Integrated circulating charging lithium battery intelligent charging and discharging control system

Abstract

This invention discloses an integrated intelligent charging and discharging control system for a cyclic-chargeable lithium battery, comprising a main control unit, a bidirectional power conversion unit, a cyclic energy recovery buffer unit, a battery pack acquisition unit, a multi-dimensional sensing unit, an active balancing unit, a hierarchical protection unit, and a communication interaction unit. The bidirectional power conversion unit adopts a time-division multiplexing architecture to achieve integrated charging and discharging functions; the cyclic energy recovery buffer unit absorbs feedback energy from the load side through a supercapacitor array and recharges it back to the battery pack; the main control unit dynamically adjusts the charging and discharging strategy based on multi-parameter acquisition using a fuzzy PID algorithm, and achieves smooth switching between multiple modes. This invention also discloses a corresponding intelligent charging and discharging control method. This invention integrates charging, discharging, energy recovery, and battery management into one system, improving energy utilization efficiency, extending battery life, and possessing advantages such as high integration, high control precision, and good safety.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery management technology, specifically relating to an integrated intelligent charging and discharging control system for cyclic charging lithium batteries. Background Technology

[0002] With the rapid development of new energy technologies, lithium batteries are widely used as energy storage units in electric vehicles, energy storage power stations, portable electronic devices, and other fields. The charge and discharge control of lithium batteries directly affects their lifespan, safety, and energy utilization efficiency.

[0003] In existing technologies, lithium battery charging and discharging systems are typically two independent devices. The charging system is responsible for converting external power into charging parameters acceptable to the battery, while the discharging system is responsible for converting battery energy into power parameters required by the load. This separate design has the following drawbacks:

[0004] 1. High hardware redundancy; two independent power conversion circuits increase system size, weight, and cost.

[0005] 2. Low energy conversion efficiency; charging and discharging each involve independent conversion stages, resulting in significant cumulative losses.

[0006] 3. It is impossible to effectively recover the feedback energy during the discharge process, such as the feedback energy generated when electric vehicles brake or the excess energy generated when the load changes suddenly. This energy is usually dissipated through the energy-consuming resistor, resulting in energy waste.

[0007] 4. The charging and discharging control strategy is relatively fixed and it is difficult to dynamically adjust it according to parameters such as real-time battery status, ambient temperature, and battery health, which affects battery life.

[0008] 5. The protection mechanism is simple, mostly software-level overvoltage and overcurrent protection, with limited response speed, posing safety hazards under extreme operating conditions. Summary of the Invention

[0009] The purpose of this invention is to provide an integrated intelligent charging and discharging control system and method for cyclic charging lithium batteries, so as to solve the technical problems of hardware redundancy, energy waste, single control strategy and imperfect protection caused by the separate design of existing charging and discharging systems.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] An integrated intelligent charging and discharging control system for cyclic charging lithium batteries includes a main control unit, a bidirectional power conversion unit, a cyclic energy recovery buffer unit, a battery pack acquisition unit, a multi-dimensional sensing unit, an active balancing unit, a hierarchical protection unit, and a communication interaction unit.

[0012] The bidirectional power conversion unit is connected to the external power supply port, the load port, and the battery pack, respectively, and is used to realize time-division multiplexing switching between charging mode and discharging mode under the control of the main control unit.

[0013] The circulating energy recovery buffer unit is connected in parallel to the DC bus side of the bidirectional power conversion unit to absorb the feedback energy from the load side and then recharge it back to the battery pack after buffering.

[0014] The main control unit is electrically connected to the bidirectional power conversion unit, the cyclic energy recovery buffer unit, the battery pack acquisition unit, the multi-dimensional sensing unit, the active balancing unit, the graded protection unit, and the communication interaction unit, respectively. It is used to dynamically adjust the charging and discharging strategy and control the cyclic energy recovery process based on the acquired battery status parameters and operating condition parameters.

[0015] The entire system integrates power conversion, energy recovery, status acquisition, battery balancing, fault protection, and data interaction into a single hardware architecture. It eliminates the need for separate charging and discharging devices, reducing redundant power circuits and signal acquisition lines, minimizing overall system space, and reducing the number of supporting components. The bidirectional power conversion circuit shares a single main power loop to handle both energy flows, reducing energy loss from multiple conversions. A buffer structure added to the bus side can catch excess energy flowing backward during load operation, preventing it from being directly lost as heat. The recovered energy is then resupplyed to the battery, improving the overall energy utilization of the system. The main control unit uniformly receives all sensor signals and operational signals from each functional unit, synchronously coordinating all logics for charging, discharging, energy recovery, balancing, and protection. The actions of each functional link cooperate with each other, preventing conflicts caused by independent module operation. It can synchronously adjust the operating logic based on real-time battery status and changes in external load and power supply, allowing the entire system to adapt to different usage scenarios.

[0016] As a preferred embodiment of the present invention, the bidirectional power conversion unit includes a bidirectional DC-DC converter. The bidirectional DC-DC converter adopts a full-bridge or half-bridge topology, and its switching transistors operate in a frequency range of 10kHz to 200kHz. In charging mode, the bidirectional DC-DC converter operates in a buck state, converting the external input voltage to a charging voltage suitable for the battery pack. In discharging mode, it operates in a boost state, converting the battery pack voltage to a supply voltage suitable for the load. A mature symmetrical power topology is used to build the bidirectional power conversion path. The same set of power switching devices can transmit power bidirectionally, eliminating the need for separate buck charging and boost discharging circuits, further simplifying the number of power loop components. The adjustable switching operating range can adapt to the usage requirements of different power levels. A low switching operating range can reduce electromagnetic interference generated by switching operations, while a high switching operating range can reduce the size of the supporting magnetic and capacitor components. During charging, the external input voltage is automatically reduced to match the battery's tolerance standard, preventing direct high voltage from damaging the battery cells. During discharging, the battery output voltage is increased to match the load power supply requirements, eliminating the need for additional boost auxiliary equipment. A single converter can simultaneously meet the voltage conversion needs of both battery charging and load power supply, simplifying the system's peripheral circuitry.

