CN112290579A - Direct-current coupling off-grid hydrogen production system and control method thereof - Google Patents
Direct-current coupling off-grid hydrogen production system and control method thereof Download PDFInfo
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- CN112290579A CN112290579A CN201910631063.XA CN201910631063A CN112290579A CN 112290579 A CN112290579 A CN 112290579A CN 201910631063 A CN201910631063 A CN 201910631063A CN 112290579 A CN112290579 A CN 112290579A
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 223
- 239000001257 hydrogen Substances 0.000 title claims abstract description 223
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 223
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 206
- 238000000034 method Methods 0.000 title claims abstract description 55
- 230000008878 coupling Effects 0.000 title claims abstract description 16
- 238000010168 coupling process Methods 0.000 title claims abstract description 16
- 238000005859 coupling reaction Methods 0.000 title claims abstract description 16
- 238000004891 communication Methods 0.000 claims abstract description 86
- 230000033228 biological regulation Effects 0.000 claims abstract description 22
- 238000009826 distribution Methods 0.000 claims abstract description 14
- SJWPTBFNZAZFSH-UHFFFAOYSA-N pmpp Chemical compound C1CCSC2=NC=NC3=C2N=CN3CCCN2C(=O)N(C)C(=O)C1=C2 SJWPTBFNZAZFSH-UHFFFAOYSA-N 0.000 claims description 24
- 238000005868 electrolysis reaction Methods 0.000 claims description 15
- 230000009471 action Effects 0.000 claims description 3
- 230000006698 induction Effects 0.000 claims description 3
- 230000001360 synchronised effect Effects 0.000 claims description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 9
- 239000001301 oxygen Substances 0.000 description 9
- 229910052760 oxygen Inorganic materials 0.000 description 9
- 238000010248 power generation Methods 0.000 description 6
- 230000004048 modification Effects 0.000 description 5
- 238000012986 modification Methods 0.000 description 5
- 238000003860 storage Methods 0.000 description 5
- 230000001276 controlling effect Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 230000001105 regulatory effect Effects 0.000 description 4
- 230000007547 defect Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004146 energy storage Methods 0.000 description 2
- 238000002955 isolation Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000003513 alkali Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E70/00—Other energy conversion or management systems reducing GHG emissions
- Y02E70/30—Systems combining energy storage with energy generation of non-fossil origin
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- Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
Abstract
The invention provides a control method of a direct current coupling off-grid hydrogen production system, wherein after a hydrogen production tank system generates a current regulation instruction with a total input current reference value according to the state of the hydrogen production tank and sends the current regulation instruction to an intelligent communication unit, the intelligent communication unit distributes the total input current reference value according to the number of converters for supplying power to the hydrogen production tank to obtain a partial current instruction with an output current reference value and sends the partial current instruction to each converter for supplying power to the hydrogen production tank; enabling each converter to respectively regulate the output current of the converter according to the current dividing instruction; and further realizes the online adjustment of the output current of each converter, so that the output current is matched with the hydrogen production tank state of the connected hydrogen production tank system. And moreover, the regulation reference value of the output current of each optimizer can be determined according to the comparison and judgment between the output capacity of the current converter and the distribution result, so that the output voltage of each converter is ensured to be matched with the voltage/current of the hydrogen production tank.
Description
Technical Field
The invention relates to the technical field of automatic control, in particular to a direct-current coupling off-grid hydrogen production system and a control method thereof.
Background
In recent years, new energy power generation, such as photovoltaic power generation and wind power generation, is developed rapidly, but due to the defects of unstable power generation and low energy density, an energy storage system is often required to be matched; the hydrogen is used as an energy storage medium which is completely pollution-free from preparation to terminal use, and is suitable for being matched with new energy to generate electricity to make up the defects. Most of the commercial new energy power generation and hydrogen production systems at present adopt a grid-connected scheme, the power generation electric energy needs to be subjected to multi-stage conversion, the utilization rate is low, the number of system equipment is large, and the cost is high; the hydrogen production system needs to be connected into a power grid through a rectifier to obtain energy from the grid side, so that a high-voltage distribution system and a corresponding harmonic treatment device need to be built, the cost and the complexity are increased, and the system cannot be used in remote areas.
In order to solve various defects of an alternating current hydrogen production system, a direct current coupled off-grid hydrogen production system is provided in the prior art, a power grid is not required to be connected, and the number of power conversion stages is small; as shown in fig. 1, the new energy power supply is connected to the hydrogen production tank system through a DC/DC converter or an AC/DC converter to provide energy required for hydrogen production for the hydrogen production tank, and the hydrogen production tank generates hydrogen and oxygen and stores the hydrogen and oxygen in the hydrogen storage/oxygen system. Therefore, the energy utilization rate can be improved, and the control is simple; however, the converter usually operates in MPPT (Maximum Power Point Tracking) control mode, and it is necessary to control its output voltage above the minimum electrolysis voltage of the hydrogen production tank, so its output current usually follows its Maximum Power Point, and online adjustment of the output current cannot be realized.
Disclosure of Invention
The invention provides a control method of a direct-current coupling off-grid hydrogen production system, which aims to solve the problem that the on-line regulation of the output current of a converter cannot be realized in the prior art.
In order to achieve the purpose, the technical scheme provided by the application is as follows:
a control method of a direct current coupling off-grid hydrogen production system comprises an intelligent communication unit and a plurality of converters with output ends connected in parallel to a hydrogen production tank power supply end of a hydrogen production tank system; the control method comprises the following steps:
the hydrogen production tank system of the direct-current coupling off-grid hydrogen production system generates a current regulation instruction with a total input current reference value according to the hydrogen production tank state and sends the current regulation instruction to the intelligent communication unit;
the intelligent communication unit determines the number of converters for supplying power to the hydrogen production tank;
the intelligent communication unit distributes the total input current reference value according to the number of the converters to obtain a partial current instruction with an output current reference value and sends the partial current instruction to each converter for supplying power to the hydrogen production tank;
and each converter respectively adjusts the output current of the converter according to the current dividing instruction.
