A control system and control method of an AEM electrolytic cell directly connected under a photovoltaic panel

Abstract

This invention relates to a control system and method for an AEM electrolyzer directly connected to a photovoltaic panel, comprising: a photovoltaic power supply module for converting solar energy into direct current to provide a stable power supply; an intelligent switching module for real-time monitoring of the output power of the photovoltaic power supply module and outputting switching commands based on the photovoltaic output power; and an AEM electrolyzer including three negative terminals for switching the negative terminal connection position according to the switching command to change the total number of electrolyzer segments in operation. The control system of this invention achieves dynamic and precise matching between photovoltaic output and the number of operating segments of the electrolyzer through a special one-positive-three-negative electrode structure and segmented operation, ensuring efficient and safe operation of the system under all working conditions, suppressing the increase of hydrogen concentration in oxygen, achieving high overall photovoltaic energy utilization, simple structure, flexible control, strong adaptability, low implementation and modification costs, and possessing extremely high engineering promotion value.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic direct-connection green hydrogen preparation technology, and more specifically, to a control system and control method for an AEM electrolyzer directly connected to a photovoltaic panel. Background Technology

[0002] With the advancement of the global zero-carbon energy transition, green hydrogen has become a core carrier for absorbing fluctuating renewable energy sources such as photovoltaics. Anion exchange membrane (AEM) electrolyzers have become a key development direction for green hydrogen production due to their advantages of using non-precious metal catalysts, low cost, and fast response.

[0003] Traditional photovoltaic hydrogen production employs an indirect coupling architecture of "photovoltaic-inverter-grid-rectifier-electrolyzer," which suffers from several inherent technical drawbacks: First, the energy conversion chain is lengthy, with the two-stage power conversion stages of inverter and rectification resulting in a 5% to 8% loss in overall system efficiency, directly reducing the energy utilization efficiency of green hydrogen production. Second, power dynamic response is lagging; grid-side scheduling constraints and the inherent delays in the power conversion stages prevent the system from accurately tracking the millisecond-level rapid fluctuations in photovoltaic output, making it difficult to adapt to the highly intermittent nature of renewable energy. Third, system investment costs are high; the cost of inverters, step-up transformers, rectifier cabinets, and other power-related equipment significantly increases the initial investment, weakening the market competitiveness of green hydrogen. Fourth, scenario adaptability is limited; the system must rely on public AC grid access for stable operation, severely restricting its application in remote areas without grid access, islands, and distributed off-grid scenarios.

[0004] To address this, the industry has proposed a direct connection scheme where photovoltaic DC power is directly connected to the electrolyzer. This means the DC power output from the photovoltaic array is directly connected to the electrolyzer without going through inverters or rectifiers. Theoretically, this can eliminate efficiency losses from multi-stage power conversion, improve system dynamic response speed, reduce investment in supporting equipment, and enable independent operation in off-grid scenarios. However, this technical approach has encountered a significant safety bottleneck in practical engineering applications: the output power of photovoltaic power generation fluctuates dramatically in real time due to factors such as solar irradiance, ambient temperature, and cloud cover, causing the electrolyzer to operate in a wide-range variable power state for extended periods.

[0005] The hydrogen concentration in oxygen is a core parameter determining the intrinsic safety level of a water electrolysis hydrogen production system. When an AEM electrolyzer operates under low current density conditions, the electrochemical reaction rate decreases significantly, and the dissolution and diffusion effects of hydrogen and oxygen in the electrolyte, as well as the cross-permeation behavior across the membrane, are significantly amplified, directly leading to an abnormally high hydrogen concentration in the oxygen on the anode side. Once the hydrogen concentration in oxygen reaches the explosion limit threshold, it will trigger a severe risk of combustion and explosion, posing a fatal threat to the safety of personnel and equipment in the entire hydrogen production unit. Currently, the known safe operating load range for an AEM electrolyzer is generally 10% to 120% of its rated power. When the input power of the photovoltaic direct-connected system is less than 10% of the rated power, the electrochemical reaction balance of the electrolyzer is disrupted, and the hydrogen concentration in oxygen will rapidly exceed the safety threshold stipulated by national safety standards, making it impossible to guarantee the safe operation of the system.

[0006] Current technologies cannot stably control the hydrogen concentration in oxygen across the entire power fluctuation range of photovoltaic systems, severely hindering the large-scale deployment of photovoltaic-to-AEM hydrogen production technology. Therefore, developing a photovoltaic-to-AEM electrolyzer hydrogen production technology that can adapt to the full power fluctuation characteristics of photovoltaic systems, especially maintaining stable hydrogen concentration within a safe range during low-power operation, has become a critical technical problem urgently needing to be solved in this field. Summary of the Invention

[0007] The technical problem to be solved by the present invention is that the existing technology cannot stably control the hydrogen concentration in oxygen within the full power fluctuation range. In view of the above-mentioned defects of the existing technology, a control system and control method for an AEM electrolyzer directly connected to a photovoltaic panel are proposed.

[0008] The technical solution adopted by this invention to solve its technical problem is: to propose a control system for an AEM electrolytic cell directly connected to a photovoltaic panel, comprising: Photovoltaic power supply modules are used to convert solar energy into direct current to provide a stable power supply; The intelligent switching module is used to monitor the output power of the photovoltaic power supply module in real time and output switching commands according to the photovoltaic output power. The AEM electrolytic cell includes three negative terminals, which are used to switch the negative terminal connection position according to the switching command to change the total number of electrolytic cell sections put into operation.

[0009] In some embodiments, the photovoltaic power supply module includes a photovoltaic array and a wide-range DC / DC converter.

