Intelligent current limiting control method and control system for vehicle-mounted sodium ion battery

Abstract

The invention provides an intelligent current limiting control method and system for a vehicle-mounted sodium-ion battery, and belongs to the technical field of sodium-ion batteries. According to the control method, real-time collection and preprocessing of multi-dimensional parameters are achieved through a distributed collection module, graded temperature threshold values are set based on the low-temperature characteristics of the sodium-ion battery, and the current limiting accuracy of the sodium-ion battery is improved; after current-limiting control is triggered, a resistor current-limiting main mode is started preferentially, and the effectiveness of an initial strategy is guaranteed in combination with a hardware self-checking mechanism; through intelligent switching and redundancy control of double current limiting modes, precise current limiting is realized by matching with a dynamic duty ratio algorithm, and meanwhile, a multi-level fault diagnosis and safety cut-off mechanism and multi-condition collaborative exit logic are constructed. The corresponding system adopts a software and hardware collaborative architecture of a sensing layer, a control layer, an execution layer and a communication layer, and high efficiency of the control method is ensured. The core problem of insufficient low-temperature charging safety of the sodium-ion battery is effectively solved, safe operation of the battery is guaranteed, and the service life of the battery is ensured.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, and more specifically, relates to an intelligent current limiting control method and control system for vehicle-mounted sodium-ion batteries. Background Technology

[0002] In recent years, the global automotive industry has been undergoing profound changes centered on electrification and intelligentization. As an important part of the transportation sector, passenger vehicles are also accelerating their electrification process. With the surge in the number of onboard electrical devices and the increasing complexity of controller architecture, higher requirements are being placed on the performance, lifespan, and safety of onboard starter batteries.

[0003] Traditional lead-acid batteries, due to their inherent disadvantages such as low capacity, short cycle life, and low charge / discharge efficiency, can no longer meet the power demands of modern passenger vehicles and are gradually being replaced by battery products with superior performance. Lithium-ion batteries, with their high energy density and excellent charge / discharge rate performance, have been widely used in the field of automotive starting batteries. However, lithium resources are unevenly distributed globally and have limited reserves. With the large-scale development of the new energy vehicle industry, the supply and demand imbalance of lithium resources is becoming increasingly prominent, resulting in high production costs for lithium batteries and severely restricting their large-scale application.

[0004] Against this backdrop, sodium-ion batteries, as an emerging electrochemical energy storage technology, have become a highly promising alternative in the field of vehicle starting batteries due to their advantages such as abundant and widely distributed raw materials, low cost, and significant characteristics in cycle life and low-temperature discharge performance. They are particularly suitable for the complex usage scenarios of passenger vehicles and the needs of use in cold regions.

[0005] However, sodium-ion batteries still face many core challenges in their industrialization process, among which insufficient safety during low-temperature charging is a key bottleneck restricting their practical application in vehicles. From the perspective of the electrochemical characteristics of sodium-ion batteries, the mobility of sodium ions decreases significantly at low temperatures. If high-current charging is used at this time, sodium deposition can easily occur inside the battery, which will not only severely damage the battery's cycle life and charge-discharge performance, but may also lead to safety risks such as battery thermal runaway.

[0006] Currently, the industry mainly focuses on cell material research and development and battery structure design to address the low-temperature charging problem of sodium-ion batteries. However, these methods often require lengthy R&D cycles and substantial investments, making breakthroughs difficult to achieve in the short term. Therefore, relying on the precise intervention of a Battery Management System (BMS) to monitor battery status in real time, dynamically optimize charging strategies, and precisely control temperature and current has become a key approach to ensure the safe and efficient operation of sodium-ion batteries under complex conditions such as low temperatures and high-frequency charging and discharging. This is of great significance for promoting the practical application of sodium-ion batteries in passenger vehicles.

