Parallel battery cooperative control method and system based on communication bus

Abstract

The application belongs to the technical field of battery management, and discloses a parallel battery cooperative control method and system based on a communication bus. The method adopts a decentralized architecture, each battery module periodically broadcasts its own information containing MOS state semantics through the communication bus, and receives other information; each module autonomously decides the switch of the charging and discharging MOS based on a preset rule. The core innovation includes: the MOS closed state is semantically classified into protection closed, logic closed and other types, precise cooperation is realized; a channel giving mechanism is introduced, so that the recovery process after protection is removed has no circulating current; in the discharging state, the braking signal and voltage judgment are combined to intelligently control the feedback current absorption; each module assigns an ID by broadcasting a unique code, supporting hot plug. The application completely eliminates the single-point fault of the traditional scheme, significantly improves the reliability, expandability, safety and energy efficiency of the parallel system, and is suitable for electric vehicles, energy storage devices and other fields.

Description

A method and system for coordinated control of parallel batteries based on a communication bus Technical Field

[0001] This invention relates to the field of battery management system technology, specifically to a control method and system applicable to parallel systems of multiple lithium batteries or other chemical systems, and particularly to a decentralized collaborative control scheme. Background Technology

[0002] With the rapid development of electric vehicles, residential energy storage, and mobile energy devices, users have placed higher demands on the capacity scalability, operational reliability, and ease of maintenance of power supply systems. To meet the needs of high power or long range, multiple battery packs or modules are often used in parallel. However, multi-battery parallel systems face many technical challenges in practical applications.

[0003] Currently, mainstream parallel connection schemes typically rely on a centralized main control unit, such as a separate parallel module or one selected from each battery as the parallel master unit, which handles the parallel logic and controls the other batteries. This approach has some inherent drawbacks:

[0004] 1. High risk of single point of failure: Once the main unit fails, the entire parallel system will be unable to coordinate, and may even cause safety hazards such as circulating current, overcharging, and reverse connection;

[0005] 2. Poor expandability: Adding or replacing battery modules requires reconfiguration of the host, making it difficult to achieve true "plug and play" functionality;

[0006] 3. High communication delay and load pressure: The master needs to frequently poll each slave, resulting in high bus load and control lag under high-speed dynamic conditions.

[0007] To improve system robustness, the industry has begun exploring decentralized, masterless parallel control architectures. Some solutions attempt to achieve parallel operation through hardware current sharing, such as diode isolation, resistor current limiting, or simple voltage comparison, but these suffer from low efficiency, severe heat generation, and an inability to dynamically adapt to operating conditions. Other solutions introduce CAN bus communication, enabling battery modules to exchange status information, but still rely on pre-defined master-slave roles or a central arbitration mechanism, failing to truly achieve autonomous collaborative decision-making among peer nodes.

[0008] Furthermore, circulating current suppression is a core safety issue during parallel operation. When there are voltage differences among the batteries, if the charging and discharging MOSFETs are turned on simultaneously, an internal circulating current will form. This not only wastes energy but may also trigger overcurrent protection or accelerate battery aging. Existing technologies mostly use a fixed differential voltage threshold to determine whether parallel operation is allowed, lacking semantic understanding of the reasons for MOSFET shutdown, such as whether it is due to protection triggering or active shutdown due to parallel logic. This prevents other nodes from accurately understanding the behavioral intent, thus affecting coordination accuracy. More seriously, even after the protection event is cleared, if all batteries synchronously resume conduction, a secondary circulating current may still be triggered due to the instantaneous voltage difference.

[0009] Therefore, there is an urgent need for an intelligent parallel control method that does not require host intervention and is based on local rules and state semantic broadcasting. This method can enable multiple battery modules to autonomously access, dynamically coordinate, and smoothly recover while ensuring safety. It can also be compatible with system-level constraints such as the status of electrical equipment, such as motor operation and communication heartbeat, thereby improving overall energy efficiency and reliability. Summary of the Invention

[0010] This invention aims to overcome the shortcomings of existing technologies and provide a highly reliable, hot-swappable, and energy-feedback-supporting parallel battery collaborative control method and system. Its core lies in eliminating dependence on a central controller, achieving safe and efficient system operation through the autonomous decision-making and collaboration of each battery module.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] Firstly, a parallel battery cooperative control method based on a communication bus is provided. This method is applied to a system consisting of at least two battery modules connected in parallel, with the modules interconnected via a communication bus. Each battery module includes an independent control unit and a charging / discharging MOSFET controlled by that control unit; the method is executed in parallel by the control units of each battery module, including:

[0013] Status broadcasting steps: The control unit of each battery module periodically broadcasts its own status information through the communication bus and listens for and receives status information broadcast by other battery modules; the self-status information includes at least: battery voltage, battery current, status of charging and discharging MOSFETs and status semantics;

[0014] The state semantics of the charging and discharging MOSFET include at least the following four types: on state, first passive off state due to analog front-end protection, first active off state due to parallel control logic, and second active off state due to main and auxiliary battery logic.