[0010] In some embodiments, the intelligent switching module includes: The photovoltaic power monitoring unit is used to collect the output voltage and current of the photovoltaic array in real time and calculate the photovoltaic output power. The control unit is used to compare the current output power with the preset photovoltaic power grading threshold and output a switching command based on the output result. The switching execution unit includes a primary switch, a secondary switch, and a tertiary switch corresponding to the three negative terminals, respectively, and is used to turn on the primary switch, the secondary switch, or the tertiary switch according to the switching command.

[0011] In some embodiments, the AEM electrolytic cell is provided with a common positive terminal, and three independent negative terminals are led out from the cathode end, namely a first negative terminal connected to the primary switch, a second negative terminal connected to the secondary switch, and a third negative terminal connected to the tertiary switch.

[0012] In some embodiments, the intelligent switching module further includes an oxygen-hydrogen concentration monitoring unit for real-time monitoring of the oxygen-hydrogen concentration in the AEM electrolyzer.

[0013] In some embodiments, the control unit further includes a hysteresis buffer.

[0014] In some embodiments, the control unit further includes: current rise rate control.

[0015] This invention also proposes a control method for an AEM electrolyzer directly connected to a photovoltaic panel, adapted to the control system of an AEM electrolyzer directly connected to a photovoltaic panel as described above, comprising: S1, real-time acquisition of photovoltaic output power of photovoltaic array, and simultaneous monitoring of hydrogen concentration in oxygen during AEM electrolyzer operation; S2, compare the current photovoltaic output power with the photovoltaic power grading threshold; S3, when the photovoltaic output power reaches the first start-up threshold, close the first-stage switch and connect the first negative terminal to start the first electrolytic cell with a high current density. S4, when the photovoltaic output power reaches the second start-up threshold, close the secondary switch and connect the second negative terminal to start the second electrolytic cell with a high current density. S5, when the photovoltaic output power reaches the third start-up threshold, close the three-stage switch and connect the third negative terminal to start the third electrolytic cell with a high current density. S6, when the photovoltaic output power is less than the first back-off threshold, close the secondary switch and connect the second negative terminal to start the second electrolytic cell with a high current density. S7, when the photovoltaic output power is less than the second back-off threshold, close the first-level switch and connect the first negative terminal to start the first electrolytic cell with a high current density. S8: When the photovoltaic output power is less than the third back-off threshold, disconnect all switches.

[0016] In some embodiments, step S2 specifically includes: S21, photovoltaic power grading threshold and oxygen hydrogen concentration safety threshold settings; S22, compare the hydrogen concentration in oxygen with the safe threshold for hydrogen concentration in oxygen; S23, if the hydrogen concentration in oxygen exceeds the safe threshold for hydrogen concentration in oxygen, a downgrade switch is performed, the upper-level control switch is closed, and the current switch is opened; if the hydrogen concentration in oxygen does not exceed the safe threshold for hydrogen concentration in oxygen, the current photovoltaic output power is compared with the photovoltaic power grading threshold.

[0017] In some embodiments, the photovoltaic power grading thresholds include: a first start-up threshold, a second start-up threshold, a third start-up threshold, a first fallback threshold, a second fallback threshold, and a third fallback threshold.

[0018] The AEM electrolyzer control system directly connected to the photovoltaic panel of this invention only activates the first electrolyzer at low power, ensuring that the electrochemical reaction rate in the electrolysis chamber remains at a high level. This suppresses the cross-permeation of hydrogen and oxygen through the membrane electrode from a reaction mechanism perspective, stably controlling the hydrogen concentration in oxygen below 1.5% under low power conditions, achieving precise and effective control of hydrogen concentration in oxygen. As the output power of the photovoltaic array gradually increases, the control unit sequentially activates the second and third electrolyzers, ensuring that all operating electrolyzers operate within a high current density range throughout the process. This fundamentally reduces the risk of exceeding the hydrogen concentration limit in oxygen across all operating conditions, achieving high current density operation under all conditions. Through a special one-positive-three-negative electrode structure and segmented activation method, the minimum stable operating load of the electrolyzer is significantly reduced from the industry-standard 10%~12% of rated power to 3%~5% of rated power, allowing for... The electrolyzer can maintain a stable electrochemical reaction state at extremely low power, eliminating the need for frequent start-stop standby and expanding its low-load operating range. With the minimum operating load reduced, stable hydrogen production can also be achieved during low-light periods, such as early morning and evening, which traditional solutions cannot cover. It can capture more photovoltaic energy in the low-power range, increasing overall photovoltaic energy utilization by 5% to 7% compared to traditional photovoltaic hydrogen production systems, significantly improving the power generation consumption ratio and hydrogen production capacity of photovoltaic power plants. Through a special one-positive-three-negative electrode structure and segmented input method, segmented matching across the entire power range can be achieved. The structure is simple and the control is flexible. All parameters such as switching thresholds, starting current, and current rise slope can be manually configured through the human-machine interface of the control unit, facilitating targeted parameter optimization for different models of electrolyzers and photovoltaic arrays with different installed capacities. It has strong adaptability, low implementation and modification costs, and extremely high engineering promotion value. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 The diagram shown is a block diagram of the AEM electrolytic cell control system directly connected to the photovoltaic panel of this invention. Figure 2 The diagram shown is a schematic of the control system of the AEM electrolytic cell directly connected to the photovoltaic panel of this invention. Figure 3 The diagram shown is a schematic diagram of the structure of the AEM electrolytic cell in the AEM electrolytic cell control system directly connected to the photovoltaic panel of the present invention. Figure 4 The figure shown is a graph of the photovoltaic output power and electrolytic cell current characteristics of the AEM electrolytic cell control system directly connected to the photovoltaic panel of the present invention. Figure 5 The diagram shows a flowchart of the control method for the AEM electrolytic cell directly connected to the photovoltaic panel according to the present invention. Figure 6 The diagram shows a flowchart of step S2 of the control method for the AEM electrolytic cell directly connected to the photovoltaic panel of the present invention. Figure 7 The diagram shows a flowchart of step S3 of the control method for an AEM electrolyzer directly connected to a photovoltaic panel according to the present invention. Figure 8 The diagram shows a flowchart of step S4 of the control method for the AEM electrolytic cell directly connected to the photovoltaic panel of the present invention. Figure 9 The diagram shows a flowchart of step S5 of the control method for an AEM electrolyzer directly connected to a photovoltaic panel according to the present invention. Figure 10 The diagram shows a flowchart of step S6 in the control method of the AEM electrolyzer directly connected to the photovoltaic panel of the present invention. Figure 11 The diagram shows a flowchart of step S7 of the control method for the AEM electrolytic cell directly connected to the photovoltaic panel of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only 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.

