Low-voltage household energy storage control method, system and circuit

Abstract

The application provides a low-voltage household energy storage control method, a parallel system and a circuit, wherein a battery control unit (BCU) is defined as a master and a battery management unit (BMU) is defined as a slave; after the master is powered on and initialized, a one-time authentication instruction is sent to each slave, a one-time result authentication is performed on a one-time reply of each slave completing a one-time authentication feedback; after the one-time result authentication is successful, a two-time authentication instruction is sent to each slave, a two-time result authentication is performed on a two-time reply of each slave completing a two-time authentication feedback, and the slaves successfully authenticated are connected in parallel, thereby realizing a safe and efficient buck starting process, facilitating BMU error positioning due to fixed master and BMU serial numbers, reducing the circulating current generated by battery connection in parallel, preventing other manufacturers from modifying the system module, improving system safety, improving parallel connection efficiency, reducing the circulating current of the battery, prolonging the service life of the battery and reducing system loss.

Description

Technical Field

[0001] This invention relates to the field of battery parallel protection technology, and in particular to a low-voltage residential energy storage control method, parallel system and circuit. Background Technology

[0002] In most residential / home energy storage systems on the market, there is no fixed master control system. Instead, a virtual master unit is randomly generated from the battery cells through competition, serving as the communication interface for aggregating information and connecting to the inverter or upper-level control system. Furthermore, the inverter master / upper-level control system / battery master (including the virtual master) does not authenticate newly added battery cells / modules as products of its own company, nor does it verify the product series, hardware version number, or software version number of the battery cells. As long as communication is established, it can work. This creates the possibility that other manufacturers may use counterfeit or stolen battery cells / modules from the company.

[0003] Traditional battery paralleling often uses pre-charge resistors, which results in low paralleling efficiency, small pre-charge current, and the pre-charge resistors easily overheating, causing the entire battery cell to heat up. Alternatively, DC-DC buck-boost circuits are used, but these are costly and have complex control algorithms. Furthermore, the paralleling algorithm mainly considers the voltage difference between the battery module to be connected and the bus voltage, or judges the system current; the battery module passively waits for the paralleling conditions to be met before paralleling can begin. Traditional home energy storage systems require a "star connection" to achieve optimal battery balance, but this home energy storage system can achieve optimal balance even without a star connection. Each BMU (battery unit) number is randomly generated. When multiple batteries fail, it's impossible to determine which number corresponds to which battery, requiring indirect methods (mobile app / host computer / LCD display) for identification, which is inconvenient for maintenance. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a low-voltage residential energy storage control method, a parallel system, and a circuit. The low-voltage residential energy storage system uses a Battery Control Unit (BCU) as the master and a Battery Management Unit (BMU) as the slave. The use of a stacked energy storage system and a certification process improves system security. The use of a low-cost buck circuit and the parallel control method of this patent reduces battery circulating current and improves battery life.

[0005] Specifically:

[0006] This invention provides a low-voltage residential energy storage control method, the control method comprising:

[0007] S1: Define the Battery Control Unit (BCU) as the master and the Battery Management Unit (BMU) as the slave; each master is responsible for managing the data information of multiple slaves that communicate with it.

[0008] S2: After the host is powered on and performs initialization self-test, it sends an authentication command to each slave and performs result authentication on each slave's response after completing an authentication feedback.

[0009] S3: After the first authentication is successful, a second authentication command is sent to each slave device to perform a second authentication on the slave device's second response after completing the second authentication.

[0010] S4: Connect the successfully authenticated slave device to the main machine.

[0011] The slave device's data information includes at least: the total battery voltage of each battery management unit (BMU), the voltage, temperature, remaining charge, battery health status, battery power status, main charge / discharge transistor status, and the PWM duty cycle value or switching status of the BUCK current limiting circuit's charge / discharge transistor.

[0012] When the host is powered on and performs an initialization self-test in step S2, the following steps are also included:

[0013] By physically activating the slave device, the power supply to the slave device circuit is enabled, thus powering on the slave device.

[0014] After the slave device is powered on, the initialization output power is completed and the host device is started.

[0015] The slave device reads the level information of the SW array and calculates its own BMU serial number. The BMU serial numbers of any two slave devices are different.

