Photovoltaic hydrogen production power supply with energy storage and current transformation capabilities

Abstract

The invention discloses a photovoltaic hydrogen production power supply with energy storage and current transformation capabilities, and relates to the technical field of hydrogen production, a first input end of the photovoltaic hydrogen production power supply is connected with a photovoltaic power generation system, a second input end of the photovoltaic hydrogen production power supply is connected with an energy storage module, and an output end of the photovoltaic hydrogen production power supply is connected with an electrolytic cell; the photovoltaic power generation system supplies power to the electrolytic cell through the photovoltaic hydrogen production power supply, and when the input voltage Uin of the photovoltaic power generation system is larger than the preset voltage Uref and the energy storage capacity of the energy storage module is not full, the photovoltaic hydrogen production power supply controls the photovoltaic power generation system to charge the energy storage module so as to absorb the excess power of the photovoltaic power generation system; and when the input voltage Uin of the photovoltaic power generation system is smaller than the preset voltage Uref and the energy storage module has the energy storage capacity, the photovoltaic hydrogen production power supply controls the energy storage module to supply power to the electrolytic cell. According to the photovoltaic hydrogen production power supply, cross-time allocation of energy is realized through energy storage conversion, and the utilization rate of photovoltaic energy is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production, and in particular to a photovoltaic hydrogen production power supply with energy storage and variable current capabilities. Background Art

[0002] Currently, as an efficient and clean energy medium, hydrogen energy has attracted more and more attention and has broad application prospects. Photovoltaic electrolytic water hydrogen production combines solar power generation and electrolytic water hydrogen production to achieve local consumption of new energy. At present, photovoltaic hydrogen production has two forms: off-grid and grid-connected. Among them, direct photovoltaic coupling hydrogen production is a widely used off-grid hydrogen production scheme, which uses a photovoltaic power generation system to directly supply direct current to a hydrogen production station for electrolytic water hydrogen production. However, the hydrogen production capacity of this photovoltaic hydrogen production scheme is limited by light, and hydrogen production can only be carried out during the day when there is light. Moreover, when there is excessive light, all energy cannot be consumed, resulting in energy waste. Summary of the Invention

[0003] In view of the above problems and technical requirements, the inventor of the present invention has proposed a photovoltaic hydrogen production power supply with energy storage and variable current capabilities. The technical solution of the present invention is as follows:

[0004] A photovoltaic hydrogen production power supply with energy storage and variable current capabilities, wherein a first input end of the photovoltaic hydrogen production power supply is connected to a photovoltaic power generation system, a second input end of the photovoltaic hydrogen production power supply is connected to an energy storage module, and an output end of the photovoltaic hydrogen production power supply is connected to an electrolytic cell;

[0005] The photovoltaic power generation system supplies power to the electrolytic cell through the photovoltaic hydrogen production power supply. When the input voltage U in of the photovoltaic power generation system is greater than a preset voltage U ref and the energy storage capacity of the energy storage module is not full, the photovoltaic hydrogen production power supply controls the photovoltaic power generation system to charge the energy storage module to absorb the excess power of the photovoltaic power generation system;

[0006] When the input voltage U in of the photovoltaic power generation system is less than a preset voltage U ref and the energy storage module has energy storage capacity, the photovoltaic hydrogen production power supply controls the energy storage module to supplement power to the electrolytic cell.

[0007] A further technical solution thereof is that the photovoltaic hydrogen production power supply includes a controller, a medium-voltage bus, a first DC / DC converter, a second DC / DC converter, and a third DC / DC converter;

[0008] An input end of the first DC / DC converter is used as the first input end of the photovoltaic hydrogen production power supply and is connected to the photovoltaic power generation system, and an output end of the first DC / DC converter is connected to the medium-voltage bus;

[0009] One end of the second DC / DC converter is connected to the energy storage module as the second input end of the photovoltaic hydrogen production power supply, and the other end of the second DC / DC converter is connected to the medium-voltage bus;

[0010] The input end of the third DC / DC converter is connected to the medium-voltage bus, and the output end of the third DC / DC converter is connected to the electrolyzer as the output end of the photovoltaic hydrogen production power supply;

[0011] The medium-voltage bus, the first DC / DC converter, the second DC / DC converter and the third DC / DC converter are all connected to the controller.

