Electrical systems and methods for islanding transitions

An electrical system comprising:

• a connection arrangement coupled in series between an external electrical grid and an electrical grid interface node;
• a voltage sensing arrangement coupled to the electrical grid interface node to measure a voltage at the electrical grid interface node;
• and
• an energy storage system comprising:
• an energy storage element;
• an inverter module coupled between the energy storage element and the electrical grid interface node, the inverter module having an output coupled to the electrical grid interface node;
• and
• a control module coupled to the voltage sensing arrangement and the inverter module to:
• determine a reference voltage at the electrical grid interface node;
• identify an islanding condition based on the measured voltage relative to the reference voltage;
• determine a target output voltage for the inverter module to counteract an electrical disturbance on the external electrical grid based on the measured voltage relative to the reference voltage;
• and
• in response to the islanding condition:
• operate the connection arrangement to electrically disconnect the electrical grid interface node from the external electrical grid;
• and
• operate the inverter module in a voltage source mode to provide the target output voltage at the output during a time period required for the connection arrangement to disconnect the electrical grid interface node from the external electrical grid.

A method of transitioning a microgrid system to an islanded state, the microgrid system including an electrical grid interface coupled to an external electrical grid via a connection arrangement, the method comprising:

• determining a reference value for an electrical characteristic at the electrical grid interface based on measurements obtained via one or more sensing arrangements;
• identifying an islanding condition based on a difference between a measurement obtained via the one or more sensing arrangements relative to the reference value;
• determining a target output value for a power conversion module coupled between the electrical grid interface and an energy storage element to counteract an electrical disturbance at the electrical grid interface based on the difference;
• and
• in response to the islanding condition:
• operating the connection arrangement to electrically disconnect the electrical grid interface from the external electrical grid;
• operating the power conversion module to provide the target output value for the electrical characteristic during a time period required for the connection arrangement to disconnect the electrical grid interface from the external electrical grid;
• and
• operating the power conversion module to provide the reference value for the electrical characteristic after disconnecting the electrical grid interface from the external electrical grid.