A power calculation method, system and electric vehicle for a power battery

Abstract

The present application discloses a power calculation method, system and electric vehicle for a power battery, which obtains the state of charge (SOC), battery temperature and the lowest single cell voltage of the power battery; according to the SOC and battery temperature, looks up the corresponding first looked-up power from a pre-stored two-dimensional discharge power table; according to the battery temperature and the lowest single cell voltage, looks up the corresponding second looked-up power from the pre-stored two-dimensional discharge power table; if the SOC is less than or equal to a preset value, determines the smaller of the first looked-up power and the second looked-up power as the theoretical maximum available power of the power battery. Since the theoretical maximum available power is determined from the first looked-up power and the second looked-up power, the theoretical maximum available power takes into account the SOC, battery temperature and the lowest single cell voltage, reducing the risk of over-discharge of the power battery.

Description

Technical Field

[0001] The present application relates to the field of automotive electrical technologies, and particularly, to a method and a system for calculating the power of a power battery and an electric vehicle. Background Art

[0002] Facing the increasingly severe problems of energy shortage and environmental pollution, China vigorously promotes the development of electric vehicles. The power battery is the core component of an electric vehicle, and its discharge performance directly affects the power performance of the electric vehicle. To improve the use efficiency and safety performance of the power battery, it is necessary to control the maximum discharge power that the power battery is allowed to output in real time.

[0003] In the prior art, the maximum allowable discharge power of a power battery is mainly obtained by performing a look-up table linear interpolation based on test data in combination with the SOC (State of Charge) of the battery. However, in actual applications, the battery discharge power only considers the discharge cut-off condition and does not involve other conditions. For example, in the low SOC stage, the deviation of the SOC estimated value often increases the risk of over-discharging the battery, affecting driving safety. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a method and a system for calculating the power of a power battery and an electric vehicle, so as to solve the problem of calculating the maximum allowable discharge power of the power battery at different SOC stages.

[0005] To solve the above problems, the present application adopts the following technical solutions for implementation:

[0006] The present application provides a method for calculating the power of a power battery, including:

[0007] Obtaining the state of charge SOC, the battery temperature, and the lowest single-cell voltage of the power battery;

[0008] According to the state of charge SOC and the battery temperature, looking up the corresponding first look-up table power from a pre-stored discharge power table;

[0009] According to the battery temperature and the lowest single-cell voltage, looking up the corresponding second look-up table power from the pre-stored discharge power table;

[0010] If the state of charge SOC is less than or equal to a preset value, then determining the smaller value of the first look-up table power and the second look-up table power as the theoretical maximum available power P3 of the power battery; if the state of charge SOC is greater than the preset value, then taking the first look-up table power as the maximum available discharge power P3 of the power battery.

[0011] Further, the battery temperature includes the highest single - cell temperature and the lowest single - cell temperature. The step of looking up the corresponding first looked - up power from the pre - stored discharge power table according to the state of charge (SOC) and the battery temperature specifically includes:

[0012] Looking up the corresponding third looked - up power from the pre - stored discharge power table according to the state of charge (SOC) and the highest single - cell temperature;

[0013] Looking up the corresponding fourth looked - up power from the pre - stored discharge power table according to the state of charge (SOC) and the lowest single - cell temperature;

[0014] Determining the smaller of the third looked - up power and the fourth looked - up power as the first looked - up power.

[0015] Further, the battery temperature includes the highest single - cell temperature and the lowest single - cell temperature. The step of looking up the corresponding second looked - up power from the pre - stored discharge power table according to the battery temperature and the lowest single - cell voltage specifically includes:

[0016] Looking up the corresponding fifth looked - up power from the pre - stored discharge power table according to the lowest single - cell voltage and the highest single - cell temperature;

[0017] Looking up the corresponding sixth looked - up power from the pre - stored discharge power table according to the lowest single - cell voltage and the lowest single - cell temperature;

[0018] Determining the smaller of the fifth looked - up power and the sixth looked - up power as the second looked - up power.

[0019] Further, the step of obtaining the state of charge (SOC), battery temperature, and lowest single - cell voltage of the power battery specifically includes:

[0020] Checking the state of the power battery;

[0021] If the power battery is in the discharge mode, then obtaining the state of charge (SOC), the battery temperature, and the lowest single - cell voltage of the power battery.

[0022] Further, when the power battery is in a fault state, after the step of determining the smaller of the first looked - up power and the second looked - up power as the theoretical maximum available power P3 of the power battery if the state of charge (SOC) is less than or equal to the preset value, the power calculation method further includes:

[0023] Detecting the fault of the power battery and determining the fault level;

[0024] Look up the corresponding limit power P4 from the pre-stored discharge power table according to the fault level;

[0025] If the limit power P4 is greater than or equal to the theoretical maximum available power P3, determine the theoretical maximum available power P3 as the maximum fault available power P5 of the power battery in the fault state. If the limit power P4 is less than the theoretical maximum available power P3, the value of the maximum fault available power P5 of the power battery in the fault state decreases linearly from the theoretical maximum available power P3 to the limit power P4.

