Off-grid type green electricity hydrogen production hydrogen-electricity coupling control system and method

Abstract

The invention discloses an off-grid type green electricity hydrogen production hydrogen-electricity coupling control system and method, and belongs to the technical field of green electricity hydrogen production, and the method comprises the steps: executing MPPT control on each photovoltaic module to maximize the output power; distributing the output power to the power type electrolytic cell, and stabilizing the low-voltage side current at a set value by adjusting the duty ratio of the boost DC / DC converter, so that the power type electrolytic cell always operates at a rated power point; the output power is distributed into the adjusting type electrolytic cell, the output voltage of the boosting type DC / DC converter is adjusted, the voltage of the high-voltage side is stabilized at a target value, the adjusting type electrolytic cell absorbs the fluctuation part of the photovoltaic power, the efficiency of the green electric power hydrogen production system can be effectively improved, and the energy storage efficiency is improved without depending on energy storage. And stable and sustainable hydrogen production is realized.

Description

Technical Field

[0001] The present invention relates to an off-grid green power-to-hydrogen hydrogen-electricity coupling control system and method, belonging to the technical field of green power-to-hydrogen. Background Art

[0002] With the continuous advancement of large-scale new energy access, the problem of source-load imbalance has become increasingly prominent. As an effective means to solve this problem, green power-to-hydrogen has achieved rapid development in recent years. Green power-to-hydrogen can be divided into off-grid and grid-connected types. Although traditional grid-connected hydrogen production uses the power grid as the power source, it cannot ensure that the power is completely from green energy and cannot obtain green power certification (green certificate), so hydrogen and its derivatives cannot be sold in the international market.

[0003] In contrast, off-grid hydrogen production has a simpler structure, usually adopting a fully DC system, reducing the AC-DC conversion link, thereby improving the overall efficiency of the system. In some scenarios lacking strong grid connection conditions, such as new energy bases in desert or desert areas, off-grid green power-to-hydrogen has particular advantages. With the large-scale access of new energy, off-grid green power-to-hydrogen will be more widely used in the future. However, to achieve this goal, multiple technical bottlenecks still need to be broken through, especially in improving system efficiency, stability and sustainability. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide an off-grid green power-to-hydrogen hydrogen-electricity coupling control system and method, which optimize the working state of the electrolyzer to improve hydrogen production efficiency and solve the problem that the electrolyzer in the existing green power-to-hydrogen system fails to operate at the optimal efficiency point.

[0005] To achieve the above object, the present invention is implemented by the following technical solutions:

[0006] In the first aspect, the present invention provides an off-grid green power-to-hydrogen hydrogen-electricity coupling control system, including:

[0007] Multiple photovoltaic modules, each photovoltaic module is connected to the electrolyzer through a boost-type DC / DC converter, and the photovoltaic module is controlled by maximum power point tracking (MPPT) to maximize the output power;

[0008] Multiple electrolyzers, including power-type electrolyzers and regulating-type electrolyzers;

[0009] A power distribution unit, including:

[0010] A power-type electrolyzer control module, which is used to distribute the output power to the power-type electrolyzers. By adjusting the duty cycle of the boost-type DC / DC converter, the current on the low-voltage side is stabilized at a set value, so that the power-type electrolyzers always operate at the rated power point;

[0011] The regulated electrolyzer control module is used to distribute the output power to the regulated electrolyzer. By adjusting the output voltage of the boost DC / DC converter, the high-voltage side voltage is stabilized at the target value, enabling the regulated electrolyzer to absorb the fluctuating 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 electrolyzer efficiency-current characteristic curve, and the low-voltage side current set value is dynamically configured based on the optimal efficiency point of this curve.

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

[0015] Furthermore, the power distribution unit is also configured to dynamically distribute the number ratio of the power-type electrolyzer and the regulated electrolyzer according to the real-time change of the photovoltaic output power.

[0016] Furthermore, the electrolyzer also includes a shutdown cell. When the photovoltaic power exceeds the regulation capacity of the regulated electrolyzer, the system stability is maintained by starting or stopping some shutdown cells or switching the electrolyzer operation mode. The electrolyzer operation modes include power type and regulated type.