[0012] A further technical solution thereof is that the first DC / DC converter outputs an input voltage U to the medium-voltage bus in , and the controller samples the input voltage U in and compares the input voltage U in with a preset voltage U ref ;

[0013] When the input voltage U in is greater than the preset voltage U ref and the energy storage capacity of the energy storage module is not full, the controller controls the medium-voltage bus to charge the energy storage module through the second DC / DC converter, so that the medium-voltage bus voltage U mid is equal to the preset voltage U ref .

[0014] A further technical solution thereof is that when the input voltage U in is less than the preset voltage U ref , and the energy storage module has energy storage capacity, the controller controls the energy storage module to supply power to the medium-voltage bus through the second DC / DC converter, so that the medium-voltage bus voltage U mid is equal to the preset voltage U ref .

[0015] A further technical solution thereof is that when the input voltage U in is greater than the preset voltage U ref and the energy storage capacity of the energy storage module is full, the controller controls the second DC / DC converter to stop working and controls the medium-voltage bus voltage U mid to follow the input voltage U in .

[0016] A further technical solution thereof is that when the input voltage U in is less than the preset voltage U ref , and the energy storage module has no energy storage capacity, the controller compares the input voltage U in with the minimum starting voltage U min ;

[0017] When the input voltage Uin When it is less than the minimum starting voltage U min , the controller controls the medium-voltage bus voltage U mid to follow the input voltage U in , and controls the medium-voltage bus to charge the energy storage module through the second DC / DC converter;

[0018] When the input voltage U in is greater than or equal to the minimum starting voltage U min , the controller controls the second DC / DC converter to stop working, and controls the medium-voltage bus voltage U mid to follow the input voltage U in .

[0019] A further technical solution thereof is that the controller collects the medium-voltage bus voltage U mid and compares it with the minimum starting voltage U min and the maximum threshold voltage U max ;

[0020] When the medium-voltage bus voltage U mid is less than the minimum starting voltage U min , the controller controls the third DC / DC converter to stop working;

[0021] When the medium-voltage bus voltage U mid is greater than or equal to the minimum starting voltage U min , and less than the maximum threshold voltage U max , the controller controls the third DC / DC converter to proportionally step down the medium-voltage bus voltage U mid and load it onto the electrolyzer;

[0022] When the medium-voltage bus voltage U mid is greater than or equal to the maximum threshold voltage, the controller controls the third DC / DC converter to convert the medium-voltage bus voltage U mid into the maximum working voltage of the electrolyzer and load it onto the electrolyzer.

[0023] A further technical solution thereof is that when the energy storage capacity of the energy storage module is not full, the SOC of the energy storage module < 99%, and when the energy storage capacity of the energy storage module is full, the SOC of the energy storage module ≥ 99%;

[0024] When the energy storage module has energy storage capacity, the SOC of the energy storage module > 1%, and when the energy storage module has no energy storage capacity, the SOC of the energy storage module ≤ 1%.

[0025] A further technical solution thereof is that the controller obtains a photovoltaic preset power curve according to the illumination condition of the photovoltaic power generation system, and controls the first DC / DC converter to output the maximum power point voltage U MPP as the input voltage Uin .

[0026] A further technical solution thereof is that the preset voltage U ref is determined according to the rated voltage of the electrolytic cell, and U min < U ref < U max .

