Energy storage bms parallel communication bus terminal resistance automatic matching circuit, method and system

Abstract

The present application relates to the technical field of battery management system, and provides a kind of energy storage BMS and machine communication bus terminal resistance automatic matching circuit, method and system.To solve the problems of material waste, operation cumbersome and unreliable communication caused by traditional manual plugging terminal resistance, the circuit of the present application includes a plurality of battery management units connected in series through serial link and connected in parallel to communication bus, each unit is built-in controller, uplink and downlink serial ports, controlled switch and terminal resistance.The uplink serial port is passive monitoring, and the downlink serial port is active detection;If the controller has no received data, it is determined as the first end and the terminal resistance is connected, if there is no response, it is determined as the tail end and the terminal resistance is connected, otherwise, it remains disconnected.The method includes power-on disconnecting resistance, parallel monitoring and detection, position determination and dynamic re-matching based on address list.The present application realizes the automatic identification and access of terminal resistance, plug and play, can dynamically adapt to node changes, significantly improves the communication reliability and system usability.

Description

Technical Field

[0001] This invention relates to the technical fields of battery management systems, and in particular to an automatic matching circuit, method and system for the terminal resistor of a parallel communication bus in an energy storage BMS. Background Technology

[0002] See Figure 1 and Figure 3 In lithium battery energy storage systems, to meet high power demands, multiple battery packs are often connected in parallel, and all battery packs are centrally managed using a CAN bus or RS485 bus. To eliminate signal echo reflection, waveform distortion, and data errors caused by discontinuous line impedance in the differential bus, terminating resistors need to be connected at both the physical start and end points of the communication bus. Currently, terminating resistors (e.g., 120Ω) are typically manually inserted at both the start and end BMS. This manual method has significant technical problems in practical applications: First, BMS manufacturers cannot predict the number of battery packs connected in parallel in the final installation scenario, making it difficult to determine the number of terminating resistors to be shipped. Over-distribution leads to material waste, while under-distribution results in communication failure or data loss. Second, when increasing or decreasing the number of battery packs connected in parallel, end users must reconfirm and manually insert and remove the terminating resistors at both ends, a cumbersome and error-prone operation. Furthermore, the uncertainty introduced by manual operation can cause signal reflection due to the lack of correct terminating resistors, severely affecting communication quality and even causing communication interruptions. Summary of the Invention

[0003] To address the shortcomings of the existing technology, this invention provides an automatic matching circuit, method, and system for the terminal resistors of the parallel communication bus of an energy storage BMS. This eliminates the need for manual insertion and removal of terminal resistors at the beginning and end nodes in the traditional method, and solves problems such as BMS manufacturers' inability to predict the number of parallel devices, leading to over- or under-matching of terminal resistors; users needing to re-insert and re-plug resistors when adding or removing battery packs, which can easily cause errors; and signal reflection and communication failures caused by manual omissions in matching.

[0004] In a first aspect, the present invention provides an automatic matching circuit for the terminating resistor of a parallel communication bus in an energy storage BMS, comprising multiple battery management units cascaded sequentially via serial communication links, each of the battery management units being connected in parallel on the same communication bus via a bus interface; each of the battery management units includes a controller, an uplink serial interface, a downlink serial interface, a controlled switch, and a terminating resistor; The controlled switch is connected in series with the terminating resistor and then spans between the two differential signal lines of the communication bus; the controller is connected to the control terminal of the controlled switch and is used to control the on / off state of the controlled switch; during power-on initialization, the controlled switch is in the off state by default; the uplink serial interface is used to receive data from the upstream battery management unit and return a response to the upstream battery management unit when valid data is received; the downlink serial interface is used to send probe data to the downstream battery management unit and receive the response from the downstream battery management unit; The controller is configured to: if the uplink serial interface does not receive valid data within a first preset time period, determine that the battery management unit is the beginning of the communication bus, and control the controlled switch to close to connect the terminating resistor to the communication bus; if the downlink serial interface does not receive a valid response after sending probe data within a second preset time period, determine that the battery management unit is the end of the communication bus, and control the controlled switch to close to connect the terminating resistor to the communication bus; otherwise, determine that the battery management unit is an intermediate node and keep the controlled switch open.