[0017] As a preferred embodiment of the present invention, the cyclic energy recovery buffer unit includes a supercapacitor array, an auxiliary DC-DC converter, and an energy flow switching device. The rated capacity of the supercapacitor array ranges from 0.1F to 100F, and its withstand voltage range is 0.5 to 2 times the rated voltage of the battery pack. The auxiliary DC-DC converter is used to realize bidirectional energy transfer between the supercapacitor array and the DC bus, and its maximum output current range is 1A to 50A. Relying on the capacitor array to receive short-term high-power feedback energy, the capacitor-type energy storage component has a faster response speed and can instantly absorb the reverse energy generated by load changes, avoiding the impact of drastic fluctuations in bus voltage on power switching devices and battery cells. The withstand voltage range of the capacitor array covers the upper and lower ranges of the normal operating voltage of the battery, and it is compatible with battery packs of different series numbers, without the possibility of voltage over-limit damage to the capacitor array. An independent auxiliary conversion circuit is added to connect the capacitor array and the DC bus, which can smoothly control the speed at which the stored energy in the capacitor is transferred to the battery. This prevents a large current from directly rushing into the battery and causing increased cell polarization. The energy flow switching component can automatically switch the feedback energy storage path without the main controller continuously outputting control signals to maintain the energy storage state, reducing the main controller's computational load and realizing a complete process of first buffering the feedback energy and then smoothly recharging it, continuously reducing energy waste.

[0018] As a preferred embodiment of the present invention, the main control unit incorporates a multi-mode charging and discharging control strategy, including constant current charging mode, constant voltage charging mode, pulse charging mode, trickle charging mode, constant current discharging mode, and constant power discharging mode. The main control unit smoothly switches between modes based on the battery pack's state of charge, health status, temperature parameters, and load requirements, with a switching transition time ranging from 10ms to 500ms. Multiple operating logics are set to adapt to different battery charge stages and usage requirements. A single device can handle multiple operating scenarios, including rapid charging, full-charge voltage stabilization, mitigating cell polarization, maintaining long-term charge, stable current output, and stable power output, without requiring changes to the control program or external control modules to switch operating modes. The switching process features a smooth transition phase, preventing sudden changes in current or voltage during mode transitions, reducing damage to the active materials inside the cell from current surges, and avoiding drastic fluctuations in the load-side supply voltage that could affect the stable operation of the equipment. The system can automatically read the battery power, aging level, temperature environment and load power demand to automatically match the corresponding operating mode without manual switching. It is suitable for unattended continuous operation scenarios and takes into account both charging efficiency and long-term battery durability.

[0019] As a preferred embodiment of the present invention, the main control unit uses a fuzzy PID algorithm to dynamically adjust the charging and discharging current, with a current adjustment range from 0.05C to 3C. The input parameters of the fuzzy PID algorithm include the battery pack's state of charge deviation, the rate of change of state of charge deviation, and the temperature deviation. The output parameter is the adjustment amount of the charging and discharging current setpoint. Relying on multi-dimensional battery operating deviation data, the charging and discharging current is corrected in real time, without relying on fixed current parameters. This allows it to adapt to the performance changes of the battery throughout its entire lifecycle, from new to aged, and to different environmental conditions, including high and low temperatures. Conventional fixed-parameter control methods cannot adjust the output to follow the non-linear changes of the battery, easily resulting in slow charging speeds or excessive current damaging the battery cells. This solution adjusts the current through comprehensive judgment of multiple deviations. During the charging phase, it can increase the charging speed under safe conditions, and during the discharging phase, it can limit the output current based on the battery's tolerance, reducing the probability of internal side reactions within the battery cells and extending the overall battery life. The algorithm completes autonomous tuning based on basic deviation data, eliminating the need to pre-enter a large number of calibration parameters for different battery models, thus reducing the workload of initial equipment debugging.

[0020] As a preferred embodiment of the present invention, the active balancing unit includes multiple active balancing converters, each corresponding to one individual battery cell, with a balancing current range of 50mA to 5A. The active balancing unit works in conjunction with passive balancing resistors. Active balancing is initiated when the voltage difference between individual cells exceeds a first threshold, passive balancing is initiated when the voltage difference is less than a second threshold but greater than a third threshold, and balancing stops when the voltage difference is less than the third threshold. The first threshold ranges from 50mV to 200mV, the second threshold ranges from 10mV to 50mV, and the third threshold ranges from 1mV to 10mV. Each cell is equipped with a separate balancing conversion path, which can directly transfer the internal energy of the high-capacity cell to the low-capacity cell, avoiding the consumption of excess energy by simply relying on resistors, and reducing the heat and energy loss generated during the balancing process. Combined with resistive passive balancing, a layered balancing logic is formed. When the cell voltage difference is large, energy transfer is used to quickly reduce the voltage difference, shortening the balancing time. When the cell voltage difference is reduced to a small range, resistive balancing is switched to reduce hardware operating power consumption. Once the voltage difference is close to uniform, the balancing action is directly stopped, avoiding meaningless continuous balancing that wastes energy. The layered balancing logic takes into account both balancing speed and overall energy consumption, continuously reducing the power difference between series-connected cells, preventing some cells from being overcharged or over-discharged in advance, improving the synchronous charging and discharging capability of the entire battery pack, and slowing down the rate of capacity decay of the entire battery pack.

