Off-grid alkaline hydrogen production system and power adaptive distribution and safety control method thereof

Abstract

The invention relates to the technical field of off-grid renewable energy hydrogen production, and discloses an off-grid alkaline hydrogen production system and a power adaptive distribution and safety control method thereof, the off-grid alkaline hydrogen production system comprises a renewable energy power supply unit, a parallel electrolytic cell module, a gas-liquid treatment system and a main controller; in the Faraday hydrogen production mode, the bubble volume is compressed by adjusting the operation pressure so as to modulate the impedance characteristic of the electrolytic cell, and the energy efficiency is improved in cooperation with current control; and in the non-Faraday polarization hot standby mode, the voltage of the rectifier cabinet is controlled to be clamped to a non-gassing polarization interval, and liquid level plugging is constructed in the U-shaped communicating pipeline according to the fluid statics principle. The system is further provided with a transient buffering strategy based on the pneumatic capacity, and pressure attenuation is delayed through the gas dead zone volume when power is suddenly reduced. The problems of hydrogen production efficiency optimization, low-power safe hot standby and mechanical protection under wide power fluctuation are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of off-grid renewable energy hydrogen production technology, specifically to an off-grid alkaline hydrogen production system and its power adaptive allocation and safety control method. Background Technology

[0002] Off-grid alkaline water electrolysis for hydrogen production is a key approach to achieving green hydrogen production using renewable energy sources such as wind and solar power. However, this technology faces a core challenge in practical applications: the output power of renewable energy sources is highly random, volatile, and intermittent. This unstable energy input causes the electrolyzer to operate under a wide range of varying operating conditions for extended periods, fundamentally different from the steady-state operating conditions of traditional grid-connected hydrogen production.

[0003] During the high-power output phase of renewable energy, the current density in the electrolyzer increases significantly, leading to a sharp acceleration in the bubble formation rate on the electrode surface and near the diaphragm. Existing control strategies mostly employ fixed pressure or simple pressure servo control, failing to establish a dynamic correlation between pressure and bubble morphology. This results in a large number of bubbles failing to detach in time and adhering to the electrode surface or suspending in the electrolyte, increasing the ohmic impedance and polarization overpotential of the solution, causing a significant decrease in energy conversion efficiency under dynamic high loads.

[0004] Meanwhile, due to the intermittent nature of energy supply, the system frequently falls into low-power operation or standby mode. In the low-power range, the extremely low gas output rate makes it difficult to maintain pressure balance and airtightness across the diaphragm, easily leading to hydrogen and oxygen cross-contamination and potential safety hazards. Simple shutdown procedures, on the other hand, can cause galvanic cell reactions within the electrolysis chamber, and the resulting reverse current accelerates the corrosion of the plates and catalyst. Furthermore, when sudden changes in external weather conditions cause a millisecond-level drop in input power, existing pressure control systems often respond with lag, leading to a rapid and uncontrolled pressure collapse within the system. This transient pressure collapse can easily induce sudden boiling within the electrolyte or create a destructive pressure differential across the diaphragm, damaging the electrolyzer's mechanical structure. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an off-grid alkaline hydrogen production system and its power adaptive allocation and safety control method, which solves the problems of insufficient safety during low-power operation, low efficiency during high-power operation, and reduced equipment lifespan caused by wide fluctuations in input power in off-grid renewable energy hydrogen production systems.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] The first aspect of the present invention provides an off-grid alkaline hydrogen production system, including a renewable energy power supply unit, multiple parallel alkaline electrolyzer modules, a public gas processing system, a circulating liquid circuit system, and a main controller.

[0008] The output of the renewable energy power supply unit is connected to the DC bus; multiple alkaline electrolyzer modules are connected in parallel to the DC bus, and each alkaline electrolyzer module includes an electrolyzer body and a rectifier cabinet;

[0009] The public gas processing system is connected to the alkaline electrolyzer module via a gas manifold, and includes a hydrogen-side pipeline, an oxygen-side pipeline, and a main back pressure valve assembly with hydrogen-side regulating valves and oxygen-side regulating valves.

[0010] The circulating fluid system includes a circulating pump and a U-shaped connecting pipe between the hydrogen-side pipeline and the oxygen-side pipeline;

[0011] The main controller is configured to execute the following control logic:

[0012] Based on the collected power data of renewable energy power supply units, a predicted power is generated. Based on the predicted power, the operating state of the off-grid alkaline hydrogen production system is determined to be either the Faraday hydrogen production mode or the non-Faraday polarization hot standby mode.

[0013] When in Faraday hydrogen production mode, an active impedance regulation strategy is implemented: the main back pressure valve group is controlled to regulate the operating pressure of the off-grid alkaline hydrogen production system. Through the compression effect of the operating pressure change on the volume of bubbles in the electrolyte, the porosity of the electrolyte bubbles is reduced to modulate the impedance characteristics of the electrolyzer body, and the output current of the rectifier cabinet is adjusted in conjunction with the regulation.

[0014] When in non-Radidatic polarization hot standby mode, an electrochemical polarization and liquid level blocking strategy is executed: a command is sent to the rectifier cabinet to clamp the output voltage in the non-gas evolution polarization range between the polarization maintenance reference voltage and the theoretical decomposition voltage; at the same time, the relative opening of the hydrogen-side regulating valve and the oxygen-side regulating valve is controlled, and a gas-liquid level height difference is constructed in the U-shaped connecting pipeline based on the principle of hydrostatics to block the gas exchange between the hydrogen side and the oxygen side.

[0015] Preferably, the main controller has a pre-built pressure bubble coupled electrolysis characteristic model, which characterizes the physical mapping relationship between the operating pressure, bubble porosity, and electrolyte ohmic resistance of the off-grid alkaline hydrogen production system. When executing the active impedance adjustment strategy, the main controller uses the pressure bubble coupled electrolysis characteristic model to construct a real-time optimization problem with the objective of maximizing the instantaneous hydrogen production of the off-grid alkaline hydrogen production system under the predicted power constraint. It solves and outputs the optimal operating pressure value of the system and the current distribution value of each electrolyzer required to compress the bubbles to a preset volume threshold.

[0016] Preferably, the specific steps of the main controller executing the electrochemical polarization and liquid level blocking strategy include: outputting a voltage control command to the rectifier cabinet to maintain the voltage at both ends of the electrolyzer body in the non-gas evolution polarization range; calculating the minimum liquid level height difference required to block the micropores of the electrolyzer diaphragm, and calculating the pressure difference between the hydrogen side and the oxygen side required to establish the minimum liquid level height difference, thereby controlling the opening of the hydrogen side regulating valve and the oxygen side regulating valve to form the blocking gas liquid level height difference in the U-shaped connecting pipeline.

