SOH Balancing Scheme of Distributed Battery Energy Storage System in AC Microgrid Based on Improved Droop Control

Droop control is usually applied to the control of distributed battery energy storage system (DBESS) inverter in islanded AC microgrid to realize automatic load sharing and autonomous operation of microgrid. State of charge (SOC) balancing scheme is usually used in battery management system of microgrid to extend the service life of DBESS. However, the conventional droop control and SOC balancing scheme cannot realize the SOH balancing of DBESS. SOH unbalancing will reduce the service life and increase the maintenance burden of DBESS. Besides, the existing SOH balancing schemes are not based on droop control, require the central controller and cannot achieve the SOH balancing among DBESS packages. Therefore, a SOH balancing scheme based on improved P-f droop control is proposed. In this scheme, multi-agent technology is introduced, and each DBESS is regarded as one agent. Through the interaction of depth of discharge (DOD) information among DBESS agents, the output active power of DBESS inverter is adjusted according to the state of SOH. Then, the SOH balancing among DBESS packages is realized. Finally, the simulation and experimental results verify the effectiveness of the proposed scheme.