[0021] As a preferred embodiment of the present invention, the hierarchical protection unit includes a first-level hardware protection, a second-level firmware protection, and a third-level software protection. The first-level hardware protection consists of an analog comparator and a protection execution device, with a response time ranging from 1μs to 100μs, and is used for rapid protection against overvoltage, undervoltage, overcurrent, and short circuit. The second-level firmware protection is implemented by the interrupt service routine of the main control unit, with a response time ranging from 100μs to 10ms, and is used for protection against abnormal temperature and communication. The third-level software protection is implemented by the main loop program of the main control unit, with a response time ranging from 10ms to 1s, and is used for predictive protection of health status and lifespan management. A three-layer progressive fault protection system is established, with different levels of protection structures operating independently and without dependence on each other. Extreme short circuits, overcurrents, and other dangerous faults can be directly cut off from the power circuit through a pure hardware structure without waiting for the main control unit to calculate and judge, shortening the fault handling time and avoiding the risk of cell thermal runaway. Moderate temperature anomalies and signal transmission faults rely on the main control interrupt program for rapid response, timely execution of current limiting and power reduction operations, taking into account both the continuous operation capability of the equipment and battery safety. Long-term, slow aging issues are addressed through continuous monitoring and prediction by the main cycle program, which adjusts the upper limit of charging and discharging power in advance to prevent the battery from operating beyond its lifespan limit. Multiple layers of protection form a complete safety barrier; even if one protection layer fails, the others can still function normally, significantly improving the overall equipment's fault tolerance. Differentiating the severity of faults and matching appropriate handling methods prevents minor faults from causing immediate shutdowns and disrupting continuous operation.

[0022] As a preferred embodiment of the present invention, the main control unit incorporates an online battery health status estimation module. This module uses a combination of an equivalent circuit model and an extended Kalman filter algorithm to estimate the battery's internal resistance and capacity decay. The online health status estimation module periodically collects voltage, current, and temperature data during charging and discharging, with an estimation cycle ranging from 1 minute to 60 minutes and an estimation error range of ±2% to ±8%. During equipment operation, real-time operating data is continuously collected to autonomously determine the battery's aging level. This eliminates the need for separate battery disassembly and offline testing with dedicated equipment, allowing for status assessment without interrupting normal charging and discharging operations. The system combines the battery's equivalent electrical model with filtering algorithms to process the collected signals, filtering out data fluctuations caused by environmental interference during the collection process, reducing aging level judgment bias, and accurately capturing aging characteristics such as increased cell internal resistance and decreased usable capacity. Based on periodically updated aging data, the system synchronously adjusts the charging and discharging limit parameters. As aging progresses, the upper limit of the charging and discharging current is automatically reduced to minimize the impact of high current on aging cells, predicting in advance when the battery is nearing its end-of-life. This facilitates timely battery replacement by maintenance personnel, preventing equipment downtime due to sudden battery failure.

[0023] As a preferred embodiment of the present invention, the multi-dimensional sensing unit includes a voltage acquisition channel, a current acquisition channel, a temperature acquisition channel, and an internal resistance detection channel. The voltage acquisition channel has an acquisition accuracy range of ±0.5mV to ±5mV and an acquisition period range of 1ms to 100ms. The current acquisition channel uses a Hall sensor or a shunt, with an acquisition accuracy range of ±0.1% to ±1%FS. The temperature acquisition channel uses an NTC thermistor or thermocouple, with a temperature measurement range of -40℃ to 125℃ and an accuracy range of ±0.5℃ to ±2℃. It simultaneously acquires four key operating parameters: cell voltage, circuit current, cell temperature, and cell internal resistance, comprehensively covering all operating indicators affecting battery safety and lifespan, preventing deviations in control logic judgments due to missing acquisition of a single parameter. Each acquisition path is equipped with fine acquisition resolution capabilities, capable of capturing subtle changes in voltage, current, and temperature, facilitating early identification of slowly developing abnormal operating conditions by the main controller. The acquisition period can be flexibly adjusted; a high-speed acquisition mode adapts to high-power, drastic fluctuation conditions, while a low-speed acquisition mode reduces the data processing load on the main controller. Two types of current acquisition elements can be flexibly selected according to the power of the equipment, and the temperature sensing element is suitable for various high and low temperature operating environments. The entire sensing structure has stronger versatility, and the accurate data collected provides reliable data support for all logics of main control mode switching, current adjustment, balanced start-up, and hierarchical protection, ensuring accurate judgment of the entire control logic.

[0024] This invention also provides an integrated intelligent charging and discharging control method for a cyclic-chargeable lithium battery, comprising the following steps:

[0025] S1. System initialization: Collect the voltage, total voltage, total current, and temperature parameters of each cell in the battery pack, and calculate the initial state of charge and health status.

[0026] S2. Determine the current working mode: If an external power source is detected and the battery pack needs to be charged, enter the charging mode; if a load is detected and the battery pack needs to be discharged, enter the discharging mode; if energy feedback is detected from the load side, enter the cyclic energy recovery mode.

