With distributed digital control structure， converters based on power electronics building block（PEBB） are cost low， easy to be reconfigured and highly reliable. The cascaded ring topology is a dominant solution scheme for its communication network. Implementing synchronization among network joints is a key technical problem due to characteristics of the ring network topology. Two synchronization strategies for ring topology network are proposed: one is based on net-clock， and the other is based on time-stamping. For practical application， a contrast analysis between two synchronization strategies are conducted in the aspects of synchronization precision， synchronization speed， resource consumption and stabilization.