Hydrogen-electricity coupling control system and method for off-grid green-electricity-based hydrogen production

Abstract

The present invention belongs to the technical field of green-electricity-based hydrogen production. Disclosed are a hydrogen-electricity coupling control system and method for off-grid green-electricity-based hydrogen production. The method comprises: executing MPPT control on each photovoltaic module, so as to maximize an output power; distributing output powers to power-type electrolyzers, and adjusting the duty cycles of boost DC / DC converters to stabilize a low-voltage-side current at a set value, such that the power-type electrolyzers always operate at rated power points; and distributing the output powers to regulation-type electrolyzers, and adjusting the output voltages of the boost DC / DC converters to stabilize a high-voltage-side voltage at a target value, such that the regulation-type electrolyzers absorb a fluctuating portion of a photovoltaic power. The present invention can effectively improve the efficiency of a green-electricity-based hydrogen production system, and can realize stable and sustainable hydrogen production without relying on energy storage.

Description

An off-grid green electricity hydrogen production hydrogen-electric coupling control system and method Technical Field

[0001] This invention relates to an off-grid green electricity hydrogen production hydrogen-hydrogen coupling control system and method, belonging to the field of green electricity hydrogen production technology. Background Technology

[0002] With the continuous advancement of large-scale renewable energy integration, the problem of source-load imbalance is becoming increasingly prominent. As an effective means to solve this problem, green electricity-based hydrogen production has experienced rapid development in recent years. Green electricity-based hydrogen production can be divided into two types: off-grid and grid-connected. Although traditional grid-connected hydrogen production uses the power grid as its power source, it cannot guarantee that the electricity comes entirely from green energy sources and cannot obtain green electricity certification (green certificates), thus preventing the sale of hydrogen and its derivatives to the international market.

[0003] In contrast, off-grid hydrogen production has a simpler structure, typically employing a fully DC system to reduce AC / DC conversion steps, thereby improving overall system efficiency. Off-grid green electricity production is particularly advantageous in scenarios lacking strong grid connection capabilities, such as renewable energy bases in desert or arid regions. With the large-scale integration of renewable energy sources, off-grid green electricity production will see wider application in the future; however, achieving this goal still requires overcoming several technological bottlenecks, especially in improving system efficiency, stability, and sustainability. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an off-grid green electricity hydrogen production hydrogen-electric coupling control system and method. By optimizing the working state of the electrolyzer, the hydrogen production efficiency is improved, and the problem that the electrolyzer in the existing green electricity hydrogen production system fails to operate at the optimal efficiency point is solved.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0006] In a first aspect, the present invention provides an off-grid green electricity hydrogen production hydrogen-electric coupling control system, comprising:

[0007] Multiple photovoltaic modules, each connected to an electrolytic cell via a boost DC / DC converter, are provided with maximum power point tracking (MPPT) control to maximize output power.

[0008] Multiple electrolytic cells, including power-type electrolytic cells and adjustable electrolytic cells;

[0009] The power distribution unit includes:

[0010] The power electrolyzer control module is used to distribute the output power to the power electrolyzer. By adjusting the duty cycle of the boost DC / DC converter, the low-voltage side current is stabilized at the set value so that the power electrolyzer always operates at the rated power point.

[0011] The regulating electrolytic cell control module is used to distribute the output power to the regulating electrolytic cell. By adjusting the output voltage of the boost DC / DC converter, the high-voltage side voltage is stabilized at the target value, so that the regulating electrolytic cell can absorb the fluctuation part of the photovoltaic power.

[0012] Furthermore, the MPPT control is implemented based on the perturbation observation method or the incremental conductance method.

[0013] Furthermore, the rated power point of the power-type electrolyzer is determined by the efficiency-current characteristic curve of the electrolyzer, and the low-voltage side current setting value is dynamically configured based on the optimal efficiency point of the curve.

[0014] Furthermore, the input power range of the adjustable electrolyzer covers the maximum fluctuation range of photovoltaic output power, and its high-voltage side voltage target value is dynamically adjusted according to the real-time power balance requirements of the system.

[0015] Furthermore, the power distribution unit is also configured to dynamically allocate the ratio of power-type electrolytic cells to regulating electrolytic cells based on the real-time changes in photovoltaic output power.

