Off-grid hydrogen production system and method

Abstract

The present invention provides an off-grid hydrogen production system and method. The system includes a new energy power source, a DC converter, and a voltage regulator. The DC converter is used to boost the DC power output by the new energy power source; the voltage regulator is used to regulate the voltage of the DC power boosted by the DC converter to achieve voltage regulation of the hydrogen production equipment. The system of the present invention is more efficient than grid-connected hydrogen production and is beneficial for hydrogen production.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen production, and in particular relates to an off-grid hydrogen production system and method. Background Art

[0002] With the dual carbon goals being proposed, large-scale renewable energy development will become an inevitable path to building a new power system and achieving the dual carbon goals. The integration of large-scale renewable energy into the AC grid will cause significant power and frequency disturbances to the grid due to the randomness and volatility of wind and solar energy, as well as the lack of inertia and weak damping of wind and photovoltaic generators.

[0003] Currently, large-scale photovoltaic access requires the power grid to provide access points, and its volatility and randomness can easily affect the safe and stable operation of the power grid.

[0004] Therefore, it is necessary to design an off-grid hydrogen production system and method to solve the above technical problems. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention provides an off-grid hydrogen production system, which includes a new energy power supply, a DC converter and a voltage regulator, wherein:

[0006] The DC converter is used to boost the DC power output by the new energy power source;

[0007] The voltage regulator is used to regulate the voltage of the DC power boosted by the DC converter to achieve voltage regulation of the hydrogen production equipment.

[0008] Furthermore, the DC converter includes a first DC converter and a second DC converter, wherein:

[0009] The first DC converter is used to perform a first-stage voltage boost on the DC power output by the new energy power source;

[0010] The second DC converter is used to perform secondary voltage following or boosting on the DC power after the primary boosting.

[0011] Furthermore, the DC converter further includes a first current collector, wherein:

[0012] The first current collector is used to realize switching of direct current after the first-stage boosting.

[0013] Furthermore, the DC converter further includes a second current collector, wherein:

[0014] The second current collector is used to regulate the voltage of the switched direct current and transmit it to the second direct current converter.

[0015] Furthermore, the DC converter further includes a DC bus, and the DC bus is used to transmit the DC power after switching through the first current collector to the second current collector.

[0016] Furthermore, the voltage regulator includes a three-phase interleaved buck circuit, wherein:

[0017] The input end of the three-phase interleaved buck circuit is connected to the output end of the second DC converter, and the output end of the three-phase interleaved buck circuit can be connected to a hydrogen production device.

[0018] Furthermore, the first DC converter and the second DC converter each include a first capacitor, a first converter, an LLC resonant module, an isolation transformer, a second converter, and a second capacitor connected in sequence.

[0019] Furthermore, the first capacitor of the first DC converter is connected to the output end of the new energy power supply, and the second capacitor of the first DC converter is connected to the input end of the first current collector.

[0020] Furthermore, the first capacitor of the second DC converter is connected to the output end of the second current collector, and the second capacitor of the second DC converter is connected to the input end of the three-phase interleaved buck circuit.

[0021] Furthermore, the new energy power supply includes an MPPT controller, a boost circuit and a photovoltaic array, wherein:

[0022] The MPPT controller is used to achieve maximum power tracking of the photovoltaic array output;

[0023] The boost circuit is used to boost the direct current output by the photovoltaic array.

[0024] On the other hand, the present invention also provides an off-grid hydrogen production method, the method comprising:

[0025] Use a DC converter to boost the DC power output by the new energy power source;

[0026] The voltage regulator is used to regulate the voltage of the DC power boosted by the DC converter to achieve voltage regulation of the hydrogen production equipment.

[0027] Furthermore, the DC converter includes a first DC converter and a second DC converter, wherein:

[0028] The first DC converter is used to perform a first-stage voltage boost on the DC power output by the new energy power source;

[0029] The second DC converter is used to perform a second-stage boost on the DC power after the first-stage boost.