[0017] Preferably, in the non-Radida polarization hot standby mode, the main controller sends a speed reduction command to the circulating pump, reducing the circulating pump flow rate setpoint to the minimum maintenance flow rate for laminar flow, so as to reduce the disturbance of fluid turbulence on the height difference of the barrier gas liquid level in the U-shaped connecting pipe.

[0018] Preferably, the main controller is configured with a transient buffer control strategy based on pneumatic capacity: when the predicted power decrease rate is detected to exceed the preset decrease rate threshold, the main back pressure valve group is preferentially instructed to close before reducing the output current of the rectifier cabinet; then the gas discharge volume flow command is calculated, and the main back pressure valve group is controlled to maintain a small and precise opening. The compressibility of the gas dead zone volume in the public gas handling system and connecting pipeline is used as a pneumatic spring to maintain the operating pressure of the off-grid alkaline hydrogen production system according to the preset safety curve.

[0019] Preferably, the main controller monitors the actual rate of change of operating pressure in the off-grid alkaline hydrogen production system. When the actual rate of change of operating pressure exceeds the maximum allowable pressure decay rate, the main back pressure valve group opening is corrected by PID control.

[0020] Preferably, the main controller uses a dual-threshold determination mechanism to determine the operating state: setting an opening threshold above the gas production start-up power threshold and a closing threshold below the gas production start-up power threshold; determining to switch to Faraday hydrogen production mode only when the predicted power rises and exceeds the opening threshold; determining to switch to non-Faraday polarization hot standby mode only when the predicted power falls and falls below the closing threshold.

[0021] Preferably, the main controller performs state parameter acquisition and power ultra-short-term trend prediction: it acquires the historical power data sequence of renewable energy power supply units within a fixed time window before the current moment, calculates the power change trend sequence in a short period of time in the future through trend prediction logic, and generates predicted power.

[0022] Preferably, the main controller also performs temperature management and mode recovery logic: during the non-Faraday polarization hot standby mode, the temperature of the electrolyzer body is monitored. If the temperature is lower than the preset cold standby temperature threshold, the voltage setting value is increased to utilize the Joule heating effect to raise the temperature. When the system needs to be restored to the Faraday hydrogen production mode, the main back pressure valve group is adjusted first to eliminate the set pressure difference between the hydrogen side and the oxygen side. After the liquid level in the U-shaped connecting pipeline is restored to balance, the current is increased to the gas production level.

[0023] A second aspect of this invention provides a power adaptive allocation and safety control method for an off-grid alkaline hydrogen production system, comprising the following steps:

[0024] S1. The main controller collects the real-time power of the renewable energy power supply unit to form a historical data sequence, and calculates the predicted power within a preset future time period based on the historical data sequence;

[0025] S2. The main controller compares the predicted power with the preset threshold and locks the off-grid alkaline hydrogen production system into one of the following modes: Faraday hydrogen production mode, non-Faraday polarization hot standby mode, or shutdown maintenance mode.

[0026] S3. If in Faraday hydrogen production mode, the main controller executes an active impedance adjustment strategy, calculates and outputs the optimal operating pressure value and current distribution value of each electrolyzer using the pressure bubble coupled electrolysis characteristic model; if in non-Faraday polarization hot standby mode, the main controller executes an electrochemical polarization and liquid level blocking strategy, generates a voltage clamping command, and calculates the pressure difference required to establish liquid level blocking to generate a differential pressure blocking command.

[0027] S4. The main controller will send the generated command to the rectifier cabinet, the main back pressure valve group and the circulating pump. When it detects that the predicted power drop rate exceeds the preset drop rate threshold, it will first command the main back pressure valve group to move in the closing direction to start the transient buffer control strategy. It will use the gas dead zone volume to maintain the off-grid alkaline hydrogen production system operating pressure according to the preset safety curve.

[0028] S5. The main controller monitors the status of the off-grid alkaline hydrogen production system, performs PID correction on the actual change rate of the operating pressure of the off-grid alkaline hydrogen production system, executes one of the following logics: temperature recovery, and then returns to step S1.

[0029] The technical solution provided by this invention reduces electrolysis ohmic losses and improves hydrogen production efficiency under dynamic power by adjusting bubble volume through variable pressure operation in the Faraday hydrogen production mode; it prevents electrode corrosion and gas crosstalk by combining voltage clamping and liquid level sealing in the non-Faraday polarization hot standby mode, thus achieving safe hot standby of the system under low power conditions; and it ensures the safety of the system's mechanical structure by using transient buffer control based on pneumatic capacity to smooth pressure fluctuations caused by sudden power drops through the system's inherent dead zone volume.

[0030] This invention provides an off-grid alkaline hydrogen production system and its adaptive power allocation and safety control method. It offers the following advantages:

[0031] 1. This invention implements an active impedance adjustment strategy under Faraday hydrogen production mode, which actively compresses the volume of bubbles in the electrolyte by increasing the system operating pressure, thereby reducing the ohmic impedance of the electrolyte caused by the bubble porosity. This enables the alkaline electrolyzer to dynamically adjust its impedance characteristics under the condition of wide fluctuations in renewable energy power, reducing electrolysis overpotential and improving hydrogen production efficiency.

[0032] 2. This invention implements an electrochemical polarization and liquid level blocking strategy under non-Radidatic polarization hot standby mode. It utilizes voltage clamping in the non-gas evolution polarization region to maintain the double electric layer structure on the electrode surface to suppress reverse current corrosion. At the same time, it uses the pressure difference in the U-shaped connecting pipe to create a liquid level height difference to physically block the diffusion of hydrogen and oxygen gases. This solves the problems of equipment lifespan degradation and gas crosstalk safety in low-power or intermittent shutdown states.

[0033] 3. This invention employs a transient buffer control strategy based on pneumatic capacity to prioritize the main back pressure valve group to close during the predicted rapid power drop phase. By utilizing the gas dead zone volume within the public gas processing system and pipelines, the system pressure decay rate is slowed down, preventing electrolyte boiling and mechanical damage to the diaphragm reverse osmosis caused by pressure runaway due to sudden power drop, thus ensuring the structural safety of the system under extreme variable operating conditions. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the overall hardware architecture of the off-grid alkaline hydrogen production system of the present invention;

[0035] Figure 2 This is a schematic diagram of the main flow of the power adaptive allocation and safety control method of the present invention;

[0036] Figure 3 This is a logic block diagram of power distribution and impedance modulation in the Faraday hydrogen production mode of the present invention;

[0037] Figure 4 This is a schematic diagram of the non-gas-generating pressure-maintaining strategy under the non-Radida polarization hot standby mode of the present invention;

[0038] Figure 5 This is a schematic diagram illustrating the principle of the transient buffer control strategy based on aerodynamic capacity of the present invention. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] See attached document Figure 1 This invention provides an off-grid alkaline hydrogen production system and its power adaptive allocation and safety control method. The hardware architecture of the off-grid alkaline hydrogen production system includes a renewable energy power supply unit, a DC bus, multiple parallel alkaline electrolyzer modules, a public gas processing system, a circulating liquid circuit system, and a main controller.

