A method for constructing a power battery hysteresis model based on temperature adaptation

Abstract

The present invention is a method for constructing a power battery hysteresis model based on temperature adaptation. First, the temperature is used as a variable to perform power battery OCV-SOC tests at different temperatures, and the charge and discharge open circuit voltages corresponding to different states of charge are collected; then, the average open circuit voltage of the power battery at different temperatures is calculated, the relationship between temperature and average open circuit voltage is analyzed, and a temperature-adaptive open circuit voltage sub-model is established; the relationship between temperature and hysteresis voltage is analyzed, and a temperature-adaptive hysteresis sub-model is established; finally, the open circuit voltage sub-model and the hysteresis sub-model are integrated into the equivalent circuit model to obtain a temperature-adaptive power battery hysteresis model. This method solves the problem that the hysteresis model in the prior art cannot adapt to temperature changes. The temperature-adaptive power battery hysteresis model can adapt to temperature changes within a certain range, thereby improving the model accuracy and providing a model basis for accurate SOC estimation.

Description

Technical Field

[0001] The present invention relates to the technical field of battery state of charge estimation, and in particular to a method for constructing a power battery hysteresis model based on temperature adaptation. Background Art

[0002] In order to reduce oil consumption in the automotive industry, improve the global energy structure, and reduce pollutants and greenhouse gas emissions, the electrification of automobiles has become an inevitable trend. As the power source of electric vehicles, the performance of power batteries is not only related to the length of the vehicle's driving range, but also to the safety and reliability of the battery. Compared with other types of power batteries, lithium-ion batteries have become the preferred power source for electric vehicles because of their high energy density, strong high and low temperature adaptability, high safety performance, and long cycle life. Excessive charging and discharging will cause irreversible damage to the cycle life of power batteries. Therefore, it is very necessary to use a battery management system to monitor the battery, and reliable and accurate state of charge (SOC) estimation is one of the key technologies of the battery management system.

[0003] The SOC estimation method based on the equivalent circuit model is currently widely used and studied. However, for the equivalent circuit model, its open circuit voltage has a hysteresis characteristic, which is manifested as different open circuit voltages in the charge and discharge states under the same SOC, which will seriously affect the accuracy of the terminal voltage of the equivalent circuit model, thereby reducing the accuracy of the SOC estimation. Many scholars have studied the hysteresis characteristics and established a battery hysteresis model that can optimize the open circuit voltage-state of charge (OCV-SOC) relationship. In addition, the zero-state hysteresis model and the single-state hysteresis model are two common battery hysteresis models. The former corrects the hysteresis characteristics by a constant, and the latter corrects the hysteresis characteristics by a function of the SOC variable. However, the common limitation of these two battery hysteresis models is that they do not consider the influence of temperature. Since the hysteresis behavior of the power battery will vary with temperature, if the temperature factor is not considered when establishing the battery hysteresis model, the error of the estimated value of the model will be large.

[0004] Based on the above problems, the present application proposes a hysteresis model that is adaptive to temperature changes, which can improve the accuracy of the voltage at the output end of the model and is conducive to improving the accuracy of charge state estimation. Summary of the invention

[0005] In view of the deficiencies in the prior art, the technical problem that the present invention intends to solve is to provide a method for constructing a power battery hysteresis model based on temperature adaptation; the problem that the hysteresis model in the prior art cannot adapt to temperature changes is solved; the method of the present invention can use limited temperature data so that the model can adapt to temperature changes within a certain range, thereby improving the accuracy of the model and providing a model basis for accurate estimation of SOC.

[0006] The present invention solves the technical problem by adopting the following technical solutions:

[0007] A method for constructing a power battery hysteresis model based on temperature adaptation, characterized in that the method comprises the following steps:

[0008] Step 1: Carry out capacity test at different temperatures to measure the capacity of the power battery at different temperatures;

[0009] Step 2: Perform an open circuit voltage-state of charge test at different temperatures to collect the charge and discharge open circuit voltages of the power battery at different states of charge at different temperatures;

[0010] Step 3: Let the average open circuit voltage be equal to half of the sum of the charge and discharge open circuit voltages, and calculate the average open circuit voltage of the power battery at different temperatures;

[0011] Step 4: Analyze the relationship between temperature and average open circuit voltage, and establish an open circuit voltage sub-model. The expression is:

