State-of-energy Balancing Strategy for Lithium Battery Based on Droop Control

The traditional P-f droop control has a wide range of applications but cannot balance the energy state of lithium iron phosphate batteries in microgrids. The existing SOE balancing schemes have not solved the SOE balancing problem under P-f droop control. In response to this issue, this article proposes an SOE balancing scheme for lithium iron phosphate batteries in an isolated microgrids based on P-f droop control. The internal relationship between droop control and SOE is studied, and the traditional P-f control parameters are redesigned. A consistency algorithm is introduced to solve the SOE balancing adjustment term so that the active power output by the lithium iron phosphate battery inverter is repeatedly distributed according to the initial state of the lithium iron phosphate battery SOE. Under the premise of less communication and ensuring good frequency quality, SOE balancing is achieved during the charging and discharging process between lithium iron phosphate battery packs in the isolated microgrids. In addition, the system's stability under different control parameters is studied by analyzing the small signal model of the proposed scheme. Finally, the PSCAD simulation results verify that the proposed scheme can achieve SOE balancing during lithium iron phosphate batteries' charging and discharging process with good scalability and robustness against communication interruptions.