[0030] Furthermore, the DC converter further includes a first current collector, wherein:

[0031] The first current collector is used to realize switching of direct current after the first-stage boosting.

[0032] The present invention provides an off-grid hydrogen production system and method, which does not require photovoltaic grid access approval (i.e., does not require the grid to provide an access point), can significantly shorten the construction period, and has more flexible scale and capacity settings.

[0033] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 A structural schematic diagram of an off-grid hydrogen production system according to an embodiment of the present invention is shown.

[0036] Figure 2 A schematic flow chart of an off-grid hydrogen production method according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0038] Large-scale photovoltaic grid-connected hydrogen production involves multiple links such as inversion, boosting grid connection, transmission, voltage reduction, and rectification hydrogen production, which has high system losses and high construction costs. Figure 1 As shown, the present invention provides an off-grid hydrogen production system, which includes a new energy power supply, a DC converter and a voltage regulator, wherein:

[0039] The DC converter is used to boost the DC power output by the new energy power source;

[0040] The voltage regulator is used to regulate the voltage of the DC power boosted by the DC converter to achieve voltage regulation of the hydrogen production equipment.

[0041] A detailed description is given below.

[0042] For new energy power sources, the present invention is described using a 100MW photovoltaic collection system (i.e., the total power generation power of the new energy power source is 100MW). The new energy power sources include an MPPT controller, a boost circuit, and a photovoltaic array. There are multiple MPPT (Maximum Power Point Tracking) controllers, boost circuits, and photovoltaic arrays (N, N=20 in this embodiment), where:

[0043] The photovoltaic array is used to convert solar energy into direct current electricity for power generation, and the power generation capacity of each photovoltaic array is 2.5MW;

[0044] The MPPT controller is used to achieve maximum power tracking of the photovoltaic array output. Each MPPT controller is connected in parallel to the output end of a photovoltaic array, so that each photovoltaic array has an MPPT function;

[0045] The boost circuit is used to boost the direct current output of the photovoltaic array, thereby achieving a pre-stage voltage control function, wherein the boost circuit includes an inductor L1, a diode D1 and a first full-control module, the inductor L1 and the diode D1 are connected in series, one end of the inductor L1 is connected to the positive electrode of the photovoltaic array output, the anode of the first full-control module is connected to the connection point between the inductor L1 and the diode D1, and the cathode of the first full-control module is connected to the negative electrode of the photovoltaic array output, wherein each first full-control module includes a fully-controlled device T1 and an anti-parallel diode, that is, the anode of the diode D2 is connected to the cathode of the fully-controlled device T1, and the cathode of the diode D2 is connected to the anode of the fully-controlled device T1, wherein the fully-controlled device T1 is connected to the connection point between the inductor L1 and the diode D1.

[0046] In this embodiment, for the DC converter, specifically:

[0047] The DC converter includes a first DC converter, a second DC converter, a first current collector, a second current collector, and a DC bus, wherein:

[0048] The first DC converter is used to boost the DC power output by the new energy power source to ±30 kV. It should be noted that this embodiment only uses ±30 kV as an example, which does not mean that the first DC converter can only boost the DC power output by the new energy power source to ±30 kV.

[0049] The second DC converter is used to perform a second-stage boost on the DC power after the first-stage boost, thereby outputting a power supply suitable for the electrolysis equipment (hydrogen production equipment).

[0050] The first current collector is used to realize switching of direct current after the first-stage boosting.

[0051] The second current collector is used to regulate the voltage of the switched direct current and transmit it to the second direct current converter.

[0052] The DC bus is used to transmit DC power after switching through the first current collector (a transmission distance of approximately 20-40 kilometers) to the second current collector. The first and second current collectors are connected via the DC bus. There are two DC busbars: one is a +30kV DC busbar and the other is a -30kV DC busbar.

[0053] The circuit topology of each component of the DC converter is described in detail below.