[0005] In this solution, by embedding a terminating resistor and a controlled switch in each battery management unit, and utilizing the listening of the uplink serial interface and the active detection of the downlink serial interface, the controller can independently determine its physical location on the communication bus—the beginning, end, or intermediate node—and automatically control the connection and disconnection of the terminating resistor. This solution completely eliminates the need for manual insertion and removal of terminating resistors at the beginning and end nodes, resolving issues such as BMS manufacturers' inability to predict the number of parallel units, leading to over- or under-pairing of terminating resistors; users needing to re-insert resistors when adding or removing battery packs, which can easily result in errors; and signal reflection and communication failures caused by manual mismatching. It achieves plug-and-play terminating resistors, standardized mass production, and improved communication reliability.

[0006] Preferably, the controlled switch is a magnetic latching relay; the magnetic latching relay has a power-off latching characteristic. When the battery management unit it belongs to is offline and powered off, the magnetic latching relay maintains the on / off state before the power-off, thereby locking the connection state of the terminating resistor and the communication bus. In this solution, the controlled switch is a magnetic latching relay, which can utilize its power-off latching characteristic to ensure that when a battery management unit is powered off or offline, the on / off state of the terminating resistor remains unchanged. In this way, even if individual nodes in the network are offline, the existing terminating matching state on the bus will not change, avoiding misjudgment of the first and last numbers or sudden changes in bus impedance caused by switch reset, further ensuring the continuous stability of the communication bus, and supporting normal communication of the system even when nodes are offline.

[0007] Preferably, the communication bus is a CAN bus or an RS485 bus. The CAN bus or RS485 bus is directly compatible with the two mainstream differential communication standards widely used in current energy storage systems, enabling the automatic matching circuit of this invention to adapt to battery management units and external devices with different communication interfaces, thus exhibiting good versatility and applicability.

[0008] Preferably, both the uplink and downlink serial interfaces are UART full-duplex interfaces, configured with the following communication parameters: baud rate 9600bps, 8 data bits, 1 stop bit, and CRC16 checksum. The use of UART full-duplex communication in both the uplink and downlink serial interfaces, along with standardized baud rate, data bits, stop bits, and CRC16 checksum, ensures the reliability and determinism of probe and response frame transmission between adjacent battery management units, providing a stable communication foundation for the controller to accurately determine the presence and location of upstream and downstream devices.

[0009] Preferably, the first preset duration is 1 second; the second preset duration is 1 second, and the downlink serial interface sends probe data 3 times within the 1 second. Setting the first preset duration of no uplink data to 1 second and the second preset duration of no downlink response to 1 second, and sending probe data 3 times within this duration, can effectively avoid misjudgments caused by occasional communication interference or instantaneous delays while ensuring the response speed of rapid identification of the first and last nodes, thus making the location determination both real-time and anti-interference.

[0010] Preferably, the controller is further configured to: establish and maintain a real-time online address list of all battery management units within the network based on serial interaction data, and monitor the online status of each node; when the number of cascaded battery management units increases or decreases, or a node goes offline, re-execute the determination of the first and last ends and control the controlled switch according to the determination result to automatically update the on / off state of the terminal resistor. By establishing and maintaining a real-time online address list of network devices, the controller can dynamically sense the increase or decrease in the number of parallel devices or the offline state of nodes; when the topology changes, it automatically re-executes the first and last end determination and switches the on / off state of the terminal resistor, realizing a truly automatic rematching function that supports dynamic addition or removal of battery packs during system operation without any manual operation, further improving the system's flexibility and maintenance-free characteristics.

[0011] Preferably, the cascading of multiple battery management units is achieved via an 8-core twisted-pair network cable. This 8-core twisted-pair cable simultaneously transmits uplink serial signals, downlink serial signals, and communication bus signals, effectively utilizing only 5 cores and eliminating the need for external independent terminating resistors and their wiring. Each battery management unit also includes an isolation power supply and data isolation module for electrical isolation of the uplink serial interface, downlink serial interface, and bus interface. In this solution, the cascading is achieved using an 8-core twisted-pair network cable, utilizing only 5 cores to simultaneously transmit uplink serial signals, downlink serial signals, and communication bus signals, eliminating the need for external independent terminating resistors and their separate wiring. Simultaneously, the built-in isolation power supply and data isolation module provide electrical isolation for each communication interface. This solution not only simplifies on-site installation and wiring, reduces material and construction costs, but also enhances the electrical isolation between units, improves system anti-interference capability and security, and achieves integration and plug-and-play functionality.

