An Iterative Algorithm of Linear Least Squares to Identify Online the Capacity of Supercapacitor

It is known that supercapacitors exhibits a voltage-dependent capacitance and the capacitance varies approximately linearly with voltage in the normal operation voltage range. To solve the online supercapacitor capacity identification problem, which is an important function to implement in supercapacitor management system, firstly, linear least squares (LLS) is applied to get a closed-form solution based on a sequence of sampling terminal voltage and charging current data, and in the meanwhile, the details of voltage data processing to obtain more accurate differential capacitance values are elaborated. Secondly, to overcome the difficulty that the closed-form solution involves large data set, takes calculation of matrix inverse, and hence leads to heavy computing burden, an iterative algorithm of LLS is deduced, which gets rid of calculating matrix inverse directly, decomposes the computing burden of LLS into each sampling period, and therefore makes itself more applicable in online identification situations. Lastly, the effectiveness of the algorithm is verified by experiment.

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