Novel Space Vector Modulation Method for the Quasi-Z-Source Asymmetrical Three-Level Inverter

The quasi-Z-source (QZS) asymmetrical three-level inverter (ATLI) can be regarded a post-fault topology of the QZS T-type three-level inverter. Due to the inherent limitation of this topology, the output states are restricted, and the conventional modulation methods are not applicable any more. This brief presents a novel space vector modulation (SVM) for the normal operation of the QZS ATLI. Depending on whether the medium vector is included, the sectors of the space vector diagram (SVD) are categorized into two types. According to the sector type, different combinations of basic vectors are selected to generate the correct ac output voltage, and the appropriate shoot-through states are properly adopted to implement the dc voltage boosting. Additionally, to guarantee the neutral-point voltage (NPV) balance, the effective small vectors are selected, whose duty cycles are adjusted in different sectors. The detailed calculating process of duty cycles and arrangement of switching sequences are provided. The effectiveness of the proposed method is verified by experimental results.