High-safety explosion-proof lithium battery pack and parallel expansion equalization control method thereof

Abstract

The application discloses a high-safety explosion-proof lithium battery pack and a parallel expansion equalization control method thereof. The lithium battery pack comprises an explosion-proof housing and a lithium iron phosphate battery cell group arranged in the explosion-proof housing. The parallel system comprises at least two explosion-proof lithium battery packs. The method comprises the following steps: obtaining current feedback values of each branch of the explosion-proof lithium battery packs in the parallel system, and broadcasting the current information of each branch to each slave control module through a communication bus; each slave control module calculates an average current according to the received current information of all branches, and obtains a current equalization error by subtracting the average current from the current feedback value of the corresponding branch; the voltage outer loop output of the corresponding branch is superimposed with the compensation of the current equalization error to generate a given reference value of the current inner loop, and the PWM duty cycle of the bidirectional DC / DC converter connected in series at the output end of the corresponding explosion-proof lithium battery pack is adjusted according to the difference between the given reference value and the current feedback value of the corresponding branch, so that the output current of the corresponding branch is adjusted.

Description

Technical Field

[0001] This invention relates to the field of explosion-proof lithium battery power grid networking and power balancing control technology, and more specifically, to a high-safety explosion-proof lithium battery pack and its parallel expansion and balancing control method. Background Technology

[0002] Currently, lithium battery power supply systems used in industrial explosion-proof scenarios mostly adopt the method of directly connecting multiple sets of explosion-proof lithium batteries in parallel to achieve power expansion. They lack a precise branch current balancing control mechanism. Due to differences in cell consistency, line impedance deviation, and different operating temperatures, the output current of each lithium battery branch is prone to unevenness. Some branches will have overcurrent output, while others will operate under light load. This will not only cause inconsistent degradation of the lithium battery pack's charge and discharge life and poor overall power supply stability, but also result in high current imbalance in the parallel system. It cannot meet the high power and high stability explosion-proof power supply requirements. Moreover, traditional parallel control methods have poor adaptability and are difficult to achieve precise dynamic current sharing adjustment of multiple branches.

[0003] There is currently no effective solution to the above problems. Summary of the Invention

[0004] This invention provides a high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method, so as to at least solve the technical problems of poor battery pack operating condition consistency, low system power supply stability and insufficient reliability of capacity expansion operation in existing explosion-proof lithium battery pack parallel capacity expansion systems.

[0005] According to one aspect of the present invention, in order to achieve the above-mentioned objective, a high-safety explosion-proof lithium battery pack and its parallel expansion and equalization control method are provided. The high-safety explosion-proof lithium battery pack includes an explosion-proof housing and a lithium iron phosphate cell pack disposed inside the explosion-proof housing. The method includes the following steps: acquiring the current feedback value of each branch of the explosion-proof lithium battery pack in the parallel system; broadcasting the current information of each branch to each slave control module through a communication bus; each slave control module calculates the average current based on the received current information of all branches, and subtracts the average current from the current feedback value of the corresponding branch to obtain the current sharing error; superimposing the voltage outer loop output of the corresponding branch with the compensation amount of the current sharing error to generate a given reference value for the current inner loop; adjusting the PWM duty cycle of the bidirectional DC / DC converter connected in series at the output terminal of the corresponding explosion-proof lithium battery pack according to the difference between the given reference value and the current feedback value of the corresponding branch, so as to adjust the output current of the corresponding branch.

[0006] Furthermore, the voltage outer loop is: the difference between the system set output voltage and the output voltage of each explosion-proof lithium battery pack is sent to the PI regulator to obtain the voltage outer loop output.

[0007] Furthermore, the current sharing error is the average current minus the current feedback value of the corresponding branch. When the current sharing error is negative, the output voltage of the bidirectional DC / DC converter of the corresponding branch is reduced to decrease the branch output current. When the current sharing error is positive, the output voltage of the bidirectional DC / DC converter of the corresponding branch is increased to increase the branch output current.

[0008] Furthermore, it also includes a state of charge normalization and equalization step: each slave control module obtains the state of charge information of each branch and allocates the total load current according to the proportion of the state of charge of each branch to the total state of charge of all branches.

[0009] Furthermore, it also includes a temperature compensation step: each slave control module obtains the internal temperature of the corresponding explosion-proof lithium battery pack in real time. When the temperature of a certain explosion-proof lithium battery pack exceeds the preset temperature threshold, the current sharing coefficient of the branch is reduced until the temperature of the explosion-proof lithium battery pack drops back to a safe range.

[0010] Furthermore, the explosion-proof enclosure is equipped with a battery management system, which has a three-level protection architecture: cell-level overcharge and over-discharge protection, current-level overcurrent and short-circuit protection, and temperature-level overheat protection.

[0011] Furthermore, in the three-level protection architecture: cell-level protection prevents single-cell overcharging above 3.65V or over-discharging below 2.5V through voltage detection; current-level protection shuts off the MOSFET when the current exceeds 1C for a specified duration or exceeds 3C instantaneous value, and performs short-circuit hardware cutoff within microseconds; temperature-level protection monitors the temperature through NTC thermistors deployed on the tabs and cell surface, and performs derating or output cutoff when the temperature exceeds 130℃.