[0012] U ou_T =Φ T ·U ou_0 (5)

[0013] Among them, Φ T Indicates the average open circuit voltage ratio at T℃, U oc_T , U oc_0 Respectively represent the average open circuit voltage of the power battery at T℃ and 0℃;

[0014] Step 5: Analyze the relationship between temperature and hysteresis voltage and establish a hysteresis sub-model. The expression is:

[0015] U h(T) =β T ·U h(0) (14)

[0016] Among them, β T Indicates the hysteresis voltage ratio at T℃, U h(T) , U h(0) Respectively represent the hysteresis voltage at T℃ and 0℃;

[0017] Step 6: Integrate the open circuit voltage sub-model and the hysteresis sub-model into the battery equivalent circuit model to obtain the temperature adaptive power battery hysteresis model. This completes the construction of the temperature adaptive power battery hysteresis model.

[0018] The establishment of the open circuit voltage sub-model includes the following steps:

[0019] Step 4.1: Set the average open circuit voltage at 0°C as the standard value, and calculate the average open circuit voltage ratio at different temperatures by formula (1);

[0020] Φ T =U oc_T / U oc_0 (1)

[0021] Step 4.2: The state of charge is divided into three intervals according to the change trend of the average open circuit voltage ratio, namely: the state of charge is 0, the state of charge interval of 10%-50% and the state of charge interval of 60%-100%. The relationship between temperature and the average open circuit voltage ratio is analyzed in the three intervals, and the temperature and average open circuit voltage ratio functions corresponding to each interval are obtained respectively:

[0022] Φ T_0 =a1T 3 +b1T 2 +c1T+d1 (2)

[0023] Φ T_10％-50％ =a2T 3 +b2T 2 +c2T+d2 (3)

[0024] Φ T_60％-100％ =a3T 3 +b3T 2 +c3T+d3 (4)

[0025] In the formula, Φ T_0 Indicates the average open circuit voltage ratio when the state of charge is 0, Φ T_10％-50％ Indicates the average open circuit voltage ratio within the range of 10%-50% state of charge, Φ T_60％-100％ Indicates the average open circuit voltage ratio in the range of 60%-100% state of charge; a1, b1, c1, d1, a2, b2, c2, d2, a3, b3, c3, d3 are all constants;

[0026] When the state of charge is 0, the average open circuit voltage ratio is calculated using formula (2); when the state of charge is in the range of 10%-50%, the average open circuit voltage ratio is calculated using formula (3); when the state of charge is in the range of 60%-100%, the average open circuit voltage ratio is calculated using formula (4).

[0027] The establishment of the hysteresis submodel includes the following steps:

[0028] Step 5.1: Calculate the hysteresis voltage of the power battery by using formula (6);

[0029] U h =ocv charge -ocv discharge (6)

[0030] In formula (6), ocv chargeis the open circuit voltage of the power battery in the charging state, ocv discharge It is the open circuit voltage of the power battery in the discharge state;

[0031] Draw hysteresis voltage curves at different temperatures, analyze the relationship between temperature and hysteresis voltage, eliminate the state of charge intervals that do not clearly reflect the correlation between temperature and hysteresis voltage, narrow the state of charge interval range to 20%-75%, and analyze the relationship between temperature and hysteresis voltage within the 20%-75% state of charge interval;

[0032] Step 5.2: Set the hysteresis voltage at 0°C as the standard value, and calculate the hysteresis voltage ratio at different temperatures using formula (7);

[0033] β T =U h(T) / U h(0) (7)

[0034] In formula (7), β T Indicates the hysteresis voltage ratio at T℃, U h(T) , U h(0) Respectively represent the hysteresis voltage at T℃ and 0℃;

[0035] Step 5.3: Divide the state of charge into two intervals according to the change trend of the hysteresis voltage ratio, namely, a 20%-50% state of charge interval and a 50%-75% state of charge interval;

[0036] At the same temperature, the hysteresis voltage ratio in the range of 20%-50% state of charge is set to a fixed value, which is numerically equal to the average value of the hysteresis voltage ratio in the range, and the temperature and hysteresis voltage ratio function in the range of 20%-50% state of charge is obtained by fitting as shown in formula (8);

[0037] β T_20％-50％ =k·exp(l·T)+m (8)

[0038] In formula (8), β T_20％-50％ It represents the hysteresis voltage ratio in the range of 20%-50% state of charge, where k, l and m are all constants;

