Duty cycle-based three-level space-vector pulse-width modulation with overmodulation and neutral-point balancing capabilities for three-phase neutral-point clamped inverters

In this study, a duty cycle-based space-vector pulse-width modulation (SVPWM) with overmodulation and capacitor voltage balance control for three-phase three-level neutral-point clamped (NPC) inverters is presented. On the basis of simple linear calculations of three-phase reference voltages, the proposed SVPWM can be derived, which avoids the trigonometry operation required by the conventional SVPWM. The modulation region can also be smoothly extended from the linear region to the overmodulation region through re-synthesising the three-phase reference voltages. This avoids the conventional non-linear function and look-up table. The neutral-point voltage balancing control is achieved via changing the duty cycle of the redundant small vectors in each switching period, which can be easily embedded into the proposed duty cycle-based SVPWM. The dynamic and steady-state performances of the proposed SVPWM are eventually verified by both simulation and experimental results.