[0012] Furthermore, it also includes an automatic fault isolation step: when the slave control module detects an internal short circuit or thermal runaway fault in the corresponding explosion-proof lithium battery pack, the battery management system of the explosion-proof lithium battery pack controls the MOSFET to turn off and the DC fuse connected in series at the output terminal to physically disconnect, so that the faulty pack is automatically disconnected from the power bus, and the remaining non-faulty explosion-proof lithium battery packs continue to supply power to the load.

[0013] Furthermore, in the state of charge normalization balancing step, the target value of current distribution is calculated by multiplying the ratio of the state of charge of each branch to the sum of the state of charge of all branches by the total load current.

[0014] Furthermore, the number of explosion-proof lithium battery packs in the parallel system is N, and 2≤N≤6; each explosion-proof lithium battery pack is connected in parallel to the power bus and outputs to the 48V inverter or DC load, and each slave control module interacts with each other through the CAN communication bus; after parallel expansion, the system imbalance is controlled within 2%.

[0015] This invention collects the current of each parallel branch and broadcasts it across the entire network. It calculates the current sharing error based on the average current difference, and generates an inner current reference value by superimposing the voltage outer loop output. It dynamically adjusts the PWM duty cycle of the bidirectional DC / DC converter to achieve precise correction of the current in each branch. This effectively realizes dynamic current sharing balance control of multiple explosion-proof lithium battery packs in parallel, significantly reduces the current imbalance of the parallel system, ensures uniform load distribution and consistent operating conditions for each battery pack, and improves the overall power supply stability, operational reliability, and equipment lifespan of the explosion-proof lithium battery parallel expansion system. It is suitable for industrial explosion-proof power supply scenarios with multiple battery packs connected in parallel for expansion. Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0017] Figure 1 This is a flowchart of a high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method according to one embodiment of the present invention. Detailed Implementation

[0018] 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 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 should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0020] According to an embodiment of the present invention, a high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method are provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0021] The method embodiments can be executed in an electronic device or similar computing device that includes memory and a processor. Taking operation on a terminal as an example, the terminal may include one or more processors (processors may include, but are not limited to, central processing units (CPUs), graphics processing units (GPUs), digital signal processing (DSP) chips, microcontroller units (MCUs), field-programmable gate arrays (FPGAs), neural network processors (NPUs), tensor processors (TPUs), artificial intelligence (AI) type processors, etc.) and memory for storing data. Optionally, the terminal may also include transmission devices, input / output devices, and display devices for communication functions. Those skilled in the art will understand that the above structural description is merely illustrative and does not limit the structure of the terminal. For example, the terminal may include more or fewer components than described above, or have a different configuration than described above.

[0022] The memory can be used to store computer programs, such as application software programs and modules, like the computer program corresponding to the high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method in this embodiment of the invention. The processor executes various functional applications and data processing by running the computer program stored in the memory, thereby realizing the aforementioned high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method. The memory may include high-speed random access memory, and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory may further include memory remotely located relative to the processor, and these remote memories can be connected to the mobile terminal via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0023] The transmission device is used to receive or send data via a network. Specific examples of the network mentioned above may include a wireless network provided by the mobile terminal's communication provider. In one example, the transmission device includes a Network Interface Controller (NIC), which can connect to other network devices via a base station to communicate with the Internet. In another example, the transmission device may be a Radio Frequency (RF) module, used for wireless communication with the Internet.

[0024] Display devices can be, for example, touchscreen liquid crystal displays (LCDs) and touch displays (also referred to as "touchscreens" or "touch displays"). LCDs enable users to interact with the user interface of a mobile terminal. In some embodiments, the mobile terminal has a graphical user interface (GUI), which allows users to interact with the GUI through finger contact and / or gestures on a touch-sensitive surface. Optional human-computer interaction functions include: creating web pages, drawing, word processing, creating electronic documents, playing games, video conferencing, instant messaging, sending and receiving emails, call interfaces, playing digital video, playing digital music, and / or web browsing, etc. Executable instructions for performing the above human-computer interaction functions are configured / stored in one or more processor-executable computer program products or readable storage media.

[0025] Figure 1 This is a flowchart of a high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method according to one embodiment of the present invention, as follows: Figure 1 As shown, the high-safety explosion-proof lithium battery pack in this method includes an explosion-proof housing and a lithium iron phosphate cell pack disposed inside the explosion-proof housing, and includes the following steps:

[0026] Step S110: Obtain the current feedback value of each explosion-proof lithium battery pack branch in the parallel system, and broadcast the current information of each branch to each slave control module through the communication bus. The specific content is as follows:

[0027] In step S110, this invention performs real-time acquisition of the current signal of all branches in a parallel expansion power supply system composed of 2 to 6 sets of explosion-proof lithium battery packs. The entire system uses multiple lithium iron phosphate battery packs equipped with explosion-proof shells as the basic power supply unit. Each lithium battery pack independently constitutes a power supply branch, and all branches are connected in parallel through a power bus to uniformly provide power to a 48V inverter or DC load, which can meet the high-power expansion power supply requirements in industrial explosion-proof scenarios. During the entire process of normal system operation and load output, the system continuously monitors the operating status of each explosion-proof lithium battery pack output branch. The core acquisition parameter is the real-time output current feedback value of each branch, which serves as the basic raw data for subsequent current sharing and load distribution adjustment.

