Multi-objective optimization PWM control for a back-to-back five-level ANPC converter

Five-level active neutral-point-clamped (5L-ANPC) converter is a newly emerging topology which can overcome the drawbacks of traditional diode-clamped and flying-capacitor multilevel converters. This paper introduces a transformer-less medium-voltage motor drive system consisting of two 5L-ANPC converters connected back-to-back (BTB). Both the rectifier and inverter are based on phase-disposition (PD) sinusoidal pulse width modulation (SPWM). A multi-objective optimization PWM control method based on zero-sequence voltage injection is presented in this paper. The neutral-point (NP) potential can be balanced by injecting proper zero-sequence voltages. In addition, by further limiting the region of the injected zero-sequence voltages, the series connected IGBTs can operate at fundamental frequency and the amplitude of common-mode voltage can be reduced to a quarter of the DC-link voltage. Experimental results are presented to verify the validity of this method.