Power battery soc estimation method and system based on real-time working condition

Abstract

The embodiment of the application provides a kind of based on real-time working condition's power battery SOC estimation method and system, belong to battery management technical field.The estimation method includes: obtaining current driving condition, determine the actual torque demand of current driving condition;Determine whether the actual torque demand is greater than or equal to 0;In the case where it is judged that the actual torque demand is greater than or equal to 0, obtain the electromagnetic torque of current driving condition;In the case where it is judged that the actual torque demand is less than 0, obtain the mechanical torque of hydraulic brake system of current driving condition, and obtain the electromagnetic torque of current driving condition according to the mechanical torque;Obtain the charge-discharge current of power battery under current driving condition;Determine whether the charge-discharge current exceeds the maximum current allowed.The estimation method and system estimate the SOC of power battery by the real-time working condition of vehicle driving, do not need to detect the charge-discharge current of battery, and consider different conditions such as driving and braking, and the calculation precision is high.

Description

Technical Field

[0001] This invention relates to the field of battery management technology, and more specifically to a method and system for estimating the state of charge (SOC) of a power battery based on real-time operating conditions. Background Technology

[0002] Estimating the state of charge (SOC) of a power battery requires detecting the charging and discharging current. However, current detection requires an additional current sensor, which increases the size and cost of the system. Furthermore, the SOC estimation is also subject to errors due to the accuracy of the sensor. Existing technologies use algorithms such as Kalman filtering to eliminate these errors, but these algorithms involve a large amount of computation, which increases the complexity of the battery management system and raises development costs. Summary of the Invention

[0003] The purpose of this invention is to provide a power battery SOC estimation method and system based on real-time operating conditions. This estimation method and system estimates the SOC of the power battery through the real-time operating conditions of the vehicle, without the need to detect the charging and discharging current of the battery, and takes into account different operating conditions such as driving and braking, with high calculation accuracy.

[0004] To achieve the above objectives, one embodiment of the present invention provides a power battery SOC estimation method based on real-time operating conditions, the estimation method comprising: Obtain the current driving conditions and determine the actual torque requirement under the current driving conditions; Determine whether the actual torque demand is greater than or equal to 0; If the actual torque demand is determined to be greater than or equal to 0, the electromagnetic torque of the current driving condition is obtained. If the actual torque demand is less than 0, the mechanical torque of the hydraulic braking system under the current driving condition is obtained, and the electromagnetic torque under the current driving condition is obtained based on the mechanical torque. Obtain the charging and discharging current of the power battery under the current driving conditions; Determine whether the charging / discharging current exceeds the maximum allowable current; If it is determined that the charging and discharging current does not exceed the maximum allowable current, the SOC of the power battery under the current driving condition is obtained; If it is determined that the charging and discharging current exceeds the maximum allowable current, the SOC of the power battery under the current driving condition is estimated according to the maximum current and the ampere-hour integral method. At the same time, the actual torque demand is limited according to the maximum charging and discharging current, and the process returns to obtain the current driving condition and determine the actual torque demand under the current driving condition.

[0005] Optionally, the current driving condition is obtained, and the actual torque requirement of the current driving condition is determined, including: The actual torque requirement for the current driving condition is determined according to formula (1). (1) in, For actual torque requirements, For mechanical transmission efficiency, Let be the moment of inertia.

[0006] Optionally, obtaining the electromagnetic torque under the current driving condition includes: The electromagnetic torque for the current driving condition is obtained according to formulas (2) to (4). (2) (3) (4) in, For electromagnetic torque, For the mechanical torque of the hydraulic braking system, This is the ratio of the electromagnetic torque to the mechanical torque of the hydraulic braking system. This is the maximum permissible braking torque.

[0007] Optionally, obtaining the charging and discharging current of the power battery under the current driving conditions includes: The mechanical power of the motor under the current driving condition is obtained according to formula (5). (5) The output power of the inverter under the current driving condition is obtained according to formula (6). (6) in, This refers to the mechanical power of the motor. The output power of the inverter. Let be the angular velocity of the motor. The motor efficiency at the current torque and speed. This represents the motor speed.

