A real-time correction method for energy storage and vehicle battery SOC

Abstract

The present invention belongs to the technical field of battery management system for new energy vehicles, and is a method for correcting the internal resistance of a battery of an energy storage and vehicle-mounted battery charging SOC. The method comprises pre-acquiring a charging current curve of a target battery under constant current charging conditions at different temperatures, and pre-acquiring the internal resistance of the target battery at different temperatures; determining the real-time battery temperature and current value according to the charging current curve, and determining different calibration points and the reference voltage of the calibration points based on the battery temperature, current value and internal resistance; adjusting the SOC growth rate according to the acquired maximum single cell voltage of the target battery and the reference voltage of different calibration points, and a pre-set correction method, so as to realize real-time correction of the SOC; the correction method proposed by the present invention estimates the reference point voltage according to the temperature, current and internal resistance and compares it with the actual SOC, and reversely corrects the BMS calculated SOC by calculating the actual voltage, thereby effectively avoiding the problem of the SOC being kept at 99% for a long time due to a false high, the problem of discharge breakdown, and the problem of the SOC being jumped at the end of charging due to a false low.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery management systems for new energy vehicles, and in particular relates to a method for real-time correction of energy storage and vehicle-mounted battery SOC. Background Art

[0002] As one of the core components of electric vehicles, the Battery Management System (BMS) has always been the focus of electric vehicle research and development. With the development of electric vehicle intelligence, the accuracy of the SOC of electric vehicles is very critical to the whole vehicle. If the SOC calculation is inaccurate, the SOC of the whole vehicle may be artificially high and the vehicle may break down.

[0003] However, there are often the following problems in calculating SOC in the prior art:

[0004] 1. Currently, some charging piles on the market have restrictions, and the SOC can only be charged to 95% at most, which makes it impossible to trigger the full charge correction of the whole vehicle, and it is impossible to eliminate the ampere-hour integration error through the full charge correction.

[0005] 2. Some commercial vehicles powered by lithium iron phosphate are driven for a long time at 30% to 80% of the vehicle's operating voltage. The voltage characteristics of lithium iron phosphate have no obvious characteristics between 30% and 80%, resulting in fewer opportunities for triggering calibration.

[0006] 3. The SOC is too high, resulting in a charging current that is too small, causing the battery to remain at 99% for too long before being fully charged. The driver has to wait too long when charging and has a clear sense of rejection. Summary of the invention

[0007] The purpose of the present invention is to provide a real-time correction method for energy storage and vehicle battery SOC to solve the problems raised in the background technology.

[0008] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0009] A method for real-time correction of energy storage and vehicle battery SOC, comprising:

[0010] Pre-acquire the charging current curve of the target battery under constant current charging conditions at different temperatures, and pre-acquire the internal resistance of the target battery under different temperatures;

[0011] Determine the real-time battery temperature and current value according to the charging current curve, and determine different calibration points and reference voltages of the calibration points based on the battery temperature, the current value and the internal resistance;

[0012] The SOC growth rate is adjusted according to the obtained maximum single cell voltage of the target battery and the reference voltages at different calibration points, as well as a pre-set correction method, so as to achieve real-time correction of the SOC.

[0013] As a further optimization solution of the present invention, the charging current curve is obtained in the following manner:

[0014] The target battery was left standing at room temperature for more than 1 hour, discharged at a constant current of 0.3C to reach the full discharge voltage of the battery, left standing for more than 1 hour, the temperature was adjusted to T1℃, the battery cell was cooled to T1℃, left standing for more than 1 hour, charged at a constant current of I1 to the full charge voltage, left standing for more than 1 hour, and after full discharge and full charge cycles, the "Temperature-SOC-Current I1 Constant Charging Voltage" curve at different temperatures was obtained.

[0015] As a further optimization scheme of the present invention, the internal resistance of the target battery is determined by a "temperature-SOC-battery internal resistance R" curve table at different temperatures, and the "temperature-SOC-battery internal resistance R" curve table is obtained by a DC pulse test.

[0016] As a further optimization solution of the present invention, the determining different calibration points and the reference voltage of the calibration points based on the battery temperature, the current value and the internal resistance includes:

[0017] The BMS collects the target battery's single cell temperature T1 and the corresponding battery pack current value I2 during the middle charging period, determines the calibration point D2 according to the "Temperature-SOC-Current I1 Constant Charging Voltage" curve table, and obtains the reference voltage V7, BMS system time t1, and battery capacity Q1 corresponding to the calibration point D2:

[0018] V7=V6+R1*(I2-I1)

[0019] Among them, V6 is the constant current charging voltage value corresponding to the cell temperature T1, R1 is the battery internal resistance corresponding to the cell temperature T1, and I1 is the constant current charging current value;

[0020] The BMS collects the lowest single cell temperature T2 of the target battery and the corresponding battery pack current value I4, determines the calibration point D3 according to the "Temperature-SOC-Current I1 Constant Charging Voltage" curve table, and obtains the reference voltage V9 and BMS system time t2 corresponding to the calibration point D3:

[0021] V9=V8+R2*(I4-I1)

[0022] Among them, V8 is the constant current charging voltage value corresponding to the lowest cell temperature T2, R2 is the battery internal resistance corresponding to the lowest cell temperature T2, and I1 is the constant current charging current value.

