Multi-modal control PEM electrolytic bath system and method based on liquid level and temperature

Abstract

The invention relates to the technical field of PEM electrolytic bath systems, in particular to a liquid level and temperature-based multi-modal control PEM electrolytic bath system and method, the system comprises a water tank, an electrolytic bath unit, a heat exchange recovery unit and a control unit, and the heat exchange recovery unit comprises a hydrogen side gas intercooler, an oxygen side gas intercooler and a gas-water separator. According to the method, the liquid level sensor judges that the water tank is in an extremely low liquid level, a normal liquid level or a more-water state, and three control modes are correspondingly triggered. The core lies in that in a normal liquid level mode, a control unit calculates the needed system water inlet flow M0 in real time through a heat balance equation according to the target temperature Tt of a water tank, the water inlet temperature T0 and the multi-path return water temperature and flow from a heat exchange recovery unit, the power of a PTC heater is dynamically adjusted, and therefore deep cooperation of liquid level management and temperature control is achieved. Electrolytic reaction waste heat can be recycled to reduce the overall energy consumption of the system, water temperature fluctuation in the water supplementing process is effectively restrained, and stable and efficient operation of the electrolytic bath is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of PEM electrolyzer system technology, and in particular to a PEM electrolyzer system and method based on multimodal control of liquid level and temperature. Background Technology

[0002] PEM electrolyzers are a highly efficient water electrolysis technology for hydrogen production, but traditional systems suffer from the following problems: First, the hydrogen and oxygen produced by the electrolyzer are at high temperatures, easily damaging downstream oxygen-to-hydrogen and hydrogen-to-oxygen sensors and shortening equipment lifespan. Second, the system has high energy consumption; the waste heat generated during electrolysis is not fully recovered, leading to a heavy load on heaters (such as PTC heaters) and low overall efficiency. Finally, large temperature fluctuations occur during water replenishment, affecting the stable operation of the electrolyzer. Existing control methods mostly focus on single-parameter control of temperature or liquid level. Specifically, they control water volume based on tank level (adding water when it's low) or control water volume and temperature based on temperature sensors, without considering temperature fluctuations during water replenishment. The actual water volume and temperature are coupled. Single-parameter control lacks collaborative optimization and is difficult to achieve adaptive adjustment.

[0003] Therefore, there is an urgent need to improve the existing single-parameter control method so as to integrate the coordinated control of liquid level and temperature parameters and achieve energy efficiency improvement and stable operation through multi-modal control. Summary of the Invention

[0004] The purpose of this invention is to provide an improvement to existing single-parameter control methods, enabling the integrated control of liquid level and temperature parameters, and achieving energy efficiency improvement and stable operation through multimodal control.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a PEM electrolyzer system and method based on multimodal control of liquid level and temperature, comprising a water tank equipped with a PTC heater, an electrolyzer unit for electrolyzing water to generate hydrogen and oxygen, a heat exchange and recovery unit connected to the electrolyzer unit, and a control unit; the electrolyzer unit includes an electrolyzer connected to a water pump, and the electrolyzer includes an oxygen side and a hydrogen side; The heat exchange and recovery unit includes a hydrogen-side gas intercooler, an oxygen-side gas intercooler, and a gas-water separator, used to cool the wet and hot gas generated by electrolysis and recover waste heat; the gas-water separator includes an oxygen-side primary gas-water separator, an oxygen-side secondary gas-water separator, and a hydrogen-side gas-water separator. The oxygen side of the electrolyzer is sequentially equipped with an oxygen-side primary gas-water separator, an oxygen-side gas intercooler, and an oxygen-side secondary gas-water separator; the hydrogen side of the electrolyzer is sequentially connected to a hydrogen-side gas intercooler and a hydrogen-side gas-water separator. It also includes temperature sensors T0, T1, T2, T3, T4, T5, T6, T7 respectively arranged at the water inlet of the water tank, the oxygen outlet of the oxygen-side secondary gas-water separator, the hydrogen outlet of the hydrogen-side gas-water separator, inside the water tank, the water inlet of the electrolyzer, the return water inlet of the hydrogen-side gas intercooler, the return water inlet of the oxygen-side gas intercooler, and the oxygen-side gas-water separator; flow sensors M0 arranged at the water tank inlet, flow sensor M1 at the inlet of the hydrogen-side gas intercooler, flow sensor M2 at the oxygen-side gas intercooler, and flow sensor M3 at the return water inlet of the oxygen-side gas-water separator; A liquid level sensor for outputting multiple liquid level signals is also provided in the water tank.

[0006] Preferably, the hydrogen-side gas intercooler and the oxygen-side gas intercooler are respectively connected to the gas circuits on the hydrogen side and the oxygen side of the electrolyzer, and the water inlets of the hydrogen-side gas intercooler and the oxygen-side gas intercooler are both connected to the water tank; The radiator is located between the water pump and the electrolyzer and is used to pre-cool the water entering the electrolyzer; the external normal temperature water enters the water tank after deionization treatment, the temperature is denoted as T0, and the flow rate is denoted as M0.

