Lithium battery charging control system and method based on AC-DC-AC isolation transformation

Abstract

The invention discloses a lithium battery charging control system and method based on AC-DC-AC isolation transformation, and belongs to the technical field of battery charging and discharging control. The method comprises the following steps: inputting source intelligent identification and mode decision; the switching network reconstructs a charging path, and the system dynamically reconstructs a current path by controlling the action of a switch; the self-adaptive four-stage pulse charging control comprises the steps that an isolation transformer and an inverter module carry out a self-adaptive optimization charging stage according to the chemical characteristics of a lithium battery; and real-time dynamic safety protection: in the charging process, the system monitors the temperature of the transformer and other key components in real time, and if the temperature is abnormal, the system immediately adopts a load reduction strategy. Electrical isolation is achieved through AC-DC-AC conversion, an existing vehicle-mounted power device is fully utilized in the lithium battery charging process, and the power utilization rate is increased; through the intelligent adjustment of the control and monitoring module, the charging safety of the lithium battery is ensured, and the efficient operation of the system is also realized.

Description

Technical Field

[0001] This invention relates to the field of battery charging and discharging control technology, and in particular to a lithium battery charging control system and method based on AC-DC-AC isolation conversion. Background Technology

[0002] With the continuous development and iteration of new energy technologies, the charging control technology of vehicle lithium batteries has evolved from the initial basic constant current and constant voltage mode to real-time monitoring of voltage / temperature to achieve dynamic adjustment, and further optimized to the power electronics integration mode (such as reusing vehicle power devices), and has now achieved intelligent collaborative charging control in all scenarios.

[0003] However, during vehicle operation, power devices such as the motor controller, generator controller, and DC / DC converter are idle. To charge, an additional OBC circuit is typically required, increasing system complexity. Traditional isolated charging solutions usually require separate transformers and power modules, which not only increases system complexity but also impacts system efficiency.

[0004] Therefore, there is an urgent need to propose a lithium battery charging control system and method based on AC-DC-AC isolation conversion to solve the above problems. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a lithium battery charging control method based on AC-DC-AC isolation conversion, comprising the following steps:

[0006] Step 1: Intelligent identification and pattern decision of input source, including input feature analysis and security access verification;

[0007] Step 2: Switch network reconstructs charging path. In different charging modes, the system dynamically reconstructs the current path by controlling the switching action.

[0008] Step 3: Adaptive four-stage pulse charging control, including the isolation transformer and inverter module adaptively optimizing the charging stages according to the chemical characteristics of the lithium battery;

[0009] Step 4: Real-time dynamic safety protection: During the charging process, the system monitors the temperature of the transformer and other key components in real time. If an abnormal temperature is detected, the system will immediately take a load reduction strategy. At the same time, when a fault is detected, the system will immediately disconnect all switches and perform physical isolation through mechanical relays.

[0010] Step 5: Charging Completed and Reset: When the output AC power module monitors the battery SOC to reach 99% or the charging current drops below 0.05C, the system automatically determines that charging is complete and resets, disconnects all switches, and releases the capacitor voltage to a safe range through the AC-DC conversion module. At the same time, the control and monitoring module uploads the charging data to the cloud for recording and analysis.

[0011] The real-time dynamic security protection includes the following strategies:

[0012] Electrical isolation monitoring: This includes differential voltage sensors deployed on the primary and secondary sides, and differential voltage monitoring between the isolation transformer and the inverter module. If the voltage difference between the primary and secondary sides is detected to be greater than 5V, all switches will be disconnected immediately, and an insulation resistance test will be initiated.

[0013] Thermal runaway protection: This includes embedding temperature sensors in the isolation transformer and the inverter module transformer, establishing a temperature-current coupling model, and using the control and monitoring module to estimate the core temperature of the battery through a thermocouple model.

[0014] Voltage consistency control: If the detected single-cell voltage deviation is greater than 50mV, the control and monitoring module activates the balanced charging mode and switches the parallel discharge resistor to the high-voltage single cell.

[0015] Furthermore, the input feature analysis includes the control and monitoring module sampling the voltage waveform of the input terminal, i.e., the AC / DC compatible input module, in real time. When a 50 / 60Hz sine wave is detected, it is marked as AC input mode; when a stable DC with ripple <5% is detected, it is marked as DC input mode; if the feature cannot be identified within 30 seconds, the fault code "E01" is triggered.

