2025, 52(2):1-9.
Abstract:To investigate the error convergence characteristics of power battery polarization parameter estimation under different operating conditions, the stability and convergence of the estimators are rigorously analyzed in this paper by using Lyapunov’s second method. The state equations of polarized parameter estimation errors are firstly derived based on the equivalent circuit model and the forgetting factor recursive least squares (FFRLS). Subsequently, the state equation is analyzed using Lyapunov’s second method to obtain the necessary condition for the asymptotic convergence of the estimator, i.e., continuously varying current input. A graphical method is proposed for analyzing the dynamic convergence properties of the error and justifying this necessary condition. Finally, the theoretical analysis process and results are validated using data generated from an experimentally calibrated battery model. The results show that the estimator can gradually converge to the vicinity of the true value under continuously varying current inputs, and the drastically varying positive and negative alternating conditions have better convergence properties.
2024, 51(12):57-66.
Abstract:To meet the requirements of SOC estimation accuracy and robustness, a temperature-dependent second-order RC equivalent circuit model is established, taking a lithium-ion battery cell as the study object and considering the effects of temperature change on open-circuit voltage, polarization resistance, polarization capacitance, and capacity. Simulation results show that the model has higher accuracy than the second-order RC model. Based on this model, the extended Kalman filter algorithm with multiple suboptimal fading factor is used to estimate SOC. The results show that the root mean square error of SOC estimation of the SMFEKF algorithm based on the variable temperature model and the constant temperature model is reduced by 42.7% and 48.2%, respectively, compared with the EKF algorithm under variable temperature conditions, which can ensure strong robustness of estimation results. The maximum relative error and root mean square error of SOC estimation results based on the variable temperature model are smaller than those of the constant temperature model under the DST condition in the variable temperature environment, which proves that the model has strong temperature adaptability and can have higher estimation accuracy under the variable temperature condition.
2021, 48(10):187-200.
Abstract:The state of charge (SOC), state of health (SOH) and residual mission (RUL) of lithium-ion battery are important state parameters for the safe and stable operation of lithium-ion battery. In this paper, a coupled estimation method of lithium-ion battery state based on the rising segment of charging voltage is proposed to realize the coupled estimation of SOC, SOH and RUL in a long operation cycle from the starting point of battery prediction (SP) to the end of life (EOL). The framework estimates SOH and RUL in the charging phase and SOC in the discharge phase. Firstly, the rising time of constant current charging voltage curve segment is extracted as the health feature (HF), and the HF as the input and cycle capacity as the output are used to establish the least squares support vector machine (LSSVM) battery aging model for SOH estimation; The equivalent circuit model is used for nonlinear fitting of the voltage segment, and the state space model is established with the fitting parameters, which is combined with the unscented Kalman filter algorithm to estimate SOC; Gaussian process regression time series model is used to model the health feature series, and the change trend of HF is predicted by extrapolation of cycle times,which is combined with LSSVM model to predict RUL and the corresponding confidence interval. The experimental results show that the proposed method has high estimation accuracy and good stability.
1990, 17(1).
Abstract:Testing and analysing the small current characteristics of three kinds of home-made ZnO elements under voltages with different waves, we present a new equivalent circuit for ZnO element. Some proposals for designing and testing MOA used in H.V.D.C. conver
1988, 15(2).
Abstract:In this paper,an equivalent circuit is proposed for T mutual inductance network.This circuit is used to get rid of the coupling in networks including T mutual inductance so that the circuit calculations are greatly simpli-fied.Applying this metheod to