[0027] The beneficial technical effects of the present invention are as follows:

[0028] The present invention provides a photovoltaic hydrogen production power supply with energy storage and current conversion capabilities, which is connected to an energy storage module and charges / discharges the energy storage module according to the power supply state of the photovoltaic power generation system and the energy storage state of the energy storage module. It can reasonably store and consume the electric energy output by the photovoltaic power generation system, realizes the cross-time allocation of energy, and improves the utilization rate of photovoltaic energy. Considering the extreme situation where the energy storage capacity of the energy storage module cannot store energy or has no energy storage capacity, it can further fully utilize photovoltaic energy. At the same time, a medium-voltage bus is introduced into the photovoltaic hydrogen production power supply, and the energy storage module is used in combination with the medium-voltage bus to suppress the fluctuating power, which can reduce the ripple of the electrolytic cell supply voltage, obtain better supply current characteristics, and improve the hydrogen production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a structural block diagram of an embodiment of the photovoltaic hydrogen production power supply provided by the present invention.

[0030] Figure 2 is a schematic diagram of an embodiment of the photovoltaic preset power curve provided by the present invention.

[0031] Figure 3 is a logic control block diagram of the second DC / DC converter in an embodiment of the present invention.

[0032] Figure 4 is a logic control block diagram of the third DC / DC converter in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The following further describes the specific embodiments of the present invention with reference to the drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art.

[0034] To improve the light energy utilization rate of the photovoltaic hydrogen production power supply, the present invention provides a photovoltaic hydrogen production power supply with energy storage and current conversion capabilities. The first input end of the photovoltaic hydrogen production power supply is connected to a photovoltaic power generation system, the second input end of the photovoltaic hydrogen production power supply is connected to an energy storage module, and the output end of the photovoltaic hydrogen production power supply is connected to an electrolytic cell;

[0035] The photovoltaic power generation system supplies power to the electrolytic cell through the photovoltaic hydrogen production power supply, and the input voltage U of the photovoltaic power generation system inGreater than the preset voltage U ref When the energy storage capacity of the energy storage module is not full, the photovoltaic hydrogen production power supply controls the photovoltaic power generation system to charge the energy storage module to absorb the excess power of the photovoltaic power generation system;

[0036] The input voltage U of the photovoltaic power generation system in Less than the preset voltage U ref , and when the energy storage module has an energy storage capacity, the photovoltaic hydrogen production power supply controls the energy storage module to supplement the power supply for the electrolyzer.

[0037] Specifically, the present invention can, based on the power supply state of the photovoltaic power generation system and the energy storage state of the energy storage module, absorb and store the excess power of the photovoltaic power generation system through the energy storage module when the energy storage capacity of the energy storage module is not full. The excess power refers to the part of the power output by the photovoltaic power generation system that exceeds the rated power of the electrolyzer. When the energy storage module has an energy storage capacity and the photovoltaic power generation system lacks energy, the stored energy is used to supplement the power supply for the electrolyzer, thereby reasonably storing and consuming the electric energy output by the photovoltaic power generation system, realizing the cross-time allocation of energy, and improving the utilization rate of photovoltaic energy.

[0038] Figure 1 Fig. shows a structural block diagram of an embodiment of a photovoltaic hydrogen production power supply. The photovoltaic hydrogen production power supply includes a controller, a medium-voltage bus, a first DC / DC converter, a second DC / DC converter, and a third DC / DC converter;

[0039] The input end of the first DC / DC converter is connected to the photovoltaic power generation system as the first input end of the photovoltaic hydrogen production power supply, and the output end of the first DC / DC converter is connected to the medium-voltage bus;

[0040] One end of the second DC / DC converter is connected to the energy storage module as the second input end of the photovoltaic hydrogen production power supply, and the other end of the second DC / DC converter is connected to the medium-voltage bus;

[0041] The input end of the third DC / DC converter is connected to the medium-voltage bus, and the output end of the third DC / DC converter is connected to the electrolyzer as the output end of the photovoltaic hydrogen production power supply;

[0042] The medium-voltage bus, the first DC / DC converter, the second DC / DC converter, and the third DC / DC converter are all connected to the controller.