[0026] Further, when the limit power P4 is less than the theoretical maximum available power P3, the maximum fault available power P5 of the power battery in the fault state, the theoretical maximum available power P3, and the limit power P4 satisfy the relationship:

[0027] where t is the time after the power battery fails, and N is a constant coefficient.

[0028] This application also provides a power calculation system for a power battery, including: an information acquisition module, a power lookup module, and a power calculation module; where

[0029] The information acquisition module is used to acquire the state of charge SOC, battery temperature, and the lowest single-cell voltage of the power battery;

[0030] The power lookup module is used to look up the corresponding first lookup power from the pre-stored discharge power table according to the state of charge SOC and the battery temperature, and look up the corresponding second lookup power from the pre-stored discharge power table according to the battery temperature and the lowest single-cell voltage;

[0031] The power calculation module is used to compare the state of charge SOC with a preset value and determine the theoretical maximum available power P3 of the power battery.

[0032] Further, the power calculation system further includes a test module and a generation module, where

[0033] The test module is used to test the discharge capacity of the power battery under different states of charge SOC, different battery temperatures, and different single-cell voltages, and generate a test result; and

[0034] The generation module is connected to the test module, and the generation module is used to transform the test result into a discharge power table for the power battery based on the state of charge SOC, the battery temperature, and the single-cell voltage.

[0035] Further, the power calculation system further includes a fault detection module for detecting faults of the power battery.

[0036] This application also provides an electric vehicle, including:

[0037] The above-mentioned power calculation system of the power battery; and

[0038] A driving device connected to the power calculation system.

[0039] In the power calculation method, system and electric vehicle of the power battery according to the embodiments of this application, by obtaining the state of charge (SOC), battery temperature and the lowest single-cell voltage of the power battery, according to the SOC and battery temperature, the corresponding first look-up power is found from a pre-stored discharge power table, and according to the battery temperature and the lowest single-cell voltage, the corresponding second look-up power is found from the pre-stored discharge power table. If the SOC is less than or equal to a preset value, the smaller of the first look-up power and the second look-up power is determined as the theoretical maximum available power of the power battery. Since the theoretical maximum available power is determined from the first look-up power and the second look-up power, the theoretical maximum available power takes into account the SOC, battery temperature and the lowest single-cell voltage, improves the accuracy of calculating the theoretical maximum available power, and reduces the risk of over-discharge of the power battery. Description of the Drawings

[0040] Figure 1 It is a schematic flowchart of a power calculation method for a power battery provided by an embodiment of this application;

[0041] Figure 2 It is a schematic flowchart of step S2 in a power calculation method for a power battery provided by an embodiment of this application;

[0042] Figure 3 It is a schematic flowchart of step S3 in a power calculation method for a power battery provided by an embodiment of this application;

[0043] Figure 4 It is a schematic flowchart of another power calculation method for a power battery provided by an embodiment of this application; and

[0044] Figure 5 It is a system diagram of a power calculation system for a power battery provided by an embodiment of this application. Detailed Embodiments

[0045] The following describes in detail the specific embodiments of this application with reference to the drawings.

[0046] It should be noted that, without conflict, the embodiments in the present application and the technical features in the embodiments can be combined with each other. The detailed description in the specific implementation manners should be understood as an explanatory illustration of the purpose of the present application and should not be regarded as an improper limitation of the present application.

[0047] It should be understood that the orientation or positional relationship is based on the orientation or positional relationship shown in the drawings. These orientation terms are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present application.

[0048] In the description of the present application, the terms "first / second" are only used to distinguish similar objects and do not represent a specific order for the objects. It can be understood that "first / second" can be interchanged with a specific order or sequence when permitted, so that the embodiments of the present application described here can be implemented in an order other than that illustrated or described here.

[0049] The power battery is the core component of an electric vehicle, the key to determining the overall performance of the electric vehicle, and at the same time an important symbol that distinguishes an electric vehicle from a traditional internal combustion engine vehicle. The charging and discharging capabilities of the power battery directly affect the power performance and drivability of the electric vehicle. In order to maximize the performance of the power battery and protect the battery from overcharging or over-discharging, the key lies in how to estimate the maximum available power of the power battery in real time.

[0050] In the prior art, the maximum allowable discharge power of the power battery is mainly obtained by linearly interpolating a look-up table based on test data in combination with parameters such as the battery temperature and the state of charge (SOC) of the battery system. Existing battery over-discharge calculation method 1: When the estimated value of SOC is lower than the discharge cut-off SOC, the discharge power of the battery pack is limited to 0, or when the terminal voltage of the single battery with the smallest capacity in the battery pack is less than the set threshold voltage, the discharge power of the battery pack is limited to 0. Battery over-discharge calculation method 1 does not consider the influence of temperature on the battery discharge power and only considers the discharge cut-off condition.

[0051] Existing battery over-discharge calculation method 2: Calculate the state of charge (SOC) of the power battery of the electric vehicle, detect the battery temperature of the power battery, and look up the look-up power corresponding to the SOC and temperature in a pre-stored discharge power table as the theoretical maximum power of the power battery. The power limit ratio of battery over-discharge protection method 2 is completely based on the difference between the current battery voltage and the cut-off voltage, which is likely to result in not meeting the requirements of the overall vehicle power performance in the medium and high SOC stages, and is likely to cause over-discharge of the battery in the low SOC stage and when the SOC accuracy is insufficient.