[0015] Autonomous decision-making process: Based on the status information of all battery modules received and the preset collaborative control rules, the control unit of each battery module autonomously decides and controls the switching action of its own charging and discharging MOSFETs to achieve decentralized collaboration among battery modules.

[0016] Furthermore, the autonomous decision-making step specifically includes:

[0017] When the system is in a discharging state, the control unit executes the discharge coordination logic, the goal of which is to turn on the discharge MOSFETs of all battery modules.

[0018] If the current battery module detects that it has a discharge current, it will turn on its own charging MOSFET;

[0019] If the system detects a braking energy feedback signal, it will only allow the battery module with the highest current voltage to turn on its charging MOSFET to absorb the feedback current.

[0020] Furthermore, the autonomous decision-making step also includes:

[0021] When the system is charging, the control unit executes charging coordination logic, the goal of which is to turn on the charging MOSFETs of all battery modules.

[0022] If the current battery module detects that it has a charging current, it will turn on its own discharge MOSFET;

[0023] During charging, only the battery module with the lowest current voltage is allowed to keep its discharge MOSFET on to ensure system output capability.

[0024] Furthermore, the method also includes a channel yielding mechanism:

[0025] When any battery module shuts down its MOSFET due to protection triggering, and the control unit of the battery module does not immediately turn the MOSFET back on after the protection condition is lifted;

[0026] The control unit continuously monitors the bus information until it determines, based on the status information broadcast by other battery modules, that other battery modules have actively turned off their corresponding MOSFETs due to parallel control logic, thereby freeing up the channel, and then it turns its own MOSFET back on.

[0027] Furthermore, in the status broadcasting step, the self-status information also includes the battery's unique code;

[0028] The method further includes an ID self-assignment step: the control unit of each battery module broadcasts its own unique code and receives the unique codes of other battery modules, sorts all codes, and autonomously determines its logical ID in the system based on the position of its own code in the sort.

[0029] Furthermore, the discharge coordination logic also includes anti-mutual charging rules:

[0030] If there is another battery module with a higher voltage than this battery module and its discharge MOSFET is in the on state, then the charging MOSFET of this battery module will be turned off.

[0031] If there are other battery modules with a higher voltage than this battery module and whose discharge MOSFETs are in the first active shutdown state due to parallel control logic, then the charging MOSFETs of this battery module will be turned off.

[0032] Secondly, a parallel battery cooperative control system based on a communication bus is provided to implement the above method. The system includes:

[0033] At least two battery modules, with the power ports of each battery module connected in parallel;

[0034] The communication bus connects the control units of all battery modules;

[0035] Each battery module includes:

[0036] Battery cell;

[0037] A charge / discharge MOSFET is connected in the charge / discharge circuit of the battery cell;

[0038] The control unit is connected to the battery cell, the charging / discharging MOSFET, and the communication bus; the control unit is configured to:

[0039] The system periodically broadcasts its own status information through the communication bus and listens for and receives status information from other battery modules.

[0040] Based on all received status information and preset collaborative control rules, it autonomously makes decisions and controls the switching action of its own charging and discharging MOSFETs.

[0041] Among them, the broadcast's own status information semantically distinguishes the off state of the charging and discharging MOSFET, at least distinguishing between off due to hardware protection and active off due to cooperative logic.

[0042] Furthermore, the control unit is also configured to execute a channel yielding mechanism: when the MOSFET is turned off due to protection triggering, even if the protection is released, it must wait for the status information of other battery modules actively turning off their corresponding MOSFETs due to collaborative logic before it can turn its own MOSFET back on.

[0043] Furthermore, the communication bus is a CAN bus; the battery module is a co-port BMS battery module, which does not require an external parallel controller.

