Railway vehicle lithium battery management system
By adopting a distributed BMS hardware architecture and layered software design, the problems of high-voltage isolation and data processing reliability in the battery management system of rail transit vehicles are solved, realizing a high-safety and low-cost battery management system suitable for lithium battery management in railway vehicles.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA ACADEMY OF RAILWAY SCI CORP LTD
- Filing Date
- 2025-12-15
- Publication Date
- 2026-05-01
AI Technical Summary
Existing rail transit vehicle battery management systems have shortcomings in high-voltage isolation, data processing reliability, and software portability, which makes it impossible to correctly determine the status of the on-board power battery when the system fails, affecting vehicle safety and reliability.
The system adopts a distributed BMS hardware architecture, including a battery cluster management unit and a battery pack management unit. Data interaction between multiple BMS slave boards and the main board is realized through daisy-chain isolated communication units. Combined with a layered software architecture and an embedded real-time operating system, data acquisition and system reliability are improved.
It achieves highly reliable and safe battery management, ensuring that the battery system can still operate normally in the event of a failure, reducing development costs and improving the adaptability of hardware platforms.
Smart Images
Figure CN121964892A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of safety monitoring technology for rail transit vehicles, specifically to a lithium battery management system for railway vehicles. Background Technology
[0002] With the rapid development of rail transit, lithium battery technology, as an efficient and clean energy supply method, is being further applied. The design and optimization of its systems have become key factors in ensuring battery performance and the safe operation of vehicles. Compared to general electric vehicles, the unique characteristics of rail transit present a series of challenges and difficulties in the design of lithium battery systems.
[0003] As a highly automated field with extremely high safety requirements, rail transit places higher demands on the performance and stability of its Battery Management System (BMS). In the complex rail environment, the BMS needs to accurately monitor battery status and make appropriate adjustments in real time to ensure the safe and reliable operation of the battery system. Furthermore, the complexity and scale of railway vehicle battery systems are significantly greater than those in electric vehicles, requiring the BMS to effectively handle tasks such as the acquisition, transmission, processing, and control of large-scale data.
[0004] Batteries, serving as both the power source and energy storage device for rail transit vehicles, generally have a higher voltage level than electric vehicles. Electric vehicle battery systems typically operate at around 300-400V, while rail transit vehicles typically operate at 600-1000V. Furthermore, traditional urban rail transit vehicles are connected to the electric traction network via converters, and the voltage level of the electric traction network is generally very high (DC 750V or DC 1500V). In addition, compared to electric vehicles, the high-voltage components connected to the BMS in rail transit vehicles generally include not only the power battery system but also an auxiliary power system directly connected to the traction power grid and the main traction system. This is because the auxiliary power system provides 110V power to the BMS via DC / DC, and the energy storage battery system also provides power to the traction system via DC / AC under certain operating conditions. Therefore, compared to existing BMS technology in the electric vehicle field, rail transit BMS needs to fully consider high-voltage isolation.
[0005] Currently, the mainstream architectures of electric vehicle battery management systems (BMS) are mainly divided into two types: master-slave and integrated master-slave architectures. Both architectures collect individual battery voltage and temperature information through a front-end measurement module, transmit it to the master control module via an internal CAN bus or isolated SPI bus, and after completing calculations and logical judgments, send equalization commands to the front-end detection module, while simultaneously interacting with the vehicle controller and charger. In practical vehicle operation, the shortcomings of this architecture have gradually become apparent. The main issue is that if any link in the entire battery management system malfunctions or malfunctions, the system will be unable to accurately determine the actual state of the on-board power battery. High reliability and high safety are the main goals pursued in the development of battery systems. The safe use of the power battery directly affects the safety of the vehicle, and the electric vehicle battery management system is the core component for monitoring the state of the on-board power battery and ensuring its safe use. Designing and developing a battery management system with high reliability, high safety, and a robust architecture plays a crucial role in improving the overall safety and reliability of railway vehicles.
[0006] With the increasing performance requirements of railway vehicles for Battery Management Systems (BMS), implementing a battery management system means a significantly larger amount of code. Currently, the main program of a foreground / background-based battery management system takes approximately 10ms to run once, and the numerous interrupt service functions introduce considerable uncertainty into task execution. Furthermore, this development approach results in strong coupling between software and hardware platforms, making it impossible to port and reuse software functions across different hardware platforms. To address this issue, major equipment manufacturers and suppliers in the global automotive industry jointly established the Automotive Open System Architecture (AUTOSAR) consortium, aiming to simplify the joint development of automotive electronic software. However, in practical applications, the AUTOSAR development toolchain is expensive, and vendors providing the AUTOSAR development toolchain and underlying software are scarce. Summary of the Invention
[0007] To address at least some of the aforementioned technical problems, embodiments of this application provide a lithium battery management system for railway vehicles.
[0008] This application provides a railway vehicle lithium battery management system, comprising:
[0009] The battery cluster management unit includes a microcontroller and a power supply circuit, a total current detection circuit, a total voltage detection circuit, a communication interface circuit, an input detection circuit, and an output control circuit connected to the microcontroller.
[0010] Multiple battery pack management units, each battery pack management unit including a battery monitoring chip, the battery monitoring chip being directly connected to a battery cell for voltage detection, and the battery monitoring chip being connected to a temperature detection circuit for temperature monitoring;
[0011] A daisy-chain isolated communication unit is provided, with one end connected to the battery cluster management unit and the other end connected in series to the battery monitoring chips of multiple battery pack management units to form a complete daisy-chain communication network.