[0021] Please refer to Figure 1 and Figure 3This invention proposes a control system for an AEM electrolyzer directly connected to a photovoltaic panel, comprising: a photovoltaic power supply module, an intelligent switching module, and an AEM electrolyzer. The photovoltaic power supply module converts solar energy into direct current to provide a stable power supply to the AEM electrolyzer. The intelligent switching module monitors the photovoltaic output power of the photovoltaic power supply module in real time and outputs switching commands based on the photovoltaic output power. The AEM electrolyzer includes three negative terminals, used to switch the negative terminal connection position according to the executed command to change the total number of electrolyzer segments in operation. The control system of this invention adjusts the negative terminal connection position of the electrolyzer according to the photovoltaic output power, thereby adjusting the total voltage and equivalent current density of the entire stack, achieving dynamic and precise matching between photovoltaic output and the number of operating electrolyzer segments, ensuring efficient and safe operation of the system under all operating conditions, and suppressing the increase of hydrogen concentration in oxygen.

[0022] Please refer to Figure 2 The photovoltaic power supply module in this embodiment mainly consists of two parts: a photovoltaic array and a wide-range DC / DC (direct-to-direct-current conversion) converter. The photovoltaic array is composed of multiple independent photovoltaic strings. The output of each photovoltaic string is directly connected to the primary input port of the wide-range DC / DC converter one-to-one through an independent DC cable. The entire process does not go through a centralized combiner box for current collection, thus avoiding line losses in the combiner stage and power mismatch between strings under local shading.

[0023] The wide-range DC / DC converter adopts a dual active bridge (DAB) topology, which consists of three core parts: a primary-side full-bridge circuit, a high-frequency isolation transformer, and a secondary-side full-bridge circuit. All four switching devices in the primary-side full-bridge circuit are SiC MOSFETs, with their inputs directly connected to the corresponding string outputs of the photovoltaic array. The primary winding of the high-frequency isolation transformer connects to the AC output of the primary-side full-bridge, while the secondary winding connects to the AC input of the secondary-side full-bridge. The turns ratio of the high-frequency isolation transformer is specially optimized, and combined with the phase-shift control strategy of both full-bridge circuits, it can achieve an ultra-wide voltage gain adjustment range of over 3:1. Relying on the physical isolation design of the high-frequency isolation transformer, this DC / DC converter achieves complete electrical isolation between the photovoltaic side and the electrolyzer side. This not only blocks the common-mode leakage current from the photovoltaic side from flowing to the electrolyzer, preventing stray current corrosion of the electrodes inside the electrolyzer, but also prevents the propagation of fault current to the electrolyzer side in the event of an insulation fault on the photovoltaic side. This eliminates the need for additional isolation protection devices, thus meeting the high-voltage safety protection requirements of photovoltaic hydrogen production scenarios. The following are the specific parameters for a wide-range DC / DC converter.

[0024]

[0025] For further details, please refer to... Figure 2The intelligent switching module includes: a photovoltaic power monitoring unit, used to collect the output voltage and current of the photovoltaic array in real time and calculate the photovoltaic output power; a control unit, used to compare the current output power with the preset photovoltaic power grading threshold and output a switching command according to the output result; and a switching execution unit, including a primary switch, a secondary switch and a tertiary switch corresponding to the three negative terminals, used to turn on the corresponding switches and connect the corresponding negative terminals according to the switching command of the negative terminals.

[0026] The photovoltaic power monitoring unit collects the output voltage and current of the photovoltaic array in real time and calculates the real-time output power through voltage sampling terminals and current Hall sensors. The sampling frequency is 10Hz, and it also records short-term power change trends to avoid frequent false switching caused by light fluctuations.

[0027] The control unit uses an industrial-grade ARM main control chip with a built-in photovoltaic power grading threshold. During operation, it compares the real-time monitoring data of the photovoltaic power monitoring unit with the photovoltaic power grading threshold. After the condition is met for three consecutive sampling cycles, it outputs a negative pole switching command to the switching execution unit to avoid malfunctions caused by instantaneous data disturbances.

[0028] The first, second, and third level switches of the switching execution unit correspond one-to-one with the three negative terminals of the AEM electrolytic cell. The switches are DC solid-state relays with arc-extinguishing structures, and the common terminal is connected to the main negative terminal of the electrolytic cell.

[0029] Please refer to Figure 3 The AEM electrolytic cell provided in this embodiment is a segmented AEM electrolytic cell. Structurally, it adopts a special series architecture with a single chamber and multiple independent negative electrodes. The entire electrolytic cell is equipped with only one common positive electrode terminal, while three independent negative electrode terminals are led out from the cathode end, which are defined as the first negative electrode terminal, the second negative electrode terminal, and the third negative electrode terminal, respectively. The three electrolytic units inside the electrolytic cell are connected in series sequentially along the current flow direction. By switching the connection state of different negative electrode terminals through the switching execution unit, the total number of electrolytic chambers in operation can be flexibly changed without adjusting the connection state on the positive electrode side.