[0044] Compared with the prior art, the present invention has the following significant advantages:

[0045] 1. This invention features high reliability and decentralization, completely eliminating single points of failure, and ensuring that the failure of any module does not affect the overall collaborative operation of the system.

[0046] 2. This invention enables true hot-swapping and high scalability. Based on ID self-assignment and status broadcasting, new modules can be connected autonomously without host configuration.

[0047] 3. This invention has high security and can effectively suppress circulating current. Through semantic MOS state, channel yielding mechanism and refined anti-inter-charging rules, it fundamentally avoids circulating current from the level of intent recognition and behavior coordination.

[0048] 4. This invention can intelligently support energy feedback, combining braking signals and voltage judgment to precisely control the object of feedback current absorption, thereby improving energy efficiency.

[0049] 5. This invention can be implemented using the existing same-port BMS architecture, without the need for additional parallel controllers or complex hardware, and is low in cost and easy to implement.

[0050] 6. The parallel logic of this invention also supports independent operation of a single battery. Attached Figure Description

[0051] Figure 1 is a schematic diagram of the parallel battery system architecture according to an embodiment of the present invention.

[0052] Figure 2 is a flowchart of the discharge MOS control logic in the discharge process of an embodiment of the present invention.

[0053] Figure 3 is a flowchart of the charging MOS control logic during the discharge process in an embodiment of the present invention.

[0054] Figure 4 is a flowchart of the charging MOS control logic in the charging process of an embodiment of the present invention. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are for illustrative purposes only and do not constitute a limitation on the scope of protection of this invention.

[0056] Example 1: System Architecture

[0057] Referring to the system architecture diagram shown in Figure 1, the system of this invention mainly includes multiple battery cells with identical structures and a shared communication bus. Each battery cell includes at least: a battery body for storing electrical energy; a group of switching devices, typically including charging switching devices (such as charging MOS) and discharging switching devices (such as discharging MOS), used to control the charging and discharging path between the battery body and the external bus (P+, P-); a local controller, such as a microcontroller unit (MCU); and a communication interface, such as a controller area network (CAN) transceiver. The communication interfaces of all battery cells are connected to the same shared communication bus, forming a peer-to-peer network without a central master node. The local controller is responsible for collecting the status of its own battery cell (such as voltage and current), controlling the group of switching devices, and broadcasting its own status information on the bus through the communication interface, while listening to and receiving status information broadcast by other battery cells. Based on this information and embedded coordination rules, each local controller independently decides and controls the switching state of its own cell, achieving global coordination.

[0058] Example 2: Control Method Flow

[0059] The core of this invention lies in the control logic that is executed in parallel by each control unit.

[0060] This invention defines a set of executable rules for parallel-connected batteries. All batteries are connected via a communication bus (the bus is CAN by default, but not limited to CAN). Each battery broadcasts its own information and receives information from other batteries, executing corresponding actions according to the defined rules. As long as information flow is smooth, and each battery follows a set of rules, knowing when to turn on and off the MOSFET, the system can operate safely.

[0061] When the battery is powered on, it is divided into discharge and charging states according to the rules. When the battery detects a special signal from the charger (such as a CAN message or a charger in-position analog level signal), the system enters the charging state. All states other than the charging state are classified as the discharge state.

[0062] During discharge, the ultimate goal of the parallel connection rule is to turn on the discharge MOS of all batteries, while the charging MOS is off by default. When a battery has a discharge current, the corresponding charging MOS of that battery turns on. When the electrical equipment brakes, there may be a feedback current (reverse charging). In order for the parallel battery system to accept reverse charging during the discharge process, the parallel system will turn on the highest voltage charging MOS based on the signal that reverse charging is possible (such as special signals such as motor speed).

[0063] During charging, the ultimate goal of the parallel connection rule is to ensure that the charging MOSFETs of all batteries are turned on, while the discharging MOSFETs are off by default. When a battery receives charging current, the corresponding discharging MOSFET turns on. To ensure that the battery with the lowest voltage output current is maintained during charging, the discharging MOSFET is turned on.

[0064] The switching on and off of the MOSFET is not preemptive; it is coordinated according to the battery state. Sometimes, in order for other batteries to turn on the MOSFET, the MOSFET will be turned off on its own.

[0065] To determine the battery ID, the battery broadcasts its own unique battery code and receives codes from other batteries. The codes are sorted, and the ID is determined based on the battery's position in the sorting list.