[0016] The safety access verification includes the control and monitoring module detecting that the battery temperature is > 45℃, or the single cell voltage difference is > 0.3V, or the SOC is > 95%, triggering a safety lock to stop charging and sending an alarm signal to the control module.

[0017] Furthermore, the dynamic reconstruction of the current path by controlling the switch action includes:

[0018] In AC mode, the switching network completes the conversion of electrical energy and battery charging by multiplexing the PFC rectifier bridge arm of the motor controller and the high-frequency inverter of the generator controller, as well as the rectifier bridge arm of the motor controller.

[0019] When the input mode is AC input, close switch groups S2, S4, S5, S7, S8; disconnect switch groups S1, S3, S6; the power device multiplexing function is mapped as follows: motor controller bridge arm 1 is mapped to PFC rectification, generator controller H-bridge is mapped to high-frequency inverter, and motor controller bridge arms 2 / 3 are mapped to isolation rectification.

[0020] Furthermore, the dynamic reconstruction of the current path by controlling the switch action also includes:

[0021] In DC mode, the system achieves a direct path to the DC bus by multiplexing the DC / DC converter, while maintaining a path similar to that in AC mode.

[0022] When the input mode is DC input, close switch groups S2, S4, S5, S6, and S8; disconnect switch groups S1, S3, and S7; the power device multiplexing function is mapped as follows: the generator controller H-bridge is mapped to high-frequency inverter, and the motor controller full-bridge is mapped to isolation rectification.

[0023] Furthermore, the switching network reconfiguration charging path also includes load balancing protection:

[0024] The temperature of the multiplexed power devices is monitored in real time. When the temperature is > 85℃, the device switches to the standby bridge arm and reduces the output current by 5%. The load balancing protection rotates the main bridge arm every 5 minutes to extend the device life.

[0025] Furthermore, the adaptive optimization charging phase specifically includes:

[0026] During the pre-charge phase, when the SOC is less than 5%, the battery is woken up with a small current of 0.1C, and the output voltage of the isolation transformer is controlled.

[0027] During the constant current fast charging phase (5% ≤ SOC < 80%), the current is set to 1C. The battery temperature is monitored in real time during charging, and the charging current is adjusted according to the temperature rise. At the same time, the PWM duty cycle of the generator controller H-bridge is adjusted.

[0028] During the pulse charging phase (80% ≤ SOC < 95%), charging is performed using a precise 200Hz pulse current. By utilizing the fast shutdown characteristics of the motor controller, precise pulse control without the need for additional hardware is achieved.

[0029] During the constant voltage trickle charging stage, when the SOC is greater than 95%, trickle charging is performed in constant voltage mode when the battery is close to full charge.

[0030] Among them, the output AC power module outputs voltage during the constant voltage trickle charge stage, and the control and monitoring module decides on the switching of the charging stage and pulse timing control.

[0031] The present invention also provides a lithium battery charging control system based on AC-DC-AC isolation conversion, which executes the lithium battery charging control method based on AC-DC-AC isolation conversion as described above, including an AC / DC compatible input module, an AC-DC conversion module, an isolation transformer and inverter module, a control and monitoring module, and an output AC power supply module;

[0032] The AC / DC compatible input module provides the system with electrical energy through the input voltage and connects to the AC-DC conversion module to convert AC power to DC power. The DC output of the AC-DC conversion module is connected to the isolation transformer and inverter module, which converts DC power back to AC power and outputs it to charge the lithium battery. The control and monitoring module is interconnected with each other. The output AC power module is connected to the battery to provide the final charging power for the lithium battery.

[0033] The AC / DC compatible input module is configured to provide AC / DC power input to the charging system, which typically comes from the vehicle generator or grid power / DC charging pile input.

[0034] The AC-DC converter module is configured to convert the input AC power into stable DC power for subsequent charging.

[0035] The isolation transformer and inverter module are configured to achieve electrical isolation and inverter functions to charge the lithium battery;

[0036] Among them, the isolation transformer provides electrical isolation for the lithium battery charging process, preventing direct electrical connection between the lithium battery and the power grid or vehicle generator; the inverter converts DC power to AC power and regulates the output voltage and current.