[0028] Each output branch of the explosion-proof lithium battery pack is independently equipped with a current detection unit, which can accurately capture real-time current operating data of the branch. This abandons the traditional coarse monitoring mode of collecting only the total current and achieves independent, high-precision acquisition of the current of each branch. The current acquisition process covers all operating conditions, including battery pack discharge, parallel expansion under load, and dynamic load switching. It can capture subtle changes in branch current caused by load fluctuations, differences in battery status, and changes in ambient temperature, ensuring the real-time nature and effectiveness of the acquired data. At the same time, in conjunction with the basic monitoring architecture of the battery management system, the current acquisition process can work in conjunction with system temperature monitoring, voltage monitoring, and fault monitoring to avoid blind spots in operating condition monitoring that exist in single data acquisition and provide complete data support for subsequent refined equalization control.

[0029] After completing the real-time acquisition of current feedback values ​​from each branch, the system relies on a dedicated CAN communication bus to achieve full-domain data interaction and broadcast transmission. The CAN communication bus, serving as the unified data interaction carrier for each branch's slave control module, possesses advantages such as strong anti-interference capability, high transmission rate, and good data synchronization, adapting to the stable data transmission requirements under complex industrial explosion-proof conditions. The system packages the real-time current feedback information acquired from each branch into a standard communication data frame and broadcasts it to all slave control modules within the parallel system via the CAN communication bus, rather than being limited to local storage and processing within a single branch.

[0030] The data broadcasting process features full-domain synchronization and seamless transmission. Regardless of the operating load, battery state of charge, or operating temperature of the corresponding branch, the current data of all branches is synchronously transmitted to every slave control module in real time. This ensures that any slave control module can obtain accurate current feedback data from all N branches in the parallel system. This data transmission mode completely solves the problem of isolated branch data in traditional parallel control systems, breaking the limitation of independent calculation for a single branch. It lays the core data foundation for subsequent unified calculation of the system average current, solving for accurate current sharing errors, and achieving dynamic current balance adjustment across branches by each slave control module. This ensures the accurate implementation of the subsequent dual-loop control strategy and ultimately supports the system in stably controlling the current imbalance within 2%.

[0031] Step S120: Each slave control module calculates the average current based on the received current information of all branches, and subtracts the average current from the current feedback value of the corresponding branch to obtain the current sharing error. The specific content is as follows:

[0032] In step S20, in the parallel expansion power supply system of multiple explosion-proof lithium batteries of the present invention, after the CAN bus broadcast synchronization of the current data of each branch of the entire network is completed, all slave control modules configured in the system will independently complete the unified current average calculation and error solution, completely eliminating the drawbacks of traditional single-branch independent control and no data communication. The system limits the number of parallel branches N to a range of 2≤N≤6. The current data of all explosion-proof lithium battery packs participating in parallel power supply have been synchronized to each slave control module in real time. Each slave control module can completely and accurately obtain the real-time current feedback value of all effective working branches of the current parallel system. There is no data loss, data delay or single-branch data closure, providing a complete data foundation for the accurate calculation of the average current across the entire area.

[0033] Each slave control module, based on the received effective current data from all branches, uniformly executes the logic for calculating the average total current of the system. Specifically, the slave control module aggregates the real-time current feedback values ​​of all normally functioning, fault-free, and isolated explosion-proof lithium battery pack branches within the parallel system, sums the current values ​​of all branches, and then divides the total current sum by the number of currently effective parallel branches to finally calculate the average current of the entire parallel power supply system. This average current accurately characterizes the standard optimal output current under the current system load conditions. It is the core benchmark parameter for achieving multi-branch current balancing and unified load distribution, and can adapt to complex operating conditions such as dynamic load fluctuations, battery SOC differences, and ambient temperature changes, exhibiting extremely strong adaptability.

[0034] After obtaining the system's overall average current, each slave control module performs targeted calculations to determine the current sharing error of its corresponding branch. The error calculation strictly follows the calculation logic defined in this invention: the average current calculated by the system is used as a benchmark value, and the real-time current feedback value of its corresponding explosion-proof lithium battery pack branch is subtracted to obtain the real-time current sharing error of that branch. Compared to traditional single-voltage closed-loop control and fixed-current distribution control methods, this error calculation method is based on the operating data of all branches in the network, rather than relying on local data of a single branch to determine the operating status. This accurately reflects the degree of deviation between a single branch and the overall balanced operating condition of the system, and truly locates the current imbalance problem in each branch.

[0035] The current sharing error obtained through this calculation method has a clearly defined positive and negative value, which can accurately distinguish the overcurrent and undercurrent operating states of branches, providing a quantitative basis for subsequent differentiated and precise control. Specifically, when the current sharing error is negative, it indicates that the actual output current of the corresponding branch is higher than the system average current, and the branch is in an overload output state; when the current sharing error is positive, it indicates that the actual output current of the corresponding branch is lower than the system average current, and the branch is in a light load and underoutput state. The positive and negative values ​​can intuitively determine the type of branch imbalance, providing a precise control basis for the subsequent fine-grained adjustment of the boost and buck converters.

