Event-Triggered Time Synchronization Strategy for Distributed Secondary Control Considering Time-Varying Delays

Synchronous information interaction is the basis for guaranting the effectiveness of distributed consensus control, which is crucial for realizing the cooperative control of micro-grids. In the absence of a centralized clock for global signal synchronization, each distributed generation (DG) is equipped with its own clock and is independently allowed to execute actions, which is more practical in distributed control; whereas asynchronous information exchange may occur in this case and could degrade the system performance. To address this problem, this paper proposes a distributed time synchronization strategy. First, the asynchronous distributed consensus control is formulated and the time-varying latency during time message transmission is analyzed in detail, which is similar to that in state delivery and would challenge the precision of clock synchronization. Then, an event-triggered time synchronization strategy which is capable to cope with the asynchronous behaviors of various DGs in the face of a delayed message is introduced with the trigger frequency remarkably reduced and the control accuracy as well as stability significantly improved, which is overlooked in most of the state-of-art literature. Furthermore, the design of the event triggering mechanism is discussed to reach a tradeoff between control actions and synchronization precision. Simulation tests are conducted to verify the effectiveness of the proposed methodology.