[0054] In the embodiment of the present invention, the first DC converter and the second DC converter may adopt the same or similar structure. This embodiment is exemplified by assuming that the first DC converter and the second DC converter adopt the same structure. Specifically:

[0055] The first DC converter and the second DC converter each include a first capacitor C1, a first converter, an LLC resonant module, an isolation transformer, a second converter, and a second capacitor C2 connected in sequence.

[0056] The first converter includes two parallel first half-bridges, each of which is divided into an upper arm and a lower arm. A second fully-controlled module is provided on each upper arm and lower arm. Each second fully-controlled module includes a fully-controlled device T2 and an anti-parallel diode D3, where the anode of diode D3 is connected to the cathode of fully-controlled device T2, and the cathode of diode D3 is connected to the anode of fully-controlled device T2. On the same first half-bridge, the cathode of fully-controlled device T2 on the upper arm is connected to the anode of fully-controlled device T2 on the lower arm. For different first half-bridges, the anodes of fully-controlled devices T2 on the two upper arms are connected to each other, and the cathodes of fully-controlled devices T2 on the two lower arms are connected to each other.

[0057] The LLC resonant module includes a resonant inductor L2, a resonant capacitor C3, and a magnetizing inductor L3. The resonant inductor L2, resonant capacitor C3, and magnetizing inductor L3 are connected in series, with one end of the resonant inductor L2 connected to the midpoint of one of the first half-bridges, and one end of the magnetizing inductor L3 connected to the midpoint of the other first half-bridge. Furthermore, the isolation transformer includes a primary winding and a secondary winding. The primary winding of the isolation transformer is connected in parallel to both ends of the magnetizing inductor L3, and the first capacitor C1 is connected in parallel to both ends of one of the first half-bridges.

[0058] The second converter includes two second half-bridges connected in parallel. Each second half-bridge is also divided into an upper arm and a lower arm, and each upper arm and lower arm are provided with a diode D4. For the same second half-bridge, the anode of the upper arm diode D4 is connected to the cathode of the lower arm diode D4. For different second half-bridges, the cathodes of the two upper arm diodes D4 are interconnected, and the anodes of the two lower arm diodes D4 are interconnected. One end of the secondary winding of the isolation transformer is connected to the midpoint of one of the second half-bridges, and the other end of the secondary winding of the isolation transformer is connected to the midpoint of the other second half-bridge. A second capacitor C2 is connected in parallel with the other second half-bridge.

[0059] In addition, in this embodiment, the first capacitor C1 of the first DC converter is connected to the output end of the new energy power supply, that is, the two ends of the first capacitor C1 are respectively connected to the positive electrode and the negative electrode of the output end of the new energy power supply.

[0060] The first current collector includes a capacitor C4, a switch S, and two third fully-controlled modules. The third fully-controlled module includes a fully-controlled device T4 and an anti-parallel diode D5, where the anode of the diode D5 is connected to the cathode of the fully-controlled device T4, and the cathode of the diode D5 is connected to the anode of the fully-controlled device T4.

[0061] Two fully-controlled devices T4 are connected in series, with the cathode of one fully-controlled device T4 connected to the anode of the other fully-controlled device T4. One end of a capacitor C4 is connected to the anode of one fully-controlled device T4, and the other end of the capacitor C4 is connected to the cathode of the other fully-controlled device T4. One end of a switch S is connected to the anode of the other fully-controlled device T4, and the other end of the switch S is connected to the cathode of the other fully-controlled device T4.

[0062] In this embodiment, there are multiple (N) first current collectors, and the multiple first current collectors constitute a first current collector module. The multiple first current collectors are connected in series, and the series connection method is: the switches S of all the first first current collectors are connected in series, and the first first collector switch S is connected to one end of the +30KV DC bus through the inductor L4, and the switch S of the last collector is connected to one end of the -30KV DC bus.

[0063] In this embodiment, there are also multiple (N) first DC converters, and the multiple first DC converters are connected one-to-one with the multiple first DC converters. Specifically: the second capacitor C2 of each first DC converter is connected to the input end of the corresponding first collector, that is, the second capacitor C2 of each first DC converter is connected in parallel with the corresponding capacitor C4.