[0030] The anode-side fluid channels of all series-connected electrolysis units in this AEM electrolyzer are fully interconnected, sharing the same anode gas-generating chamber. The power supply current connected from the shared positive terminal can flow evenly through the anode catalyst layer of all series-connected electrolysis units, avoiding uneven anode current distribution due to segmented switching. The cathode end is divided into three independent negative electrode sections along the series direction, corresponding to the first, second, and third negative electrode terminals, respectively. Each negative electrode section corresponds to several series-connected electrolysis chambers. The rated number of sections in the three negative electrode sections is configured in a 1:2:3 ratio to adapt to the three power grading levels of photovoltaic power supply modules. The three negative terminal sections are independent of each other only at the external circuit level. The first negative terminal corresponds to the primary switch, the second negative terminal to the secondary switch, and the third negative terminal to the tertiary switch. Each negative terminal is connected to the main negative busbar of the electrolytic cell through a corresponding switch. During operation, the common positive terminal of the electrolytic cell always maintains a stable connection with the positive terminal of the photovoltaic power supply module. Different negative terminals are connected to the main negative circuit only by switching the corresponding switches on and off. The specific parameters for the segmented switching of the negative terminals are as follows.

[0031]

[0032] In actual operation, when the photovoltaic output power is in the low-power range, only the primary switch corresponding to the first negative terminal is closed, while the secondary and tertiary switches are open, and the electrolysis cells corresponding to the first negative terminal section are put into operation. When the photovoltaic output power is in the medium-power range, only the secondary switch corresponding to the second negative terminal is closed, while the primary and tertiary switches are open, and the electrolysis cells corresponding to the second negative terminal section are connected in series to the circuit. When the photovoltaic output power is in the high-power range, only the tertiary switch corresponding to the third negative terminal is closed, while the primary and secondary switches are open, and all the electrolysis cells corresponding to the third negative terminal section are connected in series to the circuit. No switching operation is required on the positive side throughout the entire process; the number of electrolyzer sections can be adjusted in three levels simply by switching a single negative terminal. This achieves dynamic matching between photovoltaic output and the number of operating electrolyzer sections, avoiding the safety risk of excessive hydrogen concentration in oxygen under low light conditions. No anode flow interruption or gas path mixing issues occur during the switching process, perfectly adapting to the wide operating conditions required by photovoltaic direct-connected hydrogen production systems.

[0033] Furthermore, in some embodiments, the intelligent switching module also includes an oxygen-hydrogen concentration monitoring unit for real-time monitoring of the oxygen-hydrogen concentration in the AEM electrolyzer. Specifically, the oxygen-hydrogen concentration monitoring unit employs an electrochemical hydrogen sensor. The probe is installed on the oxygen outlet pipeline of the electrolyzer via a sealed flange, enabling real-time online monitoring of the hydrogen concentration in the oxygen, with the data directly uploaded to the control unit. The control unit has a built-in oxygen-hydrogen concentration safety threshold. If the oxygen-hydrogen concentration exceeds the safety threshold, the control unit automatically triggers a degradation switching, reducing the number of operating stages to increase current density and quickly bringing the concentration back to the safe range. The oxygen-hydrogen concentration monitoring unit, acting as hydrogen concentration feedback control, combined with the output power monitoring unit, further enhances system safety performance.

[0034] Furthermore, in some embodiments, the control unit further includes a hysteresis buffer. The control unit sets a hysteresis buffer between two adjacent power switching thresholds to avoid fluctuations in photovoltaic output power near the segmented switching thresholds, which could cause repeated switching of the negative terminal and frequent switching operations leading to switching losses.

[0035] Furthermore, in some embodiments, the control unit also includes: current rise rate control. The control unit presets a current rise slope. After each switching action of a new segment of the electrolytic cell is completed, the control unit will not directly increase the output current of that segment to the maximum. Instead, it will gradually increase the operating current of that segment according to the preset current rise slope. The current rise slope can be configured according to the actual working conditions. This avoids large current surges during the switching process, which will not disturb the output characteristics of the photovoltaic array, nor will it cause sudden current changes to damage the electrodes and membrane electrodes of the electrolytic cell. This achieves a smooth transition without impact during the segmented switching process.

[0036] It should be noted that the intelligent switching module is also connected to the host computer. All operating data and fault alarm information of the intelligent switching module are uploaded to the host computer platform in real time. It also supports receiving remote parameter configuration and forced gear switching commands issued by the host computer. The host computer communication function integrates both Modbus TCP and Modbus RTU dual protocol interfaces.

[0037] The present invention will be further described in detail below through specific embodiments.

[0038] Example 1

[0039] Please refer to Figure 4The DC power output from the photovoltaic power supply module is directly connected to the AEM electrolytic cell. The control unit sets photovoltaic power grading thresholds as follows: the first starting threshold is 12.6kW, the second starting threshold is 130kW, and the third starting threshold is 255kW. The photovoltaic power monitoring unit acquires the photovoltaic output power in real time. During operation, the control unit compares the current output power uploaded by the photovoltaic power monitoring unit with the corresponding photovoltaic power grading threshold in real time, and automatically switches the negative terminal of the electrolytic cell based on the comparison result to achieve segmented operation.