[0043] In this embodiment, the second DC / DC converter is a bidirectional DC / DC converter for charging and discharging the energy storage module. The input voltage U of the photovoltaic power generation system inGenerated and output to the medium-voltage bus by the controller controlling the first DC / DC converter. Specifically, the controller obtains the photovoltaic preset power curve according to the illumination condition of the photovoltaic power generation system, and uses the MPPT (Maximum Power Point Tracking) algorithm to track the maximum power point according to the photovoltaic preset power curve, and controls the first DC / DC converter to always output the maximum power point voltage U MPP As the input voltage U in , so that the photovoltaic power generation system outputs at the maximum output power through the first DC / DC converter. The MPPT algorithm can adopt the common form in the technical field of the present invention.

[0044] It should be understood that the magnitude of the maximum output power is affected by illumination. In order to ensure the stable operation of the power supply, the photovoltaic preset power curve can be obtained in advance. In one possible implementation, the photovoltaic preset power curve refers to the predicted maximum output power P MPP The curve that changes with time within the preset time length, and the preset time length can be 1 day or consecutive days, etc.

[0045] Figure 2 Shows an embodiment of the photovoltaic preset power curve, with the maximum output power P MPP As the vertical axis and time t as the horizontal axis are plotted. The predicted maximum output power P MPP Changes over time. Generally, when the sun is stronger at noon, P MPP Is the highest; when there is no sunlight at night, P MPP Is the lowest. Further, in specific implementation, the predicted maximum output power P MPP Can also be predicted by combining the actual geographical location, the season and the environment of the photovoltaic power generation system, etc. The embodiments of the present invention do not specifically limit the specific data of the photovoltaic preset power curve. The specific method of predicting the maximum output power P MPP According to illumination, actual geographical location, season and environment, etc. is consistent with the prior art. It should be noted that there is usually a small random difference between the predicted maximum output power P MPP And the actual maximum output power.

[0046] Figure 2 In which P N Represents the rated power of the electrolyzer connected to the photovoltaic hydrogen production power supply in the embodiments of the present invention. The preset voltage U ref Refers to the preset voltage of the medium-voltage bus. The preset voltage of the medium-voltage bus is determined according to the rated voltage of the electrolyzer. When the medium-voltage bus voltage is set to be equal to the preset voltage U ref , the third DC / DC converter can step down the preset voltage U refConvert to the rated voltage of the electrolyzer to make the electrolyzer operate at the rated state and output the rated power P N The equal-proportion step-down means that the ratio of the output voltage to the input voltage of the third DC / DC converter is a preset fixed ratio. It should be understood that the rated power P of the electrolyzer N is not the rated output power of the photovoltaic hydrogen production power supply, and the rated output power of the photovoltaic hydrogen production power supply can be adjusted according to the rated power of the connected electrolyzer.

[0047] Although the output power of the first DC / DC converter cannot be directly sampled, the output power of the first DC / DC converter is proportional to the maximum power point voltage U output by it MPP i.e., the input voltage U in , therefore, the present invention samples the input voltage U in and compares it with the preset voltage U ref to determine whether the output power of the first DC / DC converter is greater than the rated power P of the electrolyzer N .

[0048] Specifically, if the input voltage U in is greater than the preset voltage U ref , it is determined that the output power of the first DC / DC converter is higher than the rated power P of the electrolyzer at this time N , and the electrolyzer cannot fully consume the energy supplied by the photovoltaic, and at this time, the energy storage module needs to store the excess energy; if the input voltage U in is less than the preset voltage U ref , it is determined that the output power of the first DC / DC converter is lower than the rated power P of the electrolyzer at this time N , and the photovoltaic energy supply is not sufficient to support the electrolyzer to operate at the rated state, and the energy storage module needs to supplement the energy supply.

[0049] However, in specific implementation, there may be extreme cases where the energy storage capacity of the energy storage module is full and cannot store energy anymore, or there is no energy storage capacity to supplement the energy supply. Therefore, it is necessary to control the second DC / DC converter and the third DC / DC converter in combination with the power supply state of the photovoltaic power generation system and the energy storage state of the energy storage module to reasonably utilize the light energy. In this embodiment, the controller controls the second DC / DC converter and the third DC / DC converter in parallel and independently Figure 3 and Figure 4 respectively show the logic control block diagrams of the second DC / DC converter and the third DC / DC converter.