[0012] Secondly, the present invention provides an automatic matching method for the terminating resistor of a parallel communication bus in an energy storage BMS, the method being applied to the aforementioned automatic matching circuit, comprising: Step 1: After the system is powered on, each battery management unit initializes. The controller of each battery management unit controls the controlled switch of its unit to disconnect, so that the built-in terminating resistor of the unit is disconnected from the communication bus by default. Step 2: Each battery management unit enables data listening on its uplink serial interface in parallel and sends probe data cyclically through its downlink serial interface. Step 3, Head End Determination: If the upstream serial interface of this unit does not receive valid data within a preset time period, this unit is determined to be the head end of the communication bus. The controller controls the controlled switch of this unit to close and connects the terminating resistor to the communication bus. If valid data is received, a response is sent to the upstream unit, and this unit is determined to be a non-head end. Step 4, Tail End Determination: If the downlink serial interface of this unit fails to receive a valid response after sending probe data multiple times within a preset time period, this unit is determined to be the tail end of the communication bus. The controller controls the controlled switch of this unit to close and connect the terminating resistor to the communication bus. If a valid response is received, this unit is determined to be a non-tail end. Step 5, Intermediate Node Determination: If this unit is neither determined as the beginning end in step 3 nor as the end end in step 4, then the controlled switch of this unit remains open, and the terminating resistor remains disconnected from the communication bus. Step 6, Dynamic Rematching: The controller of each battery management unit maintains the online list of network device addresses in real time. When the number of parallel battery management units increases or decreases, or when a node goes offline, steps 2 to 5 are re-executed to automatically complete the re-determination of the node position and the corresponding switching of the on / off state of the terminal resistor of this unit.

[0013] In this solution, the automatic matching method operates automatically upon power-up. It provides the entire parallel system with fully automated terminal resistor matching capabilities through a complete process: initializing and disconnecting all terminating resistors, parallel monitoring of uplink data and cyclic downlink probing, determining the start and end nodes based on communication activity and controlling switch actions, and dynamically maintaining the address list and triggering re-matching. This method requires no central master node; each battery management unit makes independent decisions, completely eliminating the tediousness and error potential of traditional manual operation. It can adaptively adjust when nodes are added, removed, or offline, ensuring the communication bus always has correct termination matching and improving the reliability and availability of system communication.

[0014] Preferably, the probe data includes the local device address, function code, register start address, register read length, and CRC16 checksum; the response includes the local device address, function code, data byte length, collected data, and CRC16 checksum. The probe and response frames adopt a standard frame format containing device address, function code, data field, and CRC16 checksum, making the data exchange content between upstream and downstream units clear and verifiable, ensuring correct judgment of communication status, and providing reliable data basis for establishing address lists and managing online devices, further enhancing the accuracy of automatic terminal resistor matching and system maintainability.

[0015] Thirdly, the present invention provides an automatic matching system for the terminal resistor of a parallel communication bus of an energy storage BMS, including a PCS or an inverter and multiple sets of parallel battery packs. Each set of battery packs is equipped with the aforementioned automatic matching circuit for the terminal resistor of the parallel communication bus of the energy storage BMS. Multiple battery management units are cascaded and networked through an 8-core twisted-pair network cable. After the bus interfaces of all battery management units are connected in parallel, they are uniformly connected to the PCS or inverter for communication.

[0016] In this solution, the aforementioned automatic matching circuit is integrated into the battery management unit of each battery pack, forming a complete lithium battery energy storage system. This allows the entire energy storage system to have automatic terminal resistor adaptation capability at the factory. On-site, simply cascading the battery packs with standard network cables is sufficient; the system can automatically complete communication bus matching without any manual settings or external resistors. This reduces the complexity of system installation and maintenance, improves the reliability of parallel communication in the energy storage system, and enhances the user experience.