[0007] Existing battery current limiting control technologies are mostly designed for lithium batteries and fail to fully consider the unique electrochemical characteristics of sodium-ion batteries, resulting in the following shortcomings: The parameters collected are limited to a few parameters, such as battery temperature and charging current, and fail to fully integrate multi-dimensional information such as cell health status, environmental conditions, and hardware operating status, resulting in insufficient accuracy and reliability of current limiting decisions. The current limiting strategy lacks a graded dynamic adjustment mechanism and adopts a "one-size-fits-all" current limiting method, which is difficult to adapt to the different characteristics of sodium-ion batteries in different low temperature ranges, and is prone to problems such as insufficient current limiting leading to safety risks. The current limiting mode is singular and lacks redundancy design. When the single current limiting mode fails, it cannot switch to the backup mode in time, making it difficult to ensure the continuous safety of the battery under complex operating conditions. The lack of a sound fault diagnosis and safety backup mechanism means that there is insufficient response to scenarios such as hardware failures and control failures that may occur during the current limiting process, which poses a safety hazard. The current limiting exit logic is not scientific and reasonable enough. It is easy for the current limiting function to exit erroneously or be delayed due to instantaneous parameter fluctuations, which will affect the battery's lifespan.

[0008] To address the problems existing in the prior art, this invention proposes an intelligent current limiting control method and control system for vehicle-mounted sodium-ion batteries. Through innovative designs such as multi-parameter fusion sensing, hierarchical dynamic current limiting, dual-mode intelligent redundancy, and multi-level fault diagnosis, it achieves precise, safe, and efficient control of the low-temperature charging process of sodium-ion batteries, providing technical support for the industrial application of sodium-ion batteries. Summary of the Invention

[0009] The purpose of this invention is to provide an intelligent current limiting control method for vehicle-mounted sodium-ion batteries to solve the problem of insufficient safety when charging sodium-ion batteries at low temperatures.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is: to provide an intelligent current limiting control method for vehicle-mounted sodium-ion batteries, comprising the following steps: Step 1, Parameter Acquisition and Preprocessing: Collect core parameters of the battery cell, charging status parameters, and environmental and hardware status parameters through a distributed acquisition module. Perform filtering and outlier removal preprocessing on the collected data to eliminate high-frequency noise and establish a parameter correlation model. Step 2, Current Limiting Trigger and Initial Strategy Selection: When the BMS confirms that the battery is in an effective charging stage and the cell temperature is less than or equal to the preset low temperature threshold T2, current limiting control is triggered; the resistor current limiting main mode is started first, and the corresponding resistance value current limiting resistor is selected according to the temperature level. Before starting, hardware self-test is performed, and if there is an abnormality, it jumps to the pulse current limiting protection mode. Step 3, Dual Current Limiting Mode Switching and Redundancy Control: In resistor current limiting mode, the main charging MOSFET is turned off and the current limiting branch MOSFET is enabled to monitor the temperature of the current limiting resistor in real time; when the preset switching conditions are met, it switches to pulse current limiting mode, and the main charging MOSFET is controlled by PWM signal to limit the current in pulse mode and the PWM parameters are dynamically adjusted; when the back-off conditions are met, it smoothly switches back to resistor current limiting mode. Step 4, Fault Coverage and Safety Cut-off: In the event of a dual-mode failure scenario, immediately shut down the relevant MOSFETs and lock the charging function; Step 5, Current Limiting Exit: When any exit condition such as temperature, state switching, or SOC reaches the standard is met, current limiting control will exit and normal charging will resume.

[0011] In one possible implementation, in step 1: The core parameters of the battery cell include individual cell temperature, total voltage, individual cell voltage balance, SOC, and SOH. The charging status parameters include total charging current and charging voltage; The environmental and hardware status parameters include the vehicle ambient temperature, the current limiting resistor temperature, and the charging main MOSFET junction temperature. The sampling frequency is ≥100Hz, and the filtering method is moving average filtering.

[0012] In one possible implementation, the judgment logic of the parameter association model in step 1 is: when the temperature difference between the cell temperature and the ambient temperature is ≥5℃, the heat dissipation is determined to be abnormal.

[0013] In one possible implementation, in step 2: The temperature grading is set as T1≤-20℃, T2 is-20℃~0℃, and T0>0℃. No current limiting is required under the T0 condition. The BMS confirms that the battery is in an effective charging phase by checking the current direction and the generator wake-up signal. Hardware self-test includes MCU detection of whether the current limiting resistor has a continuity without open / short circuits and whether the MOSFET drive signal of the current limiting circuit is normal; In resistor current limiting mode, T1 corresponds to high resistance R1, and T2 corresponds to low resistance R2. The current limiting resistor is switched by the relay controlled by the MCU.

