Influence of large scale integration of electric vehicles on differential protection of distribution lines

With the aggravation of global environmental problems and the continuous promotion of the "double carbon" goal, new energy and electrified transportation have developed rapidly. Electric vehicles (EVs), as a novel type of mobile load or power source, exhibit more pronounced randomness and clustering characteristics compared to photovoltaics, wind turbines, and energy storage systems. The large-scale integration of EV into the power grid significantly alters fault characteristics on protection lines, adversely affecting the performance of current differential protection. This study first explores the basic topology of EV charging stations and then, based on the principle of ratio-restrained current differential protection, proposes guidance strategies to ensure the reliability and safety of grid operations under typical EV discharge scenarios. By reasonably controlling the discharging power of EV, the sensitivity and reliability of current differential protection are effectively enhanced. Finally, a large-scale EV discharging simulation model is developed on the PSCAD/EMTDC platform using a modified IEEE 33-bus test system, validating the impact of EV discharging on differential protection and the effectiveness of the proposed guidance strategies.