[0017] Compared with the prior art, the beneficial effects of this invention are as follows: This invention provides an automatic matching circuit, method, and system for the terminating resistor of a parallel communication bus in an energy storage BMS. The automatic matching circuit includes multiple battery management units cascaded sequentially via a serial communication link. Each battery management unit is connected in parallel on the same communication bus via a bus interface. Each battery management unit includes a controller, an uplink serial interface, a downlink serial interface, a controlled switch, and a terminating resistor. The controlled switch and the terminating resistor are connected in series and then bridged between two differential signal lines of the communication bus. The controller is connected to the control terminal of the controlled switch and is used to control the on / off state of the controlled switch. During power-on initialization, the controlled switch is in the off state by default. The uplink serial interface is used to receive data from upstream battery management units and return a response to the upstream battery management unit when valid data is received. A: The downlink serial interface is used to send probe data to the downstream battery management unit and receive the response from the downstream battery management unit. The controller is configured to: if the uplink serial interface does not receive valid data within a first preset time period, determine that the battery management unit is the beginning of the communication bus, and control the controlled switch to close to connect the terminating resistor to the communication bus; if the downlink serial interface does not receive a valid response after sending probe data within a second preset time period, determine that the battery management unit is the end of the communication bus, and control the controlled switch to close to connect the terminating resistor to the communication bus; otherwise, determine that the battery management unit is an intermediate node and keep the controlled switch open. This invention integrates a terminating resistor and a controlled switch into each battery management unit. By utilizing the listening of the uplink serial interface and the active detection of the downlink serial interface, the controller can independently determine the physical location of the unit in the communication bus—the beginning, end, or intermediate node—and automatically control the connection and disconnection of the terminating resistor. This completely eliminates the need for manual insertion and removal of terminating resistors at the beginning and end nodes, a problem encountered in traditional methods. It also solves issues such as BMS manufacturers' inability to predict the number of parallel units, leading to over- or under-matching of terminating resistors; users needing to re-insert resistors when adding or removing battery packs, which can easily result in errors; and signal reflection and communication failures caused by manual mismatching. This invention enables plug-and-play terminating resistors, standardized mass production, and improved communication reliability. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. Some specific embodiments of the invention will be described in detail below with reference to the accompanying drawings in an exemplary and non-limiting manner. The same reference numerals in the drawings designate the same or similar parts or components. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a diagram of a traditional energy storage BMS parallel system architecture; Figure 2 This is an architecture diagram of the automatic matching system for the terminal resistor of the parallel communication bus of the energy storage BMS according to the present invention; Figure 3 This is a diagram of the internal communication structure of a traditional energy storage BMS unit. Figure 4 This is a structural diagram of the internal communication of a single BMS machine in the system of this invention; Figure 5 This is a flowchart of an automatic matching method for the terminal resistor of a parallel communication bus in an energy storage BMS according to the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] Example 1 Reference Figure 2 , Figure 4 , Figure 5 This embodiment provides an automatic matching system for the terminal resistor of a parallel communication bus in an energy storage BMS. This system includes a PCS or inverter and multiple parallel battery packs. Each battery pack is equipped with an automatic matching circuit for the terminal resistor of the parallel communication bus in an energy storage BMS. In lithium battery energy storage systems, multiple battery packs are used in parallel to achieve high power output. Each battery pack is equipped with a Battery Management Unit (BMS). Multiple BMSs are cascaded sequentially via a serial communication link and connected in parallel on the same communication bus, such as a CAN bus or RS485 bus. One end of the bus (i.e., the first BMS) is connected to external devices such as a PCS (energy storage converter) or inverter, thus forming a complete energy storage system. The BMSs are physically cascaded using an 8-core twisted-pair network cable, with some cores used to transmit uplink serial signals, downlink serial signals, and differential signals of the communication bus, making field wiring simple and plug-and-play.

[0021] An automatic matching circuit for the terminal resistor of a parallel communication bus in an energy storage BMS includes multiple battery management units cascaded sequentially via serial communication links, each of which is connected in parallel on the same communication bus via a bus interface; characterized in that each battery management unit includes a controller, an uplink serial interface, a downlink serial interface, a controlled switch, and a terminal resistor; The controlled switch is connected in series with the terminating resistor and then spans between the two differential signal lines of the communication bus; the controller is connected to the control terminal of the controlled switch and is used to control the on / off state of the controlled switch; during power-on initialization, the controlled switch is in the off state by default; the uplink serial interface is used to receive data from the upstream battery management unit and return a response to the upstream battery management unit when valid data is received; the downlink serial interface is used to send probe data to the downstream battery management unit and receive the response from the downstream battery management unit; The controller is configured to: if the uplink serial interface does not receive valid data within a first preset time period, determine that the battery management unit is the beginning of the communication bus, and control the controlled switch to close to connect the terminating resistor to the communication bus; if the downlink serial interface does not receive a valid response after sending probe data within a second preset time period, determine that the battery management unit is the end of the communication bus, and control the controlled switch to close to connect the terminating resistor to the communication bus; otherwise, determine that the battery management unit is an intermediate node and keep the controlled switch open.

