A hybrid vehicle lfp battery soc calibration method and a whole vehicle energy coordination management method

Abstract

The present application relates to the technical field of lithium ion batteries, in particular to a hybrid vehicle LFP battery SOC calibration method and a whole vehicle energy coordination management method. The SOC calibration method comprises the following steps: S0, determining a calibration current limit I c of a charging process and a calibration current limit I d of a discharging process based on hybrid working condition data; S1, determining a calibration rate C c_d of the discharging process and a calibration rate C c_c of the charging process; S2, determining a charging and discharging calibration trigger duration t c ; S3, extracting a charging calibration voltage matrix and a discharging calibration voltage matrix based on cell test data; and S4, determining a dynamic calibration strategy. The whole vehicle energy coordination management method comprises a charging and discharging MAP adjustment strategy, a battery fault processing strategy and a whole vehicle energy coordination strategy. The present application customizes a special SOC calibration strategy for the hybrid agricultural machine working condition, adopts ampere-hour integration combined with multi-interval dynamic calibration, and can effectively eliminate error accumulation.

Claims

1. A method for calibrating the state of charge (SOC) of an LFP battery in a hybrid vehicle, characterized in that, Includes the following steps: S0. Determine the calibration current limit I for the charging process based on hybrid operating condition data. c and the calibration current limit I during the discharge process d Specifically: Extract all charging currents from the operating condition data, calculate the probability distribution of different current ranges, and select the current value with a cumulative probability close to 80% as the calibration current limit I. c ; Extract all discharge currents from the operating condition data, calculate the probability distribution of different current ranges, and select the current value with a cumulative probability close to 80% as the calibration current limit I. d ; S1. Determine the calibration rate C for the discharge process based on hybrid operating condition data. c_d And the calibration rate C during the charging process c_c , where C c_c equals I c C c_d To satisfy 0~I d The average value of the discharge current; S2. Determine the charge / discharge calibration trigger duration t based on hybrid operating condition data. c ; S3. Extract the charging calibration voltage matrix and discharging calibration voltage matrix based on the cell test data, specifically including the following: S301. Based on the charge and discharge SOC-CCV curve of LFP battery, select a relatively obvious linear range. At the end of charging, select 95%-100% SOC as the calibration range, and at the end of discharging, select 0-X% SOC as the calibration range, with X ranging from 20 to 25. S302, Extract the battery cell within a temperature range of -30℃ to 55℃, C c_c At the charging rate, the voltage values ​​corresponding to several SOCs within the calibration range are used as the charging calibration voltage matrix. S303, Extract the battery cell within a temperature range of -30℃ to 55℃, C c_d At the discharge rate, the voltage values ​​corresponding to several SOCs within the calibration range are used as the discharge calibration voltage matrix. S4. Determine the dynamic calibration strategy: Feedback calibration: when current I ≤ I c Duration reaches t c And V max When falling into the charging calibration voltage matrix, the corresponding SOC is obtained through the charging calibration voltage matrix and the real SOC is calibrated to the target value. The displayed SOC follows the real SOC with a 40x integral and the reverse following factor is 1 / 40. Discharge calibration: when current I ≤ I d Duration reaches t c And V min When falling into the discharge calibration voltage matrix, the corresponding SOC is obtained through the discharge calibration voltage matrix and the real SOC is calibrated to the target value. The displayed SOC follows the real SOC by a 40-fold integral and the reverse following factor is 1 / 40. 100% SOC calibration: When current I ≤ first current threshold and duration reaches t c Furthermore, when the battery pack voltage reaches the charging cutoff voltage, both the actual SOC and the displayed SOC are simultaneously calibrated to 100%; where the first current threshold is the continuous charging rate corresponding to the first intermediate charging calibration point preset in the continuous charging MAP. 0% SOC calibration: When current I ≤ second current threshold and duration reaches t c Furthermore, when the battery pack voltage reaches the discharge cutoff voltage, both the actual SOC and the displayed SOC are simultaneously calibrated to 0%; where the second current threshold is the continuous discharge rate corresponding to the first intermediate discharge calibration point preset in the continuous discharge MAP; The first current threshold is the continuous charging rate corresponding to 95% SOC in the continuous charging MAP, and the second current threshold is the continuous discharging rate corresponding to 25% SOC in the continuous discharging MAP.

