Research On The Three-phase Current Source Sepic Iverter

As the core of energy conversion and control in photovoltaic power generation system,the performance of the inverter affects the safety,stability and efficient operation of the entire photovoltaic system.The current source inverter has a buck-boost capability,which makes it more suitable for dealing with large variations in input voltage of photovoltaic power generation systems.However,the conventional current source inverter needs to use a larger value of the inductor on the DC side to obtain a stable output,resulting in an increase in the overall volume of the inverter,a decrease in power density,and also affecting the service life of the inverter.In this paper,the three-phase current source Sepic inverter is taken as the research object,and its modulation mode is improved to solve the problem of large inductance value of the DC side of the inverter.The three-phase current source Sepic inverter is integrated with the Sepic circuit and the bridge inverter circuit,so the inverter has the buck-boost ability.At the same time,the inverter has two working modes due to the intermediate inductance current unidirectional and bidirectional flow.In this paper,the working principle of the inverter and its two different working modes are analyzed firstly,and the buck-boost transmission ratios of the two modes of the inverter are mathematically derived.Secondly,this paper proposes a carrier modulation strategy based on the traditional SPWM.On this basis,the open-loop simulation and corresponding analysis of the two operating modes of the inverter are carried out.After that,the mathematical model of the three-phase current source Sepic inverter is also established.The closed-loop parameters and structure of the dual current loop control are designed,and the closed-loop simulation in the two modes is analyzed and verified.Finally,based on the theoretical analysis and simulation of the inverter,the experimental platform of the three-phase current source Sepic inverter is built and the related open-loop and closed-loop experiments are carried out.The correctness and feasibility of the theoretical analysis are verified based on the experimental results.