[0050] As Figure 3 and Figure 4 shown, the controller continuously samples the input voltage U in and compares the input voltage U in with the preset voltage U refCompare, combined with the input voltage U in and the energy storage capacity control second DC / DC converter. At the same time, the controller also continuously samples the medium-voltage bus voltage U mid , and compares the medium-voltage bus voltage U mid with the minimum startup voltage U min and the maximum threshold voltage U max to control the third DC / DC converter.

[0051] Currently, most electrolyzers have a wide load regulation range, and can operate at a minimum of 5% of the rated power, and can also operate at a state of exceeding the rated power by 5%-10%. The minimum startup voltage U min can be determined according to the lowest operating point of the electrolyzer, that is, U min After being stepped down proportionally by the third DC / DC converter, the electrolyzer operates at the minimum negative rated state. The maximum threshold voltage U max can be determined according to the highest operating point of the electrolyzer, that is, U max After being stepped down proportionally by the third DC / DC converter, it is equal to the maximum operating voltage of the electrolyzer, and the electrolyzer operates at the maximum over-rated state. From the above description, it can be seen that U ref After being stepped down proportionally by the third DC / DC converter, the electrolyzer operates at the rated state, so it can be known that U min <U ref <U max .

[0052] When the input voltage U in is greater than the preset voltage U ref and the energy storage capacity of the energy storage module is not full, the controller controls the medium-voltage bus to charge the energy storage module through the second DC / DC converter, stores the excess energy, and makes the medium-voltage bus voltage U mid equal to the preset voltage U ref . At this time, U min <U mid =U ref <U max , therefore, according to Figure 4 the shown logic block diagram, the controller controls the third DC / DC converter to step down U mid =U ref proportionally to the rated voltage of the electrolyzer to supply power to the electrolyzer, and the electrolyzer operates at the rated state. In this embodiment, the energy storage capacity of the energy storage module not being full specifically means that the SOC (State of Charge) of the energy storage module < 99%. Generally, the controller can obtain the SOC of the energy storage module by sampling parameters such as the voltage and current of the energy storage module, and the specific method of obtaining the SOC is consistent with the prior art.

[0053] When the input voltage U inLess than the preset voltage U ref , and when the energy storage module has an energy storage capacity, the controller controls the energy storage module to supply power to the medium-voltage bus through the second DC / DC converter, consume the stored energy, and make the medium-voltage bus voltage U mid equal to the preset voltage U ref . At this time, U min < U mid = U ref < U max , the controller controls the third DC / DC converter to step down U mid = U ref proportionally to the rated voltage of the electrolytic cell to supply power to the electrolytic cell, and the electrolytic cell operates in the rated state. In this embodiment, the energy storage module having an energy storage capacity specifically means that the SOC of the energy storage module > 1%.

[0054] Usually, the energy storage module will release a large amount of energy for a long time at night, so it is very rare for the energy storage capacity to be full. However, to cope with extreme situations, it is still necessary to protect the energy storage module to prevent damage to the energy storage module. When the input voltage U in is greater than the preset voltage U ref and the energy storage capacity of the energy storage module is full, the controller controls the second DC / DC converter to stop working, ensures the safe operation of the energy storage module, and controls the medium-voltage bus voltage U mid to follow the input voltage U in , that is, even if the medium-voltage bus voltage U mid changes with the input voltage U in , so that U mid = U in . At this time, U mid = U in > U ref > U min , according to the logic block diagram shown in Figure 4 , when U ref < U mid = U in ≤ U max , the controller controls the third DC / DC converter to step down U mid proportionally, so that the electrolytic cell operates in an over-rated state; when U mid = U in > U max , the controller controls the third DC / DC converter to step down U mid over a wide range, converting U mid to the maximum operating voltage, so that the electrolytic cell operates in the maximum over-rated state. In this embodiment, the energy storage capacity of the energy storage module being full specifically means that the SOC of the energy storage module ≥ 99%.