[0052] However, both the second method and the first method for calculating battery over-discharge target the entire SOC stage. In practical applications, especially in the low SOC stage, the deviation of the SOC estimation value may increase the risk of battery over-discharge and affect driving safety. Therefore, it is extremely important to select or determine different maximum available discharge powers for different SOC stages.

[0053] In view of this, as Figure 1 shown, an embodiment of the present application provides a power calculation method for a power battery, including:

[0054] S1. Obtain the state of charge (SOC), battery temperature, and the lowest cell voltage of the power battery;

[0055] S2. According to the state of charge (SOC) and the battery temperature, look up the corresponding first table-looked-up power from a pre-stored discharge power table;

[0056] S3. According to the battery temperature and the lowest cell voltage, look up the corresponding second table-looked-up power from a pre-stored discharge power table;

[0057] S4. If the state of charge (SOC) is less than or equal to a preset value, determine the smaller value of the first table-looked-up power and the second table-looked-up power as the theoretical maximum available power of the power battery; if the state of charge (SOC) is greater than the preset value, use the first table-looked-up power as the maximum available discharge power P3 of the power battery.

[0058] Specifically, the ratio of the remaining capacity of a power battery after being used for a period of time or left unused for a long time to the capacity in its fully charged state is called the state of charge (SOC) (State of Charge). SOC is usually expressed as a percentage, and its value ranges from 0 to 1. When SOC = 0, it means the battery is fully discharged, and when SOC = 1, it means the battery is fully charged. Calculate the state of charge (SOC) of the power battery. For example, obtain the state of charge (SOC) of the power battery through the information acquisition module 110.

[0059] Since the capacity of a power battery is related not only to the state of charge (SOC) but also to the battery temperature, it is necessary to detect the battery temperature in order to effectively and accurately calculate the capacity of the power battery and thus accurately calculate the available power. For example, obtain the battery temperature through the information acquisition module 110.

[0060] Since the voltage distribution of the individual cells in a power battery is very complex, the voltage of the cell with the smallest capacity drops earliest and fastest and is most likely to be over-discharged. In the embodiments of the present invention, the voltage of each individual cell in the battery is detected in real time, and a lowest voltage value is selected from them, and the power calculation is based on the lowest voltage value in the power battery.

[0061] Look up the corresponding first table-looked-up power P1 from the pre-stored discharge power table according to the state of charge (SOC) and the battery temperature. Specifically, by measuring the discharge powers at different states of charge (SOC) and different battery temperatures, a two-dimensional discharge power table 1 is plotted and stored. When performing the protection calculation for the over-discharge power, look up the corresponding first table-looked-up power P1 from the pre-stored two-dimensional discharge power table 1 according to the state of charge (SOC) and the battery temperature.

[0062] Look up the corresponding second table-looked-up power P2 from the pre-stored discharge power table according to the battery temperature and the lowest cell voltage. Specifically, by measuring the discharge powers at the lowest cell voltage and different battery temperatures, a two-dimensional discharge power table 2 is plotted and stored. When performing the protection calculation for the over-discharge power, look up the corresponding second table-looked-up power P2 from the pre-stored two-dimensional discharge power table 2 according to the battery temperature and the lowest cell voltage. It should be noted that in the two-dimensional discharge power table 1 and the two-dimensional discharge power table 2, due to different variables used when measuring, plotting, and generating the tables or curves, the data in the two-dimensional discharge power table 1 and the two-dimensional discharge power table 2 are not the same. In particular, the two-dimensional discharge power table 1 and the two-dimensional discharge power table 2 can be two different tables, or they can be the "section" charts according to different parameters in the same three-dimensional discharge power table.

[0063] It should be noted that the order between steps S2 and S3 can be exchanged in some cases, and it should not be construed as a limitation to this application. For example, first look up the corresponding second table-looked-up power P2 from the pre-stored discharge power table according to the battery temperature and the lowest cell voltage, and then look up the corresponding first table-looked-up power P1 from the pre-stored discharge power table according to the state of charge (SOC) and the battery temperature. The order of the two lookups does not limit the sequence.

[0064] Compare the preset value with the state of charge (SOC). If the state of charge (SOC) is less than or equal to the preset value, then determine the smaller value between the first table-looked-up power P1 and the second table-looked-up power P2 as the theoretical maximum available power P3 of the power battery, that is, P3 = min(P1, P2). If the state of charge (SOC) is greater than the preset value, then take the first table-looked-up power P1 as the maximum available discharge power P3 of the power battery, that is, P3 = P1.

[0065] In theory, when the state of charge (SOC) of a battery is lower than a calibrated threshold (usually 10%), the battery should stop discharging. If it continues to discharge, it is over-discharging. In the existing over-discharge calculation methods (Method 2 or Method 1) of batteries, two variables are used to calculate the theoretical maximum available power P3, with relatively low accuracy, which is likely to cause over-discharge of the battery. It should be noted that when calculating the power of existing power batteries, the battery temperature, the lowest single-cell voltage, and the state of charge (SOC) are often not taken into account, and the state of charge (SOC) is not differentiated, making it difficult to accurately obtain the discharge power of the power battery and extremely likely to generate over-discharge risks. Over-discharge of the battery may cause damage to the active substances of the battery electrodes, loss of reaction ability, and shortening of the battery life.