[0016] In step S2, after the host sends an authentication command to each slave, the slave receives the authentication command and returns a response to the host. At the same time, the slave performs a self-test. Whenever the format of the command sent by any slave is the same as that of another slave, it sends a fault record to the host and powers down the slave after a preset time to maintain normal system operation.

[0017] The first authentication command is: BCU identification ID or BCU type + first authentication command;

[0018] The slave device's response in one go is: first authentication command + BMU serial number + random number + authentication data.

[0019] After the slave instruction format is sent to the host, a soft boot command message is sent to the host. The soft boot command message is a soft boot command plus the BMU sequence number.

[0020] The slave device with the first BMU sequence number is designated as the first to start the host's battery management unit (BMU). If the slave device with the first BMU sequence number malfunctions or fails to send a soft-start command message after a preset time, the next slave device in sequence is used to replace it.

[0021] The slave device outputs VSQ2 at 100% duty and VSQ1 at PWM duty cycles from smallest to largest through the Buck circuit, supplying power to Pp and Pn to the bus. When the bus voltage and current rise to a certain value, the master device powers on and starts up. Once the slave device receives an authentication command from the master device, the master device starts up normally.

[0022] Step S3, which involves performing secondary authentication on the secondary responses from each slave device after completing the secondary authentication, also includes:

[0023] If the secondary authentication result is successful, the host will include the slave device in its management scope; otherwise, the slave device will be stopped from working. The secondary authentication command is: BCU identification ID or BCU type + second authentication command + random number + authentication data. The slave device's secondary response is: second authentication command + BMU serial number + authentication result.

[0024] Step S4, which involves parallel operation, specifically includes:

[0025] Once the slave device is connected to the Pn or Pp power bus, it begins to upload its own real-time information.

[0026] Based on the real-time information uploaded by each slave device, the master device prioritizes selecting slave devices whose battery voltage and current Pn and Pp bus voltages are within the set parallel operation threshold, and sends the parallel operation command starting from the slave device with the smaller sequence number.

[0027] After receiving the parallel operation command, the slave device determines whether the voltage difference between the bus voltage and the battery voltage is within the set first parallel operation voltage threshold range. If it is, the master device sends the first parallel operation command, and the slave device performs the parallel operation. Otherwise, the master device selects a slave device between the first and second parallel operation voltage thresholds based on the real-time information, and sends the second parallel operation command according to the BMU serial number from smallest to largest. After receiving the parallel operation command, the slave device performs the BUCK charging and discharging current limiting operation until the voltage difference between the battery voltage and the bus voltage is less than the first parallel operation voltage threshold or the BUCK charging and discharging current is less than the set threshold. Only then does the slave device turn on the main charging tube and the main discharging tube, the BUCK circuit stops working, and the parallel operation is completed.

[0028] When the voltage difference between the bus voltage and the battery voltage is greater than the second parallel voltage threshold, the host sends a parallel command according to the system's charging and discharging status. In the charging state, the host aggregates the charging current demand of all slave devices, enabling the paralleled batteries to charge at maximum charging power, and the bus voltage gradually rises. When the voltage difference between the bus voltage and the battery voltage is lower than the second parallel threshold, the host sends a second parallel command, and the slave device executes a BUCK discharge current limiting operation until the paralleling is completed. In the discharging state, the host monitors the battery voltage of the slave device to be paralleled in real time. When the bus voltage drops to a point where the voltage difference with the voltage to be paralleled is less than the second parallel threshold, the second parallel command is issued, and the BMU executes a BUCK discharge current limiting operation until the paralleling is completed.

[0029] As another preferred embodiment, the present invention also provides a low-voltage residential energy storage parallel operation system, wherein the energy storage parallel operation system adopts the low-voltage residential energy storage control method described above.

[0030] As another preferred embodiment, the present invention also provides a circuit belonging to a type of low-voltage residential energy storage control circuit. The circuit includes at least a battery control unit (BCU) circuit and a battery management unit (BMU) circuit, which are used to implement the low-voltage residential energy storage control method process described above.