[0039] The relationship between temperature and hysteresis voltage ratio in the range of 50%-75% state of charge is analyzed, and the hysteresis voltage ratio at 10°C is set as the standard value. Then, the hysteresis voltage ratio at different temperatures is calculated by formula (9);

[0040] δ T =β T / β 10 (9)

[0041] In formula (9), δ TIndicates the hysteresis voltage ratio at T℃, β 10 Indicates the hysteresis voltage ratio at 10°C;

[0042] The relationship between temperature and hysteresis voltage ratio is analyzed, and a temperature and hysteresis voltage ratio function shown in formula (10) is established in the range of 50%-75% state of charge;

[0043] δ T = p·T 2 +q·T+r (10)

[0044] In formula (10), p, q, and r are all constants;

[0045] According to the relationship between the hysteresis voltage ratio and the state of charge at 10°C, the relationship function between the hysteresis voltage ratio and the state of charge at 10°C is established as follows:

[0046] β 10 =x0+exp[-((soc+y0) / z0) 2 ]+x1+exp[-((soc+y1) / z1) 2 ] (11)

[0047] Wherein, soc represents the state of charge in the range of 50%-75%, and x0, y0, z0, x1, y1, z1 are all constants;

[0048] The temperature and hysteresis voltage ratio function in the 50%-75% state of charge range is:

[0049] β T_50％-75％ =δ T β 10 (12)

[0050] In formula (12), β T_50％-75％ Indicates the hysteresis voltage ratio within the range of 50%-75% state of charge;

[0051] According to the relationship between hysteresis voltage and state of charge at 0℃, the function of hysteresis voltage and state of charge at 0℃ is fitted as follows:

[0052]

[0053] Among them, e, f n ,ω,g n All are constants, n is an integer;

[0054] In the range of 20%-50% state of charge, the hysteresis voltage ratio is calculated using formula (8); in the range of 50%-75% state of charge, the hysteresis voltage ratio is calculated using formula (12).

[0055] The battery equivalent circuit model is any one of a Thevenin equivalent circuit model, a second-order RC equivalent circuit model or a third-order RC equivalent circuit model.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] The present invention uses temperature as a variable, performs an OCV-SOC test of a power battery at different temperatures, collects the charge and discharge open circuit voltages corresponding to different states of charge; analyzes the relationship between temperature and average open circuit voltage, and establishes a temperature-adaptive open circuit voltage sub-model; analyzes the relationship between temperature and hysteresis voltage, and establishes a temperature-adaptive hysteresis sub-model; finally, the open circuit voltage sub-model and the hysteresis sub-model are integrated into an equivalent circuit model to obtain a temperature-adaptive power battery hysteresis model, thereby improving the temperature adaptability of the model, and further improving the accuracy of the model in estimating the state of charge.

[0058] The test results show that the model proposed in the present invention can achieve higher accuracy at different temperatures. Specifically, in the DST and US06 operating conditions at all test temperatures, the cumulative error and root mean square error of the temperature-adaptive hysteresis sub-model constructed by the present invention are lower than the first-order RC equivalent circuit model and single-state hysteresis model of the prior art. By using limited temperature data, the present invention enables the model to adapt to temperature changes within a certain range, thereby improving the model accuracy, and the method is suitable for power batteries under different operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is the overall flow chart of the present invention;

[0060] Figure 2 The average open circuit voltage and state of charge curve at different temperatures;

[0061] Figure 3 It is the curve diagram of hysteresis voltage and state of charge at different temperatures;

[0062] Figure 4 It is a temperature-adaptive power battery hysteresis model;

[0063] Figure 5 It is the current diagram of DST condition;

[0064] Figure 6 This is the current diagram of US06 working condition;

[0065] Figure 7 Comparison of the cumulative errors of the three models in DST conditions at different temperatures;

[0066] Figure 8 This is a comparison chart of the root mean square errors of the three models in DST conditions at different temperatures;

[0067] Fig. 9 This is a comparison chart of the cumulative errors of the three models in US06 working condition at different temperatures;

[0068] Fig.10 This is a comparison chart of the root mean square errors of the three models in US06 working conditions at different temperatures. DETAILED DESCRIPTION

[0069] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present application is not limited thereto.

