An on-line battery capacity determination system and its control method

Abstract

The application relates to the technical field of battery management, and discloses a battery online capacity checking system and a control method thereof. The system comprises multiple inspection modules, a common DC bus and an isolated bidirectional DC / DC converter. The multiple inspection modules are one-to-one correspondingly arranged with each battery monomer in a battery pack. Each inspection module comprises a non-isolated bidirectional DC / DC converter, which converts the voltage of the corresponding battery monomer into a first voltage and outputs the first voltage. The common DC bus converges the electric energy of the first voltage converted by each inspection module. The low-voltage side of the isolated bidirectional DC / DC converter is connected with the common DC bus, and the high-voltage side is used for being connected with a system DC bus. A monitoring platform is in communication connection with each inspection module and the isolated bidirectional DC / DC converter, and is used for controlling each inspection module to be connected with the common DC bus in time sharing mode, so that the battery monomer independent capacity checking and discharging are realized. The application can realize the single-level accurate capacity checking while controlling the hardware size.

Description

Technical Field

[0001] This application relates to the field of battery management technology, and in particular to an online battery capacity control system and its control method. Background Technology

[0002] In critical locations such as communication base stations, power substations, and data centers, lead-acid battery packs serve as backup power sources and are in a float charge state for extended periods. To ensure that the actual usable capacity of the batteries meets requirements, periodic capacity discharge tests are necessary to assess the state of health (SOH) and actual usable capacity of each battery cell.

[0003] Taking a typical power substation application scenario as an example, the nominal voltage of a single battery cell is only 2V, and the maximum discharge current of a single cell during full-capacity discharge can reach 200A. A battery bank may contain over 100 cells connected in series (for example, a 220V system consists of 108 2V batteries connected in series). Under this condition, if the connection line between the power module and the battery is too long, the 200A current will generate a significant voltage drop (ΔU=I×R) and copper loss heating (P=I²×R) on the transmission line. This not only degrades the accuracy of the full-capacity voltage sampling and the efficiency of discharge energy utilization, but may even cause safety hazards due to overheating. Therefore, full-capacity power modules typically need to be installed near the terminals of each battery cell, which places high demands on the module's size, power density, and efficiency.

[0004] There are two main capacity-based solutions in related technologies. The first is the single-cell capacity-based solution: each battery cell is equipped with an independent, isolated bidirectional DC / DC converter module. During discharge, this module draws energy from the individual battery cell, boosting the low voltage (2V or 12V) to the system DC bus voltage (e.g., 48V, 110V, or 220V), achieving constant current discharge and energy transfer for the individual cell. The second is the whole-cell capacity-based solution: the entire battery pack is connected to the AC grid through a centralized bidirectional AC / DC converter, and the entire pack is discharged in a constant current manner, with the released energy fed back to the grid.

[0005] The aforementioned technologies have at least the following shortcomings: For single-cell capacity solutions, isolated bidirectional DC / DC converters must integrate high-frequency transformers, power switching devices, drive circuits, control circuits, protection circuits, and heat dissipation structures, resulting in a large overall module size. At high power levels (2V / 200A), the transformer core and windings become even larger, often exceeding the capacity of the limited space (typically only tens of millimeters) within the battery cabinet, making it difficult to install individual modules for each battery. Furthermore, N batteries require N sets of isolated DC / DC modules, and the power devices, transformers, and heat sinks for each module must be selected to high specifications. The total system cost increases linearly with the number of battery cells, resulting in poor economic efficiency. Additionally, isolated topologies are typically less efficient than non-isolated topologies due to transformer iron losses, copper losses, and power device switching losses. The large number of modules installed in the enclosed space of the battery cabinet leads to poor heat dissipation, and the temperature rise can accelerate battery aging.

[0006] For the overall capacity scheme, only the overall terminal voltage and total discharge current can be collected during the discharge process. It is impossible to obtain the independent discharge curve and termination voltage of each individual cell. The true performance of individual lagging cells is masked by the average data of the whole group, making it difficult for maintenance personnel to accurately locate the deteriorated individual cells. Moreover, due to factors such as AC / DC topology, power device losses and power frequency isolation transformers, the AC / DC conversion efficiency is relatively low.

[0007] The root cause lies in the fact that related single-cell capacity approval schemes bundle "isolation function" and "conversion function" onto each individual battery cell. This results in the dispersed deployment of numerous bulky and costly isolated DC / DC converters, which fails to meet the installation constraints of the compact battery cabinet and leads to cost waste. Furthermore, the overall capacity approval scheme completely abandons the refined management capabilities at the individual cell level, sacrificing data accuracy for system simplification. In addition, conventional single-level isolation schemes (using isolated DC / DC converters directly on the individual cell side) or two-level isolation schemes (single-level isolation + system-level two-level isolation) also fail to balance size, efficiency, and cost. This is because isolated DC / DC converters require built-in high-frequency isolation transformers, isolation drives, safety capacitors, and other components. Consequently, they cannot meet the single-cell capacity approval requirements of large-capacity battery packs with a nominal voltage of 2V, a discharge current as high as 200A, and more than 100 individual cells.

[0008] Furthermore, during the time-sharing switching process, if the power switching device fails due to a short circuit, the above-mentioned single-unit capacity scheme may cause circulating current or even a short circuit accident; and in the face of combined fault conditions such as power failure and battery open circuit, the existing scheme lacks effective countermeasures to maintain the continuity of the entire series circuit. Summary of the Invention

[0009] In order to achieve precise capacity assessment at the individual battery level, while keeping the hardware size within the space that can be installed in existing battery cabinets, reducing the system cost to an acceptable level, and having a complete multi-level safety protection mechanism, this application provides an online capacity assessment system for batteries and its control method.