[0064] In this embodiment, the circuit topology of the second current collector is the same as that of the first current collector, and the second current collector also includes a capacitor C4, a switch S, and two third full-control modules.

[0065] In this embodiment, there are multiple (N) second current collectors, forming a second current collector module. These multiple second current collectors are connected in series as follows: the switches S of all first second current collectors are connected in series, with the first second current collector switch S connected to the other end of the +30 kV DC bus via inductor L4, and the switch S of the last second current collector connected to the other end of the -30 kV DC bus. The first capacitor C1 of each second DC converter is connected to the output end of the corresponding second current collector, i.e., the first capacitor C1 of each second DC converter is connected in parallel with the second capacitor C2 of the corresponding second current collector.

[0066] In this embodiment, the voltage regulator includes a three-phase interleaved buck circuit, and there are multiple (N) three-phase interleaved buck circuits. The input end of each three-phase interleaved buck circuit is connected to the output end of the corresponding second DC converter, and the output end of the three-phase interleaved buck circuit can be connected to the hydrogen production equipment. The topology of the three-phase interleaved buck circuit is specifically as follows:

[0067] The three-phase interleaved buck circuit includes a capacitor C6, three inductors L5, and three connecting branches, wherein the three connecting branches are connected in parallel, and each connecting branch includes a fourth fully-controlled module and a diode D7 connected in series. The fourth fully-controlled module includes a fully-controlled device T5 and an anti-parallel diode D6, i.e., the anode of diode D6 is connected to the cathode of fully-controlled device T5, and the cathode of diode D6 is connected to the anode of fully-controlled device T5. The cathode of diode D7 is connected to the cathode of fully-controlled device T5, and the anode of diode D7 is connected to the cathode of fully-controlled device T5. The three inductors L5 are respectively connected to the midpoints of the three connecting branches (i.e., the connection points between fully-controlled device T5 and diode D7), and the other ends of the three inductors L5 are connected to one end of capacitor C6, and the other end of capacitor C6 is connected to the anode of diode D7.

[0068] In this embodiment, every two adjacent voltage regulators are connected to one hydrogen production device, i.e., every two adjacent voltage regulators form a voltage regulator group. In each voltage regulator in each voltage regulator group, the other end of each of the three inductors L5 is connected to one end of the hydrogen production device, and the other end of the capacitor C6 is connected to the other end of the hydrogen production device.

[0069] In this embodiment, the second capacitor C2 of each second DC converter is connected to the input end of the corresponding three-phase interleaved buck circuit, that is, the second capacitor C2 of each second DC converter is connected in parallel with one of the connection branches of the corresponding three-phase interleaved buck circuit.

[0070] In this embodiment, all fully controlled devices include but are not limited to IGCT (Integrated Gate-Commutated Thyristor), IGBT (Insulated Gate Bipolar Transistor), and IEGT (Injection Enhanced Gate Transistor).

[0071] In this embodiment, the system has the following effects:

[0072] 1) First LLC module (a first LLC module composed of multiple first DC converters): The first DC converter in the first LLC module is connected in parallel with the corresponding boost device (boost circuit), enabling electrical isolation (since the output end of the first DC converter is high voltage and needs to be isolated, thus achieving voltage isolation between the input and output of the first DC converter), while also achieving voltage following (the output voltage of the first DC converter follows the input voltage) and reducing the number of series connections;

[0073] 2) Current collector module (multiple first current collectors): realizes switching of the entire module after parallel input (the input end of the first current collector is connected in parallel with the capacitor C2) and series output;

[0074] 3) DC line (DC bus): for transmission of photovoltaic power;

[0075] 4) Output current collector (multiple second current collectors): realize the voltage regulation function of the output module (multiple first DC converters);

[0076] 5) Second LLC module (second LLC module composed of multiple second DC converters): can also achieve electrical isolation and voltage following function;

[0077] 6) Three-phase interleaved buck circuit: to achieve load (hydrogen production equipment, Figure 1Flexible adjustment of the 0-800V voltage required by the electrolyzer (in the middle) is particularly critical during the startup phase of the hydrogen production equipment;

[0078] 7) Hydrogen production equipment: 5MW alkaline water electrolysis hydrogen production equipment (Alkaline Water Electrolysis, ALK) is used.