[0014] In one possible implementation, in step 3: Soft shutdown is achieved by gradually reducing the gate voltage of the charging main MOSFET through the driving circuit. In the current-limiting resistor mode, the maximum withstand temperature Tr_max of the resistor is set. Tr_max is determined to be 85℃ based on the temperature resistance rating of the current-limiting resistor material. This mode is maintained when Tr≤Tr_max-10℃, and when Tr_max-10℃<Tr<Tr_max, the BMS issues an overheat warning for the resistor.

[0015] In one possible implementation, in step 3: The trigger condition for switching to pulse current limiting mode is that the temperature of the current limiting resistor Tr ≥ Tr_max, or the current limiting resistor is short-circuited, causing the current to exceed 120% of the safety threshold I_safe. In pulse current limiting mode, the PWM pulse period is fixed at 10ms, and the duty cycle D = I_target / I_peak. I_target is the low-temperature safe charging current obtained by looking up a table based on SOC and temperature, and I_peak is the peak current during a single turn-on and does not exceed I_safe.

[0016] In one possible implementation, the dynamic adjustment rule for the PWM duty cycle is as follows: when the cell temperature rises close to T0, the SOC increases to ≥80%, or the current limiting resistor temperature drops to Tr≤Tr_max-20℃, the duty cycle D is gradually increased; conversely, the duty cycle D is gradually decreased.

[0017] In one possible implementation, the mode cut-back condition in step 3 is Tr≤Tr_max-20℃ and lasts for 3s. During the cut-back, the current fluctuation is ≤5%I_target by gradually changing the PWM duty cycle.

[0018] In one possible implementation, the dual-mode failure scenarios in step 4 include: In resistor-limited current mode, the current exceeds 1.5 × I_safe for 50ms. In pulse current limiting mode, the PWM output is abnormal or the current continues to exceed 1.5×I_safe for 50ms. The voltage of a single cell exceeds the upper limit voltage or the temperature rises by ≥5℃ / s.

[0019] The intelligent current limiting control method and control system for vehicle-mounted sodium-ion batteries of the present invention have the following significant advantages compared with the prior art: By replacing traditional lead-acid batteries with sodium-ion batteries, and through real-time monitoring and protection by the battery management system (BMS), the disadvantages of low capacity and short lifespan of lead-acid batteries can be overcome, thereby improving the performance of the on-board power system of passenger vehicles. To address the issue that low-temperature, high-current charging can degrade the performance of sodium-ion batteries, intelligent current limiting control is used to protect the battery's lifespan and ensure its long-term stable operation under complex conditions. The design employs two complementary current limiting methods to avoid the limitations of a single current limiting method and improve the reliability and adaptability of current limiting control. The design incorporates a scientifically sound current limiting exit control logic to address issues such as slow charging and severe overheating caused by excessive current limiting, thereby ensuring battery safety. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The flowchart illustrates an intelligent current limiting control method for vehicle-mounted sodium-ion batteries provided by this invention. Detailed Implementation

[0022] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0023] Unless otherwise explicitly specified, the use of terms such as "first," "second," or "third" is intended to distinguish different objects, not to describe a specific order.

[0024] Unless otherwise expressly defined, the use of directional terms such as “center,” “lateral,” “longitudinal,” “horizontal,” “vertical,” “top,” “bottom,” “inner,” “outer,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “clockwise,” “counterclockwise,” “high,” and “low” to indicate orientation or positional relationships is based on the orientation and positional relationships shown in the accompanying drawings and is only for the convenience of describing the invention and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the specific scope of protection of the invention.

[0025] Please see Figure 1 The core objective of this invention is to provide an intelligent current-limiting control method and control system for vehicle-mounted sodium-ion batteries, in order to solve the core problem of insufficient safety during low-temperature charging of sodium-ion batteries, and to achieve the following specific objectives: By replacing traditional lead-acid batteries with sodium-ion batteries, and through real-time monitoring and protection by the battery management system (BMS), the disadvantages of low capacity and short lifespan of lead-acid batteries can be overcome, thereby improving the performance of the on-board power system of passenger vehicles. To address the issue that low-temperature, high-current charging can degrade the performance of sodium-ion batteries, intelligent current limiting control is used to protect the battery's lifespan and ensure its long-term stable operation under complex conditions. The design employs two complementary current limiting methods to avoid the limitations of a single current limiting method and improve the reliability and adaptability of current limiting control. The design incorporates a scientifically sound current limiting exit control logic to address issues such as slow charging and severe overheating caused by excessive current limiting, thereby ensuring battery safety.