[0037] The output AC power module is configured to invert the converted DC power into AC power with a suitable frequency and voltage to charge the lithium battery.

[0038] The control and monitoring module is configured to perform intelligent control and real-time monitoring of the entire charging system, including real-time monitoring of the charging status of the lithium battery, the operating status of the power devices, and the input and output voltage and current.

[0039] Monitoring the charging status of lithium batteries includes real-time monitoring of the charging status of lithium batteries through battery voltage, current and temperature sensors to ensure that the charging process of lithium batteries is within a safe range.

[0040] Monitoring the operating status of power devices includes real-time monitoring of the motor controller and generator controller to ensure full operation during charging.

[0041] The control and monitoring module also includes functions for optimizing the charging process.

[0042] Based on the battery charging curve, the output current and voltage are automatically adjusted to ensure that the lithium battery charging curve always meets the lithium battery charging requirements; it also includes intelligent control: the control module automatically adjusts the working status of the inverter and AC-DC conversion module based on real-time data, optimizes the load of power devices, and realizes the reuse of power devices.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] This invention achieves electrical isolation through AC-DC-AC conversion and fully utilizes existing onboard power devices during lithium battery charging to improve power utilization. Intelligent adjustment by the control and monitoring module not only ensures lithium battery charging safety but also achieves efficient system operation. The coordinated operation between modules guarantees both safety and efficiency in the charging process, while also solving problems such as large size, idle power devices, and insufficient electrical isolation found in traditional charging systems.

[0045] This invention reduces power device requirements by 60% compared to traditional hardware reuse schemes by multiplexing 3 sets of power devices (2 sets of motor controllers + 1 set of generator controllers) in AC mode and 2 sets of power devices (eliminating the front-end rectification) in DC mode.

[0046] This invention provides triple safety protection through active differential monitoring and dynamically adjusted electrical isolation, thermal management using an exponential decay current model, and a fault response speed of 10μs-level disconnection, further ensuring the charging safety performance of lithium batteries. Attached Figure Description

[0047] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 This is a schematic diagram of the lithium battery charging control system based on AC-DC-AC isolation conversion of the present invention;

[0050] Figure 2 This is a flowchart of the lithium battery charging control method based on AC-DC-AC isolation conversion of the present invention;

[0051] Figure 3 This is a flowchart of step 2 of the lithium battery charging control method based on AC-DC-AC isolation transformation of the present invention;

[0052] Figure 4 This is a flowchart of step 4 of the lithium battery charging control method based on AC-DC-AC isolation transformation of the present invention. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0054] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0055] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" and "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0056] Example 1

[0057] like Figure 1 As shown, this invention provides a lithium battery charging control system based on AC-DC-AC isolation conversion. The system adopts an AC-DC-AC conversion-based architecture and mainly consists of the following core modules:

[0058] An AC / DC compatible input module is configured to provide AC or DC power input to the charging system, typically from an onboard alternator or grid power / DC charging station. The AC / DC compatible input module provides the necessary electrical energy to the system, serving as its power input. Its output voltage and current are converted to DC power by an AC-DC converter module for subsequent use.

[0059] The AC-DC converter module is configured to convert the input AC power into stable DC power for subsequent charging. It converts the input AC power into DC power through circuits such as rectifiers and filters, providing a stable, fluctuation-free DC power supply for the subsequent battery charging process and ensuring the efficiency of the entire system.

[0060] An isolation transformer and inverter module are configured to provide electrical isolation and inversion functions for charging lithium batteries. The isolation transformer provides electrical isolation during the lithium battery charging process, preventing direct electrical connection between the lithium battery and the power grid or vehicle alternator, thereby improving charging safety. The inverter converts direct current (DC) to alternating current (AC), regulating the output voltage and current to suit the characteristics of lithium battery charging, ensuring the battery is not overcharged or damaged during charging. In the system design, this isolation transformer and inverter module are required to have high conversion efficiency, capable of AC-DC and DC-AC conversion with minimal energy loss; simultaneously, it must ensure electrical isolation between the battery and the external power source, thus preventing the battery from being affected by electrical faults or excessive voltage.

