Comparison of capacitor voltage balancing techniques in multilevel inverters

Abstract

The diode-clamped multilevel topology has the problem of voltage unbalance of dc link capacitors. This problem can be solved by different methods such as using separate dc sources instead of dc link capacitors, or adding auxiliary circuits to the conventional diode clamped inverter or adopting space vector modulation control, up to three-level inverter applications. For more level applications, the use of separate dc sources is not viable and the control techniques for other two methods will be more complicated to implement. Hence the Hybrid Multilevel Inverter Based on Switched-capacitor and Diode-clamped units can be used for higher levels. This topology can balance the capacitor voltage and also boost the terminal voltage in the output with the help of switched capacitor converter. The boosting of output voltage reduces the transformation ratio of the input transformer or avoids it in low power applications, thereby reducing the cost and design complication of converters. The simulation of this topology is done using MAT lab simulink software and compared with other voltage balancing techniques.