[0066] The MOS switch of the battery broadcast has the following 4 states, and the battery determines its own action based on the MOS state of other batteries.

[0067] 0: MOS on;

[0068] 1: Due to AFE protection being shut down (passive);

[0069] 2: Due to MCU logic shutdown (active);

[0070] 3: Due to the main and auxiliary battery logic being shut down.

[0071] The rules for the states of discharge and charge are described in detail below:

[0072] Discharge state:

[0073] The battery broadcasts its own voltage, current, MOS actual status, and the reasons for MOS shutdown: active logic and passive logic. Charging and discharging are marked separately. The shutdown due to protection belongs to passive logic, while the shutdown due to parallel logic belongs to active logic.

[0074] As shown in Figure 2, the discharge MOS control logic during the discharge process is as follows:

[0075] In addition to this battery, if there is a battery with a low voltage and the charging MOSFET is on, the discharging MOSFET will be off (otherwise it will charge the low-voltage battery); otherwise, the discharging MOSFET is allowed to be on. A low voltage battery is one whose voltage is lower than the voltage of this battery minus the allowable voltage difference.

[0076] As shown in Figure 3, the charging MOS control logic during the discharge process is as follows:

[0077] 1. If there is a battery other than this battery with a high voltage and the discharge MOS is turned on, the charging MOS will be turned off. Otherwise, the charging MOS is allowed to be turned on. High voltage means that it is greater than the voltage of this battery plus the allowable voltage difference (otherwise, they will charge each other).

[0078] 2. In addition to this battery, if there is a battery with a high voltage and the discharge MOS is actively turned off due to parallel logic, the charging MOS will be turned off. Otherwise, the charging MOS is allowed to be turned on. High voltage means that it is greater than the voltage of this battery plus the allowable voltage difference (turning on the charging MOS with a low voltage will affect the turning on of the discharge MOS with a high voltage, so the channel must be given up).

[0079] 3. In addition to this battery, if there are batteries with high voltage and the charging MOS is turned off due to protection but not for discharge protection, the charging MOS will be turned off. Otherwise, the charging MOS is allowed to be turned on. High voltage means that it is greater than the voltage of this battery plus the allowable voltage difference (otherwise they will charge each other).

[0080] 4. Turn off the charging MOS within 5 seconds of powering on (sufficient time for power-on detection).

[0081] 5. If the system and the electrical equipment do not communicate, the charging MOS will be turned off for 1.5 seconds (sufficient time for power-on detection).

[0082] 6. When the motor speed is less than or equal to 1, the charging MOS is turned off (to support the braking reverse charging design, when there is speed, there will be reverse charging when decelerating).

[0083] 7. Charging current greater than 0.8 Overcurrent charging value, shut down the charging MOS (to prevent overcurrent charging).

[0084] 8. When the internal voltage of the battery (plus the allowable voltage difference) is less than the P+P- voltage, the charging MOS will be turned off (the charging MOS must not be turned on when the external voltage of the battery is high, otherwise there will be no communication).

[0085] 9. In addition to the above conditions, turn on the charging MOS.

[0086] When the protection is released, logically the MOS will not turn on immediately after the self-protection is released, and will only turn on after other batteries give way.

[0087] Charging status:

[0088] The discharge MOS control logic during the charging process is as follows: if the voltage of the battery itself is higher than that of other batteries, the discharge MOS is turned off; otherwise, the discharge MOS is turned on. Here, the discharge MOS is turned on for the battery with the lowest voltage.

[0089] As shown in Figure 4, the charging MOS control logic during the charging process is as follows:

[0090] 1. The charging MOS is turned off when its own voltage (plus the allowable voltage difference) is less than the voltage of the battery that turns on the discharge MOS.

[0091] 2. The self-discharge MOS is turned on because of the charging current, but the charging MOS of the lower voltage battery is not turned on due to the parallel logic, thus turning off the self-charging MOS (affecting the turn-on of the low voltage charging MOS and making way for the channel).

[0092] 3. The charging MOS is turned off if the power-on time is less than 5 seconds, and turned on in other cases.

[0093] Furthermore, a crucial aspect of the system is determining when to turn the charging MOS on and off. The charging MOS should ideally remain off when there is no reverse charging. If the system can transmit at the required speed, the charging MOS should only be turned on once speed is available, as reverse charging current only occurs when there is speed.

