A simulation framework for evaluation of real-time electric vehicle (EV) charging control strategy and investigation of Its interaction with V2G-based frequency regulation
Kang, Joo Sung
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Unlike conventional vehicles propelled by internal combustion engine (ICE), an electric vehicle (EV) is powered by an electric motor with rechargeable battery packs. EVs can offer significant potential for increasing energy efficiency in transportation, reducing greenhouse gas emissions, and relieving reliance on foreign oil import. In addition, the large-scale adoption of EVs presents an opportunity to provide electric energy storage (EES)-based ancillary services for ensuring grid-wide frequency stability by smoothing the natural intermittency of renewable energy sources (RES). However, the charging of EVs would have an impact on the distribution grid because they consume a large amount of electrical energy and this demand of electrical power can lead to additional, large and undesirable peaks in the electrical power consumption. Many simulation-based studies have suggested that, if no regulation on EV charging is implemented, even a 10% penetration of EVs may cause unacceptable impacts on the grid. Among a variety of EV charging strategies, the decentralized “valley-filling” approach, which is the most popularly researched, have been shown to be the most versatile for a given daily load profile prediction in that it achieves the maximum load factor and minimizes the daily operating costs of utilities simultaneously. However, the decentralized valley-filling charging strategy has a number of technical limitations that can be resolved by applying the techniques for real-time systems where the satisfaction of timing constraints are as important as the correctness of system outputs. In this research, a real-time scheduling algorithm for EV charging control, which enables EV charging to be controlled in real time without exact knowledge of EV charging profiles as well as to satisfy EV owners' preferences, is proposed, and its technical feasibility and capability to fill the technical gaps of the valley-filling charging strategy are evaluated. In addition, a methodology for incorporating vehicle-to-grid (V2G)-based frequency regulation into the real-time EV charging system is presented, and their interactions are investigated. Furthermore, a simulation framework for developing a real-time EV charging algorithm with V2G-based ancillary services incorporated is presented.