Research On Series Z-source Inverter Based On Switched Inductor

Microgrid technology is the key to develop and utilize the renewable energy sources such as wind and solar energy.The inverter is the core component of the microgrid,which is the guarantee of the efficient operation of the microgrid,and the medium of energy exchange between distributed energy and the power grid.The traditional voltage source inverter can only reduce the output voltage,in order to achieve grid-connected generation,a level of DC-DC boost link need to be increased,constitutes a two stage grid-connected generation system,the structure is complex and difficult to control.The new topology Z-source inverter can realize single-stage boost by through states,which is apply to single-stage grid-connected power generation system.However,the traditional Z-source inverter has many disadvantages such as large starting current,low gain-boosted and abnormal operating state,and it is not suitable for high voltage gain and large load variation.In order to solve the inrush current,low gain-boosted,and abnormal operating state,the high performance series Z-source inverter based on the switched inductor is proposed,compared to the traditional Z source inverter,it has many advantages including small starting current impact,high step-up voltage gain,and there is no abnormal operating state.Firstly,the series Z-source network and the enhanced Z-source network based on the switched inductor are studied.series Z-source network has the inherent ability to inhibit inrush current;enhanced Z-source network based on the switched inductor can achieve high step-up gain.In this paper,two kinds of structure of inverter are in conjunction and the Z-source inductor of the series z-source inverter is replaced by the switched inductor unit,to constitute series Z-source inverter based on switched inductor so as to solve the starting current impact,low gain-boosted,and abnormal operating state.Secondly,by analyzing 7 kinds of work mode of the series Z-source inverterbased on switched inductor,it can be seen that the improved Z-source inverter does not exist current path like traditional Z-source inverter,restrain impact current intrinsically;Z-source inductor current and the current through the switch tube S-U can reverse flow,and there is no abnormal condition.Then the large-signal model of the improved Z-source inverter is established based on Kirchhoff's law and the state averaging method,and according to the small-signal perturbation method,the small-signal model of the improved Z-source inverter is established to realize the control of DC-link voltage.Finally,in order to verify the advantages of the high performance series Z-source inverter based on switched inductor,such as small starting current,high voltage gain and no abnormal working state,a SIMULINK simulation platform for high performance series Z-source inverter based on switched inductor is built in this paper,to compare with traditional Z source inverter.Compared with the traditional Z-source inverter,the improved Z-source inverter has high voltage gain,and the starting current is small.