Patent ID: 7948306
Filing Date: 2011-05-24
Classification: G03G

Abstract:
1. An active line filter comprising: an ac line input: an ac neutral connection point; an ac line output; a first switching configuration including a first transistor and a second transistor operatively connected in series; a second switching configuration including a third transistor and a fourth transistor operatively connected in series, and an energy buffer operatively connected to the ac neutral connection point and ac line output, the energy buffer being a capacitor with a positive terminal and a negative terminal and an energy buffer voltage across the capacitor is regulated by a DC controlled amplifier, wherein the active line filter is configured to measure a momentary ac line output current, measure a momentary ac line input current, switch the energy buffer to provide additional current to the ac line output when the momentary ac line output current is greater than the momentary ac line input current and switch the energy buffer to draw current from the ac line input when the momentary ac line output current is less than the momentary ac line input current, and wherein the capacitor is operatively connected in parallel to the first and second switching configurations and the first switching configuration is operatively connected to the ac line output to switch the capacitor at a predetermined duty cycle for providing the additional current to the ac line output when the measured ac line output current is greater than the momentary ac line input current and switch the capacitor at the predetermined duty cycle to draw current from the ac line input when the momentary ac line output current is less than the momentary ac line input current.