Research On Switched-inductance Z-source Three-level Inverter

With the development of society,a large number of human needs lead to the gradual depletion of global disposable energy,clean and renewable energy occupies proportion bigger and bigger at the same time,and various renewable energy utilization technologies have developed rapidly.Inverter system is the important component and key technology,since the Z source inverter have been proposed,for its unique impedance network and allowance of bridge shoot-through,which provides a new mechanism for the realization of the boost-buck voltage inverter,attracted more and more attention from domestic and foreign scholars.However,due to its small output capacity,and limited boost capacity,the traditional Z inverter is only applicable to low-voltage low-power occasions.This thesis studies a novel Z-source inverter that is termed Switched Inductor Z-Source three-level Inverter.Compared with the traditional source inverter,the topology of the inverter only requires a smaller pass-through duty cycle,which can improve the boost coefficient,has a greater voltage gain,help to improve the output power quality and system performance in high power applications.In this thesis,the working principle and detailed topological structure of SL Zsource three-level inverter are analyzed.First,analyze and compare the traditional Z-source two-level inverter,the conventional Z-sourced three-level inverter and the SL Z-sourced three-level inverter,the results show that the SL Z-sourced three-level inverter has advantages in high power applications.The modulation strategy and the insertion method of the shoot-through vector are analyzed in detail,the shoot-through time can be extended to the next effective vector after optimizing the vector action sequence,and the SVPWM method can be improved and simulated.Next to the neutral-point voltage balance problem has carried on the detailed analysis,found in a switch cycle if inserted Upper Shoot-through time and Lower Shoot-through time on equal inserted straight to no effect on the neutral-point voltage,and then deeply analyses the neutral-point voltage balance control method,introducing the balance factor method is used to analyze the neutral-point voltage balance control.In the end,the paper further studies the inverter DC side of the DC link voltage control,based on state space average method and small signal model set up SL Z source three level inverter DC booster circuit model,and impedance network are analyzed in detail the influence of main parameters on the system dynamic performance,and have good performance of the controller is designed,and the overall design of Z source network.The simulation model is built to verify the system model and the proposed control scheme through MATLAB/simulink.The simulation results show the correctness of the system model and the effectiveness of the proposed controller.