A novel hybrid quasi-Z-source inverter topology and its modulation strategy

In view of the fact that the number of units required for the symmetric quasi-Z source cascaded H-bridge increases rapidly with the increase of the number of output levels and the switching frequency of the quasi-Z source inverter is multiplied during the insertion of the shoot-through signal of the traditional modulation method, a novel hybrid quasi-Z-source inverter topology and a modulation strategy are proposed. The topology consists of a quasi-Z-source cascaded H-bridge inverter (low-voltage unit) and a traditional H-bridge inverter (high-voltage unit). For the modulation strategy, the improved trapezoidal wave (ITPWM) is adopted as the modulation wave of the high-voltage unit (working at the fundamental frequency), and the step-wave method is utilized for modulation; for the low-voltage unit, the multi-modulation wave phase-shift modulation method is used for modulation, and the modulation wave of the low-voltage unit is shifted up and down, and the shoot-through signal is implanted into the switching moment of the inverter switch. Simulation and experimental results show that by the new topology and modulation strategy proposed in this paper, the number of quasi-Z sources cascaded H-bridge units can be significantly reduced, the switching losses can be greatly reduced, and the utilization rate of DC voltage can be increased. The maximum efficiency can reach 95.92%. Compared with the traditional modulation strategy, the efficiency is increased by 1.83%, and the DC voltage utilization rate is increased by 19.19%.