mart grid is a network of integrated information network and power network, which integrates energy and communication system. In smart grid, the power flow in transmission network and distribution network is bidirectional, and reliable bidirectional communication exists in both transmission and distribution lines. Therefore, reliable and fast communication technology is crucial to the successful implementation of future smart grid projects. One of the main challenges facing smart grid is to upgrade the existing traditional "passive distribution network" to "active distribution network" with two-way communication capability.