Switched mode power supplies for charge-up, discharge and balancing dc-link capacitors of diode-clamped five-level inverter

Inductor switch mode power supplies (SMPS) operated in a discontinuous inductor current mode are used to balance the dc-link capacitor voltages of a diode-clamped five-level inverter. The SMPS concept is extended to charge up and discharge the four dc-link capacitors. Complete diode-clamped five-level inverter operation is implemented, from start-up, charge-up, balance dc-link capacitors in normal operation, discharge, to shut-down, which have not been presented before. Ramped start of a controlled rectifier sourcing a boost converter limits the lowest dc-link capacitor inrush current and control its charging time. SMPS in conjunction with the boost converter are used to control the dc-link capacitor charge-up and discharge times. The proposed inverter complete operation is validated by simulation and practically.