[0008] Optionally, obtaining the charging and discharging current of the power battery under the current driving conditions further includes: The conduction loss of the power transistors in the inverter can be obtained according to formula (7). (7) The switching loss of the power transistor can be obtained according to formula (8). (8) in, This refers to the conduction loss of the power transistor. The switching cycle of the power transistor. This is the on-state voltage drop when the power transistor carries the rated current. This refers to the voltage drop of the power transistor under light load. Rated current, This represents the actual current flowing through the power transistor. This refers to the duty cycle of the power transistor. For the switching losses of the power transistor, This refers to the conduction loss of the power transistor at its rated current. This refers to the turn-off loss of the power transistor at rated current. For switching frequency, This represents the amplitude of the alternating current.

[0009] Optionally, obtaining the charging and discharging current of the power battery under the current driving conditions further includes: The total power losses of the three-phase inverter power transistors are obtained according to formula (9). (9) in, This represents the total power losses of the three-phase inverter power transistors.

[0010] Optionally, obtaining the charging and discharging current of the power battery under the current driving conditions further includes: The charging and discharging current of the power battery is obtained according to formula (10). (10) in, The charging and discharging current of the power battery. This refers to the terminal voltage of the power battery pack.

[0011] Optionally, if it is determined that the charging / discharging current does not exceed the maximum allowable current, the state of charge (SOC) of the power battery under the current driving condition is obtained, including: The SOC of the power battery under the current driving conditions is obtained according to formula (11). (11) in, For the SOC of the power battery, This is the initial value of the SOC (State of Charge) of the power battery. This refers to the rated capacity of the power battery.

[0012] On the other hand, the present invention also provides a power battery SOC estimation system based on real-time operating conditions, the estimation system including a processor for executing the estimation method as described above.

[0013] Through the above technical solution, this invention provides a method and system for estimating the State of Charge (SOC) of a power battery based on real-time operating conditions. By acquiring the current driving conditions, the actual torque demand under these conditions is determined. It is then determined whether the actual torque demand is greater than or equal to 0. When the actual torque demand is greater than or equal to 0, the power battery discharges, and the driving force is entirely provided by the motor. When the actual torque demand is less than 0, the power battery charges, and the vehicle is in a braking state. The braking force is partly provided by the motor and partly by the hydraulic braking system. The electromagnetic torque of the motor is calculated based on different actual torque demands, and then the power of the motor and inverter is calculated. The charging and discharging current of the power battery is calculated based on the principle of energy conservation. When the current does not exceed the maximum allowable charging and discharging current of the power battery, the SOC of the power battery is directly estimated according to the formula. When the current exceeds the maximum allowable charging and discharging current of the power battery, the SOC needs to be estimated using the ampere-hour integral method based on the maximum current. Simultaneously, the actual torque is limited based on the maximum charging and discharging current. This estimation method and system estimates the SOC of the power battery through the real-time operating conditions of the vehicle, without needing to detect the battery's charging and discharging current. It considers different operating conditions such as driving and braking, and calculates the charging and discharging current based on the principle of energy conservation, resulting in high calculation accuracy.

[0014] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart of a power battery SOC estimation method based on real-time operating conditions, according to one embodiment of the present invention. Figure 2 This is a flowchart of obtaining the charging and discharging current of the power battery under the current driving conditions, according to one embodiment of the present invention. Detailed Implementation

[0016] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0017] like Figure 1 The diagram shows a flowchart of a power battery SOC estimation method based on real-time operating conditions, according to one embodiment of the present invention. Figure 1 In this context, the estimation method may include: In step S1, the current driving conditions are obtained, and the actual torque requirements of the current driving conditions are determined; In step S2, it is determined whether the actual torque demand is greater than or equal to 0; In step S3, if the actual torque demand is greater than or equal to 0, the electromagnetic torque of the current driving condition is obtained. In step S4, if the actual torque demand is less than 0, the mechanical torque of the hydraulic braking system under the current driving condition is obtained, and the electromagnetic torque under the current driving condition is obtained based on the mechanical torque. In step S5, the charging and discharging current of the power battery under the current driving conditions is obtained; In step S6, it is determined whether the charging and discharging current exceeds the maximum allowable current; In step S7, if it is determined that the charging and discharging current does not exceed the maximum allowable current, the SOC of the power battery under the current driving conditions is obtained; In step S8, if it is determined that the charging and discharging current exceeds the maximum allowable current, the SOC of the power battery under the current driving condition is estimated according to the maximum current and the ampere-hour integration method. At the same time, the actual torque demand is limited according to the maximum charging and discharging current, and the process returns to the step of obtaining the current driving condition and determining the actual torque demand under the current driving condition.

