Method of estimating pulse response using an impedance spectrum

摘要

Electrochemical Impedance Spectrum data are used to predict pulse performance of an energy storage device. The impedance spectrum may be obtained in-situ. A simulation waveform includes a pulse wave with a period greater than or equal to the lowest frequency used in the impedance measurement. Fourier series coefficients of the pulse train can be obtained. The number of harmonic constituents in the Fourier series are selected so as to appropriately resolve the response, but the maximum frequency should be less than or equal to the highest frequency used in the impedance measurement. Using a current pulse as an example, the Fourier coefficients of the pulse are multiplied by the impedance spectrum at corresponding frequencies to obtain Fourier coefficients of the voltage response to the desired pulse. The Fourier coefficients of the response are then summed and reassembled to obtain the overall time domain estimate of the voltage using the Fourier series analysis.

主权项

1. A method of assessing a condition of an energy storage device by estimating a response to an excitation pulse, the method comprising the acts of:
defining a simulated pulse profile comprising a periodic train of pulses to emulate the excitation pulse; decomposing the simulated pulse profile by Fourier analysis to obtain Fourier series coefficients at Fourier series frequencies, the Fourier series frequencies comprising a low frequency at the frequency of the periodic train of pulses, a largest selected harmonic frequency and harmonic frequencies therebetween; measuring an impedance spectrum comprising measured responses of the energy storage device to a stimulus at a plurality of frequencies, wherein one or more frequencies of the plurality of frequencies is different from the Fourier series frequencies; estimating values for the impedance spectrum at one or more of the Fourier series frequencies when the impedance spectrum does not include a value at the one or more of the Fourier series frequencies; for each of the Fourier series frequencies, combining the Fourier series coefficients with either a measured value or an estimated value of the impedance spectrum at a corresponding frequency to obtain an estimated response at that corresponding frequency; assembling the estimated responses for each of the Fourier series frequencies into an overall time response of the energy storage device; and subtracting the overall time response from a bias voltage of the energy storage device to estimate the response of the energy storage device to the excitation pulse.