[0036] Meanwhile, this current sharing error calculation logic can be integrated with the system's state-of-charge normalization balancing, temperature compensation mechanism, and automatic fault isolation function. When some battery packs in the system have low SOC, excessive temperature, or fault isolation branches, the slave control module can automatically remove abnormal current data from faulty branches and derating branches, and only use data from normally operating branches to calculate the average current and current sharing error. This ensures that the balancing control logic is not affected by faulty branches or abnormal operating conditions, and always maintains the accuracy and stability of the system's balancing control, ultimately ensuring that the current imbalance of the entire parallel expansion system is stably controlled within 2%.

[0037] Step S140: The voltage outer loop output of the corresponding branch is superimposed with the compensation amount of the current sharing error to generate a given reference value for the current inner loop. The PWM duty cycle of the bidirectional DC / DC converter connected in series at the output terminal of the corresponding explosion-proof lithium battery pack is adjusted according to the difference between the given reference value and the current feedback value of the corresponding branch, so as to adjust the output current of the corresponding branch. The specific content is as follows:

[0038] In step S140, in this embodiment, after obtaining the branch current sharing error, the slave control module needs to perform a compensation calculation on the current sharing error to obtain the compensation amount. This compensation amount is used to characterize the current correction amount required to eliminate the branch current deviation. The compensation amount can be obtained by proportionally adjusting the current sharing error to match the response speed of the control system and avoid the problems of control oscillation and excessive overshoot caused by directly using the original current sharing error in the calculation. This compensation amount represents the direction and magnitude of the branch current correction. If the current sharing error is positive, the compensation amount corresponds to positive correction; if the current sharing error is negative, the compensation amount corresponds to negative correction, thereby providing a current sharing correction component for the subsequent generation of the given reference value.

[0039] In this embodiment, the voltage outer loop output serves as the fundamental reference component for the current inner loop. The voltage outer loop operates by acquiring the system's set output voltage and the corresponding output voltage of the explosion-proof lithium battery pack. It then calculates the difference between these two voltages and inputs this difference into a PI controller for closed-loop processing. The output result is the voltage outer loop output. The voltage outer loop output primarily ensures the overall stability of the parallel system's bus output voltage, prioritizing the load side's requirements for output voltage levels. This allows the system output voltage to track the system's set output voltage, preventing large fluctuations in the parallel system's bus voltage. The voltage outer loop output forms the basis of the current inner loop's reference value.

[0040] In this embodiment, the slave control module superimposes the voltage outer loop output obtained from the corresponding branch with the aforementioned current sharing error compensation, and the superposition generates a given reference value for the current inner loop. This given reference value integrates two control objectives: on the one hand, it inherits the voltage outer loop output to ensure the overall output voltage index of the parallel system; on the other hand, it introduces the current sharing error compensation, embedding the current balancing correction requirements of each branch, so that the current given of each branch is no longer completely consistent, but dynamically corrected according to the deviation of the branch from the system average current, taking into account both system voltage stability and the current sharing control objective among multiple branches, which is different from the traditional control architecture where the voltage loop and current loop are independent.

[0041] In this embodiment, after the inner current loop obtains a given reference value, it performs a difference calculation between this given reference value and the current feedback value collected in real time by this branch to obtain the inner current loop deviation value. This inner current loop deviation value reflects the degree of deviation of the actual output current of the current branch from the ideal control target. The magnitude of the deviation value represents the adjustment force required, and the positive or negative sign of the deviation represents the direction of adjustment required. This deviation serves as the input basis for adjusting the bidirectional DC / DC converter. The bidirectional DC / DC converter is arranged in series at the output terminal of the corresponding explosion-proof lithium battery pack, which can realize bidirectional flow of electrical energy and flexibly adjust its output capability by changing the PWM duty cycle, adapting to the bidirectional charging and discharging working conditions of the parallel system.

[0042] In this embodiment, the slave control module adjusts the PWM duty cycle of the bidirectional DC / DC converter based on the deviation value of the current inner loop. When the current feedback value is lower than the given reference value, the PWM duty cycle of the bidirectional DC / DC converter is increased, increasing the output voltage of that branch and thus increasing the output current of that branch. When the current feedback value is higher than the given reference value, the PWM duty cycle of the bidirectional DC / DC converter is decreased, decreasing the output voltage of that branch and thus decreasing the output current of that branch. By continuously and dynamically adjusting the PWM duty cycle, the gap between the current feedback value and the given reference value of the current inner loop is continuously narrowed, ultimately achieving closed-loop regulation of the output current of the corresponding explosion-proof lithium battery pack branch.

[0043] In this embodiment, the aforementioned dual-loop superimposed control logic continuously cycles, combining the real-time refreshed current data of each branch via the CAN bus to continuously update the current sharing error, compensation amount, and the reference value given in the inner current loop, thereby achieving dynamic correction of the output current of each branch. This control method can be coordinated with state-of-charge normalization balancing, temperature compensation, and automatic fault isolation. When the state of charge or temperature of a branch changes, or when a faulty branch is isolated, the output of the outer voltage loop and the compensation amount of the current sharing error change synchronously and adaptively, ensuring that the control strategy remains effective. Ultimately, this keeps the current imbalance of the parallel system composed of 2-6 sets of explosion-proof lithium battery packs within 2%, ensuring the operational stability of the parallel expansion system.