[0016] Furthermore, the electrolytic cell also includes a shutdown tank. When the photovoltaic power exceeds the adjustment capacity of the adjustable electrolytic cell, the system stability is maintained by starting or stopping some shutdown tanks or switching the electrolytic cell operation mode. The electrolytic cell operation modes include power type and adjustment type.

[0017] Furthermore, the MPPT control, constant current control of the power-type electrolytic cell, and constant voltage control of the regulating electrolytic cell are achieved through independent closed loops, and the three work together through bus communication or a central controller.

[0018] Furthermore, the control logic of the boost DC / DC converter is bound to the type of electrolytic cell; the power type electrolytic cell corresponds to the low-voltage side current closed loop, and the regulating type electrolytic cell corresponds to the high-voltage side voltage closed loop.

[0019] Furthermore, the output power of the plurality of photovoltaic modules is controlled by a plurality of boost DC / DC converters.

[0020] Secondly, the present invention provides a control method applicable to the off-grid green electricity-to-hydrogen coupling control system described in any of the foregoing claims, comprising:

[0021] MPPT control is performed on each photovoltaic module to maximize output power;

[0022] The output power is distributed to the power electrolyzer, and the duty cycle of the boost DC / DC converter is adjusted to stabilize the low-voltage side current at the set value so that the power electrolyzer always operates at the rated power point.

[0023] The output power is distributed to the regulating electrolyzer, and the output voltage of the boost DC / DC converter is adjusted to stabilize the high-voltage side voltage at the target value, so that the regulating electrolyzer absorbs the fluctuation part of the photovoltaic power.

[0024] Furthermore, the MPPT control is implemented based on the perturbation observation method or the incremental conductance method.

[0025] Furthermore, the rated power point of the power-type electrolyzer is determined by the efficiency-current characteristic curve of the electrolyzer, and the low-voltage side current setting value is dynamically configured based on the optimal efficiency point of the curve.

[0026] Furthermore, the input power range of the adjustable electrolyzer covers the maximum fluctuation range of photovoltaic output power, and its high-voltage side voltage target value is dynamically adjusted according to the real-time power balance requirements of the system.

[0027] Furthermore, the method also includes: dynamically allocating the ratio of power-type electrolytic cells to regulating electrolytic cells based on the real-time changes in photovoltaic output power.

[0028] Furthermore, the method also includes: when the photovoltaic power exceeds the regulation capacity of the regulating electrolytic cell, maintaining system stability by starting or stopping some of the shut-down cells or switching the electrolytic cell operation mode, wherein the electrolytic cell operation mode includes power type and regulation type.

[0029] Furthermore, the method also includes: implementing MPPT control, constant current control of power-type electrolytic cells, and constant voltage control of regulating electrolytic cells through independent closed loops, with the three working together through bus communication or a central controller.

[0030] Furthermore, the method also includes: binding the control logic of the boost DC / DC converter to the type of electrolytic cell, with the power type electrolytic cell corresponding to the low-voltage side current closed loop and the regulating type electrolytic cell corresponding to the high-voltage side voltage closed loop.

[0031] Furthermore, the method also includes controlling the output power of multiple photovoltaic modules through multiple boost DC / DC converters.

[0032] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0033] This invention provides an off-grid green electricity hydrogen production hydrogen coupling control system and method. By dividing the electrolyzer into a power-type electrolyzer and a regulating electrolyzer, power allocation is optimized to ensure that the power-type electrolyzer always operates at its highest efficiency point, while the regulating electrolyzer handles the photovoltaic power fluctuations and acts as an energy storage function, ensuring system voltage stability and improving hydrogen production efficiency. This system does not rely on energy storage devices and, through reasonable power allocation and control strategies, can still achieve a stable hydrogen production process even when photovoltaic power fluctuates. This invention is applicable to hydrogen production systems with multiple photovoltaic cells and multiple electrolyzers, and has advantages such as significantly improved efficiency, reduced losses, and ensured system stability, demonstrating high practical value and economic benefits. Attached Figure Description

[0034] Figure 1 shows the topology of hydrogen production using multiple electrolyzers.

[0035] Figure 2 is a topology diagram of hydrogen production using multiple photovoltaic cells and multiple electrolyzers.

[0036] Figure 3 shows the power distribution of new energy sources during fluctuations.

[0037] Figure 4 shows the operating efficiency of the electrolyzer.

