Novel DC Link Balancing Scheme In Five-Level Back-To-Back Converter System

Paper presents a novel DC link balancing scheme for a back-to-back system with five-level diode clamped topologies. The proposed algorithm is improvement of the variable switching frequency control strategy formerly introduced with the five-level back-to-back system and it relays on measurement of adjacent capacitor voltages which provide information about the potential variation in consecutive nodes of the 5-level DC link network. Subsequently the adequate control signals are used to modify the multi-carrier PWM modulators on the rectifier side as well as on the inverter side respectively. In result, the voltages across all four capacitors in DC link network are effectively maintained balanced. This new control scheme has advantages over the variable switching frequency due to optimization of the switching losses.