[0044] Based on steps S110 to S140 above, in this embodiment of the invention, by collecting the current of each parallel branch and broadcasting it across the entire network, calculating the current sharing error based on the average current difference, and generating the current inner loop reference value by superimposing the output of the outer voltage loop, the PWM duty cycle of the bidirectional DC / DC converter is dynamically adjusted to achieve accurate correction of the current of each branch. This effectively realizes dynamic current sharing balance control of the parallel branches of multiple explosion-proof lithium battery packs, significantly reduces the current imbalance of the parallel system, ensures uniform load distribution and consistent operating conditions of each battery pack, improves the overall power supply stability, operational reliability and equipment lifespan of the explosion-proof lithium battery parallel expansion system, and is suitable for industrial explosion-proof power supply scenarios of parallel expansion of multiple battery packs.

[0045] The high-safety explosion-proof lithium battery pack and its parallel expansion and equalization control method of the present invention have the following outer voltage loop: the difference between the system set output voltage and the output voltage of each explosion-proof lithium battery pack is sent to the PI regulator to obtain the outer voltage loop output.

[0046] In this embodiment, the voltage outer loop is: the difference between the system set output voltage and the output voltage of each explosion-proof lithium battery pack is sent to the PI regulator to obtain the voltage outer loop output. This method can accurately close the loop voltage regulation, suppress the voltage fluctuation of the parallel bus, and provide a stable and accurate basic given component for the subsequent current inner loop current sharing control, effectively balancing the stability of the system output voltage and the current balancing accuracy of multiple branches.

[0047] Specifically, the current sharing error is the average current minus the current feedback value of the corresponding branch. When the current sharing error is negative, the output voltage of the bidirectional DC / DC converter of the corresponding branch is reduced to decrease the branch output current. When the current sharing error is positive, the output voltage of the bidirectional DC / DC converter of the corresponding branch is increased to increase the branch output current.

[0048] In this embodiment, the current sharing error is the average current minus the current feedback value of the corresponding branch. When the current sharing error is negative, the output voltage of the bidirectional DC / DC converter of the corresponding branch is reduced to decrease the branch output current. When the current sharing error is positive, the output voltage of the bidirectional DC / DC converter of the corresponding branch is increased to increase the branch output current. This accurate positive and negative error discrimination and corresponding voltage and speed regulation logic can correct the current deviation of each parallel branch in real time, quickly eliminate the uneven working conditions of heavy load and light load in the branch, and significantly improve the current sharing consistency and operation stability of the multi-battery parallel system.

[0049] Furthermore, it also includes a state of charge normalization and equalization step: each slave control module obtains the state of charge information of each branch and allocates the total load current according to the proportion of the state of charge of each branch to the total state of charge of all branches.

[0050] In this embodiment, a state of charge (SOC) normalization and balancing step is also included: each slave control module obtains the SOC information of each branch and allocates the total load current according to the proportion of the SOC of each branch to the total SOC of all branches. This allocation method can adaptively allocate the load according to the remaining charge status of each battery pack, avoiding unreasonable operating conditions such as light load for high SOC batteries and overload for low SOC batteries, effectively balancing the charging and discharging progress of each parallel battery pack, extending the overall battery pack life and further improving the working consistency of the parallel system.

[0051] This embodiment also includes a temperature compensation step: each slave control module obtains the internal temperature of the corresponding explosion-proof lithium battery pack in real time. When the temperature of a certain explosion-proof lithium battery pack exceeds the preset temperature threshold, the current sharing coefficient of the branch is reduced until the temperature of the explosion-proof lithium battery pack drops back to a safe range.

[0052] In this embodiment, a temperature compensation step is also included: each slave control module obtains the internal temperature of the corresponding explosion-proof lithium battery pack in real time. When the temperature of a certain explosion-proof lithium battery pack exceeds the preset temperature threshold, the current sharing coefficient of the branch is reduced until the temperature of the explosion-proof lithium battery pack drops back to a safe range. This temperature adaptive derating adjustment mechanism can promptly perform load current limiting protection on the high-temperature battery branch, effectively avoid the risk of battery high-temperature degradation and thermal runaway, and greatly improve the operational safety and environmental condition adaptability of the explosion-proof lithium battery parallel system.

[0053] Specifically, the explosion-proof enclosure is equipped with a battery management system, which has a three-level protection architecture: cell-level overcharge and over-discharge protection, current-level overcurrent and short-circuit protection, and temperature-level overheat protection.

[0054] In this embodiment, a battery management system is also installed inside the explosion-proof housing. The battery management system has a three-level protection architecture, which includes cell-level overcharge and over-discharge protection, current-level overcurrent and short-circuit protection, and temperature-level overheat protection. Through the layered and multi-dimensional protection architecture, the explosion-proof lithium battery pack can be comprehensively managed from three dimensions: cell voltage, circuit current, and operating temperature. This effectively reduces the probability of battery overcharge and over-discharge, overcurrent and short-circuit, and overheating failure, and significantly improves the working safety and explosion-proof reliability of the explosion-proof lithium battery pack itself.

