Optimal carrier based PWM strategy in overmodulation region of three-level inverter

This paper presents the carrier based pulse-width modulation (PWM) strategy in overmodulation region of three-level inverter. The optimal modulation signal is derived from the end of the three-level space vector undermodulation. As the magnitude of modulation signal increases, the modulation mode varies from the end of undermodulation to overmodulation mode-1, and then to mode-2, the waves of phase command voltages and the relation between modulation factor and shifting angle in overmodulation modes are provided. The modulation technique is verified by simulation of three-level inverter with fan load.