[0026] The intelligent current limiting control method and control system for vehicle-mounted sodium-ion batteries provided by this invention achieves precise control of the low-temperature charging process of sodium-ion batteries through multi-dimensional parameter acquisition, hierarchical dynamic decision-making, dual-mode redundant control, and multi-level safety protection.

[0027] The intelligent current limiting control method for vehicle-mounted sodium-ion batteries includes the following steps: Parameter acquisition and preprocessing: The core of this step is to comprehensively and accurately acquire various parameters related to the charging state of sodium-ion batteries, and to eliminate interference and establish correlations through preprocessing, so as to provide reliable data support for subsequent current limiting decisions.

[0028] Parameter acquisition is performed in real time using a distributed acquisition module at a sampling frequency of ≥100Hz, collecting the following three types of parameters: Key parameters of the battery cell include: individual cell temperature, total voltage, individual cell voltage equalization, SOC (State of Charge), and SOH (State of Health). Individual cell temperature is collected via a built-in NTC sensor with an accuracy of ±0.5℃; the SOC measurement error is ≤3%, ensuring accurate assessment of the remaining battery capacity; and the individual cell voltage equalization is used to prevent localized overcharging and ensure the consistency of the battery pack.

[0029] Charging status parameters include total charging current and charging voltage. The total charging current is collected using an onboard shunt with an accuracy of ±1%; the charging voltage is the output voltage of the vehicle-mounted generator, directly reflecting the operating status of the charging power supply.

[0030] Environmental and hardware status parameters include: vehicle ambient temperature, current-limiting resistor temperature, and charging main MOSFET junction temperature. The vehicle ambient temperature is the temperature inside the vehicle cabin, which reflects the heat dissipation conditions of the battery pack; the current-limiting resistor temperature is collected by a surface-mount temperature sensor close to the resistor body, with a sampling accuracy of ±1℃; the charging main MOSFET junction temperature is obtained through feedback from the driver chip to monitor the operating status of the power devices in real time.

[0031] Data preprocessing involves performing the following preprocessing operations on the collected raw data: Filtering: The data is smoothed by using a moving average filter, which effectively eliminates high-frequency noise interference from equipment such as vehicle motors, while removing obvious outliers to ensure the authenticity and stability of the data.

[0032] Establish a parameter correlation model: By analyzing the inherent relationships between various parameters, a parameter correlation model is constructed. For example, when the temperature difference between the cell temperature and the ambient temperature is ≥5℃, it is determined that the battery pack heat dissipation is abnormal, and an early warning message is issued in a timely manner, providing a basis for subsequent adjustments to the current limiting strategy.

[0033] Current limiting trigger and initial strategy selection: Based on the collected parameters, this step determines whether current limiting control needs to be activated, and selects an appropriate initial current limiting strategy according to the battery status to ensure the timeliness and effectiveness of current limiting control.

[0034] Rate limiting is triggered when both of the following conditions are met: Charging status determination: The BMS confirms that the battery is in an effective charging phase by detecting the current direction (forward charging current) and the generator wake-up signal. Activating current limiting control is only meaningful when the battery is truly charging, thus avoiding unnecessary operations.

[0035] Temperature condition determination: Based on the low-temperature characteristics of sodium-ion batteries, namely that the sodium ion mobility decreases significantly with decreasing temperature, easily leading to sodium deposition, a three-level temperature threshold is set: T1 (extremely low temperature): ≤-20℃, at which point the sodium ion mobility is <50% of the room temperature value, and the risk of battery charging is extremely high; T2 (Low Temperature): -20℃ to 0℃, at which point the sodium ion mobility is 50% to 80% of the room temperature value, and there is a certain risk in charging the battery; T0 (room temperature threshold): >0℃, at which point the sodium ion mobility is close to the room temperature level, and no current limiting control is required; It is worth noting that the temperature thresholds T1, T2, and T0 mentioned above are approximate ranges. The threshold ranges can be adjusted according to the different characteristics of the battery cells, which will not be elaborated here.