[0007] Preferably, the control unit executes a multi-modal control strategy, including Mode 1, Mode 2 and Mode 3; Mode 1: When the liquid level sensor detects that the liquid level L is lower than the lowest threshold LL (L < LL), turn off the PTC heater and replenish water to the water tank at the maximum water inlet flow rate M0 max ; Mode 2: When the liquid level L is at the normal liquid level (LL ≤ L < LH), dynamically adjust the power of the PTC heater and the water inlet flow rate M0 according to the difference between the water tank temperature T3 and the set target temperature Tt, where the water inlet flow rate M0 is calculated by the heat balance equation; Mode 3: When the liquid level L is higher than the high threshold LH (L ≥ LH), turn off the water inlet flow rate M0, and adjust the power of the PTC heater and the power of the radiator according to the water tank temperature T3 and the target temperature Tt.

[0008] A control method for a PEM electrolyzer based on multi-modal intelligent control of liquid level and temperature, which obtains in real time the liquid level signal L of the liquid level sensor, the water tank temperature T3, the target temperature Tt, the water inlet temperature T0 of the water tank, and the temperature and flow rate signals of multiple return water routes in the heat exchange recovery unit; Judge the current liquid level state and liquid level trend according to the liquid level signal L; the liquid level state includes the multi-water state, the normal liquid level and the extremely low liquid level; Select the corresponding control mode based on the liquid level state: the control modes include Mode 1, Mode 2 and Mode 3; If L < LL, indicating an extremely low liquid level, execute mode one: shut down the PTC heater and operate at the maximum inlet flow rate M0. max Hydration; M0 max The flow rate at maximum water supply pump speed; If LL≤L<LH represents the normal liquid level, then execute mode two: Based on the temperature difference between the water tank temperature T3 and the target temperature Tt, dynamically adjust the PTC heater power and the inlet water flow rate M0. The inlet water flow rate M0 is determined by M0=M0 cal +M' confirms, M0 cal M0 is the theoretical flow rate, M' is the trend-corrected flow rate derived from the liquid level trend assessment, and M' is the theoretical flow rate. cal Calculated using the heat balance equation: ; If the water level is high (L≥LH), execute mode 3: shut off the inlet flow rate M0, and adjust the power of the PTC heater and the radiator according to the water tank temperature T3 and the target temperature Tt. Based on the selected mode, output control commands for the PTC heater power and inlet water flow rate M0.

[0009] Preferably, the step of determining the current liquid level status based on the liquid level signal L specifically includes: receiving the gear signal from the liquid level sensor, determining that no gear is triggered as an extremely low liquid level, determining that the triggered high liquid level LH ​​gear is a state of excess water, and determining that the triggered low liquid level LL, low liquid level LML, medium liquid level LM, and medium high liquid level LHM gears are normal liquid levels. The liquid level trend judgment includes: comparing the current liquid level with the liquid level in the previous control cycle; if the liquid level rises, then the theoretical flow rate M0 calculated from the heat balance equation is... cal A negative correction flow rate is added; if the liquid level drops, a positive correction flow rate is added.

[0010] Preferably, in Mode 2, when T3 is T3 > Tt + 10℃, indicating a severely overheated temperature, the PTC heater is forcibly shut down, and the radiator is simultaneously activated with its power set to 100%. When T3 is at Tt+ΔT<T3≤Tt+10℃, the temperature is slightly too high. In this case, the PTC heater power is turned off, the radiator power is adjusted according to the table based on temperature T3, and the inlet water flow rate M0 is set to M0. min M0 min The flow rate at the minimum operating speed of the water supply pump; The optimal range is when T3 is within the range of Tt-ΔT<T3≤Tt+ΔT. The theoretical flow rate M0 can be calculated using the heat balance equation. cal By superimposing the trend-corrected flow rate M', we obtain the influent flow rate M0 = M0 cal+M'; If M' is positive, then the PTC needs to be turned on appropriately, and the PTC heater power is C. (Tt-T0) M'; if M' is negative, then the heatsink needs to be turned on, and the heatsink power is C. (Tt-T0) M'; where C is the specific heat capacity of water; When T3 is within Tt-10℃<T3≤Tt-ΔT, the temperature is slightly low. Keep the PTC heater on and set the inlet water flow rate M0 to M0. min ; When the water temperature T3 is significantly too low (T3 < Tt-10℃), the PTC heater is turned on to 100%, and the inlet water flow rate M0 is set to M0. min ; Among them, Tt is generally set to 60±5℃, and the preset temperature deviation threshold ΔT is set to 3~5℃ according to the actual situation.

[0011] Preferably, the liquid level status is determined by multiple level signals output by the liquid level sensor, including high liquid level LH, medium-high liquid level LHM, medium liquid level LM, medium-low liquid level LML, and low liquid level LL; the liquid level change trend is obtained by comparing the current liquid level status with the status of the previous cycle.

[0012] Preferably, in Mode 3, when T3 is T3 > Tt + 10℃, indicating a severely overheated temperature, an overheating warning is issued, the PTC heater power is turned off, and the radiator is started with its power at 100%. When T3 is at Tt+ΔT<T3≤Tt+10℃, the temperature is slightly too high. In this case, the PTC heater power is turned off and the radiator is turned on. When T3 is in the optimal range of Tt-ΔT<T3≤Tt+ΔT, the PTC heater is turned off and the inlet water flow rate M0 is turned off. When T3 is at Tt-10℃<T3≤Tt-ΔT, the temperature is slightly low. Turn off the inlet water flow M0 and turn on the PTC heater. When T3 is below Tt-10℃, indicating a severely low temperature, the inlet water flow rate M0 should be turned off, and the PTC heater power should be turned on at 100%. Where Tt is the target operating temperature of the electrolytic cell 4 system, which is generally set to 60±5℃; ΔT is the preset temperature deviation threshold, which is set to 3~5℃ according to the actual situation.

