Battery SOC estimation method and device, battery management system and medium

Abstract

The embodiment of the invention provides a battery SOC estimation method and device, a battery management system and a medium. The method comprises the steps that the current battery state of a to-be-tested battery is determined; the current battery state comprises a charging state or a discharging state; determining a target estimation strategy corresponding to the current battery state; and performing SOC estimation on the battery to be measured based on the target estimation strategy. It can be known that different estimation strategies are set for the current battery state of the to-be-tested battery, so that the corresponding target estimation strategy can be determined according to the to-be-tested battery in the charging state or the discharging state to carry out SOC estimation. Therefore, the dependence on the path is considered during SOC estimation, so that the SOC estimation deviation caused by the path dependence problem is reduced, and the SOC estimation accuracy is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery SOC estimation method, device, battery management system and medium. Background Art

[0002] The state of charge (SOC) of a battery refers to the state of the remaining power in the battery. In order to achieve safe and reliable operation of electrical devices, real-time estimation of the battery SOC is particularly important. Since the battery SOC cannot be measured directly, it needs to be estimated through an estimation method. However, in the related art, although various SOC estimation methods have their own characteristics, the estimation accuracy of SOC is not ideal. How to provide an estimation method that can improve the accuracy of SOC estimation is a technical problem that needs to be solved urgently in this field. Summary of the invention

[0003] In view of the above problems, the embodiments of the present application provide a battery SOC estimation method, device, battery management system and medium, which can solve the technical problem of low SOC estimation accuracy.

[0004] In a first aspect, an embodiment of the present application provides a battery SOC estimation method, the method comprising:

[0005] Determine the current battery state of the battery to be tested; the current battery state includes a charging state or a discharging state;

[0006] Determining a target estimation strategy corresponding to the current battery state;

[0007] Based on the target estimation strategy, the SOC of the battery to be tested is estimated.

[0008] In the technical solution of the embodiment of the present application, different estimation strategies are set for the current battery state of the battery to be tested, so that the corresponding target estimation strategy can be determined according to the charging state or the discharging state of the battery to be tested to perform SOC estimation. Therefore, the dependence on the path is taken into account when estimating SOC, thereby reducing the SOC estimation deviation introduced by the path dependence problem and improving the accuracy of SOC estimation.

[0009] In some embodiments, the determination of the target estimation strategy corresponding to the current battery state includes: determining to use a mapping relationship corresponding to the current battery state for SOC estimation. By setting different mapping relationships for the current state of the battery to be tested, the SOC estimation can be performed based on the corresponding mapping relationship determined in the charging state or the discharging state of the battery to be tested. As a result, the dependence on the path is taken into account during SOC estimation, thereby reducing the SOC estimation deviation introduced by the path dependence problem and improving the accuracy of SOC estimation.

[0010] In some embodiments, before determining to use the mapping relationship corresponding to the current battery state for SOC estimation, it also includes: detecting the first duration of the current of the battery to be tested before a reverse change occurs; the reverse change is a change in the opposite direction of the current corresponding to the current battery state; determining that the first duration is greater than or equal to a first time threshold. By first determining that the first duration of the battery to be tested before a reverse change occurs in the current exceeds the first time threshold, the battery to be tested is allowed to stably operate on a mapping relationship corresponding to a certain battery state for a certain period of time. At this time, it can be considered that the battery to be tested maintains a charging state or a discharging state. After determining that the battery to be tested remains in a certain battery state, it is determined to use the mapping relationship corresponding to the battery state for SOC estimation, so that the battery to be tested will not fluctuate between mapping relationships corresponding to different battery states due to the hysteresis effect, thereby improving the accuracy of SOC estimation.

[0011] In some embodiments, the method further includes: if it is determined that the first duration is less than the first time threshold, determining that the target estimation strategy is the ampere-hour integration method. It can be seen that if the first duration is less than the first time threshold, it means that the battery to be tested is not maintained in a charging state or a discharging state. At this time, the battery to be tested does not stably operate on the mapping relationship corresponding to a certain battery state, and may fluctuate between the mapping relationships corresponding to different battery states. The ampere-hour integration method can better adapt to the SOC estimation when the battery fluctuates. Therefore, using the ampere-hour integration method to estimate the SOC can improve the accuracy of the SOC estimation of the battery when it fluctuates.

[0012] In some embodiments, the determination to use the mapping relationship corresponding to the current battery state for SOC estimation includes: if the current battery state is a charging state, determining to use the mapping relationship between the battery parameters of the charging segment and the SOC for SOC estimation; if the current battery state is a discharging state, determining to use the mapping relationship between the battery parameters of the discharging segment and the SOC for SOC estimation. By using each SOC measured when the battery is discharging and the corresponding battery parameters to establish a mapping relationship in the discharge state, and using each SOC measured when the battery is charging and the corresponding battery parameters to establish a mapping relationship in the charging state, when performing SOC estimation, the corresponding mapping relationship can be selected as the estimation strategy with reference to the current battery state of the battery, thereby taking into account the dependence on the path when estimating SOC, and improving the accuracy of SOC estimation.

[0013] In some embodiments, the battery parameters include model parameters of the equivalent circuit model and the open circuit voltage. It can be seen that when the battery to be tested is in a charging state or a discharging state, the mapping relationship between the model parameters of the equivalent circuit corresponding to the battery state and the SOC, as well as the mapping relationship between the open circuit voltage and the SOC, are used to dynamically estimate the SOC of the battery to be tested. The change in the SOC of the battery during charging and discharging is more dependent on the electrochemical characteristics inside the battery and is more in line with dynamic estimation rules. Therefore, using the model parameters of the equivalent circuit model and the open circuit voltage to dynamically estimate the SOC can improve the accuracy of SOC estimation.

[0014] In some embodiments, the determining to use the mapping relationship corresponding to the current battery state to perform SOC estimation includes: determining to use the mapping relationship corresponding to the current battery state in combination with a correction algorithm to perform SOC estimation. By introducing a correction algorithm, the SOC deviation caused during the battery charging and discharging process can be corrected, thereby improving the accuracy of SOC estimation.

[0015] In some embodiments, the battery state also includes a static state; the determination of the target estimation strategy corresponding to the current battery state includes: determining the historical battery state of the battery to be tested before the static state; determining to use the mapping relationship corresponding to the historical battery state for SOC estimation. It can be seen that when the battery to be tested is in a static state, even if the battery to be tested is not currently being charged or discharged, the corresponding mapping relationship is still selected to perform SOC estimation with reference to the historical battery state of the battery to be tested. This allows the SOC estimation to still take into account the path dependency in the static state, thereby improving the accuracy of SOC estimation.

[0016] In some embodiments, before determining the battery state of the battery to be tested in the history before the static state, it also includes: detecting a second duration of the battery to be tested in the static state; and determining that the second duration is greater than or equal to a second time threshold. By first determining that the second duration of the battery to be tested in the static state exceeds the second time threshold, it can be considered that the battery to be tested is stably maintained in the static state. Then, it is determined to use the mapping relationship corresponding to the battery state of the history before the static state to perform SOC estimation, so that the battery to be tested will not fluctuate between the mapping relationships corresponding to different historical battery states due to the hysteresis effect, thereby improving the accuracy of SOC estimation.

[0017] In some embodiments, the method further includes: if it is determined that the second duration is less than the second time threshold, determining that the target estimation strategy is a historically determined estimation strategy. It can be seen that if the second duration is less than the second time threshold, it means that the battery to be tested is not maintained in a static state. At this time, the battery to be tested may fluctuate between the mapping relationships corresponding to different historical battery states. At the same time, since the battery current is basically 0 in a static state, the ampere-hour integration method is not applicable to estimate the SOC. Therefore, it is proposed to continue to use the historically determined estimation strategy to continue SOC estimation, and then redetermine the target estimation strategy after the battery to be tested stabilizes or changes the battery state.

