Three-level low-modulation-degree carrier modulation method

The invention discloses a three-level low-modulation-degree carrier wave modulation method, which comprises the following steps of: when the modulation degree is relatively low, simultaneously performing positive bias on three-phase modulation waves of a three-level frequency converter in a current carrier wave period, and then changing the bias direction of the three-phase modulation waves once every one carrier wave period. Furthermore, in each switching period, the biased three-phase modulation wave is compared with the two triangular carrier waves which are stacked in an inverted mode, and a switching sequence of all power switching tubes in each switching period is obtained. The method is easy to implement and high in reliability, the switching frequency of a device is not increased while the minimum pulse width problem in the low modulation degree is solved, and it can be guaranteed that the average value of the output line voltage is not distorted. 本发明公开一种三电平的低调制度载波调制方法，当调制度较低时，将当前载波周期中三电平变频器的三相调制波同时进行