Research On Equivalent Experiment And Diagnosis Method Of Electrothermal Characteristics Of Lithium-ion Battery Internal Short Circuit Fault

Energy shortage and environmental pollution have become the most important problems facing human industry in the 21st century.Renewable energy generation with energy storage devices has become an important solution for new power systems in the future because of its low carbon and environmental protection characteristics.lithium-ion batteries have been widely used in electrochemical energy storage devices because of their high energy density and fast charging and discharging characteristics.However,the frequent occurrence of spontaneous combustion and explosion accidents in the field of electrochemical energy storage in recent years proves that the failure of lithium-ion batteries is latent,spontaneous and destructive.The direct cause of spontaneous combustion and explosion of lithium-ion battery is thermal runaway,and the internal short circuit fault of lithium-ion battery is both the main causative and common link of thermal runaway.Therefore,in this thesis,starting from the diagnosis method of internal short circuit fault of lithium-ion battery and combining with the simulation triggering experiment of internal short circuit fault of lithium-ion battery,the safety warning method of lithium-ion battery operation is studied based on the identification of internal short circuit fault.In order to solve the problem of difficult diagnosis of internal short circuit faults in lithium-ion batteries,the internal short circuit fault simulation method is studied with Li Fe PO₄battery for energy storage as the experimental object.Combining the characteristics of lithium-ion battery internal/external short circuit faults with similar equivalent circuits,the electrothermal characteristics of lithium-ion battery during internal short circuit faults are simulated by parallel resistance from the perspective of controllable,reproducible and operable fault simulation,and the influence of internal short circuit faults on the electrothermal characteristics of lithium-ion battery is analyzed according to the parameter effect,depletion effect and adiabatic experimental results of internal short circuit faults.According to the designed experimental scheme,different materials and structures of internal short circuit fault simulation trigger elements are designed by combining the requirements of different internal short circuit simulation magnitudes on the trigger elements.On this basis,the influence of different simulated trigger element materials and structures on the temperature distribution characteristics is analyzed from the perspective of the temperature distribution characteristics of the internal short circuit fault simulation trigger experiment.According to the characteristics of internal short circuit fault in lithium-ion battery,a fault diagnosis method of internal short circuit fault in battery module based on voltage cosine similarity is proposed to construct a two-dimensional feature vector with the voltage and current signals in the battery module,introduce the gain multiplier containing the excitation information,and carry out secondary processing on the feature vector to realize the effective separation of fault signal characteristics,and the effectiveness of the diagnosis method is verified according to the experimental results.