[0018] In steps S1 to S8, the current driving condition is obtained based on the accelerator and brake pedals, and the actual torque demand under the current driving condition is determined. It is determined whether the actual torque demand is greater than or equal to 0. When the actual torque demand is greater than or equal to 0, the power battery discharges, and the driving force is entirely provided by the motor. The electromagnetic torque of the current driving condition is obtained. When the actual torque demand is less than 0, the power battery charges, the vehicle is in a braking state, and the braking force is partly provided by the motor and partly by the hydraulic braking system. The mechanical torque of the current driving condition is obtained, and the electromagnetic torque of the current driving condition is obtained based on the mechanical torque. The charging and discharging current of the power battery under the current driving condition is obtained, and it is determined whether the charging and discharging current exceeds the maximum allowable current. If it is determined that the charging and discharging current does not exceed the maximum allowable current, the SOC of the power battery under the current driving condition is obtained. If it is determined that the charging and discharging current exceeds the maximum allowable current, the SOC of the power battery under the current driving condition is estimated according to the maximum current and the ampere-hour integration method. At the same time, the actual torque demand is limited according to the maximum charging and discharging current, and the process returns to the step of obtaining the current driving condition and determining the actual torque demand under the current driving condition. This estimation method estimates the SOC of the power battery by measuring the real-time operating conditions of the vehicle, without needing to detect the charging and discharging current of the battery. It also considers different operating conditions such as driving and braking, and calculates the charging and discharging current based on the principle of energy conservation, resulting in high calculation accuracy.

[0019] In Figure 1In the method shown, step S1 can be used to obtain the current driving condition and determine the actual torque requirement of the current driving condition. The specific method for determining the actual torque requirement of the current driving condition can be of various forms known to those skilled in the art. In one example of the present invention, the actual torque requirement is determined by the current driving condition. The mechanical transmission efficiency of the current driving condition is obtained empirically, and the actual torque requirement of the current driving condition can be determined according to formula (1). (1) in, For actual torque requirements, For mechanical transmission efficiency, Let be the moment of inertia.

[0020] Based on the actual torque demand value determined in step S1, step S2 can be used to determine whether the actual torque demand is greater than or equal to 0. Step S3 can be used to obtain the electromagnetic torque of the current driving condition when the actual torque demand is greater than or equal to 0. Step S4 can be used to obtain the mechanical torque of the hydraulic braking system of the current driving condition when the actual torque demand is less than 0, and obtain the electromagnetic torque of the current driving condition based on the mechanical torque. When the actual torque demand is greater than or equal to 0, the driving force is entirely provided by the motor. When the actual torque demand is less than 0, the vehicle is in a braking state, and the braking force is partly provided by the motor and partly by the hydraulic braking system. The specific method for obtaining the electromagnetic torque of the current driving condition can be any of the forms known to those skilled in the art. In one embodiment of the present invention, the electromagnetic torque can be obtained according to formulas (2) to (4) for the current driving condition. (2) (3) (4) in, For electromagnetic torque, For the mechanical torque of the hydraulic braking system, This is the ratio of the electromagnetic torque to the mechanical torque of the hydraulic braking system. The maximum allowable braking torque is less than 0 because the mechanical torque of the hydraulic braking system is also the braking torque. Under braking conditions, the electromagnetic torque and the mechanical torque of the hydraulic braking system provide braking torque simultaneously. The relationship between the two can be expressed by formula (3). Therefore, under braking conditions, the electromagnetic torque and the mechanical torque of the hydraulic braking system can be obtained by formula (2) and formula (3), which is formula (4).

