An Improved Modulation Strategy for the Three-Phase Z-Source Inverters (ZSIs)

Z-source inverters (ZSIs), compared to the conventional two-stage architecture, embrace some interesting features, like the reduced size and complexity of the entire conversion system. Many research activities have been established to improve the performance of the so-called ZSI since it has been proposed in 2003, and several modifications have been introduced since then. These modifications include the structure of the ZSI, i.e. modifying the topology itself, and its modulation scheme as well. From the modulation perspective, the existing modulation strategies suffer from some demerits, such as the increased number of switch commutations at high current during the entire fundamental period and the utilization of extra reference signals. In this paper, an improved modulation strategy is proposed in order to enhance the performance of the three-phase ZSIs and the equivalent topologies. The proposed modulation strategy, which is called simple-boost modified space vector (SBMSV) modulation, reduces the number of switch commutations for shorter period during the fundamental cycle, simplifies the generation of the gate signals by utilizing only three reference signals, and achieves a single switch commutation at a time. This modulation strategy is analyzed and compared to the conventional equivalent modulation strategy, where a reduced scale 1 kVA three-phase ZSI is designed and simulated using MATLAB/PLECS models. Finally, the designed 1 kVA three-phase ZSI is implemented experimentally in order to verify the proposed modulation strategy, the reported analysis, and the simulation results.