[0070] The present invention provides a method for constructing a power battery hysteresis model based on temperature adaptation (hereinafter referred to as the method), which specifically comprises the following steps:

[0071] Step 1: Carry out capacity test at different temperatures to measure the capacity of the power battery at different temperatures;

[0072] Step 2: Perform OCV-SOC test on power battery at different temperatures, and collect charge and discharge open circuit voltages of power battery at different charge states at different temperatures; the temperature range is 0-40℃, and each 10℃ is a test temperature; the battery is charged and discharged with a step length of 10% of the total capacity, so the test points of the charge state of the power battery are 0, 10%, 20%,..., 100% respectively; after each step length of charge and discharge is completed, rest for one hour before performing the next step length of charge and discharge, until the terminal voltage reaches the charge and discharge cut-off voltage value, and the terminal voltage obtained at the end of each rest is regarded as the charge and discharge open circuit voltage;

[0073] Step 3: Based on the OCV-SOC test data, let the average open circuit voltage be equal to half of the sum of the charge and discharge open circuit voltages of the power battery, calculate the average open circuit voltage of the power battery at different temperatures, and plot it as follows: Figure 2 The average open circuit voltage and state of charge curves of the power battery at different temperatures are shown;

[0074] Step 4: Analyze the relationship between temperature and average open circuit voltage according to the average open circuit voltage and state of charge curve, and establish an open circuit voltage sub-model;

[0075] Step 4.1: Set the average open circuit voltage at 0°C as the standard value, and calculate the average open circuit voltage ratio at different temperatures by formula (1);

[0076] ΦT=U oc_T / U oc_0 (1)

[0077] In formula (1), Φ T Indicates the average open circuit voltage ratio at T℃, U oc_T , U oc_0Respectively represent the average open circuit voltage of the power battery at T℃ and 0℃;

[0078] Step 4.2: Analyze the relationship between temperature and average open circuit voltage ratio. Since the trend of the average open circuit voltage ratio is different in different charge state intervals, the charge state is divided into three intervals according to the trend of the average open circuit voltage ratio, so as to better analyze and fit the temperature and average open circuit voltage ratio function. The three intervals are: 0 state of charge, 10%-50% state of charge interval and 60%-100% state of charge interval. The relationship between temperature and average open circuit voltage ratio is analyzed in the three intervals, and the temperature and average open circuit voltage ratio functions corresponding to each interval are obtained as follows:

[0079] Φ T_0 =a1T 3 +b1T 2 +c1T+d1 (2)

[0080] Φ T_10％-50％ =a2T 3 +b2T 2 +c2T+d2 (3)

[0081] Φ T_60％-100％ =a3T 3 +b3T 2 +c3T+d3 (4)

[0082] In the formula, Φ T_0 Indicates the average open circuit voltage ratio when the state of charge is 0, Φ T_10％-50％ Indicates the average open circuit voltage ratio within the range of 10%-50% state of charge, Φ T_60％-100％ Indicates the average open circuit voltage ratio in the range of 60%-100% state of charge; a1, b1, c1, d1, a2, b2, c2, d2, a3, b3, c3, d3 are all constants;

[0083] Step 4.3: Establish an open circuit voltage sub-model as shown in equation (5);

[0084] U oc_T =Φ T ·U oc_0 (5)

[0085] In formula (5), when the state of charge is 0, the average open circuit voltage ratio is calculated using formula (2); when the state of charge is in the range of 10%-50%, the average open circuit voltage ratio is calculated using formula (3); when the state of charge is in the range of 60%-100%, the average open circuit voltage ratio is calculated using formula (4);

[0086] Step 5: Analyze the relationship between temperature and hysteresis voltage and establish a hysteresis sub-model;

[0087] Step 5.1: Based on the test data obtained in step 2, calculate the hysteresis voltage U of the power battery by formula (6): h ;

[0088] U h =ocv charge -ocv discharge (6)

[0089] In formula (6), ocv charge is the open circuit voltage of the power battery in the charging state, ocv discharge It is the open circuit voltage of the power battery in the discharge state;

[0090] Draw as Figure 3 The hysteresis voltage curves at different temperatures are shown, the temperature and hysteresis voltage curves are analyzed, the state of charge intervals that do not clearly reflect the correlation between temperature and hysteresis voltage are eliminated, the state of charge interval range is narrowed to 20%-75%, and the relationship between temperature and hysteresis voltage is analyzed within the 20%-75% state of charge interval;