[0061] The control and monitoring module is configured to intelligently control and monitor the entire charging system in real time. It monitors the charging status of the lithium battery, the operating status of power devices, and the input and output voltage and current to ensure a safe and stable charging process. Battery status monitoring includes real-time monitoring of the lithium battery's charging status using sensors such as battery voltage, current, and temperature to ensure the charging process does not exceed safe limits. Power device status monitoring includes real-time monitoring of the operating status of power devices such as the motor controller and generator controller to ensure they are fully engaged in operation during charging, rather than idle.

[0062] The control and monitoring module also includes charging process optimization: based on the battery charging curve, it automatically adjusts the output current and voltage to ensure that the lithium battery charging curve always meets the lithium battery charging requirements, improving charging efficiency and safety. It also includes intelligent control: the control module can automatically adjust the operating status of the inverter and AC-DC conversion module based on real-time data, optimize the load of power devices, realize power device reuse, and improve overall system efficiency.

[0063] The output AC power module is configured to invert the converted DC power into AC power of appropriate frequency and voltage to charge the lithium battery. In other words, it outputs the AC-DC-AC converted power to charge the lithium battery. According to the control module's adjustment, the output AC power module delivers the inverter's output AC current to the battery at an appropriate frequency and voltage. This provides a suitable AC power supply for charging the lithium battery, ensuring that the lithium battery is not affected by improper voltage or current during the charging process.

[0064] The AC / DC compatible input module provides the system with electrical energy through the input voltage and connects to the AC-DC converter module to convert AC power to DC power. The DC output of the AC-DC converter module is connected to the inverter module via an isolation transformer, which further converts the DC power back to AC power for charging the lithium battery. The control and monitoring module is interconnected with all other modules. It monitors the charging status of the lithium battery, the system's electrical parameters, and the usage of power devices in real time, and adjusts the system's operating state through feedback to ensure the safety and efficiency of the charging process. The output AC power module connects to the battery, providing the final charging power for the lithium battery. The output current and voltage of this module are regulated by the control and monitoring module to ensure that the charging current meets the charging requirements of the lithium battery.

[0065] This invention achieves electrical isolation through AC-DC-AC conversion and fully utilizes existing onboard power devices during lithium battery charging to improve power utilization. Intelligent adjustment by the control and monitoring module not only ensures lithium battery charging safety but also achieves efficient system operation. The coordinated operation between modules guarantees both safety and efficiency in the charging process, while also solving problems such as large size, idle power devices, and insufficient electrical isolation found in traditional charging systems.

[0066] Example 2

[0067] like Figure 2 As shown, the present invention also provides a lithium battery charging control method based on AC-DC-AC isolation conversion, specifically including:

[0068] Step 1: Intelligent identification and pattern decision of input source, including input feature analysis and security access verification.

[0069] The input characteristic analysis includes real-time sampling of the voltage waveform at the input terminals (AC / DC compatible input modules) by the control and monitoring module. When a 50 / 60Hz sine wave is detected, it is marked as AC input mode; when a stable DC with ripple <5% is detected, it is marked as DC input mode. If the characteristic cannot be identified within 30 seconds, fault code "E01" is triggered.

[0070] The safety access verification process includes the control and monitoring module detecting that the battery temperature is >45℃, the single-cell voltage difference is >0.3V, or the SOC is >95%, triggering a safety lockout to stop charging and sending an alarm signal to the control module. If none of the above conditions are detected, the process proceeds to step 2, the power device reuse configuration process.

[0071] Step 2: Switch network reconstructs the charging path. In different charging modes, the system dynamically reconstructs the current path by controlling switch actions to achieve efficient energy transfer. For example... Figure 3 As shown, it includes:

[0072] In AC mode, the switching network completes power conversion and battery charging by multiplexing the PFC rectifier bridge arm of the motor controller, the high-frequency inverter of the generator controller, and the rectifier bridge arm of the motor controller. Specifically, when the input mode is AC input, switch groups S2, S4, S5, S7, and S8 are closed; disconnect switch groups S1, S3, and S6 are opened. The power device multiplexing function mapping is as follows: motor controller bridge arm 1 is mapped to PFC rectification, generator controller H-bridge is mapped to high-frequency inverter, and motor controller bridge arms 2 / 3 are mapped to isolation rectification.

[0073] In DC mode, the system achieves a direct path to the DC bus by multiplexing the DC / DC converter, while maintaining a path similar to that in AC mode. Specifically, when the input mode is DC input, switch groups S2, S4, S5, S6, and S8 are closed; switch groups S1, S3, and S7 are opened. The power device multiplexing function is mapped as follows: the generator controller H-bridge is mapped to high-frequency inversion, and the motor controller full-bridge is mapped to isolation rectification.