[0012] In some embodiments, the communication interface circuit includes a CAN communication circuit, an RS485 communication circuit, an Ethernet interface circuit, an isoSPI interface circuit, and a 4-20mA current loop hardwired interface, wherein the 4-20mA current loop hardwired interface serves as a redundant backup communication interface for the CAN communication circuit.
[0013] The microcontroller is connected to the total voltage detection circuit and the total current detection circuit through the ADC interface, to the CAN communication circuit and the RS485 communication circuit through the UART interface, to the Ethernet interface circuit through the SPI interface, and to the input detection circuit and the output control circuit through the GPIO interface.
[0014] The daisy-chain isolated communication unit includes an isoSPI transceiver, a signal transformer, and differential lines. The isoSPI transceiver is connected to another SPI interface of the microcontroller. The differential output of the isoSPI transceiver is connected to the non-isolated side of the signal transformer. The isolated side of the signal transformer is connected to the differential lines. The differential lines are connected in series with the battery monitoring chips of each battery pack management unit.
[0015] In some embodiments, the battery monitoring chip is an LTC6804 chip, and the LTC6804 chip is directly connected to a plurality of series-connected battery cells in at least one battery pack for monitoring the voltage of each battery cell.
[0016] In some embodiments, both the total voltage detection circuit and the total current detection circuit employ Hall sensors, and the microcontroller samples the total current at a sampling frequency of not less than 20 kHz.
[0017] In some embodiments, the temperature detection circuit includes a negative temperature coefficient thermistor with a measurement range of -40°C to 130°C; the battery monitoring chip acquires the voltage signal of the thermistor through its GPIO interface to calculate the temperature.
[0018] In some embodiments, the input detection circuit uses a linear optocoupler for electrical isolation, and the output control circuit uses a relay for electrical isolation, to adapt to the 110VDC power supply environment of rail transit vehicles.
[0019] In some embodiments, the power supply circuit includes an input filter circuit, a reverse polarity protection diode, and a power conversion module connected in sequence, for converting the 110V DC power of the vehicle auxiliary power supply into the +5V and ±15V power required by the railway vehicle lithium battery management system.
[0020] In some embodiments, the microcontroller is specifically an STM32F407ZET6 chip, whose core is an ARM Cortex-M4.
[0021] This application provides a method for managing lithium batteries in railway vehicles. Based on the railway vehicle lithium battery management system described in any of the above embodiments, the method includes:
[0022] The battery monitoring chip in the battery pack management unit collects the voltage and temperature signals of each battery cell.
[0023] The voltage and temperature signals are transmitted to the battery cluster management unit in the form of differential isolation signals through the daisy-chain isolated communication unit.
[0024] The total voltage and total current of the battery system are collected through the total voltage detection circuit and the total current detection circuit of the battery cluster management unit.
[0025] In the microcontroller of the battery cluster management unit, SOC estimation based on the ampere-hour integration method is performed, and multi-level fault diagnosis is performed based on the voltage, temperature and current information. When a fault is diagnosed, alarm, current limiting or disconnection of the charging and discharging circuit is performed according to the preset protection strategy.
[0026] In some embodiments, the microcontroller creates and schedules multiple tasks, which include at least a voltage acquisition task, a current acquisition task, a temperature acquisition task, a fault diagnosis task, and a SOC estimation task; the multiple tasks synchronize and communicate with each other through at least one of queues, semaphores, and event flag groups.
[0027] The railway vehicle lithium battery management system and method provided in this application embodiment utilizes a master-slave BMS slave board structure to achieve data interaction between multiple BMS slave boards and the BMS main board via a daisy chain, thereby improving the reliability of the slave board data acquisition system. Through the cooperation of the battery cluster management unit and the battery pack management unit, the system achieves monitoring, control, and data exchange, while simultaneously meeting requirements for voltage withstand capability, reliability, and other aspects. Attached Figure Description
[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, 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 this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:
[0029] Figure 1 This is a schematic diagram of the structure of a railway vehicle lithium battery management system provided in an embodiment of this application.
[0030] Figure 2 This is a schematic diagram of the structure of a main control unit provided in an embodiment of this application.
[0031] Figure 3 This is a schematic diagram of the structure of a slave control unit provided in an embodiment of this application.
[0032] Figure 4 This is a schematic diagram of a system software architecture provided in an embodiment of this application.
[0033] Figure 5 This is a schematic diagram of an LTC6804 sampling circuit provided in an embodiment of this application.
[0034] Figure 6 This is a schematic diagram of a BMS total voltage sampling circuit provided in an embodiment of this application.
[0035] Figure 7 This is a schematic diagram of a total current sampling circuit provided in an embodiment of this application.
[0036] Figure 8 This is a schematic diagram of a temperature detection circuit provided in an embodiment of this application.
[0037] Figure 9 This is a schematic diagram of an input detection circuit provided in an embodiment of this application.
[0038] Figure 10 This is a schematic diagram of an output control circuit provided in an embodiment of this application.
[0039] Figure 11 This is a schematic diagram of a power input filtering circuit provided in an embodiment of this application.
[0040] Figure 12 This is a schematic diagram of a CAN communication circuit provided in an embodiment of this application.
[0041] Figure 13 This is a schematic diagram of an RS485 interface circuit provided in an embodiment of this application.
[0042] Figure 14This is an internal structure diagram of THVD1410 provided in an embodiment of this application.
[0043] Figure 15 This is a schematic diagram of an Ethernet interface circuit based on a hardware protocol stack provided in an embodiment of this application.
[0044] Figure 16 This is a schematic diagram of an isoSPI interface circuit provided in an embodiment of this application.
[0045] Figure 17 This is a schematic diagram of a data transmission mechanism provided in an embodiment of this application.