[0018] In some embodiments, the determination to use the mapping relationship corresponding to the historical battery state for SOC estimation includes: if the historical battery state is a charging state, determining to use the mapping relationship between the battery parameters of the charging segment and the SOC for SOC estimation; if the historical battery state is a discharging state, determining to use the mapping relationship between the battery parameters of the discharging segment and the SOC for SOC estimation. By using the various SOCs and corresponding battery parameters measured when the battery is discharging to establish a mapping relationship under the discharge state, and using the various SOCs and corresponding battery parameters measured when the battery is charging to establish a mapping relationship under the charging state, the battery to be tested can refer to the historical battery state to select the corresponding mapping relationship as the estimation strategy in the static state. The dependence of SOC on the path is also considered in the static state, which improves the accuracy of SOC estimation.

[0019] In some embodiments, the battery parameters include open circuit voltage. It can be seen that when the battery to be tested is in a static state, the mapping relationship between the open circuit voltage and SOC corresponding to the historical battery state is used to perform a static SOC estimation on the battery to be tested. Since the mapping relationship between the open circuit voltage and the SOC is measured when the battery is static, the SOC change law of the battery in a static state is more in line with the SOC-OCV mapping relationship. In other words, the SOC-OCV mapping relationship can better reflect the change of SOC in a static state, thereby improving the accuracy of SOC estimation.

[0020] In a second aspect, an embodiment of the present application provides a SOC estimation device, the device comprising:

[0021] A first determination module is used to determine the current battery state of the battery to be tested; the current battery state includes a charging state or a discharging state;

[0022] A strategy module, used to determine a target estimation strategy corresponding to the current battery state;

[0023] An estimation module is used to estimate the SOC of the battery to be tested based on the target estimation strategy.

[0024] In a third aspect, an embodiment of the present application provides a battery management system, the battery management system comprising:

[0025] processor;

[0026] a memory for storing processor-executable instructions;

[0027] Wherein, when the processor calls the executable instruction, it implements the operation of any method described in the first aspect.

[0028] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium having computer instructions stored thereon, wherein the computer instructions, when executed by a processor, implement the steps of any method described in the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 A flow chart of a battery SOC estimation method provided in an embodiment of the present application;

[0031] Figure 2 A schematic flow chart of a target estimation strategy determination process in a battery SOC estimation method provided in an embodiment of the present application;

[0032] Figure 3 A schematic flow chart of a target estimation strategy determination process in another battery SOC estimation method provided in an embodiment of the present application;

[0033] Figure 4 A schematic flow chart of a target estimation strategy determination process in another battery SOC estimation method provided in an embodiment of the present application;

[0034] Figure 5 A schematic flow chart of a target estimation strategy determination process in another battery SOC estimation method provided in an embodiment of the present application;

[0035] Figure 6 A schematic flow chart of a target estimation strategy determination process in another battery SOC estimation method provided in an embodiment of the present application;

[0036] Figure 7 The SOC-OCV curve diagram of the charging section and the discharging section provided in the embodiment of the present application;

[0037] Figure 8A schematic diagram of the structure of a second-order equivalent circuit model provided in an embodiment of the present application;

[0038] Fig. 9 A flowchart of another battery SOC estimation method provided in an embodiment of the present application;

[0039] Fig.10 A structural block diagram of a battery SOC estimation device provided in an embodiment of the present application;

[0040] Fig.11 A hardware structure diagram of a battery management system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0041] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0043] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0044] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0045] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0046] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0047] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0048] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0049] Batteries have a hysteresis effect. For example, the hysteresis effect of lithium iron phosphate batteries is particularly obvious. The hysteresis effect of the battery will cause the battery to exhibit different electrochemical characteristics when charging and discharging. From the perspective of SOC estimation, the hysteresis effect will cause the battery parameters presented by the same SOC value when the battery is charging to be different from the battery parameters presented when the battery is discharging. For example, the SOC-OCV (Open Circuit Voltage) curves obtained by testing under charging and discharging conditions do not overlap. That is, the SOC-OCV curve measured by "discharge + static" is different from the SOC-OCV curve measured by "charge + static", and it is particularly obvious in the platform section of the curve. The SOC-OCV curve is path (charging path or discharge path) dependent.

[0050] However, in the related art, the SOC-OCV curve used for SOC estimation is a single-value curve, that is, one SOC value corresponds to one OCV value, and the path dependence of the curve is not considered. Obviously, this will lead to a large error in SOC estimation, and the SOC deviation introduced by the curve may even reach 40%.

[0051] To this end, the embodiment of the present application provides a battery SOC estimation method, in which different estimation strategies are set for the current battery state of the battery to be tested. This allows the SOC estimation to be performed by determining the corresponding target estimation strategy according to the charging state or the discharging state of the battery to be tested. As a result, the dependence on the path is taken into account when estimating the SOC, thereby reducing the SOC estimation deviation introduced by the path dependence problem and improving the accuracy of the SOC estimation.

[0052] The battery disclosed in the embodiments of the present application may include but is not limited to batteries of other systems that also have a hysteresis effect, such as lithium iron phosphate batteries. The battery disclosed in the embodiments of the present application may be used, but is not limited to, in electrical devices such as vehicles, ships, or aircraft. Electrical devices that use batteries as power sources may include but are not limited to mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys may include fixed or mobile electric toys, for example, game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0053] According to some embodiments of the present application, Figure 1 As shown, a first aspect provides a method for estimating a battery SOC. The method can be applied to a battery management system (BMS), and includes steps 110 to 130.

[0054] Step 110: Determine the current battery status of the battery to be tested;

[0055] The current battery state includes a charging state or a discharging state;

[0056] Step 120: Determine a target estimation strategy corresponding to the current battery state;

[0057] Step 130: Based on the target estimation strategy, perform SOC estimation on the battery to be tested.

[0058] The battery state includes at least a charging state or a discharging state. The charging state refers to the state in which the battery is being charged; the discharging state refers to the state in which the battery is being discharged.

[0059] The estimation strategy is used to estimate the SOC of the battery to be tested. The estimation strategy may include multiple types. Exemplarily, the execution subject of this embodiment may pre-store multiple estimation strategies. When executing step 120, according to the current battery state of the battery to be tested, a target estimation strategy corresponding to the current battery state is determined from the multiple estimation strategies.

[0060] Thus, in this embodiment, different estimation strategies are set for the current battery state of the battery to be tested, so that the corresponding target estimation strategy can be determined according to the charging state or the discharging state of the battery to be tested to perform SOC estimation. Thus, the dependence on the path is taken into account when estimating SOC, thereby reducing the SOC estimation deviation introduced by the path dependence problem and improving the accuracy of SOC estimation.

[0061] Based on the above embodiment, determining the target estimation strategy corresponding to the current battery state in step 120 may specifically include:

[0062] Determine to use a mapping relationship corresponding to the current battery state to perform SOC estimation.

[0063] The mapping relationship may refer to a mapping relationship between a battery parameter and SOC. For example, the battery parameter may include one or more. The battery parameter may be directly measured or determined by other directly measurable parameters.

[0064] There may be multiple mapping relationships. Each mapping relationship corresponds to a different battery state. In other words, different mapping relationships correspond to different battery states. Thus, the mapping relationship corresponding to the current battery state may include: a mapping relationship between battery parameters and SOC in a charging state, and a mapping relationship between battery parameters and SOC in a discharging state.