[0041] The output of the renewable energy power supply unit is physically connected to the DC bus input, configured to convert fluctuating electrical energy generated by wind or solar power into DC power. The DC bus output is connected to the rectifier cabinet input of each alkaline electrolyzer module via shunt busbars. Each alkaline electrolyzer module consists of an electrolyzer body, a rectifier cabinet connected in series with it, and pressure monitoring instruments installed at the hydrogen and oxygen outlets respectively. The rectifier cabinet is equipped with a power regulation circuit that adjusts the DC voltage and current applied to the electrodes of the electrolyzer body in response to control commands.

[0042] The utility gas handling system is connected to the outlets of all alkaline electrolyzer modules via a gas manifold. Along the gas flow direction, the utility gas handling system sequentially includes a gas-liquid separator, a gas purification tower, a dryer, and a main back pressure valve assembly. The gas-liquid separator is configured as a gravity or cyclone separator to separate the electrolyte from the gas-liquid mixture. The main back pressure valve assembly includes independently actuated hydrogen-side and oxygen-side regulating valves to specifically regulate the back pressure on the hydrogen and oxygen sides of the system, respectively.

[0043] The circulating liquid circuit system adopts an independent parallel liquid supply structure. The circulating liquid circuit system includes an alkaline storage tank, a circulating pump, and a U-shaped connecting pipe between the liquid phase outlet of the hydrogen-side gas-liquid separator and the liquid phase outlet of the oxygen-side gas-liquid separator. A liquid level difference measuring instrument is installed on the U-shaped connecting pipe or on the side wall of the gas-liquid separator to monitor the relative height difference between the liquid levels on the hydrogen and oxygen sides. The off-grid alkaline hydrogen production system and its power adaptive allocation and safety control method utilize a variable frequency drive for the circulating pump to regulate the electrolyte flow rate through each electrolyzer.

[0044] The main controller is connected to the power supply unit, DC bus monitoring instruments, rectifier cabinets, pressure and level monitoring instruments, and actuator valves via signal cables. The internal logic of the main controller is divided into six functional units: data acquisition, status prediction, power absorption and allocation, mode discrimination, optimization decision-making, and execution drive.

[0045] The core control concept of the main controller embodies an integrated strategy of prediction, maximizing energy absorption and allocation, and safety boundary control: First, the state prediction unit predicts the power trend. Then, the power absorption and allocation unit and the optimization decision-making unit, with maximizing the total energy consumption of the system as the primary objective, dynamically calculate the number of electrolyzers to be put into operation and the power benchmark for each cell based on real-time renewable energy power and the health status of each electrolyzer, thus solving the problem of multi-machine parallel coordination under fluctuating power. At the same time, the modal discrimination unit switches the operating strategy at different power levels according to the preset safety boundary, ensuring that the system always operates within the safe range.

[0046] In the implementation of the control logic, the data acquisition unit reads physical quantities in real time, including the total available power of the renewable energy power supply unit, the temperature of each tank, the system pressure, the hydrogen-oxygen pressure difference, and the liquid level difference. The state prediction unit calculates the power change trend within a preset future time period based on the power data within the historical time window. The modal discrimination unit compares the predicted total available power with the system's minimum operating power and rated power based on the power band mapping mechanism to determine the system's current operating strategy.

[0047] When the predicted power is within the high-efficiency operating power range, and the system enters the Faraday hydrogen production zone, the main controller executes a power allocation logic based on active modulation of bubble porosity to maximize the absorption of electrical energy within a limited power fluctuation range and prevent forced curtailment of solar and wind power due to excessive voltage. This power allocation logic is based on the physical principle that the ohmic internal resistance of the electrolyzer is positively correlated with the bubble porosity in the electrolyte, while the bubble porosity is negatively correlated with the system operating pressure. Based on the power increase trend signal output by the state prediction unit, the controller pre-calculates the target pressure value required to compress the bubbles to a preset volume threshold. Since the pressure build-up in the fluid system has a lag, the controller pre-drives the main back pressure valve group to reduce its opening to gradually increase the system pressure when it predicts that the power is about to enter the peak range. This strategy aims to solve the bottleneck problem of high-power absorption in off-grid scenarios: by physically compressing the volume of microbubbles on the electrode surface, the effective conductive cross-sectional area between the electrodes is increased, thereby reducing the internal resistance of the electrolyzer. This prevents voltage overshoot from triggering shutdown protection, and also allows the electrolytic cell to accommodate a larger current density under the same voltage limit, thereby improving the system's ability to absorb continuous instantaneous peak power and reducing energy waste.

[0048] When the predicted power drops below the gas production initiation threshold but does not meet the shutdown conditions, in order to maintain the system's rapid response capability and avoid cold start energy consumption, when the system is determined to have entered the non-Radida polarization hot standby zone, which corresponds to the low-power maintenance mode of the off-grid system, the controller drives the rectifier cabinet to clamp the output voltage within a specific non-gas evolution range between the polarization maintenance reference voltage (typically 0.8 V) and the theoretical decomposition voltage (typically 1.23 V). Within this voltage range, the current is mainly used to maintain the charge state of the electrode double layer and generate Joule heat to maintain the tank temperature, without triggering continuous electrochemical gas evolution reactions, thus achieving extremely low power consumption hot standby when the system is not producing gas. At the same time, the main controller activates the dynamic liquid seal control logic: by controlling the relative opening of the hydrogen-side regulating valve and the oxygen-side regulating valve, a small preset pressure difference is established between the hydrogen and oxygen sides. This small preset pressure difference is strictly limited to the mechanical safety pressure difference threshold allowed by the electrolyzer diaphragm (e.g., less than 3 kPa). A small, pre-set pressure difference acts on the electrolyte within the connecting pipe, forcing the liquid to form a height difference that balances the pressure difference. This height difference physically constitutes a liquid barrier layer, increasing the resistance to the diffusion path of gas molecules through the membrane, thereby preventing the mixing of hydrogen and oxygen gases without producing gas.

[0049] Furthermore, to achieve electrical coordinated control and safety protection in off-grid environments, the controller is equipped with pneumatic buffer logic based on gas production rate feedforward. When the predicted power change rate exceeds the preset decrease rate threshold, the controller, based on the predicted gas production attenuation trend, prioritizes locking or slightly closing the main back pressure valve group before reducing the current at the rectifier cabinet. This utilizes the expansion characteristics of the gas stored in the pipeline and separator to maintain the system in a positive pressure state, preventing the system from collapsing due to negative pressure caused by the instantaneous cessation of gas production.

