Online Expansion of Multiple Mobile Emergency Energy Storage Vehicles Without Communication

The extreme weather and natural disasters will cause power grid outage. In disaster relief, mobile emergency energy storage vehicle (MEESV) is the significant tool for protecting critical loads from power grid outage. However, the on-site online expansion of multiple MEESVs always faces the challenges of hardware and software configurations through communications. In order to simplify the on-site operation, the online expansion without communication line is always expected to realize the effect of plug-and-play. For this purpose, this article proposes an online expansion method, which focuses on the voltage coordinate control at two key parts to avoid the circulating current: one is for the system reset after new MEESV is joined, while the other one is for the bus voltage synchronously gradually restored to the rated value. For the former one, a mutual small-signal-based resetting method is proposed, for which the injection and identification of small signal are studied to ensure the safe expansion with acceptable disturbances. For the latter one, event-triggered method is suggested which synchronously restores the bus voltage to nominal value at its specific zero crossings. The effectiveness of the proposed methods is validated through an experimental platform, with three prototypes online expanded one by one.