Distributed Secondary Control for Battery Energy Storage Systems in AC Microgrids under Multiple Time-Varying Communication Delays

This paper addresses the challenge of designing a fully distributed secondary control strategy for heterogeneous battery energy storage systems in a microgrid with the objective of achieving consensus in frequency and active power, while preserving a balanced state of charge, subject to multiple time-varying communication delays. The problem is addressed in a multi-agent fashion where the local controllers of the distributed generators play the role of agents, and communication is affected by time-varying delays. The proposed approach exploits a combination of integral sliding mode control and a linear consensus protocol. Lyapunov analysis is presented to assess the stability properties of the closed loop. Delay-dependent stability conditions are expressed as a set of linear matrix inequalities whose solution yields appropriate control gains such that the control objectives are achieved despite multiple time-varying delays. The effectiveness of the proposed control strategy is assessed through simulations.