[0013] Preferably, the method is applicable to distributed hydrogen production systems, used to improve cold start speed, reduce system energy consumption, protect back-end sensors, and maintain stable operating temperature.

[0014] Compared with the prior art, the advantages and positive effects of the present invention are as follows: Under the traditional control method, a large amount of waste heat generated by the electrolysis reaction is often directly dissipated through the radiator, and the water replenishment heating completely depends on an additional PTC heater, resulting in low energy utilization efficiency. In the present invention, the liquid level state (extremely low, normal, excessive water) is used as the multi-modal control condition. In the normal liquid level mode, the temperature and flow rate of the multi-channel return water (M1, M2, M3) of the heat exchange recovery unit are collected in real time, and the theoretical water replenishment flow rate M0 is dynamically calculated based on the heat balance equation cal , so that the heat required for the supplementary normal temperature water (T0) is exactly provided by the waste heat of the system. Further, a feed-forward correction amount M' of the liquid level change trend is introduced to compensate in advance for the influence of the water volume change on the temperature. The algorithm M0 based on the heat balance cal =[M3 (T7 - Tt) + M1 (T5 - Tt) + M2 (T6 - Tt)] / (Tt - T0), and the system inlet water flow rate M0 is dynamically adjusted in combination with the liquid level trend, M0 = M0 cal + M'. This enables the recovery of low-grade heat energy in the humid and hot gas at the rear end of the electrolyzer for preheating the supplementary normal temperature water. Practice shows that this is beneficial to reducing the energy consumption of the PTC heater and the radiator during steady-state operation, and effectively shortening the time required for the cold start of the equipment

[0015] The hydrogen and oxygen produced by the PEM electrolyzer have high humidity and temperature. Direct discharge is likely to damage the precise hydrogen-in-oxygen and oxygen-in-hydrogen sensors at the rear end and shorten their service life. Through a mandatory gas cooling process (heat exchange through an intercooler), the present invention can stably reduce the outlet gas temperature below the dew point, achieve efficient gas-water separation, and thus control the humidity of the output gas within a safe range. In addition, based on the control strategy divided by the liquid level multi-modal, it has the highest priority when the liquid level is extremely low (L < LL), can immediately cut off the heating and replenish water at the maximum flow rate, fundamentally eliminating the risk of dry burning of the electrolyzer. This dual temperature and liquid level safety protection is beneficial to extending the service life of the sensors and improving the long-term operation reliability of the system

[0016] Traditional single-parameter (only liquid level or only temperature) control methods are difficult to avoid causing drastic fluctuations in the water tank temperature during water replenishment, thereby affecting the stability and efficiency of the electrolysis reaction. The multi-modal collaborative control strategy proposed in the present invention uses the liquid level state (extremely low, normal, excessive water) as the top-level logic for switching control modes, and in the core "normal liquid level" mode, deeply integrates real-time heat balance calculation and feed-forward correction of the liquid level change trend. This enables the system to not only perceive the water volume change trend in advance and make flow compensation, but also accurately calculate the minimum (or optimal) water replenishment volume required to maintain the target temperature, thus achieving on-demand, precise, and gentle water replenishment. As Figure 5 shown in Figure 6 , compared with the traditional method ( Figure 4Compared to other methods, this invention helps to eliminate periodic large temperature fluctuations and stabilizes the water tank temperature within the optimal range of ±ΔT, providing a highly stable environment for the electrolytic cell. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the PEM electrolyzer system based on multimodal intelligent control of liquid level and temperature according to the present invention. Figure 2 The flowchart shows the PEM electrolyzer control method based on multimodal intelligent control of liquid level and temperature according to the present invention. Figure 3 This is a lookup table for the PTC heater power and radiator power corresponding to the water tank temperature in this invention; Figure 4 This is a schematic diagram showing the temperature fluctuation of the water tank over time when using the traditional single-parameter control method. Figure 5 This is a schematic diagram illustrating the optimization effect of the water tank temperature fluctuation over time after adopting the multimodal control method described in this invention. Figure 6 This is a schematic diagram showing the change of system influent flow rate M0 over time after adopting the multimodal control method described in this invention; Explanation of reference numerals in the attached diagram: 1. Water tank; 2. Water pump; 3. Radiator; 4. Electrolyzer; 5. Oxygen-side primary gas-water separator; 6. Oxygen-side gas intercooler; 7. Oxygen-side secondary gas-water separator; 8. Hydrogen-side gas intercooler; 9. Hydrogen-side gas-water separator; T0: External inlet water temperature / water tank inlet temperature; T1: Oxygen outlet temperature (outlet of oxygen-side secondary gas-water separator); T2: Hydrogen outlet temperature (outlet of hydrogen-side gas-water separator); T3: Water temperature inside the water tank; T4: Electrolyzer inlet temperature; T5: Hydrogen-side gas intercooler return water temperature; T6: Oxygen-side gas intercooler return water temperature; T7: Total return water temperature of oxygen-side gas-water separators (primary and secondary); M0: System inlet water flow rate; M1: Hydrogen-side gas intercooler inlet water flow rate; M2: Oxygen-side gas intercooler inlet water flow rate; M3: Total return water flow rate of oxygen-side gas-water separator; P0: System inlet water pressure (optional); LH, LHM, LM, LML, LL: Liquid level sensor range signals (corresponding to high, medium-high, medium, medium-low, and low liquid levels, respectively). Detailed Implementation

[0018] This invention provides a PEM electrolyzer system and control method. Through a multi-modal intelligent control strategy for liquid level and temperature, it solves the problems in the prior art of PEM electrolyzer systems, such as excessive humidity of hydrogen and oxygen outlet gases damaging sensors (dew point temperature at 100% humidity is the same as temperature), high system energy consumption, and water temperature fluctuations during water replenishment affecting the stable operation of the electrolyzer.