[0010] Firstly, this application provides an online capacity assessment system for storage batteries, which adopts the following technical solution: An online capacity assessment system for a storage battery includes: multiple inspection modules, each corresponding to a single battery cell in a battery pack; a first terminal of each inspection module connected to the corresponding battery cell; each inspection module includes a non-isolated bidirectional DC / DC converter for converting the voltage of the corresponding battery cell to a first voltage and outputting it; a common DC bus connected to the second terminal of each inspection module for collecting the electrical energy from the first voltage converted by each inspection module; isolated bidirectional DC / DC converters, fewer in number than the total number of battery cells in the battery pack, with the low-voltage side of each isolated bidirectional DC / DC converter connected to the common DC bus and the high-voltage side connected to the system DC bus; and a monitoring platform communicatively connected to each inspection module and each isolated bidirectional DC / DC converter for controlling each inspection module to access the common DC bus in a time-sharing manner, thereby enabling independent capacity assessment and discharge of individual battery cells.

[0011] By adopting the above technical solution, the function of the isolated bidirectional DC / DC converter, which requires independent configuration for each battery cell in the relevant single-cell capacity scheme, is split into two levels: a non-isolated primary converter on the single-cell side and an isolated secondary converter on the system side. These two levels are connected via a common DC bus, allowing the isolated bidirectional DC / DC converter to be shared by multiple batteries. On one hand, the non-isolated bidirectional DC / DC converter on the single-cell side eliminates the need for bulky magnetic components such as high-frequency transformers, significantly reducing the size of the inspection module, which can be installed close to the limited gap near the battery terminals. On the other hand, the high-cost, bulky isolation function is concentrated on the system side, reducing the number of configurations from N to one or a small number, thus eliminating the linear increase in system cost with the number of battery cells. Simultaneously, each battery cell is independently discharged and collected data via its own inspection module connected to the common DC bus in a time-sharing manner, enabling accurate measurement of the actual capacity and complete discharge curve of each cell.

[0012] Optionally, the number of inspection modules is N, and the number of isolated bidirectional DC / DC converters is M, where N≥2, M≥1, and M<N.

[0013] By adopting the above technical solution, the number of isolated bidirectional DC / DC converters is strictly less than the total number of battery cells, clarifying the "multi-cell sharing" architecture and further reducing system costs.

[0014] Optionally, the first voltage is 12V, and the voltage of the DC bus of the system is any one of 48V, 110V or 220V.

[0015] By adopting the above technical solution, the common DC bus uses a 12V standard voltage as the intermediate common channel. The system DC bus is compatible with multiple specifications such as 48V, 110V, and 220V, which correspond to typical application environments such as communication base stations, power operation power supplies, and substation DC systems, so that the same system architecture can be compatible with multiple field voltage levels.

[0016] Optionally, each of the inspection modules further includes a gating switch network, which is connected in series between the battery cell and the common DC bus. On the positive and negative connection paths of the battery cell, at least two switching devices are connected in series in each path to form a multi-switch series redundant structure.

[0017] By adopting the above technical solution, each polarity path is connected in series with at least two switching devices to form redundancy. Even if any single switch fails due to a short circuit, the other switch can still reliably disconnect the electrical connection between the battery and the common DC bus, preventing unexpected connection.

[0018] Optionally, each of the inspection modules also includes a voltage sampling circuit, a current sampling circuit, and a temperature sensor, which are used to collect the terminal voltage, core capacity discharge current, and battery body temperature of the corresponding battery cell, respectively, and upload the collected data to the monitoring platform through a communication bus.

[0019] By adopting the above technical solution, the inspection module collects data locally, with a short sampling line, effectively reducing the impact of line impedance on voltage sampling accuracy, and can reflect the battery body temperature in real time, providing accurate data for temperature compensation and over-temperature protection.

[0020] Optionally, an electronic switch module is also included, connected in series between the DC output terminal of the external charger powered by mains and the battery pack; the electronic switch module includes a power switch device and a power diode connected in reverse parallel with the power switch device, the electronic switch module is also communicatively connected to the monitoring platform, and the power switch device is controlled by the monitoring platform to switch on and off; the power diode is used to conduct when the mains power fails, so that the energy of the battery pack is fed to the system DC bus.

[0021] By adopting the above technical solution, the power switch is closed to supply power during float charging, and the power switch is opened during capacity testing to isolate the charger and ensure measurement accuracy. When the mains power fails, the parallel power diode is instantly forward-biased, achieving microsecond-level rapid switching and ensuring uninterrupted power supply to the load.

[0022] Optionally, it also includes a bidirectional AC / DC converter connected between the battery pack and the AC power grid to provide a full-capacity discharge path for the battery pack, so that the battery pack can discharge to the AC power grid via the bidirectional AC / DC converter to achieve full-capacity discharge.

[0023] By adopting the above technical solution, a bidirectional AC / DC converter can be optionally added to expand the overall capacity mode of the battery pack, and the entire battery pack can be discharged to the AC power grid through the converter.

[0024] Secondly, the control method for an online capacity assessment system for a storage battery provided in this application adopts the following technical solution: A control method for an online capacity-controlled battery system based on the first aspect described above includes the following steps: S1. Obtain the capacity instruction and select a target battery cell in the battery pack; S2. Send a bus access control command to each inspection module, so that only the target inspection module corresponding to the target battery cell is connected to the common DC bus, and the other inspection modules are kept disconnected from the common DC bus. S3. Send a start command to the target inspection module to start its non-isolated bidirectional DC / DC converter, and send a start command to the isolated bidirectional DC / DC converter to perform core capacity discharge on the target battery cell. S4. Receive the capacity data collected and uploaded in real time by the target inspection module. When the preset capacity termination condition is reached, send a disconnect command to all inspection modules to disconnect the target inspection module from the common DC bus. S5. After confirming that no battery cell is connected to the common DC bus, switch to the next target battery cell and repeat the above steps until the capacity of all or part of the battery cells is completed.

