A centralized electric vehicle charging scheme based on user satisfaction fairness and cost

Abstract

Recently, the penetration of electric vehicles (EVs) has been expected to increase rapidly. From the power grid point of view, a large number of EVs could act as a large amount of load as well as energy storage. To avoid jeopardizing the stability of electric power grid, a charging mechanism for EVs should be properly managed. Many researchers have investigated centralized charging algorithms. However, to the best of our knowledge, none of them have discussed about the user satisfaction fairness among EV users. In this thesis, we propose two new metrics to represent the EV user satisfaction fairness. The metrics are used to define the satisfaction fairness among EV users.

To guarantee obtaining an optimal solution, we convert an non-linear optimization problem into a linear optimization problem through linear approximation. The linear optimization is a general model that can accommodate various satisfaction level metrics. We investigate a tradeoff between the user satisfaction fairness and the total cost of electricity for charging. Results show that we may need higher total electricity cost even with a smaller deviation of EV users` satisfaction, especially with higher fairness among EV users at a given time. Through the proposed scheme, EV users can achieve a much higher satisfaction level for almost all the times, compared to the conventional scheme. The proposed scheme can also ensure a higher level of battery state-of-charge (SOC).

To be more practical, we also propose a real-time charging scheme considering the satisfaction fairness. The real-time charging scheme can reduce the complexity of the system and it is more practical. We compare the performance of the 1-hr real-time charging scheme with the 24-hr optimization scheme.

We also evaluate the performance of the proposed charging scheme in diverse environments: apartment complexes, companies, and shopping malls. The results in different environments show the similar trend in terms of the satisfa...