[0019] This invention relates to a PEM electrolyzer system based on multimodal control of liquid level and temperature, comprising: an electrolyzer unit, a heat exchange and recovery unit, and a control unit. The control unit monitors liquid level and temperature parameters in real time, and adaptively selects different control modes (mode one, mode two, and mode three) according to the liquid level status (e.g., high water, normal, extremely low) and trend (rising / falling / stable), adjusting the inlet water flow rate M0 and the PTC heater power to maximize the utilization of waste heat and maintain temperature stability. Figure 1 This is a flow chart of the PEM electrolyzer system of the present invention, illustrating the entire process from water intake to the production of hydrogen and oxygen, including components such as water tank 1, water pump 2, electrolyzer 4, heat exchanger, and separator. Figure 1 As shown, the PEM electrolyzer 4 system mainly includes a water tank 1, a water pump 2, a plate heat exchanger 3 for electrolyzer 4, an electrolyzer 4, an oxygen-side primary gas-water separator 5, an oxygen-side gas intercooler 6, an oxygen-side secondary gas-water separator 7, a hydrogen-side gas intercooler 8, and a hydrogen-side gas-water separator 9. Key parameters are labeled as follows: T0 (inlet water temperature), T1 (oxygen outlet temperature), T2 (hydrogen outlet temperature), T3 (water tank 1 temperature), T4 (electrolyzer 4 temperature), T5 (return water temperature of hydrogen-side gas intercooler 8), T6 (return water temperature of oxygen-side gas intercooler 6), T7 (return water temperature of oxygen-side separator), M0 (inlet water flow rate), M1 (inlet water flow rate of hydrogen-side gas intercooler 8), M2 (inlet water flow rate of oxygen-side gas intercooler 6), and M3 (return water flow rate of oxygen-side separator, the sum of the return water flow rates of the oxygen-side primary gas-water separator 5 and the oxygen-side secondary gas-water separator 7). Water tank 1 is equipped with a PTC heater for heating the incoming water; external ambient temperature water flows into water tank 1 after deionization treatment (temperature T0, flow rate M0, pressure P0). Water pump 2 sends the water flowing out of water tank 1 to radiator 3 for preheating, and then enters electrolysis cell 4 for electrolysis. The hydrogen produced by electrolysis is cooled by hydrogen-side gas intercooler 8 (using ambient temperature water for heat exchange) and then separated and output (temperatures T2, T6, T7, flow rates M2, M3), while oxygen is output through oxygen-side separator (temperature T1). Key temperature and flow rate points include the inlet water temperature T0 of water tank 1, the oxygen outlet temperature T1 of the oxygen-side secondary gas-water separator 7, the hydrogen outlet temperature T2 of the hydrogen-side gas-water separator 9, the water tank temperature T3, the inlet water temperature T4 of electrolyzer 4, the return water temperature T5 of the hydrogen-side gas intercooler 8, the return water temperature T6 of the oxygen-side gas intercooler 6, the return water temperature T7 of the oxygen-side separator, the inlet water flow rate M0 of water tank 1, the inlet water flow rate M1 of the hydrogen-side gas intercooler 8, the inlet water flow rate M2 of the oxygen-side gas intercooler 6, and the return water flow rate M3 of the oxygen-side separator, used for control feedback. In addition, Tt is the target operating temperature for the electrolyzer 4 system, typically set to 60±5℃.

[0020] System workflow: 1) Electrolytic cell unit: External ambient temperature water (temperature T0) that has undergone deionization treatment flows into water tank 1 with heater (PTC) through a valve, and is then pumped by water pump 2 to radiator 3 of electrolytic cell 4 (using external cold water for heat exchange) to control the temperature of electrolytic cell 4 and prevent overheating before entering electrolytic cell 4 for electrolysis.

[0021] 2) Heat exchange and recovery unit: The wet hot hydrogen and oxygen generated by electrolysis of electrolytic cell 4 pass through the gas intercooler and gas-water separator respectively, and the water after heat exchange is returned to the system.

[0022] 3) Control unit: Through real-time data from sensors (such as temperature T0-T6, flow rate M0-M2, pressure P0), it performs liquid level judgment and multi-modal control, and outputs PTC heater power and inlet water flow rate M0.

[0023] Figure 2 This is the control flowchart of the present invention, including a liquid level status, a liquid level trend judgment module, and a multi-modal control module, demonstrating the status judgment and mode selection mechanism based on the liquid level signals (LH, LHM, LM, LML, LL) from five liquid level sensors in water tank 1. Figure 2 As shown, the control unit, with a microprocessor at its core, executes the following steps: System initialization and operation: During startup, system initialization and sensor self-tests (such as temperature and level sensors) are performed. The initial PTC heater power and inlet water flow rate M0 are set. Since the initial water temperature T3 in tank 1 is room temperature, the initial PTC heater power needs to be set to 100% to rapidly heat to the ideal temperature. Because the water level in tank 1 is at the normal level during initial operation, the initial inlet water flow rate M0 can be referenced from the inlet water flow rate in Mode 2, and is set to M0. min .