[0036] When the cell temperature is ≤T2, it indicates that the battery is in a low-temperature environment and current limiting control needs to be activated to ensure charging safety.

[0037] Initial strategy selection: Prioritize resistor current limiting as the main current limiting mode: When the cell temperature is ≤T2 and the battery is in an effective charging phase, resistor current limiting is selected as the primary current limiting mode. The corresponding current limiting resistor value is selected based on the temperature classification: T1 (extremely low temperature) corresponds to a high resistance value R1 to achieve a stronger current limiting effect and prevent damage to the battery from high current; T2 (low temperature) corresponds to a low resistance value R2 to ensure battery operation safety. The switching of the current limiting resistor is achieved through MCU-controlled relays, realizing dynamic matching of "temperature-resistance".

[0038] Hardware self-test: Before activating the resistor current limiting mode, the MCU performs a self-test on the relevant hardware, including checking whether the current limiting resistor is functioning correctly (no open / short circuit faults) and whether the MOSFET drive signal of the current limiting circuit is normal. If an abnormality is found during the self-test, it means that the resistor current limiting mode cannot work properly. At this time, it will directly jump to the pulse current limiting backup mode to avoid current limiting failure due to hardware failure.

[0039] Dual current limiting mode switching and redundant control: This step uses intelligent switching and redundant design of two current limiting modes to balance the accuracy, safety and reliability of current limiting control, ensuring effective current limiting under different operating conditions.

[0040] Current limiting control 1: (Resistor current limiting, main mode) Execution logic: The MCU sends a shutdown signal to the main charging MOSFET, employing a soft shutdown method. The gate voltage of the MOSFET is gradually reduced through the drive circuit to avoid voltage spikes caused by sudden shutdown, protecting the power devices and battery. Simultaneously, the current-limiting branch MOSFET is enabled, allowing the charging current to flow through the selected current-limiting resistor R (R1 or R2) to achieve current limiting. During resistor-limited current-mode operation, the temperature Tr of the current-limiting resistor is monitored in real time.

[0041] Safety constraints: Based on the temperature rating of the current-limiting resistor's material, the maximum withstand temperature Tr_max is set to 85℃. When Tr≤Tr_max-10℃ (i.e. ≤75℃, safe zone), the current resistor current-limiting mode is maintained; when Tr_max-10℃<Tr<Tr_max (i.e. 75℃<Tr<85℃, warning zone), the BMS issues a "resistor overheat warning" to prepare for possible subsequent mode switching.

[0042] Current limiting control 2: (PWM pulse current limiting, minimum protection mode) 3.2.1 Triggering Conditions: When one of the following two conditions occurs, the current-limiting branch MOSFET will be immediately turned off, switching from resistor current-limiting mode to pulse current-limiting mode: If the current-limiting resistor temperature Tr ≥ Tr_max (85℃), it indicates that the resistor is overheated. Continuing to use the resistor for current limiting may lead to resistor damage or thermal runaway. If current limiting control 1 fails, for example, if the current limiting resistor is short-circuited and the charging current exceeds 120% of the safety threshold I_safe, the resistor current limiting will no longer work and the system must switch to standby mode.

[0043] Execution logic: The MCU outputs a PWM signal through the MOS drive circuit to control the main charging MOSFET to operate in a "conduction-off" pulse mode, thereby limiting current by controlling the average current. The PWM pulse period is fixed at 10ms. This period setting avoids electromagnetic interference (EMI) caused by high-frequency switching, ensuring the normal operation of the vehicle's electronic equipment.

[0044] Dynamic duty cycle algorithm: The duty cycle D of the PWM signal is dynamically adjusted according to the battery status. The duty cycle is calculated as D = I_target / I_peak. Where I_target is the low-temperature safe charging current, which is obtained by looking up a table based on the cell temperature and SOC to ensure that the current limiting intensity is adapted to different states; I_peak is the peak current during a single conduction, which is strictly controlled within the safe threshold I_safe to avoid damage to the battery due to excessive peak current.

[0045] The dynamic adjustment rules for the duty cycle are as follows: When the cell temperature rises (closes to T0), the SOC increases to ≥80%, or the current limiting resistor temperature drops to Tr≤Tr_max-20℃ (65℃), it indicates that the battery's charging safety margin has increased. At this time, the duty cycle D is gradually increased, the current limiting intensity is reduced, and the charging efficiency is improved. Conversely, when the cell temperature decreases, the SOC is low, or the current-limiting resistor temperature increases, the duty cycle D is gradually reduced to enhance the current-limiting strength and ensure charging safety.