[0050] See attached document Figure 2 This control method employs a closed-loop dynamic adjustment mechanism, with the main controller periodically executing the following steps according to a specific timing sequence:

[0051] Step S1: System Status Parameter Acquisition and Power Ultra-Short-Term Trend Prediction. The controller reads the current physical status data of the system and the input signals from the power supply side through each sensor interface at a preset sampling frequency. The read data includes: the real-time output power value of the renewable energy power supply unit, the temperature value of the electrolyte inside each electrolyzer module, the liquid level height value in each gas-liquid separator, the pressure value in the system's common pipeline, and the gaseous impurity concentration value in the hydrogen pipeline.

[0052] After acquiring real-time power data, the controller initiates its built-in trend prediction logic. This logic, based on a sequence of historical power data within a fixed time window prior to the current moment, calculates a power change trend sequence for a short future period using linear extrapolation or autoregressive algorithms. The predicted power change trend sequence includes estimated power values ​​for each future moment, used to identify rapid increases or decreases in power before the actual power is reached, providing a time margin for mechanical actuators to act in advance.

[0053] Step S2: Determining the operating mode range based on power bands. The controller divides the system operation into multiple power bands based on the total available power and presets a corresponding safe operating mode for each power band. In practice, the controller compares the predicted power values ​​with the system's key thresholds. Through this mapping mechanism based on power bands and operating states, the system's operating state is locked as either Faraday hydrogen production mode, non-Faraday polarization hot standby mode, or shutdown maintenance mode.

[0054] When the predicted power value is greater than or equal to the preset gas production start-up power threshold, the system is determined to have entered the Faraday hydrogen production mode. In the Faraday hydrogen production mode, the controller aims to maximize hydrogen production. At this time, the current density in the electrolyzer supports continuous electrolysis reaction, and the purity of the produced gas meets the set standard.

[0055] When the predicted power value is between zero and the gas production start-up power threshold, the system is determined to have entered the non-Radidatic polarization hot standby mode. In the non-Radidatic polarization hot standby mode, the input power is insufficient to maintain continuous gas desorption, and the control objective changes to stopping gas production. Low current is used to maintain the polarization potential of the electrode surface and the system temperature to ensure that the system can respond to power recovery commands at any time.

[0056] When the predicted power value is close to zero and the duration exceeds the preset standby time limit, the system is determined to enter the shutdown maintenance mode, triggering the power cut-off and system purging procedure.

[0057] Step S3: Multi-objective optimization decision-making and reference instruction generation. Based on the operating mode determined in step S2, the controller calls different physical control strategies to generate execution instructions.

[0058] If the system is in Faraday hydrogen production mode, the controller's core objective shifts to maximizing the utilization of renewable energy power. To this end, the controller implements an innovative active impedance regulation strategy. This strategy not only allocates current but also actively alters the physical characteristics of the electrolyzers by adjusting system pressure to accommodate greater instantaneous power. Based on the current equivalent circuit model of the electrolyzers, the controller calculates the optimal operating pressure and current allocation for each electrolyzer under the current total power input. This calculation logic is based on the physical principle that under high current density conditions, increasing system pressure compresses the volume of bubbles on the electrode surface, reducing the porosity of the gas-liquid mixture and thus decreasing the ohmic resistance of the electrolyte. Accordingly, the controller outputs a higher pressure setpoint to the back pressure valve group and a corresponding current setpoint to each rectifier cabinet.

[0059] If the system is in non-Radar polarization hot standby mode, the controller executes an electrochemical polarization and liquid level sealing strategy. On the electrical side, the controller outputs voltage control commands to clamp the voltage applied across the electrolyzer within a specific range (e.g., 0.8V to 1.2V) below the theoretical decomposition voltage. Within this voltage range, electrical energy is mainly converted into charge to maintain the double-layer structure of the electrodes and heat energy to maintain the tank temperature, without triggering a large-scale gas evolution reaction. On the mechanical side, the controller calculates the minimum liquid level height difference required to seal the micropores of the electrolyzer diaphragm, and then calculates the hydrogen-oxygen side pressure difference required to establish the minimum liquid level height difference based on the principle of hydrostatics. The controller decomposes the hydrogen-oxygen side pressure difference into opening commands for the hydrogen-side back pressure valve and the oxygen-side back pressure valve, so that the hydrogen-side set pressure is slightly higher or slightly lower than the oxygen-side set pressure, thereby constructing a stable liquid seal barrier in the connecting pipeline.

[0060] During the transition process of establishing the liquid seal barrier, the main controller synchronously sends a speed reduction command to the variable frequency drive circulating pump of the circulating liquid circuit system. The controller reduces the flow rate setpoint of the circulating pump to the minimum sustaining flow rate required to maintain laminar flow, thereby reducing the disturbance of fluid turbulence to the gas-liquid interface within the U-shaped connecting pipe and preventing the liquid seal from being breached or the liquid level from becoming unstable due to excessive flow velocity. The system then waits for the liquid level difference measuring instrument to report that the liquid level difference has stabilized at the set value. Then, the controller fine-tunes the pump speed according to thermal management requirements.

[0061] Step S4: Electrical Co-operation and Transient Pneumatic Buffering Based on Gas Production Rate Feedforward. The controller sends the generated electrical commands and valve action commands to the actuator. To achieve electrical coordination control and avoid delay mismatch between power fluctuations and gas system response, the controller adopts asynchronous timing control based on power prediction for scenarios with rapid power changes.

[0062] When a rapid increase in power is predicted, the controller executes a pre-depressurization or opening maintenance strategy: before increasing the electrolytic rectifier current, it instructs the main back pressure valve group to maintain the current opening or moderately increase the opening to reserve space for gas expansion and prevent the system instantaneous pressure overshoot caused by the subsequent surge in gas production.

[0063] When a rapid decrease in power is predicted, the controller executes a back pressure maintenance strategy: before reducing the electrolytic rectifier current, it prioritizes instructing the main back pressure valve assembly to close. Since the reduction in gas production is instantaneous, while pressure changes have inertia, the controller utilizes the gas volume accumulated in the pipeline and separator as a buffer gas source (pneumatic spring), in conjunction with the pre-closing action of the valves, to maintain the system pressure following a preset safety curve during the reduction in gas production, preventing system pressure drops or negative pressure formation due to delayed valve closure.

[0064] Step S5: Safety Closed-Loop Feedback and Exit Logic. The controller monitors the temperature of each electrolyzer in real time. If the temperature of an electrolyzer is detected to be lower than the preset cold standby temperature threshold during hot standby mode, the controller automatically increases the voltage setpoint of that electrolyzer, utilizing the increased Joule heating effect to raise the temperature. When the system needs to recover from hot standby mode to hydrogen production mode, the controller executes the pressure balance reset logic: it first adjusts the back pressure valve to eliminate the artificially set pressure difference on the hydrogen and oxygen sides, and after the liquid level in the connecting pipe returns to balance, it then releases the voltage clamping restriction and increases the current to the gas production level to prevent electrolyte from being carried into the gas pipeline by the gas flow due to liquid level fluctuations.