[0024] Real-time parameter reading: Each control cycle reads the liquid level signal (LH, LHM, LM, LML, LL, etc., switch signals) and temperature parameters (T3, Tt, T0, etc.). The liquid level sensor has five levels: high (LH), medium-high (LHM), medium (LM), medium-low (LML), and low (LL). LH, LHM, LM, LML, and LL correspond to the liquid level sensors at five positions in water tank 1, specifically at 90%, 70%, 50%, 30%, and 10% of the tank's water level, respectively, and can also be fine-tuned. (Reference) Figure 1Five level sensors are installed in water tank 1 from top to bottom, corresponding to the level signals LH, LHM, LM, LML, and LL. When the liquid level L reaches the position of a certain level sensor, that level sensor is activated. If the liquid level L is below LL, it is considered an extremely low liquid level. At this time, because the liquid level L is lower than the lowest level sensor LL, all level sensors are not activated; that is, the state where all level sensors are not activated is considered an extremely low liquid level. If the liquid level L is between LM and LHM, then LM... All level sensors at and below will be set. In actual water tank 1, this means the level sensors at LL, LML, and LM will all be lit and set, while the level sensors at LHM and LH will not be set. This is considered a normal level. Similarly, when all level sensors are lit and set, it indicates a high water level (L≥LH). When all level sensors are off and not set, it indicates an extremely low level (L<LL). Other states are normal levels (LL≤L<LH), corresponding to Mode 3, Mode 1, and Mode 2 in the control strategy, respectively. Low level (LL) is set to 10% to avoid dry burning; low level (LML) is set to 30%; medium level (LM) is set to 50%; medium-high level (LHM) is set to 70%; high level (LH) is set to 90% to avoid overflow. When the water level is above 90%, it is considered a high water level; when the water level is below 10%, it is considered an extremely low level. The inlet flow rate is M0. max It is actually controlled by the front-end water supply pump; set to M0. max This is actually equivalent to the flow rate at maximum water supply pump speed; M0 min This is equivalent to the flow rate at the minimum operating speed of the water supply pump. The control mode is adaptively selected based on the liquid level status and trend observed by the level sensor, adjusting the inlet flow rate M0 of water tank 1 and the power of the PTC heater.

[0025] Liquid Level Status and Trend Judgment: Five switch signals are input (LH represents high liquid level, LHM represents medium-high liquid level, LM represents medium liquid level, LML represents medium-low liquid level, and LL represents low liquid level). The system receives level signals from the liquid level sensor. Any level not triggered is judged as extremely low liquid level; triggering the high liquid level LH ​​level is judged as a high water level; triggering the medium-low liquid level LML, medium liquid level LM, or medium-high liquid level LHM level is judged as a normal liquid level. The liquid level is determined based on the output liquid level status (e.g., LH trigger = "high water level", LHM trigger = "normally high", LM trigger = "normally ideal", LML trigger = "normally low", and only LL not triggered = "extremely low"). Combined with the status from the previous cycle, the liquid level trend (rising, falling, or stable) is determined. The trend (rising, falling, stable) judgment is only used for control in mode two. Five level sensors are set according to the range of 90%-70%-50%-30%-10%. The trend variable is considered to be the time it takes for the water volume to exceed the level of adjacent sensors. For example, if the time taken to go from 50% to 70% is 10 seconds, it is considered that the current water volume has exceeded the normal range to a higher range. At this time, based on the total water volume V in the tank, it can be calculated that the water volume in the tank increased by 0.2V within 10 seconds. Therefore, the rate of increase in water volume during this period is 0.2V / 10s = 0.02V / s. This volumetric flow rate is used as the trend correction flow rate M' for the next stage of control. Therefore, after exceeding 70% from 50% in 10 seconds, the trend correction flow rate M' of the inflow M0 is increased by -0.02V / s. The current liquid level state is compared with the liquid level state of the previous control cycle. If the liquid level rises, the theoretical flow rate M0 calculated from the heat balance equation is used. cal A negative correction flow rate is superimposed if the liquid level drops; if the liquid level drops, a positive correction flow rate is superimposed. The liquid level status judgment is for temperature control, while the added trend flow rate variable is for liquid level control, so that it can be maintained at the normal liquid level for a longer period of time under normal temperature.

[0026] Multimodal control: First, a liquid level safety judgment is performed (L < LL?). If L < LL, then control is performed using mode one (safety priority), forcibly shutting down the PTC heater, while simultaneously setting M0 = M0. max Maximum flow rate is used for emergency water replenishment to prevent electrolytic cell 4 from drying out; this mode has the highest priority. If L ≥ LL, the next step is to determine the liquid level status. If the water level in tank 1 is at the normal level (LL ≤ L < LH), control is implemented using mode two (normal level - energy efficiency and temperature coordination). If the water level in tank 1 is in a state of excess water (L ≥ LH), control is implemented using mode three (excess water state - thermal balance priority). In modes one, two, and three, different adjustment strategies are applied based on the water temperature T3.