[0038] Figure 5 is a control block diagram of a power-type electrolytic cell;

[0039] Figure 6 is a control block diagram of an adjustable electrolyzer. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0041] Example 1: This example introduces an off-grid green electricity hydrogen production hydrogen-electric coupling control system, including:

[0042] Multiple photovoltaic modules, each connected to an electrolytic cell via a boost DC / DC converter, are provided with maximum power point tracking (MPPT) control to maximize output power.

[0043] Multiple electrolytic cells, including power-type electrolytic cells and adjustable electrolytic cells;

[0044] The power distribution unit includes:

[0045] The power electrolyzer control module is used to distribute the output power to the power electrolyzer. By adjusting the duty cycle of the boost DC / DC converter, the low-voltage side current is stabilized at the set value so that the power electrolyzer always operates at the rated power point.

[0046] The regulating electrolytic cell control module is used to distribute the output power to the regulating electrolytic cell. By adjusting the output voltage of the boost DC / DC converter, the high-voltage side voltage is stabilized at the target value, so that the regulating electrolytic cell can absorb the fluctuation part of the photovoltaic power.

[0047] The following description, in conjunction with a preferred embodiment, illustrates the content involved in the above embodiments.

[0048] In existing green electricity-to-hydrogen systems, a boost DC / DC converter is used on the source side, and maximum power point tracking (MPPT) control is employed to ensure that the photovoltaic output voltage is maintained at the optimal power point. The load-side DC-DC converter controls the high-voltage side voltage (U... H This system dynamically adjusts the load power based on changes in photovoltaic output power to achieve energy balance. Under stable hydrogen production conditions, this control scheme maximizes the utilization of photovoltaic energy while enabling high-voltage power transmission and reducing energy transmission losses. However, although existing systems can achieve the maximum output power at the photovoltaic end, the electrolyzer typically does not operate at its optimal efficiency point.

[0049] To address the aforementioned issues, this invention proposes a multi-electrolyzer hydrogen production model suitable for situations where photovoltaic system output power fluctuates significantly. The typical topology of this model is shown in Figure 1. Actual photovoltaic output exhibits power fluctuations (as shown in Figure 3(a)). Existing solutions distribute the photovoltaic output power evenly across two electrolyzers (as shown in Figure 3b), with both electrolyzers sharing the burden of these fluctuations. The advantage of this solution lies in its simple and easy-to-implement control strategy; stable system operation can be achieved by adding a droop element to the DC / DC control strategy on the load side. However, in this case, neither electrolyzer operates at its optimal efficiency point, resulting in low electrolyzer efficiency, especially at lower power (current) levels, where the efficiency drops dramatically (as shown in Figure 4).

[0050] This embodiment proposes to divide the electrolyzer into a power-type electrolyzer and a regulating electrolyzer. The power-type electrolyzer always maintains the optimal efficiency point (usually at the rated power point), while the regulating electrolyzer is used to balance the fluctuation part of photovoltaic energy (as shown in Figure 3(c)).

[0051] In this scheme, to ensure that the power-type electrolyzer always operates at its optimal efficiency point, DC / DC1 needs to adopt a constant low-voltage side current control strategy to maintain the low-voltage side current I. L The control strategy is constant. The block diagram is shown in Figure 5. Under constant temperature conditions, the power-type electrolyzer behaves as a constant power load. The regulating electrolyzer is responsible for handling fluctuations in photovoltaic power, and DC / DC2 uses a constant high-voltage side voltage U. H The control strategy is shown in Figure 6.

[0052] In this scheme, the photovoltaic power source provides maximum power, the power-type electrolyzer operates at constant power, and the remaining fluctuating power is handled by the regulating electrolyzer. The regulating electrolyzer plays a role in maintaining system voltage stability and, through its voltage stabilization, ensures stable maximum power point tracking (MPPT) of the photovoltaic system and stable low-voltage side current control of the power-type electrolyzer. As the system's balancing node, the regulating electrolyzer is crucial to system stability.

[0053] The solution in this embodiment requires no energy storage configuration. Under the condition of achieving stable hydrogen production, it can ensure the MPPT control of photovoltaics and high-voltage power transmission, while keeping part of the load operating at the optimal efficiency point. The generalization of this model can be further applied to actual photovoltaic hydrogen production systems with multiple photovoltaic cells and multiple electrolyzers, and the specific topology is shown in Figure 2.

