Accurate estimation of the capacity and state of charge of an energy storage system used in wind farms

An apparatus for estimating an aged capacity of a battery in an energy storage system (ESS) associated with a plurality of wind turbine generators, the apparatus comprising:

• at least one processor configured to:
• determine an internal impedance of the battery;
• determine an approximate age of the battery based on the internal impedance;
• determine a relationship between a maximum capacity corresponding to the battery and a number of charging cycles;
• determine the aged capacity of the battery based on the approximate age and the relationship;
• determine a state of charge (SOC) of the battery;
• and
• determine an available energy remaining in the battery based on the SOC and the aged capacity.

A system comprising:

• one or more of wind turbine generators;
• at least one battery for storing energy produced by the wind turbine generators;
• and
• at least one processor configured to:
• determine an internal impedance of the battery;
• determine an approximate age of the battery based on the internal impedance;
• determine a relationship between a maximum capacity corresponding to the battery and a number of charging cycles;
• determine an aged capacity of the battery based on the approximate age and the relationship;
• determine a state of charge (SOC) of the battery;
• and
• determine an available energy remaining in the battery based on the SOC and the aged capacity.