[0027] When the water level in tank 1 is at the normal level (LL≤L<LH) and in start-up mode two, if the temperature T3 is significantly too high (T3>Tt+10℃), the PTC heater will be forcibly shut down, and radiator 3 will be started simultaneously. Radiator 3 will operate at 100% power for rapid cooling. Radiator 3 can use external cooling water for heat exchange or fan heat exchange; no specific requirements apply. The control strategy is based on PID control according to the target water temperature. Radiator 3 is a plate heat exchanger. ΔT is a preset temperature deviation threshold, set between 3 and 5℃ according to actual conditions. If the temperature T3 is slightly too high (Tt+ΔT<T3≤Tt+10℃), the PTC heater power will be shut down, and the radiator 3 power will be adjusted according to the T3 temperature using a table. The inlet water flow rate M0 is set to M0. min With M0 min Water is introduced. When temperature T3 is within the optimal range (Tt-ΔT<T3≤Tt+ΔT), the theoretical flow rate M0 is calculated using the heat balance equation. cal By superimposing the trend-corrected flow rate M', we obtain the influent flow rate M0 = M0 cal +M'; If M' is positive, then the PTC needs to be turned on appropriately, and the PTC heater power is C. (Tt-T0) M'; if M' is negative, then radiator 3 needs to be turned on appropriately, and the power of radiator 3 is C. (Tt-T0) M'; Fully utilize the waste heat from the reaction for heating to achieve optimal energy efficiency, pursuing optimal energy efficiency based on dynamic adjustment of thermal balance. When the water temperature T3 is slightly low (Tt-10℃<T3≤Tt-ΔT), keep the PTC heater on. The PTC heater power is determined by referring to a table based on the T3 temperature, and maintain the inlet water flow rate at M0. min Slowly introduce water. When the water temperature T3 is significantly lower (T3 < Tt-10℃), prioritize the simultaneous activation of the PTC heater at M0. min Water inlet, PTC heater power output 100%; the following is the calculation method for the water inlet flow rate M0 within the optimal temperature range (Tt-ΔT<T3≤Tt+ΔT): Q = Return water heat power Q1 + Waste heat recovery heat power Q2; C M0 cal ΔT=C M 回水 ΔT 回水 +C M 余热回收 ΔT 余热回收 ; M0 cal (Tt-T0)=M3 (T7-Tt)+M1 (T5-Tt)+M2 (T6-Tt); M0 cal =[M3 (T7-Tt)+M1 (T5-Tt)+M2 [(T6-Tt)] / (Tt-T0); M0=M0 cal +M'; In the formula, C represents the specific heat capacity of water. The total heat required to heat the ambient temperature makeup water (temperature T0) entering water tank 1 to the system set temperature Tt should be equal to the sum of the waste heat carried by the three return water streams inside the system (from the oxygen-side primary gas-water separator 5, the oxygen-side secondary gas-water separator 7, the hydrogen-side gas intercooler 8, and the oxygen-side gas intercooler 6, respectively). The theoretical flow rate M0 is dynamically calculated using the heat balance equation. cal This allows for maximizing the use of waste heat and minimizing the additional energy consumption of the PTC heater while meeting water temperature requirements.

[0028] If the water level in tank 1 is in a high-water state (L≥LH), control will be implemented using mode 3 (high-water state - thermal balance priority), while simultaneously performing precise water temperature (T3 vs Tt) checks. If water temperature T3 is significantly too high (T3>Tt+10℃), the PTC heater power will be shut off, an overheat alarm will be triggered, and radiator 3 will be activated at 100% power. If water temperature T3 is slightly too high (Tt+ΔT<T3≤Tt+10℃), the PTC heater will be shut off, the inlet flow rate M0 will be turned off, and radiator 3 will be activated, with its power adjusted according to the T3 temperature. If water temperature T3 is within the optimal range (Tt-ΔT<T3≤Tt+ΔT), the PTC heater will be shut off, and the inlet flow rate M0 will be turned off. If water temperature T3 is slightly too low (Tt-10℃<T3≤Tt-ΔT), the inlet flow rate M0 will be turned off, and the PTC heater power will be adjusted according to the T3 temperature. When the water temperature T3 is significantly too low (T3 < Tt-10℃), the inlet water flow rate M0 is turned off and the PTC heater power is turned on at 100%. Figure 3 This is a lookup table for the PTC heater power and radiator 3 power corresponding to water tank temperature T3 in this invention; the power corresponding to some temperatures is shown in Table 1: Table 1:

[0029] Finally, perform actuator operation: adjust the PTC heater power, inlet water flow rate M0, and radiator 3 power according to the selected mode.

[0030] Control unit: The control cycle is based on the current PLC control cycle and only needs to be 100ms; the control algorithm is PID control based on the target temperature and the target power of the PTC heater. M0 max M0 min The calibration values ​​can all be determined based on the actual selection results. The control unit is used to execute a multi-modal control strategy based on the signals from the liquid level sensor and the multiple temperature sensors to adjust the power of the PTC heater, the inlet water flow rate M0, and the power of the radiator 3.

[0031] Data update and cycle: The data is updated at the end of each cycle and awaits the next cycle.

