Systems and methods for islanding protection

A system comprising:

• a distributed energy resource;
• and
• a connection device coupled to the distributed energy resource to control distribution of power from the distributed energy resource to an electrical grid, wherein the connection device is configured to:
• measure voltage and current at a connection point between the distributed energy resource and the electrical grid;
• determine a Thévenin impedance of the electrical grid based upon the voltage and current measurements;
• set a predetermined threshold, wherein to set the predetermined threshold comprises to:
• determine a first range of possible values for the Thévenin impedance under a normal condition using a computer simulation;
• determine a second range of possible values for the Thévenin impedance under an islanding condition using a computer simulation;
• and
• determine whether an overlap exists between the first and second ranges of possible values for the Thévenin impedance;
• and
• determine whether the Thévenin impedance has exceeded the predetermined threshold.