[0046] Figure 18 This is a voltage acquisition flowchart provided in an embodiment of this application.
[0047] Figure 19 This is a flowchart of a current acquisition process provided in an embodiment of this application.
[0048] Figure 20 This is a flowchart of an insulation / high voltage detection function provided in an embodiment of this application.
[0049] Figure 21 This is a flowchart of temperature acquisition provided in an embodiment of this application.
[0050] Figure 22 This is a flowchart of a fault parameter configuration provided in an embodiment of this application.
[0051] Figure 23 This is a fault diagnosis flowchart provided in an embodiment of this application.
[0052] Figure 24 This is a schematic diagram of the structure of a railway vehicle lithium battery management system provided in an embodiment of this application.
[0053] Figure 25 This is a flowchart illustrating a method for managing lithium batteries in railway vehicles, as provided in an embodiment of this application. Detailed Implementation
[0054] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the embodiments of this application will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments and their descriptions are used to explain this application, but are not intended to limit this application. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily arranged.
[0055] The terms “first,” “second,” etc., used in this document are not intended to specifically refer to order or sequence, nor are they used to limit this application; they are merely used to distinguish elements or operations described using the same technical terms.
[0056] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.
[0057] The term "and / or" as used in this document includes any or all of the items mentioned.
[0058] This application proposes a BMS hardware and software architecture based on the structure and characteristics of lithium batteries in railway vehicles. Considering the large number of power batteries in rail transit vehicles, their distribution across different areas of the vehicle body, and the space constraints imposed by the vehicle body, this application adopts a distributed BMS hardware architecture, distributing each functional unit across its respective circuit module. In conjunction with the characteristics of the hardware architecture, the BMS software architecture employs a layered design principle.
[0059] I. Hardware Architecture
[0060] like Figure 1 As shown, the distributed BMS includes a Battery Cluster Management Unit (BCU) and a Battery Module Management Unit (BMU), which can perform functions such as battery status acquisition, battery life estimation, battery energy balancing, battery fault analysis and diagnosis, battery information management, and data interaction with the container controller.
[0061] The Battery Cluster Management Unit (BCU) is the control core of the battery management system. It is responsible for monitoring the entire battery system's operation, implementing control strategies, analyzing and processing data, managing the internal CAN bus of the battery management system, and exchanging data and controlling processes with external devices such as the Traction Control Unit (TCU), display screen, and charger. The Battery Pack Management Unit (BMU), as the individual battery cell detection unit, is the most direct part for obtaining battery status information. It is mainly responsible for collecting real-time information such as battery pack voltage and temperature, while also performing automatic charge / discharge bidirectional equalization management, online detection, and fault diagnosis.
[0062] The specific functions of the Battery Cluster Management Unit (BCU) are as follows:
[0063] Total current sensing: Supports at least one total current sensing channel, providing a data basis for SOC (State of Charge) and SOF (State of Function) estimation, and is used to monitor the battery charge and discharge status.
[0064] Total voltage detection: Supports at least 2 total voltage detection channels. The open circuit voltage before the battery system is powered on is used for SOC correction. In addition, when the high voltage system is powered on, the total voltage of the battery system and the total voltage of the precharge circuit need to be monitored in real time to ensure reliable power-on of the battery system.
[0065] SOC estimation: Estimating the SOC of the battery system based on algorithms such as the ampere-hour integration method.
[0066] Communication functions include internal data transmission between the battery management system's internal BCU and various BMUs, and external communication interfaces provided to the charger, vehicle controller, and instrument cluster; including a 4-20mA current loop hardwired communication interface, which allows important battery system parameters (such as battery system SOC, total voltage, and maximum charge / discharge power) to be interacted with the TCU via hardwired communication in the event of network failure, thus improving system reliability.
[0067] Relay control output: Used to control the contactors on the main positive and main negative lines of the battery, as well as the precharge contactor. It can also be used as a hard-wired digital signal output.
[0068] Digital signal input: Used to detect fault signals of the TCU and the status of auxiliary contacts of the relays.
[0069] Fault warning: It can identify and locate faults in the battery pack, report the fault information to the whole vehicle, and also receive fault signals from external devices.
[0070] Data Processing: Analyzes and interprets data received from the BMU to complete data processing and related control strategies. It also features an integrated clock module with large-capacity storage to record fault data detected during BMS operation and the time of occurrence, facilitating system diagnostics and performance optimization.
[0071] The main functions of the Battery Pack Management Unit (BMU) include:
[0072] Individual cell voltage detection: Detects the voltage of individual battery cells, which can support different numbers of battery cells.
[0073] Temperature detection: The battery temperature is detected using a temperature sensor, and it also has a temperature sampling fault location function.
[0074] Communication Function: The BMU provides a communication interface to send the collected individual cell voltage information, battery temperature information, equalization status information, and other detected status information to the BCU.
[0075] II. Software Architecture
[0076] like Figure 4 As shown, following the principle of layered design, this embodiment of the application divides the BMS software architecture into an application layer, an access interface layer, a driver layer, a hardware abstraction layer, and a real-time operating system (RTOS). This layered design can solve the problem of high development costs in different application scenarios.
[0077] Application Layer: The function of application layer tasks is to fulfill the specified requirements of BMS, mainly including information collection tasks, computing tasks, execution tasks and communication tasks.
[0078] Access Interface Layer: The access interface layer provides a dedicated interface for data exchange between tasks and between interrupts and tasks. This is a necessary form of protection in multitasking programs.
[0079] Driver layer and hardware abstraction layer: The driver layer and hardware abstraction layer further shield the hardware environment, so that the program can be adapted to different hardware platforms by only changing the hardware driver.
