Research On Photovoltaic Grid Connected System Based On Power Electronic Transformer

The traditional transformer has the advantages of slow transformation speed,poor regulation ability,and large volume to increase the floor area.With the development of all control devices,the power electronic transformer has grown up and developed with the excellent switch performance of all control devices,and its advantages are obvious.The power electronic transformer can completely replace the traditional transformer in many fields,photovoltaic grid connection is one of them.Aiming at the harmonic and power quality problems of photovoltaic grid connection,the power electronic transformer which is more prominent than the traditional transformer is the advantage of this paper.How to make photovoltaic grid connection more efficient and more efficient and optimize the power quality of the power system is the core issue of this paper.Therefore,this paper studies the photovoltaic grid connection system based on the power electronic transformer.How to build a new energy system with the ability of multi energy access and parallel operation with the traditional power grid has become a research hotspot in the field of distributed new energy generation,transmission and transformation.In this paper,the power electronic transformer is taken as the research object,and some key problems of its input stage and isolation stage are studied,and the grid connection method of photovoltaic system is designed.The main contents of this paper are as follows:In this paper,by analyzing the structure and control strategy of each link of photovoltaic grid connected system,aiming at the problems of slow dynamic response and unstable output voltage of photovoltaic power generation system when converting electric energy,a new three-level boost converter is proposed,which combines the output voltage feedback control of independent photovoltaic cells in the front stage of photovoltaic grid connected system with the Z-source complementary control mode,and solves the problems of different power supply The problem of slow dynamic response and unstable output voltage optimizes the performance of the former DC \ DC converter.For the later stage of photovoltaic grid connected system,a current closed-loop control mode of LCL filter inverter based on SPWM combined with fuzzy PI controller is adopted.Through the control strategy of fuzzy PI controller combined with current closed-loop,the dynamic performance and resonance of the system are improved,so that the photovoltaic grid connected system is optimized and improved,and the purpose of photovoltaic grid connected is finally realized.Verify the control method proposed in this paper,build simulation model in Matlab /Simulink module,and prove the feasibility of photovoltaic grid connected system based on power electronic transformer.In order to further verify its control strategy,combined with the actual construction of a small simulation experiment platform,the final completion of the simulation experiment,analysis of the experimental results,verify the feasibility of the system.