[0027] S3. In charging mode, dynamically select the charging sub-mode and adjust the charging current according to the state of charge, temperature and health status.

[0028] S4. In discharge mode, the discharge output is dynamically adjusted according to load demand, temperature and health status.

[0029] S5. In the cycle energy recovery mode, the feedback energy is first stored in the supercapacitor array. After the supercapacitor voltage reaches the set threshold, it is recharged to the battery pack through the auxiliary DC-DC converter.

[0030] S6. Real-time monitoring of various protection parameters triggers a graded protection mechanism;

[0031] S7. Regularly update the battery health status estimation results and correct the charging and discharging strategy parameters.

[0032] The above-described operational process forms a complete closed loop, from device power-on self-test to continuous operation, fault protection, and parameter adaptive correction. During power-on, all basic data acquisition and initial state determination are completed in one go, eliminating the need for manual input of battery parameters and simplifying the startup process. The system can autonomously identify three operating conditions: external power supply, load, and regenerative energy, and automatically switch the corresponding operational process. In scenarios with alternating operating conditions, no manual intervention is required to switch the working logic, adapting to the frequent switching of charging and discharging conditions in mobile devices and uninterrupted energy storage devices. The charging, discharging, and energy recovery processes all synchronously adjust output parameters based on battery charge, temperature, and aging status, balancing efficiency and battery protection throughout. The regenerative energy recovery process, with its step-by-step buffering and smooth recharging, avoids instantaneous high-current impacts on the battery cells. Fault indicators are continuously monitored throughout operation; upon anomalies, a layered protection process is immediately activated, while simultaneously updating battery aging data to reverse-correct the entire control logic. This allows the control process to autonomously adapt to battery aging, eliminating the need for manual recalibration of control parameters and reducing subsequent maintenance costs.

[0033] In the aforementioned integrated cyclic charging lithium battery intelligent charge and discharge control method, the cyclic energy recovery mode in step S5 specifically includes:

[0034] S51. Detect whether the DC bus voltage is higher than the feedback threshold. If so, turn on the energy flow switching device so that the feedback energy flows into the supercapacitor array.

[0035] S52. Monitor the voltage of the supercapacitor array. When the voltage reaches the upper limit threshold, stop direct charging and start the auxiliary DC-DC converter for constant current recharge.

[0036] S53. When the voltage of the supercapacitor array drops to the lower threshold, stop the auxiliary DC-DC converter and wait for the next energy feedback input.

[0037] The feedback threshold range is 1.05 to 1.2 times the rated voltage of the DC bus, the upper threshold range is 0.8 to 0.95 times the rated voltage of the supercapacitor, and the lower threshold range is 0.2 to 0.5 times the rated voltage of the supercapacitor.

[0038] Relying on changes in bus voltage as the basis for identifying feedback energy, this system eliminates the need for additional independent energy detection sensors to identify reverse energy, simplifying sensor placement. Upon a rise in bus voltage, the energy storage path is immediately activated, rapidly absorbing instantaneous feedback energy, stabilizing the bus operating voltage, and preventing voltage spikes that could damage power devices. Once the capacitor's stored charge reaches its safe upper limit, direct energy storage ceases, and the conversion circuit intervenes to uniformly deliver energy to the battery, controlling the recharge current smoothly and preventing a large current surge into the battery after the capacitor is fully charged, thus mitigating battery charging polarization. Once the capacitor's internal energy is released to its safe lower limit, the conversion circuit stops operating, preventing deep discharge of the capacitor and shortening its lifespan. The entire energy recovery process is executed automatically and cyclically, continuously capturing intermittent feedback energy, maximizing the recovery of excess energy from the load side, and continuously reducing the overall system energy consumption.

[0039] In the above-mentioned integrated cyclic charging lithium battery intelligent charge and discharge control method, the charging sub-mode switching condition in step S3 is:

[0040] When the state of charge is below the first SOC threshold and the temperature is within a suitable range, constant current high current charging is used, with the current range being 0.5C to 2C.

[0041] When the state of charge is higher than the first SOC threshold and lower than the second SOC threshold, a pulse charging mode is adopted, with a pulse duty cycle ranging from 10% to 90%.

[0042] When the state of charge is higher than the second SOC threshold and lower than the third SOC threshold, it switches to constant voltage charging mode.

[0043] When the state of charge is higher than the third SOC threshold, it switches to trickle charging mode with a current range of 0.05C to 0.2C.

[0044] The first SOC threshold ranges from 50% to 80%, the second SOC threshold ranges from 80% to 90%, and the third SOC threshold ranges from 90% to 95%.

[0045] The charging operation mode is matched in stages according to the battery's charge level. When the charge level is low, a stable high current is used to quickly replenish the energy, shortening the overall charging time and meeting the demand for rapid power consumption. When the charge level rises to the middle range, pulse charging is switched. The intermittent current supply can release the polarization voltage generated during the charging process of the cell, improve the battery's charging acceptance capacity, store more energy in the same amount of time, and reduce cell heat generation. When the charge level is close to full, constant voltage charging is switched, and the charging current is gradually reduced to avoid overcharging damage caused by the cell voltage exceeding the limit. After the charge level reaches the full range, a small current is used to replenish the cell's self-discharge loss, maintaining the battery at full charge in long-term static scenarios without frequently starting the high-power charging circuit. The segmented switching logic is entirely triggered autonomously by the battery's own charge level, taking into account charging speed, charging safety, and long-term storage durability, and is suitable for use scenarios such as energy storage and vehicle use where the battery needs to be quickly replenished after long periods of static storage.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] (1) Integrated design: Through the time-division multiplexing architecture of the bidirectional power conversion unit, the charging and discharging functions are integrated into the same power circuit, which reduces hardware redundancy, reduces system size, weight and cost, and improves power density.