[0080] Real-time operating system: A real-time operating system provides functions such as task scheduling and memory management for software operation. This embodiment employs an embedded real-time operating system, which can utilize CPU resources more rationally and effectively, simplify application software design, shorten system development time, and better ensure the system's real-time performance and reliability.
[0081] Therefore, this application embodiment proposes a BMS hardware and software architecture tailored to the structure and characteristics of railway vehicle power batteries. The master-slave structure of the BMS slave boards enables data interaction between multiple BMS slave boards and the BMS main board via a daisy chain, improving the reliability of the slave board data acquisition system. This is achieved through the main control unit (see...). Figure 2 ) and slave control unit (see Figure 3 The collaboration between the BMS and the host computer enables monitoring, control, and data exchange of the battery system, while meeting design requirements in terms of voltage resistance, reliability, and other aspects. The BMS can utilize a 32-bit microprocessor platform, offering advantages such as high integration, strong processing power, and abundant expansion interfaces. Furthermore, the BMS can communicate with a host computer via a CAN bus, allowing the host computer to monitor, diagnose, and configure parameters of the lithium battery system through service software.
[0082] The following detailed description of the railway vehicle lithium battery management system and method provided in this application is based on a specific embodiment.
[0083] I. Hardware Circuit Structure
[0084] 1. High-voltage isolation
[0085] When designing the BMS hardware circuit, different high-voltage isolation circuits were designed according to the circuits of different modules.
[0086] In the power input circuit, the BMS employs an integrated isolation voltage module. Individual cell voltage and temperature detection circuits are directly connected to the energy storage battery system, and their isolation from the low-voltage section is achieved through magnetic coupling. Additionally, in the communication circuit, magnetic coupling isolation is used to ensure communication reliability. For the digital input and output circuits, input signals are isolated using linear optocouplers, while output signals, including those for high-voltage switches and cooling fans, are isolated via relays. In the overall voltage detection circuit, a voltage Hall sensor eliminates the electrical connection between the BMS circuit board and the energy storage battery system, thus achieving effective isolation between the high and low voltage sections.
[0087] 2. Electromagnetic compatibility
[0088] This application focuses on electromagnetic compatibility (EMC) issues at the BMS circuit board level, and conducts EMC design from three aspects: component selection, circuit design, and PCB routing.
[0089] (1) Selection of components
[0090] When conditions permit, choose surface-mount components whenever possible. When selecting specific components, try to choose those with low EMI (electromagnetic interference) sensitivity and low radiation.
[0091] (2) Circuit design
[0092] Adding decoupling capacitors to the power supply points of active devices, and placing them as close as possible to the power pins, effectively suppresses high-frequency switching noise generated during power switching, guiding the noise to ground to reduce its conduction on the circuit board. Bypass capacitors can act as high-frequency bypass devices to reduce the transient current demand of the power module. Transmitting signals in the form of current effectively prevents interference signals from entering during long-distance transmission, improving the accuracy of signal transmission. Using optocoupler isolation and magnetic coupling isolation technologies disconnects the electrical connection between the isolated parts, preventing interference signals from interfering with each other.
[0093] (3) PCB routing
[0094] To minimize grounding impedance, the grounds of multiple power supplies in the system are first separated and then converged to a single grounding point. Where there is no wiring, grounding copper can be used to enhance shielding and decoupling capabilities. In this embodiment, the circuit board uses a four-layer layout, effectively separating the power and ground layers, with ground planes on each layer. Routing is done as directly as possible, using 45-degree or 135-degree bends, and avoiding routing under crystal oscillators and other noise-sensitive devices.
[0095] 2. Detection circuit
[0096] (1) Individual cell voltage detection
[0097] In this embodiment, the BMU (Battery Controller Unit) can be a Linear Technology LTC6804 chip specifically designed for battery monitoring, capable of measuring the voltage of up to 12 series-connected batteries. In this embodiment, the BCU is connected to three transformer-isolated daisy-chain LTC6804 chips via SPI communication, allowing simultaneous acquisition of the voltage of 36 individual battery cells. The block diagram of the LTC6804 sampling circuit is shown below. Figure 5 As shown.
[0098] (2) Total voltage detection
[0099] BMS total voltage sampling circuit, such as Figure 6 As shown, the current signal LEM_Iin output from the secondary side is sampled by high-precision resistors R1 and R2 and converted into a voltage signal. After RC filtering and operation amplifier, it is sent to the MCU's AD port. At the same time, the reference voltage circuit provides a reference voltage to the reference voltage. After AD sampling and calibration, the voltage value can be obtained.
[0100] (3) Total current detection
[0101] The total current is measured using a current Hall sensor conforming to railway industry standards. The ripple frequency in the battery charging current is between 4kHz and 8kHz. According to Shannon's sampling theorem, the sampling frequency must be at least twice the highest frequency of the sampled signal. Therefore, in this embodiment, a sampling frequency of 20kHz is selected to sample the total battery current. The total current sampling circuit used in this embodiment is as follows: Figure 7 As shown.
[0102] (4) Temperature detection
[0103] In this embodiment, a thermistor (NTC) is used as the temperature sensor, with a measurement range of -40℃ to 130℃ and a measurement accuracy of ±1℃. The thermistor selected in this embodiment is a negative temperature type, meaning its resistance decreases as temperature increases. The resistance-temperature characteristic can be expressed by the following formula:
[0104] (1)
[0105] In the formula, and These represent temperatures at T and T, respectively. The resistance of the thermistor is B, which is the B value of the thermistor. Its calculation formula is shown in the following formula (2), where R1 and R2 represent the resistance of the NTC at T1=25℃ and T2=85℃, respectively.
