Research On A Dual-input Quasi-Z Source Inverter

In recent years,the supply of fossil energy has become increasingly tight,and the degree of environmental damage has become increasingly serious.At present,all countries in the world are actively developing green energy,and inverters play an important role in it.However,most of the inverter products on the market are buck type,and dead zone time must be added in the control signal,which seriously affects the quality of the output waveform and increases the cost of the filter devices.The proposal of the Quasi-Z source inverter has solved these problems.Afterwards,the research of multi-input Quasi-Z sources has further advanced the development of Z-source inverters,but most of its main circuits achieve high voltage gain by increasing energy storage elements,making these topologies appear high-order and resulting in complex working status,being in difficulty to build models and to select appropriate control strategies.In this thesis,a circuit topology of dual-input Quasi-Z source inverter is designed.The circuit does not increase the number of energy storage elements.It also has the characteristics of high voltage gain and the advantages of applying multiple control strategies.The working principle is analyzed,and the mathematical expressions of the relevant parameters are derived.The state-space average model and small signal method are used to derive the transfer function of the inverter’s main circuit,which provides a theoretical basis for the selection of elements such as capacitors,inductors.Four control strategies for the dual-input Quasi-Z source inverters are introduced.The working range of the inverter and the voltage stress of switching devices under different control strategies are calculated.The current stress of the switching devices under three shoot-through modes is derived.Among them,the current stress is the largest in the single-phase shoot-through mode and the purpose of this data is to select the type of switching devices and of the RCD buffer circuit;the current stress is reduced to a minimum by the three-phase shoot-through mode.The four control strategies are simulated and compared by MATLAB.Through theoretical analysis and simulation results,the relatively superior segmented shoot-through control strategy was selected for experiment,and the experimental results verified that the dual-input Quasi-Z source inverter has a simple structure and has the advantages of achieving a high voltage gain without additional energy storage elements.