Online Estimation of Supercapacitor State of Charge Based on Nonlinear Observer

doi:10.16183/j.cnki.jsjtu.2021.210

Abstract

Abstract:

Supercapacitors have the advantages of fast charging and discharging, high power density, and long life, which are widely used in energy storage systems for new energy vehicles. Reliable operation of the system requires the acquisition of its remaining electricity, which is to estimate its state of charge (SOC). Relying on the equivalent analog circuit model of a single supercapacitor, this paper establishes a state-space model of the capacitor second-order nonlinear system with the multi-capacitor terminal voltage in the model as the state, the capacitor input current as the control input, and the capacitor output voltage as the observation output, and contains the leakage current caused by the self-discharge phenomenon. In order to improve the simulation accuracy, different model parameters were identified to characterize the charging and discharging conditions. In this paper, a nonlinear observer algorithm is used to obtain the internal state of the model to realize the estimation of SOC. The results of the charging and discharging experiment show that considering the leakage factor and establishing the charging and discharging model with different parameters, the dynamic characteristics of the supercapacitor can be better simulated, and the nonlinear observer algorithm has a stable tracking ability.

Key words: supercapacitor, state of charge (SOC) estimation, nonlinear observer, leakage current

CLC Number:

TP13
TK 01+8

DU Yushi, JU Changjiang, YANG Genke. Online Estimation of Supercapacitor State of Charge Based on Nonlinear Observer[J]. Journal of Shanghai Jiao Tong University, 2022, 56(12): 1630-1637.

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模型类别	R₀/Ω	R₂/Ω	R_l/Ω	C₀/F	k/ (F·V^-1)	C₂/F
单一模型	0.000 63	0.5	3 000	28 000	350	500
充电模型	0.001 5	0.000 05	3 000	28 000	440	2 000
放电模型	0.000 53	0.8	3 000	28 000	400	0.1

模型类别	ME	MAE	RMSE
单一模型	2.493	0.748	1.065
充电模型	0.184	0.107	0.122

模型类别	ME	MAE	RMSE
不考虑泄漏	7.776	3.653	4.290
考虑泄漏	0.184	0.108	0.123

模型类别	ME	MAE	RMSE
单一模型	2.087	0.731	0.962
放电模型	0.303	0.190	0.214

模型类别	ME	MAE	RMSE
不考虑泄漏	3.744	2.097	2.365
考虑泄漏	0.303	0.195	0.217