Research On Control Strategy Of Z Source Inverter Based On Droop Control

The series of problems such as operational safety brought about by the expansion of the power grid,coupled with multiple pressures such as resource shortage and environmental problems,have led to the rapid development of new energy fields such as photovoltaics and wind power,and distributed power generation methods have emerged.At the same time,droop control has become a research hotspot of the inverter power supply system because of the advantages of easy modularization and high scalability of the inverter parallel system.With the rapid development of renewable energy power generation and other fields,traditional inverters can not satisfy more complex engineering practice because of their inherent defects.Z source inverters,with their unique Z source network,allow the same inverter bridge arm to shoot through or open,effectively overcome the shortcomings of traditional inverters,have become the research focus of theory and practical application,and have great development potential in new energy power generation and other fields.To this end,this paper applies the droop control to the Z-source inverter parallel system,conducts theoretical research and builds the Matlab/Simulink model for simulation verification.Firstly,based on the analysis of the limitations of traditional inverters,the working principle of three-phase Z source inverters is introduced.Six kinds of modulation strategies commonly used in three-phase Z source inverters are summarized.Focusing on the situation of traditional zero-vector equalization and non-uniformity in the shoot-through-segment SVPWM,it is concluded that as long as certain conditions are met,no matter whether the traditional zero-vector equalization or not,the full utilization of the traditional zero-vector by shoot-through time can be realized.The simulation model is built with Matlab/Simulink as the platform to prove the validity of the conclusion.Then,the two parallel control modes of interconnected lines and non-interconnected lines are summarized,and the principle of droop control and parameter selection in the latter are described in detail.The operation principle of parallel system and the causes of circulating current are discussed.It is concluded that the relevant parameters of the parallel Z source inverters need to be adjusted reasonably so that the output voltage amplitude and phase are exactly the same,so as to achieve a good effect on the load current sharing.Finally,taking the single-phase Z source inverter as an example,the main circuit,double closed loop control structure and the output filter parameter design are analyzed,and droop control is applied to parallel systems of two single-phase Z source inverters.The simulation model of the system is built using the platform of Matlab/Simulink.The simulation model of the system is built using the simulation platform of Matlab/Simulink.The simulation results of each module and the whole system model show that the droop control can achieve current sharing,power sharing and good circulation suppression effect regardless of the sudden change of load,and ensure the stable operation of parallel system.The validity of the related theoretical research and the simulation model and the superiority of the parallel system scheme designed in this paper are verified.