[0031] In summary, this invention provides a low-voltage residential energy storage control method, a parallel system, and a circuit. The method defines a Battery Control Unit (BCU) as the master and a Battery Management Unit (BMU) as the slave. After the master is powered on and performs an initial self-test, it sends an authentication command to each slave. The system then performs a first-response authentication on each slave's response to the first authentication. Once the first authentication is successful, a second authentication command is sent to each slave. The system then performs a second-response authentication on each slave's response to the second authentication. Finally, the successfully authenticated slaves are connected in parallel.

[0032] The beneficial effects of this invention are:

[0033] 1. An authentication process was used to prevent other vendors from copying system modules, thereby improving system security and economic efficiency.

[0034] 2. By using a low-cost buck circuit and the parallel control method of this patent, parallel efficiency is greatly improved, battery circulating current is reduced, battery life is increased, and system losses are reduced.

[0035] 3. Safe and efficient buck startup process, detecting external short circuits and parallel input / output current limiting.

[0036] 4. Fixed host and BMU serial numbers facilitate BMU error location.

[0037] 5. A stable, reliable, and efficient parallel control method reduces circulating current generated during battery parallel operation. Attached Figure Description

[0038] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0039] Figure 1 This is a flowchart illustrating the overall process of a low-voltage residential energy storage control method according to the present invention.

[0040] Figure 2 This is a flowchart illustrating the working principle of the BMU described in this invention.

[0041] Figure 3 This is a flowchart illustrating the working principle of the BCU described in this invention.

[0042] Figure 4 This is a circuit diagram for the serial number detection described in this invention.

[0043] Figure 5 This is a diagram showing the serial number detection results described in this invention.

[0044] Figure 6 This is the BUCK circuit diagram described in this invention.

[0045] Figure 7 This is a flowchart illustrating the parallel operation principle of the present invention.

[0046] Figure 8 This is a schematic diagram of the stacking of the low-voltage residential energy storage parallel system described in this invention. Detailed Implementation

[0047] To enable those skilled in the art to better understand the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only 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 are within the scope of protection of the present invention.

[0048] like Figure 1-3 As shown, the present invention provides a low-voltage residential energy storage control method, the control method comprising:

[0049] S1: Define the Battery Control Unit (BCU) as the master and the Battery Management Unit (BMU) as the slave; each master is responsible for managing the data information of multiple slaves that communicate with it.

[0050] S2: After the host is powered on and performs initialization self-test, it sends an authentication command to each slave and performs result authentication on each slave's response after completing an authentication feedback.

[0051] S3: After the first authentication is successful, a second authentication command is sent to each slave device to perform a second authentication on the slave device's second response after completing the second authentication.

[0052] S4: Connect the successfully authenticated slave device to the main machine.

[0053] The slave device's data information includes at least: the total battery voltage of each battery management unit (BMU), the voltage, temperature, remaining charge, battery health status, battery power status, main charge / discharge transistor status, and the PWM duty cycle value or switching status of the BUCK circuit's charge / discharge transistor.

[0054] When the host is powered on and performs an initialization self-test in step S2, the following steps are also included:

[0055] By physically activating the slave device, the power supply to the slave device circuit is enabled, thus powering on the slave device.

[0056] After the slave device is powered on, the initialization output power is completed and the host device is started.

[0057] like Figure 4 As shown, the slave device reads the level information of the SW array and calculates its own BMU serial number. The BMU serial numbers of any two slave devices are different.

[0058] like Figure 5 The diagram shows the SW array level information for one channel. Through N SW level detection circuits, 2^N arrangements can be achieved. For example, if three SW level detection circuits are connected to the P1.0, P1.1, and P1.2 pins of the MCU respectively, 2^3 arrangements, or 8 BMUs, can be generated based on the readings of P1.0, P1.1, and P1.2. Figure 4 When SW1 is stacked and blocked by structural components, SW1 is connected, the signal at "TO MCU" is high, and the MCU pin reading is "1". If it is not blocked, it is low ('0'). By arranging them, 8 BMU serial numbers can be arranged. According to the number of SW level detection circuits, 2 to the power of N BMU serial numbers can be obtained.

[0059] In step S2, after the host sends an authentication command to each slave, the slave receives the authentication command and returns a response to the host. At the same time, the slave performs a self-test. Whenever the format of the command sent by any slave is the same as that of another slave, it sends a fault record to the host and powers down the slave after a preset time to maintain normal system operation.

