Research On Super-capacitor State Of Charge Calculation Method

No matter the super-capacitor used in electric power system,electric vehicles, hybrid vehicles, electric or electronic products, state of charge(SOC) is a important parameter in energy control.In this paper, the SOC calculation methods used in traditional eletrical storage were studied, advantages and disadvantages of various methods were analyzed. According to the difference between traditonal batteries and super-capacitors, the battery SOC algorithms were improved, at the same time, the methods of A-H and load voltage were disigned. Through the charge,discharge and self-discharge test, the characteristics of the super-capacitors were analyzed. Based on the physical properties of the super-capacitor, the nonlinear first-order which considered the voltage impact to equivalent capacitance value and self-discharge effect. Meanwhile, methods about model parameters identification were given, which were improved with higher accuracy by simulation. Based on the new model and Kalman filtering theory, the author proposed a new Kalman filter algorithm which used current integration and terminal valtage.Combined LabVIEW and MATLAB, the SOC of super-capacitor was calculated with the online real-time measurement system which used the A-H method, the load voltage method and Kalman filtering method. Results showed the accuracy of super-capacitor SOC calculating which used Kalman filter algorithm was higher, and also verifyed the Kalman filer of the prosposed algorithm for super-capaciror SOC calculating. In additon, the online real-time measurement system has higher availability.