[0106] (2)
[0107] Because the temperature detection is directly connected to the high-voltage battery system, the temperature acquisition circuit and the CPU must be isolated. To save costs and simplify the design, this embodiment uses the general-purpose GPIO (with ADC input function) of the LTC6804 to acquire the temperature signal. Each LTC6804 is configured with two temperature sampling circuits. The temperature detection circuit is as follows: Figure 8 As shown.
[0108] 3. CPU and peripheral circuits
[0109] The BCU uses STMicroelectronics' STM32F407ZET6 processor. In this embodiment, the battery management system uses the STM32F407ZET6 microcontroller from STMicroelectronics, whose core uses ARM's 32-bit Cortex-M4 processor with a clock speed of up to 168MHz. It integrates 1MB of FLASH and 192KB of SRAM on-chip.
[0110] 4. Input detection circuit
[0111] Input detection is generally divided into isolated and non-isolated detection methods. Rail transit power supply is 110VDC, while automotive power supply is generally 12 / 24VDC. To achieve compatible design, input detection requires electrical isolation. Input detection employs methods such as... Figure 9 The isolation and testing method shown.
[0112] 5. Output control circuit
[0113] Output control is generally divided into relay control and high-side chip control. Due to the different power supply voltages of rail transit and automobiles, electrical isolation is required for compatible design. Furthermore, high-side chips currently available only have a 24V or 48V power supply voltage range, which is unsuitable for 110V rail power supply systems. Therefore, output control employs... Figure 10 The relay control method shown.
[0114] 6. Power supply circuit
[0115] The BCU's power supply circuit consists of two parts: a 5V power supply for the system and a ±15V power supply for the Hall sensor. Because the battery management system uses the vehicle's auxiliary power supply (110V), to simplify the design and ensure system reliability, this embodiment employs two railway-certified power conversion modules: RP08-11005SAW and ESBM110150-DP-F20. Both power modules feature input undervoltage protection and output overvoltage, overcurrent, and short-circuit protection. Figure 11 The diagram shows the filtering circuit at the input front end of the power module. Adding a reverse connection protection diode D2 at the power input can effectively prevent damage to the BMS caused by reverse connection of the power line on site.
[0116] 7. Communication circuits
[0117] In this embodiment, the main control unit is designed with rich communication interface circuits, including CAN communication, RS485 communication and 4-20mA current loop hard-wired signal.
[0118] (1) CAN communication circuit
[0119] In this embodiment, the CAN transceiver used is the Texas Instruments SN65HVD233 high-speed CAN transceiver chip. The CAN communication circuit is as follows: Figure 12 As shown, a 5V power supply is used, and the TXD and RXD pins are connected to the transmit and receive pins of the CAN controller inside the main control chip, respectively.
[0120] (2) RS485 communication circuit
[0121] RS485 communication circuit, such as Figure 13 As shown. The RS485 bus supports both half-duplex and full-duplex transmission, using differential signal transmission, and is not affected by ground level. The RS485 transceiver can be the TI THVD1410, with a maximum transmission rate of 2.5 Mbps. Its pin information and internal structure diagram are shown below. Figure 14 As shown.
[0122] (3) Ethernet interface
[0123] Ethernet functionality is implemented through a hardware protocol stack, such as Ethernet interface circuits based on the hardware protocol stack. Figure 15 As shown, the MCU connects to the W5500 via an SPI interface. The W5500 converts the SPI signal into an Ethernet differential signal, which is then connected to a signal transformer for electrical isolation.
[0124] (4) isoSPI interface
[0125] The MCU's SPI signal is converted by an isoSPI transceiver and then isolated by a signal transformer to obtain an isoSPI differential signal, such as... Figure 16 As shown, the isoSPI transceiver used is the LINEAR LTC6820, with a communication rate of 1Mbps, excellent EMC performance, and compliance with the AEC-Q100 automotive standard.
[0126] 8. Master-slave communication technology based on daisy chain
[0127] In this embodiment, a daisy-chain master-slave communication technology is used. Only the microcontroller is retained on the BMS motherboard. The original slave board is simplified to a small board that simply revolves around the AFE chip. The information collected by the AFE is directly transmitted to the motherboard through differential isolation signals.
[0128] II. Software Solution
[0129] In the embedded field, embedded real-time operating systems are being used more and more widely. Using an embedded real-time operating system (RTOS) allows for more rational and efficient use of CPU resources, simplifies application software design, shortens system development time, and better ensures system real-time performance and reliability.
[0130] 1. Operating System Design
[0131] (1) Source file porting
[0132] In this embodiment, a real-time operating system based on FreeRTOS is selected. The FreeRTOS Kernel file includes functions such as coroutines, event groups, linked lists, queues, tasks, software timers, and stream buffers. The specific porting process is as follows:
[0133] The interrupt service function xPortSysTickHandler for the tick clock provides a time base for FreeRTOS operation. If a higher-priority task becomes ready, xPortPendSVHandler is woken up to complete the task switch.
[0134] The vPortSVCHandler function loads the contents of the current task control block into the CPU register to start the first task, without needing to push the values of the CPU register onto the stack.
[0135] The `xPortPendSVHandler` function is the core component for OS scheduling, specifically context switching. This function is called by `xPortSysTickHandler` and when manual task switching is required.
[0136] (2) Task communication method
[0137] Based on object-oriented principles, global variables are encapsulated and protected by critical sections. To ensure that the execution of critical section code is not interrupted, interrupts must be disabled before entering the critical section, and immediately enabled after the critical section code completes execution, or mutual exclusion protection must be implemented for global variables. Finally, this is encapsulated into an external interface function, which external programs call to access global variables. To this end, this application proposes a data transmission mechanism such as... Figure 17 As shown.