[0023] As a further optimization scheme of the present invention, the BMS obtains the highest single cell voltage V5 of the target battery in advance, and the preset correction method includes:

[0024] When V5>reference voltage V7 corresponding to calibration point D2 and SOC1 calculated by BMS at calibration point D2<SOC2 at calibration point D2, the corrected SOC1 is:

[0025]

[0026] When the highest cell voltage V5 < the reference point V9 corresponding to the calibration point D3 and the SOC3 calculated by the BMS at the calibration point D3 < the SOC4 at the calibration point D3, the corrected SOC3 is:

[0027]

[0028] Wherein, t0 is the last BMS system time, f1 and f2 are acceleration coefficients, f1>1, f2<1.

[0029] The beneficial effects of the present invention are:

[0030] The correction method proposed in the present invention estimates the reference point voltage according to the temperature, current and internal resistance and compares it with the actual SOC, and reversely corrects the BMS calculated SOC by calculating the actual voltage, thereby effectively avoiding the problem of the SOC being too high to be maintained at 99% for a long time, the problem of discharge being stranded, and the problem of the SOC being too low to jump at the end of charging. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flow chart of the correction method of the present invention;

[0032] Figure 2 It is a system framework diagram of the correction method of the present invention. DETAILED DESCRIPTION

[0033] The present application is further described in detail below in conjunction with the accompanying drawings. It is necessary to point out here that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technical personnel in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0034] Example 1

[0035] like Figure 1-2 As shown, this embodiment provides a method for real-time correction of energy storage and vehicle battery SOC, including:

[0036] Pre-acquire the charging current curve of the target battery under constant current charging conditions at different temperatures, and pre-acquire the internal resistance of the target battery under different temperatures;

[0037] Determine the real-time battery temperature and current value according to the charging current curve, and determine different calibration points and reference voltages of the calibration points based on the battery temperature, the current value and the internal resistance;

[0038] The SOC growth rate is adjusted according to the obtained maximum single cell voltage of the target battery and the reference voltages at different calibration points, as well as a pre-set correction method, so as to achieve real-time correction of the SOC.

[0039] Furthermore, the charging current curve is obtained as follows:

[0040] The target battery was left standing at room temperature for more than 1 hour, discharged at a constant current of 0.3C to reach the full discharge voltage of the battery, left standing for more than 1 hour, the temperature was adjusted to T1℃, the battery cell was cooled to T1℃, left standing for more than 1 hour, charged at a constant current of I1 to the full charge voltage, left standing for more than 1 hour, and after full discharge and full charge cycles, the "Temperature-SOC-Current I1 Constant Charging Voltage" curve at different temperatures was obtained.

[0041] Furthermore, the internal resistance of the target battery is determined by a "temperature-SOC-battery internal resistance R" curve table at different temperatures, and the "temperature-SOC-battery internal resistance R" curve table is obtained by a DC pulse test.

[0042] More specifically, the "Temperature-SOC-Battery Internal Resistance R" curve obtained by DC pulse testing is as follows:

[0043] a. Adjust the incubator temperature to room temperature and let it stand for more than 1 hour.

[0044] b. Charge the battery at a constant current of 0.3C to reach the full charge voltage of the battery, adjust the current to 0.1C to reach the full charge voltage again, and let it stand for more than 1 hour.

[0045] c. Adjust the temperature of the incubator to T1℃, wait for the battery cell to cool to T1℃, and let it stand for more than 1 hour.

[0046] d. Discharge at a constant current of 0.3C to SOC1, let stand for more than 1 hour, and record the cell voltage as V1.

[0047] e. Discharge at a constant current of I1 for 60 seconds, record the cell voltage as V2, let stand for more than 1 hour, and record the cell voltage as V3;

[0048] f. Charge at constant current I1 for 60 seconds, record the cell voltage as V4, and let stand for more than 1 hour;

[0049] g. Discharge internal resistance R = (V1-V2) / I1

[0050] h. Charging internal resistance R = (V4-V3) / I1

[0051] i. Cycle steps a, b, c, d, test the "Temperature-SOC-Battery Internal Resistance R" curve at different temperatures.

