizing the feasible region of the optimization problem. The proposed methodology is applied to two case studies. The uncertainties related to the charging scenarios are considered by means of Monte-Carlo simulations. The results obtained show that the total power profile is effectively limited, while the profits of the aggregators are not significantly affected by the coordinated approach that is expected to be performed by the Distribution System Operator (DSO). Additionally, to demonstrate the reduction of the impact of PEV charging on the distribution system, the voltage profile, the transformer loss of life and the power and energy losses are reported.

Highlights

Nowadays, society, in general, seeks a technological revolution to reduce the environmental pollution produced by the conventional transportation system, which is based on internal-combustion engines [1]
The aim of the Distribution System Operator (DSO) is to constrain the total power supplied by the primary distribution transformer (PDT), i.e. the baseload power (BL) and the power demanded by Plugin Electric Vehicle (PEV) chargers, to its rated value, while the profit of the aggregators is maximized
This methodology minimizes energy costs of the aggregators while constraining the power supplied by the PDT to the medium voltage grid and the power supplied by the secondary distribution transformers (SDT) to the aggregators

Summary

Introduction

Society, in general, seeks a technological revolution to reduce the environmental pollution produced by the conventional transportation system, which is based on internal-combustion engines [1]. The technology available for such a revolution is based on plug-in electric vehicles (PEVs). The massive connection of PEVs to the distribution networks will have a significant impact, which may be negative if the recharging of the PEV batteries is not properly coordinated. A methodology to coordinate the recharging of multiple PEVs, in a distribution grid, is proposed. The methodology considers a power constraint imposed by the primary distribution transformer (PDT) that supplies the medium voltage grid. The fulfillment constraint is achieved through the coordination of aggregators that manage the PEV charging systems plugged into low voltage networks. Power constraints due to the SDTs are considered

Methods

Results

Conclusion