[0025] By adopting the above technical solution, the system performs time-division capacity allocation according to the sequence of "selection - access only the target module - start discharge - disconnect when termination conditions are met - switch after confirming empty bus", ensuring that at any given time only one battery is connected to the common DC bus, thereby avoiding the risk of multiple batteries in parallel circulating current or short circuit.

[0026] Optionally, on the positive and / or negative connection paths of the target inspection module, two switching devices are connected in series on each connection path, with one switching device near the battery cell end serving as the first switching device and the other switching device near the common DC bus end serving as the second switching device. In step S2, a bus access control command is sent to each inspection module to ensure that only the target inspection module corresponding to the target battery cell is connected to the common DC bus. This step includes the following sub-steps: S21. Only issue a closing command to the first switching device; S22. Read the voltage detection value of the voltage sampling point after the first switching device. If the voltage detection value is equal to the battery voltage, it is determined that the first switching device is normally closed. S23. Then, a closing command is sent to the second switching device to establish an energy path between the target battery cell and the common DC bus.

[0027] By adopting the above technical solution, the failed switching devices are actively screened before each closing, avoiding the risk of multiple batteries being connected in parallel when relying on a single switch and not knowing that it has a short circuit failure.

[0028] Optionally, it also includes a combined protection mechanism for mains power failure and individual battery cell failure: When a mains power failure is detected and a voltage drop or open circuit fault is reported by any inspection module, a closing command is sent to the inspection module corresponding to the faulty battery. A reverse operating command is sent to the isolated bidirectional DC / DC converter, enabling the isolated bidirectional DC / DC converter to draw power from the system DC bus, inject sustaining current into the node where the faulty battery is located via the common DC bus and the inspection module corresponding to the faulty battery, so as to maintain circuit continuity at the faulty battery node.

[0029] By adopting the above technical solution, under the combined conditions of mains power failure and individual cell failure, the normal battery energy in the system can be used to "self-rescue" by injecting sustaining current into the faulty battery node, maintaining the circuit continuity of the entire series discharge circuit, and improving power supply reliability.

[0030] In summary, this application includes at least one of the following beneficial technical effects: 1. Adopting a two-stage conversion architecture of "N non-isolated inspection modules + 1 or a few isolated bidirectional DC / DC converters", the large-volume magnetic components on the individual cell side are eliminated, and the size of the inspection module is greatly reduced (it can be controlled within 180mm×125mm×50mm). It can be directly installed in the limited gaps near the individual cell poles of existing standard battery cabinets without modifying the cabinet. The isolated bidirectional DC / DC converter is shared by multiple batteries, and the system cost no longer increases linearly with the number of battery cells. 2. Each battery cell is discharged independently by its own inspection module, and its terminal voltage and discharge current are collected independently. This allows for accurate determination of the actual capacity and complete discharge curve of each cell, so that lagging cells are no longer masked by the average performance of the whole group. The inspection module is installed nearby and the sampling line is short, which can compensate for the impact of line impedance voltage drop on sampling accuracy. The temperature sensor is attached nearby and can reflect the temperature of the battery body in real time. 3. Through a multi-level mechanism including software interlocking, dual-switch series redundancy, step-by-step closure and step-by-step verification, it ensures that only one battery is connected to the common DC bus at any given time, thus ensuring high safety. 4. The parallel power diodes in the electronic switch module enable microsecond-level rapid switching when the mains power fails, ensuring uninterrupted power supply to critical loads. Under the combined conditions of mains power failure and individual cell failure, the normal battery energy in the system can be used to "self-rescue" by injecting sustaining current into the faulty battery node, maintaining the circuit continuity of the entire series discharge circuit and improving power supply reliability. 5. The switch redundancy scheme can be flexibly expanded. A single positive / negative path can be configured with 2, 3 or more series-connected switching devices to adapt to different safety level usage scenarios. The monitoring platform integrates data storage, remote alarm and local interaction functions, and can retain battery operation and maintenance data throughout the entire life cycle, making it convenient for operation and maintenance personnel to trace the battery degradation process and improve the convenience of system operation and maintenance. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall structure of the online capacity approval system for batteries according to an embodiment of this application; Figure 2 This is a schematic diagram of energy flow in the float charge standby mode according to an embodiment of this application; Figure 3 This is a schematic diagram of energy flow in the online single-unit capacity mode of an embodiment of this application; Figure 4 This is a schematic diagram of energy flow under emergency power supply mode according to an embodiment of this application; Figure 5 This is a schematic diagram of energy flow during protection under the combined conditions of mains power failure and individual cell fault, as described in this application embodiment. Figure 6 This is a schematic diagram of the overall structure after adding a bidirectional AC / DC converter in the embodiment of this application; Figure 7 This is a flowchart of the control method according to an embodiment of this application; Figure 8 This is a detailed flowchart of the control method according to the embodiments of this application.

[0032] Explanation of reference numerals in the attached figures: 1. Inspection module; 2. Battery cell; 3. Common DC bus; 4. Isolated bidirectional DC / DC converter; 5. Monitoring platform; 6. Electronic switch module; 7. Bidirectional AC / DC converter. Detailed Implementation

[0033] The following combination Figures 1 to 8 This application will be described in further detail.

[0034] This application discloses an online capacity assessment system for storage batteries.

[0035] Reference Figure 1 The online capacity assessment system for batteries is used to assess the capacity of series-connected battery packs. The battery pack consists of multiple battery cells 2 connected in series. It mainly includes multiple inspection modules 1, a common DC bus 3, an isolated bidirectional DC / DC converter 4, a monitoring platform 5, and an electronic switch module 6.