[0138] (3) Task synchronization method
[0139] Mutexes and event flag groups are used to synchronize tasks and interrupts. The software uses semaphores and event flag groups to synchronize tasks. When a task acquires a mutex, its priority is temporarily raised to the highest level to ensure that it can be executed first. After execution, the mutex is released in time to restore the original priority.
[0140] (4) Task allocation based on FreeRTOS
[0141] Based on the development goals, the system is divided into multiple tasks, as shown in Table 1 below. The priority of the tasks is allocated according to the real-time requirements and the principle of efficient RAM utilization.
[0142] Table 1. Task information based on FreeRTOS
[0143]
[0144] 2. Voltage detection function
[0145] The voltage acquisition process of BMS is as follows: Figure 18 As shown, the acquisition is completed by the AD chip, and the controller parses and processes the acquired data, including filtering and anomaly handling.
[0146] (1) Voltage acquisition
[0147] 1) A voltage acquisition cycle is performed every 3ms.
[0148] 2) After every 6 rounds of sampling, the controller performs data processing once.
[0149] 3) When batteries are connected across different cells, the voltage across the cells needs to be processed.
[0150] (2) Troubleshooting
[0151] 1) After filtering, if the voltage is normal, it is uploaded to the controller data area for use by other tasks.
[0152] 2) If the sampled voltage is 0 or greater than 5V, the sampled chip is considered faulty and should be re-initialized. If the sampled chip is still considered faulty after 10 consecutive initializations, the system should be powered down.
[0153] (3) If the sampled voltage is between 0-5V, but adjacent voltages suddenly increase and suddenly decrease respectively, it is determined that the sampled cable has come loose. Power off the system.
[0154] (4) When the data acquisition is normal, determine whether there is a high voltage, undervoltage, or differential voltage fault in the system based on the highest and lowest values of the individual units and the difference between the highest and lowest values. Perform protection processing according to the parameter configuration.
[0155] 3. Current detection function
[0156] The current acquisition process of BMS is as follows: Figure 19 As shown, the acquisition is completed by the AD chip, and the controller parses and processes the acquired data, including filtering and anomaly handling.
[0157] (1) Current acquisition
[0158] 1) Current is sampled every 5ms.
[0159] 2) After every 8 rounds of data collection, the controller performs a current processing operation.
[0160] (2) Troubleshooting
[0161] 1) The controller converts the acquired AD value according to the current sensor range. If the value exceeds the range, it reports a sensor acquisition fault.
[0162] 2) If the current is normal, upload it to the controller data area for use in other tasks.
[0163] 3) If the current is too high, implement protection measures according to the parameter configuration.
[0164] 4. Insulation / High Voltage Detection Function
[0165] The insulation / high voltage detection function process is as follows: Figure 20 As shown, the specific process is as follows:
[0166] (1) A circuit combining a balanced bridge and an unbalanced bridge is used, all switches are open, and the voltage at the sampling point is the total battery voltage V0.
[0167] (2) When switch S1 is closed and S2 and S3 are open, and there is no leakage resistance to ground at the positive and negative terminals of the battery, or when the leakage resistance of the positive and negative terminals is the same, the detected V1 should be the same as when all switches are open.
[0168] (3) When switches S1 and S2 are closed and S3 is open, the voltage V2 that breaks the balance bridge is obtained.
[0169] (4) With switches S1 and S3 closed and S2 open, the voltage V3 that breaks the balance bridge is obtained.
[0170] (5) Check for total voltage acquisition faults by comparing V0 with the cumulative value of individual unit voltages. Check for high voltage acquisition faults by converting V1, V2, V3 with voltage divider resistors.
[0171] 5. Temperature detection function
[0172] Temperature acquisition for the energy storage BMS is performed by an AD chip, and the process is as follows: Figure 21 As shown, the main controller parses and processes the collected data, including filtering and anomaly handling.
[0173] (1) Temperature acquisition
[0174] 1) Temperature data is collected every 3ms, with 4 temperature sensors collected each time.
[0175] 2) After every 4 rounds of sampling, all temperature data is collected, and the controller performs one data processing operation.
[0176] (2) Troubleshooting
[0177] 1) If the temperature is normal, upload it to the controller data area for use by other tasks.
[0178] 2) If the temperature reading fails, or the collected temperature is below -50℃ or above 125℃, it is determined that the ribbon cable has come loose.
[0179] 3) A first-order filtering scheme is adopted, and the temperature change value is increased by only 50% of the actual change value each time.
[0180] 4) Determine if there are high temperature, low temperature, temperature difference, or temperature rise faults based on the unit temperature. If there are faults, handle them according to the parameter configuration.
[0181] 6. Fault diagnosis function
[0182] (1) Fault parameter configuration
[0183] The fault parameter configuration process is as follows: Figure 22 As shown, the parameter area is divided into positive code area, negative code area, and backup area.
[0184] 1) After power-on reset, the stored parameters are verified. If the verification fails, the default values are reset.
[0185] 2) When storing parameters, the parameter range is checked, and the parameters are stored in the verification area and backup area in positive and negative code form.
[0186] (2) Fault diagnosis process
[0187] Fault diagnosis process as follows Figure 23 As shown, the fault levels are divided into three levels, with level three being the highest and level one the lowest. Each level of fault can be configured with different handling schemes, including alarm display, current detection, and disconnection of the charging / discharging circuit. Fault diagnosis is performed every 100ms, and the diagnostic items include: high voltage, low voltage, charging overcurrent, discharging overcurrent, battery high temperature, battery low temperature, voltage difference, temperature difference, low SOC, temperature rise, insulation, temperature sensing cable detachment, voltage cable detachment, and communication failure.