[0054] In the multi-photovoltaic, multi-electrolyzer hydrogen production system shown in Figure 2, m photovoltaic modules are connected to the source side, and the DC / DC converter of each photovoltaic module adopts maximum power point tracking control. The load side has n electrolyzers, which can be divided into three categories: off-line electrolyzers, power-type electrolyzers, and regulating electrolyzers.

[0055] In this system, when the number of power-type electrolyzers is close to the total number of operating electrolyzers, the hydrogen production efficiency is high, but the system regulation performance is poor. In extreme cases, the power deficit may exceed the maximum regulation capacity of the regulating electrolyzers, leading to system voltage instability and subsequent instability. Conversely, when the number of power-type electrolyzers is small, the system regulation performance is strong, but the hydrogen production efficiency is low.

[0056] Therefore, it is necessary to increase the number of regulated electrolyzers. The number of regulated electrolyzers is closely related to the accuracy of photovoltaic output prediction and the start-up and shutdown speed of the electrolyzers. The more accurate the photovoltaic output power prediction, or the faster the start-up, shutdown, and regulation speed of the electrolyzers, the fewer regulated electrolyzers are required, and the more electrolyzers can operate as power-type electrolyzers. Conversely, the more regulated electrolyzers are required, the fewer electrolyzers can operate as power-type electrolyzers. In extreme cases, the system consists entirely of regulated electrolyzers, degenerating into a fluctuating power-sharing operation mode.

[0057] Example 2: This example provides a control method applicable to the off-grid green electricity hydrogen production hydrogen-electric coupling control system described in any of Examples 1, comprising:

[0058] MPPT control is performed on each photovoltaic module to maximize output power;

[0059] The output power is distributed to the power electrolyzer, and the duty cycle of the boost DC / DC converter is adjusted to stabilize the low-voltage side current at the set value so that the power electrolyzer always operates at the rated power point.

[0060] The output power is distributed to the regulating electrolyzer, and the output voltage of the boost DC / DC converter is adjusted to stabilize the high-voltage side voltage at the target value, so that the regulating electrolyzer absorbs the fluctuation part of the photovoltaic power.

[0061] The MPPT control is implemented based on the perturbation observation method or the incremental conductance method.

[0062] The rated power point of the power-type electrolyzer is determined by the efficiency-current characteristic curve of the electrolyzer, and the low-voltage side current setting value is dynamically configured based on the optimal efficiency point of the curve.

[0063] The input power range of the adjustable electrolyzer covers the maximum fluctuation range of photovoltaic output power, and its high-voltage side voltage target value is dynamically adjusted according to the real-time power balance requirements of the system.

[0064] The method further includes: dynamically allocating the ratio of power-type electrolytic cells to regulating electrolytic cells based on the real-time changes in photovoltaic output power.

[0065] The method further includes: when the photovoltaic power exceeds the regulation capacity of the regulating electrolyzer, maintaining system stability by starting or stopping some of the shut-down cells or switching the electrolyzer operating mode, wherein the electrolyzer operating mode includes power type and regulation type.

[0066] The method further includes: implementing MPPT control, constant current control of power-type electrolytic cells, and constant voltage control of regulating electrolytic cells through independent closed loops, with the three working together through bus communication or a central controller.

[0067] The method further includes binding the control logic of the boost DC / DC converter to the type of electrolytic cell, with the power type electrolytic cell corresponding to the low-voltage side current closed loop and the regulating type electrolytic cell corresponding to the high-voltage side voltage closed loop.

[0068] The method further includes controlling the output power of multiple photovoltaic modules through multiple boost DC / DC converters.

[0069] Through the above optimization methods, this embodiment can effectively improve the efficiency of the green electric hydrogen production system and achieve stable and sustainable hydrogen production without relying on energy storage.

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An off-grid green electricity hydrogen production hydrogen-electric coupling control system, characterized in that... include: Multiple photovoltaic modules, each connected to an electrolytic cell via a boost DC / DC converter, are provided with maximum power point tracking (MPPT) control to maximize output power. Multiple electrolytic cells, including power-type electrolytic cells and adjustable electrolytic cells; The power distribution unit includes: The power electrolyzer control module is used to distribute the output power to the power electrolyzer. By adjusting the duty cycle of the boost DC / DC converter, the low-voltage side current is stabilized at the set value so that the power electrolyzer always operates at the rated power point. The regulating electrolytic cell control module is used to distribute the output power to the regulating electrolytic cell. By adjusting the output voltage of the boost DC / DC converter, the high-voltage side voltage is stabilized at the target value, so that the regulating electrolytic cell can absorb the fluctuation part of the photovoltaic power.