2. The hybrid vehicle LFP battery SOC calibration method as described in claim 1, characterized in that, Step S2 specifically includes the following: S201, Extracting values ​​satisfying 0~I d Calculate the duration of the current for each discharge, considering all discharge currents. S202, Extracting values ​​satisfying 0~I c Calculate the duration of the current for each charging cycle, considering all charging currents. S203. Based on the duration distribution data of charging and discharging, determine the charge / discharge calibration trigger duration t. c , t c The determination principle is as follows: the calibration trigger frequency for charging and discharging is between 2 and 10 times. If multiple t c If both conditions are met, choose the larger one.

3. The method for calibrating the SOC of an LFP battery in a hybrid vehicle as described in claim 1, characterized in that, The specific steps S3 are as follows Includes the following: S301. The calibration range is 95%-100% SOC at the end of charging and 0-25% SOC at the end of discharging. S302, Extract the battery cell within a temperature range of -30℃ to 55℃, C c_c The voltage values ​​corresponding to 95% SOC, 97% SOC, and 100% SOC at the charging rate are used as the charging calibration voltage matrix; S303, Extract the battery cell within a temperature range of -30℃ to 55℃, C c_d The voltage values ​​at 25% SOC, 20% SOC, 15% SOC, 10% SOC, 5% SOC, and 0% SOC at the discharge rate are used as the discharge calibration voltage matrix.

4. A method for coordinated energy management of a hybrid vehicle based on the SOC calibration method of claim 1, characterized in that, Includes the following: Charge / discharge MAP adjustment strategy: Determine the first SOC (State of Charge) in the charging MAP. C1 and the first discharge calibration point (SOC) in the discharge MAP D1 The SOC C1 95% SOC, SOC D1 25% SOC; The corresponding SOC in the charging MAP C1 The charging power is limited to a first charging power value, which is not less than the minimum charging power required to avoid significant vehicle vibration when the vehicle energy management switches from charging to discharging the battery pack. The corresponding SOC in the discharge MAP D1 The discharge power is limited to a first discharge power value, which is not less than the minimum discharge power required to avoid significant vehicle vibration when the vehicle energy management switches from discharging to charging the battery pack. The corresponding second charging calibration point SOC in the charging MAP C2 The continuous charging power is limited to 0, and the SOC is... C2 97% or 98% SOC; The corresponding second discharge calibration point SOC in the discharge MAP D2 The continuous discharge power is limited to 0, and the SOC is... D2 15% SOC; Battery failure handling strategy: When an individual cell voltage overcharge alarm is triggered, the feedback power is limited to 0, and the actual SOC and displayed SOC are forcibly calibrated to 100%. When an over-discharge alarm is triggered on a single cell, the discharge power is limited to 0, and both the actual SOC and the displayed SOC are forcibly calibrated to 0%. Whole vehicle energy synergy strategy: Obtain the current state of charge (SOC) of the battery pack; When the state of charge (SOC) is below 25%, increase the generator's output power. When the state of charge (SOC) is higher than 95%, reduce the generator's output power.

5. The vehicle energy collaborative management method as described in claim 4, characterized in that, The triggering condition for the single-cell overcharge alarm is: the battery voltage reaches the cutoff voltage for normal charging, and the duration is ≥3s. The triggering condition for the single-cell over-discharge alarm is: the battery voltage reaches the cutoff voltage for normal discharging, and the duration is ≥3s.

6. The vehicle energy collaborative management method as described in claim 4, characterized in that: The vehicle energy synergy strategy also includes controlling the battery pack's SOC within a preset convergence range: When the SOC is lower than the lower threshold of the convergence range, the generator is controlled to adjust its output power to replenish the battery pack until the SOC rises back to the convergence range. When the SOC is higher than the upper threshold of the convergence interval, the generator is controlled to adjust the output power to discharge the battery pack until the SOC drops to within the convergence interval. When the SOC is within the convergence range, the current generator output power is maintained, and no additional power is supplied or discharged to the battery pack.

7. The vehicle energy collaborative management method as described in claim 6, characterized in that: The lower threshold of the convergence interval is 60% SOC, and the upper threshold is 70% SOC.

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