[0040] The first stage is the low-power operation segment, corresponding to a photovoltaic output power range of 12~126kW, suitable for low-light conditions in the early morning and evening. When the real-time photovoltaic output power of the photovoltaic array rises to the first start-up threshold of 12.6kW, the control unit outputs a first-level switching command. The switching execution unit only closes the first-level switch corresponding to the first negative terminal, and opens the second-level and third-level switches. The electrolysis cell corresponding to the first negative terminal group is then connected to the power supply circuit for operation. In this stage, the first electrolyzer uses 200A as the starting operating current, corresponding to a current density within the high-efficiency and safe range. It can stably control the hydrogen concentration in oxygen below 1.5% under extremely low power conditions, far below the national standard safety red line of 2%. As the photovoltaic output power gradually increases, the operating current of the first electrolyzer rises smoothly according to the preset current rise slope until it reaches the rated current upper limit of 1500A. At this time, the total output power of the photovoltaic array is approximately 126kW, and the operating voltage of the electrolyzer remains stable within the range of 63~84V throughout the entire process.

[0041] The second stage is the medium-power operation segment, corresponding to a photovoltaic output power range of 130~252kW, suitable for moderate sunlight conditions in the morning and afternoon. When the real-time photovoltaic output power continues to rise to the second start-up threshold of 130kW, the control unit outputs a secondary switching command. The switching execution unit closes the secondary switch corresponding to the second negative terminal, and opens the primary and tertiary switches. The second electrolyzer is connected to the power supply circuit with a starting current of 900A. At this time, the electrolysis chambers corresponding to the second negative terminal are put into operation in series. The current of the second electrolyzer is maintained in a high current density range above 900A, ensuring that the hydrogen concentration in oxygen is within a safe range throughout the process. As the photovoltaic output power continues to increase, the operating current of the second electrolyzer gradually rises to the rated current limit of 1500A according to the preset current rise slope. At this time, the total output power of the photovoltaic array is approximately 252kW, and the operating voltage of the electrolyzer remains stable in the range of 144~168V throughout the process.

[0042] The third stage is the high-power operation segment, corresponding to a photovoltaic output power range of 255~375kW, suitable for strong sunlight conditions during midday. When the real-time photovoltaic output power continues to rise to the third start-up threshold of 255kW, the control unit outputs a three-stage switching command. The switching execution unit closes the three-stage switch corresponding to the third negative terminal, and opens the first-stage and second-stage switches. The third electrolytic cell is connected to the power supply circuit with a starting current of 1100A. At this time, all electrolytic cells corresponding to the third negative terminal are connected in series and put into operation, and the current of each electrolytic cell is maintained in a high current density range of over 1100A. As the photovoltaic output power continues to increase, the operating current of the third electrolytic cell gradually rises to the rated current limit of 1500A according to the preset current rise slope. At this time, the total output power of the photovoltaic array is approximately 375kW, and the operating voltage of the electrolytic cell remains stable in the range of 231~250V throughout the entire process.

[0043] When the photovoltaic output power decreases, the intelligent switching module disconnects the corresponding negative terminals in reverse order, ensuring that each operating segment maintains a high current density and preventing an increase in hydrogen concentration in the oxygen. All switching thresholds and current parameters can be manually set in the control unit.

[0044] This embodiment relies on a segmented AEM electrolyzer with three independent negative electrodes and an intelligent switching module to construct a three-segment precisely matched segmented operation mechanism. Throughout the process, the current in each segment of the electrolyzer remains stable within the optimal operating range of 200-1500A. Unlike traditional AEM electrolyzers that require more than 10% of rated power for stable operation, the electrolyzer of this invention can still start and operate stably at 3%-5% of rated power. Simultaneously, by controlling the hydrogen concentration in oxygen to below 1.5% through high current density, it fundamentally avoids the problems of sudden efficiency drops and excessive hydrogen concentration in oxygen caused by excessively low current density under low load in traditional photovoltaic direct-connected hydrogen production systems. According to photovoltaic output characteristics statistics, reducing the minimum operating load from 10% to 3%-5% can increase photovoltaic utilization by 5%-7%, thus improving photovoltaic efficiency.

[0045] Example 2

[0046] The control unit sets the safe threshold for hydrogen concentration in oxygen to 1.5% VOL. During operation, the hydrogen concentration monitoring unit monitors the hydrogen content in the oxygen in real time. The control unit compares the real-time concentration value uploaded by the monitoring unit with the corresponding safe threshold. If the real-time hydrogen concentration exceeds the 1.5% VOL safe threshold during operation, the control unit will directly trigger a degradation switch, automatically reducing the number of electrolyzer sections in operation and increasing the operating current density of each electrolysis cell to quickly bring the hydrogen concentration back to the safe range.

[0047] Example 3

[0048] Taking the medium-power operation segment corresponding to the second negative terminal in Example 1 as an example, the control unit sets the second start threshold to 130kW and the disconnection backoff threshold to 120kW, forming a 10kW hysteresis buffer zone between the two thresholds. When the system is in a low-power operation state, a switching command will only be triggered and the secondary switch will be turned on to enter the medium-power operation state if the real-time photovoltaic output power rises above 130kW for three consecutive sampling cycles. After entering the medium-power level, even if the photovoltaic power falls below 130kW, the backoff switching will not be triggered as long as it does not remain below 120kW.

[0049] The width of this hysteresis interval can be flexibly configured according to the power plant's illumination characteristics. In this embodiment, it is uniformly set to 8% of the rated power of the corresponding level. This ensures that the system will not operate inefficiently for a long time due to an excessively wide interval, nor will it lose its anti-frequent switching function due to an excessively narrow interval. This logic can reduce the frequency of switching operations by more than 90%, significantly extending the life of devices, while avoiding current surges in the electrolyzer caused by frequent switching, thus significantly improving the operational stability of the photovoltaic direct-connected hydrogen production system.