[0066] In the power calculation method of the embodiment of the present application, a preset value is compared with the state of charge (SOC), so that at different states of charge (SOC), the value of the theoretical maximum available power P3 of the power battery is different, which not only reduces the risk of over-discharge of the battery caused by insufficient accuracy of the state of charge (SOC), but also makes the theoretical maximum available power P3 take into account multiple variable factors, improves the accuracy of the theoretical maximum available power P3, and further improves the reliability of the power battery.

[0067] To better understand the power calculation method of the embodiment of the present application, each step in the power calculation method will be described in detail below.

[0068] S1. Obtain the state of charge (SOC), battery temperature, and lowest single-cell voltage of the power battery.

[0069] Specifically, calculate the state of charge (SOC) of the power battery, and detect the battery temperature and the lowest single-cell voltage of the power battery. For example, obtain the state of charge (SOC), battery temperature, and lowest single-cell voltage of the power battery through the information acquisition module 110.

[0070] In an embodiment, the step of S1. Obtain the state of charge (SOC), battery temperature, and lowest single-cell voltage of the power battery specifically includes:

[0071] S11. Check the state of the power battery;

[0072] S12. If the power battery is in the discharge mode, obtain the state of charge (SOC), battery temperature, and lowest single-cell voltage of the power battery.

[0073] Specifically, check the state of the power battery to know whether the power battery is in the discharge state or the charge state. If the power battery is in the discharge mode, obtain the state of charge (SOC), battery temperature, and lowest single-cell voltage of the power battery through the information acquisition module 110.

[0074] For example, determine whether the power battery is in the discharge mode according to the current direction of the power battery. If the power battery is in the discharge mode, enter step S12; otherwise, return to S11, so as to perform discharge protection on the power battery and improve the safety and reliability of the power battery.

[0075] S2. According to the state of charge (SOC) and the battery temperature, look up the corresponding first look-up power from a pre-stored discharge power table.

[0076] Specifically, by measuring the discharge power at different states of charge (SOC) and different battery temperatures, a two-dimensional discharge power table 1 is plotted and stored. When performing protection calculation on the over-discharge power, the corresponding first look-up power P1 is looked up from the pre-stored two-dimensional discharge power table 1 according to the state of charge (SOC) and the battery temperature.

[0077] In one embodiment, as Figure 2 shown, the battery temperature includes the highest cell temperature T1 and the lowest cell temperature T2. The step of S2 of looking up the corresponding first look-up power from the pre-stored discharge power table according to the state of charge (SOC) and the battery temperature specifically includes:

[0078] S21. According to the state of charge (SOC) and the highest cell temperature, look up the corresponding third look-up power from the pre-stored discharge power table;

[0079] S22. According to the state of charge (SOC) and the lowest cell temperature, look up the corresponding fourth look-up power from the pre-stored discharge power table;

[0080] S23. Determine the smaller of the third look-up power and the fourth look-up power as the first look-up power.

[0081] Specifically, the battery temperature includes the highest cell temperature T1 and the lowest cell temperature T2. The highest cell temperature T1 and the lowest cell temperature T2 of the power battery are detected. The corresponding third look-up power P11 is looked up from the pre-stored two-dimensional discharge power table 1 according to the state of charge (SOC) and the highest cell temperature T1, and the corresponding fourth look-up power P12 is looked up from the pre-stored two-dimensional discharge power table 1 according to the state of charge (SOC) and the lowest cell temperature T2.

[0082] Compare the third look-up table power P11 with the fourth look-up table power P12, and determine the smaller of the third look-up table power P11 and the fourth look-up table power P12 as the first look-up table power P1, that is, P1 = min(P11, P12). Since the highest single cell temperature T1 and the lowest single cell temperature T2 are used in the process of looking up the table according to the state of charge SOC and the battery temperature, and the power value is found based on the highest single cell temperature T1, the lowest single cell temperature T2 and the state of charge SOC, and the smaller of them is determined as the corresponding first look-up table power P1, so as to further protect the power battery and take into account the influence of the highest single cell temperature T1, the lowest single cell temperature T2 and the state of charge SOC.

[0083] S3. Look up the corresponding second look-up table power from the pre-stored discharge power table according to the battery temperature and the lowest single cell voltage.

[0084] Specifically, by measuring the lowest single cell voltage and the discharge power at different battery temperatures, a two-dimensional discharge power table 2 is plotted and stored. When performing over-discharge power protection calculation, look up the corresponding second look-up table power P2 from the pre-stored two-dimensional discharge power table 2 according to the battery temperature and the lowest single cell voltage.

[0085] In one embodiment, as Figure 3 shown, the battery temperature includes the highest single cell temperature T1 and the lowest single cell temperature T2. The step of S3. Looking up the corresponding second look-up table power from the pre-stored discharge power table according to the battery temperature and the lowest single cell voltage specifically includes:

[0086] S31. Look up the corresponding fifth look-up table power from the pre-stored discharge power table according to the lowest single cell voltage and the highest single cell temperature;

[0087] S32. Look up the corresponding sixth look-up table power from the pre-stored discharge power table according to the lowest single cell voltage and the lowest single cell temperature;

[0088] S33. Determine the smaller of the fifth look-up table power and the sixth look-up table power as the second look-up table power.

