Hybrid Control of Networked Battery Systems

Battery systems are inherently networked systems, in which battery cells or packs are grouped by serial and parallel connections to meet power and capacity specifications. In realtime operation, battery packs must be controlled collaboratively so that their capacities can be fully utilized. By employing both analog charge/discharge currents and discrete-event bypass switches in networked battery systems, this paper develops a new hybrid control methodology to control the states of charge (SOCs) and optimize performance. The paper first establishes necessary and sufficient conditions for controllability under hybrid control mechanism. These conditions are then used to derive control strategies to achieve coordinated SOC control, state consensus, and performance optimization. Control algorithms are developed, their convergence properties proved, and optimality established. Simulation examples are used to demonstrate the methods and their performances using a production battery system.