[0021] Step S5 can be used to obtain the charging and discharging current of the power battery under the current driving conditions. The specific method for obtaining the charging and discharging current of the power battery under the current driving conditions can be of various forms known to those skilled in the art. In one example of the present invention, the method for obtaining the charging and discharging current of the power battery under the current driving conditions may include, for example... Figure 2 The steps are shown. Specifically: In step S10, the mechanical power of the motor under the current driving condition is obtained according to formula (5). (5) In step S11, the output power of the inverter under the current driving condition is obtained according to formula (6). (6) in, This refers to the mechanical power of the motor. The output power of the inverter. Let be the angular velocity of the motor. The motor efficiency at the current torque and speed. This represents the motor speed.

[0022] In step S12, the conduction loss of the power transistors in the inverter is obtained according to formula (7). (7) In step S13, the switching loss of the power transistor is obtained according to formula (8). (8) in, This refers to the conduction loss of the power transistor. The switching cycle of the power transistor. This is the on-state voltage drop when the power transistor carries the rated current. This refers to the voltage drop of the power transistor under light load. Rated current, This represents the actual current flowing through the power transistor. This refers to the duty cycle of the power transistor. For the switching losses of the power transistor, This refers to the conduction loss of the power transistor at its rated current. This refers to the turn-off loss of the power transistor at rated current. For switching frequency, This represents the amplitude of the alternating current.

[0023] In step S14, the total loss of the three-phase inverter power transistors is obtained according to formula (9). (9) in, This represents the total power losses of the three-phase inverter power transistors.

[0024] In step S15, the charging and discharging current of the power battery is obtained according to formula (10). (10) in, The charging and discharging current of the power battery. This refers to the terminal voltage of the power battery pack.

[0025] Step S6 can be used to determine whether the charging / discharging current exceeds the maximum allowable current. Step S7 can be used to obtain the SOC of the power battery under the current driving conditions if the charging / discharging current does not exceed the maximum allowable current. The specific method for obtaining the SOC of the power battery under the current driving conditions can be of various forms known to those skilled in the art. In one example of the present invention, the SOC of the power battery under the current driving conditions can be obtained according to formula (11). (11) in, For the SOC of the power battery, This is the initial value of the SOC (State of Charge) of the power battery. This refers to the rated capacity of the power battery.

[0026] Step S8 can be used to estimate the SOC of the power battery under the current driving condition based on the maximum current and the ampere-hour integral method when it is determined that the charging and discharging current exceeds the maximum allowable current. At the same time, the actual torque demand is limited based on the maximum charging and discharging current, and the process returns to obtain the current driving condition and determine the actual torque demand under the current driving condition.

[0027] On the other hand, the present invention also provides a power battery SOC estimation system based on real-time operating conditions, the estimation system including a processor for executing the estimation method as described above.

[0028] Through the above technical solution, this invention provides a method and system for estimating the State of Charge (SOC) of a power battery based on real-time operating conditions. By acquiring the current driving conditions, the actual torque demand under these conditions is determined. It is then determined whether the actual torque demand is greater than or equal to 0. When the actual torque demand is greater than or equal to 0, the power battery discharges, and the driving force is entirely provided by the motor. When the actual torque demand is less than 0, the power battery charges, and the vehicle is in a braking state. The braking force is partly provided by the motor and partly by the hydraulic braking system. The electromagnetic torque of the motor is calculated based on different actual torque demands, and then the power of the motor and inverter is calculated. The charging and discharging current of the power battery is calculated based on the principle of energy conservation. When the current does not exceed the maximum allowable charging and discharging current of the power battery, the SOC of the power battery is directly estimated according to the formula. When the current exceeds the maximum allowable charging and discharging current of the power battery, the SOC needs to be estimated using the ampere-hour integral method based on the maximum current. Simultaneously, the actual torque is limited based on the maximum charging and discharging current. This estimation method and system estimates the SOC of the power battery through the real-time operating conditions of the vehicle, without needing to detect the battery's charging and discharging current. It considers different operating conditions such as driving and braking, and calculates the charging and discharging current based on the principle of energy conservation, resulting in high calculation accuracy.