[0089] Specifically, detect the highest single cell temperature T1 and the lowest single cell temperature T2 of the power battery. Look up the corresponding fifth look-up table power P21 from the pre-stored two-dimensional discharge power table 2 according to the lowest single cell voltage and the highest single cell temperature T1, and look up the corresponding sixth look-up table power P22 from the pre-stored two-dimensional discharge power table 2 according to the lowest single cell voltage and the lowest single cell temperature T2.

[0090] Compare the fifth look-up table power P21 with the sixth look-up table power P22, and determine the smaller of the fifth look-up table power P21 and the sixth look-up table power P22 as the second look-up table power P2, that is, P2 = min(P21, P22). Since the highest cell temperature T1 and the lowest cell temperature T2 are used in the process of looking up the table according to the lowest cell voltage and the battery temperature, and the power value is found based on the highest cell temperature T1, the lowest cell temperature T2, and the lowest cell voltage, and the smaller of them is determined to be the corresponding second look-up table power P2, so as to further protect the power battery and take into account the influence of the highest cell temperature T1, the lowest cell temperature T2, and the lowest cell voltage.

[0091] S4. If the state of charge SOC is less than or equal to the preset value, then determine the smaller of the first look-up table power and the second look-up table power as the theoretical maximum available power of the power battery. If the state of charge SOC is greater than the preset value, then use the first look-up table power as the maximum available discharge power P3 of the power battery.

[0092] Specifically, detect the state of charge SOC and compare the state of charge SOC with the preset value. If the state of charge SOC is less than or equal to the preset value, then determine the smaller of the first look-up table power P1 and the second look-up table power P2 as the theoretical maximum available power P3 of the power battery, that is, P3 = min(P1, P2). If the state of charge SOC is greater than the preset value, then use the first look-up table power P1 as the maximum available discharge power P3 of the power battery, that is, P3 = P1. For example, the state of charge SOC is in the low SOC stage and the medium-high SOC stage.

[0093] It should be noted that when calculating the power of the existing power battery, the state of charge SOC in the low SOC stage or the medium-high and low SOC stages is not distinguished, and it is difficult to accurately obtain the discharge power of the power battery. On the other hand, when looking up the power in the discharge power two-dimensional table at present, it is generally based on voltage and temperature, and does not involve considering the highest cell temperature T1, the lowest cell temperature T2, the lowest cell voltage, and the state of charge SOC in layers. However, in the embodiment of the present application, the state of charge SOC is processed in segments, and at each different state of charge SOC, the determined value of the maximum available discharge power P3 of the power battery is different, so as to better protect the power battery from discharging.

[0094] In one embodiment, as Figure 4 shown, when the power battery is in a fault state, after the step of S4. If the state of charge SOC is less than or equal to the preset value, then determine the smaller of the first look-up table power and the second look-up table power as the theoretical maximum available power P3 of the power battery, the power calculation method further includes:

[0095] S5. Detect the fault of the power battery and determine the fault level;

[0096] S6. Look up the corresponding limit power P4 from the pre-stored discharge power table according to the fault level;

[0097] S7. If the limit power is greater than or equal to the theoretical maximum available power, determine the theoretical maximum available power as the maximum fault available power P5 of the power battery in the fault state. If the limit power P4 is less than the theoretical maximum available power P3, the value of the maximum fault available power of the power battery in the fault state decreases linearly from the theoretical maximum available power P3 to the limit power P4.

[0098] Specifically, detect the current fault of the power battery, classify the fault level, and determine the fault level where the power battery is located. Limit the theoretical maximum available power P3 according to different fault levels. If there is no fault, determine the theoretical maximum available power P3 as the maximum fault available power P5 of the power battery in the fault state, that is, P5 = P3. Look up the corresponding limit power P4 from the pre-stored discharge power table according to the fault level. If there is no fault, determine the smaller of the first look-up power P1 and the second look-up power P2 as the theoretical maximum available power P3 of the power battery, that is, the maximum available discharge power P3 = min(P1, P2).

[0099] When the fault of the power battery is a first-level fault, look up the limit power P4, and compare the limit power P4 with the maximum available discharge power P3. If the limit power P4 is greater than or equal to the maximum available discharge power P3, determine the maximum available discharge power P3 as the maximum fault available power P5 of the power battery in the fault state, that is, P4 ≥ P3, then P5 = P3. It should be noted that the above is only an example with the fault of the power battery being a first-level fault, and it is not a limitation on the power calculation method of the embodiments of the present application. The fault of the power battery can also be a second-level fault, a third-level fault, a fourth-level fault, etc. Look up the corresponding limit power P4 according to the corresponding fault level.

[0100] In an embodiment, when the limit power P4 is less than the theoretical maximum available power P3, the maximum fault available power P5 of the power battery in the fault state, the theoretical maximum available power P3, and the limit power P4 satisfy the relationship:

[0101] where t is the time elapsed after the power battery fails, and N is a constant coefficient.