[0048] (2) Recycled energy recovery: A recycled energy recovery buffer unit is added, which uses a supercapacitor array to absorb the feedback energy from the load side and then charges it back to the battery pack through an auxiliary DC-DC converter, thus avoiding the dissipation and waste of feedback energy and improving the overall energy utilization efficiency.

[0049] (3) Intelligent multi-mode control: The main control unit has multiple charging and discharging modes built in, which are dynamically switched based on multiple parameters such as state of charge, health status, and temperature. The fuzzy PID algorithm is used to adjust the current in real time, taking into account both charging speed and battery life.

[0050] (4) Hierarchical protection mechanism: A three-level protection system of hardware, firmware and software is constructed to deal with fault scenarios with different response speed requirements, which significantly improves the security and reliability of the system.

[0051] (5) Active balancing and health management: Combining a hybrid balancing strategy of active balancing and passive balancing, and with online health status estimation, it effectively improves battery pack consistency and extends the overall service life of the battery pack. Attached Figure Description

[0052] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only examples of embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 This is a structural block diagram of an embodiment of the present invention;

[0054] Figure 2 This is a schematic diagram of the circuit topology of the bidirectional power conversion unit in an embodiment of the present invention;

[0055] Figure 3 This is a schematic diagram of the structure of the cyclic energy recovery buffer unit in an embodiment of the present invention;

[0056] Figure 4 This is a flowchart of an embodiment of the present invention. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0058] See Figure 1 As shown in the figure, the integrated intelligent charging and discharging control system for cyclic charging lithium batteries disclosed in this embodiment of the invention includes a main control unit, a bidirectional power conversion unit, a cyclic energy recovery buffer unit, a battery pack acquisition unit, a multi-dimensional sensing unit, an active balancing unit, a hierarchical protection unit, and a communication interaction unit.

[0059] The bidirectional power conversion unit is connected to the external power supply port, the load port, and the battery pack, respectively, serving as the main power circuit of the system. Under the control of the main control unit, it realizes time-division multiplexing switching between charging and discharging modes. The cyclic energy recovery buffer unit is connected in parallel to the DC bus side of the bidirectional power conversion unit to absorb the feedback energy from the load side and buffer it before recharging it back to the battery pack.

[0060] The main control unit, as the control core of the system, is electrically connected to the bidirectional power conversion unit, the cycle energy recovery buffer unit, the battery pack acquisition unit, the multi-dimensional sensing unit, the active balancing unit, the hierarchical protection unit, and the communication interaction unit. It receives data collected by each unit, outputs control commands, dynamically adjusts the charging and discharging strategy, and controls the cycle energy recovery process.

[0061] Specifically, the main control unit can be implemented using a microcontroller or digital signal processor, such as an ARM series MCU or a TI series DSP, which has sufficient computing power to execute fuzzy PID algorithm, extended Kalman filter algorithm, and multi-mode switching logic.

[0062] like Figure 2 As shown, the bidirectional power conversion unit includes a bidirectional DC-DC converter. In this embodiment, a full-bridge topology is adopted, comprising four power switching transistors, an energy storage inductor, and input / output filter capacitors. The switching transistors can be MOSFETs or IGBTs, with an operating frequency range of 10kHz to 200kHz. The specific frequency can be selected according to the power level and efficiency requirements.

[0063] The bidirectional DC-DC converter has bidirectional energy flow capability: in charging mode, the diagonal switches are alternately turned on, and the circuit operates in buck mode, converting the higher external input voltage into a charging voltage suitable for the battery pack to charge the battery pack; in discharging mode, the other set of diagonal switches are alternately turned on, and the circuit operates in boost mode, converting the battery pack voltage into a supply voltage suitable for the load to supply power to the load.

[0064] By using the same full-bridge circuit to achieve time-division multiplexing of charging and discharging, separate charging and discharging converters are eliminated, reducing the number of power devices and improving system integration and power density.

[0065] like Figure 3 As shown, the circulating energy recovery buffer unit includes a supercapacitor array, an auxiliary DC-DC converter, and an energy flow switching device.

[0066] A supercapacitor array consists of multiple supercapacitor cells connected in series and parallel, with a rated capacity ranging from 0.1F to 100F and a withstand voltage range of 0.5 to 2 times the rated voltage of the battery pack. Supercapacitors are characterized by high power density, long cycle life, and fast charge and discharge speeds, making them suitable for absorbing short-term, high-power feedback energy.

[0067] The auxiliary DC-DC converter is used to realize bidirectional energy transfer between the supercapacitor array and the DC bus. Its maximum output current range is 1A to 50A, and it can adopt a buck-boost topology to adapt to the wide voltage variation range of the supercapacitor.

[0068] The energy flow switching device can be a power MOSFET or a diode to control the direction of the regenerative energy flow. When regenerative energy occurs on the load side (such as during motor braking or a sudden load drop), the DC bus voltage rises, the energy flow switching device turns on, and the regenerative energy directly charges the supercapacitor array, achieving rapid energy buffering and absorption. When the voltage of the supercapacitor array accumulates to a certain level, the auxiliary DC-DC converter is activated to recharge the energy in the supercapacitors back to the battery pack in a controlled manner, completing the cycle recovery.