[0074] The AC-DC conversion module acts as a PFC rectifier in AC mode (i.e., multiplexed motor controller bridge arm 1); the isolation transformer and inverter module realize: high-frequency inverter function → multiplexed generator controller H bridge; and isolation rectification function → multiplexed motor controller bridge arm 2 / 3 (AC mode) or full bridge (DC mode).

[0075] The switching network reconfiguration of the charging path also includes load balancing protection: real-time monitoring of the temperature of the multiplexed power devices; when the temperature > 85°C, switching to the backup bridge arm (such as generator controller bridge arm 3) and reducing the output current by 5%. The load balancing protection rotates the primary bridge arm every 5 minutes to extend device lifespan.

[0076] Step 3: Adaptive four-stage pulse charging control, including the isolation transformer and inverter module adaptively optimizing the charging stages based on the chemical characteristics of the lithium battery, specifically including:

[0077] Precharge phase (SOC<5%): Wake up the battery with a small current of 0.1C and control the output voltage of the isolation transformer.

[0078] Constant current fast charging stage (5%≤SOC<80%): At this time, the current is set to 1C. The battery temperature is monitored in real time during the charging process. If the temperature rises too quickly, the charging current is reduced appropriately. At the same time, the PWM duty cycle of the generator controller H-bridge is adjusted.

[0079] During the pulse charging stage (80%≤SOC<95%), charging is performed using a precise 200Hz pulse current. By utilizing the fast shutdown characteristic of the motor controller, precise pulse control can be achieved without adding any hardware.

[0080] During the constant voltage trickle charging stage (SOC > 95%), when the battery is close to full charge, a constant voltage mode is used for trickle charging to ensure safe and accurate charging.

[0081] Among them, the output AC power module outputs voltage during the constant voltage trickle charge stage, and the control and monitoring module makes decisions on the switching of the charging stage (based on SOC) and pulse timing control.

[0082] Step 4: Real-time Dynamic Safety Protection: During charging, the system monitors the temperature of the transformer and other critical components in real time. If an abnormal temperature is detected, the system will immediately implement a load reduction strategy to minimize the risk of overheating. Simultaneously, upon detecting faults such as short circuits, the system (including the control and monitoring module) will disconnect all switches within 10μs and physically isolate the circuit via mechanical relays to ensure the safety of the battery and the system. Figure 4 As shown, for example, it includes the following processes:

[0083] 1. Electrical isolation monitoring: This includes differential voltage sensors deployed on the primary and secondary sides, and differential voltage monitoring between the isolation transformer and the inverter module. If the voltage difference between the primary and secondary sides is detected to be > 5V, all switches will be disconnected immediately, and an insulation resistance test will be initiated.

[0084] 2. Thermal runaway protection: This includes embedding temperature sensors in the isolation transformer and the inverter module transformer, establishing a temperature-current coupling model (such as an exponential decay current model), and the control and monitoring module estimating the core temperature of the battery through a thermocouple model.

[0085] 3. Voltage consistency control: If the detected single-cell voltage deviation is >50mV, the control and monitoring module activates the balanced charging mode and switches the parallel discharge resistor to the high-voltage single cell.

[0086] Step 5: Charging Completed and Reset: When the output AC power module monitors the battery SOC (State of Charge) to reach 99% or the charging current drops below 0.05C, the system automatically determines that charging is complete and resets, disconnects all switches, and releases the capacitor voltage to a safe range through the AC-DC conversion module (e.g., capacitor energy is discharged to <3V). Subsequently, the control and monitoring module uploads the charging data to the cloud for recording and analysis.

[0087] This invention reduces power device requirements by 60% compared to traditional hardware reuse schemes by multiplexing 3 sets of power devices (2 sets of motor controllers + 1 set of generator controllers) in AC mode and 2 sets of power devices (eliminating the front-end rectification) in DC mode.

[0088] This invention provides triple safety protection through active differential monitoring and dynamically adjusted electrical isolation, thermal management using an exponential decay current model, and a fault response speed of 10μs-level disconnection, further ensuring the charging safety performance of lithium batteries.