[0060] The first authentication command is: BCU identification ID or BCU type + first authentication command;

[0061] The slave device's response in one go is: first authentication command + BMU serial number + random number + authentication data.

[0062] After the slave instruction format is sent to the master, a soft-boot command message is sent to the master. The soft-boot command message consists of a soft-boot command plus a BMU sequence number. The random number is generated autonomously by the BMU; the authentication data is encrypted using the random number and a key stored within the BMU; and the master and slave share the same key.

[0063] The slave device with the first BMU sequence number is designated as the first to start the host's battery management unit (BMU). If the slave device with the first BMU sequence number malfunctions or fails to send a soft-start command message after a preset time, the next slave device in sequence is used to replace it.

[0064] For example, if a soft-start command message is not sent within 5 seconds, and BMU No.1 fails to upload a BMU soft-start command within 5 seconds of power-on, other slave devices will detect the soft-start command timeout and BMU No.2 will upload the soft-start command and execute the soft-start action. If BMU No.2 also fails, BMU No.3 will execute the soft-start. This process continues until the number of slave devices falls below the system's minimum working number, at which point the soft-start action will not be executed, the entire system will stop running, and the corresponding fault and cause will be recorded.

[0065] like Figure 6 As shown, the slave device outputs VSQ2 100% duty through the Buck circuit, and VSQ1 outputs PWM duty cycles from small to large, supplying power to Pp and Pn to the bus. When the bus voltage and current rise to a certain value, the master device powers on and starts up. Once the slave device receives an authentication command from the master device, the master device starts up normally.

[0066] Normally, BMU No. 1 is used to boot the host by default. The current bus voltage is 0V, so the host cannot boot.

[0067] For example, PWM duty starts at 5%, increasing by 1% every 10ms. The maximum duty cannot exceed 90% or the highest duty value determined by the buck circuit. During output duty, the BMU monitors the voltages of Pp and Pn, and the current in the Buck In and Ip circuits to prevent external short circuits and buck circuit overcurrent. In case of a fault, the buck output stops, the BMU indicates, records, and uploads the error command before shutting down.

[0068] During the process of BMU No.1 using the BUCK current-limiting output to the bus, when the bus voltage and current rise to a certain value, the BCU powers on and starts. After the BCU completes a series of initializations such as power-on self-test, the BCU sends a BMU authentication command via the CAN, RS485, or other buses. Upon receiving the BCU's authentication command, BMU No.1 indicates that the BCU has started normally. BCU No.1 turns on the charging and discharging transistors of the main circuit, and the VSQ1 and VSQ2 PWM duty outputs of the Buck circuit are 0%, so the Buck circuit does not work. If BMU No.1 cannot use the Buck to start the BCU for other reasons, then BMU No.2 will start it, and so on.

[0069] Step S3, which involves performing secondary authentication on the secondary responses from each slave device after completing the secondary authentication, also includes:

[0070] If the secondary authentication result is successful, the host will include the slave device in its management scope; otherwise, the slave device will be stopped from working. The secondary authentication command is: BCU identification ID or BCU type + second authentication command + random number + authentication data. The slave device's secondary response is: second authentication command + BMU serial number + authentication result.

[0071] like Figure 7 As shown, step S4, which involves parallel operation, specifically includes:

[0072] Once the slave device is connected to the Pn or Pp power bus, it begins to upload its own real-time information.

[0073] Based on the real-time information uploaded by each slave device, the master device prioritizes selecting slave devices whose battery voltage and current Pn and Pp bus voltages are within the set parallel operation threshold, and sends the parallel operation command starting from the slave device with the smaller sequence number.

[0074] The real-time information includes at least the BMU real-time information reporting command + BMU serial number + total battery voltage, battery current, maximum and minimum cell voltage, maximum and minimum cell temperature, SOC, SOH, SOP (charging demand current and discharge current), main charging and discharging tube status, BUCK current limiting circuit charging and discharging tube PWM duty cycle value or its switching status, but is not limited to these.

[0075] After receiving the parallel operation command, the slave device determines whether the voltage difference between the bus voltage and the battery voltage is within the set first parallel operation voltage threshold range.

[0076] If present, the master sends the first parallel operation command, and the slave performs the parallel operation.