[0065] Thus, after determining the current battery state, a mapping relationship corresponding to the current battery state can be selected. After obtaining the battery parameters, the SOC corresponding to the obtained battery parameters can be determined as the estimated SOC according to the selected mapping relationship, thereby completing the SOC estimation process.

[0066] In this embodiment, different mapping relationships are set for the current state of the battery to be tested, so that the SOC estimation can be performed according to the corresponding mapping relationship determined in the charging state or the discharging state of the battery to be tested. Therefore, the dependence on the path is taken into account when estimating the SOC, thereby reducing the SOC estimation deviation introduced by the path dependence problem and improving the accuracy of the SOC estimation.

[0067] Based on the above embodiment, before determining to use the mapping relationship corresponding to the current battery state to perform SOC estimation, the following steps may also be included: Figure 2 Steps 210 to 220 are shown.

[0068] Step 210: Detecting a first duration of the current of the battery to be tested before a reverse change occurs;

[0069] The reverse change is a change in the current direction opposite to that corresponding to the current battery state;

[0070] Step 220: Determine whether the first duration is greater than or equal to a first time threshold.

[0071] The battery state includes a charging state or a discharging state. In the charging state, the corresponding current direction is that the current flows into the battery. In the discharging state, the corresponding current direction is that the current flows out of the battery. It can be seen that the current direction corresponding to the charging state is opposite to the current direction corresponding to the discharging state.

[0072] When the battery to be tested is in a charging state, a reverse change in current may include the battery to be tested changing to a discharging state and discharging. Before the current of the battery to be tested changes reversely, it may maintain a charging state, or stop charging, that is, a static state. In this way, the first duration of the current of the battery to be tested before the reverse change includes the duration of the battery to be tested in a charging state and the duration in a static state. Exemplarily, the sum of the two durations is the first duration. That is, when the current battery state is a charging state, the first duration is the non-discharging time of the battery to be tested.

[0073] When the battery to be tested is in a discharge state, a reverse change in current may include the battery to be tested changing to a charging state and charging. Before the current of the battery to be tested changes reversely, it may maintain a discharge state, or stop charging, that is, a static state. In this way, the first duration of the current of the battery to be tested before the reverse change includes the duration of the battery to be tested in the discharge state and the duration in the static state. Exemplarily, the sum of the two durations is the first duration. That is, when the current battery state is a discharge state, the first duration is the non-charging time of the battery to be tested.

[0074] The first time threshold can be set by those skilled in the art according to actual needs. This application is not limited here. As a feasible example, the first time threshold can be set to a time of seconds, such as 10 seconds.

[0075] In this embodiment, it is first determined that the first duration of the battery under test before the current reversely changes exceeds the first time threshold, so that the battery under test works stably in a mapping relationship corresponding to a certain battery state for a certain period of time. At this time, it can be considered that the battery under test maintains a charging state or a discharging state. After determining that the battery under test maintains a certain battery state, it is determined to use the mapping relationship corresponding to the battery state to perform SOC estimation, so that the battery under test will not fluctuate between mapping relationships corresponding to different battery states due to hysteresis effects, thereby improving the accuracy of SOC estimation.

[0076] Based on the above embodiments, in some embodiments, the above method may further include the steps of:

[0077] If it is determined that the first duration is less than the first time threshold, the target estimation strategy is determined to be the ampere-hour integration method.

[0078] If the first duration is less than the first time threshold, it means that the current of the battery to be tested changes reversely before reaching the first time threshold.

[0079] In the charging state, before reaching the first time threshold, the battery to be tested changes to the discharging state and discharges. The sum of the duration of the battery to be tested in the charging state and the duration in the static state does not reach the first time threshold.

[0080] In the discharge state, before reaching the first time threshold, the battery to be tested changes to the charging state and is charged. The sum of the duration of the battery to be tested in the discharge state and the duration in the static state does not reach the first time threshold.

[0081] The ampere-hour integration method is a method for estimating the SOC by accumulating the total charge flowing into or out of the battery during the charging and discharging process. The relevant estimation process can be referred to the relevant technology, and this application will not expand on it here.

[0082] In this embodiment, if the first duration is less than the first time threshold, it means that the battery to be tested is not maintained in the charging state or the discharging state. At this time, the battery to be tested is not stably working on the mapping relationship corresponding to a certain battery state, and may fluctuate between the mapping relationships corresponding to different battery states. The ampere-hour integration method can better adapt to the SOC estimation when the battery fluctuates, so using the ampere-hour integration method to estimate the SOC can improve the accuracy of the SOC estimation of the battery when it fluctuates.

[0083] Based on any of the above embodiments, the step of determining to use the mapping relationship corresponding to the current battery state to estimate the SOC may specifically include: Figure 3 Steps 310 to 320 are shown.

[0084] Step 310: If the current battery state is a charging state, determine to use a mapping relationship between battery parameters and SOC in the charging section to perform SOC estimation;

[0085] Step 320: If the current battery state is a discharge state, determine to use a mapping relationship between the battery parameters of the discharge segment and the SOC to perform SOC estimation.

[0086] Among them, either step 310 or step 320 is performed.

[0087] As described above, the mapping relationship corresponding to the current battery state may include: a mapping relationship between a battery parameter and SOC in a charging state, and a mapping relationship between a battery parameter and SOC in a discharging state.

[0088] For example, the mapping relationship between the battery parameters and the SOC in the charging state may include: the mapping relationship between the battery parameters and the SOC in the charging section. The so-called battery parameters in the charging section refer to the battery parameters measured when the battery is subjected to a charging test.

[0089] Similarly, the mapping relationship between the battery parameters and the SOC in the discharge state may include: the mapping relationship between the battery parameters and the SOC in the discharge stage. The so-called battery parameters in the discharge stage refer to the battery parameters measured when the battery is subjected to a discharge test.

[0090] Optionally, the mapping relationship may be stored and presented in the form of table items or curves.

[0091] Optionally, the mapping relationship may be a functional relationship. Thus, each SOC and corresponding battery parameter measured in the battery charge and discharge test may be used to perform function fitting to obtain a functional relationship between the battery parameter and the SOC in the charge / discharge stage as the mapping relationship.

[0092] Exemplarily, after selecting the mapping relationship, the battery parameters may be obtained, such as testing the current battery parameters, and then the SOC corresponding to the current battery parameters is determined as the estimated SOC according to the selected mapping relationship, thereby completing the SOC estimation process.

[0093] In this embodiment, a mapping relationship under the discharge state is established using each SOC measured when the battery is discharging and the corresponding battery parameters, and a mapping relationship under the charging state is established using each SOC measured when the battery is charging and the corresponding battery parameters, so that when performing SOC estimation, the corresponding mapping relationship can be selected as the estimation strategy with reference to the current battery state of the battery, thereby taking into account the dependence on the path when estimating the SOC, thereby improving the accuracy of SOC estimation.

[0094] Based on the above embodiment, the battery parameters include model parameters of the equivalent circuit model and the open circuit voltage.

[0095] It can be seen that the battery parameters of the charging stage include: the model parameters of the equivalent circuit model of the charging stage, and the open circuit voltage of the charging stage, that is, the model parameters of the equivalent circuit model and the open circuit voltage obtained when the battery is charged.

[0096] The battery parameters of the discharge stage include: model parameters of the equivalent circuit model of the discharge stage, and the open circuit voltage of the discharge stage, that is, the model parameters of the equivalent circuit model and the open circuit voltage obtained when the battery is subjected to a discharge test.

[0097] In this way, the mapping relationships corresponding to different charging states include the mapping relationship between the model parameters and the SOC, and the mapping relationship between the open circuit voltage and the SOC.

[0098] Exemplarily, the equivalent circuit model may include a first-order equivalent circuit model, a multi-order equivalent circuit model, etc. Those skilled in the art may select any equivalent circuit model according to actual needs.

