Online impedance spectrum measurement of fuel cells based on Morlet wavelet transform
By Du, Runben; Wang, Xueyuan; Dai, Haifeng; Wei, Xuezhe; Ming, PingWen
Published in International Journal of Hydrogen Energy
2021
Abstract
An online impedance calculation method for fuel cells is proposed in this paper. A periodic square wave is selected as the standard excitation current and injected into a fuel cell. Then, the impedance spectrum is obtained by converting the excitation current and response voltage to the frequency domain with the Morlet wavelet. The accuracy of the calculated impedance is firstly tested offline under the stand excitation current condition, and the relative errors of the real part and imaginary part are within 5% and 10%, respectively. To calculate the impedance automatically, a search method is proposed to locate the position of the translation parameters autonomously. Besides, this paper investigates the effects of the stable time and the excitation current form on the calculation results and recommends the excitation current parameters. Finally, an implementation scheme for online impedance measurement is given.