[0046] The mode switching and anti-jitter design meets the condition that the current-limiting resistor temperature Tr ≤ Tr_max - 20℃ (65℃) and this state lasts for 3 seconds. To avoid current fluctuations and equipment losses caused by frequent switching, a gradual transition of the PWM duty cycle is used during switching to smoothly switch from pulse current-limiting mode back to resistor current-limiting mode, ensuring that the current fluctuation during the switching process is ≤ 5%I_target, thus guaranteeing the stability of the battery and circuit.

[0047] Fault fallback and safety cut-off: To cope with the extreme situation where both modes fail, this step is designed with a multi-level fault diagnosis and safety cut-off mechanism to maximize the safety of the battery and the whole vehicle.

[0048] When any of the following "dual-mode failure" scenarios occur, immediately perform a safety disconnection operation: In resistor current limiting mode, if the charging current exceeds 1.5×I_safe for 50ms, it indicates that the current limiting resistor may have a serious fault such as a short circuit, and the resistor current limiting is completely ineffective. In pulse current limiting mode, abnormal PWM output (such as duty cycle runaway) or charging current exceeding 1.5×I_safe for 50ms indicates that pulse current limiting mode cannot effectively control the current. If the voltage of a single cell exceeds the upper limit (e.g., 4.2V), or if the cell temperature rises by ≥5℃ / s, both of these situations indicate that the battery may have serious safety hazards such as thermal runaway.

[0049] The safety disconnection actions include: immediately shutting off the main charging MOSFET and the current-limiting branch MOSFET to completely cut off the charging circuit; at the same time, locking the charging function, which can only be automatically unlocked after manual reset or fault clearance, to prevent safety accidents caused by restarting charging if the fault is not cleared.

[0050] Current limiting exit: When any of the following conditions are met, it indicates that the battery no longer requires current limiting protection, exits current limiting control, and resumes normal charging mode: Temperature-based exit: The cell temperature is ≥T0 (>0℃) and remains so for 5 seconds. The 5-second delay is set to avoid accidental exit caused by instantaneous temperature fluctuations and to ensure that the battery is indeed in a normal temperature environment. State switching: charging terminates (charging current ≤ 0.05C and lasts for 10s), battery switches to discharge state (current reverses) or rest state (current = 0 and lasts for 30s). At this time, the charging process has ended or the battery state has changed, and current limiting control is meaningless. SOC meets the standard: SOC≥95%. When the battery is close to full charge, continuing to limit the current will result in a slow charging speed. At this time, the current limiting will be removed and the normal charging method will be used to complete the subsequent charging process.

[0051] Based on the same inventive concept, this invention also provides an intelligent current limiting control system for vehicle-mounted sodium-ion batteries. This control system is used to implement the aforementioned intelligent current limiting control method for vehicle-mounted sodium-ion batteries. It employs a hardware and software co-design and consists of four parts: a sensing layer, a control layer, an execution layer, and a communication layer. The modules at each layer cooperate with each other to ensure the efficient implementation of the control method.

[0052] The perception layer is the foundation of the system's data acquisition, responsible for comprehensively and accurately acquiring various parameters to provide decision-making basis for the control layer.

[0053] It mainly includes: Distributed temperature sensors: comprising three types of temperature sensors, namely, NTC sensors with built-in battery cells (collecting the temperature of individual battery cells, with an accuracy of ±0.5℃), ambient temperature sensors in the vehicle cabin (collecting the ambient temperature of the vehicle), and surface-mount temperature sensors near the current-limiting resistor (collecting the temperature of the current-limiting resistor, with an accuracy of ±1℃); Current sensors: using an onboard shunt to collect the total charging current, with an accuracy of ±1%; Voltage acquisition chips: using a 16-bit AD chip to collect voltage parameters such as the total battery voltage, individual cell voltage equalization, and charging voltage, ensuring high accuracy in voltage acquisition.