[0065] See attached document Figure 2 In step S1, the main controller performs data preprocessing and trend calculation. The controller is internally configured with a first-in, first-out (FIFO) data buffer to store the most recent data from the renewable energy power supply units. A power data sequence for 1 sampling period. Let the current sampling time be 1. The sampling period is .

[0066] To eliminate random noise interference from the source input, the controller first performs a weighted moving average calculation on the historical data in the buffer to calculate the smoothed power reference value at the current moment. Based on this, in order to overcome the physical response delay of the actuator in a high-power electrolysis system, the controller uses a first-order trend extrapolation model to calculate the power value at future times. This calculation process is performed according to the following formula:

[0067] ;

[0068] in: Indicates the current sampling time Calculated future sampling time The predicted power value at that time, in kilowatts; This represents the smoothed power baseline value at the current moment after noise reduction processing, in kilowatts. This represents the slope of the current power change trend calculated from historical data, used to characterize the rate and direction of power change, and is measured in kilowatts per second.

[0069] Regarding the slope of the current power change trend To acquire the data, the controller employs a multi-point differential weighting algorithm: calculating the difference between two adjacent historical power sampling points within the buffer and then averaging these differences. To improve the prediction's sensitivity to recent abrupt changes, the weighting coefficients are assigned according to a rule that they decrease exponentially with the time distance between the sampling point and the current moment; that is, data points closer to the current moment are assigned greater weights.

[0070] In step S2, the controller executes mode discrimination logic with hysteresis based on the above calculation results. To prevent frequent oscillations between different modes caused by small fluctuations in the predicted power near the threshold, the controller constructs a dual-threshold determination mechanism.

[0071] Set the system rated power to The basic reference value for the initial gas production power is Based on a basic reference value for the initial gas production power, the controller sets an activation threshold. and the closing threshold Among them, the activation threshold Set to a dead zone increment higher than the basic reference value by a preset value, and disable the threshold. It is set to reduce the dead zone by a preset value below the basic reference value.

[0072] The specific switching logic is as follows:

[0073] If the system is currently in a non-Laday polarization hot standby mode, the controller monitors and predicts the power in real time. Only when Rise and exceed the activation threshold When the controller determines that the power increase condition is met, it triggers the switching command to the Faraday hydrogen production mode and starts the back pressure valve pre-pressurization program.

[0074] If the system is currently in Faraday hydrogen production mode, the controller monitors and predicts the power in real time. Only when Falling below the shutdown threshold When the controller determines that the power reduction condition is met, it triggers a switching command to the non-Radida polarization hot standby mode and starts the buck and liquid seal establishment procedure.

[0075] If the system operates in non-Laday polarization hot standby mode and the predicted power remains below the shutdown threshold close to zero, The controller will start a timer. The timer will only activate if the accumulated standby time exceeds a preset threshold. When the controller determines that it has entered the shutdown maintenance mode, it will perform a power-off operation.

[0076] The final mode switching command and corresponding current reference command are output. At that time, the controller uses a ramp function generator to control the rate of change of the command. A limit is imposed. This limit ensures that even if the predicted power changes abruptly, the actual current command applied to the electrolyzer will transition smoothly at a rate that matches the physical capacity of the equipment, preventing impact on the power grid or causing drastic fluctuations in the liquid level of the gas-liquid separator.

[0077] See attached document Figure 3 After step S2 determines that the system is in Faraday hydrogen production mode (Mode A), the main controller enters the execution phase of step S3, executing an active impedance adjustment strategy based on multi-physics coupling. At this time, the controller adjusts the power output based on the predicted power generated in step S1. The aim is to solve the problem of increased internal resistance of electrolytic cells caused by bubble adhesion under high current density conditions. It not only uses current as an adjustment quantity, but also uses the system operating pressure as an active control variable that can change the ohmic characteristics of the electrolytic cell.

[0078] The controller has a pre-installed pressure bubble coupled electrolysis characteristic model. This model is based on the interaction mechanism of fluid mechanics and electrochemistry: within the electrolyte flow channel, the pressure applied to the electrode surface directly determines the diameter of the precipitated bubbles and their desorption rate. As the system pressure increases, the volume of the microbubbles is physically compressed, reducing the bubble porosity in the gas-liquid two-phase flow, thereby increasing the effective conductive cross-sectional area of ​​the electrolyte and significantly reducing the equivalent ohmic resistance of the solution.

[0079] To quantify this physical process and solve for optimal control, the controller calculates the first voltage characteristic equation based on the following voltage characteristic equation. The terminal voltage of an electrolytic cell under specific pressure and current. :

[0080] ;

[0081] in: Representing the The terminal voltage of an electrolytic cell under specific pressure and current, expressed in volts; Represents the reversible voltage under standard conditions, measured in volts; Represents the flow through the first The DC current of each electrolytic cell, in amperes; This represents the effective geometric surface area of ​​a single electrode plate, expressed in square centimeters. The basic ohmic surface resistance of the pure electrolyte and structural components after excluding the influence of air bubbles, expressed in ohms square centimeters. This represents the current operating pressure setting of the system; Represents the bubble resistance coefficient, a physical quantity determined by the flow channel geometry and electrolyte surface tension, used to characterize the strength of the bubble's obstruction of the conductive path; The bubble compressibility index, ranging from 0.5 to 1.0, is used to characterize the nonlinear effect of pressure changes on bubble volume compression. and This represents the Tafel kinetic constant related to the activity of the electrode catalyst.

[0082] Furthermore, considering the significant impact of temperature on the electrolyte's ionic conductivity and bubble surface tension, the controller incorporates the basic ohmic surface resistance into its calculations. Introducing a temperature correction factor The corrected logic is as follows:

[0083] ;

[0084] in: This is the measured temperature; For reference temperature; This is the temperature sensitivity coefficient of the electrolyte.

[0085] Meanwhile, the controller dynamically adjusts the bubble resistance coefficient based on the real-time temperature. This is because increased temperature reduces the surface tension of the electrolyte, thereby decreasing the desorption diameter of bubbles and weakening the shielding effect of bubbles on the conductive cross section.

[0086] Based on the above physical model, the main controller constructs a real-time optimization problem with the objective of maximizing the instantaneous hydrogen production of the entire system. Within each control cycle, the controller searches for a set of optimal current allocation vectors. and the system's optimal operating pressure value .

