Devices and methods for disconnecting a grid power source from an electrical distribution system

An electrical distribution system configured to supply electric power to an electric load, the electrical distribution system comprising a feeder for connecting at least one electric load, a battery energy storage system connected to the feeder, and a connection point for connecting a grid power source to the feeder, the battery energy storage system comprising a battery, an electrical switchgear device and an electronic controller, the electrical switchgear device being configured to selectively connect the connection point to the feeder, wherein the electronic controller is configured to implement a virtual-synchronous generator control mode, and wherein the electronic controller is configured to:

• detect an electric fault representative of a power loss event on the grid power source,
• upon detecting an electric fault, automatically open the electrical switchgear device to disconnect the grid power source from the feeder, and
• ensure that the battery energy storage system supplies electric power to the electric load while operating in a virtual-synchronous generator control mode,
• wherein detecting an electric fault comprises detecting a voltage vector shift in voltage delivered by the grid power source, and
• wherein detecting the voltage vector shift in the voltage delivered by the grid power source comprises:
• measuring a duration of each cycle of the voltage delivered by the grid power source for each electrical phase,
• comparing a duration of a current voltage cycle with a duration of a previous voltage cycle,
• identifying a change in a voltage vector angle, and
• identifying that a power loss condition has occurred if the change of the voltage vector angle exceeds a predefined threshold angle value.