[0102] Specifically, when the limit power P4 < P3, Where t is the time after the fault occurs, N is a constant coefficient (t / N ≤ 1), and when t > N, P5 = P4. For example, when the fault of the power battery is a first-level fault, during the period from 20 kw to 10 kw within 10 s, the maximum available fault power P5 decreases from 19 kw, 18 kw, 17 kw to 10 kw, rather than suddenly dropping to 10 kw. A sharp drop is likely to cause short-term power overlimit and a significant reduction in power.

[0103] To better understand the power calculation method of the power battery in the embodiments of the present application, the following will be specifically described in combination with the actual calculation process.

[0104] Step 1: Determine whether the power battery is in the discharge mode according to the current direction. If the power battery is in the discharge mode, go to Step 2; otherwise, return to Step 1.

[0105] Step 2: Calculate the state of charge SOC of the power battery.

[0106] Step 3: Detect the battery temperature of the power battery, where the battery temperature includes the highest single-cell temperature T1 and the lowest single-cell temperature T2 of the battery.

[0107] Step 4: Look up the third table-looked-up power P11 corresponding to the state of charge SOC and the highest single-cell temperature T1 from the pre-stored discharge power table 1, look up the fourth table-looked-up power P12 corresponding to the SOC and the highest single-cell temperature T2 from the pre-stored discharge power table, and determine the smaller of the third table-looked-up power P11 and the fourth table-looked-up power P12 as the first table-looked-up power P1, that is, P1 = min(P11, P12).

[0108] Step 5: Detect the lowest single-cell voltage of the power battery.

[0109] Step 6: Look up the fifth table-looked-up power P21 corresponding to the lowest single-cell voltage and the highest single-cell temperature T1 from the pre-stored discharge power table 2, look up the sixth table-looked-up power P22 corresponding to the lowest single-cell voltage and the highest single-cell temperature T2 from the pre-stored discharge power table 2, and determine the smaller of the fifth table-looked-up power P21 and the sixth table-looked-up power P22 as the second table-looked-up power P1, that is, P2 = min(P21, P22). It should be noted that the discharge power table 1 is different from the discharge power table 2, and the variables used in the table-lookup process are different.

[0110] Step 7: Determine the state of charge (SOC) of the power battery. If the SOC is greater than the preset value SOC1, then use the first look-up table power P1 as the maximum available discharge power P3 of the power battery, that is, P3 = P1. If the SOC is less than or equal to the preset value SOC1, determine the smaller value between the first look-up table power P1 and the second look-up table power P2 as the theoretical maximum available power P3 of the power battery, that is, the maximum available discharge power P3 = min(P1, P2).

[0111] Step 8, Detect the current faults of the power battery, classify the fault levels, and limit the maximum allowable discharge power P3 according to different fault levels. If there is no fault, determine the smaller value between the first look-up table power P1 and the second look-up table power P2 as the theoretical maximum available power P3 of the power battery, that is, the maximum available discharge power P3 = min(P1, P2).

[0112] Specifically, when the fault of the power battery is a first-level fault, look up the table to obtain the limit power P4, and compare the limit power P4 with the maximum available discharge power P3. If the limit power P4 is greater than or equal to the maximum available discharge power P3, then determine the maximum available discharge power P3 as the maximum fault available power P5 of the power battery in the fault state, that is, P4 ≥ P3, then P5 = P3. For example, before the fault occurs, the maximum available discharge power P3 is 20kw, and the allowable limit power P4 after the fault occurs is 10kw. The value of the maximum fault available power P5 of the power battery in the fault state is between the theoretical maximum available power P3 and the limit power P4. In particular, if the limit power P4 is less than the maximum available discharge power P3, the maximum fault available power P5, the theoretical maximum available power P3, and the limit power P4 of the power battery in the fault state satisfy the relationship: where t is the time after the fault occurs, and N is a constant coefficient (t / N ≤ 1). When t > N, P5 = P4. For example, during the period from 20kw to 10kw within 10s, the maximum fault available power P5 decreases from 19kw, 18kw, 17kw to 10kw, rather than suddenly dropping to 10kw. A steep drop is likely to cause short-term power overlimit and a significant reduction in power.

[0113] It should be noted that in the power calculation of the power battery in the embodiment of the present application, in the medium and high SOC stages, look up in the discharge power table generated according to the state of charge SOC and the battery temperature to obtain the first discharge power P1. In the low SOC stage, look up in the discharge power table generated according to the lowest single-cell voltage and the battery temperature to obtain the second discharge power P2. Determine the smaller of the second discharge power P2 and the first discharge power P1 as the maximum available discharge power P3. In the full-range SOC stage, detect and classify different faults that occur in the vehicle, and limit the table-lookup power according to different fault levels to improve the usage efficiency of the batteries in the power battery, meet the vehicle power requirements, and avoid over-discharging of the batteries in the power battery.