[0089] Example 3

[0090] The present invention also provides an electronic device, including: a processor, a transmitting device, an input device, an output device, and a memory. The processor may be implemented using a general-purpose CPU (Central Processing Unit), a microprocessor, an application-specific integrated circuit, or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of this application. The memory may be implemented using a read-only memory (ROM), a static storage device, a dynamic storage device, or a random access memory (RAM), and is used to store computer program code. The computer program code includes computer instructions. When the processor executes the computer instructions, the electronic device executes a method as described in any of the above possible implementation methods.

[0091] Example 4

[0092] The present invention also provides a computer-readable storage medium storing a computer program, the computer program including program instructions, which, when executed by a processor of an electronic device, cause the processor to perform a method as described in any of the above possible implementations.

[0093] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0094] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A lithium battery charging control method based on AC-DC-AC isolation conversion, characterized in that, Includes the following steps: Intelligent input source recognition and pattern decision-making, including input feature analysis and security access verification; The switching network reconstructs the charging path. In different charging modes, the system dynamically reconstructs the current path by controlling the switching action. Adaptive four-stage pulse charging control, including isolation transformer and inverter module adaptively optimizing charging stages according to the chemical characteristics of lithium battery; Real-time dynamic safety protection: During charging, the system monitors the temperature of the transformer and other key components in real time. If an abnormal temperature is detected, the system will immediately take a load reduction strategy. At the same time, when a fault is detected, the system will immediately disconnect all switches and perform physical isolation through mechanical relays. Charging completion and reset: When the output AC power module monitors the battery SOC to reach 99% or the charging current drops below 0.05C, the system automatically determines that charging is complete and resets, disconnects all switches, and releases the capacitor voltage to a safe range through the AC-DC conversion module. At the same time, the control and monitoring module uploads the charging data to the cloud for recording and analysis. The real-time dynamic security protection includes the following strategies: Electrical isolation monitoring: This includes differential voltage sensors deployed on the primary and secondary sides, and differential voltage monitoring between the isolation transformer and the inverter module. If the voltage difference between the primary and secondary sides is detected to be greater than 5V, all switches will be disconnected immediately, and an insulation resistance test will be initiated. Thermal runaway protection: This includes embedding temperature sensors in the isolation transformer and the inverter module transformer, establishing a temperature-current coupling model, and using the control and monitoring module to estimate the core temperature of the battery through a thermocouple model. Voltage consistency control: If the detected single-cell voltage deviation is greater than 50mV, the control and monitoring module activates the balanced charging mode and switches the parallel discharge resistor to the high-voltage single cell.

2. The lithium battery charging control method based on AC-DC-AC isolation conversion according to claim 1, characterized in that, The input feature analysis includes the control and monitoring module sampling the voltage waveform of the input terminal, i.e., the AC / DC compatible input module, in real time. When a 50 / 60Hz sine wave is detected, it is marked as AC input mode; when a stable DC with ripple <5% is detected, it is marked as DC input mode; if the feature cannot be identified within 30 seconds, the fault code "E01" is triggered. The safety access verification includes the control and monitoring module detecting that the battery temperature is > 45℃, or the single cell voltage difference is > 0.3V, or the SOC is > 95%, triggering a safety lock to stop charging and sending an alarm signal to the control module.

3. The lithium battery charging control method based on AC-DC-AC isolation conversion according to claim 1, characterized in that, The dynamic reconstruction of the current path by controlling the switch action includes: In AC mode, the switching network completes the conversion of electrical energy and battery charging by multiplexing the PFC rectifier bridge arm of the motor controller and the high-frequency inverter of the generator controller, as well as the rectifier bridge arm of the motor controller. When the input mode is AC input, close switch groups S2, S4, S5, S7, S8; disconnect switch groups S1, S3, S6; the power device multiplexing function is mapped as follows: motor controller bridge arm 1 is mapped to PFC rectification, generator controller H-bridge is mapped to high-frequency inverter, and motor controller bridge arms 2 / 3 are mapped to isolation rectification.

4. The lithium battery charging control method based on AC-DC-AC isolation conversion according to claim 3, characterized in that, The method of dynamically reconstructing the current path by controlling the switch action also includes: In DC mode, the system achieves a direct path to the DC bus by multiplexing the DC / DC converter, while maintaining a path similar to that in AC mode. When the input mode is DC input, close switch groups S2, S4, S5, S6, and S8; disconnect switch groups S1, S3, and S7; the power device multiplexing function is mapped as follows: the generator controller H-bridge is mapped to high-frequency inverter, and the motor controller full-bridge is mapped to isolation rectification.