[0036] In this embodiment, the battery pack is connected between an external charger (an AC / DC rectifier power supply in the diagram, using AC mains power as the input power) and the system DC bus, which supplies power to the equipment / load. The AC side of the external charger is connected to the AC power grid (AC_L, AC_N in the diagram), and the DC side is connected to the battery pack via electronic switch module 6. The voltage of the system DC bus is any one of 48V, 110V, or 220V.

[0037] Inspection module 1 is configured to correspond one-to-one with each battery cell 2 in the battery pack. The first terminal (input terminal) of each inspection module 1 is directly connected to the positive and negative terminals of the corresponding battery cell 2, and the second terminal (output terminal) is connected to the common DC bus 3. Inspection module 1 includes a non-isolated bidirectional DC / DC converter, used to convert the voltage of the corresponding battery cell 2 to a first voltage and output it; in this embodiment, the first voltage is 12V, meaning the common DC bus 3 is a 12V DC bus. Taking a battery cell 2 with a nominal voltage of 2V as an example, the non-isolated bidirectional DC / DC converter converts 2V to a stable 12V with a boost ratio of more than 6 times. Because it adopts a non-isolated boost topology, it eliminates the need for bulky magnetic components such as transformers. Combined with high-density power electronic solutions such as high switching frequency design, low on-resistance power devices, and optimized magnetic component layout, the overall size of the inspection module 1 can be controlled within 180mm×125mm×50mm, with a typical conversion efficiency of over 95%. It can be directly installed near the individual poles of the existing battery cabinet without changing the cabinet structure.

[0038] The common DC bus 3 is connected to the second end of each inspection module 1, serving as the intermediate common channel for energy gathering and distribution of all battery cells 2. It is laid in the battery cabinet along the battery pack layout direction to gather the electrical energy of the first voltage after transformation by each inspection module 1.

[0039] The number of isolated bidirectional DC / DC converters 4 is less than the total number of individual battery cells 2 in the battery pack. Their low-voltage side is connected to the common DC bus 3, and their high-voltage side is used to connect to the system DC bus. Assume there are N inspection modules 1 and M isolated bidirectional DC / DC converters 4, where N≥2, M≥1, and M<N. That is, the isolated bidirectional DC / DC converter 4 is shared by the entire pack or multiple cells within a pack; it can be a single unit or a small number of redundant sets. The isolated bidirectional DC / DC converter 4 adopts an isolated topology and has an internal high-frequency isolation transformer, providing electrical isolation compliant with safety regulations between the common DC bus 3 side and the system DC bus side. During full-capacity discharge, the isolated bidirectional DC / DC converter 4 operates in a low-voltage to high-voltage energy transfer mode, boosting and converting the battery discharge energy from the common DC bus 3 to the system DC bus for load consumption or system feedback.

[0040] The monitoring platform 5 is connected to each inspection module 1, the isolated bidirectional DC / DC converter 4, and the electronic switch module 6 via a communication bus (such as RS485 or CAN bus) to centrally schedule the working status of each unit and control each inspection module 1 to access the common DC bus 3 in a time-sharing manner, so as to realize the independent capacity discharge of each battery cell.

[0041] It should be noted that, in one embodiment, the monitoring platform 5 integrates a main control microcontroller, an RS485 / CAN communication circuit, a local data storage device, a touch display interactive panel, and a remote alarm output interface; the main control microcontroller has built-in interlock control program, a capacity calculation program, and a multi-level fault protection program; the local data storage device can store the historical capacity data of hundreds of battery groups for a long time; the remote alarm output interface supports uploading over-temperature, under-voltage, and switch fault signals to the data center operation and maintenance backend.

[0042] Electronic switch module 6 is connected in series between the DC output terminal of the external charger and the battery pack, used to connect or disconnect the power supply circuit from the external charger to the battery pack. Electronic switch module 6 includes a power switching device and a power diode connected in reverse parallel with the power switching device; the power diode is used to conduct when the mains power fails (at which time the external charger stops working due to the mains power interruption), allowing energy from the battery pack to be fed to the system DC bus. Electronic switch module 6 is also communicatively connected to monitoring platform 5, and its power switching device is controlled by monitoring platform 5.

[0043] Reference Figure 1 Each inspection module 1 integrates multiple functions such as parameter acquisition, primary non-isolated transformation, gating protection, and battery management system (BMS).

[0044] For parameter acquisition, the inspection module 1 also includes a voltage sampling circuit, a current sampling circuit, and a temperature sensor (not shown in the figure). The voltage sampling circuit is used to acquire the terminal voltage of the corresponding battery cell 2; the current sampling circuit is used to acquire the core discharge current of the corresponding battery cell; the temperature sensor (e.g., an NTC thermistor or thermocouple) is attached near the terminal of the battery cell 2 to acquire the temperature of the corresponding battery cell. Because the inspection module 1 is installed close to the battery, the sampling line is short, effectively reducing the impact of line impedance on voltage sampling accuracy and achieving high-precision local sampling compensation. The inspection module 1 is connected to the monitoring platform 5 via a communication bus to upload the acquired terminal voltage, core discharge current, and temperature data.

[0045] In terms of selective protection, each inspection module 1 also includes a selective switch network, which is connected in series between the battery cell 2 and the common DC bus 3. On the positive and negative connection paths of the battery cell 2, at least two switching devices (such as MOSFET power switches) are connected in series in each path, forming a multi-switch series redundant structure.

[0046] In one specific embodiment, a first positive switch and a second positive switch are connected in series between the positive terminal of the battery and the positive input terminal of the non-isolated bidirectional DC / DC converter; a first negative switch and a second negative switch are connected in series between the negative terminal of the battery and the negative input terminal of the non-isolated bidirectional DC / DC converter. Even if any single switch fails due to a short circuit, the other normal switch can still reliably disconnect the electrical connection between the battery cell 2 and the common DC bus 3, preventing accidental connection.

