Study Of Rapid AC Impedance Test And Its Application In Electric Vehicles

In face of the current fossil energy crisis and global environmental pollution,the rapid advancement of electric vehicles can alleviate or partly solve the above serious problems.As one of the most critical technologies in electric vehicles,battery management system is of vital importance for the safe,efficient and stable operation of on-board batteries,and accurate state estimation is the prerequisite for achieving efficient battery management.Traditional strategies for battery state estimation mostly depend on the external characteristics,which can not reflect the fundamental properties.Hence,the accuracy of state estimation is limited,which affects the safety level of battery operation.Electrochemical impedance spectroscopy(EIS)is regarded as a powerful tool for investigating the physical and chemical characteristics of electrochemical systems.The fundamental properties of batteries can be explored through the interpretation of EIS.EIS-based state monitoring for batteries shows potential prospects.Due to the disadvange such as slow testing and high cost of the traditional impedance technology,it is not suitable for real-time monitoring of battery state.Thereforce,it is urgent to develop fast testing technology for EIS.Fast impedance measurement technology mainly involves innovative broadband excitation signal and advanced estimation algorithm.With the clues of innovative excitation signals and advanced estimation algorithms,in present work,the current research status of fast impedance spectroscopy testing is firstly discussed in detail.Because it is easy to generate pseudo-random binary sequence(PRBS)and PRBS has more flat spectral characteristics than other broadband signals,PRBS has shown excellent application prospects and attracted the attention of many researchers.For above reasons,the discussion is focused on PRBS type excitation signals.In addition,wavelet transform-based fast impedance spectrum measurement is studied in depth as follows: 1)The corresponding relationship between EIS and Equivalent Circuit Model(ECM)is elucidated in detail;2)the principle of fast impedance spectroscopy measurement based on Complex Morlet Wavelet Transform(CMWT)illustrated;3)the function of complex Morlet wavelet parameters and their influence on EIS measurement are described one by one;4)based on the uncertainty principle,the influence of relevant parameters on time-frequency resolution is elaborated,and the optimization work is carried out;and 5)finally,a fast impedance spectrum measurement is implemented in higher precison and with wider frequency band.The results achieved in this paper show that it is feasible to carry out rapid EIS test.With the improvement of advanced estimation algorithm and hardware technology,fast impedance spectroscopy technology will not only play an increasingly important role in battery condition monitoring,but also be more widely used in the field of safe operation of electric vehicles.