SVPWM-Based DC Voltage Balancing and Fault Diagnosis Method for a Cascaded H-Bridge Multilevel Converter

In the DC voltage balancing control of a cascaded H-bridge multilevel converter, the frequently used PI controllers have complicated parameter tuning and cause the balancing ability to degrade under the switch fault condition. Regarding this, a space vector pulse width modulation-based DC voltage balancing method is presented to flexibly adjust the cell voltage levels and maintain the DC voltage balance between the power cells to the fullest degree. Furthermore, based on the voltage level changes under different switch faults, an active vector transition scheme is used to successively diagnose single or multiple open switch faults in one power cell or different power cells. The simulation and experimental results have shown the effectiveness of balancing algorithm under the normal and fault conditions, and the diagnosis validity for multiple faults.