[0052] Further, the determining different calibration points and the reference voltages of the calibration points based on the battery temperature, the current value and the internal resistance includes:

[0053] The BMS collects the target battery's single cell temperature T1 and the corresponding battery pack current value I2 during the middle charging period, determines the calibration point D2 according to the "Temperature-SOC-Current I1 Constant Charging Voltage" curve table, and obtains the reference voltage V7, BMS system time t1, and battery capacity Q1 corresponding to the calibration point D2:

[0054] V7=V6+R1(I2-I1)

[0055] Among them, V6 is the constant current charging voltage value corresponding to the cell temperature T1, R1 is the battery internal resistance corresponding to the cell temperature T1, and I1 is the constant current charging current value;

[0056] The BMS collects the lowest single cell temperature T2 of the target battery and the corresponding battery pack current value I4, determines the calibration point D3 according to the "Temperature-SOC-Current I1 Constant Charging Voltage" curve table, and obtains the reference voltage V9 and BMS system time t2 corresponding to the calibration point D3:

[0057] V9=V8+R2(I4-I1)

[0058] Among them, V8 is the constant current charging voltage value corresponding to the lowest cell temperature T2, R2 is the battery internal resistance corresponding to the lowest cell temperature T2, and I1 is the constant current charging current value.

[0059] Furthermore, the BMS obtains the highest single cell voltage V5 of the target battery in advance, and the preset correction method includes:

[0060] When V5>reference voltage V7 corresponding to calibration point D2 and SOC1 calculated by BMS at calibration point D2<SOC2 at calibration point D2, the corrected SOC1 is:

[0061]

[0062] When the highest cell voltage V5 < the reference point V9 corresponding to the calibration point D3 and the SOC3 calculated by the BMS at the calibration point D3 < the SOC4 at the calibration point D3, the corrected SOC3 is:

[0063]

[0064] Wherein, t0 is the last BMS system time, f1 and f2 are acceleration coefficients, f1>1, f2<1.

[0065] In this embodiment, the specific values ​​of the acceleration coefficients f1 and f2 are calibrated according to the required SOC change rate of the whole vehicle.

[0066] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A real-time correction method for energy storage and vehicle battery SOC, characterized in that: include: Pre-acquire the charging current curve of the target battery under constant current charging conditions at different temperatures, and pre-acquire the internal resistance of the target battery under different temperatures; Determine the real-time battery temperature and current value according to the charging current curve, and determine different calibration points and reference voltages of the calibration points based on the battery temperature, the current value and the internal resistance; The SOC growth rate is adjusted according to the obtained maximum single cell voltage of the target battery and the reference voltages at different calibration points, as well as a pre-set correction method, so as to achieve real-time correction of the SOC; The determining of different calibration points and reference voltages of the calibration points based on the battery temperature, the current value and the internal resistance comprises: The BMS collects the target battery's single cell temperature T1 and the corresponding battery pack current value I2 during the middle charging period, determines the calibration point D2 based on the temperature-SOC-current I1 constant charging voltage curve table, and obtains the reference voltage V7 corresponding to the calibration point D2, the BMS system time t1, and the battery capacity Q1: V7=V6+R1(I2-I1) Among them, V6 is the constant current charging voltage value corresponding to the cell temperature T1, R1 is the battery internal resistance corresponding to the cell temperature T1, and I1 is the constant current charging current value; The BMS collects the lowest single cell temperature T2 of the target battery and the corresponding battery pack current value I4, determines the calibration point D3 according to the temperature-SOC-current I1 constant charging voltage curve table, and obtains the reference voltage V9 and BMS system time t2 corresponding to the calibration point D3: V9=V8+R2(I4-I1) Among them, V8 is the constant current charging voltage value corresponding to the lowest cell temperature T2, R2 is the battery internal resistance corresponding to the lowest cell temperature T2, and I1 is the constant current charging current value; The BMS obtains the highest single cell voltage V5 of the target battery in advance, and the preset correction method includes: When V5>reference voltage V7 corresponding to calibration point D2 and SOC1 calculated by BMS at calibration point D2<SOC2 at calibration point D2, the corrected SOC1 is: When the highest cell voltage V5 < the reference point V9 corresponding to the calibration point D3 and the SOC3 calculated by the BMS at the calibration point D3 < the SOC4 at the calibration point D3, the corrected SOC3 is: Wherein, t0 is the last BMS system time, f1 and f2 are acceleration and deceleration coefficients, f1>1, f2<1.

2. A method for real-time correction of energy storage and vehicle battery SOC according to claim 1, characterized in that: The charging current curve is obtained as follows: The target battery was left standing for more than 1 hour at room temperature, discharged at a constant current of 0.3C to reach the full discharge voltage of the battery, left standing for more than 1 hour, the temperature was adjusted to T1℃, the battery cell was cooled to T1℃, left standing for more than 1 hour, charged at a constant current of I1 to the full charge voltage, left standing for more than 1 hour, and after full discharge and full charge cycles, the temperature-SOC-current I1 constant charging voltage curve at different temperatures was obtained.

3. A method for real-time correction of energy storage and vehicle battery SOC according to claim 1, characterized in that: The internal resistance of the target battery is determined by a temperature-SOC-battery internal resistance R curve table at different temperatures, and the temperature-SOC-battery internal resistance R curve table is obtained by a DC pulse test.

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