[0054] The control layer is the core decision-making unit of the system, responsible for processing, analyzing, and making decisions on the parameters collected by the sensing layer, and sending control commands to the execution layer. It mainly includes: a 32-bit MCU: serving as the control core, with a main frequency ≥100MHz, supporting fast PWM output and interrupt response, capable of quickly processing complex control algorithms and real-time data, ensuring a system response speed ≤10ms; a filtering module: implementing moving average filtering and outlier removal functions to eliminate high-frequency noise interference; a parameter correlation model construction module: constructing a correlation model between parameters such as cell temperature and ambient temperature to determine abnormal states; a graded threshold decision module: based on temperature graded thresholds, determining whether to trigger current limiting control and selecting the initial current limiting strategy; a dual-mode control module: implementing switching control between resistor current limiting mode and pulse current limiting mode, dynamic adjustment of PWM duty cycle, and smooth transition of mode revert; and a fault diagnosis module: implementing multi-level fault diagnosis functions such as hardware self-test and dual-mode failure detection, providing a basis for safe disconnection.

[0055] The execution layer is responsible for receiving instructions from the control layer and executing specific current-limiting actions; it is the implementation unit for the control method. It mainly includes: a charging main MOSFET: withstand voltage ≥80V, on-resistance <10mΩ, with soft-shutdown function, used to control the on / off state of the charging main circuit; a current-limiting branch MOSFET: working in conjunction with the charging main MOSFET to control the on / off state of the current-limiting branch; a relay: used to switch current-limiting resistors R1 and R2, responding to MCU control instructions; current-limiting resistors R1 and R2: R1 is a high-resistance resistor, suitable for the extremely low temperature environment T1; R2 is a low-resistance resistor, suitable for the low temperature environment T2, both materials meeting the maximum withstand temperature requirement of 85℃.

[0056] The communication layer is responsible for internal data transmission and external fault alarms, ensuring real-time feedback of system status and timely notification of abnormal situations. It mainly includes: a CANFD bus with a transmission rate ≥2Mbps, used for real-time data transmission between the sensing, control, and execution layers, as well as reporting battery status and current limiting control status to the vehicle controller; and a fault alarm module containing a buzzer and a remote push unit. When the system detects a fault or abnormality, the buzzer emits a local alarm, and simultaneously, the alarm information is sent to the vehicle management platform or user terminal via the remote push unit, facilitating timely troubleshooting and handling of faults.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for intelligent current limiting control of vehicle-mounted sodium-ion batteries, characterized in that, Includes the following steps: Step 1, Parameter Acquisition and Preprocessing: Collect core parameters of the battery cell, charging status parameters, and environmental and hardware status parameters through a distributed acquisition module. Perform filtering and outlier removal preprocessing on the collected data to eliminate high-frequency noise and establish a parameter correlation model. Step 2, Current Limiting Trigger and Initial Strategy Selection: When the BMS confirms that the battery is in an effective charging stage and the cell temperature is less than or equal to the preset low temperature threshold T2, current limiting control is triggered; the resistor current limiting main mode is started first, and the corresponding resistance value current limiting resistor is selected according to the temperature level. Before starting, hardware self-test is performed, and if there is an abnormality, it jumps to the pulse current limiting protection mode. Step 3, Dual Current Limiting Mode Switching and Redundancy Control: In resistor current limiting mode, the main charging MOSFET is turned off and the current limiting branch MOSFET is enabled to monitor the temperature of the current limiting resistor in real time; when the preset switching conditions are met, it switches to pulse current limiting mode, and the main charging MOSFET is controlled by PWM signal to limit the current in pulse mode and the PWM parameters are dynamically adjusted; when the back-off conditions are met, it smoothly switches back to resistor current limiting mode. Step 4, Fault Coverage and Safety Cut-off: In the event of a dual-mode failure scenario, immediately shut down the relevant MOSFETs and lock the charging function; Step 5, Current Limiting Exit: When any exit condition such as temperature, state switching, or SOC reaches the standard is met, current limiting control will exit and normal charging will resume.

2. The intelligent current limiting control method for vehicle-mounted sodium-ion batteries according to claim 1, characterized in that, In step 1: The core parameters of the battery cell include individual cell temperature, total voltage, individual cell voltage balance, SOC, and SOH. The charging status parameters include total charging current and charging voltage; The environmental and hardware status parameters include the vehicle ambient temperature, the current limiting resistor temperature, and the charging main MOSFET junction temperature. The sampling frequency is ≥100Hz, and the filtering method is moving average filtering.

