Novel DC link balancing scheme in generic n-level back-to-back converter system

Paper presents a novel DC link balancing scheme for a generic n-level back-to-back system with multi-level diode clamped topologies. The proposed algorithm is generalization of the 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 n-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 the capacitors in DC link network are effectively maintained balanced. The new balancing scheme has been demonstrated in simulations with 5-level, 7-level and 9-level single phase back-to-back systems and it can be extended to any n-level back-to-back system.