[0017] Furthermore, the MPPT control, the constant current control of the power-type electrolyzer, and the constant voltage control of the regulated electrolyzer are realized 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 electrolyzer type. The power-type electrolyzer corresponds to the low-voltage side current closed loop, and the regulated electrolyzer corresponds to the high-voltage side voltage closed loop.

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

[0020] In a second aspect, the present invention provides a control method applicable to the off-grid green power-to-hydrogen and hydrogen-electricity coupling control system described in any one of the foregoing items, including:

[0021] Performing MPPT control on each photovoltaic module to maximize the output power;

[0022] Distributing the output power to the power-type 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-type electrolyzer always operates at the rated power point;

[0023] The output power is distributed to the regulated electrolyzer. By adjusting the output voltage of the boost DC / DC converter, the high-voltage side voltage is stabilized at the target value, enabling the regulated electrolyzer to absorb the fluctuating 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 electrolyzer efficiency-current characteristic curve, and the low-voltage side current set value is dynamically configured based on the optimal efficiency point of this curve.

[0026] Furthermore, the input power range of the regulated electrolyzer covers the maximum fluctuation amplitude of the 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 further includes: dynamically allocating the quantity ratio of the power-type electrolyzer and the regulated electrolyzer according to the real-time change of the photovoltaic output power.

[0028] Furthermore, the method further includes: when the photovoltaic power exceeds the regulation capacity of the regulated electrolyzer, maintaining the system stability by starting and stopping some shutdown cells or switching the operation mode of the electrolyzer. The operation modes of the electrolyzer include power type and regulation type.

[0029] Furthermore, the method further includes: implementing the MPPT control, the constant current control of the power-type electrolyzer, and the constant voltage control of the regulated electrolyzer through independent closed loops, and the three work together through bus communication or a central controller.

[0030] Furthermore, the method further includes: binding the control logic of the boost DC / DC converter to the type of electrolyzer. The power-type electrolyzer corresponds to the low-voltage side current closed loop, and the regulated electrolyzer corresponds to the high-voltage side voltage closed loop.

[0031] Furthermore, the method further 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:

[0033] The present invention provides an off-grid green power-to-hydrogen hydrogen-electricity coupling control system and method. By dividing the electrolyzer into a power-type electrolyzer and a regulating-type electrolyzer and optimizing the power distribution, the power-type electrolyzer is always operated at the highest efficiency point, while the regulating-type electrolyzer undertakes the part of the photovoltaic power fluctuation and functions as energy storage to ensure the system voltage stability and improve the hydrogen production efficiency. This system does not rely on energy storage devices. Through reasonable power distribution and control strategies, a stable hydrogen production process can still be achieved during photovoltaic power fluctuations. The invention is applicable to hydrogen production systems with multiple photovoltaics and multiple electrolyzers, and has the advantages of significantly improving efficiency, reducing losses, and ensuring system stability, with high practical value and economic benefits. Description of the Drawings

[0034] Figure 1 It is a topology diagram of hydrogen production with multiple electrolyzers;

[0035] Figure 2 It is a topology diagram of hydrogen production with multiple photovoltaics and multiple electrolyzers;

[0036] Figure 3 It is a diagram of new energy fluctuating power distribution;

[0037] Figure 4 It is an operating efficiency diagram of the electrolyzer;

[0038] Figure 5 It is a control block diagram of the power-type electrolyzer;

[0039] Figure 6 It is a control block diagram of the regulating-type electrolyzer. Detailed Embodiments

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

[0041] Embodiment 1. This embodiment introduces an off-grid green power-to-hydrogen hydrogen-electricity coupling control system, including:

[0042] Multiple photovoltaic modules, each photovoltaic module is connected to the electrolyzer through a boost-type DC / DC converter, and the photovoltaic module is controlled by maximum power point tracking (MPPT) to maximize the output power;

[0043] Multiple electrolyzers, the electrolyzers include a power-type electrolyzer and a regulating-type electrolyzer;

[0044] A power distribution unit, including:

[0045] A power-type electrolyzer control module, used to distribute the output power to the power-type electrolyzer, and by adjusting the duty cycle of the boost-type DC / DC converter, the current on the low-voltage side is stabilized at a set value, so that the power-type electrolyzer always operates at the rated power point;

[0046] A regulated electrolyzer control module is used to distribute the output power to the regulated electrolyzer. By adjusting the output voltage of the boost DC / DC converter, the high-voltage side voltage is stabilized at the target value, enabling the regulated electrolyzer to absorb the fluctuating part of the photovoltaic power.

