Observer-based Distributed Self-triggered Secondary Control of Multi-bus DC Microgrid Over Directed Communication

Dynamic consensus-based average state observation is a common method for distributed secondary control (SC) of multi-bus microgrids. However, this method requires high communication and computation frequency, and currently available methods for static average consensus are not applicable for dynamic consensus. Meanwhile, it is not considered that the unbalanceness of directed networks can result observation and SC errors. Therefore, an observation- based distributed self-triggered SC strategy is proposed in this paper. First, a dynamic consensus-based distributed average state observer is designed for DC microgrids, and the convergence under weight-balanced directed networks is proved. Decentralized observation-based SC is designed and the SC structure is proved to be equivalent to a virtually fully connected network with good dynamic performance. Then, a distributed self-triggered mechanism is proposed to achieve intermittent communication between generator - generator and generator - networked sensors as well as intermittent SC computation, thus proving Lyapunov stability. Finally, a trigger time corrector is designed to improve the self-trigger response speed. MATLAB/Simulink simulations show that the proposed method can reduce communication and update frequencies of SC by 95% and 75% in quasi-steady states compared with periodical SC. Furthermore, it reduces the trigger frequency by 54.6% compared with currently available method. The communication and computation burden can be effectively lowered, and system practicability as well as reliability can be significantly improved.