Study On The Fault Diagnosis And Fault Tolerant Strategy Of Ni-MH Battery

Electric cars have become the future development direction of cars. However, asone of the key technologies, power batteries have two important problems such as lowsafety coefficient and poor reliability that have been restricting the electric cars’development and the formation of industrialization. It is worth mentioning that autofault diagnosis technology development as a new subject and fault-tolerant controltechnology is widely used in automotive field. Therefore, it provides a new method forsolving those problems. In this thesis, the Ni-MH battery that was widely used in theelectric cars and hybrid cars was selected as the main research object, and a study aboutfault diagnosis and fault-tolerant strategy was carried out.First, in this thesis, the working principle and performance parameters of Ni-MHbattery were analyzed and their potential faults were studied. Second, based on theresistance and capacitance model of Ni-MH battery, the Ni-MH battery model as well ascapacitance reduced fault model and resistance increased fault model were establishedby using ADVISOR and its secondary development technique. And then the simulationanalysis was carried out about the Ni-MH battery’s current, voltage, state of charge,temperature and power loss.Third, based on wavelet transform and wavelet packet analysis technology, theNi-MH battery’s fault value was extracted. Based on the BP and Elman neural network,the fault diagnosis systems were established and the performance simulation andcontrast analysis were executed. Through the simulation it draws a conclusion that bothBP and Elman neural network fault diagnosis systems can detect the Ni-MH battery’sfaults, and the former’s performance is better than the latter.Finally, a kind of fault-tolerant control strategy was brought up in this thesis, whichwas separating the battery monomer destroyed. The simulation results show that whenone or more battery monomers are damaged, they don’t affect overall work performanceof the Ni-MH battery packs after the fault-tolerant, and the batteries can still drive theelectric car.The developed fault diagnosis system and proposed fault-tolerant control strategyfor the Ni-MH battery in this thesis lay a foundation for the reliability research ofNi-MH battery, and offer a new idea to the fault diagnosis and fault-tolerant researchesfor other power batteries.