[0069] The battery pack acquisition unit is used to acquire the voltage of each individual cell in the battery pack. It can use a dedicated battery management analog front-end chip and supports the acquisition of voltage of multiple cells connected in series.

[0070] The multi-dimensional sensing unit includes a voltage acquisition channel, a current acquisition channel, a temperature acquisition channel, and an internal resistance detection channel. The voltage acquisition channel has an acquisition accuracy range of ±0.5mV to ±5mV and an acquisition period range of 1ms to 100ms. The current acquisition channel uses a Hall sensor or a shunt, with an acquisition accuracy range of ±0.1% to ±1%FS. The temperature acquisition channel uses an NTC thermistor or thermocouple, with a temperature measurement range of -40℃ to 125℃ and an accuracy range of ±0.5℃ to ±2℃. The internal resistance detection channel can be implemented using AC injection or pulse discharge methods for online monitoring of battery internal resistance changes.

[0071] The active balancing unit includes multiple active balancing converters, each corresponding to one individual battery cell, with a balancing current range of 50mA to 5A. The active balancing unit works in conjunction with passive balancing resistors to form a hybrid balancing strategy: active balancing is initiated when the voltage difference between cells exceeds a first threshold (50mV to 200mV), transferring energy from the high-voltage cell to the low-voltage cell via energy transfer; passive balancing is initiated when the voltage difference is less than a second threshold (10mV to 50mV) but greater than a third threshold (1mV to 10mV), using resistors to draw the high-voltage cell down; balancing stops when the voltage difference falls below the third threshold. This hierarchical balancing strategy balances balancing speed and efficiency.

[0072] The tiered protection unit comprises level one hardware protection, level two firmware protection, and level three software protection, forming a defense-in-depth system.

[0073] The first-level hardware protection consists of an analog comparator and protection actuators (such as relays and MOSFETs), with a response time range of 1μs to 100μs. It can work independently without relying on the main control unit and is used for fault protection that requires extremely fast response, such as overvoltage, undervoltage, overcurrent, and short circuit.

[0074] The secondary firmware protection is implemented by the interrupt service routine of the main control unit, with a response time range of 100μs to 10ms, and is used for protection against medium-speed requirements such as abnormal temperature, communication, and data acquisition.

[0075] Level 3 software protection is implemented by the main loop program of the main control unit, with a response time range of 10ms to 1s. It is used for slow protection such as health status prediction protection, lifespan management, and strategic derating.

[0076] The main control unit incorporates an online battery health estimation module, which uses an equivalent circuit model combined with an extended Kalman filter algorithm to estimate battery internal resistance and capacity decay. The online health estimation module periodically collects voltage, current, and temperature data during charging and discharging, with an estimation period ranging from 1 minute to 60 minutes and an estimation error range of ±2% to ±8%. The health estimation results are used to adjust charging and discharging strategy parameters; for example, appropriately reducing the charging current when battery aging worsens to extend remaining lifespan.

[0077] The main control unit incorporates a multi-mode charging and discharging control strategy, including constant current charging mode, constant voltage charging mode, pulse charging mode, trickle charging mode, constant current discharging mode, and constant power discharging mode. Based on the battery pack's state of charge, state of health, temperature parameters, and load requirements, the main control unit smoothly switches between modes with a transition time ranging from 10ms to 500ms, avoiding sudden changes in current or voltage during switching.

[0078] The main control unit uses a fuzzy PID algorithm to dynamically adjust the charging and discharging current, with a current adjustment range from 0.05C to 3C. The input parameters of the fuzzy PID algorithm include the battery pack's state of charge deviation, the rate of change of state of charge deviation, and the temperature deviation. Through fuzzy inference, the proportional, integral, and derivative parameters of the PID are tuned online, and the adjustment amount of the charging and discharging current setpoint is output, realizing precise control of the nonlinear and time-varying battery system.

[0079] The communication interaction unit supports multiple communication methods such as CAN, RS485, Bluetooth, and WiFi for data interaction with the host computer, battery management system, and cloud platform. It also supports human-machine interface display of operating status, parameter settings, and other functions.

[0080] The following is combined Figure 4 The integrated intelligent charge and discharge control method for a cyclic-chargeable lithium battery of the present invention includes the following steps:

[0081] S1. System Initialization. After the system is powered on, the main control unit completes peripheral initialization and parameter loading. The battery pack acquisition unit and the multi-dimensional sensing unit acquire the voltage, total voltage, total current, and temperature parameters of each cell in the battery pack. The main control unit calculates the initial state of charge based on the ampere-hour integration method and the open-circuit voltage method, and loads historical health status data.

[0082] S2. Determine the current operating mode. The main control unit detects the external power supply connection status, load connection status, and DC bus voltage: If an external power supply is detected and the battery pack's state of charge is lower than the set charging start threshold, it enters charging mode; if a load is detected and the battery pack's state of charge is higher than the discharge cutoff threshold, it enters discharging mode; if a rise in DC bus voltage is detected, indicating load-side energy feedback, it enters cyclic energy recovery mode. These three modes can be dynamically switched according to operating conditions.

