Z-source Inverter Main Circuit

The inverter is widely used in all kinds of conversions. However, the traditional inverter (VSI or CSI) has the conceptual and theoretical barriers and limitations. They are either a buck (VSI) or a boost (CSI) inverter, which limits the output voltage or current. It requires an additional DC-DC converter to boost the output voltage (VSI) or the output current (CSI).In a voltage-source inverter, the upper and lower devices of each phase leg could be gated simultaneously by EMI noise, which would destroy the circuit and decrease the reliability. To avoid the shoot-through state, dead band has to be provided in the control strategy. Nevertheless, a disadvantage of the dead band is that it can bring the waveform distortion. CSI also have some similar limitations.In order to overcome the problems of the traditional inverter, a new type inverter named Z-source inverter was presented. It makes the shoot-through state possible by employing a unique impedance network (Z-network). And this unique impedance network allows the Z-source inverter to buck and boost its output voltage.In this paper, the operating principle and superiority of the Z-source inverter are described firstly. And its main circuit design is analyzed in detail. Based on the analysis of the abnormal operational state of the Z-source inverter, the relationship between the operating status and devices parameters is proposed distinctly. The methods of reducing the stress are discussed through the analysis of the devices voltage and current stresses. At last the simulation and experimental results have been performed to confirm the analysis. They are quite consistent with the theoretical analysis.