The existence of large-scale power electronic equipments will lead that the fault characteristics of the system are not only affected by the topology

but also affected by the control strategy. This paper discusses the modeling method first. Based on the fault characteristics and new protection principles of the classify study

the thinking of methods of analyzing the fault characteristic of power system with large power electronic equipments are put forward

the development trend of new protection principles is summarized. Finally

in view of the importance of converter control strategy in the system

the ideas of coordinating control and protection are suggested. This work is supported by National Natural Science Foundation of China(No. 51477131)and Key Project of Smart Grid Technology and Equipment of National Key Research and Development Program of China(No. 2016YFB0900603).