[0047] Understandably, in addition to the basic scheme of two switches connected in series, in high-safety-level scenarios, three power switching devices can be connected in series in the positive and negative paths respectively. The three-layer series connection forms multiple circuit breaker protection. If any one or two switches fail due to short circuit, the remaining switches can still reliably disconnect the electrical connection between the battery and the common DC bus, further improving safety under extreme fault conditions.

[0048] Furthermore, a fuse (not shown in the figure) is connected in series in the connection path of the corresponding battery cell 2 as a last-line backup protection: when both series switches fail to short-circuit and the system fails to detect the extreme situation, the abnormally large current will cause the fuse to irreversibly blow, physically disconnecting the battery connection completely. Specifically, the fuse is a slow-blow type power fuse with a rated current matching the maximum discharge current of the corresponding inspection module. It can be configured individually in the positive path, negative path, or both positive and negative paths to achieve dual physical fuse protection.

[0049] It is understood that the safety constraint of this application is that at any given time, only one battery cell 2 can be connected to the common DC bus 3. If multiple battery cells 2 are connected simultaneously, it will cause batteries of different voltage levels to be directly connected in parallel through the common DC bus 3, resulting in uncontrolled circulating current or even a short circuit. To achieve this constraint, the system adopts the following multi-level safety control mechanism.

[0050] One approach is a software interlock strategy. In one embodiment, the monitoring platform 5 also executes the following interlock control: before issuing a selection command to the inspection module 1 corresponding to the selected battery cell 2, it first confirms that no other battery cell 2 is connected on the common DC bus 3; after the current battery cell 2's capacity verification operation is completed and its selection switch is confirmed to be off, the next battery cell 2 is selected. The monitoring platform 5 maintains a global status table, recording the switch status, working mode, and operating parameters of each inspection module 1. Any status change must be verified by the interlock condition.

[0051] Understandably, the global status table is updated in real time with the switch-closed status of all inspection modules, the current capacity operation status, and the fault mark status. Before any control command is issued, the global status table is read to complete the verification. If the verification fails, the circuit breaker command is rejected and an alarm is reported, thus preventing the abnormal operation of multiple batteries being connected to the bus at the same time from the software level.

[0052] The second is hardware dual-switch series redundancy, which is the multi-switch series structure of the above-mentioned gating switch network.

[0053] Thirdly, there is a step-by-step closure and step-by-step verification mechanism, which is detailed in the control method section below. Fourthly, there is a backup protection mechanism with a terminal fuse, namely the fuse connected in series in the connection path.

[0054] Based on the above hardware architecture, the system can intelligently switch between the following working states through software scheduling of monitoring platform 5.

[0055] Reference Figure 2 In float charging standby mode: With normal mains power, the power switch of electronic switch module 6 is closed, and the external charger float charges the battery pack and supplies power to the load via electronic switch module 6. All conversion functions of inspection modules 1 are not activated; only daily parameter acquisition and reporting are performed.

[0056] Reference Figure 3Online single-cell capacity verification status: With normal mains power, the power switch of electronic switch module 6 is disconnected to isolate the external charger, ensuring the purity and measurement accuracy of the capacity verification discharge data. Monitoring platform 5 selects the battery cell 2 under test, closes the selection switch of its corresponding inspection module 1, and starts the first-stage non-isolated bidirectional DC / DC converter. The energy of battery cell 2 is transferred to the isolated bidirectional DC / DC converter 4 via the common DC bus 3, boosted, and fed into the system DC bus for load consumption. The load is simultaneously powered by the output of the isolated bidirectional DC / DC converter 4 and the external charger, which is still connected to normal mains power. During the capacity verification process, inspection module 1 collects parameters such as voltage, temperature, and current of battery cell 2 in real time. Based on preset discharge current, discharge time, termination voltage, and termination temperature conditions, it determines the termination of the capacity verification and records the discharge curve and actual capacity.

[0057] Reference Figure 4 Emergency power supply status: When the mains power is abnormal and the external charger stops working, the power diodes connected in parallel inside the electronic switch module 6 are instantly forward-biased, and the battery pack directly supplies power to the load on the system's DC bus online. The switching time is in the microsecond range.

[0058] Reference Figure 5 Composite fault protection state: When the mains power failure and the single cell battery 2 are severely undervoltage or open circuit faults occur simultaneously, the monitoring platform 5 actively closes the switching device in the inspection module 1 corresponding to the faulty battery, and controls the isolated bidirectional DC / DC converter 4 to work in the energy transfer mode from the high voltage side to the low voltage side, so that it draws energy from the system DC bus (this energy comes from the backup power provided by the power diodes of the other normal cells in the battery pack through the electronic switch module 6), and injects a sustaining current into the node where the faulty battery is located through the common DC bus 3 and the inspection module 1 corresponding to the faulty battery, so as to support its terminal voltage to a safe range or bypass equivalent voltage, ensuring that the entire series discharge circuit will not be interrupted due to the failure of a single cell battery, and ensuring the continuous power supply to the downstream load.

[0059] Reference Figure 6 To expand the system's application flexibility, a bidirectional AC / DC converter 7 can be optionally installed, connected between the battery pack and the AC power grid. The bidirectional AC / DC converter 7 is an optional configuration unit; its connection or disconnection does not affect the independent operation of the individual unit capacity-based function based on the inspection module 1 and the isolated bidirectional DC / DC converter 4. The bidirectional AC / DC converter 7 provides a complete capacity-based discharge path for the battery pack, enabling the battery pack to discharge into the AC power grid via the bidirectional AC / DC converter 7, thus achieving complete capacity-based discharge. The bidirectional AC / DC converter 7 communicates with the monitoring platform 5 via a communication bus (such as RS485 or CAN bus).