[0091] Step 5.2: Set the hysteresis voltage at 0°C as the standard value, and calculate the hysteresis voltage ratio at different temperatures using formula (7);

[0092] β T =U h(T) / U h(0) (7)

[0093] In formula (7), β T Indicates the hysteresis voltage ratio at T℃, U h(T) , U h(0) Respectively represent the hysteresis voltage at T℃ and 0℃;

[0094] Step 5.3: Analyze the relationship between temperature and hysteresis voltage ratio. The change trend of hysteresis voltage ratio is different in different state of charge intervals. Therefore, the state of charge is divided into two intervals according to the change trend of hysteresis voltage ratio, namely 20%-50% state of charge interval and 50%-75% state of charge interval. The relationship between temperature and hysteresis voltage ratio is analyzed in these two intervals.

[0095] Step 5.3.1: For the same temperature, within the range of 20%-50% state of charge, the hysteresis voltage ratio changes little, so the hysteresis voltage ratio curve within this range is approximated as a straight line, and the hysteresis voltage ratio is set to a fixed value, which is numerically equal to the average value of the hysteresis voltage ratio within this range; at different temperatures, the hysteresis voltage ratio within the range of 20%-50% state of charge has a fixed value, and the temperature and hysteresis voltage ratio function within the range of 20%-50% state of charge shown in formula (8) is obtained by fitting;

[0096] β T_20％-50％ =k·exp(l·T)+m (8)

[0097] In formula (8), β T_20％-50％ It represents the hysteresis voltage ratio in the range of 20%-50% state of charge, where k, l and m are all constants;

[0098] Step 5.3.2: Analyze the relationship between temperature and hysteresis voltage ratio in the range of 50%-75% state of charge, set the hysteresis voltage ratio at 10°C as the standard value, and calculate the hysteresis voltage ratio at different temperatures by formula (9);

[0099] δ T =β T / β 10 (9)

[0100] In formula (9), δ T Indicates the hysteresis voltage ratio at T℃, β 10 Indicates the hysteresis voltage ratio at 10°C;

[0101] Step 5.3.3: Analyze the relationship between temperature and hysteresis voltage ratio, and establish the temperature and hysteresis voltage ratio function shown in formula (10) in the range of 50%-75% state of charge;

[0102] δ T = p·T 2 +q·T+r (10)

[0103] In formula (10), p, q, and r are all constants;

[0104] Step 5.3.4: According to the relationship between the hysteresis voltage ratio and the state of charge at 10°C, the relationship function between the hysteresis voltage ratio and the state of charge at 10°C is established as follows:

[0105] β 10 =x0+exp[-((soc+y0) / z0) 2 ]+x1+exp[-((soc+y1) / z1) 2 ] (11)

[0106] Wherein, soc represents the state of charge in the range of 50%-75%, and x0, y0, z0, x1, y1, z1 are all constants;

[0107] The temperature and hysteresis voltage ratio function in the 50%-75% state of charge range is:

[0108] β T_50％-75％ =δ T β 10 (12)

[0109] In formula (12), β T_50％-75％ Indicates the hysteresis voltage ratio within the range of 50%-75% state of charge;

[0110] According to the relationship between hysteresis voltage and state of charge at 0℃, the function of hysteresis voltage and state of charge at 0℃ is fitted as follows:

[0111]

[0112] Among them, e, f n ,ω,g n All are constants, n is an integer;

[0113] Step 5.4: Establish the hysteresis submodel as shown in equation (13):

[0114] U h(T) =β T ·U h(0) (14)

[0115] In formula (14), within the range of 20%-50% state of charge, the hysteresis voltage ratio is calculated using formula (8); within the range of 50%-75% state of charge, the hysteresis voltage ratio is calculated using formula (12);

[0116] Step 6: Integrate the open circuit voltage sub-model and the hysteresis sub-model into the Thevenin equivalent circuit model to obtain Figure 4 The temperature-adaptive power battery hysteresis model shown here completes the construction of the temperature-adaptive power battery hysteresis model; Figure 4 Middle,U oc_T represents the open circuit voltage sub-model, and H represents the hysteresis sub-model.