[0077] Otherwise, based on the real-time information, the host selects a slave device that is between the first and second parallel voltage thresholds, and sends a second parallel command according to the BMU serial number from smallest to largest. After receiving the parallel command, the slave device performs BUCK charging and discharging current limiting action until the voltage difference between the battery voltage and the bus voltage is less than the first parallel voltage threshold or the BUCK charging and discharging current is less than the set threshold. Only then will the slave device turn on the main charging tube and the main discharging tube, the BUCK circuit stop working, and the parallel operation is completed.

[0078] For example: the parallel operation threshold is 3V. BMU No.1 is currently connected to the bus (currently, only BMU No.1 is on the power bus), and the bus voltage is the voltage of BMU No.1, assuming it is 51.2V. BMU No.2 is 55.3V, BMU No.3 is 50.5V, and BMU No.4 is 52.1V. Then, the BCU requests BMU No.3 to perform the parallel operation, and then requests BMU No.4 to perform the parallel operation.

[0079] When the voltage difference between the bus voltage and the battery voltage is greater than the second parallel voltage threshold, the host sends a parallel command according to the system's charging and discharging status. In the charging state, the host aggregates the charging current demand of all slave devices, enabling the paralleled batteries to charge at maximum charging power, and the bus voltage gradually rises. When the voltage difference between the bus voltage and the battery voltage is lower than the second parallel threshold, the host sends a second parallel command, and the slave device executes a BUCK discharge current limiting operation until the paralleling is completed. In the discharging state, the host monitors the battery voltage of the slave device to be paralleled in real time. When the bus voltage drops to a point where the voltage difference with the voltage to be paralleled is less than the second parallel threshold, the second parallel command is issued, and the BMU executes a BUCK discharge current limiting operation until the paralleling is completed.

[0080] When the BMU is under protection, it will automatically disconnect from the network. Once the protection is lifted, the BCU will control the BMU to perform a parallel operation.

[0081] In this invention, the master and slave devices may communicate via CAN, RS485 or other communication buses, but are not limited thereto.

[0082] As another preferred embodiment, the present invention also provides a low-voltage residential energy storage parallel operation system, wherein the energy storage parallel operation system employs the low-voltage residential energy storage control method described above. Figure 8 As shown, the module at the top is BCU, the next highest is BMU No.1, then BMU No.2, BMU No.3… BMU No.N, BMU No.N+1, with the BMUs at the bottom having larger serial numbers. Figure 2The detection circuit ensures that when the switch (SW) is blocked by structural components of the chassis, the BMU detects a high level. The 4-channel SW detection circuit can program 16 BMUs. The BMU module located at the second-to-top is BMU No.1, and the bottom one is BMU No.16.

[0083] As another preferred embodiment, the present invention also provides a circuit belonging to a type of low-voltage residential energy storage control circuit. The circuit includes at least a battery control unit (BCU) circuit and a battery management unit (BMU) circuit, which are used to implement the low-voltage residential energy storage control method process described above.

[0084] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0085] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0086] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A low-voltage residential energy storage control method, characterized in that, The control method includes: S1: Define the Battery Control Unit (BCU) as the master and the Battery Management Unit (BMU) as the slave; each master is responsible for managing the data information of multiple slaves that communicate with it; S2: After the host is powered on and performs initialization self-test, it sends an authentication command to each slave and performs result authentication on each slave's response after completing an authentication feedback. S3: After the first authentication result is successful, a second authentication command is sent to each slave device to perform a second authentication on the slave device's second response after completing the second authentication. S4: Connect the successfully authenticated slave device to the main machine; In step S2, after the host sends an authentication command to each slave, the slave receives the authentication command and returns a response to the host. At the same time, the slave performs a self-test. Whenever the format of the command sent by any slave is the same as that of another slave, it sends a fault record to the host and powers down the slave after a preset time to maintain normal system operation. The first authentication command is: BCU identification ID or BCU type + first authentication command; The slave device's response in one step consists of: first authentication command + BMU serial number + random number + authentication data; After the slave instruction format is sent to the host, a soft boot command message is sent to the host. The soft boot command message is a soft boot command plus the BMU sequence number. The slave device with the first BMU sequence number is designated as the first to start the host's battery management unit (BMU). If the slave device with the first BMU sequence number malfunctions or fails to send a soft-start command message after a preset time, the next slave device in sequence is used to replace it.