[0060] Understandably, in the overall capacity verification mode, for a system equipped with a bidirectional AC / DC converter 7, the monitoring platform 5 issues an overall capacity verification command to control the bidirectional AC / DC converter 7 to operate in inverter mode. The DC power output of the battery pack is converted into AC power by the bidirectional AC / DC converter 7 and fed back to the AC grid. The total voltage and total discharge current of the battery pack are collected throughout the process to calculate the actual capacity of the entire pack and complete the overall battery capacity verification test.

[0061] It should be noted that the monitoring platform 5 can independently control the bidirectional AC / DC converter 7 to operate in two modes: inverter discharge and rectification charging. In inverter mode, the entire battery pack is discharged, and in rectification mode, the power grid provides the entire battery pack with additional power. The entire battery pack discharge mode and the individual battery pack discharge mode are mutually exclusive, and only one discharge process is allowed to operate at the same time to prevent the two discharge circuits from operating simultaneously and generating circulating current.

[0062] Reference Figure 7 and Figure 8 This application also provides a control method based on the above-mentioned online capacity assessment system for batteries, executed by the monitoring platform 5, which includes the following steps, taking online single-cell capacity assessment as an example: S1. Obtain the capacity control instruction and select a target battery cell 2 in the battery pack. At this time, the electronic switch module 6 is disconnected, isolating the external charger from the battery pack.

[0063] S2. Send a bus access control command to each inspection module 1, so that only the target inspection module 1 corresponding to the target battery cell 2 is connected to the common DC bus 3, and the other inspection modules 1 are kept disconnected from the common DC bus 3.

[0064] In the target inspection module 1, on the positive and / or negative connection paths, each connection path has two switching devices connected in series. One switching device near the battery cell 2 is the first switching device, and the other switching device near the common DC bus 3 is the second switching device.

[0065] Step S2 specifically includes the following sub-steps: S21. Only a closing command is sent to the first switching device. At this time, the battery cell 2 has not yet formed a complete power path with the common DC bus 3. S22. Read the voltage detection value of the voltage sampling point after the first switching device (the voltage sampling point after the first switching device and before the second switching device, starting from the positive terminal of the battery). If the voltage detection value is equal to the battery voltage, it is determined that the first switching device is closed normally. If the detection result is consistently zero or much lower than the normal battery voltage, it is determined that the switch has failed to close reliably or has been damaged. The current closing process is immediately stopped, the inspection module 1 is marked as faulty and an alarm is issued. S23. After confirming that the first switching device is normal, a closing command is sent to the second switching device to establish an energy path between the target battery cell 2 and the common DC bus 3.

[0066] It should be noted that the implementation of the above-mentioned step-by-step closure and step-by-step verification mechanism is premised on the presence of a gating switch network in the inspection module 1. Specifically, when the battery online capacity assessment system adopts the aforementioned inspection module 1 including the gating switch network (i.e., each inspection module 1 has at least two switching devices connected in series on each of the positive and negative connection paths of the battery cell 2, forming a multi-switch series redundant structure), the bus access control in step S2 can be further refined into the following step-by-step closure and step-by-step verification sub-steps to fully utilize the dual-switch series structure to actively detect the health status of the switching devices before closing. In a system configuration without a gating switch network, step S2 can achieve the access control of the inspection module 1 and the common DC bus 3 through other means (e.g., direct closure of a single switch combined with bus voltage monitoring).

[0067] S3. A start command is sent to the target inspection module 1 to start its non-isolated bidirectional DC / DC converter, and a start command is sent to the isolated bidirectional DC / DC converter 4 to perform full-capacity discharge on the target battery cell 2. The battery energy is transferred to the isolated bidirectional DC / DC converter 4 via the common DC bus 3, boosted, and then fed into the system DC bus.

[0068] S4. Receive the capacity data (terminal voltage, capacity discharge current, battery body temperature, etc.) collected and uploaded in real time by the target inspection module 1. When it is determined that the preset capacity termination condition has been met, send a disconnect command to all inspection modules 1 to disconnect the connection between the target inspection module 1 and the common DC bus 3.

[0069] It should be noted that sending a disconnect command to all inspection modules 1 (rather than just the target inspection module 1) in step S4 is for safety redundancy design considerations. In the normal process, step S2 has ensured that only the target inspection module 1 is connected to the common DC bus 3, while the other inspection modules 1 are in a disconnected state. However, in actual engineering operation, there may be abnormal situations such as communication bus delay, command loss, and untimely feedback of abnormal status of switching devices, which may cause the switching device of a non-target inspection module 1 to be in an unexpected and uncertain state. Therefore, at the end of each round of capacity discharge, the monitoring platform 5 broadcasts a disconnect command to all inspection modules 1, causing all inspection modules 1 (regardless of their current state) to perform a deterministic disconnection action, thereby forcibly clearing the common DC bus 3 to a safe baseline state without battery connection, providing a reliable premise for the interlock verification in step S5 and the safe connection of the next battery. This design achieves system-level deterministic safety assurance with extremely low communication overhead, avoiding potential parallel risks that may be missed due to reliance on single-point status feedback.

[0070] Specifically, the preset capacity verification termination conditions include any one of the following: the terminal voltage of the target battery cell 2 reaches the preset termination voltage; the capacity verification discharge time reaches the preset termination time; the capacity verification discharge capacity reaches the preset termination capacity; the temperature of the target battery cell 2 reaches the preset termination temperature. During the capacity verification process, the monitoring platform 5 continuously monitors the voltage of the common DC bus 3 and the current feedback of each inspection module 1. If an abnormality in the bus voltage or an abnormality in the current fluctuation is detected, all switching devices of the corresponding inspection module 1 are immediately disconnected simultaneously.

[0071] It should be noted that in other embodiments, a sudden increase in battery internal resistance or abnormal overcurrent of the bus can also be configured as termination conditions. Once the above parameters are detected to be abnormal, the current single-cell capacity control process is immediately interrupted and all switches are disconnected.

