Research On Small Signal Modeling And Stability Of Meshed DC Microgrid

As an important part of distributed generation system,DC microgrid can accept distributed power and load more efficiently and reliably when the power system is connected to power electronic converter.With the expansion of the scale of DC micro grid,some new problems have been brought.For example,the stability of the system under different grid structures is different,the influence of controller parameters combination of different power sources on the stability of the whole system.To solve these problems,the main work of this paper is as follows:(1)In order to analyze the influence of different grid structures on DC microgrid,the small signal models of converters and DC lines on the power and load sides are established,the oscillation modes of the system under different grid structures are studied,and the interaction between the state variables of the system under different structures is explored according to the participation factor method.Thirdly,based on the root locus of the system,the influence of source side,load side and line parameters on the stability of different grid structures is studied.(2)Based on the participation factor and system characteristic root,the stability region analysis method is proposed to study the influence of multiple system parameters on system stability.The results show that due to the interaction of the source network load,the stability region of the controller parameters of the power supply is different under different network parameters.When the network parameters are symmetrical,the stability region of the controller parameters is symmetrical;when the network parameters are asymmetrical,the stability region of the controller parameters is no longer symmetrical.By optimizing the configuration of the controller parameters of different power sources,we can obtain greater stability margin and more power output under the condition of meeting the power quality.(3)By analyzing the stability region of the meshed DC microgrid system,it is found that the main factor affecting the stability of the system is the interaction between the source networks.The interaction between source and load is mainly reflected in the total size of the load,and the power distribution of different loads has a weak impact on the stability.(4)In view of the above theoretical analysis,based on the established DC microgrid simulation model,matlab time-domain simulation verification is carried out.