Centralized nonlinear switching control strategy for distributed energy storage systems communicating via a network with large time delays

Abstract

This paper proposes a novel centralized switching controller for the state of charge balancing of battery energy storage systems distributed in a DC microgrid. The main advantage of the proposed controller is that it can tolerate non-uniform and time-varying delays in the communication links between a central processor and each battery energy storage system. The central processor generates predictive estimates of the renewable energy generation/load and state of charge of each battery energy storage. The switching controller uses the predictive estimates to generate participation rates of battery energy storage systems. The proposed control strategy is integrated with the primary droop control and the secondary voltage control for the power sharing and microgrid voltage restoration. In addition, the proposed control method guarantees that the active battery energy storage systems are either charging or discharging thus eliminating circulating currents. RTDS real-time simulator is used to verify the proposed large time delay tolerant control scheme on a DC microgrid with four distributed battery energy storage systems, loads and a PV generation. Moreover, mathematically rigorous analysis of the proposed control scheme is given.