[0055] When the input voltage U in is less than the preset voltage Uref When there is no energy storage capacity in the energy storage module, the controller compares the input voltage U in with the minimum starting voltage U min .

[0056] When the input voltage U in is less than the minimum starting voltage U min , since the energy storage module cannot supply energy at this time, and the input voltage U in is not enough to support the electrolytic cell to work at the lowest working point, the controller controls the medium-voltage bus voltage U mid to be equal to the input voltage U in , and controls the medium-voltage bus to charge the energy storage module through the second DC / DC converter. At this time, U mid = U in < U min . According to the logic block diagram shown in Figure 4 , the controller controls the third DC / DC converter to stop working, the electrolytic cell has no power supply, and only the energy storage module stores and stores tiny energy.

[0057] When the input voltage U in is greater than or equal to the minimum starting voltage U min , the controller controls the medium-voltage bus voltage U mid to be equal to the input voltage U in , and controls the second DC / DC converter to stop working. At this time, U min ≤ U mid = U in ≤ U ref . According to the logic block diagram shown in Figure 4 , the controller controls the third DC / DC converter to perform proportional step-down on U mid . The energy storage module has no charge and discharge at this time, and the electrolytic cell works in the rated state or the negative rated state. In this embodiment, the fact that the energy storage module has no energy storage capacity specifically means that the SOC of the energy storage module ≤ 1%.

[0058] It should be noted that in this embodiment, when the input voltage U in is equal to the preset voltage U ref , the control logic executed is the same as when the input voltage U in is less than the preset voltage U ref . When U in = U ref > U min and the energy storage module has energy storage capacity, the controller will control the energy storage module to supply power to the medium-voltage bus through the second DC / DC converter. However, since U in = U ref , the medium-voltage bus voltage U mid can be stabilized at the preset voltage without the power supply of the energy storage moduleref Therefore, the energy storage module does not discharge during actual operation, and the controller controls the third DC / DC converter to U mid The voltage is reduced in proportion, and the electrolyzer works at the rated state; U in =U ref >U min When the energy storage module has no energy storage capacity, the second DC / DC converter stops operating, and the controller controls the third DC / DC converter to mid The voltage is reduced in proportion and the electrolytic cell operates at rated state.

[0059] It should be noted that the terms "first", "second" and "third" used in the above description are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0060] The above is only a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the protection scope of the present invention.

Claims

1. A photovoltaic hydrogen production power source with energy storage and current conversion capability, characterized in that: The first input end of the photovoltaic hydrogen production power supply is connected to the photovoltaic power generation system, the second input end of the photovoltaic hydrogen production power supply is connected to the energy storage module, and the output end of the photovoltaic hydrogen production power supply is connected to the electrolyzer; The photovoltaic power generation system supplies power to the electrolyzer through the photovoltaic hydrogen production power supply. The input voltage U in Greater than the preset voltage U ref When the energy storage capacity of the energy storage module is not full, the photovoltaic hydrogen production power source controls the photovoltaic power generation system to charge the energy storage module to absorb excess power of the photovoltaic power generation system; Input voltage U of photovoltaic power generation system in Less than the preset voltage U ref , and when the energy storage module has energy storage capacity, the photovoltaic hydrogen production power supply controls the energy storage module to supplement the power supply for the electrolyzer.

2. The photovoltaic hydrogen production power source with energy storage and current conversion capability according to claim 1 is characterized in that: The photovoltaic hydrogen production power supply includes a controller, a medium voltage bus, a first DC / DC converter, a second DC / DC converter and a third DC / DC converter; The input end of the first DC / DC converter is connected to the photovoltaic power generation system as the first input end of the photovoltaic hydrogen production power supply, and the output end of the first DC / DC converter is connected to the medium voltage bus; One end of the second DC / DC converter is connected to the energy storage module as the second input end of the photovoltaic hydrogen production power supply, and the other end of the second DC / DC converter is connected to the medium voltage bus; The input end of the third DC / DC converter is connected to the medium voltage bus, and the output end of the third DC / DC converter is connected to the electrolyzer as the output end of the photovoltaic hydrogen production power supply; The medium voltage bus, the first DC / DC converter, the second DC / DC converter and the third DC / DC converter are all connected to the controller.