5. A lithium battery charging control method based on AC-DC-AC isolation conversion according to claim 1, characterized in that, The switching network reconfiguration of the charging path also includes load balancing protection: The temperature of the multiplexed power devices is monitored in real time. When the temperature is > 85℃, the device switches to the standby bridge arm and reduces the output current by 5%. The load balancing protection rotates the main bridge arm every 5 minutes to extend the device life.

6. The lithium battery charging control method based on AC-DC-AC isolation conversion according to claim 1, characterized in that, The adaptive optimization charging phase specifically includes: During the pre-charge phase, when the SOC is less than 5%, the battery is woken up with a small current of 0.1C, and the output voltage of the isolation transformer is controlled. During the constant current fast charging phase (5% ≤ SOC < 80%), the current is set to 1C. The battery temperature is monitored in real time during charging, and the charging current is adjusted according to the temperature rise. At the same time, the PWM duty cycle of the generator controller H-bridge is adjusted. During the pulse charging phase (80% ≤ SOC < 95%), charging is performed using a precise 200Hz pulse current. By utilizing the fast shutdown characteristics of the motor controller, precise pulse control without the need for additional hardware is achieved. During the constant voltage trickle charging stage, when the SOC is greater than 95%, trickle charging is performed in constant voltage mode when the battery is close to full charge. Among them, the output AC power module outputs voltage during the constant voltage trickle charge stage, and the control and monitoring module decides on the switching of the charging stage and pulse timing control.

7. A lithium battery charging control system based on AC-DC-AC isolation conversion, executing the lithium battery charging control method based on AC-DC-AC isolation conversion as described in any one of claims 1 to 6, characterized in that, It includes an AC / DC compatible input module, an AC-DC conversion module, an isolation transformer and inverter module, a control and monitoring module, and an output AC power supply module; The AC / DC compatible input module provides the system with electrical energy through the input voltage and connects to the AC-DC conversion module to convert AC power to DC power. The DC output of the AC-DC conversion module is connected to the isolation transformer and inverter module, which converts DC power back to AC power and outputs it to charge the lithium battery. The control and monitoring module is interconnected with each other. The output AC power module is connected to the battery to provide the final charging power for the lithium battery.

8. A lithium battery charging control system based on AC-DC-AC isolation conversion according to claim 7, characterized in that, The AC / DC compatible input module is configured to provide AC / DC power input to the charging system, which typically comes from the vehicle generator or grid power / DC charging pile input. The AC-DC converter module is configured to convert the input AC power into stable DC power for subsequent charging. The isolation transformer and inverter module are configured to achieve electrical isolation and inverter functions, and to charge the lithium battery; Among them, the isolation transformer provides electrical isolation for the lithium battery charging process, preventing direct electrical connection between the lithium battery and the power grid or vehicle generator; the inverter converts DC power to AC power and regulates the output voltage and current. The output AC power module is configured to invert the converted DC power into AC power with a suitable frequency and voltage to charge the lithium battery.

9. A lithium battery charging control system based on AC-DC-AC isolation conversion according to claim 7, characterized in that, The control and monitoring module is configured to perform intelligent control and real-time monitoring of the entire charging system, including real-time monitoring of the charging status of the lithium battery, the operating status of the power devices, and the input and output voltage and current. Monitoring the charging status of lithium batteries includes real-time monitoring of the charging status of lithium batteries through battery voltage, current and temperature sensors to ensure that the charging process of lithium batteries is within a safe range. Monitoring the operating status of power devices includes real-time monitoring of the motor controller and generator controller to ensure full operation during charging.

10. A lithium battery charging control system based on AC-DC-AC isolation conversion according to claim 9, characterized in that, The control and monitoring module also includes functions for optimizing the charging process. Based on the battery charging curve, the output current and voltage are automatically adjusted to ensure that the lithium battery charging curve always meets the lithium battery charging requirements; it also includes intelligent control: the control module automatically adjusts the working status of the inverter and AC-DC conversion module based on real-time data, optimizes the load of power devices, and realizes the reuse of power devices.

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