飞跨电容三电平逆变器的零共模电压过调制策略及其电容电压控制

This paper proposes a zero common-mode voltage overmodulation (ZCMV-OVM) strategy for flying capacitor (FC) three-level inverters while considering FC voltage balancing. This strategy effectively eliminates common-mode voltage (CMV) while improving output voltage capability with the same dc-link voltage. First, a space vector-based zero common-mode voltage (ZCMV) modulation algorithm is proposed, which synthesizes the reference voltage vector using six medium vectors and one specific zero vector to eliminate CMV. Then, through simple logical judgment and correction of the duty cycles calculated by the ZCMV algorithm, an overmodulation strategy is implemented to overcome the limitation of reduced dc-link voltage utilization in traditional ZCMV modulation algorithms. Furthermore, the accuracy of voltage output is further enhanced through piecewise quadratic function fitting. Finally, an active FC voltage control algorithm and three switching signal adjustment methods are proposed, which ensure the suppression of FC voltage bias and low-frequency fluctuations from the linear region to the six-step region of the ZCMV-OVM strategy, thereby more effectively eliminating CMV. The effectiveness of the proposed strategy was experimentally verified on a surface-mounted permanent magnet synchronous motor platform.