A Single-Phase Switched-Capacitor Nine-Level Inverter With Reduced Capacitance

A novel nine-level switched-capacitor multilevel inverter (SCMLI) with reduced capacitance and balanced capacitor voltage is proposed in this article. Utilizing only two capacitors, the proposed SCMLI can boost the input voltage and realize nine output voltage levels under different kinds of load conditions. The controllable capacitor charging speed in the proposed SCMLI depends on the charging resonant inductor rather than the equivalent resistance of the devices in conventional topologies. The two capacitors can be charged or discharged independently by a dc source when their voltages deviate from the rated voltage. This makes the proposed SCMLI free of the capacitor voltage imbalance. The longest discharging time (LDT) of capacitors is reduced to twice the switching period, which contributes to reduced capacitance in the proposed SCMLI. With the required capacitor voltage ripple, the quality of output waveforms is also very high. A comprehensive comparison with previous SCMLIs in terms of capacitance, the voltage imbalance problem, the output voltage level, and so on is conducted to validate the merits mentioned above. The theoretical analysis, the simulation, and experiment results are accordant, confirming the feasibility of the proposed SCMLI.