2. The low-voltage residential energy storage control method according to claim 1, characterized in that, The slave device's data information includes at least: the total battery voltage of each battery management unit (BMU), the voltage, temperature, remaining charge, battery health status, battery power status, main charge / discharge transistor status, and the PWM duty cycle value or switching status of the BUCK current limiting circuit's charge / discharge transistor.

3. The low-voltage residential energy storage control method according to claim 2, characterized in that, When the host is powered on and performs an initialization self-test in step S2, the following steps are also included: By physically activating the slave device, the power supply to the slave device circuit is enabled, thus powering on the slave device. After the slave device is powered on, the initialization output power is completed and the host device is started. The slave device reads the level information of the SW array and calculates its own BMU serial number. The BMU serial numbers of any two slave devices are different.

4. The low-voltage residential energy storage control method according to claim 3, characterized in that, Also includes: The slave device outputs VSQ2 at 100% duty and VSQ1 at PWM duty cycles from smallest to largest through the Buck circuit, supplying power to Pp and Pn to the bus. When the bus voltage and current rise to a certain value, the master device powers on and starts up. Once the slave device receives an authentication command from the master device, the master device starts up normally.

5. The low-voltage residential energy storage control method according to claim 4, characterized in that, Step S3, which involves performing secondary authentication on the secondary responses from each slave device after completing the secondary authentication, also includes: If the secondary authentication result is successful, the host will include the slave device in its management scope; otherwise, the slave device will be stopped from working. The secondary authentication command is: BCU identification ID or BCU type + second authentication command + random number + authentication data. The slave device's secondary response is: second authentication command + BMU serial number + authentication result.

6. The low-voltage residential energy storage control method according to claim 4, characterized in that, Step S4, which involves parallel operation, specifically includes: Once the slave device is connected to the Pn or Pp power bus, it begins to upload its own real-time information. Based on the real-time information uploaded by each slave device, the master device prioritizes selecting slave devices whose battery voltage and current Pn and Pp bus voltages are within the set parallel operation threshold, and sends the parallel operation command starting from the slave device with the smaller sequence number. After receiving the parallel operation command, the slave device determines whether the voltage difference between the bus voltage and the battery voltage is within the set first parallel operation voltage threshold range. If it is, the master device sends the first parallel operation command, and the slave device performs the parallel operation. Otherwise, the master device selects a slave device between the first and second parallel operation voltage thresholds based on the real-time information, and sends the second parallel operation command according to the BMU serial number from smallest to largest. After receiving the parallel operation command, the slave device performs the BUCK charging and discharging current limiting operation until the voltage difference between the battery voltage and the bus voltage is less than the first parallel operation voltage threshold or the BUCK charging and discharging current is less than the set threshold. Only then does the slave device turn on the main charging tube and the main discharging tube, the BUCK circuit stops working, and the parallel operation is completed. When the voltage difference between the bus voltage and the battery voltage is greater than the second parallel voltage threshold, the host sends a parallel command according to the system's charging and discharging status. In the charging state, the host aggregates the charging current demand of all slave devices, enabling the paralleled batteries to charge at maximum charging power, and the bus voltage gradually rises. When the voltage difference between the bus voltage and the battery voltage is lower than the second parallel threshold, the host sends a second parallel command, and the slave device executes a BUCK discharge current limiting operation until the paralleling is completed. In the discharging state, the host monitors the battery voltage of the slave device to be paralleled in real time. When the bus voltage drops to a point where the voltage difference with the voltage to be paralleled is less than the second parallel threshold, the second parallel command is issued, and the BMU executes a BUCK discharge current limiting operation until the paralleling is completed.

7. A low-voltage residential energy storage parallel operation system, characterized in that, The energy storage parallel system adopts the low-voltage residential energy storage control method as described in any one of claims 1-6.

8. A circuit, belonging to a type of low-voltage residential energy storage control circuit, characterized in that, The circuit includes at least a battery control unit (BCU) circuit and a battery management unit (BMU) circuit, which are used to implement the low-voltage residential energy storage control method process as described in any one of claims 1-6.

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