超级电容器具有快速充放、高功率密度和长寿命等优点, 被广泛用于新能源汽车的储能系统. 系统可靠运行需获取其剩余电量, 即对其荷电状态(SOC)进行估算. 依托超级电容单体的等效模拟电路模型, 建立了以模型中多电容端电压为状态, 电容器输入电流为控制输入, 电容器输出电压为观测输出的电容器二阶非线性系统的状态空间模型, 包含了自放电现象产生的泄漏电流的因素. 为提高模拟精度, 辨识不同的模型参数,分别刻画充电和放电工况. 采用非线性观测器算法来获取模型内部状态从而实现对SOC的估计. 充放电实验的结果表明, 考虑泄漏因素和建立不同参数下的充放电模型, 能够更好地模拟超级电容器的动态特性, 同时验证了非线性观测器算法具有稳定的跟踪能力.

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.