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

[0048] In the existing green power hydrogen production system, a boost DC / DC converter is adopted on the source side, and through the maximum power point tracking (MPPT) control, it is ensured that the photovoltaic output voltage is maintained at the optimal power point. The DC-DC converter on the load side controls the high-voltage side voltage (U H ), and dynamically adjusts the load power according to the change of the photovoltaic output power, thereby achieving the energy balance of the system. Under the condition of stable hydrogen production, this control scheme can maximize the utilization of photovoltaic energy, while realizing high-voltage power transmission and reducing energy transmission losses. However, although the existing system can reach the maximum output power at the photovoltaic end, the electrolyzer usually does not operate at the optimal efficiency point.

[0049] To solve the above problems, the present invention proposes a multi-electrolyzer hydrogen production model, which is applicable to the situation where the output power of the photovoltaic system fluctuates greatly. The typical topological structure of this model is as Figure 1 shown. There are power fluctuations in the actual photovoltaic output (as shown in Figure 3 (a)). The existing scheme evenly distributes the photovoltaic output power to two electrolyzers (as shown in Figure 3 b)), and the two electrolyzers jointly bear the fluctuations of the photovoltaic power. The advantage of this scheme is that the control strategy is simple and easy to implement, and the stable operation of the system can be achieved by adding a droop link to the DC / DC control strategy on the load side. However, in this case, neither of the two electrolyzers operates at the optimal efficiency point, resulting in a low operating efficiency of the electrolyzer. Especially when the power (current) is low, the efficiency of the electrolyzer drops significantly (as shown in Figure 4 ).

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

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

[0052] In this scheme, the photovoltaic power supply provides the maximum power. The power-type electrolyzer operates at a constant power, and the remaining fluctuating power is borne by the regulating electrolyzer. The regulating electrolyzer plays a role in maintaining the stability of the system voltage. Under its voltage stabilizing effect, it ensures the stability of the maximum power point tracking (MPPT) of the photovoltaic and the current control of the low-voltage side of the power-type electrolyzer. As the balance node of the system, the regulating electrolyzer is crucial for the stability of the system.

[0053] The scheme of this embodiment does not require energy storage configuration. Under the condition of realizing stable hydrogen production, it can ensure the MPPT control of the photovoltaic and high-voltage power transmission, while keeping some loads operating at the optimal efficiency point. The popularization of this model can be further applied to the actual photovoltaic hydrogen production system with multiple photovoltaics and multiple electrolyzers. The specific topological structure is as Figure 2 shown in the figure.

[0054] Assume that in Figure 2 the multi-photovoltaic and multi-electrolyzer hydrogen production system shown in the figure, m photovoltaic modules are connected to the source side, and the DC / DC converters of each photovoltaic module adopt the maximum power point tracking control. There are n electrolyzers on the load side, and these electrolyzers can be divided into three categories: shutdown 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 relatively high, but the system regulation performance is poor. In extreme cases, the power deficit may exceed the maximum regulation capacity of the regulating electrolyzer, resulting in the inability to stabilize the system voltage and further instability. On the contrary, 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 regulating electrolyzers. The number of regulating electrolyzers is closely related to the prediction accuracy of the photovoltaic output and the start-stop speed of the electrolyzers. When the prediction of the photovoltaic output power is more accurate, or the start-stop and regulation speed of the electrolyzers is faster, the number of required regulating electrolyzers is less, and the number of electrolyzers that can operate as power-type electrolyzers is more. On the contrary, the number of required regulating electrolyzers is more, and the number of electrolyzers that can operate as power-type electrolyzers is less. In extreme cases, the system consists of all regulating electrolyzers and degrades into a fluctuating power equalization operation mode.

