Distributed Secondary Control Method for Islanded Microgrids With Communication Constraints

In this paper, a two-layer model for islanded microgrids with communication constraints is proposed, where a key component of the model is a top layer communication network composed of agents over the bottom layer microgrid. Agents on the communication network collect present states of distributed generators to which they connect and exchange information with neighbors according to the asynchronous communication protocol. Furthermore, a systematic method is presented to derive a set of control laws for agents from a given communication network. However, communication constraints, such as packet losses, may occur on the communication network. Therefore, a power estimation term is employed and added into the control laws in order to alleviate the negative impact on the performance. Furthermore, two theorems are proved, which ensure the power balance in the system and the proportional outputs of distributed generators, while the proposition gives the convergence of the control laws with the power estimation term. Finally, simulations are carried out and the results show that the fluctuations of the frequency and voltage are small and meet the requirements, when fluctuations of load demand and environmental conditions are considered. Moreover, the proportional outputs of distributed generators still can be achieved, even if the probability of packet losses is high.