[0032] Figure 4 The graph shows the real-time temperature change curve of the water tank when the method of the present invention is not used. It can be seen from the graph that the water tank temperature will drop significantly when water is added, and will remain lower than the target temperature during the water replenishment process. After the water replenishment is completed, the water temperature will return to the target temperature under the action of the heater. The heater needs to be turned on continuously during the water replenishment process. Figure 5 The real-time temperature change curve of the water tank when using the method of the present invention is shown. Based on the real-time calculated water inflow, water is replenished in real time during the stable operation of the electrolytic cell, avoiding temperature fluctuations caused by a large amount of water replenishment when the water tank level drops for a short time. This effectively utilizes the waste heat of the reaction, reduces system energy consumption, and eliminates the need to turn on the radiator and heater. Figure 6 This is a graph showing the real-time water replenishment flow rate change of the water tank when using the method of the present invention.

[0033] This invention achieves intelligent coordinated control of liquid level and temperature by dividing the control mode according to the liquid level state and combining it with heat balance calculation. The system structurally integrates a water tank with a PTC heater, an electrolysis cell unit, and a heat exchange and recovery unit including a hydrogen / oxygen side gas intercooler and a multi-stage gas-water separator. It is also equipped with a complete network of temperature, flow, and liquid level sensors covering the inlet, outlet, water tank, and gas outlet. The method proposes three control modes: Mode 1, prioritizing safety at extremely low liquid levels, involves full water replenishment and shutdown of heating; Mode 2, prioritizing energy efficiency at normal liquid levels, dynamically calculates the optimal inlet flow rate based on the established heat balance equation and supplements it with feedforward correction based on liquid level change trends, thereby precisely maintaining the water tank temperature within the set range while maximizing the utilization of waste heat from the electrolysis reaction and minimizing PTC heater energy consumption; and Mode 3, prioritizing heat balance in a high-water state, operates with the minimum maintenance flow rate and finely adjusts the PTC heater power to stabilize the temperature. This invention effectively solves the problems of large water temperature fluctuations, high energy consumption, waste heat, and easy damage to back-end sensors under traditional single-parameter control. It is beneficial to improve the operating efficiency, stability, and reliability of PEM electrolyzer systems and is particularly suitable for applications such as distributed hydrogen production.

Claims

1. A PEM electrolyzer system based on multi-modal control of liquid level and temperature, characterized by: The application relates to a PEM electrolyzer system based on liquid level and temperature multi-modal control, which comprises a water tank (1) equipped with a PTC heater, an electrolyzer unit for electrolyzing water to generate hydrogen and oxygen, a heat exchange recovery unit connected with the electrolyzer unit and a control unit; the electrolyzer unit comprises an electrolyzer (4) communicated with a water pump (2), and the electrolyzer (4) comprises an oxygen side and a hydrogen side; The heat exchange recovery unit comprises a hydrogen side gas intercooler (8), an oxygen side gas intercooler (6) and a gas-water separator for cooling and waste heat recovery of wet hot gas generated by electrolysis; the gas-water separator comprises an oxygen side first-stage gas-water separator (5), an oxygen side second-stage gas-water separator (7) and a hydrogen side gas-water separator (9), the oxygen side of the electrolyzer (4) is sequentially provided with the oxygen side first-stage gas-water separator (5), the oxygen side gas intercooler (6) and the oxygen side second-stage gas-water separator (7); the hydrogen side of the electrolyzer (4) is sequentially connected with the hydrogen side gas intercooler (8) and the hydrogen side gas-water separator (9); The application further comprises temperature sensors T0, T1, T2, T3, T4, T5, T6 and T7 arranged at a water inlet of the water tank (1), an oxygen gas outlet of the oxygen side second-stage gas-water separator (7), a hydrogen gas outlet of the hydrogen side gas-water separator (9), the water tank (1), a water inlet of the electrolyzer (4), a water return port of the hydrogen side gas intercooler (8), a water return port of the oxygen side gas intercooler (6) and the oxygen side gas-water separator; a flow sensor M0 arranged at the water inlet of the water tank (1), a flow sensor M1 arranged at the inlet of the hydrogen side gas intercooler (8), a flow sensor M2 arranged at the oxygen side gas intercooler (6) and a flow sensor M3 arranged at the water return port of the oxygen side gas-water separator; The water tank (1) is further provided with liquid level sensors for outputting a plurality of liquid level signals.

2. The PEM electrolyzer system based on liquid level and temperature multi-modal control according to claim 1, wherein: The hydrogen side gas intercooler (8) and the oxygen side gas intercooler (6) are respectively connected with the gas paths of the hydrogen side and the oxygen side of the electrolyzer (4), and the water inlets of the hydrogen side gas intercooler (8) and the oxygen side gas intercooler (6) are connected with the water tank (1); The radiator (3) is located between the water pump (2) and the electrolyzer (4) and is used for pre-cooling water entering the electrolyzer (4); external normal-temperature water enters the water tank (1) after being treated by deionization, and the temperature is recorded as T0 and the flow is recorded as M0.

3. The liquid level and temperature based multi-modal controlled PEM electrolyzer system of claim 1, wherein: The control unit executes a multi-modal control strategy, which comprises mode one, mode two and mode three; Mode one: when the liquid level sensor detects that the liquid level L is lower than the minimum threshold LL (L < LL), turn off the PTC heater and use the maximum water inflow M0 max Water is supplied to the water tank (1); Mode two: when the liquid level L is in a normal liquid level (LL<=L Mode three: when the liquid level L is higher than a high threshold LH (L>=LH), the water inflow M0 is closed, and the power of the PTC heater and the power of the radiator (3) are adjusted according to the water tank (1) temperature T3 and the target temperature Tt.