[0083] S3. Charging Mode Control. In charging mode, the main control unit dynamically selects the charging sub-mode and adjusts the charging current based on the state of charge, temperature, and health status. Specific switching conditions are as follows:

[0084] When the state of charge is below the first SOC threshold (50% to 80%) and the temperature is within a suitable range, constant current high-current charging is used, with a current range of 0.5C to 2C, to achieve fast charging;

[0085] When the state of charge is higher than the first SOC threshold and lower than the second SOC threshold (80% to 90%), a pulse charging mode is adopted with a pulse duty cycle ranging from 10% to 90%. The pulse gap is used to alleviate battery polarization and improve charging acceptance.

[0086] When the state of charge is higher than the second SOC threshold and lower than the third SOC threshold (90% to 95%), it switches to constant voltage charging mode to keep the charging voltage constant and the current gradually decreases.

[0087] When the state of charge is higher than the third SOC threshold, it switches to trickle charging mode with a current range of 0.05C to 0.2C to compensate for self-discharge losses and maintain a fully charged state.

[0088] S4. Discharge Mode Control. In discharge mode, the main control unit dynamically adjusts the discharge output based on load demand, temperature, and battery health. It supports two modes: constant current discharge and constant power discharge. Constant current discharge mode maintains a constant discharge current, suitable for loads requiring high current stability; constant power discharge mode maintains a constant output power, suitable for loads requiring stable power. When the battery temperature is too low or too high, it automatically derated to protect battery safety.

[0089] S5. Cyclic Energy Recovery Mode Control. In cyclic energy recovery mode, the recovered energy is first stored in the supercapacitor array. Once the supercapacitor voltage reaches a set threshold, it is recharged back to the battery pack via an auxiliary DC-DC converter. Specifically, this includes:

[0090] S51. Detect whether the DC bus voltage is higher than the feedback threshold (1.05 to 1.2 times the rated DC bus voltage). If so, turn on the energy flow switching device to allow the feedback energy to flow into the supercapacitor array and use the high power density characteristics of the supercapacitor to quickly absorb the feedback energy.

[0091] S52. Monitor the voltage of the supercapacitor array. When the voltage reaches the upper limit threshold (0.8 to 0.95 times the rated voltage of the supercapacitor), stop direct charging and start the auxiliary DC-DC converter to perform constant current recharge, so that the energy in the supercapacitor can be smoothly charged into the battery pack, avoiding the direct impact of large current on the battery.

[0092] S53. When the voltage of the supercapacitor array drops to the lower threshold (0.2 to 0.5 times the rated voltage of the supercapacitor), stop the auxiliary DC-DC converter and wait for the next feedback energy input.

[0093] S6. Real-time Protection Monitoring. During system operation, the hierarchical protection units monitor various protection parameters in real time. Level 1 hardware protection operates independently and immediately cuts off the power circuit once serious faults such as overvoltage, undervoltage, overcurrent, or short circuit are detected. Level 2 firmware protection responds to faults such as abnormal temperature and communication through interrupts, and performs current limiting or shutdown operations. Level 3 software protection performs predictive protection and strategic derating based on health status estimation and lifetime models.

[0094] S7. Health Status Update. The main control unit periodically updates the battery health status estimation results. Based on the voltage, current, and temperature data collected during charging and discharging, combined with the equivalent circuit model and extended Kalman filter algorithm, it estimates the degree of battery internal resistance growth and capacity decay, and corrects the charging and discharging strategy parameters according to the health status results, such as adjusting the charging current rate and modifying the SOC threshold, to achieve adaptive lifespan management.

[0095] The above steps are executed cyclically to achieve integrated intelligent control and cyclic energy recovery of the lithium battery charging and discharging process.

[0096] This invention integrates charging and discharging functions through time-division multiplexing of a bidirectional power conversion unit, eliminating the need for a separate charge-discharge converter. By adding a cyclic energy recovery buffer unit, the energy feedback from the load side is buffered to the supercapacitor before being recharged back to the battery, improving energy utilization. Through multi-mode charging and discharging strategies and fuzzy PID control, adaptive control for different operating conditions is achieved. Through three-level hierarchical protection and online health status estimation, the safety of the system and the battery life are improved.

[0097] The above description illustrates the basic principles of the present invention. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The above embodiments and descriptions in the specification are only for illustrating the principles of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and scope of the present invention without departing from the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. An integrated intelligent charging and discharging control system for cyclic-chargeable lithium batteries, characterized in that: It includes a main control unit, a bidirectional power conversion unit, a cyclic energy recovery buffer unit, a battery pack acquisition unit, a multi-dimensional sensing unit, an active balancing unit, a graded protection unit, and a communication interaction unit; The bidirectional power conversion unit is connected to the external power supply port, the load port and the battery pack respectively, and is used to realize time-division multiplexing switching of charging mode and discharging mode under the control of the main control unit. The circulating energy recovery buffer unit is connected in parallel to the DC bus side of the bidirectional power conversion unit, and is used to absorb the feedback energy from the load side and buffer it before recharging it back to the battery pack. The main control unit is electrically connected to the bidirectional power conversion unit, the cyclic energy recovery buffer unit, the battery pack acquisition unit, the multi-dimensional sensing unit, the active balancing unit, the hierarchical protection unit, and the communication interaction unit, respectively, and is used to dynamically adjust the charging and discharging strategy and control the cyclic energy recovery process based on the acquired battery state parameters and operating condition parameters.

2. The integrated intelligent charging and discharging control system for cyclic-chargeable lithium batteries according to claim 1, characterized in that: The bidirectional power conversion unit includes a bidirectional DC-DC converter, which adopts a full-bridge or half-bridge topology and its switching transistors operate in the frequency range of 10kHz to 200kHz. The bidirectional DC-DC converter operates in buck mode during charging, converting the external input voltage into a charging voltage suitable for the battery pack; and operates in boost mode during discharging, converting the battery pack voltage into a supply voltage suitable for the load.