[0099] Exemplarily, the model parameters of the equivalent circuit model may be resistance and capacitance parameters.

[0100] Exemplarily, when the equivalent circuit model is a second-order equivalent circuit model, the model parameters (i.e., resistance and capacitance parameters) may include one or more of ohmic internal resistance, electrochemical polarization capacitance, electrochemical polarization internal resistance, concentration polarization capacitance, and concentration polarization resistance.

[0101] In this embodiment, when the battery to be tested is in a charging state or a discharging state, the mapping relationship between the model parameters of the equivalent circuit corresponding to the battery state and the SOC, and the mapping relationship between the open circuit voltage and the SOC are used to dynamically estimate the SOC of the battery to be tested. The change of the SOC of the battery during charging and discharging is more dependent on the electrochemical characteristics inside the battery and is more in line with the dynamic estimation rules. Therefore, the dynamic estimation of the SOC using the model parameters of the equivalent circuit model and the open circuit voltage can improve the estimation accuracy of the SOC.

[0102] On the basis of the above embodiment, if the battery parameters include the model parameters of the equivalent circuit model and the open circuit voltage, then the above step of determining to use the mapping relationship corresponding to the current battery state to perform SOC estimation may specifically include:

[0103] Determine to use a mapping relationship corresponding to the current battery state, and perform SOC estimation in combination with a correction algorithm.

[0104] Exemplarily, the correction algorithm may include various filtering algorithms, such as but not limited to Kalman filter, particle filter, etc.

[0105] If the current battery state is the charging state, then the SOC is estimated by using the mapping relationship corresponding to the current battery state in combination with the correction algorithm, that is, the mapping relationship between the model parameters of the equivalent circuit model of the charging segment and the SOC, and the mapping relationship between the open circuit voltage of the charging segment and the SOC are used, combined with the correction algorithm to collaboratively estimate the SOC.

[0106] If the current battery state is a discharge state, then the SOC is estimated by using the mapping relationship corresponding to the current battery state in combination with the correction algorithm, that is, the mapping relationship between the model parameters of the equivalent circuit model of the discharge segment and the SOC, and the mapping relationship between the open circuit voltage of the discharge segment and the SOC are used, combined with the correction algorithm to collaboratively estimate the SOC.

[0107] In this embodiment, by introducing a correction algorithm, the SOC deviation caused by the battery charging and discharging process can be corrected, thereby improving the accuracy of SOC estimation.

[0108] Based on the above embodiment, the current battery state of the battery to be tested may include a static state in addition to a charging state or a discharging state. Thus, the target estimation strategy corresponding to the current battery state determined in step 120 may specifically include: Figure 4 Steps 410 - 420 are shown.

[0109] Step 410: determining the battery status of the battery under test history before the static state;

[0110] Step 420: Determine to use a mapping relationship corresponding to the historical battery state to perform SOC estimation.

[0111] The static state refers to the state where the battery under test is neither charged nor discharged. In the static state, the battery capacity of the battery under test will not change due to charging or discharging behavior. The battery capacity remains basically unchanged.

[0112] Since the current battery state also includes the static state, a target estimation strategy corresponding to the static state may be determined in step 120. Specifically, the target estimation strategy corresponding to the static state refers to: using a mapping relationship corresponding to the historical battery state to perform SOC estimation. The historical battery state refers to the battery state that the battery to be tested has experienced historically before entering the static state.

[0113] Exemplarily, the historical battery state refers to the previous battery state before entering the static state.

[0114] It is understandable that the battery state includes a charging state, a discharging state and a static state. Before the battery to be tested enters the static state, the battery state it has experienced the last time may be a charging state or a discharging state. That is, when the current battery state is the static state, the historical battery state is a charging state or a discharging state.

[0115] It can be seen that if the current battery state is a static state, the previous battery state of the battery to be tested is referred to to determine the mapping relationship corresponding to the historical charging state or the historical discharging state to perform SOC estimation.

[0116] In this embodiment, when the battery to be tested is in a static state, even if the battery to be tested is not currently being charged or discharged, the corresponding mapping relationship is still selected to perform SOC estimation with reference to the historical battery state of the battery to be tested, so that the dependence of SOC estimation on the path is still considered in the static state, thereby improving the accuracy of SOC estimation.

[0117] Based on the above embodiment, before executing step 410 to determine the battery state of the battery to be tested before the static state, the following steps may also be included: Figure 5 Steps 510 - 520 are shown.

[0118] Step 510: Detecting a second duration of the battery under test in the static state;

[0119] Step 520: Determine whether the second duration is greater than or equal to a second time threshold.

[0120] The second time threshold may be the time required for the battery to be tested to reach stability. As a feasible example, the second time threshold may be set to several hours, such as 3 hours.

[0121] If the current battery state of the battery to be tested is the static state, the second duration of the static state is first detected. If it is determined that the second duration of the battery to be tested in the static state is not less than the second time threshold, it means that the battery to be tested has been stably in the static state. At this time, the target estimation strategy is determined according to the historical battery state.

[0122] In this embodiment, it is first determined that the second duration of the battery under test in the static state exceeds the second time threshold, at which time it can be considered that the battery under test is stably maintained in the static state. Then, it is determined to use the mapping relationship corresponding to the historical battery state before the static state to perform SOC estimation, so that the battery under test will not fluctuate between the mapping relationships corresponding to different historical battery states due to the hysteresis effect, thereby improving the accuracy of SOC estimation.

[0123] Based on the above embodiments, in some embodiments, the above method may further include the steps of:

[0124] If it is determined that the second duration is less than the second time threshold, the target estimation strategy is determined to be a historically determined estimation strategy.

[0125] The historically determined estimation strategy refers to a target estimation strategy determined for different battery states and / or different first durations in any of the above embodiments. For example, the historically determined estimation strategy may include one or more of using a mapping relationship between battery parameters and SOC in a discharge segment to estimate SOC, using a mapping relationship between battery parameters and SOC in a charging segment to estimate SOC, using a mapping relationship corresponding to the current battery state in combination with a correction algorithm to estimate SOC, and using an ampere-hour integration method to estimate SOC.

[0126] If the second duration is less than the second time threshold, it means that the battery to be tested has not yet been stably in a static state. At this time, the battery to be tested will fluctuate between different mapping relationships due to the hysteresis effect, so it is not suitable to use the mapping relationship corresponding to the historical battery state for SOC estimation. In this way, the historically determined estimation strategy continues to be used for SOC estimation. When the second duration reaches the second time threshold, the estimation strategy is changed to use the mapping relationship corresponding to the historical battery state for SOC estimation, thereby correcting the estimated value of SOC. Or before the second duration reaches the second time threshold, if the battery state of the battery to be tested changes from a static state to a charging state or a discharging state, the target estimation strategy corresponding to the battery state is adopted according to the method provided in the above embodiment to perform SOC estimation.

[0127] In this embodiment, if the second duration is less than the second time threshold, it means that the battery to be tested is not kept in a static state. At this time, the battery to be tested may fluctuate between the mapping relationships corresponding to different historical battery states. At the same time, since the battery current is basically 0 in a static state, the ampere-hour integration method is not applicable to estimate the SOC. Therefore, it is proposed to continue to estimate the SOC using the historically determined estimation strategy, and then redefine the target estimation strategy after the battery to be tested is stable or the battery state changes.

[0128] Based on any of the above embodiments, step 420 may specifically include: Figure 6 Steps 610 - 620 are shown.

[0129] Step 610: If the historical battery state is a charging state, determine to use a mapping relationship between the battery parameters of the charging stage and the SOC to perform SOC estimation;

[0130] Step 620: If the historical battery state is a discharge state, determine to use the mapping relationship between the battery parameters of the discharge segment and the SOC to perform SOC estimation.