[0117] Test verification

[0118] The power battery hysteresis model constructed by this method is based on the Thevenin equivalent circuit model. Therefore, it is necessary to perform parameter identification on the Thevenin equivalent circuit model to obtain the internal resistance, polarization resistance and polarization capacitance of the equivalent circuit model. The power battery hysteresis model after parameter identification is used to estimate the state of charge of the power battery.

[0119] In order to verify the effect of the power battery hysteresis model constructed by this method, the first-order RC equivalent circuit model (1-RC-ECM) and the single-state hysteresis model (H S -ECM) and the temperature adaptive power battery hysteresis model (H T-ECM), the model accuracy is compared under different temperatures and different working conditions. The model accuracy is measured by cumulative error and root mean square error (RMSE). The calculation formulas of cumulative error and root mean square error RMSE are:

[0120]

[0121]

[0122] Among them, U i_M is the model output voltage, U t is the actual terminal voltage of the battery, and j is the number of errors.

[0123] In this example, the test battery is a cylindrical lithium-ion battery LR18650SZ with a rated capacity of 2400mAh and a nominal voltage of 3.6V. The test is carried out on a battery testing system produced by the Newway Group with a current range of 50mA-10A and a voltage range of 25mV-5V. The accuracy of current and voltage is ±0.1% of the full scale. The test battery is placed in a DHT environmental test chamber to simulate temperature changes.

[0124] The test battery was subjected to OCV-SOC test at 0°C, 10°C, 20°C, 30°C and 40°C. The specific test steps are as follows:

[0125] (1) The battery is charged in constant current and constant voltage mode; first, the battery is charged at a rate of 0.5C to the charge cut-off voltage, and then the battery is charged at a constant voltage until the charging current drops to a rate of 0.02C; C represents the charge and discharge rate;

[0126] (2) After charging is completed, the battery is discharged at a rate of 0.5C and a step size of 10% of the total capacity after a one-hour rest. After each step of discharge, the battery is discharged for one hour and then discharged for the next step. This cycle is repeated until the voltage reaches the discharge cut-off voltage value. The terminal voltage value obtained at the end of each rest is regarded as the discharge open circuit voltage under the corresponding charge state.

[0127] (3) After one hour of rest, the battery is charged at a rate of 0.5C and in steps of 10% of the total capacity, similar to the discharge process, until the voltage reaches the charge cut-off voltage. The terminal voltage value obtained at the end of each rest period is regarded as the charge open circuit voltage under the corresponding charge state.

[0128] In addition, the dynamic stress test (DST) condition and the US06 drive cycle current condition (US06) were selected to simulate the actual working environment of the battery. The battery was discharged at 10℃, 17℃, 20℃, room temperature (25℃), 30℃, 37℃ and 40℃ respectively with the above two working conditions. First, the battery was fully charged in a constant current and constant voltage manner, and then the DST and US06 working conditions were introduced into the battery test system respectively, and the battery was discharged to a cut-off voltage of 3.0V. The sampling interval was set to 1s to obtain the test data; Figure 5 , 6 They are respectively the dynamic stress test condition current and the US06 drive circulating current condition current.

[0129] Comparison of the cumulative errors of the three models in DST conditions at 10℃, 17℃, 20℃, room temperature (25℃), 30℃, 37℃ and 40℃ Figure 7 shown.

[0130] Comparison of the root mean square errors of the three models in DST conditions at 10℃, 17℃, 20℃, room temperature (25℃), 30℃, 37℃ and 40℃ Figure 8 shown.

[0131] Comparison of the cumulative errors of the three models in US06 condition at 10℃, 17℃, 20℃, room temperature (25℃), 30℃, 37℃ and 40℃ Fig. 9 shown.

[0132] Comparison of the root mean square errors of the three models in US06 conditions at 10℃, 17℃, 20℃, room temperature (25℃), 30℃, 37℃ and 40℃ Fig.10 shown.

[0133] Table 1 shows the error data of the three models in DST conditions at different temperatures, and Table 2 shows the error data of the three models in US06 conditions at different temperatures.

[0134] Table 1 Error data of three models in DST conditions at different temperatures

[0135]

[0136]

[0137] The results in Tables 1 and 2 show that the method proposed in the present invention has better S -ECM has higher model accuracy. Specifically, H T The cumulative error produced by H-ECM is 7.74%-39.86% lower than that of 1-RC-ECM, and the root mean square error is 6.40%-30.12% lower;T -The cumulative error ratio of ECM is H S -ECM is 0.42%-13.78% lower, and the root mean square error is 0.52%-8.75% lower. It also shows that the method proposed by the present invention can be applied to different working conditions and has universal applicability.