[0022] Example 2 Reference Figure 2 , Figure 4 , Figure 5 This embodiment provides the internal communication structure of the BMS unit in the system of the present invention. Each battery management unit uniformly integrates a controller (such as an MCU), an uplink serial interface, a downlink serial interface, a bus interface (CAN / RS485 differential communication channel), a controlled switch, and a terminating resistor. The uplink and downlink serial interfaces both use isolated serial ports, such as a UART full-duplex interface, configured with a baud rate of 9600bps, 8 data bits, 1 stop bit, and CRC16 checksum to ensure communication reliability. The battery management unit also internally includes isolated power supply and data isolation modules to provide electrical isolation for the uplink serial interface, downlink serial interface, and bus interface, enhancing the system's anti-interference capability and security.

[0023] The controlled switch is connected in series with the terminating resistor and then spans between the two differential signal lines of the communication bus. The controller is connected to the control terminal of the controlled switch and is used to control the on / off state of the controlled switch. The terminating resistor can be 120Ω. Specifically, the control terminal of the controlled switch is connected to the IO pin of the controller, and the contact circuit of the controlled switch is connected in series with the terminating resistor and then in parallel between the CAN / RS485 differential signal lines CAN_H and CAN_L (or the A and B lines of RS485). In this embodiment, the controlled switch is preferably a magnetic latching relay, which has a power-off latching characteristic: when the battery management unit is offline or powered off due to a fault, the magnetic latching relay can maintain the contact state before the power-off, thereby locking the connection relationship between the terminating resistor and the bus and avoiding bus impedance mismatch caused by the disconnection of individual nodes. During system power-on initialization, the controllers of all battery management units control the controlled switches of their respective units to disconnect, so that the terminating resistors built into each unit are disconnected from the communication bus by default, preparing for subsequent automatic identification of the first and last nodes.

[0024] Each battery management unit receives data from its upstream neighboring unit via the uplink serial interface and returns an acknowledgment frame to the upstream unit upon receiving valid data. It also actively sends probe frames to its downstream neighboring unit via the downlink serial interface, waiting to receive acknowledgment frames from the downstream unit. Based on this "passive uplink acknowledgment, active downlink probe" interaction strategy, the controller can independently determine its physical location within the cascaded topology.

[0025] The specific location determination logic is as follows: The controller monitors the uplink serial interface in real time. If no valid data frame is received from upstream within a first preset time period (e.g., 1 second), the controller determines that the battery management unit is the head end of the communication bus, immediately controls the controlled switch to close, and connects the terminating resistor of the unit in parallel between the differential signal lines of the communication bus. If the uplink serial interface receives valid data sent from upstream within this time period, the controller replies with an acknowledgment frame to upstream and determines that the unit is not the head end node.

[0026] Simultaneously, the controller controls the downlink serial interface to cyclically send probe frames at a preset frequency (e.g., 3 times) within a second preset time period (e.g., 1 second). The probe frame format is constructed according to the preset protocol specification, as shown in the downlink sending example: device address (e.g., 01), function code (e.g., 03), register start address (0000), number of registers read (0002), and CRC16 checksum (C40B). If no valid response frame is received from the downstream after sending probe frames within this time period, the battery management unit is determined to be the tail end of the communication bus, and the controlled switch is closed to connect the terminating resistor to the communication bus. If the downlink serial interface receives a response frame from the downstream unit (e.g., uplink receiving example: device address 01, function code 03, number of bytes 04, data 0000C490, and CRC16 checksum 5890), the unit is determined to be a non-tail end node.

[0027] If the controller determines that the device is neither the beginning nor the end of the cascaded link, then the device is identified as an intermediate node in the cascaded link, the controlled switch is kept open, and the terminating resistor remains disconnected from the bus.

