Mobile QR Code QR CODE : The Korean Institute of Power Electronics
Title The State of Charge Estimation for Lithium-Polymer Battery using a PI Observer
Authors Junwon Lee ; Jongmin Jo ; Sungsoo Kim ; Hanju Cha
DOI 10.6113/TKPE/2015.20.2.175
Page pp.175-181
ISSN 1229-2214
Keywords Lithium-polymer battery; State-of-charge; PI observer; Battery parameter estimation
Abstract In this study, a lithium polymer battery (LiPB) is simply expressed by a primary RC equivalent model. The PI state observer is designed in Matlab/Simulink. The non-linear relationship with the OCV-SOC is represented to be linearized with 0.1 pu intervals by using battery parameters obtained by constant-current pulse discharge. A state equation is configured based on battery parameters. The state equation, which applied Peukert’s law, can estimate SOC more accurately. SOC estimation capability was analyzed by utilizing reduced Federal Test Procedure (FTP-72) current profile and using a bi-directional DC-DC converter at temperature (25 °C). The PI state observer, which is designed in this study, indicated a SOC estimation error rate of ± 2% in any of the initial SOC states. The PI state observer confirms a strong SOC estimation performance despite disturbances, such as modeling errors and noise.