4. A PEM electrolyzer control method based on multi-modal intelligent control of liquid level and temperature, characterized by: Real-time acquisition of liquid level sensor liquid level signal L, water tank (1) temperature T3, target temperature Tt, water tank (1) inlet temperature T0, and temperature and flow signals of multiple return water routes in the heat recovery unit; Determine the current liquid level state and liquid level trend according to the liquid level signal L; the liquid level state includes multiple water state, normal liquid level and extremely low liquid level; Select the corresponding control mode based on the liquid level state: the control mode includes mode one, mode two and mode three; If L < LL is a very low liquid level, execute mode one: turn off PTC heater and run at maximum water inlet flow M0 max Water replenishment; M0 max M0 is the flow at maximum pump speed. If LL≤L<LH is normal liquid level, mode two is executed: according to the temperature difference between the water tank (1) temperature T3 and the target temperature Tt, the PTC heater power and the water inflow M0 are dynamically adjusted, the water inflow M0 is determined by M0=M0 cal +M' cal Theoretical flow M0 cal Through the heat balance equation: ； If it is a multiple water state (L≥LH), mode three is executed: the water inlet flow M0 is closed, and the power of the PTC heater and the power of the radiator (3) are adjusted according to the water tank (1) temperature T3 and the target temperature Tt; According to the selected mode, output control instructions for PTC heater power and water inlet flow M0.

5. The PEM electrolyzer control method based on liquid level and temperature multi-modal intelligent control according to claim 4, characterized in that: The determination of the current liquid level state according to the liquid level signal L specifically includes: receiving the gear signal from the liquid level sensor, judging the extremely low liquid level as not triggering any gear, judging the multiple water state as triggering the high liquid level LH gear, and judging the normal liquid level as triggering the low liquid level LL, the low-middle liquid level LML, the middle liquid level LM, and the high-middle liquid level LHM gears; The liquid level trend judgment comprises: comparing the current liquid level state with the liquid level state of the last control cycle, if the liquid level rises, a negative correction flow is superimposed on the theoretical flow M0 calculated by the heat balance equation cal If the liquid level falls, a positive correction flow is superimposed.

6. The PEM electrolyzer control method based on liquid level and temperature multi-modal intelligent control according to claim 4, characterized in that: In mode two, when T3 is in T3>Tt+10℃, it is a serious temperature overhigh, the PTC heater is forced to be closed, and the radiator (3) is started with the power opened to 100%; When T3 is Tt+ΔT < T3≤Tt+10℃, which is slightly high temperature, the PTC heater power is turned off, the radiator (3) power is adjusted according to the T3 temperature table, and the water inlet flow M0 is set as M0 min ; M0 min is the flow at the minimum running speed of the water supplement pump. The optimal range is when T3 is within the range of Tt-ΔT<T3≤Tt+ΔT. The theoretical flow rate M0 can be calculated using the heat balance equation. cal By superimposing the trend-corrected flow rate M', we obtain the influent flow rate M0 = M0 cal +M'; If M' is positive, then the PTC needs to be turned on appropriately, and the PTC heater power is C. (Tt-T0) M'; if M' is negative, then radiator 3 needs to be turned on, and the power of radiator 3 is C. (Tt-T0) M'; where C is the specific heat capacity of water; When T3 is Tt-10℃ < T3≤ Tt-ΔT, the temperature is slightly low, the PTC heater is kept on, and the water inflow M0 is set as M0 min ; When the water temperature T3 is seriously too low (T3 < Tt - 10℃), the PTC heater is turned on to 100%, and the water inlet flow M0 is set to M0 min ; Wherein, Tt is the set target temperature of the electrolyzer 4 system, generally set to 60±5℃; ΔT is the preset temperature deviation threshold, set to 3~5℃ according to the actual situation.

7. The method of claim 4, wherein the method further comprises: The liquid level state is determined by multiple gear signals output by the liquid level sensor, including high liquid level LH, high-middle liquid level LHM, middle liquid level LM, low-middle liquid level LML, and low liquid level LL; the liquid level change trend is obtained by comparing the current liquid level state with the last period state.

8. The PEM electrolyzer control method based on liquid level and temperature multi-modal intelligent control according to claim 5, characterized in that: In mode three, when T3 is in T3>Tt+10℃, it is a serious temperature overhigh, the PTC heater power is closed, and the radiator (3) is started with the power opened to 100%; When T3 is in Tt+ΔT<T3≤Tt+10℃, it is a slight temperature overhigh, the PTC heater power is closed, and the radiator (3) is started; When T3 is in Tt-ΔT<T3≤Tt+ΔT, it is the best interval, the PTC heater is closed, and the water inlet flow M0 is closed; When T3 is in Tt-10℃<T3≤Tt-ΔT, it is a slight temperature overlow, the water inlet flow M0 is closed, and the PTC heater is started; When T3 is in T3<Tt-10℃, it is a serious temperature overlow, the water inlet flow M0 is closed, and the PTC heater power is started to 100%; Wherein, Tt is generally set to 60±5℃, and ΔT is set to 3~5℃ according to the actual situation.

9. The method of claim 4, wherein the method is a method of controlling a PEM electrolyzer based on liquid level and temperature multi-modal intelligence, characterized by: The method is suitable for a distributed hydrogen production system, and is used for improving a cold start speed, reducing system energy consumption, protecting a rear-end sensor, and maintaining a stable operation temperature.

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