PUC9-MMC: A Reduced-Switch-Count Modular Multilevel Converter with DC Fault Current Handling Capability

A nine-level packed U-cell (PUC9) multilevel converter is introduced as a submodule of a modular multi-level converter (MMC) to increase the voltage level by reducing the component counts. This topology would handle the DC fault current without needing the additional DC circuit breaker. PUC9 topology doubles the output voltage levels at the output of MMC with 33% more component counts rather than PUC5. The proposed configuration could be operated as a single DC source single-phase or three-phase multilevel converter with the capability of modularity and scalability. Voltage balancing integrated with level shift pulse width modulation (LS-PWM) technique is applied to balance three flying capacitors (FCs) voltages of each submodule without needing to an external controller. To validate the performance of the converter in transient and steady-state mode, PUC9-MMC is modeled in Matlab-Simulink and the results illustrate the appropriate waveforms in stand-alone mode.