3. The intelligent current limiting control method for vehicle-mounted sodium-ion batteries according to claim 1 or 2, characterized in that, The judgment logic of the parameter association model in step 1 is as follows: when the temperature difference between the cell temperature and the ambient temperature is ≥5℃, the heat dissipation is judged to be abnormal.

4. The intelligent current limiting control method for vehicle-mounted sodium-ion batteries according to claim 1, characterized in that, In step 2: The temperature grading is set as T1≤-20℃, T2 is-20℃~0℃, and T0>0℃. No current limiting is required under the T0 condition. The BMS confirms that the battery is in an effective charging phase by checking the current direction and the generator wake-up signal. Hardware self-test includes MCU detection of whether the current limiting resistor has a continuity without open / short circuits and whether the MOSFET drive signal of the current limiting circuit is normal; In resistor current limiting mode, T1 corresponds to high resistance R1, and T2 corresponds to low resistance R2. The current limiting resistor is switched by the relay controlled by the MCU.

5. The intelligent current limiting control method for vehicle-mounted sodium-ion batteries according to claim 1, characterized in that, In step 3: Soft shutdown is achieved by gradually reducing the gate voltage of the charging main MOSFET through the driving circuit. In the current-limiting resistor mode, the maximum withstand temperature Tr_max of the resistor is set. Tr_max is determined to be 85℃ based on the temperature resistance rating of the current-limiting resistor material. This mode is maintained when Tr≤Tr_max-10℃, and when Tr_max-10℃<Tr<Tr_max, the BMS issues an overheat warning for the resistor.

6. The intelligent current limiting control method for vehicle-mounted sodium-ion batteries according to claim 1 or 5, characterized in that, In step 3: The trigger condition for switching to pulse current limiting mode is that the temperature of the current limiting resistor Tr ≥ Tr_max, or the current limiting resistor is short-circuited, causing the current to exceed 120% of the safety threshold I_safe. In pulse current limiting mode, the PWM pulse period is fixed at 10ms, and the duty cycle D = I_target / I_peak. I_target is the low-temperature safe charging current obtained by looking up a table based on SOC and temperature, and I_peak is the peak current during a single turn-on and does not exceed I_safe.

7. The intelligent current limiting control method for vehicle-mounted sodium-ion batteries according to claim 6, characterized in that, The dynamic adjustment rule for the PWM duty cycle is as follows: when the cell temperature rises close to T0, the SOC increases to ≥80%, or the current limiting resistor temperature drops to Tr≤Tr_max-20℃, the duty cycle D is gradually increased. Conversely, gradually decrease the duty cycle D.

8. The intelligent current limiting control method for vehicle-mounted sodium-ion batteries according to claim 1 or 5, characterized in that, In step 3, the mode switching condition is Tr≤Tr_max-20℃ and lasts for 3s. During the switching, the current fluctuation is ≤5%I_target by gradually changing the PWM duty cycle.

9. The intelligent current limiting control method for vehicle-mounted sodium-ion batteries according to claim 1, characterized in that, The dual-mode failure scenarios in step 4 include: In resistor-limited current mode, the current exceeds 1.5 × I_safe for 50ms. In pulse current limiting mode, the PWM output is abnormal or the current continues to exceed 1.5×I_safe for 50ms. The voltage of a single cell exceeds the upper limit voltage or the temperature rises by ≥5℃ / s.

10. A vehicle-mounted sodium-ion battery intelligent current limiting control system, used to implement the vehicle-mounted sodium-ion battery intelligent current limiting control method as described in any one of claims 1-9, characterized in that, include: The sensing layer includes distributed temperature sensors and current sensors. The distributed temperature sensors include NTC sensors with built-in batteries, cabin ambient temperature sensors, and surface-mount temperature sensors near the current-limiting resistor. The current sensors are onboard shunts. The control layer includes a 32-bit MCU, a filtering module, a parameter correlation model construction module, a hierarchical threshold decision module, a dual-mode control module, and a fault diagnosis module. The execution layer includes the main charging MOSFET, the current-limiting branch MOSFET, the relay, and the current-limiting resistors R1 and R2. The communication layer includes a CANFD bus and a fault alarm module containing a buzzer and a remote push unit.

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