[0188] 7. Research on Host Computer Service Software Solution
[0189] The battery management system of the lithium battery system can communicate with the host computer through the diagnostic CAN port. The host computer can monitor, diagnose and configure the parameters of the lithium battery system through service software.
[0190] (1) Software main interface
[0191] The main interface displays key parameters and fault statuses of the lithium battery system. Statistical information on the main interface includes the lithium battery system's state of charge (SOC), voltage, and current; fault information includes system fault status, with each fault status indicated by a red light to indicate the presence of the fault and a green light to indicate the absence of the fault.
[0192] (2) Detailed information
[0193] The detailed information interface displays detailed information for each BMU under a battery cluster. The detailed information BMU interface includes information such as the status, temperature, and remaining power of the corresponding battery pack.
[0194] (3) Alarm information
[0195] The alarm information interface displays alarms from the lithium battery system. The interface includes the system alarm status; if a fault alarm exists, the fault level is displayed; otherwise, it displays "normal."
[0196] (4) Parameter settings
[0197] The parameter setting interface allows you to configure lithium battery system parameters and battery protection limits.
[0198] The railway vehicle lithium battery management system and method proposed in this application have at least the following advantages compared to existing BMS systems:
[0199] The BMS hardware circuit proposed in this application embodiment has different high-voltage isolation circuits customized for different modules, resulting in stronger system voltage withstand capability.
[0200] The BMS multi-layer redundancy architecture proposed in this application embodiment ensures that when a component fails, another system is managed as a hot backup.
[0201] In this application embodiment, the Cortex-M4 core is used as the MCU, which enables the chip to be independently controllable;
[0202] This application's embodiments use the open-source and free real-time operating system FreeRTOS as the software kernel of the BMS development platform, and solve the problem of high development costs in different application scenarios based on layered software design.
[0203] Based on the above inventive concept, this application claims protection for a lithium battery management system and method for railway vehicles.
[0204] Figure 24 This is a schematic diagram of the structure of a railway vehicle lithium battery management system provided in an embodiment of this application. Figure 24 As shown in the embodiment of this application, a lithium battery management system for railway vehicles includes:
[0205] The battery cluster management unit 1 includes a microcontroller 1 and a power supply circuit, a total current detection circuit, a total voltage detection circuit, a communication interface circuit, an input detection circuit, and an output control circuit connected to the microcontroller.
[0206] Multiple battery pack management units 2, each battery pack management unit 2 includes a battery monitoring chip, which is directly connected to a single battery cell for voltage detection and is also connected to a temperature detection circuit for temperature monitoring.
[0207] The daisy-chain isolated communication unit 3 has one end connected to the battery cluster management unit 1 and the other end connected in series to multiple battery monitoring chips of the battery pack management unit 2 to form a complete daisy-chain communication network.
[0208] In some embodiments, the communication interface circuit includes a CAN communication circuit, an RS485 communication circuit, an Ethernet interface circuit, an isoSPI interface circuit, and a 4-20mA current loop hardwired interface, wherein the 4-20mA current loop hardwired interface serves as a redundant backup communication interface for the CAN communication circuit; the microcontroller is connected to the total voltage detection circuit and the total current detection circuit via an ADC interface, to the CAN communication circuit and the RS485 communication circuit via a UART interface, to the Ethernet interface circuit via an SPI interface, and to the input detection circuit and the output control circuit via a GPIO interface; the daisy-chain isolated communication unit includes an isoSPI transceiver, a signal transformer, and differential lines. The isoSPI transceiver is connected to another SPI interface of the microcontroller, the differential output terminal of the isoSPI transceiver is connected to the non-isolated side of the signal transformer, the isolated side of the signal transformer is connected to the differential lines, and the differential lines are sequentially connected in series to the battery monitoring chips of each battery pack management unit.
[0209] In some embodiments, the battery monitoring chip is an LTC6804 chip, and the LTC6804 chip is directly connected to a plurality of series-connected battery cells in at least one battery pack for monitoring the voltage of each battery cell.
[0210] In some embodiments, both the total voltage detection circuit and the total current detection circuit employ Hall sensors, and the microcontroller samples the total current at a sampling frequency of not less than 20 kHz.
[0211] In some embodiments, the temperature detection circuit includes a negative temperature coefficient thermistor with a measurement range of -40°C to 130°C; the battery monitoring chip acquires the voltage signal of the thermistor through its GPIO interface to calculate the temperature.
[0212] In some embodiments, the input detection circuit uses a linear optocoupler for electrical isolation, and the output control circuit uses a relay for electrical isolation, to adapt to the 110VDC power supply environment of rail transit vehicles.
[0213] In some embodiments, the power supply circuit includes an input filter circuit, a reverse polarity protection diode, and a power conversion module connected in sequence, for converting the 110V DC power of the vehicle auxiliary power supply into the +5V and ±15V power required by the railway vehicle lithium battery management system.
[0214] In some embodiments, the microcontroller is specifically an STM32F407ZET6 chip, whose core is an ARM Cortex-M4.
[0215] Based on the same inventive concept, this application also provides a method for managing lithium batteries in railway vehicles, which is based on the railway vehicle lithium battery management system described in any of the above embodiments.
[0216] Figure 25 This is a flowchart illustrating a method for managing lithium batteries in railway vehicles, as provided in an embodiment of this application. Figure 25 As shown, the method includes:
[0217] S1. The voltage and temperature signals of each battery cell are collected through the battery monitoring chip of the battery pack management unit.
[0218] S2. The voltage and temperature signals are transmitted to the battery cluster management unit in the form of differential isolation signals through the daisy-chain isolated communication unit.
