Patent ID: 8310104

Claim:
A method for connecting an inverter having an output voltage, frequency, and phase, to an AC grid having a grid voltage, frequency, and phase, while supporting a local load, comprising: matching the inverter output voltage with the grid voltage; matching the inverter output frequency with the grid frequency; matching the inverter output phase with the grid phase; and while the inverter output supports a local load, electrically connecting the inverter output to the grid; wherein: the inverter is connected to the grid through an LCL filter that has an LCL filter ratio, where the LCL filter ratio is the ratio of the grid-side AC peak voltage to the inverter-side AC peak voltage; the inverter has a DC input; and at least after the connection is made, the voltage at the DC input is higher than the product of the peak voltage of the grid AC wave times the ratio of the LCL filter.