[0087] The mathematical logic of this optimization problem is as follows:

[0088] Objective function: ;

[0089] Constraints:

[0090] ;

[0091] ;

[0092] in: This represents the overall instantaneous hydrogen production rate of the system. Represents the flow through the first The DC current of each electrolytic cell, in amperes; Representing the The terminal voltage of an electrolytic cell under specific pressure and current, expressed in volts; This represents the power conversion efficiency of the rectifier and distribution unit; This indicates the predicted power value generated by the controller based on step S1, in kilowatts. and These represent the minimum holding pressure and the maximum working pressure allowed by the system's mechanical design, respectively. This represents the current operating pressure setting of the system.

[0093] The controller's solution logic follows the following physical laws: when the predicted power... When a significant increase occurs, the optimization algorithm will automatically increase the operating pressure setpoint. This is because, under high current density conditions, the calculation formula, which characterizes the pressure drop of the bubbles, is crucial. The issue becomes apparent. This can be achieved by increasing the operating pressure setpoint. Although it will slightly increase the energy consumption of auxiliary equipment, the compression of bubbles will reduce the terminal voltage of the electrolytic cell. The decrease makes it possible to achieve the same input power constraint. Under these conditions, the system can accommodate a larger total current. This enables impedance matching and improved power absorption capacity at the physical level.

[0094] The calculated optimal operating pressure value DC current of each slot It is then sent to the actuator to complete the multi-physics collaborative execution in step S4.

[0095] See attached document Figure 4 When step S2 determines that the system operating conditions do not meet the gas production requirements and locks the mode to the non-Radida polarization hot standby mode (Mode B), the main controller initiates the non-gas production pressure maintenance strategy in step S3. The non-gas production pressure maintenance strategy aims to solve the problem of frequent cold start-ups and shutdowns caused by intermittent power supply, and includes two coordinated processes: polarization clamping on the electrical side and differential pressure blocking on the fluid side.

[0096] In the electrical control logic, the controller disconnects the current tracking loop based on gas production and instead establishes a voltage closed-loop control. The controller applies the voltage across the electrolyzer. The electrolyzer is forcibly locked within the non-gas evolution polarization region. The non-gas evolution polarization region is set to be greater than the open-circuit voltage of the electrolyzer and less than the thermal neutral voltage. Under this voltage excitation, the equivalent physical model of the electrolyzer exhibits the characteristics of a large-capacity electric double-layer capacitor. The input energy is mainly used to maintain the charge arrangement of the electric double layer on the electrode surface, rather than overcoming the potential barrier of the hydrogen evolution reaction, thereby maintaining electrochemical activity without producing hydrogen gas.

[0097] In the fluid control logic, to physically block the diffusion of impurity gases between the anode and cathode that would occur due to the cessation of gas evolution, the controller executes a dynamic liquid seal construction procedure. Based on the principle of hydrostatic equilibrium, the controller calculates the minimum gas path pressure difference required to force the electrolyte in the gas-liquid separator to overcome gravity and rise, thus submerging the diaphragm channels.

[0098] This calculation process is performed based on the following physical formula:

[0099] ;

[0100] in: This indicates the artificially set pressure difference, in Pascals, that must be established between the hydrogen-side pipeline and the oxygen-side pipeline in order to construct an effective liquid seal. This indicates the density of the circulating electrolyte at the current temperature monitoring value, in kilograms per cubic meter. This represents the gravitational acceleration constant, with a value of 9.8 meters per second squared. This indicates the geometrical vertical height difference between the upper edge of the gas outlet channel or diaphragm of the electrolyzer and the reference liquid level of the gas-liquid separator, in meters. This indicates the preset safety redundancy height of the liquid level to resist interference from liquid level fluctuations and ensure complete sealing, in meters.

[0101] In the execution phase of step S4, the controller, based on the calculated... Generate asymmetric backpressure commands. The controller uses the system's current baseline backpressure value as the center point and... Half of the value is used as a bias, which is added to the pressure setpoints on the hydrogen and oxygen sides respectively, thereby creating a directional pressure gradient within the system. The actuator responds to this command, adjusting the back pressure valve opening and using the gas pressure difference to drive the electrolyte column upwards to... At that height, the air connection path was physically severed.

[0102] Meanwhile, in the monitoring cycle of step S5, the controller monitors the temperature of the electrolyzer stack in real time. If the temperature is detected to be lower than the preset thermal backup limit, the controller will finely adjust and increase the applied voltage across the electrolyzer within the non-gas evolution polarization range. By utilizing the increased non-Radiladian leakage current effect caused by voltage rise, the Joule heating power generated by the internal resistance of the electrolytic cell is enhanced, thereby achieving self-sustaining heat control without external auxiliary heat sources.

[0103] See attached document Figure 5 When the prediction model in step S1 detects a sharp drop in input power that does not meet the steady-state operating conditions (e.g., the power drops within milliseconds due to the photovoltaic array being blocked by clouds), and the system has not yet reached the complete shutdown threshold, the main controller activates a transient buffer control strategy based on aerodynamic capacity in step S4.

[0104] The transient buffer control strategy utilizes the compressibility of gas within the inherent dead zone volume of the gas separator and connecting pipelines to take over the back pressure regulation logic at the instant electrochemical gas generation stops. To prevent pressure collapse due to valves not closing in time after gas generation ceases, or water hammer effects caused by valves closing too quickly, the controller must calculate an accurate compensation discharge flow rate. This control logic no longer simply follows the current signal, but aims to maintain the system pressure decreasing at a preset safe decay rate.

[0105] The controller calculates the gas emission volume flow command based on the law of conservation of mass and the differential form of the gas equation of state. The calculation formula is as follows:

[0106] ;

[0107] in: Indicates that the controller is in The constantly calculated gas discharge volume flow rate command required to maintain the system at a preset slope for depressurization, in cubic meters per second; This represents the total number of electrolytic cells connected in series in the electrolytic cell stack, and is a dimensionless integer; This represents the molar volume constant of a gas under standard conditions, expressed in cubic meters per mole. This represents the current Faraday current efficiency, which is obtained by looking up the efficiency curve stored inside the controller. This represents the measured input DC current value at the current moment, in amperes. This represents the Faraday constant, with a value of 96,485 coulombs per mole; The total physical volume of the gas phase space of the gas-liquid separator on the high-pressure side of the system and the connecting pipeline (i.e., the effective volume participating in the pneumatic buffer) is expressed in cubic meters. The polytropic expansion index represents the gas's expansion. For hydrogen, a value of 1.4 is recommended to characterize the thermodynamic properties of the gas expansion process. This represents the system absolute pressure value fed back by the sensor in real time, in Pascals. This indicates the maximum allowable pressure decay rate (negative value) preset by the controller. This parameter is determined based on the maximum transient pressure difference change rate that the diaphragm can withstand, and the unit is Pascals per second.