[0131] Among them, either step 610 or step 620 is performed.

[0132] The mapping relationship corresponding to the historical battery state may include: a mapping relationship between a battery parameter and SOC in a charging state, and a mapping relationship between a battery parameter and SOC in a discharging state.

[0133] For example, the mapping relationship between the battery parameters and the SOC in the charging state may include: the mapping relationship between the battery parameters and the SOC in the charging section. The so-called battery parameters in the charging section refer to the battery parameters measured when the battery is subjected to a charging test.

[0134] Similarly, the mapping relationship between the battery parameters and the SOC in the discharge state may include: the mapping relationship between the battery parameters and the SOC in the discharge stage. The so-called battery parameters in the discharge stage refer to the battery parameters measured when the battery is subjected to a discharge test.

[0135] Exemplarily, after selecting the mapping relationship, the battery parameters may be obtained, such as testing the current battery parameters, and then the SOC corresponding to the current battery parameters is determined as the estimated SOC according to the selected mapping relationship, thereby completing the SOC estimation process.

[0136] In this embodiment, each SOC measured when the battery is discharged and the corresponding battery parameters are used to establish a mapping relationship in the discharge state, and each SOC measured when the battery is charged and the corresponding battery parameters are used to establish a mapping relationship in the charging state, so that the battery to be tested can refer to the historical battery state to select the corresponding mapping relationship as the estimation strategy in the static state. The dependence of SOC on the path is also considered in the static state, which improves the accuracy of SOC estimation.

[0137] Based on the above embodiment, the battery parameter includes the open circuit voltage.

[0138] It can be seen that the battery parameters of the charging stage include: the open circuit voltage of the charging stage, that is, the open circuit voltage measured when the battery is being charged.

[0139] The battery parameters of the discharge stage include: the open circuit voltage of the discharge stage, that is, the open circuit voltage measured when the battery is discharged.

[0140] In this way, the target estimation strategy corresponding to the static state includes the mapping relationship between the open circuit voltage and SOC in the charging segment when the historical battery state is the charging state, such as the SOC-OCV curve of the charging segment; and includes the mapping relationship between the open circuit voltage and SOC in the discharging segment when the historical battery state is the discharging state, such as the SOC-OCV curve of the discharging segment.

[0141] For example, when the current battery state is a static state, if the historical battery state is a charging state, the mapping relationship between the open circuit voltage of the charging section and the SOC is selected. The current open circuit voltage of the battery to be tested is tested. According to the mapping relationship between the open circuit voltage of the charging section and the SOC, and the current open circuit voltage, the corresponding SOC is determined to be the estimated SOC, thereby completing the SOC estimation process.

[0142] If the historical battery state is a discharge state, the mapping relationship between the open circuit voltage and SOC in the discharge stage is selected. The current open circuit voltage of the battery to be tested is tested. According to the mapping relationship between the open circuit voltage and SOC in the charging stage and the current open circuit voltage, the corresponding SOC is determined to be the estimated SOC, thereby completing the SOC estimation process.

[0143] In this embodiment, when the battery to be tested is in a static state, the mapping relationship between the open circuit voltage and SOC corresponding to the historical battery state is used to perform static SOC estimation on the battery to be tested. Since the mapping relationship between the open circuit voltage and SOC is measured when the battery is static, the SOC change law of the battery in a static state is more consistent with the SOC-OCV mapping relationship. In other words, the SOC-OCV mapping relationship can better reflect the change of SOC in a static state, thereby improving the accuracy of SOC estimation.

[0144] The following will introduce the process of establishing each mapping relationship.

[0145] The process of establishing the mapping relationship includes an initialization parameter testing phase and a battery parameter extraction phase.

[0146] In the initialization parameter test phase, the battery is discharged multiple times with a preset capacity. After each discharge of the preset capacity is completed and the battery reaches a steady state, the open circuit voltage of the battery is tested. In this way, each SOC and the corresponding open circuit voltage in the discharge section can be obtained.

[0147] Similarly, the battery is charged with a preset capacity for multiple times, and after each charging of the preset capacity is completed and the battery reaches a steady state, the open circuit voltage of the battery is tested. In this way, each SOC and the corresponding open circuit voltage in the charging stage can be obtained.

[0148] The embodiment of the present application does not limit the order in which the multiple constant current charges and multiple constant current discharges of the battery are performed.

[0149] In addition, during the initialization parameter test phase, the battery also undergoes a HPPC (Hybrid Pulse Power Characteristic) test, which is to perform a constant current discharge pulse on the battery and record the pulse waveform, wherein the pulse time is a preset time and the pulse discharge amplitude is a preset amplitude.

[0150] For example, the HPPC test can be performed after each constant current discharge and after the open circuit voltage of the test battery is completed. Thus, the pulse waveform corresponding to each SOC in the discharge section can be obtained. In this way, in the constant current discharge test, the number of HPPC tests is consistent with the number of constant current discharges.

[0151] For example, the HPPC test can be performed after each constant current charge and after the open circuit voltage of the battery is tested. Thus, the pulse waveform corresponding to each SOC in the charging section can be obtained. In this way, in the constant current charge test, the number of HPPC tests is consistent with the number of constant current charges.

[0152] After completing the initialization parameter testing phase, the battery parameter extraction phase begins.

[0153] In multiple constant current discharges of the battery, each SOC and the corresponding open circuit voltage in the discharge section can be obtained. Using each SOC and the corresponding open circuit voltage in the discharge section, the mapping relationship between the open circuit voltage and SOC in the discharge section can be obtained. Optionally, the mapping relationship can be a table item or a curve graph. For example, by interpolating each SOC and the corresponding open circuit voltage in the discharge section, a curve graph and a table item between the open circuit voltage and SOC in the discharge section are obtained. Optionally, the mapping relationship can be a functional relationship. For example, a function is fitted using each SOC and the corresponding open circuit voltage in the discharge section, and the functional relationship obtained is the mapping relationship.

[0154] Similarly, in multiple constant current charging of the battery, each SOC and the corresponding open circuit voltage in the charging section can be obtained. Using each SOC and the corresponding open circuit voltage in the charging section, the mapping relationship between the open circuit voltage and SOC in the charging section can be obtained. Optionally, the mapping relationship can be a table item or a curve graph. For example, by interpolating each SOC and the corresponding open circuit voltage in the charging section, a curve graph and a table item between the open circuit voltage and SOC in the charging section are obtained. Optionally, the mapping relationship can be a functional relationship. For example, a function is fitted using each SOC and the corresponding open circuit voltage in the charging section, and the functional relationship obtained is the mapping relationship.

[0155] In the HPPC test after each constant current discharge of the battery, each SOC and the corresponding pulse waveform in the discharge section can be obtained. By fitting the pulse waveform with an equivalent circuit model, various model parameters of the discharge section can be obtained. In this way, the mapping relationship between the SOC and one or more model parameters of the discharge section can be obtained.

[0156] Similarly, in the HPPC test after each constant current charging of the battery, each SOC and the corresponding pulse waveform in the charging stage can be obtained. By fitting the pulse waveform with an equivalent circuit model, a variety of model parameters of the charging stage can be fitted. In this way, the mapping relationship between the SOC and one or more model parameters of the charging stage can be obtained.

[0157] According to some embodiments of the present application, for a lithium iron phosphate battery, a mapping relationship between battery parameters corresponding to different battery states and SOC is generated through an initialization parameter testing phase and a battery parameter extraction phase.

[0158] The initialization parameter testing phase includes the following steps:

[0159] Step 1.1: Discharge the lithium iron phosphate battery at constant current and constant voltage.