[0050] The AEM electrolyzer control system directly connected to the photovoltaic panel of this invention only activates the first electrolyzer at low power, ensuring that the electrochemical reaction rate in the electrolysis chamber remains at a high level. This suppresses the cross-permeation of hydrogen and oxygen through the membrane electrode from a reaction mechanism perspective, stably controlling the hydrogen concentration in oxygen below 1.5% under low power conditions, achieving precise and effective control of hydrogen concentration in oxygen. As the output power of the photovoltaic array gradually increases, the control unit sequentially activates the second and third electrolyzers, ensuring that all operating electrolyzers operate within a high current density range throughout the process. This fundamentally reduces the risk of exceeding the hydrogen concentration limit in oxygen across all operating conditions, achieving high current density operation under all conditions. Through a special one-positive-three-negative electrode structure and segmented activation method, the minimum stable operating load of the electrolyzer is significantly reduced from the industry-standard 10%~12% of rated power to 3%~5% of rated power, allowing for... The electrolyzer can maintain a stable electrochemical reaction state at extremely low power, eliminating the need for frequent start-stop standby and expanding its low-load operating range. With the minimum operating load reduced, stable hydrogen production can also be achieved during low-light periods, such as early morning and evening, which traditional solutions cannot cover. It can capture more photovoltaic energy in the low-power range, increasing overall photovoltaic energy utilization by 5% to 7% compared to traditional photovoltaic hydrogen production systems, significantly improving the power generation consumption ratio and hydrogen production capacity of photovoltaic power plants. Through a special one-positive-three-negative electrode structure and segmented input method, segmented matching across the entire power range can be achieved. The structure is simple and the control is flexible. All parameters such as switching thresholds, starting current, and current rise slope can be manually configured through the human-machine interface of the control unit, facilitating targeted parameter optimization for different models of electrolyzers and photovoltaic arrays with different installed capacities. It has strong adaptability, low implementation and modification costs, and extremely high engineering promotion value.

[0051] Please refer to Figure 5 This invention also proposes a control method for an AEM electrolyzer directly connected to a photovoltaic panel. The control method in this embodiment is fully compatible with the control system of an AEM electrolyzer directly connected to a photovoltaic panel. Relying on the segmented AEM electrolyzer structure with one positive and three negative terminals and an intelligent switching module, it can achieve dynamic and precise matching between photovoltaic output and the number of operating segments of the electrolyzer, ensuring efficient and safe operation of the system under all working conditions. The specific steps include: S1, real-time acquisition of photovoltaic output power of photovoltaic array, and simultaneous monitoring of hydrogen concentration in oxygen during AEM electrolyzer operation; S2, compare the current photovoltaic output power with the photovoltaic power grading threshold; S3, when the photovoltaic output power reaches the first start-up threshold, close the first-stage switch and connect the first negative terminal to start the first electrolytic cell with a high current density. S4, when the photovoltaic output power reaches the second start-up threshold, close the secondary switch and connect the second negative terminal to start the second electrolytic cell with a high current density. S5, when the photovoltaic output power reaches the third start-up threshold, close the three-stage switch and connect the third negative terminal to start the third electrolytic cell with a high current density. S6, when the photovoltaic output power is less than the first back-off threshold, close the secondary switch and connect the second negative terminal to start the second electrolytic cell with a high current density. S7, when the photovoltaic output power is less than the second back-off threshold, close the first-level switch and connect the first negative terminal to start the first electrolytic cell with a high current density. S8: When the photovoltaic output power is less than the third back-off threshold, disconnect all switches.

[0052] In step S1, after the system is powered on, the control unit collects the output voltage and current of the photovoltaic array in real time at a fixed frequency through the photovoltaic power monitoring unit and calculates the photovoltaic output power. At the same time, the hydrogen concentration data at the oxygen outlet of the AEM electrolyzer is monitored throughout the process through the oxygen hydrogen concentration monitoring unit. The two types of monitoring data are uploaded to the control unit simultaneously to complete preprocessing, eliminate abnormal values ​​caused by instantaneous disturbances, and provide a reliable basis for subsequent control logic.

[0053] Please refer to Figure 6 Step S2 specifically includes the following steps: S21, photovoltaic power grading threshold and oxygen hydrogen concentration safety threshold settings; S22, compare the hydrogen concentration in oxygen with the safe threshold for hydrogen concentration in oxygen; S23, if the hydrogen concentration in oxygen exceeds the safe threshold for hydrogen concentration in oxygen, a downgrade switch is performed, the upper-level control switch is closed, and the current switch is opened; if the hydrogen concentration in oxygen does not exceed the safe threshold for hydrogen concentration in oxygen, the current photovoltaic output power is compared with the photovoltaic power grading threshold.

[0054] In step S21, the operator sets parameters through the human-machine interface of the control unit or a host computer connected to the control unit. Specific parameters include: photovoltaic power grading threshold and oxygen-hydrogen concentration safety threshold. The photovoltaic power grading threshold includes: a first start-up threshold, a second start-up threshold, a third start-up threshold, a first fallback threshold, a second fallback threshold, and a third fallback threshold. The oxygen-hydrogen concentration monitoring unit monitors the oxygen-hydrogen concentration throughout the electrolyzer's operation and uploads the monitoring data to the control unit. If the current oxygen-hydrogen concentration exceeds the oxygen-hydrogen concentration safety threshold, the control unit will directly trigger a downgrade switch, automatically reducing the number of electrolyzer segments in operation, increasing the operating current density of each electrolysis cell, and quickly bringing the oxygen-hydrogen concentration back to a safe range. The downgrade switch specifically involves switching from a three-stage switch to a two-stage switch, from a two-stage switch to a one-stage switch, and from a one-stage switch to no switch. That is, when the oxygen-hydrogen concentration in the first electrolyzer segment is found to be greater than the safety threshold during operation, all switches are immediately disconnected, putting the system in a shutdown state.

[0055] Please refer to Figure 7 Step S3 specifically includes the following steps: S31 outputs a conduction command to the first-level switch, closes the first-level switch, connects the first negative terminal, and connects the electrolytic cell corresponding to the first negative terminal group to the power supply circuit. S32, the first current is increased according to the first current rise slope until the first rated current is reached.

