Patent ID: 8279649

Claim:
A method for controlling an inverter configured to deliver power from a direct current (DC) alternative energy source to an alternating current (AC) grid at a grid voltage and a grid phase, the inverter including an input converter coupled to an output converter via a DC bus, the method comprising: determining a first amount of power being supplied by the DC alternative energy source; and in response to the first amount of power being less than a predetermined amount of power: (i) disabling the output converter of the inverter, (ii) in response to the AC grid voltage crossing zero volts, determining an estimated DC bus voltage for a future zero-crossing of the AC grid voltage and determining minimum DC bus voltage, and (iii) in response to the estimated DC bus voltage being greater than a predetermined maximum DC bus voltage, enabling the output converter of the inverter to transfer energy from the DC bus to the AC grid such that the DC bus voltage is reduced to approximately the minimum DC bus voltage.