[0079] In this embodiment, the overall control strategy of the system is as follows:

[0080] In a large-scale photovoltaic-collected DC transmission off-grid hydrogen production system, when the load power is greater than the power supply power, the power supply controls the power; when the power supply power is greater than the load power, the load adjusts the power.

[0081] The MPPT maximum power tracking function needs to be implemented. An LLC (first LLC module and second LLC module) is added to the rear stage, followed by a three-phase staggered parallel buck circuit to achieve full voltage range conditions and load power regulation of the electrolysis equipment (hydrogen production equipment); the overall input and output power are balanced, Ur (actual reference voltage) -30kV→PI regulation of the total input and total output power is stable, and the load power command Pout is received at the same time to achieve input and output power matching.

[0082] Overall operation control quantity:

[0083] Series boost part: MPPT controls the photovoltaic power P0, the Boost circuit controls the front-stage voltage U0, the LLC follows the voltage U0 (that is, the input voltage of the first DC converter follows the output voltage of the Boost circuit), and the series modules are switched through the collector module to achieve a DC bus voltage of ±30kV.

[0084] When the load power is greater than the power supply power, the power is controlled by the power supply; when the power supply power is greater than the load power, the load adjusts the power; in the process of controlling or adjusting the power, communication within 20-30 kilometers is also achieved through the DC bus.

[0085] The MPPT maximum power tracking function needs to be implemented. Two LLCs are added to the back stage and a three-phase staggered parallel buck circuit is added to achieve the full voltage range conditions and load power regulation of the electrolysis equipment. By controlling the overall input and output power balance, Ur-30kV→PI adjusts the total input and total output power to be stable, and at the same time receives the load power command Pout to achieve input and output power matching.

[0086] Initial strategy

[0087] (1) If the power generation of the photovoltaic system (the total power generation of multiple new energy sources) is (2 / 3-1)P, the power can be controlled and the electrolyzer can be operated at reduced power;

[0088] (2) For example, when the power generation power of the photovoltaic system is (1 / 10-2 / 3)P, the collector (collector module and / or output collector) can be switched on and off to achieve switching matching between the load and the power source (new energy power source) (for example, if the input power of the photovoltaic array is small, the corresponding load can be cut off at the same time by switching on the second collector to achieve input-output matching);

[0089] (3) If the power generation capacity of the photovoltaic system is less than 1 / 10P, the transmission power is low and it is recommended that the system is not allowed to operate.

[0090] The system of this embodiment includes steps such as boosting, transmission, and stepping down (through a three-phase interleaved parallel buck circuit) for hydrogen production. The system efficiency is higher than that of grid-connected hydrogen production, and off-grid operation has no impact on the main power grid. It is very suitable for large-scale photovoltaic off-grid hydrogen production application scenarios, and provides another idea for the future development and utilization of new energy.

[0091] like Figure 2 As shown, on the other hand, this embodiment also provides an off-grid hydrogen production method, the method comprising:

[0092] Use a DC converter to boost the DC power output by the new energy power source;

[0093] The voltage regulator is used to regulate the voltage of the DC power boosted by the DC converter to achieve voltage regulation of the hydrogen production equipment.

[0094] In this embodiment, the functions and implementation methods of each step of an off-grid hydrogen production method correspond to the functions and implementation methods of each part of an off-grid hydrogen production system, and therefore, they are not repeated here.