[0108] The controller will calculate the gas emission volume flow rate command. The valve flow characteristic curve is converted into a back pressure valve opening signal and sent to the actuator. As can be seen from the formula, when the input DC current value... When the flow rate drops sharply to near zero, the first term (gas production term) disappears, and the flow command is determined solely by the second term (pneumatic compensation term). At this point, Change to a value similar to the current pressure setting. Inversely proportional to the target maximum pressure decay rate A positive value that is directly proportional to the back pressure. This means that the controller will maintain the back pressure valve at a very small and precise opening, utilizing... The internally stored gas is released in a controlled manner, thereby forcing the system pressure to follow... The slope is set to descend smoothly, rather than in free fall.

[0109] During execution, step S5 continuously monitors the actual pressure change rate at a high-frequency sampling rate. If the absolute value of the actual pressure drop rate exceeds... If the pressure drops too quickly, the controller will use PID correction to adjust the opening calculated by the above formula, further reducing the valve opening until the pressure change trajectory returns to the preset safety buffer channel, ensuring the mechanical safety of the system during periods of drastic power fluctuations.

[0110] See attached document Figure 2 During the periodic execution of step S5, in order to achieve fault isolation and system reconfiguration in the off-grid environment, the main controller runs a stack health diagnosis algorithm based on statistical analysis and a sensor self-verification algorithm based on a physical mechanism model. When the calculated characteristic parameters deviate from the preset safety channel, the controller starts the fault handling program, directly and dynamically corrects the operating boundary parameters in step S4, and shields the failure node in the control loop to achieve fault crossing of the system. While isolating the fault point, it maximizes the stable operation of the remaining system and the ability to absorb renewable energy.

[0111] The controller acquires the voltage signal vectors of all series-connected cells in the electrolyzer stack in real time. To identify early faults (such as local consistency deviations caused by micro-blockages in the flow channels) that have not yet triggered the absolute voltage threshold but whose polarization characteristics have already deteriorated, the controller calculates the dispersion index of the voltage distribution. The calculation formula is as follows:

[0112] ;

[0113] in: This represents the standard deviation of the electrolytic cell voltage distribution at the current sampling moment, in volts. This represents the total number of electrolytic cells connected in series in the electrolytic cell stack, and is a dimensionless integer; Indicates the number of collected data. Real-time terminal voltage value of each electrolysis cell, in volts; This represents the arithmetic mean of all cell voltages at the current sampling time, in volts.

[0114] The controller will Compare with a preset health threshold. If If the threshold is exceeded, the controller determines that the stack consistency is abnormal and actively reduces the allowable upper limit of the global current command in step S4. This derating factor is related to... The overshoot is inversely proportional to the overshoot, thereby limiting the heat generation power of the abnormal chamber and preventing the fault from spreading.

[0115] Meanwhile, to prevent control instability caused by pressure sensor drift or freezing, the controller performs pressure residual verification based on the law of conservation of mass. The controller calculates the theoretical gas production using current integration and the theoretical exhaust volume using valve opening, thereby deriving the theoretical pressure value and comparing it with the measured absolute pressure value of the system. Compare them.

[0116] Pressure monitoring residual The calculation formula is as follows:

[0117] ;

[0118] in: This represents the absolute value of the residual between the pressure sensor reading and the physical model estimate, expressed in Pascals. Pressure sensors in current The measured absolute pressure value of the system is fed back in real time, in Pascals; Indicates the start time of the verification period The latched initial system pressure value, in Pascals; This represents the ideal gas constant, with a value of 8.314 joules per mole Kelvin; This represents the average temperature monitoring value of the gas phase space inside the gas-liquid separator, in Kelvin. The total physical volume of the gas phase space of the gas-liquid separator on the high-pressure side of the system and the connecting pipeline (i.e., the effective volume participating in the pneumatic buffer) is expressed in cubic meters. This represents the total number of electrolytic cells connected in series in the electrolytic cell stack, and is a dimensionless integer; Indicates the integral variable The instantaneous input current at a given moment, measured in amperes; This represents the current Faraday current efficiency, which is obtained by looking up the efficiency curve stored inside the controller. This represents the Faraday constant, with a value of 96,485 coulombs per mole; Indicates in The theoretical gas discharge flow rate is calculated based on the real-time opening feedback value of the back pressure valve and the valve's inherent flow characteristic curve, and the unit is moles per second.

[0119] If the calculated residual If the error exceeds the allowable tolerance for several consecutive cycles, the controller determines that the data from the physical pressure sensor is unreliable. At this point, the controller triggers a reconfiguration mechanism: it blocks the feedback signal from the physical sensor at the logic layer, switches to a virtual observer control mode that uses the theoretical pressure value calculated from the integral term of the formula as the feedback source, and simultaneously forces the system to switch to Mode B (non-Radidas hot standby state). By stopping electrochemical gas production, the system is maintained in a pressure-holding state with the lowest risk until the fault is reset.

[0120] To eliminate the computational divergence of the virtual observer caused by the accumulation of integral errors, the controller introduces periodic reference correction logic. When the system is in steady-state operation and the voltage and temperature fluctuation rates of each slot are below the preset steady-state threshold, if the residual at this time... Within the allowable range, the controller will force the integrator's initial pressure value. Updated to the current measured pressure value and will The constant zeroing and resetting ensures that the fault diagnosis algorithm is only sensitive to short-term abnormal pressure changes (such as leaks or sensor mutations), while ignoring long-term cumulative calculation errors.

Claims

1. An off-grid alkaline hydrogen production system, characterized in that, include: A renewable energy power supply unit, the output of which is connected to a DC bus; Multiple alkaline electrolyzer modules connected in parallel are connected to the DC bus, and each alkaline electrolyzer module includes an electrolyzer body and a rectifier cabinet; A public gas processing system, which is connected to the alkaline electrolyzer module via a gas manifold, includes a hydrogen-side pipeline, an oxygen-side pipeline, and a main back pressure valve assembly with a hydrogen-side regulating valve and an oxygen-side regulating valve. A circulating fluid system, comprising a circulating pump and a U-shaped connecting pipe between the hydrogen-side pipeline and the oxygen-side pipeline; The main controller is configured to collect power data from the renewable energy power supply unit to generate predicted power, and determine the operating state of the off-grid alkaline hydrogen production system as either Faraday hydrogen production mode or non-Faraday polarization hot standby mode based on the predicted power. When in the Faraday hydrogen production mode, an active impedance adjustment strategy is executed: The main back pressure valve group is controlled to adjust the operating pressure of the off-grid alkaline hydrogen production system. The change in operating pressure modulates the impedance characteristics of the electrolyzer body by compressing the volume of bubbles in the electrolyte, and in conjunction with adjusting the output current of the rectifier cabinet. When in the aforementioned non-Radidatic polarization hot standby mode, an electrochemical polarization and liquid level blocking strategy is executed: The rectifier cabinet is controlled to clamp the output voltage in the non-gas evolution polarization range, and the relative opening of the hydrogen-side regulating valve and the oxygen-side regulating valve is controlled to create a barrier gas-liquid level height difference in the U-shaped connecting pipeline.

