Novel Quasi-Z-Source Inverter with High-Frequency AC Link of High-Proportion Renewable-Energy Power System

Z-source/quasi-z-source inverters can make up for some limitations of traditional voltage-/current-source inverters. In recent years, more and more research has been carried on z-source/quasi-z-source inverters, but most of them are unable to realize input/output galvanic isolation. The proposal of high-frequency isolated z-source/quasi-z-source inverters greatly enriches the topological family of this type of converter but places relatively high voltage stress on the capacitors. In this paper, a novel circuit topology of a quasi-z-source inverter with a high-frequency AC link of a new high-proportion power system is proposed. The operating principle and abnormal operating states, such as discontinuous-conduction mode (DCM) operation and abnormal states caused by component failures, are analyzed. The double closed-loop control strategy is analyzed and designed, and a grid-connected photovoltaic system based on the inverter is designed. The experimental results verify that the presented inverter has advantages such as high-frequency electrical isolation, bi-directional power flow, lower voltage stress on the capacitors, etc.