[0114] As Figure 5 shown, the embodiment of the present application also provides a power calculation system 100 for a power battery, including an information acquisition module 110, a power lookup module 120, and a power calculation module 130. Among them, the information acquisition module 110 is used to acquire the state of charge SOC, the battery temperature, and the lowest single-cell voltage of the power battery. The power lookup module 120 is used to look up the corresponding first table-lookup power P1 from the pre-stored discharge power table according to the state of charge SOC and the battery temperature, and look up the corresponding second table-lookup power P2 from the pre-stored discharge power table according to the battery temperature and the lowest single-cell voltage. The power calculation module 130 is used to compare the state of charge SOC with a preset value and determine the theoretical maximum available power P3 of the power battery.

[0115] Specifically, the information acquisition module 110 calculates the state of charge SOC of the power battery, detects the highest single-cell temperature T1 and the lowest single-cell temperature T2 of the battery. According to the state of charge SOC and the battery temperature, the power lookup module 120 looks up the corresponding third table-lookup power P11 from the pre-stored discharge power table for the state of charge SOC and the highest single-cell temperature T1. The power lookup module 120 looks up the corresponding fourth table-lookup power P12 from the pre-stored discharge power table for the SOC and the highest single-cell temperature T2.

[0116] The information acquisition module 110 also detects the lowest single-cell voltage of the battery. The power lookup module 120 looks up the corresponding fifth table-lookup power P21 from the pre-stored discharge power table for the lowest single-cell voltage and the highest single-cell temperature T1. The power lookup module 120 looks up the corresponding sixth table-lookup power P22 from the pre-stored discharge power table 2 for the lowest single-cell voltage and the highest single-cell temperature T2.

[0117] The power calculation module 130 compares the state of charge (SOC) with a preset value and determines the theoretical maximum available power P3 of the power battery. For example, the power calculation module 130 determines the smaller of the fifth look-up table power P21 and the sixth look-up table power P22 as the second look-up table power P1, that is, P2 = min(P21, P22). The power calculation module 130 determines the smaller of the third look-up table power P11 and the fourth look-up table power P12 as the first look-up table power P1, that is, P1 = min(P11, P12).

[0118] The power calculation module 130 compares the state of charge (SOC) with a preset value. If the state of charge (SOC) is greater than the preset value SOC1, the first look-up table power P1 is used as the maximum available discharge power P3 of the power battery, that is, P3 = P1. If the state of charge (SOC) is less than or equal to the preset value SOC1, the smaller of the first look-up table power P1 and the second look-up table power P2 is determined as the theoretical maximum available power P3 of the power battery, that is, the maximum available discharge power P3 = min(P1, P2).

[0119] In one embodiment, the power calculation system further includes a test module and a generation module. The test module is used to test the discharge capacity of the power battery under different states of charge (SOC), different battery temperatures, and different single-cell voltages. The generation module is connected to the test module and is used to transform the test results into a discharge power table based on the state of charge (SOC), battery temperature, and single-cell voltage. Specifically, the test module tests the power battery under different states of charge (SOC) and different battery temperatures to generate test results. The generation module is connected to the test module and generates a two-dimensional discharge power table 1 of the power battery based on the state of charge (SOC) and battery temperature.

[0120] The test module also tests the power battery under different battery temperatures and different minimum single-cell voltages to generate test results. The generation module generates a two-dimensional discharge power table 2 of the power battery based on the battery temperature and the minimum single-cell voltage, so as to facilitate directly looking up the two-dimensional discharge power table 1 and the two-dimensional discharge power table 2 in the subsequent calculation process. It should be noted that the two-dimensional discharge power table 1 and the two-dimensional discharge power table 2 can be combined and recorded into a whole table for storage, or recorded into two different tables for storage.

[0121] In one embodiment, the power calculation system further includes a fault detection module, which is used to detect faults of the power battery. Specifically, the fault detection module detects faults of the power battery and classifies the faults of the power battery to find the limiting power P4 in the subsequent calculation process.

[0122] The present application also provides an electric vehicle, including a power calculation system 100 of a power battery and a driving device, wherein the driving device is connected to the power calculation system.

[0123] Specifically, the power calculation system 100 of the power battery combines the highest single-cell temperature T1 and the lowest single-cell temperature T2, and the state of charge SOC, and obtains the lowest single-cell voltage through look-up tables to obtain the first look-up power P1 and the second look-up power P2, and determines the smaller of the first look-up power P1 and the second look-up power P2 as the theoretical maximum available power P3 of the power battery, P3 = min(P1, P2). The driving device operates at the theoretical maximum available power P3, enabling the electric vehicle to travel. Particularly, in the power calculation of the power battery, the state of charge SOC is compared with a preset value, and the state of charge SOC is divided into different SOC stages. In the medium and high SOC stages, look up in the discharge power table generated according to the state of charge SOC and the battery temperature to obtain the first discharge power P1. In the low SOC stage, look up in the discharge power table generated according to the lowest single-cell voltage and the battery temperature to obtain the second discharge power P2, and determine the smaller of the second discharge power P2 and the first discharge power P1 as the maximum available discharge power P3. In the full-range SOC stage, different faults occurring in the vehicle are detected and classified, and the look-up power is restricted according to different fault levels to improve the utilization efficiency of the batteries in the power battery, meet the power requirements of the whole vehicle, and avoid over-discharge of the batteries in the power battery.

