A Sinusoidal Pulsewidth Modulation (SPWM) Technique for Capacitor Voltage Balancing of a Nested T Type Four Level Inverter
In this letter, a new control method based on the sinusoidal pulsewidth modulation scheme is proposed to control capacitor voltages of a T type four level nested neutral point clamped (NNPC) inverter. The T type four level NNPC inverter has a lower number of switches and components compared with other four level classic and advanced inverters, which make this topology attractive for high power medium voltage applications. This topology has been proposed and studied with the assumption of constant dc sources instead of flying capacitors. In this letter, a simple single phase modulator is developed to balance flying capacitor voltages. The performance and the feasibility of the proposed control technique are evaluated experimentally under a steady state and transient conditions and for different modulation indexes and loads. The experimental results demonstrate the effectiveness of the developed control method to control the capacitors' voltages.
IEEE Transactions on Power Electronics