[0056] When the real-time output power of the photovoltaic system rises to the preset first start-up threshold, the control unit outputs a first-level switching command, the first-level switch closes, and the electrolysis chamber corresponding to the first negative electrode section is connected to the power supply circuit for operation. This enables the first electrolyzer to start up with a high current density, simultaneously executing a 5-10s soft start-up process. Throughout the process, the hydrogen concentration in the oxygen is controlled below the safety threshold, ensuring safe operation during the start-up phase. The control unit pre-sets the first current rise slope. As the photovoltaic output power gradually increases, the operating current of the first electrolyzer rises smoothly according to the preset first current rise slope until it reaches the first rated current, completing the transition to full-load operation of a single section.

[0057] Understandably, if the real-time output power of the photovoltaic system does not reach the first start-up threshold, it will remain in standby mode.

[0058] Please refer to Figure 8 Step S4 specifically includes the following steps: S41 outputs a conduction command to the secondary switch, closes the secondary switch, connects the second negative terminal, and connects the electrolytic cell corresponding to the second negative terminal group to the power supply circuit; S42 outputs a disconnect command to the primary switch, disconnecting the primary switch; S43, increase the second current according to the second current rise slope until the second rated current is reached.

[0059] When the real-time output power of the photovoltaic system rises to the preset second start-up threshold, the intelligent switching module executes the switch from the first electrolytic cell to the second electrolytic cell. The control unit outputs a secondary switching command, and the switching execution unit first closes the secondary switch, connects the second negative terminal, and maintains the primary switch in an overlapping conduction state for 50ms. Then, it opens the primary switch and disconnects the first negative terminal. The 50ms overlapping conduction time avoids the risk of current interruption. As the photovoltaic output power further increases, the control unit smoothly increases the current according to the preset second current rise slope until it reaches the second rated current, completing the full-load coordinated operation of the second electrolytic cell.

[0060] Please refer to Figure 9 Step S5 specifically includes the following steps: S51 outputs a conduction command to the three-stage switch, closes the three-stage switch, connects the third negative terminal, and connects the electrolytic cell corresponding to the third negative terminal group to the power supply circuit; S52 outputs a disconnect command to the secondary switch, disconnecting the secondary switch; S53, the third current is increased according to the third current rise slope until the third rated current is reached.

[0061] When the real-time output power of the photovoltaic system rises to the preset third start-up threshold, the intelligent switching module executes the switch from the second-stage electrolytic cell to the third-stage electrolytic cell. The control unit outputs a secondary switching command, and the switching execution unit first closes the tertiary switch, connects the third negative terminal, and maintains the secondary switch in a continuous conducting state for 50ms of overlapping conduction. Then, it opens the secondary switch and disconnects the second negative terminal. The 50ms overlapping conduction time avoids the risk of current interruption. As the photovoltaic output power further increases, the control unit smoothly increases the current according to the preset third current rise slope until it reaches the third rated current, completing the full-capacity high-load operation of the third-stage electrolytic cell.

[0062] Please refer to Figure 10 Step S6 specifically includes the following steps: S61 outputs a conduction command to the secondary switch, closes the secondary switch, connects the second negative terminal, and connects the electrolytic cell corresponding to the second negative terminal group to the power supply circuit; S62 outputs a disconnect command to the three-stage switch, disconnecting the three-stage switch.

[0063] When the real-time output power of the photovoltaic is less than the first back-off threshold, the control unit performs the switching from the third electrolytic cell to the second electrolytic cell. First, it closes the secondary switch, connects the second negative terminal, and maintains the tertiary switch in an overlapping conduction state for 50ms. Then, it opens the tertiary switch and disconnects the third negative terminal. Through the 50ms overlapping conduction time, the risk of current interruption is avoided.

[0064] Please refer to Figure 11 Step S7 specifically includes the following steps: S71 outputs a conduction command to the first-level switch, closes the first-level switch, connects the second negative terminal, and connects the electrolytic cell corresponding to the first negative terminal group to the power supply circuit. S72 outputs a disconnect command to the secondary switch, disconnecting the secondary switch.

[0065] When the real-time output power of the photovoltaic is less than the second back-off threshold, the control unit performs the switching from the second electrolytic cell to the first electrolytic cell. First, it closes the first-level switch, connects the first negative terminal, and keeps the second-level switch in an overlapping conduction state for 50ms. Then, it opens the second-level switch and disconnects the second negative terminal. Through the 50ms overlapping conduction time, the risk of current interruption is avoided.

[0066] In step S8, when the photovoltaic output power is less than the third back-off threshold, the control unit directly disconnects all switches and all negative terminals to complete the shutdown, thus avoiding the problem of excessive hydrogen concentration in oxygen caused by low current density operation under low power throughout the process.

[0067] The entire process of load reduction and backtracking uses reverse switching logic to ensure that each section of the electrolyzer maintains a high current density, effectively suppressing abnormal increases in hydrogen concentration in oxygen and ensuring operational safety under all operating conditions.

[0068] In one specific embodiment, the specific switching logic of the control method of the present invention is shown in the figure below, where P is the current photovoltaic output power, the first start threshold is 12kW, the second start threshold is 130kW, the third start threshold is 255kW, the first back-off threshold is 240kW, the second back-off threshold is 115kW, and the third back-off threshold is 10kW.