[0160] According to the instruction manual of the corresponding model of lithium iron phosphate battery, discharge the battery to the discharge cut-off voltage with the allowable rated discharge current I1 recorded in the instruction manual. Then maintain the discharge cut-off voltage and continue to discharge until the current is less than 0.05C, so that the remaining capacity of the battery, that is, SOC, is 0. Control the battery temperature during discharge to prevent excessive temperature rise.

[0161] Step 1.2: Charge the lithium iron phosphate battery with constant current and constant voltage.

[0162] Charge the battery to the battery charging cut-off voltage with the rated charging current I2 as specified in the instruction manual. Then keep the charging cut-off voltage and continue charging until the current is less than 0.05C, so that the remaining capacity of the battery, i.e., SOC, is 100%. During charging, control the battery temperature so that it does not produce excessive temperature rise. And record the total charge Qmax of the charging process as the actual capacity of the battery.

[0163] Through steps 1.1 to 1.2, the activation of the lithium iron phosphate battery is achieved.

[0164] Step 1.3: Keep the temperature constant for 3 hours to wait for the battery to reach a steady state.

[0165] Step 1.4: Discharge the lithium iron phosphate battery at a constant current.

[0166] The battery is discharged at 20% of the rated discharge current I1, and the preset capacity is discharged to 5% Qmax, and then left to stand for 3 hours. After the battery reaches a steady state, the open circuit voltage OCV of the battery is recorded. The recorded OCV is the open circuit voltage of the discharge section mentioned above.

[0167] Step 1.5: Perform HPPC test on lithium iron phosphate battery.

[0168] The battery is subjected to a single constant current discharge pulse. The pulse time is a preset 20 seconds, the pulse discharge amplitude is a preset 0.3I1, and the corresponding pulse waveform is recorded. After the discharge pulse ends, wait for 1 minute. Then use a constant current charge of 0.1I1 for 1 minute to make up for the charge loss during the pulse discharge.

[0169] The above steps 1.4-1.5 are cycled 17 times. That is, in step 1.4, after each discharge of 5% Qmax and recording of the open circuit voltage OCV, step 1.5 is executed. After completing the recording of the pulse waveform and compensating for the charge loss of the pulse discharge, return to step 1.4 until steps 1.4-1.5 are cycled 17 times in total. After the cycle is executed 17 times, step 1.6 is executed.

[0170] Step 1.6: Discharge the lithium iron phosphate battery at constant current and constant voltage.

[0171] Discharge the battery at a voltage not lower than the minimum voltage allowed for operation, and keep the discharge amount at 5% Qmax unchanged. After discharge, let it stand for 3 hours, wait for the battery to reach a steady state, and record the battery open circuit voltage OCV at this time. The recorded OCV is the open circuit voltage of the discharge section mentioned above.

[0172] Then follow step 1.5 above.

[0173] The above steps 1.6 to 1.5 are cycled twice. That is, in step 1.6, after each discharge of 5% Qmax and recording of the open circuit voltage OCV, step 1.5 is executed. After completing the recording of the pulse waveform and compensating for the charge loss of the pulse discharge, return to step 1.6 until steps 1.6 to 1.5 are cycled twice in total.

[0174] In fact, steps 1.4 and 1.6 are multiple discharges of the lithium iron phosphate battery with a preset capacity. The preset capacity is 5% Qmax. After each discharge, the OCV is recorded when it is left to stand still until it reaches a steady state, and the open circuit voltage of the discharge section is obtained. It can be seen that if the discharge capacity is 5% Qmax each time, the SOC of the battery is 0 after 20 discharges. In the first 17 discharges, the method of step 1.4 is used to discharge the battery at a constant current. In the 18th-19th discharge, the method of step 1.6 is used to discharge the battery at a constant current-constant voltage to ensure that the SOC of the battery is 0 after completing step 1.6.

[0175] In addition, according to step 1.5, an HPPC test is performed after each 5% Qmax discharge. Since steps 1.4 and 1.6 are discharged 20 times in total, step 1.5 is also cycled 20 times to obtain the pulse waveform corresponding to each SOC in the discharge section.

[0176] Step 1.7: After 20 times of 5% Qmax discharge, let it stand for 3 hours and wait for the battery to reach a steady state.

[0177] Step 1.8: Charge the lithium iron phosphate battery with constant current.

[0178] The battery is discharged at 20% of the rated discharge current I2, and the preset capacity is discharged to 5% Qmax, and then left to stand for 3 hours. After the battery reaches a steady state, the open circuit voltage OCV of the battery is recorded. The recorded OCV is the open circuit voltage of the charging stage mentioned above.

[0179] Step 1.9: Perform HPPC test on lithium iron phosphate battery.

[0180] The battery is subjected to a single constant current discharge pulse. The pulse time is a preset 20 seconds, the pulse discharge amplitude is a preset 0.3I1, and the corresponding pulse waveform is recorded. After the discharge pulse ends, wait for 1 minute. Then use a constant current charge of 0.1I1 for 1 minute to make up for the charge loss during the pulse discharge.

[0181] The above steps 1.8-1.9 are cycled 17 times. That is, in step 1.8, after charging 5% Qmax and recording the open circuit voltage OCV, step 1.9 is executed. After completing the recording of the pulse waveform and compensating for the charge loss of the pulse discharge, return to step 1.8 until step 1.8-1.9 is cycled 17 times in total. After the cycle is executed 17 times, step 1.10 is executed.

[0182] Step 1.10: Charge the lithium iron phosphate battery with constant current and constant voltage.

[0183] The battery is charged at a voltage not higher than the minimum allowed operating voltage, and the charge capacity is kept constant at 5% Qmax. After discharge, the battery is left to stand for 3 hours until it reaches a steady state, and the open circuit voltage (OCV) of the battery is recorded. The recorded OCV is the open circuit voltage of the charging stage described above.

[0184] Follow up with step 1.9 above.

[0185] The above steps 1.10 to 1.9 are cycled twice. That is, in step 1.10, after charging 5% Qmax and recording the open circuit voltage OCV, step 1.9 is executed. After completing the recording of the pulse waveform and compensating for the charge loss of the pulse discharge, return to step 1.10 until steps 1.10 to 1.9 are cycled twice in total.

[0186] In fact, steps 1.8 and 1.10 are to charge the lithium iron phosphate battery with a preset capacity multiple times. The preset capacity is 5% Qmax. After each charge, the OCV is recorded when it is left to stand until steady state, and the open circuit voltage of the charging stage is obtained. It can be seen that if the charging capacity is 5% Qmax each time, the SOC of the battery is 100% after 20 charges. In the first 17 charges, the method of step 1.8 is used to charge the battery with constant current. In the 18th-19th charge, the method of step 1.10 is used to charge the battery with constant current-constant voltage to ensure that the SOC of the battery is 100% after completing step 1.10.

[0187] In addition, according to step 1.9, an HPPC test is performed after each 5% Qmax charge. Since steps 1.8 and 1.10 are charged 20 times in total, step 1.9 is also executed 20 times in a cycle to obtain the pulse waveform corresponding to each SOC in the charging stage.

[0188] The initialization parameter test phase is now complete. Then enter the battery parameter extraction phase, which includes the following steps:

[0189] Step 2.1: Based on the multiple discharge tests in steps 1.4 and 1.6, we can obtain the SOCs (i.e. 100%, 95%, 90%…0%) with a 5% interval from 100% to 0% and the corresponding open circuit voltage OCV1 in the discharge section. Thus, we can obtain a total of 20 scattered points (SOC, OCV1). By interpolating the scattered points, we can obtain the following: Figure 7 The SOC-OCV curve of the discharge section is shown.

