Hierarchical Operation of Electric Vehicle Charging Station in Smart Grid Integration Applications - An Overview

With the fast development of electrifications of vehicles, EV charging stations are booming in coming years. Meanwhile, the growing demand for charging power, and the stochastic patterns of charging behaviors are creating the scarcity of electricity and significant power fluctuations to the power system. To ensure the system stability and the supply-demand balance of the electricity market, several technical measures are necessary, such as more ancillary power reserve, appropriate demand-side energy management, etc. Moreover, the higher penetration level of renewable energy sources in the conventional power system can be leveraged to sustain the power peak induced by the charging demand with proper system operation strategies. This paper presents an overview of the latest research of EV charging stations and highlights some important issues and challenges in power architectures design, energy storage techniques, control strategies of micro-grid, and energy management optimization. In addition, the hierarchical control system is specifically outlined, which offers decoupled control objectives in different layers of microgrid systems for EV charging. Typical coordinated control techniques and energy management strategies aiming to achieve the optimum performance of EV charging stations are investigated in detail. Further, the future research directions are extensively discussed at the end of this paper.