2. The off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 1, characterized in that, The MPPT control is implemented based on the perturbation observation method or the incremental conductance method.

3. The off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 1, characterized in that, The rated power point of the power-type electrolyzer is determined by the efficiency-current characteristic curve of the electrolyzer, and the low-voltage side current setting value is dynamically configured based on the optimal efficiency point of the curve.

4. The off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 1, characterized in that, The input power range of the adjustable electrolyzer covers the maximum fluctuation range of photovoltaic output power, and its high-voltage side voltage target value is dynamically adjusted according to the real-time power balance requirements of the system.

5. The off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 1, characterized in that, The power distribution unit is also configured to dynamically allocate the ratio of power-type electrolytic cells to regulating electrolytic cells based on the real-time changes in photovoltaic output power.

6. The off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 1, characterized in that, The electrolytic cell also includes a shutdown tank. When the photovoltaic power exceeds the regulation capacity of the adjustable electrolytic cell, the system stability is maintained by starting or stopping some shutdown tanks or switching the electrolytic cell operation mode. The electrolytic cell operation modes include power type and regulation type.

7. The off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 1, characterized in that, The MPPT control, constant current control of the power-type electrolyzer, and constant voltage control of the regulating electrolyzer are achieved through independent closed loops. The three work together through bus communication or a central controller.

8. The off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 1, characterized in that, The control logic of the boost DC / DC converter is bound to the type of electrolytic cell. The power type electrolytic cell corresponds to the low-voltage side current closed loop, and the regulating type electrolytic cell corresponds to the high-voltage side voltage closed loop.

9. The off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 1, characterized in that, The output power of the multiple photovoltaic modules is controlled by multiple boost DC / DC converters.

10. A control method applicable to the off-grid green electricity hydrogen production hydrogen-electric coupling control system according to any one of claims 1-9, characterized in that, include: MPPT control is performed on each photovoltaic module to maximize output power; The output power is distributed to the power electrolyzer, and the duty cycle of the boost DC / DC converter is adjusted to stabilize the low-voltage side current at the set value so that the power electrolyzer always operates at the rated power point. The output power is distributed to the regulating electrolyzer, and the output voltage of the boost DC / DC converter is adjusted to stabilize the high-voltage side voltage at the target value, so that the regulating electrolyzer absorbs the fluctuation part of the photovoltaic power.

11. The control method of the off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 10, characterized in that, The MPPT control is implemented based on the perturbation observation method or the incremental conductance method.

12. The control method of the off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 10, characterized in that, The rated power point of the power-type electrolyzer is determined by the efficiency-current characteristic curve of the electrolyzer, and the low-voltage side current setting value is dynamically configured based on the optimal efficiency point of the curve.

13. The control method of the off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 10, characterized in that, The input power range of the adjustable electrolyzer covers the maximum fluctuation range of photovoltaic output power, and its high-voltage side voltage target value is dynamically adjusted according to the real-time power balance requirements of the system.

14. The control method of the off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 10, characterized in that, The method further includes: dynamically allocating the ratio of power-type electrolytic cells to regulating electrolytic cells based on the real-time changes in photovoltaic output power.

15. The control method of the off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 10, characterized in that, The method further includes: when the photovoltaic power exceeds the regulation capacity of the regulating electrolyzer, maintaining system stability by starting or stopping some of the shut-down cells or switching the electrolyzer operating mode, wherein the electrolyzer operating mode includes power type and regulation type.

16. The control method of the off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 10, characterized in that, The method further includes: implementing MPPT control, constant current control of power-type electrolytic cells, and constant voltage control of regulating electrolytic cells through independent closed loops, with the three working together through bus communication or a central controller.

17. The control method of the off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 10, characterized in that, The method further includes binding the control logic of the boost DC / DC converter to the type of electrolytic cell, with the power type electrolytic cell corresponding to the low-voltage side current closed loop and the regulating type electrolytic cell corresponding to the high-voltage side voltage closed loop.

18. The control method of the off-grid green electricity hydrogen production hydrogen-electric coupling control system according to claim 10, characterized in that, The method further includes controlling the output power of multiple photovoltaic modules through multiple boost DC / DC converters.

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