A NOVEL METHOD AND SYSTEM OF CAPACITOR VOLTAGE BALANCING OF A THREE-PHASE NEUTRAL-PONT CLAMPED BI-DIRECTIONAL RECTIFIER

摘要

A new method and system of balancing DC-bus capacitor voltages of a three-phase neutral-point clamped bidirectional converter using minimum number of switching transitions of optimized switching sequences is disclosed. The present invention describes how the capacitor voltage unbalancing in neutral-point clamped converters can be balanced by virtue of changing the number of sampling periods within each sector & its regions depending upon amount of DC-bus capacitor voltage unbalance. Since each sampling period is associated with respective vectors and their time of implementation, thus changing the number of sampling periods within each sector & its regions" changes the effective time of implementation of various vectors resulting in balancing of capacitor voltages. As number of sampling periods per cycle and switching sequence within each sampling period is unaltered, voltage balance is achieved at minimum number of switching transitions for a selected switching frequency.