[0190] According to the multiple charging tests in step 1.8 and step 1.10, each SOC at 5% intervals from 0-100% (i.e. 0%, 5%, 10%...100%) and the corresponding open circuit voltage OCV2 in the charging section can be obtained. Thus, a total of 20 scattered points (SOC, OCV2) can be obtained. By interpolating the scattered points, the following can be obtained: Figure 7 The SOC-OCV curve of the charging stage is shown.

[0191] from Figure 7 It can be seen from the two SOC-OCV curves that the OCV corresponding to the SOC in the charging section and the discharging section are different, especially in the platform section. This application establishes a mapping relationship between the SOC in the charging section and the discharging section and the open circuit voltage OCV, so that when estimating the SOC of the lithium iron phosphate battery, the charging and discharging path is introduced as a consideration, and the corresponding mapping relationship is selected for SOC estimation, thereby solving the problem of low SOC estimation accuracy caused by the hysteresis effect and improving the SOC estimation accuracy.

[0192] Step 2.1: According to the HPPC test in step 1.5, each SOC with an interval of 5% from 100% to 0% and the corresponding pulse waveform in the discharge section can be obtained. Figure 8 The second-order equivalent circuit model shown in the figure is used to fit the pulse waveform to obtain the model parameters of the discharge section, including the ohmic internal resistance R0, the electrochemical polarization capacitance C p , electrochemical polarization internal resistance R p , concentration polarization capacitance C e , and concentration polarization resistance R e .also, Figure 8 It also shows the battery's electromotive force E, electrochemical polarization internal resistance terminal voltage Up, concentration polarization internal resistance terminal voltage Ue, and terminal voltage U t .

[0193] According to the HPPC test in step 1.9, each SOC at an interval of 5% from 0-100% and the corresponding pulse waveform in the charging stage can be obtained. The second-order equivalent circuit model is selected to fit the pulse waveform, and the model parameters of the charging stage can be obtained, including ohmic internal resistance, electrochemical polarization capacitance, electrochemical polarization internal resistance, concentration polarization capacitance, and concentration polarization resistance.

[0194] Step 2.3: For each SOC and the corresponding model parameters in the discharge section, a curve diagram of the model parameters of the discharge section and the SOC can be obtained by interpolation as a mapping relationship, including: a mapping relationship between the ohmic internal resistance of the discharge section and the SOC, a mapping relationship between the electrochemical polarization capacitance of the discharge section and the SOC, a mapping relationship between the electrochemical polarization internal resistance of the discharge section and the SOC, a mapping relationship between the concentration polarization capacitance of the discharge section and the SOC, and a mapping relationship between the concentration polarization resistance of the discharge section and the SOC. One or more of the mapping relationships.

[0195] For each SOC and the corresponding model parameters in the charging section, a curve diagram of the model parameters of the charging section and the SOC can be obtained by interpolation as a mapping relationship, including: a mapping relationship between the ohmic internal resistance of the charging section and the SOC, a mapping relationship between the electrochemical polarization capacitance of the charging section and the SOC, a mapping relationship between the electrochemical polarization internal resistance of the charging section and the SOC, a mapping relationship between the concentration polarization capacitance of the charging section and the SOC, and a mapping relationship between the concentration polarization resistance of the charging section and the SOC.

[0196] The battery parameter extraction phase is now complete. The obtained mapping relationship can be stored in the BMS that is connected to the battery. Whenever SOC estimation is required, the corresponding mapping relationship can be read to perform SOC estimation. Specifically, the battery SOC estimation process may include the following: Fig. 9 Steps shown.

[0197] First, the current battery state of the lithium iron phosphate battery is determined (step 901). The current battery state may include a charging state, a discharging state, and a static state. Subsequently, a target estimation strategy corresponding to the current battery state may be selected.

[0198] Specifically, if the current battery state is a charging state, the first duration before the battery current changes in the opposite direction is detected (step 902). The reverse change of the current refers to a change in the direction opposite to the current corresponding to the current battery state. Then in the charging state, the reverse change of the current means that the battery is discharging. In this way, the first duration includes the duration of the battery in the charging state and the duration in the static state. That is, the first duration is the non-discharging time of the battery.

[0199] It is detected whether the first duration is greater than a first time threshold (step 903), for example, 10 seconds.

[0200] If the first duration is greater than the first time threshold, it means that the battery maintains the charging state, and the mapping relationship between the model parameters of the charging section and the SOC, and the mapping relationship between the open circuit voltage of the charging section and the SOC are used, combined with the particle filter as the target estimation strategy to collaboratively estimate the SOC (step 904). If the first duration is less than the first time threshold, it means that the battery does not stably maintain the charging state, and the ampere-hour integration method is used as the target estimation strategy to estimate the SOC (step 908).

[0201] If the current battery state is a discharge state, the first duration before the battery current reversely changes is detected (step 905). In the discharge state, the reverse change of the current means that the battery is charged. Thus, the first duration includes the duration of the battery in the discharge state and the duration in the static state. That is, the first duration is the non-charging time of the battery.

[0202] It is detected whether the first duration is greater than a first time threshold (step 906), such as 10 seconds.

[0203] If the first duration is greater than the first time threshold, it means that the battery maintains the discharge state, and the mapping relationship between the model parameters of the discharge segment and the SOC, and the mapping relationship between the open circuit voltage of the discharge segment and the SOC are used, combined with the particle filter as the target estimation strategy to collaboratively estimate the SOC (step 907). If the first duration is less than the first time threshold, it means that the battery does not stably maintain the discharge state, and the ampere-hour integration method is used as the target estimation strategy to estimate the SOC (step 908).

[0204] If the current battery state is the static state, then the second duration of the battery in the static state is detected (step 909), and it is determined whether the second duration is greater than a second time threshold (step 910), for example, 3 hours.

[0205] If the second duration is greater than the second time threshold, it means that the battery has remained in the static state, and the historical battery state of the battery is further determined (step 911). That is, the battery state of the battery before entering the static state. For example, the historical battery state can be a charging state or a discharging state.

[0206] If the historical battery state is a charging state, the SOC is estimated using the mapping relationship between the open circuit voltage and SOC in the charging phase (step 912). If the historical battery state is a discharging state, the SOC is estimated using the mapping relationship between the open circuit voltage and SOC in the discharging phase (step 913).

[0207] It can be seen that since the mapping relationship between open circuit voltage and SOC is established using the SOC and open circuit voltage recorded when the battery reaches a steady state, the mapping relationship between open circuit voltage and SOC is applicable to static SOC estimation when the battery remains in a static state. At the same time, the SOC estimated using the mapping relationship between open circuit voltage and SOC in a static state has a correction effect. That is, if there is an estimation error when using other estimation strategies before, then when the battery remains in a static state, the estimated value can be corrected by statically estimating the SOC, so that the SOC estimation can be calibrated regularly to maintain a certain accuracy.

[0208] In addition, if the second duration is less than the second time threshold, it means that the battery has not yet reached a steady state in the static state, and therefore the SOC is estimated using the historically determined estimation method (step 914 ).

[0209] It can be seen that in the embodiment of the present application, by considering the mapping relationship between the battery parameters and SOC of the charging section and the discharging section respectively, the refined modeling of the battery model is realized, and the lithium iron phosphate battery with hysteresis effect due to the use of a single value curve is avoided. The introduction of system errors when estimating the SOC. In addition, by setting the first time threshold and the second time threshold, the battery needs to meet the battery state for a period of time before taking the corresponding mapping relationship as the estimation strategy, avoiding the battery from fluctuating between the mapping relationships of different battery states. And because the filtering algorithm is introduced, the SOC estimation deviation caused during the operation can be corrected. In particular, the particle filtering algorithm is used, which does not require a linear system and has no requirements for the function form, so any interpolation algorithm can be used to estimate the battery parameters corresponding to each SOC.