[0069]

[0070] After the system is powered on, it continuously collects the photovoltaic output power P and the hydrogen concentration in the oxygen of the electrolyzer. When P ≥ 12kW, the startup process is triggered; otherwise, it remains in standby mode. The control unit issues a command to close the primary switch, performing a 5-10s soft start to start the first electrolyzer at a high current density. Subsequently, the current is increased according to a preset first current rise rate until the first rated current is reached, keeping the hydrogen concentration in the oxygen within a safe threshold throughout the process. When P ≥ 130kW is detected, a 50ms overlapping conduction logic is executed: first, the secondary switch is closed, keeping the first terminal continuously conducting for 50ms, then the primary switch is opened, putting the first and second electrolyzers in a high current density condition. Subsequently, the second stage current is increased according to the second current rise rate to the second rated current. When P ≥ 255kW is detected, a 50ms overlapping conduction logic is executed: first, the tertiary switch is closed, keeping the second terminal continuously conducting for 50ms, then the secondary switch is opened, putting the second and third electrolyzers in a high current density condition simultaneously. Subsequently, the third stage current is increased according to the third current rise rate to the third rated current. When the power drops to P<240kW, the secondary switch is closed first, and the tertiary switch is opened after a 50ms delay, returning to the second-stage operating state. When the power further drops to P<115kW, the primary switch is closed first, and the secondary switch is opened after a 50ms delay, returning to the first-stage operating state. When P<10kW is detected, the control unit issues a command to disconnect all switches, and the system completes shutdown, thus avoiding the problem of excessive hydrogen concentration in oxygen caused by low current density operation at low power throughout the process.

[0071] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0072] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They do not limit the scope of protection of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

[0073] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A control system for an AEM electrolytic cell directly connected to a photovoltaic panel, characterized in that, include: Photovoltaic power supply modules are used to convert solar energy into direct current to provide a stable power supply; The intelligent switching module is used to monitor the output power of the photovoltaic power supply module in real time and output switching commands according to the photovoltaic output power. The AEM electrolytic cell includes three negative terminals, which are used to switch the negative terminal connection position according to the switching command to change the total number of electrolytic cell sections put into operation.

2. The AEM electrolytic cell control system directly connected to the photovoltaic panel according to claim 1, characterized in that, The photovoltaic power supply module includes a photovoltaic array and a wide-range DC / DC converter.

3. The AEM electrolytic cell control system directly connected to the photovoltaic panel according to claim 2, characterized in that, The intelligent switching module includes: The photovoltaic power monitoring unit is used to collect the output voltage and current of the photovoltaic array in real time and calculate the photovoltaic output power. The control unit is used to compare the current output power with the preset photovoltaic power grading threshold and output a switching command based on the output result. The switching execution unit includes a primary switch, a secondary switch, and a tertiary switch corresponding to the three negative terminals, respectively, and is used to turn on the primary switch, the secondary switch, or the tertiary switch according to the switching command.

4. The AEM electrolytic cell control system directly connected to the photovoltaic panel according to claim 3, characterized in that, The AEM electrolytic cell is provided with a common positive terminal, and three independent negative terminals are led out from the cathode end, namely the first negative terminal connected to the first-stage switch, the second negative terminal connected to the second-stage switch, and the third negative terminal connected to the third-stage switch.

5. The AEM electrolytic cell control system directly connected to the photovoltaic panel according to claim 4, characterized in that, The intelligent switching module also includes an oxygen-hydrogen concentration monitoring unit, used to monitor the oxygen-hydrogen concentration in the AEM electrolyzer in real time.

6. The AEM electrolytic cell control system directly connected to the photovoltaic panel according to claim 5, characterized in that, The control unit also includes a hysteresis buffer zone.

7. The AEM electrolytic cell control system directly connected to the photovoltaic panel according to claim 5, characterized in that, The control unit also includes: current rise rate control.

8. A method for controlling an AEM electrolytic cell directly connected to a photovoltaic panel, characterized in that, The AEM electrolytic cell control system, adapted for direct connection to the photovoltaic panel as described in any one of claims 1-7, comprises: S1, real-time acquisition of photovoltaic output power of photovoltaic array, and simultaneous monitoring of hydrogen concentration in oxygen during AEM electrolyzer operation; S2, compare the current photovoltaic output power with the photovoltaic power grading threshold; S3, when the photovoltaic output power reaches the first start-up threshold, close the first-stage switch and connect the first negative terminal to start the first electrolytic cell with a high current density. S4, when the photovoltaic output power reaches the second start-up threshold, close the secondary switch and connect the second negative terminal to start the second electrolytic cell with a high current density. S5, when the photovoltaic output power reaches the third start-up threshold, close the three-stage switch and connect the third negative terminal to start the third electrolytic cell with a high current density. S6, when the photovoltaic output power is less than the first back-off threshold, close the secondary switch and connect the second negative terminal to start the second electrolytic cell with a high current density. S7, when the photovoltaic output power is less than the second back-off threshold, close the first-level switch and connect the first negative terminal to start the first electrolytic cell with a high current density. S8: When the photovoltaic output power is less than the third back-off threshold, disconnect all switches.

9. The control method for an AEM electrolytic cell directly connected to a photovoltaic panel according to claim 8, characterized in that, Step S2 specifically includes: S21, photovoltaic power grading threshold and oxygen hydrogen concentration safety threshold settings; S22, compare the hydrogen concentration in oxygen with the safe threshold for hydrogen concentration in oxygen; S23, if the hydrogen concentration in oxygen exceeds the safe threshold for hydrogen concentration in oxygen, a downgrade switch is performed, the upper-level control switch is closed, and the current switch is opened; if the hydrogen concentration in oxygen does not exceed the safe threshold for hydrogen concentration in oxygen, the current photovoltaic output power is compared with the photovoltaic power grading threshold.

10. The control method for an AEM electrolytic cell directly connected to a photovoltaic panel according to claim 9, characterized in that, The photovoltaic power grading thresholds include: a first start-up threshold, a second start-up threshold, a third start-up threshold, a first fallback threshold, a second fallback threshold, and a third fallback threshold.

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