Inverter-based black start of domestic loads: behavior and inrush current

When a portion of the low-voltage grid is islanded from the main grid (due to a fault on the upstream grid or maintenance), a temporary re-energization solution is necessary. For environmental purposes and security of supply improvement, distribution system operators are also investigating alternative re-energization solutions to the currently used mobile diesel generator, such as local photovoltaic sources and batteries if available. The black start of such an inverter-based microgrid faces many challenges, especially regarding the limited short-circuit current of small-size residential PV inverters. Since telecommunication systems and load monitoring schemes might not be available during emergencies, the re-energization process needs to be designed based on the natural behavior of loads. This paper investigates how inverter stress can be reduced during the re-energization of households, while not being able to monitor the load. For that, domestic load transient measurements are conducted and assessed as a function of their impact on the stability of the considered microgrid. Then the use of a voltage ramp as a transient mitigation strategy is analyzed based on three load categories. The work is based both on detailed electromagnetic transient (EMT) models and on measurements conducted with real-life loads in an experimental facility.