In order to tackle the existing problems in power grid

we propose the concept of software defined grid by incorporating the software defined idea for the first time. And we analyze the characteristics of software defined grid featuring the separation of part or all of the grid management

operation and control. Then we delimit the detailed advantages of software defined grid

illustrate the architecture of software defined grid consisting of three layers and two interfaces between layers

and detail the functionality of each layer and interface. Finally

we demonstrate two applications of concept of software defined grid

which are mainly on the power distribution network and virtual power plant to show the advantages of software defined grid.