Patent ID: 7787272

Claim:
A controller for controlling a charge and/or a discharge of an energy storage device used in a distributed energy resource, the controller comprising circuitry: to calculate a maximum frequency change for an inverter based on a first comparison between a first power set point and a measured power from the inverter, wherein the first power set point is defined based on a charge level of an energy storage device coupled to the inverter; to calculate a minimum frequency change for the inverter based on a second comparison between a second power set point and the measured power from the inverter; to calculate an operating frequency for the inverter based on a third comparison between a power set point and a measured power flow; to calculate a requested frequency for the inverter by combining the calculated maximum frequency change, the calculated minimum frequency change, and the calculated operating frequency; and to integrate the calculated requested frequency to determine a phase angle of a voltage of the inverter to control a frequency of an output power of the inverter.