2. The off-grid alkaline hydrogen production system according to claim 1, characterized in that, The main controller has a pre-set pressure bubble coupled electrolysis characteristic model, which characterizes the physical mapping relationship between the operating pressure, bubble porosity and electrolyte ohmic resistance of the off-grid alkaline hydrogen production system. When executing the active impedance adjustment strategy, the main controller uses the pressure bubble coupled electrolysis characteristic model to construct a real-time optimization problem with the objective of maximizing the instantaneous hydrogen production of the off-grid alkaline hydrogen production system under the predicted power constraint. The controller then solves and calculates the optimal operating pressure value of the off-grid alkaline hydrogen production system and the current distribution value of each electrolyzer required to compress the bubbles to a preset volume threshold.

3. The off-grid alkaline hydrogen production system according to claim 1, characterized in that, When the main controller executes the electrochemical polarization and liquid level blocking strategy, it is also configured as follows: By outputting voltage control commands to the rectifier cabinet, the voltage applied across the two ends of the electrolytic cell body is clamped in the non-gas evolution polarization range between the polarization maintenance reference voltage and the theoretical decomposition voltage, thus completing the electrical polarization maintenance. By calculating the minimum liquid level height difference required to seal the micropores of the electrolytic cell diaphragm, and based on the principle of hydrostatics, calculating the pressure difference between the hydrogen side and the oxygen side required to establish the minimum liquid level height difference, the opening of the hydrogen side regulating valve and the oxygen side regulating valve are controlled to construct the barrier gas liquid level height difference in the U-shaped connecting pipeline, thus completing the liquid level sealing.

4. The off-grid alkaline hydrogen production system according to claim 3, characterized in that, The main controller is also configured to: In the non-Radida polarization hot standby mode, a speed reduction command is sent to the circulating pump to reduce the flow rate setpoint of the circulating pump to the minimum maintenance flow rate for laminar flow, thereby reducing the disturbance of the barrier gas liquid level height difference in the U-shaped connecting pipe to the fluid turbulence.

5. The off-grid alkaline hydrogen production system according to claim 1, characterized in that, The main controller is also configured to execute a transient buffer control strategy based on aerodynamic capacity: When the predicted power decrease rate is detected to exceed the preset decrease rate threshold, the main back pressure valve group is preferentially instructed to close before reducing the output current of the rectifier cabinet, thus activating the transient buffer control strategy. By calculating the gas emission volume flow command, the main back pressure valve group is controlled to maintain a small and precise opening. The gas dead zone volume in the public gas processing system and connecting pipeline is used as a pneumatic spring to maintain the operating pressure of the off-grid alkaline hydrogen production system according to the preset safety curve, thus completing the transient buffer control strategy.

6. The off-grid alkaline hydrogen production system according to claim 5, characterized in that, The main controller is also configured to monitor the actual rate of change of the operating pressure of the off-grid alkaline hydrogen production system. When the actual rate of change of the operating pressure exceeds the maximum allowable pressure decay rate, the main back pressure valve group opening is corrected by PID control.

7. The off-grid alkaline hydrogen production system according to claim 1, characterized in that, The main controller is also configured to determine the operating state using a dual threshold determination mechanism: Set an opening threshold that is higher than the gas production start-up power threshold, and a closing threshold that is lower than the gas production start-up power threshold; The switch to the Faraday hydrogen production mode is determined only when the predicted power increases and exceeds the activation threshold; Switching to the illegal Radic polarization hot standby mode is determined only when the predicted power decreases and falls below the shutdown threshold.

8. The off-grid alkaline hydrogen production system according to claim 1, characterized in that, The main controller is also configured to perform status parameter acquisition and ultra-short-term power trend prediction. The status parameter acquisition is completed by collecting the historical power data sequence of the renewable energy power supply unit within a fixed time window prior to the current moment; By applying trend prediction logic to process the historical power data sequence, the power change trend sequence in a short future period is calculated, and the predicted power is generated, thus completing the ultra-short-term power trend prediction.

9. The off-grid alkaline hydrogen production system according to claim 1, characterized in that, The main controller is also configured to execute temperature management and mode recovery logic: By monitoring the temperature of the electrolytic cell body in real time, if the temperature is detected to be lower than the preset cold standby temperature threshold during the non-Radida polarization hot standby mode, the voltage setting value is automatically increased, and the temperature is raised by increasing the Joule heating effect to complete the temperature management. When the off-grid alkaline hydrogen production system needs to recover from the non-Faraday polarization hot standby mode to the Faraday hydrogen production mode, the main back pressure valve group is adjusted first to eliminate the set pressure difference between the hydrogen side and the oxygen side. After the liquid level in the U-shaped connecting pipeline is restored to balance, the current is increased to the gas production level to complete the mode recovery logic.

10. A method for adaptive power allocation and safety control of an off-grid alkaline hydrogen production system, characterized in that, The off-grid alkaline hydrogen production system according to any one of claims 1-9 comprises the following steps: S1. Use the main controller to collect the real-time power of the renewable energy power supply unit to form a historical data sequence, and calculate the predicted power within a future preset time period based on the historical data sequence; S2. The main controller compares the predicted power with a preset threshold and locks the off-grid alkaline hydrogen production system into one of the following operating states: Faraday hydrogen production mode, non-Faraday polarization hot standby mode, and shutdown maintenance mode. S3. If the system is in the Faraday hydrogen production mode, the main controller executes an active impedance adjustment strategy, uses the pressure bubble coupled electrolysis characteristic model to calculate and output the optimal operating pressure value and current distribution value of each electrolyzer for the off-grid alkaline hydrogen production system. If the system is in the non-Radidatic polarization hot standby mode, the main controller executes the electrochemical polarization and liquid level blocking strategy, generates a voltage clamping command, and calculates the pressure difference required to establish liquid level blocking to generate a pressure difference blocking command. S4. The main controller will generate instructions and send them to the rectifier cabinet, the main back pressure valve group and the circulating pump. When it detects that the predicted power decrease rate exceeds the preset decrease rate threshold, it will preferentially instruct the main back pressure valve group to move in the closing direction to start the transient buffer control strategy. The gas dead zone volume will be used to maintain the operating pressure of the off-grid alkaline hydrogen production system according to the preset safety curve. S5. The main controller monitors the status of the off-grid alkaline hydrogen production system, performs PID correction on the actual change rate of the operating pressure of the off-grid alkaline hydrogen production system, executes temperature recovery logic, and returns to step S1 in a loop.

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