Method for extracting characteristic parameters of the state of health of lithium iron phosphate batteries for battery cascade utilization
A technology of lithium iron phosphate batteries and characteristic parameters, which is applied in the direction of measuring electricity, measuring electrical variables, measuring devices, etc., can solve the problems of large errors in related parameters, and achieve the effects of reducing errors, speeding up and improving accuracy.
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specific Embodiment approach 1
[0027] Specific implementation mode 1. Combination figure 1 , figure 2 and image 3 Describe this embodiment, the method for extracting the health state characteristic parameters of lithium iron phosphate batteries for battery cascade utilization described in this embodiment, the specific steps of the method are:
[0028] Step 1. Use a current signal with a current value of C / 25 to charge the battery whose characteristic parameters are to be extracted, and collect the terminal voltage U of the battery T (k); Set up the simple equivalent circuit model of battery charging; C is the rated current of battery to be tested;
[0029] Step 2. Using the model parameters of the battery charging equivalent circuit model in step 1, establish a relational expression:
[0030]
[0031] get model terminal voltage Among them, SOC p,1 It is the termination SOC value of the lithium iron phosphate positive electrode lithium intercalation process or the initial SOC value at the beginnin...
specific Embodiment approach 2
[0044] Specific embodiment 2. This embodiment is a further description of the method for extracting the health state characteristic parameters of the lithium iron phosphate battery for battery cascade utilization described in the specific embodiment 1. In step 2, the open circuit potential function U of the lithium iron phosphate positive electrode is p (SOC p )for:
[0045] u p (SOC p )=3.4323-0.8428exp(-80.2493(1-SOC p ) 1.3198 )
[0046] -3.2474×10 -6 exp(20.2645(1-SOC p ) 3.8003 ) (5)
[0047] +3.2482×10 -6 exp(20.2646(1-SOC p ) 3.7995 )
[0048] Graphite negative electrode open circuit potential function U n (SOC n )for:
[0049]
[0050] The constant coefficients of the equation of positive and negative open circuit potentials are obtained by curve fitting, SOC n The SOC value during the charging process of the graphite negative electrode of the battery, SOC p The SOC value of the lithium iron phosphate positive electrode when charging the battery.
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specific Embodiment approach 3
[0052] Specific Embodiment 3. This embodiment is a further explanation of the method for extracting the health state characteristic parameters of lithium iron phosphate batteries for cascaded utilization of batteries described in Embodiment 1, using the Levenberg-Marquardt method for iterative calculation The process of realizing model parameter identification is as follows:
[0053] Use the formula:
[0054]
[0055] Among them, the Jacobi matrix is: The Hessian matrix is: The terminal voltage sensitivity matrix is: λ is the iteration step, i is the number of iterations, I is the identity matrix, , ε is the iteration threshold, let θ i =θ=[SOC n,1 ,m,R], that is, to obtain the parameter SOC to be identified n,1 , m and R.
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