3. The integrated intelligent charging and discharging control system for cyclic-chargeable lithium batteries according to claim 1, characterized in that: The circulating energy recovery buffer unit includes a supercapacitor array, an auxiliary DC-DC converter, and an energy flow switching device. The rated capacity of the supercapacitor array ranges from 0.1F to 100F, and the withstand voltage ranges from 0.5 times to 2 times the rated voltage of the battery pack. The auxiliary DC-DC converter is used to realize bidirectional energy transfer between the supercapacitor array and the DC bus, and its maximum output current range is 1A to 50A.

4. The integrated intelligent charging and discharging control system for cyclic-chargeable lithium batteries according to claim 1, characterized in that: The main control unit has a built-in multi-mode charging and discharging control strategy, including constant current charging mode, constant voltage charging mode, pulse charging mode, trickle charging mode, constant current discharging mode and constant power discharging mode. The main control unit smoothly switches between modes based on the battery pack's state of charge, health status, temperature parameters, and load requirements, with a switching transition time ranging from 10ms to 500ms.

5. The integrated intelligent charging and discharging control system for cyclic-chargeable lithium batteries according to claim 1, characterized in that: The main control unit uses a fuzzy PID algorithm to dynamically adjust the charging and discharging current, with the current adjustment range being 0.05C to 3C. The input parameters of the fuzzy PID algorithm include the battery pack state of charge deviation, the rate of change of state of charge deviation, and the temperature deviation, and the output parameter is the adjustment amount of the charge and discharge current setpoint.

6. The integrated intelligent charging and discharging control system for cyclic-chargeable lithium batteries according to claim 1, characterized in that: The active balancing unit includes a multi-channel active balancing converter, each corresponding to a single cell, with a balancing current range of 50mA to 5A. The active balancing unit works in conjunction with the passive balancing resistor. When the voltage difference between individual cells is greater than the first threshold, active balancing is initiated. When the voltage difference between individual cells is less than the second threshold but greater than the third threshold, passive balancing is initiated. When the voltage difference between individual cells is less than the third threshold, balancing is stopped. The first threshold range is 50mV to 200mV, the second threshold range is 10mV to 50mV, and the third threshold range is 1mV to 10mV.

7. The integrated intelligent charging and discharging control system for cyclic-chargeable lithium batteries according to claim 1, characterized in that: The hierarchical protection unit includes first-level hardware protection, second-level firmware protection, and third-level software protection. The primary hardware protection consists of an analog comparator and a protection actuator, with a response time range of 1μs to 100μs, and is used for ultra-fast protection against overvoltage, undervoltage, overcurrent, and short circuit. The secondary firmware protection is implemented by the interrupt service routine of the main control unit, with a response time range of 100μs to 10ms, and is used for protection against abnormal temperature and communication. The three-level software protection is implemented by the main loop program of the main control unit, with a response time range of 10ms to 1s, and is used for predictive protection of health status and lifespan management.

8. The integrated intelligent charging and discharging control system for cyclic-chargeable lithium batteries according to claim 1, characterized in that: The main control unit has a built-in online battery health status estimation module, which uses a combination of equivalent circuit model and extended Kalman filter algorithm to estimate battery internal resistance and capacity decay. The online health status estimation module periodically collects voltage, current, and temperature data during the charging and discharging process, with an estimation cycle ranging from 1 minute to 60 minutes and an estimation error range of ±2% to ±8%.

9. The integrated intelligent charging and discharging control system for cyclic-chargeable lithium batteries according to claim 1, characterized in that: The multi-dimensional sensing unit includes a voltage acquisition channel, a current acquisition channel, a temperature acquisition channel, and an internal resistance detection channel. The voltage acquisition channel has an acquisition accuracy range of ±0.5mV to ±5mV and an acquisition period range of 1ms to 100ms. The current acquisition channel uses a Hall sensor or a shunt, with an acquisition accuracy range of ±0.1% to ±1%FS; The temperature acquisition channel uses an NTC thermistor or thermocouple, with a temperature measurement range of -40℃ to 125℃ and an accuracy range of ±0.5℃ to ±2℃.

10. An integrated intelligent charging and discharging control method for a cyclic-chargeable lithium battery, characterized in that: The integrated intelligent charge and discharge control system for cyclic-chargeable lithium batteries according to any one of claims 1-9 includes the following steps: S1. System initialization: Collect the voltage, total voltage, total current, and temperature parameters of each cell in the battery pack, and calculate the initial state of charge and health status. S2. Determine the current working mode: If an external power source is detected and the battery pack needs to be charged, enter the charging mode; if a load is detected and the battery pack needs to be discharged, enter the discharging mode; if energy feedback is detected from the load side, enter the cyclic energy recovery mode. S3. In charging mode, dynamically select the charging sub-mode and adjust the charging current according to the state of charge, temperature and health status. S4. In discharge mode, the discharge output is dynamically adjusted according to load demand, temperature and health status. S5. In the cycle energy recovery mode, the feedback energy is first stored in the supercapacitor array. After the supercapacitor voltage reaches the set threshold, it is recharged to the battery pack through the auxiliary DC-DC converter. S6. Real-time monitoring of various protection parameters triggers a graded protection mechanism; S7. Regularly update the battery health status estimation results and correct the charging and discharging strategy parameters.

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