[0095] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An off-grid hydrogen production system, comprising a new energy power supply, a DC converter and a voltage regulator, wherein: The DC converter is used to boost the DC power output by the new energy power source; the DC converter includes a first DC converter, a second DC converter, a first current collector, a second current collector and a DC bus, wherein: The first DC converter is used to perform a first-stage voltage boost on the DC power output by the new energy power source; The second DC converter is used to perform secondary voltage following or boosting on the DC power after the primary boosting; The first current collector is used to implement switching of the DC power after the first stage of boosting; The second current collector is used to regulate the voltage of the switched DC power and transmit it to the second DC converter; The DC bus is used to transmit the DC power after switching through the first collector to the second collector; the DC bus includes a positive polarity DC bus and a negative polarity DC bus; The voltage regulator is used to regulate the voltage of the DC power boosted by the DC converter to achieve voltage regulation of the hydrogen production equipment; There are N new energy power supplies, N first DC converters, N second DC converters, N first current collectors, N second current collectors, and N voltage regulators. The N first DC converters are connected to the N first current collectors in a one-to-one correspondence, and the N second DC converters are connected to the N second current collectors in a one-to-one correspondence; N first current collectors are connected in series, the first first current collector is connected to one end of the positive polarity DC bus, and the last first current collector is connected to one end of the negative polarity DC bus; N second current collectors are connected in series, the first second current collector is connected to the other end of the positive polarity DC bus, and the last second current collector is connected to the other end of the negative polarity DC bus.

2. An off-grid hydrogen production system according to claim 1, wherein: The voltage regulator includes a three-phase interleaved buck circuit, wherein the input end of the three-phase interleaved buck circuit is connected to the output end of the second DC converter, and the output end of the three-phase interleaved buck circuit can be connected to the hydrogen production equipment.

3. An off-grid hydrogen production system according to claim 2, wherein: The first DC converter and the second DC converter each include a first capacitor, a first converter, an LLC resonant module, an isolation transformer, a second converter, and a second capacitor, which are connected in sequence.

4. An off-grid hydrogen production system according to claim 3, wherein: The first capacitor of the first DC converter is connected to the output end of the new energy power supply, and the second capacitor of the first DC converter is connected to the input end of the first current collector.

5. An off-grid hydrogen production system according to claim 3, wherein: The first capacitor of the second DC converter is connected to the output end of the second current collector, and the second capacitor of the second DC converter is connected to the input end of the three-phase interleaved buck circuit.

6. An off-grid hydrogen production system according to any one of claims 1 to 5, wherein: The new energy power supply includes an MPPT controller, a boost circuit and a photovoltaic array, wherein the MPPT controller is used to achieve maximum power tracking of the photovoltaic array output; the boost circuit is used to boost the direct current output of the photovoltaic array.

7. An off-grid hydrogen production method, comprising: The DC power outputted by the new energy power source is boosted by a DC converter; the DC converter comprises a first DC converter, a second DC converter, a first current collector, a second current collector and a DC bus, wherein: The first DC converter is used to perform a first-stage voltage boost on the DC power output by the new energy power source; The second DC converter is used to perform secondary voltage following or boosting on the DC power after the primary boosting; The first current collector is used to implement switching of the DC power after the first stage of boosting; The second current collector is used to regulate the voltage of the switched DC power and transmit it to the second DC converter; The DC bus is used to transmit the DC power after switching through the first collector to the second collector; the DC bus includes a positive polarity DC bus and a negative polarity DC bus; The voltage regulator is used to regulate the voltage of the DC power boosted by the DC converter to achieve voltage regulation of the hydrogen production equipment; There are N new energy power supplies, N first DC converters, N second DC converters, N first current collectors, N second current collectors, and N voltage regulators. The N first DC converters are connected to the N first current collectors in a one-to-one correspondence, and the N second DC converters are connected to the N second current collectors in a one-to-one correspondence; N first current collectors are connected in series, the first first current collector is connected to one end of the positive polarity DC bus, and the last first current collector is connected to one end of the negative polarity DC bus; N second current collectors are connected in series, the first second current collector is connected to the other end of the positive polarity DC bus, and the last second current collector is connected to the other end of the negative polarity DC bus.

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