3. The photovoltaic hydrogen production power source with energy storage and current conversion capability according to claim 2 is characterized in that: The first DC / DC converter outputs an input voltage U to the medium voltage bus. in , the controller samples the input voltage U in And the input voltage U in With the preset voltage U ref Make comparisons; When the input voltage U in Greater than the preset voltage U ref When the energy storage capacity of the energy storage module is not full, the controller controls the medium voltage bus to charge the energy storage module through the second DC / DC converter, so that the medium voltage bus voltage U mid With the preset voltage U ref equal.

4. The photovoltaic hydrogen production power source with energy storage and current conversion capability according to claim 3 is characterized in that: When the input voltage U in Less than the preset voltage U ref , and the energy storage module has energy storage capacity, the controller controls the energy storage module to supply power to the medium voltage bus through the second DC / DC converter, so that the medium voltage bus voltage U mid With the preset voltage U ref equal.

5. The photovoltaic hydrogen production power source with energy storage and current conversion capability according to claim 4 is characterized in that: When the input voltage U in Greater than the preset voltage U ref When the energy storage capacity of the energy storage module is full, the controller controls the second DC / DC converter to stop working and controls the medium voltage bus voltage U mid Following input voltage U in .

6. The photovoltaic hydrogen production power source with energy storage and current conversion capability according to claim 5 is characterized in that: When the input voltage U in Less than the preset voltage U ref , and the energy storage module has no energy storage capacity, the controller compares the input voltage U in With minimum starting voltage U min ; When the input voltage U in Less than the minimum starting voltage U min When the controller controls the medium voltage bus voltage U mid Following input voltage U in , and controls the medium voltage bus to charge the energy storage module through the second DC / DC converter; When the input voltage U in Greater than or equal to the minimum starting voltage U min When the controller controls the second DC / DC converter to stop working, and controls the medium voltage bus voltage U mid Following input voltage U in .

7. The photovoltaic hydrogen production power source with energy storage and current conversion capability according to any one of claims 3 to 6, characterized in that: The controller collects the medium voltage bus voltage U mid And with the minimum starting voltage U min And the maximum threshold voltage U max Make comparisons; When the medium voltage bus voltage U mid Less than the minimum starting voltage U min When , the controller controls the third DC / DC converter to stop working; When the medium voltage bus voltage U mid Greater than or equal to the minimum starting voltage U min , and is less than the maximum threshold voltage U max When the controller controls the third DC / DC converter to the medium voltage bus voltage U mid Perform proportional pressure reduction and load to the electrolytic cell; When the medium voltage bus voltage U mid When the voltage is greater than or equal to the maximum threshold voltage, the controller controls the third DC / DC converter to convert the medium voltage bus voltage U mid Converted to the maximum operating voltage of the electrolyzer and loaded to the electrolyzer.

8. The photovoltaic hydrogen production power source with energy storage and current conversion capability according to claim 6 is characterized in that: When the energy storage capacity of the energy storage module is not full, the SOC of the energy storage module is less than 99%, and when the energy storage capacity of the energy storage module is full, the SOC of the energy storage module is greater than or equal to 99%; When the energy storage module has energy storage capacity, the SOC of the energy storage module is greater than 1%, and when the energy storage module has no energy storage capacity, the SOC of the energy storage module is less than or equal to 1%.

9. The photovoltaic hydrogen production power source with energy storage and current conversion capability according to claim 3 is characterized in that: The controller obtains a photovoltaic preset power curve according to the illumination conditions of the photovoltaic power generation system, and uses the MPPT algorithm to control the first DC / DC converter to output the maximum power point voltage U according to the photovoltaic preset power curve. MPP As input voltage U in .

10. The photovoltaic hydrogen production power source with energy storage and current conversion capability according to claim 2, characterized in that: The preset voltage U ref Determined according to the rated voltage of the electrolytic cell, and U min <U ref <U max .

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