[0210] The second aspect of the embodiment of the present application further provides a SOC estimation device, such as Fig.10 As shown, the estimation device 1000 includes:

[0211] The first determination module 1010 is used to determine the current battery state of the battery to be tested; the current battery state includes a charging state or a discharging state;

[0212] A strategy module 1020, configured to determine a target estimation strategy corresponding to the current battery state;

[0213] The estimation module 1030 is used to estimate the SOC of the battery to be tested based on the target estimation strategy.

[0214] In some embodiments, the policy module 1020 is specifically configured to:

[0215] Determine to use a mapping relationship corresponding to the current battery state to perform SOC estimation.

[0216] In some embodiments, the policy module 1020 is further configured to:

[0217] Detecting a first duration of the current of the battery to be tested before a reverse change occurs; the reverse change is a change in a direction opposite to the current corresponding to the current state of the battery;

[0218] It is determined that the first duration is greater than or equal to a first time threshold.

[0219] In some embodiments, the strategy module 1020 is further configured to: if it is determined that the first duration is less than the first time threshold, determine that the target estimation strategy is the ampere-hour integration method.

[0220] In some embodiments, the policy module 1020 is specifically configured to:

[0221] If the current battery state is a charging state, determine to use a mapping relationship between battery parameters in the charging section and SOC to estimate the SOC;

[0222] If the current battery state is a discharging state, it is determined to use a mapping relationship between the battery parameters of the discharging section and the SOC to perform SOC estimation.

[0223] In some embodiments, the battery parameters include model parameters of an equivalent circuit model and an open circuit voltage.

[0224] In some embodiments, the strategy module 1020 is specifically used to: determine to use a mapping relationship corresponding to the current battery state, and perform SOC estimation in combination with a correction algorithm.

[0225] In some embodiments, the battery state further includes a static state; the strategy module 1020 is further configured to:

[0226] Determining a historical battery state of the battery under test before the static state;

[0227] Determine to use a mapping relationship corresponding to the historical battery state to perform SOC estimation.

[0228] In some embodiments, the policy module 1020 is further configured to:

[0229] Detecting a second duration of the battery under test in the static state;

[0230] It is determined that the second duration is greater than or equal to a second time threshold.

[0231] In some embodiments, the policy module 1020 is further configured to:

[0232] If it is determined that the second duration is less than the second time threshold, the target estimation strategy is determined to be a historically determined estimation strategy.

[0233] In some embodiments, the policy module 1020 is specifically configured to:

[0234] If the historical battery state is a charging state, determining to use a mapping relationship between the battery parameters of the charging section and the SOC to perform SOC estimation;

[0235] If the historical battery state is a discharge state, it is determined to use a mapping relationship between the battery parameters of the discharge segment and the SOC to perform SOC estimation.

[0236] In some embodiments, the battery parameter includes an open circuit voltage.

[0237] The implementation process of the functions and effects of each module in the above-mentioned device is specifically described in the implementation process of the corresponding steps in the above-mentioned method, which will not be repeated here.

[0238] The third aspect of the present application also provides Fig.11 A schematic diagram of the structure of a battery management system is shown in FIG. Fig.11 At the hardware level, the BMS includes a processor, an internal bus, a network interface, a memory, and a non-volatile memory, and may also include hardware required for other services. The processor reads the corresponding computer program from the non-volatile memory into the memory and then runs it to implement a battery SOC estimation method described in any of the above embodiments.

[0239] The present application also provides a computer storage medium, which stores a computer program. When the computer program is executed by a processor, it can be used to execute a battery SOC estimation method described in any of the above embodiments.

[0240] Finally, it should be noted that 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

[0241] In several embodiments provided in the present application, it should be understood that the disclosed devices and methods can also be implemented in other ways. The device embodiments described above are merely schematic. For example, the flowcharts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices, methods and computer program products according to multiple embodiments of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, a program segment or a part of a code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, and the combination of boxes in the block diagram and / or flowchart can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0242] In addition, the functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0243] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0244] The above description is only an embodiment of the present application and is not intended to limit the scope of protection of the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0245] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0246] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

Claims

1. A battery SOC estimation method, characterized in that: The method comprises: Determine the current battery state of the battery to be tested; the current battery state includes a charging state or a discharging state; Determining a target estimation strategy corresponding to the current battery state; Based on the target estimation strategy, the SOC of the battery to be tested is estimated.

2. The method according to claim 1, characterized in that The determining of a target estimation strategy corresponding to the current battery state includes: Determine to use a mapping relationship corresponding to the current battery state to perform SOC estimation.

3. The method according to claim 2, characterized in that Before determining to use the mapping relationship corresponding to the current battery state to perform SOC estimation, the method further includes: Detecting a first duration of the current of the battery to be tested before a reverse change occurs; the reverse change is a change in a direction opposite to the current corresponding to the current state of the battery; It is determined that the first duration is greater than or equal to a first time threshold.

4. The method according to claim 3, characterized in that The method further comprises: If it is determined that the first duration is less than the first time threshold, the target estimation strategy is determined to be the ampere-hour integration method.

5. The method according to any one of claims 2 to 4, characterized in that: The determining to use a mapping relationship corresponding to the current battery state to perform SOC estimation includes: If the current battery state is a charging state, determine to use a mapping relationship between battery parameters in the charging section and SOC to estimate the SOC; If the current battery state is a discharging state, it is determined to use a mapping relationship between the battery parameters of the discharging section and the SOC to perform SOC estimation.

6. The method according to claim 5, characterized in that The battery parameters include model parameters of the equivalent circuit model and an open circuit voltage.

7. The method according to claim 6, characterized in that The determining to use a mapping relationship corresponding to the current battery state to perform SOC estimation includes: Determine to use a mapping relationship corresponding to the current battery state, and perform SOC estimation in combination with a correction algorithm.

8. The method according to claim 1, characterized in that The battery state also includes a static state; and the determining of a target estimation strategy corresponding to the current battery state includes: Determining a historical battery state of the battery under test before the static state; Determine to use a mapping relationship corresponding to the historical battery state to perform SOC estimation.

9. The method according to claim 8, characterized in that Before determining the battery status of the battery to be tested in the static state, the method further includes: Detecting a second duration of the battery under test in the static state; It is determined that the second duration is greater than or equal to a second time threshold.

10. The method according to claim 9, characterized in that The method further comprises: If it is determined that the second duration is less than the second time threshold, the target estimation strategy is determined to be a historically determined estimation strategy.

11. The method according to any one of claims 8 to 10, characterized in that: The determining to use a mapping relationship corresponding to the historical battery state to perform SOC estimation includes: If the historical battery state is a charging state, determining to use a mapping relationship between the battery parameters of the charging section and the SOC to perform SOC estimation; If the historical battery state is a discharge state, it is determined to use a mapping relationship between the battery parameters of the discharge segment and the SOC to perform SOC estimation.

12. The method according to claim 11, characterized in that The battery parameters include open circuit voltage.

13. A SOC estimation device, characterized in that: The device comprises: A first determination module is used to determine the current battery state of the battery to be tested; the current battery state includes a charging state or a discharging state; A strategy module, used to determine a target estimation strategy corresponding to the current battery state; An estimation module is used to estimate the SOC of the battery to be tested based on the target estimation strategy.

14. A battery management system, characterized in that: The battery management system comprises: processor; a memory for storing processor-executable instructions; Wherein, when the processor calls the executable instructions, the operation of any method described in claims 1-12 is implemented.

15. A computer-readable storage medium, characterized in that: Computer instructions are stored thereon, and when the computer instructions are executed by a processor, the steps of any method described in claims 1-12 are implemented.

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