Distributed event-triggered multi-timer synchronization scheme for secondary control in islanded microgrids

Abstract

Consensus-based distributed control has been widely applied in the secondary control for microgrids (MGs) with the assumption that the control actions of each distributed generations (DGs) are triggered at the same time as others in the state-of-art literature. However, in the absence of centralized timer synchronization, the asynchrony resulting from the independent timer localized in each DG would inevitably undermine the system performance or even cause instability. This paper proposes a distributed time synchronization strategy to guarantee the update actions of individual DGs to be triggered at the same discrete instants. First, the asynchrony problem in the distributed secondary control due to the essential distributed characteristic is elaborated and the resultant convergence deviation is deduced. Then, the distributed time synchronization strategy based on pinning consensus is described, with the optimal pinning timer selected to achieve superior propagation performance. Further, the event-triggered mechanism is introduced, which reduces the communication burden significantly compared to the time-driven mode and maintains the global clock synchronization efficiently. The selection of event triggering threshold is formulated for the tradeoff between the trigger frequency and convergence accuracy. The effectiveness as well as flexibility of the proposed control strategy is demonstrated by simulations.