[0055] Furthermore, in the three-level protection architecture: cell-level protection prevents single-cell overcharging above 3.65V or over-discharging below 2.5V through voltage detection; current-level protection shuts off the MOSFET when the current exceeds 1C for a specified duration or exceeds 3C instantaneous value, and performs short-circuit hardware cutoff within microseconds; temperature-level protection monitors the temperature through NTC thermistors deployed on the tabs and cell surface, and performs derating or output cutoff when the temperature exceeds 130℃.

[0056] In this embodiment, the three-level protection architecture includes: cell-level protection prevents single-cell overcharging above 3.65V or over-discharging below 2.5V through voltage detection; current-level protection shuts off the MOSFET when the current exceeds 1C for a specified duration or exceeds 3C instantaneous value, and performs short-circuit hardware cutoff within microseconds; temperature-level protection monitors the temperature through NTC thermistors deployed on the tabs and cell surface, and performs derating or output cutoff when the temperature exceeds 130°C. Relying on precise threshold judgment and rapid hardware response, the layered protection methods can achieve fine monitoring and rapid handling of cell voltage, circuit current, and battery temperature, promptly curbing the development of various abnormal operating conditions and further improving the fault resistance and safety of the explosion-proof lithium battery pack.

[0057] This embodiment also includes an automatic fault isolation step: when the slave control module detects an internal short circuit or thermal runaway fault in the corresponding explosion-proof lithium battery pack, the battery management system of the explosion-proof lithium battery pack controls the MOSFET to turn off and the DC fuse connected in series at the output terminal to physically disconnect, so that the faulty pack is automatically disconnected from the power bus, and the remaining non-faulty explosion-proof lithium battery packs continue to supply power to the load.

[0058] In this embodiment, an automatic fault isolation step is also included: when the slave control module detects an internal short circuit or thermal runaway fault in the corresponding explosion-proof lithium battery pack, the battery management system of the explosion-proof lithium battery pack controls the MOSFET to turn off and the DC fuse connected in series at the output terminal to physically disconnect, so that the faulty pack is automatically disconnected from the power bus, and the remaining non-faulty explosion-proof lithium battery packs continue to supply power to the load. Through the dual isolation method of electronic device shutdown and fuse physical disconnection, the faulty battery pack can be quickly disconnected from the parallel bus, avoiding the fault from spreading and affecting the remaining normal branches, ensuring that the parallel power supply system does not experience a complete power outage, and improving the system's fault tolerance and continuous power supply reliability.

[0059] In this embodiment, in the state of charge normalization and equalization step, the current distribution target value is calculated by multiplying the ratio of the state of charge of each branch to the sum of the state of charge of all branches by the total load current.

[0060] In this embodiment, in the state of charge (SOC) normalization balancing step, the current distribution target value is calculated by multiplying the ratio of the SOC of each branch to the total SOC of all branches by the total load current. The load distribution is accurately matched by the remaining capacity of each branch battery through a quantization ratio algorithm, so that the charging and discharging progress of each explosion-proof lithium battery pack tends to be consistent. This effectively solves the problems of uneven current distribution and premature aging caused by inconsistent SOC of different battery packs, and further improves the balancing accuracy and overall service life of the parallel system.

[0061] Specifically, the number of explosion-proof lithium battery packs in the parallel system is N, and 2≤N≤6; each explosion-proof lithium battery pack is connected in parallel to the power bus and outputs to the 48V inverter or DC load, and each slave control module interacts with each other through the CAN communication bus; after parallel expansion, the system imbalance is controlled within 2%.

[0062] In this embodiment, the number of explosion-proof lithium battery packs in the parallel system is N, and 2≤N≤6; each explosion-proof lithium battery pack is connected in parallel to the power bus and outputs to the 48V inverter or DC load, and each slave control module interacts with each other through the CAN communication bus; after parallel expansion, the system imbalance is controlled within 2%. By limiting the number of parallel branches, relying on high-speed and reliable CAN bus data interaction, and cooperating with high-precision current sharing control strategy, the output consistency after the parallel expansion of multiple battery packs is effectively guaranteed, the system current imbalance loss is greatly reduced, and the 48V power supply system is guaranteed to operate smoothly, with strong expansion adaptability and high control accuracy.

[0063] According to another embodiment of the present invention, a high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method are disclosed, the method comprising the following steps:

[0064] This method is applied to a parallel capacity expansion power supply system consisting of 2 to 6 48V / 20Ah explosion-proof lithium battery pack units. Each explosion-proof lithium battery pack unit includes an explosion-proof enclosure conforming to GB / T3836.2 standards, internal lithium iron phosphate battery cells, and a battery management system integrated within the explosion-proof enclosure with a three-level protection architecture for cells, current, and temperature. Each explosion-proof lithium battery pack unit has a bidirectional DC / DC converter connected in series at its output terminal. Each unit is configured with a corresponding slave control module, and all slave control modules are connected to a CAN communication bus. Multiple battery packs are connected in parallel via a power bus to supply power to a 48V inverter or DC load. The method includes the following steps:

[0065] Step 201: System Power-On Self-Test and Data Initialization: After the parallel system is powered on, each slave control module completes a hardware self-test, establishes a CAN communication bus handshake connection, and the battery management system of each explosion-proof lithium battery pack collects operating parameters such as cell voltage, circuit current, NTC thermistor temperature, and state of charge (SOC) of the unit to complete initial data sampling. After confirming that there are no hardware faults in all branches, it enters the normal parallel operation mode. If a unit is found to have a fatal fault such as a short circuit or over-temperature, the fault isolation process is executed directly.

