Harmonic Interactive Modeling And Analysis Of Multiple Inverters In Hybrid Grid

In AC/DC hybrid power grid with various types of distributed generation units,distributed energy system needs to realize grid-connected operation through power electronic interface and bus connection.Grid-connected inverter is an important interface between large grid and distributed generation unit,and it undertakes the important task of direct-to-direct current conversion for AC-DC hybrid large grid.The harmonic content of grid-connected current is an important index for the stable operation of distributed generation units and access to large power grids.Harmonic analysis and suppression in hybrid microgrid is one of the hot topics of scholars at home and abroad.LCL filter has good suppression of high-order harmonics,but also has some resonance problems.In this paper,aiming at the harmonic interaction problem of AC/DC hybrid power grid,the harmonic interaction analysis of different grid-connected operation modes is carried out with the emphasis on a variety of distributed generation units composed of three-phase LCL inverters.In order to make the AC/DC hybrid microgrid perfect enough,this paper outlines the system structure and corresponding control strategies of photovoltaic,gas turbine and wind power generation units.At the same time,the current harmonic detection methods of hybrid microgrid are classified and elaborated.Through the simulation operation of AC/DC power grid model,the harmonic characteristics of grid-connected operation of single inverter and multiple inverters are summarized and analyzed.In this paper,the PSCAD/EMTDC electromagnetic transient simulation software is used to build various distributed generation unit modules and public power grid models.Aiming at the typical system structure with multiple LCL inverters connected to the large power grid,the harmonic interaction of distributed generation units after connected to the large power grid is analyzed and summarized in detail through simulation sampling of the model,especially the content of low-order harmonics such as 3,5,7,9 and 11.