[0029] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0030] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0031] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0032] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0033] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0034] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0035] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0036] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0037] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for estimating the state of charge (SOC) of a power battery based on real-time operating conditions, characterized in that, The estimation method includes: Obtain the current driving conditions and determine the actual torque requirement under the current driving conditions; Determine whether the actual torque demand is greater than or equal to 0; If the actual torque demand is determined to be greater than or equal to 0, the electromagnetic torque of the current driving condition is obtained. If the actual torque demand is less than 0, the mechanical torque of the hydraulic braking system under the current driving condition is obtained, and the electromagnetic torque under the current driving condition is obtained based on the mechanical torque. Obtain the charging and discharging current of the power battery under the current driving conditions; Determine whether the charging / discharging current exceeds the maximum allowable current; If it is determined that the charging and discharging current does not exceed the maximum allowable current, the SOC of the power battery under the current driving condition is obtained; If it is determined that the charging and discharging current exceeds the maximum allowable current, the SOC of the power battery under the current driving condition is estimated according to the maximum current and the ampere-hour integration method. At the same time, the actual torque demand is limited according to the maximum charging and discharging current, and the process returns to obtain the current driving condition and determine the actual torque demand under the current driving condition. Obtaining the charging and discharging current of the power battery under the current driving conditions includes: The mechanical power of the motor under the current driving condition is obtained according to formula (5). ，（5） The output power of the inverter under the current driving condition is obtained according to formula (6). ，（6） in, This refers to the mechanical power of the motor. The output power of the inverter. Let be the angular velocity of the motor. The motor efficiency at the current torque and speed. This refers to the motor speed. Electromagnetic torque; The conduction loss of the power transistors in the inverter can be obtained according to formula (7). ，（7） The switching loss of the power transistor can be obtained according to formula (8). ，（8） in, This refers to the conduction loss of the power transistor. The switching cycle of the power transistor. This is the on-state voltage drop when the power transistor carries the rated current. This refers to the voltage drop of the power transistor under light load. Rated current, This represents the actual current flowing through the power transistor. This refers to the duty cycle of the power transistor. For the switching losses of the power transistor, This refers to the conduction loss of the power transistor at its rated current. This refers to the turn-off loss of the power transistor at rated current. For switching frequency, The amplitude of the alternating current; The total power losses of the three-phase inverter power transistors are obtained according to formula (9). ，（9） in, This represents the total power losses of the three-phase inverter power transistors. The charging and discharging current of the power battery is obtained according to formula (10). ，（10） in, The charging and discharging current of the power battery. This refers to the terminal voltage of the power battery pack.

2. The estimation method according to claim 1, characterized in that, Obtain the current driving conditions and determine the actual torque requirement for the current driving conditions, including: The actual torque requirement for the current driving condition is determined according to formula (1). ，（1） in, For actual torque requirements, For mechanical transmission efficiency, Let be the moment of inertia.

3. The estimation method according to claim 2, characterized in that, Obtaining the electromagnetic torque under the current driving condition includes: The electromagnetic torque for the current driving condition is obtained according to formulas (2) to (4). ，（2） ，（3） ，（4） in, For the mechanical torque of the hydraulic braking system, This is the ratio of the electromagnetic torque to the mechanical torque of the hydraulic braking system. This is the maximum permissible braking torque.

4. The estimation method according to claim 3, characterized in that, If it is determined that the charging / discharging current does not exceed the maximum allowable current, the state of charge (SOC) of the power battery under the current driving condition is obtained, including: The SOC of the power battery under the current driving conditions is obtained according to formula (11). ，（11） in, For the SOC of the power battery, This is the initial value of the SOC (State of Charge) of the power battery. This refers to the rated capacity of the power battery.

5. A power battery SOC estimation system based on real-time operating conditions, characterized in that, The estimation system includes a processor for executing the estimation method as described in any one of claims 1 to 4.

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