A New Z Source Inverter Topology And Its Control

Renewable energy generation system is easily affected by the external environment,which is characterized by intermittent,stochastic and volatility.Traditional inverter can not achieve good recombination function in the renewable energy generation system due to its own defects.Z source inverter by introducing Z source impedance network between the DC power supply with inverter bridge,allowing the bridge arm pass straight or open,provides a new mechanism for the inverter to achieve free rise/fall function,it solves the insufficients of the traditional inverter,and has broad application prospects in the field of renewable energy power generation.However,in recent years,as the traditional Z source inverter widely used,the defects such as the weak boost capability,the large capacitance voltage stress,the starting impulse circuit and the abnormal working state are exposed,to this end,topology improvements are needed.Depth analysis based on the characteristics of the improved topology and the intrinsic relationship between topologies,the basic evolution principles were deduced named as location exchanging principle,replacement principle and enhancement principle.Each principle is demonstrated combined with the existing topologies,and its future application is prospected.By using the replacement principle and enhancement principle,a new Z source inverter is proposed,compared with traditional Z source inverter,the new Z source inverter has the advantages of stronger boosting capacity and large range of load adaptation,its topology,working principle and improved characteristics are described in detail.The modulation strategy of the existing Z source inverter is summarized,among them,the improved SVPWM modulation strategy with shoot-through vector,it direct frequency is equal to carrier frequency,when applied in the new Z source inverter,can effectively reduce the switching frequency of the former switch,compared to other modulation strategies,it has obvious advantages.The low frequency mathematical model of the new Z source inverter in two phase rotating coordinate system is established,based on the mathematical model,designed a double closed loop control system,it includes grid connected current inner loop and Z source capacitor voltage outer loop,the control system has good dynamic and steady performance,meanwhile,analyzed three important components of the main circuit parameters.In this paper,the improved characteristics,the improved SVPWM modulation strategy with shoot-through vector and the performance of the grid connected double closed loop control system of the new Z source inverter are simulated,all achieved good simulation results,verified the advantages of the new Z source inverter topology and the designed control system.