Control method and apparatus to reduce current through DC capacitor linking two static converters

The invention relates generally to AC power converters, typically in AC power supplies used to drive AC motors which use one or more power cells having a first converter to convert input AC power into an intermediate DC link, a capacitor connected across the intermediate DC link for smoothing, and a second converter to convert the DC power into output AC power. More particularly, the invention relates to a control method to reduce the current through the capacitor in the link between the two converters. A control method and apparatus to reduce current through a DC capacitor linking two converters causes the value of the DC-side current output of the first converter to approach the value of the DC-side input current into the second converter, thus minimizing the DC capacitor current which is equal to the difference between the output current from the first converter and the input current into the second converter.