Patent ID: 7541696

Claim:
A voltage sag compensation device, comprising: a first capacitor having a first peak voltage and a second capacitor having a second peak voltage, the second peak voltage being lower than the first peak voltage, the first capacitor and the second capacitor being configured to be charged via an AC rectifier when the voltage sag compensation device is connected to a power line; a first voltage sag detector configured to detect on the power line a voltage sag of a first predetermined value, and a second voltage sag detector configured to detect on the power line a voltage sag of a second predetermined value, the second predetermined value being greater than the first predetermined value; an inverter arranged to transform DC power supplied by at least one of the first or second capacitors into AC power; and control switching, responsive to the first voltage sag detector and to the second voltage sag detector, configured to, upon detection of a voltage sag of the first predetermined value, disconnect the power line from the AC rectifier, disconnect the power line from a load being serviced by the power line, and cause the power line to drive a gating circuit associated with the inverter such that the inverter generates AC voltage that is substantially in phase with AC voltage present on the power line which inverter generated voltage is arranged to be supplied to the load in series with the power line voltage, and further configured to, upon detection of a voltage sag of the second predetermined value, cause the inverter to receive power directly from the first capacitor.