A Sinusoidal Pulse Width Modulation (SPWM) Technique for Capacitor Voltage Balancing of Nested T-Type Four-Level Inverter

This paper introduces a novel control method based on the sinusoidal pulse width modulation(SPWM) scheme to regulate the capacitor voltages of a four-level T-type NNPC inverter. The four-level Ttype NNPC inverter features a reduced number of switches and components compared to other traditionaland advanced four-level inverters, making it a compelling choice for high-power, medium-voltageapplications. This topology has been analyzed under the assumption of constant DC sources rather thanflying capacitors. A simple single-phase modulator is developed to balance the voltages of the flyingcapacitors. The performance and feasibility of the proposed control technique are experimentally evaluatedunder steady-state and transient conditions, as well as for various modulation indices and loads.Experimental results confirm the effectiveness of the control method in regulating the capacitor voltages.