[0072] S5. After confirming that no battery cell 2 is connected to the common DC bus 3 (interlock verification passed), switch to the next target battery cell 2 and repeat the above steps until the capacity verification of all or part of the battery cells 2 is completed. After the capacity verification of all battery cells 2 is completed, the electronic switch module 6 closes, the system returns to the float charging standby state, and a capacity verification report is generated and uploaded to the monitoring platform 5.

[0073] In one embodiment, such as Figure 4 As shown, the control method also includes a mains power failure emergency protection step: when a mains power failure is detected, all ongoing capacity-saving operations are immediately stopped; a disconnect command is sent to all inspection modules 1 (locking the switch drive signals of all inspection modules 1, prohibiting any inspection module 1 from reconnecting to the common DC bus 3), to disconnect from the common DC bus 3; a blocking command is sent to the isolated bidirectional DC / DC converter 4, causing the system to switch to backup power supply mode, prioritizing the supply of all energy from the battery pack to the downstream load. The power diode in the electronic switch module 6, connected in series between the DC output terminal of the external charger and the battery pack, is momentarily forward biased and conducts when the mains power fails. The energy from the battery pack is fed to the system DC bus through this diode to supply power to the downstream load. The switching time is in the microsecond range and requires no control signal intervention.

[0074] In one embodiment, such as Figure 5As shown, the control method also includes a composite protection step involving mains power failure and individual cell faults: When a mains power failure is detected, and a voltage drop or open-circuit fault is reported by any inspection module 1 for a certain battery cell 2, a closing command is sent to the inspection module 1 corresponding to the faulty battery to close its switching device; a reverse working command is sent to the isolated bidirectional DC / DC converter 4 to control it to operate in the energy transfer mode from the high-voltage side to the low-voltage side, so that the isolated bidirectional DC / DC converter 4 draws energy from the system DC bus, injects a sustaining current into the node where the faulty battery is located through the common DC bus 3 and the inspection module 1 corresponding to the faulty battery, so as to maintain the circuit continuity of the faulty battery node. This function uses the normal battery energy in the system to "self-rescue" and maintain the circuit continuity of the faulty battery node, ensuring that the power supply capacity of the entire battery pack is not completely paralyzed due to a single point of failure at the lowest cost.

[0075] Reference Figure 6 In a system equipped with a bidirectional AC / DC converter 7, the control method also includes a full-group capacity verification step executed by the monitoring platform 5: obtaining a full-group capacity verification command; controlling the bidirectional AC / DC converter 7 to operate in inverter mode; the entire battery pack supplies DC power to the bidirectional AC / DC converter 7 via the system DC bus, the bidirectional AC / DC converter 7 inverts the DC power into AC power and feeds it into the AC grid, and discharges the entire pack with a preset constant current to achieve full-group capacity verification discharge.

[0076] It is understandable that the system of this application can realize the core capacity discharge function of individual battery cells, as well as the core capacity discharge of the entire battery pack, and also constructs a multi-level, full-condition fault protection system.

[0077] Routine battery status anomaly protection: The system continuously monitors each battery cell 2 online through each inspection module 1. When the voltage of battery cell 2 is higher than the preset overvoltage threshold or lower than the preset undervoltage threshold, an anomaly is marked and an alarm is reported. If necessary, the energy path of the battery is cut off. When the battery internal resistance exceeds the preset degradation threshold, a maintenance warning is issued. When the battery terminal temperature exceeds the preset overtemperature threshold, it is determined that there is a risk of thermal runaway. The current capacity operation of the battery is immediately stopped and an emergency shutdown command is issued. The system supports the freezing and storage of fault data. When protection is triggered, the bus voltage, current, temperature and switch status at the time of the fault are recorded simultaneously for easy fault tracing and analysis in the future.

[0078] Power level protection during the capacity expansion process: For overvoltage and undervoltage protection, the system continuously monitors the voltage of the common DC bus 3, the system DC bus voltage, and the terminal voltage of each operated unit. If any voltage exceeds the preset safety range, the operation is immediately stopped, the corresponding switching device of the inspection module 1 is disconnected, and the drive pulse of the isolated bidirectional DC / DC converter 4 is blocked. For overcurrent and short-circuit protection, the system monitors the current flowing through the isolated bidirectional DC / DC converter 4, each inspection module 1, and the common DC bus 3 in real time. When the current exceeds the preset threshold or a short-circuit characteristic waveform occurs, the hardware overcurrent protection circuit responds quickly by cycle-by-cycle current limiting or direct blocking. Simultaneously, after software confirmation, the corresponding switching device is disconnected, achieving synergy between microsecond-level hardware protection and millisecond-level software protection. For power device fault protection, when a fault such as abnormal drive, overheating, or breakdown is detected in the switching device inside the isolated bidirectional DC / DC converter 4 or inspection module 1, the relevant drive signal is immediately blocked, and the faulty unit is isolated to prevent the fault from spreading.

[0079] The implementation principle of the online capacity assessment system for batteries in this application embodiment is as follows: By splitting the function of the isolated bidirectional DC / DC converter, which is independently configured for each battery in the traditional single-cell capacity assessment, into a non-isolated primary conversion in the single-cell inspection module 1 and an isolated secondary conversion in the system-side isolated bidirectional DC / DC converter 4, and using the 12V common DC bus 3 as the intermediate common channel, N small non-isolated inspection modules 1 can complete the time-sharing independent capacity assessment of each battery cell 2 with one or a few isolated bidirectional DC / DC converters 4; with the multi-level safety mechanism of software interlocking, dual-switch series redundancy, step-by-step closure verification and end fuse, it is ensured that only one battery cell 2 is connected to the common DC bus 3 at any time; and with the help of the parallel power diodes of the electronic switch module 6 and the bidirectional energy transfer capability of the isolated bidirectional DC / DC converter 4, microsecond-level switching of mains power failure and node maintenance under compound faults are achieved, thereby achieving accurate single-cell capacity assessment and high-reliability power supply under the premise of small size and low cost.