[0138] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A method for constructing a power battery hysteresis model based on temperature adaptation, characterized in that: The method comprises the following steps: Step 1: Carry out capacity test at different temperatures to measure the capacity of the power battery at different temperatures; Step 2: Perform an open circuit voltage-state of charge test at different temperatures to collect the charge and discharge open circuit voltages corresponding to different states of charge of the power battery at different temperatures; Step 3: Let the average open circuit voltage be equal to half of the sum of the charge and discharge open circuit voltages, and calculate the average open circuit voltage of the power battery at different temperatures; Step 4: Analyze the relationship between temperature and average open circuit voltage, and establish an open circuit voltage sub-model. The expression is: IN oc_T =Φ T ·IN oc_0 (5) Among them, Φ T Indicates the average open circuit voltage ratio at T℃, U oc_T , U oc_0 Respectively represent the average open circuit voltage of the power battery at T℃ and 0℃; Step 5: Analyze the relationship between temperature and hysteresis voltage and establish a hysteresis sub-model. The expression is: IN h(T) =β T ·IN h(0) (14) Among them, β T Indicates the hysteresis voltage ratio at T℃, U h(T) , U h(0) Respectively represent the hysteresis voltage at T℃ and 0℃; Step 6: Integrate the open circuit voltage sub-model and the hysteresis sub-model into the battery equivalent circuit model to obtain the temperature adaptive power battery hysteresis model. This completes the construction of the temperature adaptive power battery hysteresis model.

2. The method for constructing a power battery hysteresis model based on temperature adaptation according to claim 1, characterized in that: The establishment of the open circuit voltage sub-model includes the following steps: Step 4.1: Set the average open circuit voltage at 0°C as the standard value, and calculate the average open circuit voltage ratio at different temperatures by formula (1); Φ T =U oc_T / IN oc_0 (1) Step 4.2: The state of charge is divided into three intervals according to the change trend of the average open circuit voltage ratio, namely: the state of charge is 0, the state of charge interval of 10%-50% and the state of charge interval of 60%-100%. The relationship between temperature and the average open circuit voltage ratio is analyzed in the three intervals, and the temperature and average open circuit voltage ratio functions corresponding to each interval are obtained respectively: Φ T_0 =a1T 3 +b1T 2 +c1T+d1 (2) <h2 style=";text-align:left;direction:ltr">Φ<h2 style=";text-align:left;direction:ltr"> T_10％-50％ <h2 style=";text-align:left;direction:ltr"> =a2T<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> +b2T<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +c2T+d2 (3) <h2 style=";text-align:left;direction:ltr">Φ<h2 style=";text-align:left;direction:ltr"> T_60％-100％ <h2 style=";text-align:left;direction:ltr"> =a3T<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> +b3T<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +c3T+d3 (4) In the formula, Φ T_0 Indicates the average open circuit voltage ratio when the state of charge is 0, Φ T_10％-50％ Indicates the average open circuit voltage ratio within the range of 10%-50% state of charge, Φ T_60％-100％ Indicates the average open circuit voltage ratio in the range of 60%-100% state of charge; a1, b1, c1, d1, a2, b2, c2, d2, a3, b3, c3, d3 are all constants; When the state of charge is 0, the average open circuit voltage ratio is calculated using formula (2); when the state of charge is in the range of 10%-50%, the average open circuit voltage ratio is calculated using formula (3); when the state of charge is in the range of 60%-100%, the average open circuit voltage ratio is calculated using formula (4).

