Narrow pulse suppression of high frequency three level converter based on hybrid modulation strategy in low modulation index region

Aiming at the problem of narrow pulse when high-frequency three-level converter operated in low modulation index, limited region of switch pattern in space plane is proposed and a hybrid modulation strategy is designed. The difference function between the working time of the voltage vector and the switching time of the power device was established and the image of the difference function was analyzed in the space vector plane. The narrow pulse regions generated by conventional virtual space vector modulation were analyzed. The region where the difference function value is less than zero is the limited region of the basic voltage vector sequence, in which the voltage vector sequence required by the conventional virtual space vector cannot be realized. The relationship between the switching frequency and the modulation strategy was evaluated by the dimension of the limited region, and the highest switching frequency under different modulation strategies were also given. The hybrid modulation strategy was designed based on the new sector division method in low modulation index region. The voltage vector sequences were designed in different regions to suppress the narrow pulse. The effectiveness of the proposed method is verified by simulation and experimental results. © 2021, Harbin University of Science and Technology Publication. All right reserved.