Method for balancing capacitors voltages on split DC-links

Abstract

A technique to actively balance the voltages on series-connected capacitors designated to split DC sources whose loads comprise power converters is presented. It performs such balancing dynamically, enabling the voltage equalization even for small capacitors under wide power and voltages ranges. Proposal consists on lightly controlling the power of one input capacitor for each pair, measuring their voltage difference and, based upon that, generating a single control signal. Thereby, it then controls the power drained individually from that capacitor, whilst the total load remains being supplied by the whole pair. The performance of the proposed capacitor voltage balancing control loop has been demonstrated by means of experimental results of a 300 V-6 kW bipolar-buck (330 V-1500 V supply).