[0124] For the convenience of description, when describing the above modules, various units are described according to their functions. Of course, in the present application, the functions of each module can be implemented in the same or multiple software and / or hardware.

[0125] The arrangement of the method described in combination with the embodiments disclosed in the present application can be directly implemented by hardware, the above various modules executed by a processor, or a combination of the two. The various modules can be placed in a random access memory (RAM), memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, register, hard disk, removable disk, CD-ROM, or any other form of storage medium well-known in the technical field.

[0126] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions required to be protected by the present application.

Claims

1. A method for calculating the power of a power battery, characterized in that, Including: Obtain the state of charge (SOC), battery temperature, and the lowest single-cell voltage of the power battery; According to the state of charge (SOC) and the battery temperature, look up the corresponding first table-lookup power from a pre-stored discharge power table; According to the battery temperature and the lowest single-cell voltage, look up the corresponding second table-lookup power from the pre-stored discharge power table; If the state of charge (SOC) is less than or equal to a preset value, determine the smaller value between the first table-lookup power and the second table-lookup power as the theoretical maximum available power P3 of the power battery. If the state of charge (SOC) is greater than the preset value, use the first table-lookup power as the maximum available discharge power P3 of the power battery; When the power battery is in a fault state, after the step of determining the smaller value between the first table-lookup power and the second table-lookup power as the theoretical maximum available power P3 of the power battery if the state of charge (SOC) is less than or equal to the preset value, the power calculation method further includes: Detect the fault of the power battery and determine the fault level; According to the fault level, look up the corresponding limiting power P4 from the pre-stored discharge power table; If the limiting power P4 is greater than or equal to the theoretical maximum available power P3, determine the theoretical maximum available power P3 as the maximum fault available power P5 of the power battery in the fault state. If the limiting power P4 is less than the theoretical maximum available power P3, the maximum fault available power P5 of the power battery in the fault state linearly decreases from the theoretical maximum available power P3 to the limiting power P4; When the limiting power P4 is less than the theoretical maximum available power P3, the maximum fault available power P5 of the power battery in the fault state, the theoretical maximum available power P3, and the limiting power P4 satisfy the relationship: , where t is the time elapsed after the failure of the power battery, and N is a constant coefficient.

2. The power calculation method according to claim 1, wherein The battery temperature includes the highest single-cell temperature and the lowest single-cell temperature. The step of looking up the corresponding first table-lookup power from the pre-stored discharge power table according to the state of charge (SOC) and the battery temperature specifically includes: Look up the corresponding third table-lookup power from the pre-stored discharge power table according to the state of charge (SOC) and the highest single-cell temperature; Look up the corresponding fourth table-lookup power from the pre-stored discharge power table according to the state of charge (SOC) and the lowest single-cell temperature; Determine the smaller value between the third table-lookup power and the fourth table-lookup power as the first table-lookup power.

3. The power calculation method according to claim 1, wherein The battery temperature includes the highest single-cell temperature and the lowest single-cell temperature. The step of looking up the corresponding second table-lookup power from the pre-stored discharge power table according to the battery temperature and the lowest single-cell voltage specifically includes: Look up the corresponding fifth table-lookup power from the pre-stored discharge power table according to the lowest single-cell voltage and the highest single-cell temperature; Look up the corresponding sixth table-lookup power from the pre-stored discharge power table according to the lowest single-cell voltage and the lowest single-cell temperature; Determine the smaller value between the fifth table-lookup power and the sixth table-lookup power as the second table-lookup power.

4. The power calculation method according to claim 1, wherein Steps for obtaining the state of charge (SOC), battery temperature, and minimum cell voltage of a power battery, specifically including: Checking the state of the power battery; If the power battery is in a discharge mode, obtaining the state of charge (SOC), battery temperature, and minimum cell voltage of the power battery.

5. A power calculation system for a power battery, which is used to implement the power calculation method as described in claim 1, characterized in that Including: An information acquisition module, a power lookup module, and a power calculation module; wherein, The information acquisition module is used to obtain the state of charge (SOC), battery temperature, and minimum cell voltage of the power battery; The power lookup module is used to look up the corresponding first looked-up power from a pre-stored discharge power table according to the state of charge (SOC) and the battery temperature, and look up the corresponding second looked-up power from the pre-stored discharge power table according to the battery temperature and the minimum cell voltage; The power calculation module is used to compare the state of charge (SOC) with a preset value and determine the theoretical maximum available power P3 of the power battery.

6. The power calculation system according to claim 5, wherein The power calculation system further includes a test module and a generation module, wherein, The test module is used to respectively test the discharge capacity of the power battery under different states of charge (SOC), different battery temperatures, and voltages of different single cells, and generate test results; and The generation module is connected to the test module, and the generation module is used to transform the test results to the power battery based on the state of charge (SOC), the battery temperature, and the voltage of the single cell to generate the discharge power table.

7. The power calculation system according to claim 5, characterized in that, The power calculation system further includes a fault detection module, and the fault detection module is used to detect faults of the power battery.

8. An electric vehicle, characterized in that, Including: The power calculation system of the power battery according to any one of claims 5 to 7; And A traveling device, connected to the power calculation system.

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