A 3-D SVPWM without medium vectors for 3-phase 3-wire 3-level rectifier

摘要

In this paper, the high frequency mathematical model based on controlled objects of tri-phase tri-wire diode-clamped tri-level rectifier in tri-dimensional αβγ coordinates has been presented. This mathematical model shows that switch function Sγ has only effect on the voltage difference of up and down capacitor in DC side and has no effect on line current in AC side and DC output voltage. Therefore, a novel 3-D space vector PWM has been suggested in which medium vectors have been eliminated and its vector region has only been divided into 12 tri-prisms. The simulating results show that the presented mathematical model and control strategies are correct, the self-balance of neutral point potential (NPP) has been received, and the NPP has been controlled in quantity too. Although the NPP is floating in tri-phase tri-wire tri-level rectifier system, the proposed PWM is still simpler because of no medium vectors. This PWM is fit for tri-level inverter too.