[0080] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A battery online capacity assessment system, characterized in that, include: Multiple inspection modules (1) are configured to correspond one-to-one with each battery cell (2) in the battery pack. The first end of each inspection module (1) is connected to the corresponding battery cell (2). The inspection module (1) includes a non-isolated bidirectional DC / DC converter. The non-isolated bidirectional DC / DC converter adopts a non-isolated boost topology and is used to convert the voltage of the corresponding battery cell (2) into a first voltage with a boost ratio of more than 6 times and output it. A common DC bus (3) is connected to the second end of each inspection module (1) to collect the electrical energy of the first voltage after transformation by each inspection module (1); each inspection module (1) also includes a selection switch network, which is connected in series between the battery cell (2) and the common DC bus (3). On the positive and negative connection paths of the battery cell (2), at least two switching devices are connected in series in each path to form a multi-switch series redundant structure. The isolated bidirectional DC / DC converter (4) is less than the total number of battery cells (2) in the battery pack. The low-voltage side of the isolated bidirectional DC / DC converter (4) is connected to the common DC bus (3), and the high-voltage side is used to connect to the system DC bus. The monitoring platform (5) is connected to each of the inspection modules (1) and the isolated bidirectional DC / DC converter (4) respectively, and is used to control each of the inspection modules (1) to access the common DC bus (3) in a time-sharing manner, so as to realize the independent capacity discharge of the battery cell (2).

2. The online capacity assessment system for storage batteries according to claim 1, characterized in that, The number of inspection modules (1) is N, and the number of isolated bidirectional DC / DC converters (4) is M, where N≥2, M≥1, and M<N.

3. The online capacity assessment system for storage batteries according to claim 1, characterized in that, The first voltage is 12V, and the voltage of the DC bus of the system is any one of 48V, 110V or 220V.

4. The online capacity assessment system for storage batteries according to claim 1, characterized in that, Each of the inspection modules (1) further includes: Voltage sampling circuit, used to collect the terminal voltage of the corresponding battery cell (2); A current sampling circuit is used to collect the core discharge current of the corresponding battery cell (2); A temperature sensor is attached near the terminal of a battery cell (2) to collect the temperature of the corresponding battery cell (2); the inspection module (1) is connected to the monitoring platform (5) via a communication bus to upload the collected terminal voltage, core discharge current and temperature data.

5. The online capacity assessment system for storage batteries according to claim 1, characterized in that, Also includes: The electronic switch module (6) is connected in series between the DC output terminal of the external charger powered by the mains and the battery pack; The electronic switch module (6) includes a power switch device and a power diode connected in reverse parallel with the power switch device; the electronic switch module (6) is also connected to the monitoring platform (5) for communication, and the power switch device is controlled by the monitoring platform (5) to switch on and off. The power diode is used to conduct when the mains power fails, so that the energy of the battery pack is fed to the DC bus of the system.

6. The online capacity assessment system for storage batteries according to claim 1, characterized in that, It also includes a bidirectional AC / DC converter (7) connected between the battery pack and the AC power grid; the bidirectional AC / DC converter (7) is used to provide a full-capacity discharge path for the battery pack, so that the battery pack can be discharged to the AC power grid via the bidirectional AC / DC converter (7) to achieve full-capacity discharge.

7. A control method for an online capacity-matching system for a storage battery according to any one of claims 1 to 6, characterized in that, Including the following steps: S1. Obtain the capacity instruction and select a target battery cell in the battery pack (2). S2. Send a bus access control command to each inspection module (1) to enable only the target inspection module (1) corresponding to the target battery cell (2) to access the common DC bus (3), and keep the other inspection modules (1) disconnected from the common DC bus (3); S3. Send a start command to the target inspection module (1) to start its non-isolated bidirectional DC / DC converter, and send a start command to the isolated bidirectional DC / DC converter (4) to perform core capacity discharge on the target battery cell (2); S4. Receive the capacity data collected and uploaded in real time by the target inspection module (1). When the preset capacity termination condition is reached, send a disconnect command to all inspection modules (1) to disconnect the target inspection module (1) from the common DC bus (3). S5. After confirming that no battery cell (2) is connected on the common DC bus (3), switch to the next target battery cell (2) and repeat the above steps until the capacity of all or part of the battery cells (2) is completed.

8. The control method according to claim 7, characterized in that, On the positive and / or negative connection paths of the target inspection module (1), two switching devices are connected in series on each connection path. One switching device near the battery cell (2) is the first switching device, and the other switching device near the common DC bus (3) is the second switching device. In step S2, a bus access control command is sent to each inspection module (1) to enable only the target inspection module (1) corresponding to the target battery cell (2) to access the common DC bus (3). This includes the following sub-steps: S21. Only issue a closing command to the first switching device; S22. Read the voltage detection value of the voltage sampling point after the first switching device. If the voltage detection value is equal to the battery voltage, it is determined that the first switching device is normally closed. S23. Then send a closing command to the second switching device to establish an energy path between the target battery cell (2) and the common DC bus (3).

9. The control method according to claim 7, characterized in that, It also includes a composite protection mechanism for mains power failure combined with individual battery cell failure: When a mains power failure is detected and a voltage drop or open circuit fault is reported by any inspection module (1) for a single battery cell (2), a closing command is sent to the inspection module (1) corresponding to the faulty battery. Send a reverse working command to the isolated bidirectional DC / DC converter (4) so ​​that the isolated bidirectional DC / DC converter (4) draws power from the system DC bus and injects a sustaining current into the node where the faulty battery is located through the common DC bus (3) and the inspection module (1) corresponding to the faulty battery, so as to keep the circuit continuity of the faulty battery node.

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