[0066] Step 202, Branch Current Acquisition and Network Broadcast: Each slave control module acquires the current feedback value of the corresponding explosion-proof lithium battery pack branch in real time, encapsulates the current information of each branch into a communication data frame, and broadcasts it to all slave control modules in the parallel system through the CAN communication bus, so that each slave control module can obtain the real-time current feedback data of all normally operating branches.

[0067] Step 203: Calculate the average current and solve the current sharing error: Each slave control module calculates the average current of the parallel system branches based on all valid branch current information received from the CAN bus, and subtracts the current feedback value of the corresponding branch from the average current to obtain the current sharing error of that branch; when the current sharing error is negative, it means that the output current of that branch is higher than the average current of the system; when the current sharing error is positive, it means that the output current of that branch is lower than the average current of the system.

[0068] Step 204: Obtain the voltage outer loop output quantity through voltage outer loop calculation: Obtain the system set output voltage, collect the output voltage of each explosion-proof lithium battery pack, and send the difference between the system set output voltage and the output voltage of each explosion-proof lithium battery pack into the PI regulator for closed-loop calculation to obtain the voltage outer loop output quantity. This output quantity serves as the basic component given by the current inner loop to ensure the stability of the output voltage of the parallel power bus.

[0069] Step 205: Generate the reference value for the inner current loop and adjust the PWM duty cycle of the bidirectional DC / DC converter: Perform compensation calculation on the current sharing error obtained in step 203 to obtain the compensation amount for the current sharing error. Superimpose the output of the outer voltage loop with the compensation amount for the current sharing error to generate the reference value for the inner current loop. Calculate the difference between the reference value for the inner current loop and the corresponding branch current feedback value. Adjust the PWM duty cycle of the bidirectional DC / DC converter connected in series at the output terminal of the corresponding explosion-proof lithium battery pack based on this difference. When the current sharing error is negative, lower the output voltage of the bidirectional DC / DC converter to reduce the branch output current. When the current sharing error is positive, raise the output voltage of the bidirectional DC / DC converter to increase the branch output current, thereby realizing closed-loop regulation of the branch output current.

[0070] Step 206, State of Charge Normalization and Equalization Processing: Each slave control module obtains the state of charge information of all branches of the parallel system through the CAN bus, and processes it according to formula (1):

[0071] L 𝑡𝑎𝑟𝑔𝑒𝑡 =(𝑆𝑂𝐶 𝑖 / ∑𝑆𝑂𝐶 𝑗 )×𝐼 𝑡𝑜𝑡𝑎l (1)

[0072] Among them: 𝐼 𝑡𝑎𝑟𝑔𝑒𝑡 The target current allocation value for the i-th branch, i.e., the ideal current that this explosion-proof lithium battery pack branch should output; 𝑆𝑂𝐶 𝑖 This represents the state of charge (SOC) of the i-th explosion-proof lithium battery pack branch, i.e., the percentage of remaining battery capacity in this branch; 𝐼 𝑡𝑜𝑡𝑎l The total load current of the parallel system, i.e., the total output current that all parallel branches need to provide to the load; 𝑆𝑂𝐶 𝑗 This represents the state of charge of the j-th explosion-proof lithium battery pack branch.

[0073] Calculate the target value for current distribution in each branch, and distribute the total load current according to the ratio of the state of charge of each branch to the total state of charge of all branches. Branches with a higher state of charge bear a larger output current, while branches with a lower state of charge bear a smaller output current, thereby achieving coordinated charging and discharging progress of each battery pack.

[0074] Step 207, Temperature Compensation Control: Each slave control module reads the temperature data collected by the NTC thermistor inside the corresponding explosion-proof lithium battery pack in real time. When the internal temperature of a certain explosion-proof lithium battery pack exceeds the preset derating temperature threshold, the current sharing setpoint coefficient of that branch is reduced, and the output load of that branch is reduced. The battery temperature is continuously monitored until the temperature of the explosion-proof lithium battery pack drops back to the safe temperature range, and then the normal current sharing setpoint coefficient of that branch is restored.

[0075] Step 208, Real-time Monitoring of Level 3 Safety Protection: The battery management system continuously executes the level 3 protection logic; Cell-level protection monitors the cell voltage in real time to prevent single cell overcharging above 3.65V or over-discharging below 2.5V; Current-level protection monitors the circuit current, and when the current exceeds 1C for a specified time or a 3C instantaneous overcurrent occurs, it controls the MOSFET to turn off and completes short-circuit hardware cutoff in microseconds; Temperature-level protection collects the temperature based on the NTC thermistor on the electrode tab and cell surface, and when the temperature exceeds 130℃, it executes derating output or directly cuts off the output.