[0028] The aforementioned location determination mechanism enables the physical start and end points of the communication bus to automatically identify and connect terminating resistors without manual intervention. It is important to note that this determination logic does not rely on a central master node; each battery management unit can independently determine its location based solely on the communication status of its uplink and downlink ports, thus achieving distributed automatic matching without a master node dependency.

[0029] To support scenarios with dynamically changing parallel battery capacity, the controller is also equipped with a dynamic rematching mechanism. After the system completes initialization upon first power-on, each controller establishes and maintains a real-time online address list of all battery management units within the network based on uplink and downlink serial interaction data. It periodically exchanges heartbeats or status information via a communication bus (such as CAN / RS485) to monitor the online status of each node. When a user adds or removes battery packs, or when an intermediate node goes offline due to a fault, the network topology changes. The controller detects the change in the online list and immediately re-executes the aforementioned position determination process—each unit again determines whether it has become the new head or tail end through uplink listening and downlink probing, and accordingly closes or opens the controlled switch, thereby automatically completing the rematching of the terminating resistor. For scenarios using magnetic latching relays, even if a node is in a state with a terminating resistor connected while offline, this state will be latched, not affecting the normal impedance matching of the bus during offline periods, further ensuring communication reliability.

[0030] Example 3 Reference Figure 2 , Figure 4 , Figure 5Based on the system of the present invention in the above embodiments, this embodiment provides an automatic matching method for the terminal resistor of the parallel communication bus of an energy storage BMS. The method includes: initializing each battery management unit after system power-on, disconnecting all controlled switches, and deactivating the terminal resistor by default; cyclically sending uplink data monitoring and downlink probe frames in parallel; determining whether the device is the head end based on whether data is received at the uplink port, and if so, closing the switch to connect the terminal resistor; determining whether the device is the tail end based on whether a response is received at the downlink port, and if so, closing the switch to connect the terminal resistor; if neither is true, keeping the switch open; dynamically reconstructing the address list and re-executing the aforementioned steps when the number of parallel units changes or a node goes offline, thereby achieving dynamic matching of the terminal resistor.

[0031] This invention integrates the terminating resistor into each BMS, automatically identifies the bus topology location using the communication status of the uplink and downlink serial ports, and combines this with the status latching and dynamic list maintenance of the magnetic latching relay. This eliminates the need for external independent terminating resistors and manual plugging / unplugging operations, achieving the technical effects of adaptive matching, plug-and-play, and standardized batch delivery, thereby improving the reliability and ease of use of parallel communication in energy storage systems.

[0032] It should be noted that the above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention, and the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An automatic matching circuit for the terminating resistor of a parallel communication bus in an energy storage BMS, comprising multiple battery management units cascaded sequentially via a serial communication link, wherein each battery management unit is connected in parallel on the same communication bus via a bus interface; characterized in that, Each of the battery management units includes a controller, an uplink serial interface, a downlink serial interface, a controlled switch, and a terminating resistor; The controlled switch is connected in series with the terminating resistor and then spans between the two differential signal lines of the communication bus; the controller is connected to the control terminal of the controlled switch and is used to control the on / off state of the controlled switch; during power-on initialization, the controlled switch is in the off state by default; The uplink serial interface is used to receive data from the upstream battery management unit and to return a response to the upstream battery management unit when valid data is received; The downlink serial interface is used to send probe data to the downstream battery management unit and receive the response from the downstream battery management unit. The controller is configured to: if the uplink serial interface does not receive valid data within a first preset time period, determine that this battery management unit is the beginning of the communication bus, and control the controlled switch to close so as to connect the terminal resistor to the communication bus; If the downlink serial interface does not receive a valid response after sending probe data within a second preset time period, the battery management unit is determined to be the tail end of the communication bus, and the controlled switch is closed to connect the terminating resistor to the communication bus; otherwise, the battery management unit is determined to be an intermediate node, and the controlled switch is kept open.

2. The automatic matching circuit for the terminal resistor of the parallel communication bus of the energy storage BMS according to claim 1, characterized in that, The controlled switch is a magnetic latching relay; the magnetic latching relay has a power-off latching characteristic. When the battery management unit is offline and powered off, the magnetic latching relay maintains the on / off state before the power-off to lock the connection state between the terminal resistor and the communication bus.