[0219] S3. Collect the total voltage and total current of the battery system through the total voltage detection circuit and the total current detection circuit of the battery cluster management unit;
[0220] S4. In the microcontroller of the battery cluster management unit, SOC estimation based on the ampere-hour integration method is performed, and multi-level fault diagnosis is performed based on the voltage, temperature and current information. When a fault is diagnosed, alarm, current limiting or disconnection of the charging and discharging circuit is performed according to the preset protection strategy.
[0221] In some embodiments, the microcontroller creates and schedules multiple tasks, which include at least a voltage acquisition task, a current acquisition task, a temperature acquisition task, a fault diagnosis task, and a SOC estimation task; the multiple tasks synchronize and communicate with each other through at least one of queues, semaphores, and event flag groups.
[0222] This embodiment discloses a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions, and when the program instructions are executed by a computer, the computer can perform the methods provided in the above-described method embodiments.
[0223] This embodiment provides a computer-readable storage medium storing a computer program that causes the computer to execute the methods provided in the above-described method embodiments.
[0224] 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.
[0225] 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.
[0226] 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.
[0227] 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.
[0228] In the description of this specification, the references to terms such as "an embodiment," "a specific embodiment," "some embodiments," "for example," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0229] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.
Claims
1. A lithium battery management system for railway vehicles, characterized in that, include: The battery cluster management unit includes a microcontroller and a power supply circuit, a total current detection circuit, a total voltage detection circuit, a communication interface circuit, an input detection circuit, and an output control circuit connected to the microcontroller. Multiple battery pack management units, each battery pack management unit including a battery monitoring chip, the battery monitoring chip being directly connected to a battery cell for voltage detection, and the battery monitoring chip being connected to a temperature detection circuit for temperature monitoring; A daisy-chain isolated communication unit is provided, with one end connected to the battery cluster management unit and the other end connected in series to the battery monitoring chips of multiple battery pack management units to form a complete daisy-chain communication network.
2. The railway vehicle lithium battery management system according to claim 1, characterized in that, The communication interface circuit includes a CAN communication circuit, an RS485 communication circuit, an Ethernet interface circuit, an isoSPI interface circuit, and a 4-20mA current loop hardwired interface, wherein the 4-20mA current loop hardwired interface serves as a redundant backup communication interface for the CAN communication circuit. The microcontroller is connected to the total voltage detection circuit and the total current detection circuit through the ADC interface, to the CAN communication circuit and the RS485 communication circuit through the UART interface, to the Ethernet interface circuit through the SPI interface, and to the input detection circuit and the output control circuit through the GPIO interface. The daisy-chain isolated communication unit includes an isoSPI transceiver, a signal transformer, and differential lines. The isoSPI transceiver is connected to another SPI interface of the microcontroller. The differential output of the isoSPI transceiver is connected to the non-isolated side of the signal transformer. The isolated side of the signal transformer is connected to the differential lines. The differential lines are connected in series with the battery monitoring chips of each battery pack management unit.
3. The railway vehicle lithium battery management system according to claim 2, characterized in that, The battery monitoring chip is an LTC6804 chip. The LTC6804 chip is directly connected to multiple series-connected battery cells in at least one battery pack and is used to monitor the voltage of each battery cell.
4. The railway vehicle lithium battery management system according to claim 3, characterized in that, Both the total voltage detection circuit and the total current detection circuit use Hall sensors, and the microcontroller samples the total current at a sampling frequency of not less than 20kHz.
5. The railway vehicle lithium battery management system according to claim 4, characterized in that, The temperature detection circuit includes a negative temperature coefficient thermistor, which has a measurement range of -40°C to 130°C; the battery monitoring chip acquires the voltage signal of the thermistor through its GPIO interface to calculate the temperature.
6. The railway vehicle lithium battery management system according to claim 5, characterized in that, The input detection circuit uses a linear optocoupler for electrical isolation, and the output control circuit uses a relay for electrical isolation, in order to adapt to the 110VDC power supply environment of rail transit vehicles.
7. The railway vehicle lithium battery management system according to claim 6, characterized in that, The power supply circuit includes an input filter circuit, a reverse connection protection diode, and a power conversion module connected in sequence, which are used to convert the 110V DC power of the vehicle auxiliary power supply into the +5V and ±15V power required by the railway vehicle lithium battery management system.
8. The railway vehicle lithium battery management system according to claim 7, characterized in that, The microcontroller is specifically an STM32F407ZET6 chip, whose core is an ARM Cortex-M4.
9. A method for managing lithium batteries in railway vehicles, characterized in that, Based on the railway vehicle lithium battery management system according to any one of claims 1 to 8, the method includes: The battery monitoring chip in the battery pack management unit collects the voltage and temperature signals of each battery cell. The voltage and temperature signals are transmitted to the battery cluster management unit in the form of differential isolation signals through the daisy-chain isolated communication unit. The total voltage and total current of the battery system are collected through the total voltage detection circuit and the total current detection circuit of the battery cluster management unit. In the microcontroller of the battery cluster management unit, SOC estimation based on the ampere-hour integration method is performed, and multi-level fault diagnosis is performed based on the voltage, temperature and current information. When a fault is diagnosed, alarm, current limiting or disconnection of the charging and discharging circuit is performed according to the preset protection strategy.
10. The method according to claim 9, characterized in that, The microcontroller creates and schedules multiple tasks, which include at least a voltage acquisition task, a current acquisition task, a temperature acquisition task, a fault diagnosis task, and a SOC estimation task; the multiple tasks synchronize and communicate with each other through at least one of the following methods: queues, semaphores, and event flag groups.