[0057] Embodiment 2. This embodiment provides a control method applicable to the off-grid green power hydrogen production hydrogen-electricity coupling control system described in any one of Embodiments 1, including:

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

[0059] The output power is distributed to the power type electrolyzer. By adjusting the duty ratio of the boost DC / DC converter, the current on the low voltage side is stabilized at a set value, so that the power type electrolyzer always operates at the rated power point;

[0060] The output power is distributed to the regulated electrolyzer. By adjusting the output voltage of the boost DC / DC converter, the voltage on the high voltage side is stabilized at a target value, so that the regulated electrolyzer absorbs the fluctuating 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 electrolyzer efficiency-current characteristic curve, and the set value of the current on the low voltage side is dynamically configured based on the optimal efficiency point of this curve.

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

[0064] The method further includes: dynamically allocating the quantity ratio of the power type electrolyzer and the regulated electrolyzer according to the real-time change of the photovoltaic output power.

[0065] The method further includes: when the photovoltaic power exceeds the regulation capacity of the regulated electrolyzer, maintaining the system stability by starting and stopping some shutdown electrolyzers or switching the operation mode of the electrolyzer. The operation modes of the electrolyzer include power type and regulated type.

[0066] The method further includes: realizing the MPPT control, the constant current control of the power type electrolyzer, and the constant voltage control of the regulated electrolyzer through independent closed loops, and the three work 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 electrolyzer. The power type electrolyzer corresponds to the closed loop of the current on the low voltage side, and the regulated electrolyzer corresponds to the closed loop of the voltage on the high voltage side.

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

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

[0070] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. An off-grid green electricity hydrogen production hydrogen-electricity coupling control system, characterized in that include: A plurality of photovoltaic modules, each photovoltaic module is connected to the electrolyzer via a step-up DC / DC converter, and the photovoltaic modules are controlled by maximum power point tracking (MPPT) to maximize output power; A plurality of electrolytic cells, wherein the electrolytic cells include power type electrolytic cells and regulating type electrolytic cells; A power distribution unit, comprising: The power electrolyzer control module is used to distribute the output power to the power electrolyzer, and stabilize the low-voltage side current at a set value by adjusting the duty cycle of the boost DC / DC converter, so that the power electrolyzer always operates at the rated power point; The regulated electrolyzer control module is used to distribute the output power to the regulated electrolyzer. 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 regulated electrolyzer absorbs the fluctuating part of the photovoltaic power.

2. The off-grid green electricity hydrogen production hydrogen-electricity coupling control system according to claim 1 is 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-electricity coupling control system according to claim 1 is characterized in that: The rated power point of the power-type electrolyzer is determined by the electrolyzer efficiency-current characteristic curve, 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-electricity coupling control system according to claim 1 is characterized in that: The input power range of the adjustable electrolyzer covers the maximum fluctuation amplitude of the photovoltaic output power, and its high-voltage side voltage target value is dynamically adjusted according to the real-time power balance demand of the system.

5. The off-grid green electricity hydrogen production hydrogen-electricity coupling control system according to claim 1 is characterized in that: The power distribution unit is also configured to dynamically distribute the quantity ratio of the power-type electrolyzers and the regulating-type electrolyzers according to the real-time changes in the photovoltaic output power.

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

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

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

9. The off-grid green electricity hydrogen production hydrogen-electricity coupling control system according to claim 1 is characterized in that: The output power of the plurality of photovoltaic modules is controlled by a plurality of step-up DC / DC converters.

10. A control method applicable to the off-grid green electricity hydrogen production hydrogen-electricity coupling control system according to any one of claims 1 to 9, characterized in that: include: Perform MPPT control 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 fluctuating part of the photovoltaic power.

11. The control method of the off-grid green electricity hydrogen production hydrogen-electricity coupling control system according to claim 10 is 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-electricity coupling control system according to claim 10, characterized in that: The rated power point of the power-type electrolyzer is determined by the electrolyzer efficiency-current characteristic curve, 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-electricity coupling control system according to claim 10, characterized in that: The input power range of the adjustable electrolyzer covers the maximum fluctuation amplitude of the photovoltaic output power, and its high-voltage side voltage target value is dynamically adjusted according to the real-time power balance demand of the system.

14. The control method of the off-grid green electricity hydrogen production hydrogen-electricity coupling control system according to claim 10, characterized in that: The method further includes: dynamically allocating the quantity ratio of the power-type electrolyzers and the regulating-type electrolyzers according to the real-time change of the photovoltaic output power.

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

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

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

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

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