3. The automatic matching circuit for the terminal resistor of the parallel communication bus of the energy storage BMS according to claim 1, characterized in that, The communication bus is either a CAN bus or an RS485 bus.

4. The automatic matching circuit for the terminal resistor of the parallel communication bus of the energy storage BMS according to claim 1, characterized in that, Both the uplink serial interface and the downlink serial interface are UART full-duplex interfaces, with the following communication parameters configured: baud rate 9600bps, 8 data bits, 1 stop bit, and CRC16 checksum.

5. The automatic matching circuit for the terminal resistor of the parallel communication bus of the energy storage BMS according to claim 1, characterized in that, The first preset duration is 1 second; the second preset duration is 1 second, and the downlink serial interface sends probe data 3 times within the 1 second.

6. The automatic matching circuit for the terminal resistor of the parallel communication bus of the energy storage BMS according to claim 1, characterized in that, The controller is also configured to: establish and maintain a real-time online address list of all battery management units in the network based on serial interaction data, and monitor the online status of each node; when the number of cascaded battery management units increases or decreases or a node goes offline, re-execute the determination of the first end and the last end and control the controlled switch according to the determination result to automatically update the on / off state of the terminal resistor.

7. The automatic matching circuit for the terminal resistor of the parallel communication bus of the energy storage BMS according to claim 1, characterized in that, The cascading of multiple battery management units is achieved through an 8-core twisted-pair network cable. The 8-core twisted-pair network cable simultaneously transmits uplink serial signals, downlink serial signals, and communication bus signals, effectively utilizing 5 cores and eliminating the need for external independent terminating resistors and their wiring. Each battery management unit is also equipped with an isolated power supply and data isolation module for electrical isolation of the uplink serial interface, the downlink serial interface, and the bus interface.

8. A method for automatic matching of terminal resistors of parallel communication bus in an energy storage BMS, characterized in that, The method is applied to the automatic matching circuit according to any one of claims 1 to 7, comprising: Step 1: After the system is powered on, each battery management unit initializes. The controller of each battery management unit controls the controlled switch of its unit to disconnect, so that the built-in terminating resistor of the unit is disconnected from the communication bus by default. Step 2: Each battery management unit enables data listening on its uplink serial interface in parallel and sends probe data cyclically through its downlink serial interface. Step 3, Head End Determination: If the upstream serial interface of this unit does not receive valid data within a preset time period, this unit is determined to be the head end of the communication bus. The controller controls the controlled switch of this unit to close and connects the terminating resistor to the communication bus. If valid data is received, a response is sent to the upstream unit, and this unit is determined to be a non-head end. Step 4, Tail End Determination: If the downlink serial interface of this unit fails to receive a valid response after sending probe data multiple times within a preset time period, this unit is determined to be the tail end of the communication bus. The controller controls the controlled switch of this unit to close and connect the terminating resistor to the communication bus. If a valid response is received, this unit is determined to be a non-tail end. Step 5, Intermediate Node Determination: If this unit is neither determined as the beginning end in step 3 nor as the end end in step 4, then the controlled switch of this unit remains open, and the terminating resistor remains disconnected from the communication bus. Step 6, Dynamic Rematching: The controller of each battery management unit maintains the online list of network device addresses in real time. When the number of parallel battery management units increases or decreases, or when a node goes offline, steps 2 to 5 are re-executed to automatically complete the re-determination of the node position and the corresponding switching of the on / off state of the terminal resistor of this unit.

9. The automatic matching method for the terminal resistor of the parallel communication bus of an energy storage BMS according to claim 8, characterized in that, The probe data includes the local device address, function code, register start address, register read length, and CRC16 checksum; the response includes the local device address, function code, data byte length, collected data, and CRC16 checksum.

10. An automatic matching system for the terminal resistor of a parallel communication bus in an energy storage BMS, comprising a PCS or an inverter and multiple sets of parallel battery packs, characterized in that, Each battery pack is equipped with an automatic matching circuit for the terminal resistor of the parallel communication bus of the energy storage BMS as described in any one of claims 1 to 7; multiple battery management units are cascaded and networked through an 8-core twisted-pair network cable, and the bus interfaces of all battery management units are connected in parallel to each other and then uniformly communicate with the PCS or inverter.

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