Battery monomer fault detection method and device of energy storage system

The invention discloses a single battery fault detection method and device for an energy storage system, and the method comprises the steps: obtaining the thermal runaway data of each single battery in the energy storage system under an operation condition, and obtaining the full-life-cycle data; performing cleaning state preprocessing on the full life cycle data to obtain a plurality of charging and discharging fragment data; on the basis of a pre-constructed successive variation mode model, successive variation mode decomposition is carried out by adjusting model parameters, and maximum voltage dynamic fluctuation components and voltage dynamic fluctuation components are obtained; based on a selected outlier threshold value, box plot local outlier detection is carried out on each maximum voltage dynamic fluctuation component, and an abnormal single battery detection result is obtained; and performing battery internal fault diagnosis on each voltage dynamic fluctuation component according to the selected fir