[0076] Step 209, Automatic Fault Isolation Judgment: The slave control module continuously monitors whether the corresponding explosion-proof lithium battery pack has an internal short circuit or thermal runaway fault; when a fault is determined, the battery management system controls the MOSFET to turn off, and at the same time the DC fuse connected in series at the branch output terminal is physically disconnected, so that the faulty battery pack is completely disconnected from the power bus; after the system removes the faulty branch, the remaining normal explosion-proof lithium battery pack continues to supply power to the load, and at the same time re-participates in the calculation of average current and total state of charge.

[0077] Step 210, Iterative Control: Return to step 202 and iteratively execute the entire process of current acquisition, current sharing calculation, dual-loop adjustment, SOC normalization and equalization, temperature compensation, safety protection and fault diagnosis. Continuously and dynamically correct the output current of each branch to control the current imbalance of the parallel expansion system within 2% until the system shuts down.

[0078] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods according to the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. The computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0079] Optionally, specific examples in this embodiment can refer to the examples described in the above embodiments and optional implementations, and will not be repeated here.

[0080] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0081] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some interfaces; indirect couplings or communication connections between units or modules may be electrical or other forms.

[0082] 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 units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0083] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0084] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0085] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method, wherein the high-safety explosion-proof lithium battery pack includes an explosion-proof shell and a lithium iron phosphate cell pack disposed inside the explosion-proof shell, characterized in that, Includes the following steps: Obtain the current feedback value of each explosion-proof lithium battery pack branch in the parallel system, and broadcast the current information of each branch to each slave control module through the communication bus. Each slave control module calculates the average current based on the current information received from all branches, and obtains the current sharing error by subtracting the average current from the current feedback value of the corresponding branch. The voltage outer loop output of the corresponding branch is superimposed with the compensation amount of the current sharing error to generate a given reference value for the current inner loop. The PWM duty cycle of the bidirectional DC / DC converter connected in series with the output terminal of the corresponding explosion-proof lithium battery pack is adjusted according to the difference between the given reference value and the current feedback value of the corresponding branch, so as to adjust the output current of the corresponding branch.

2. The high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method according to claim 1, characterized in that, The voltage outer loop is defined as follows: the difference between the system set output voltage and the output voltage of each explosion-proof lithium battery pack is sent to the PI regulator to obtain the voltage outer loop output.

3. The high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method according to claim 1, characterized in that, The current sharing error is the average current minus the current feedback value of the corresponding branch; when the current sharing error is negative, the output voltage of the bidirectional DC / DC converter of the corresponding branch is reduced to reduce the branch output current. When the current sharing error is positive, the output voltage of the bidirectional DC / DC converter of the corresponding branch is increased to increase the branch output current.

4. The high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method according to claim 1, characterized in that, It also includes a state of charge normalization and equalization step: each slave control module obtains the state of charge information of each branch and allocates the total load current according to the proportion of the state of charge of each branch to the total state of charge of all branches.

5. The high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method according to claim 1, characterized in that, It also includes a temperature compensation step: each slave control module obtains the internal temperature of the corresponding explosion-proof lithium battery pack in real time. When the temperature of a certain explosion-proof lithium battery pack exceeds the preset temperature threshold, the current sharing coefficient of the branch is reduced until the temperature of the explosion-proof lithium battery pack drops back to a safe range.

6. The high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method according to claim 1, characterized in that, The explosion-proof enclosure is also equipped with a battery management system, which has a three-level protection architecture: cell-level overcharge and over-discharge protection, current-level overcurrent and short-circuit protection, and temperature-level overheat protection.

7. The high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method according to claim 6, characterized in that, In the three-level protection architecture: cell-level protection prevents single-cell overcharging above 3.65V or over-discharging below 2.5V through voltage detection; current-level protection shuts off the MOSFET when the current exceeds 1C for a specified duration or exceeds 3C instantaneous value, and performs short-circuit hardware cutoff within microseconds; temperature-level protection monitors the temperature through NTC thermistors deployed on the tabs and cell surface, and performs derating or output cutoff when the temperature exceeds 130℃.

8. The high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method according to claim 1, characterized in that, It also includes an automatic fault isolation step: when the slave control module detects an internal short circuit or thermal runaway fault in the corresponding explosion-proof lithium battery pack, the battery management system of the explosion-proof lithium battery pack controls the MOSFET to turn off and the DC fuse connected in series at the output terminal to physically disconnect, so that the faulty pack is automatically disconnected from the power bus, and the remaining non-faulty explosion-proof lithium battery packs continue to supply power to the load.

9. The high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method according to claim 4, characterized in that, In the state of charge normalization balancing step, the target value of current distribution is calculated by multiplying the ratio of the state of charge of each branch to the sum of the state of charge of all branches by the total load current.

10. The high-safety explosion-proof lithium battery pack and its parallel capacity expansion and equalization control method according to claim 1, characterized in that, The number of explosion-proof lithium battery packs in the parallel system is N, and 2≤N≤6; each explosion-proof lithium battery pack is connected in parallel to the power bus and outputs to the 48V inverter or DC load; each slave control module interacts with each other through the CAN communication bus; the imbalance of the system after parallel expansion is controlled within 2%.

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