[0094] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the inventive concept of the present invention and the description and drawings, or direct / indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A parallel battery cooperative control method based on a communication bus, characterized in that, It is applied to parallel battery systems including at least two battery modules, each battery module is interconnected through a communication bus, and each battery module includes an independent control unit and a charging and discharging MOSFET controlled by the control unit; The method is executed in parallel by the control units of each battery module, including: a status broadcasting step: each battery module's control unit periodically broadcasts its own status information through the communication bus and listens for and receives status information broadcast by other battery modules; the self-status information includes at least: battery voltage, battery current, and the status and status semantics of the charging and discharging MOSFETs; wherein, the status semantics of the charging and discharging MOSFETs include at least the following four: on state, first passive off state due to simulated front-end protection, first active off state due to parallel control logic, and second active off state due to main and auxiliary battery logic; an autonomous decision-making step: each battery module's control unit autonomously decides and controls the switching action of its own charging and discharging MOSFETs based on the received status information of all battery modules and preset collaborative control rules, so as to achieve decentralized collaboration among battery modules; the autonomous decision-making step specifically includes: when the system is in a discharging state, the control unit executes the discharge collaboration logic, the goal of which is to turn on the discharge MOSFETs of all battery modules; if the current battery module detects that it has a discharge current, it turns on its own charging MOSFET; if the system detects that there is a braking energy feedback signal, only the battery module with the highest current voltage is allowed to turn on its charging MOSFET to absorb the feedback current. The method further includes a channel yielding mechanism: when any battery module shuts down its charging MOSFET or discharging MOSFET due to protection triggering, and after the protection condition is released, the control unit of that battery module does not immediately restart the charging MOSFET or discharging MOSFET; the control unit continuously monitors the bus information until it determines, based on the status information broadcast by other battery modules, that other battery modules have actively shut down their charging MOSFET or discharging MOSFET due to parallel control logic, thus yielding the channel, and then restarts its own charging MOSFET or discharging MOSFET; in the status broadcasting step, the self-status information also includes the battery's unique code; the method further includes an ID self-assignment step: the control unit of each battery module broadcasts its own unique code and receives the unique codes of other battery modules, sorts all codes, and autonomously determines its logical ID in the system based on the position of its own code in the sort; the discharge coordination logic also includes anti-mutual charging rules: if there is another battery module with a voltage higher than this battery module and its discharging MOSFET is in the on state, then the charging MOSFET of this battery module is shut down; if there is another battery module with a voltage higher than this battery module and its discharging MOSFET is in the first actively shut-down state due to parallel control logic, then the charging MOSFET of this battery module is shut down.

2. The method according to claim 1, characterized in that, The autonomous decision-making steps also include: when the system is in a charging state, the control unit executes charging coordination logic, the goal of which is to turn on the charging MOSFETs of all battery modules; if the current battery module detects that it has a charging current, it turns on its own discharge MOSFET; in the charging state, only the battery module with the lowest current voltage is allowed to keep its discharge MOSFET turned on, so as to ensure the system output capability.

3. A parallel battery cooperative control system based on a communication bus, characterized in that, To implement the method as described in any one of claims 1 to 2, the parallel battery cooperative control system based on a communication bus includes: at least two battery modules, with the power ports of each battery module connected in parallel; a communication bus connecting control units of all battery modules; wherein each battery module includes: a battery cell; a charging / discharging MOSFET connected in the charging / discharging circuit of the battery cell; and a control unit connected to the battery cell, the charging / discharging MOSFET, and the communication bus; the control unit is configured to: periodically broadcast its own status information through the communication bus and listen to and receive status information from other battery modules; autonomously decide and control the switching action of its own charging / discharging MOSFET according to all received status information and preset cooperative control rules; wherein, in the broadcasted own status information, the off state of the charging / discharging MOSFET is semantically distinguished, at least distinguishing between off due to hardware protection and active off due to cooperative logic.

4. The parallel battery cooperative control system based on a communication bus according to claim 3, characterized in that, The control unit is also configured to execute a channel yield mechanism: when the charging MOSFET or discharging MOSFET is turned off due to protection triggering, even if the protection is released, it must wait for the status information of other battery modules actively turning off the charging MOSFET or discharging MOSFET due to cooperative logic before it can turn its own charging MOSFET or discharging MOSFET back on.

5. The parallel battery cooperative control system based on a communication bus according to claim 3, characterized in that, The communication bus is a CAN bus; the battery module is a same-port BMS battery module, which does not require an external parallel controller.

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