3. The method for constructing a power battery hysteresis model based on temperature adaptation according to claim 1, characterized in that: The establishment of the hysteresis submodel includes the following steps: Step 5.1: Calculate the hysteresis voltage of the power battery by using formula (6); U h =ocv charge -ocv discharge (6) In formula (6), ocv charge is the open circuit voltage of the power battery in the charging state, ocv discharge It is the open circuit voltage of the power battery in the discharge state; Draw hysteresis voltage curves at different temperatures, analyze the relationship between temperature and hysteresis voltage, eliminate the state of charge intervals that do not clearly reflect the correlation between temperature and hysteresis voltage, narrow the state of charge interval range to 20%-75%, and analyze the relationship between temperature and hysteresis voltage within the 20%-75% state of charge interval; Step 5.2: Set the hysteresis voltage at 0°C as the standard value, and calculate the hysteresis voltage ratio at different temperatures using formula (7); β T =U h(T) / IN h(0) (7) In formula (7), β T Indicates the hysteresis voltage ratio at T℃, U h(T) , U h(0) Respectively represent the hysteresis voltage at T℃ and 0℃; Step 5.3: Divide the state of charge into two intervals according to the change trend of the hysteresis voltage ratio, namely, a 20%-50% state of charge interval and a 50%-75% state of charge interval; At the same temperature, the hysteresis voltage ratio in the range of 20%-50% state of charge is set to a fixed value, which is numerically equal to the average value of the hysteresis voltage ratio in the range, and the temperature and hysteresis voltage ratio function in the range of 20%-50% state of charge is obtained by fitting as shown in formula (8); β T_20％-50％ =k·exp(l·T)+m (8) In formula (8), β T_20％-50％ It represents the hysteresis voltage ratio in the range of 20%-50% state of charge, where k, l and m are all constants; The relationship between temperature and hysteresis voltage ratio in the range of 50%-75% state of charge is analyzed, and the hysteresis voltage ratio at 10°C is set as the standard value. Then, the hysteresis voltage ratio at different temperatures is calculated by formula (9); d T =b T / b 10 (9) In formula (9), δ T Indicates the hysteresis voltage ratio at T℃, β 10 Indicates the hysteresis voltage ratio at 10°C; The relationship between temperature and hysteresis voltage ratio is analyzed, and a temperature and hysteresis voltage ratio function shown in formula (10) is established in the range of 50%-75% state of charge; δ T =p·T 2 +q·T+r (10) In formula (10), p, q, and r are all constants; According to the relationship between the hysteresis voltage ratio and the state of charge at 10°C, the relationship function between the hysteresis voltage ratio and the state of charge at 10°C is established as follows: β 10 =x0+exp[-((soc+y0) / z0) 2 ]+x1+exp[-((soc+y1) / z1) 2 ] (11) Wherein, soc represents the state of charge in the range of 50%-75%, and x0, y0, z0, x1, y1, z1 are all constants; The temperature and hysteresis voltage ratio function in the 50%-75% state of charge range is: b T_50％-75％ =d T ·b 10 (12) In formula (12), β T_50％-75％ Indicates the hysteresis voltage ratio within the range of 50%-75% state of charge; According to the relationship between hysteresis voltage and state of charge at 0℃, the function of hysteresis voltage and state of charge at 0℃ is fitted as follows: Among them, e, f n ,ω,g n All are constants, n is an integer; In the range of 20%-50% state of charge, the hysteresis voltage ratio is calculated using formula (8); in the range of 50%-75% state of charge, the hysteresis voltage ratio is calculated using formula (12).

4. The method for constructing a power battery hysteresis model based on temperature adaptation according to claim 1, characterized in that: The battery equivalent circuit model is any one of a Thevenin equivalent circuit model, a second-order RC equivalent circuit model or a third-order RC equivalent circuit model.

5. The method for constructing a power battery hysteresis model based on temperature adaptation according to claim 1, characterized in that: In step 2, the steps of the open circuit voltage-state of charge test are: (1) The battery is charged in constant current and constant voltage mode; first, the battery is charged at a rate of 0.5C to the charge cut-off voltage, and then the battery is charged at a constant voltage until the charging current drops to a rate of 0.02C; C represents the charge and discharge rate; (2) After charging is completed, rest for one hour, and then discharge the battery at a rate of 0.5C and a step size of 10% of the total capacity. After each step of discharge, rest for one hour, and then discharge the battery at the next step of discharge, and repeat this cycle until the voltage reaches the discharge cut-off voltage value; The terminal voltage value obtained at the end of each rest period is regarded as the discharge open circuit voltage at the corresponding state of charge; (3) After the discharge is completed, rest for one hour, and then charge the battery at a rate of 0.5C and a step size of 10% of the total capacity. After each step of charging, rest for one hour, and then charge the next step of charging, and cycle in sequence until the voltage reaches the charging cut-off voltage value; The terminal voltage value obtained at the end of each rest period is regarded as the charging open circuit voltage at the corresponding state of charge.

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