Preferably, before obtaining a partial current command with an output current reference value and sending the partial current command to each converter for supplying power to the hydrogen production tank, the method further comprises the following steps:
the intelligent communication unit determines the output power of each converter for supplying power to the hydrogen production tank in an MPPT control mode;
the intelligent communication unit calculates an input voltage reference value of the hydrogen production tank according to the total input current reference value, the equivalent resistance of the hydrogen production tank and the minimum electrolysis voltage;
the intelligent communication unit respectively calculates the output current value of each converter according to the input voltage reference value of the hydrogen production tank and the output power of each converter;
and the intelligent communication unit respectively compares the output current value of each converter with the result of the distribution of the total input current reference value, and takes the smaller value as the output current reference value of the corresponding converter.
Preferably, each converter adjusts its output current according to the divided current command, and the method includes:
each converter respectively adjusts the output current of the converter to the output current reference value.
Preferably, the intelligent communication unit determines the output power of each converter for supplying power to the hydrogen production tank in the MPPT control mode, and includes:
the intelligent communication unit calculates output power of the corresponding converter according to output voltage and output current of each converter under the MPPT control mode;
or,
and the intelligent communication unit respectively receives the output power of each converter under the MPPT control mode.
Preferably, the intelligent communication unit calculates the output current value of each converter according to the input voltage reference value of the hydrogen production tank and the output power of each converter, and the calculation formula is as follows: Pmpp/Uo；
Where Pmpp is the output power of the converter, UoIs the input voltage reference value of the hydrogen production tank.
Preferably, the output current reference value is a result of the distribution of the total input current reference value;
in the control method, before obtaining a partial current instruction with an output current reference value and sending the partial current instruction to each converter for supplying power to the hydrogen production tank, the method further comprises the following steps:
the intelligent communication unit calculates an input voltage reference value of the hydrogen production tank according to the total input current reference value, the equivalent resistance of the hydrogen production tank and the minimum electrolysis voltage;
in the control method, when a partial current instruction with an output current reference value is obtained and sent to each converter for supplying power to the hydrogen production tank, the method further comprises the following steps:
and the intelligent communication unit issues the input voltage reference value of the hydrogen production tank to the corresponding converter.
Preferably, each converter adjusts its output current according to the divided current command, and the method includes:
each converter calculates to obtain the output current value of the converter according to the input voltage reference value of the hydrogen production tank and the output power of the converter;
each converter respectively compares the output current value of the converter with the output current reference value, and the smaller value is taken as the adjustment reference value of the output current of the converter.
Preferably, each converter calculates to obtain its own outputtable current value according to the input voltage reference value of the hydrogen production tank and its own output power, and the adopted calculation formula is: Pmpp/Uo；
Where Pmpp is the output power of the converter, UoIs the input voltage reference value of the hydrogen production tank.
Preferably, the intelligent communication unit calculates the input voltage reference value of the hydrogen production tank according to the total input current reference value, the equivalent resistance of the hydrogen production tank and the minimum electrolysis voltage, and the adopted calculation formula is as follows:
Uo＝[(Uo×I_ref)×Req]1/2+Uin_limit1；
wherein Req is the equivalent resistance of the hydrogen production cell, Uin _ limit1 is the minimum electrolysis voltage of the hydrogen production cell, UoAnd I _ ref is the input voltage reference value of the hydrogen production cell and the total input current reference value.
Preferably, the intelligent communication unit determines the number of converters for supplying power to the hydrogen production tank, and comprises:
the intelligent communication unit is respectively communicated with each converter connected with the intelligent communication unit, or receives the output voltage of each converter connected with the intelligent communication unit, and determines the number of the converters for supplying power to the hydrogen production tank.
Preferably, before the hydrogen production tank system of the dc-coupled off-grid hydrogen production system generates a current regulation instruction with a total input current reference value according to a hydrogen production tank state and issues the current regulation instruction to the intelligent communication unit, the method further includes:
when the system is started, the hydrogen production tank system issues a hydrogen production tank state to each converter for supplying power to the hydrogen production tank through the intelligent communication unit;
and when the hydrogen tank state is normal, each converter respectively executes the starting action and enters the MPPT control mode.
Preferably, the intelligent communication unit is arranged outside the hydrogen production tank system, or the intelligent communication unit is integrated inside the hydrogen production tank system.
Preferably, if the converter is a DC/DC converter, the input end of each DC/DC converter receives the electric energy output by the corresponding photovoltaic string;
and if the converter is an AC/DC converter, the input end of each AC/DC converter receives the electric energy output by the corresponding fan through the corresponding double-fed induction motor DFIG or the permanent magnet synchronous generator PMSG.
The invention provides a control method of a direct current coupling off-grid hydrogen production system, wherein after a hydrogen production tank system generates a current regulation instruction with a total input current reference value according to the state of the hydrogen production tank and sends the current regulation instruction to an intelligent communication unit, the intelligent communication unit distributes the total input current reference value according to the number of converters for supplying power to the hydrogen production tank to obtain a partial current instruction with an output current reference value and sends the partial current instruction to each converter for supplying power to the hydrogen production tank; enabling each converter to respectively regulate the output current of the converter according to the current dividing instruction; and further realizes the online adjustment of the output current of each converter, so that the output current is matched with the hydrogen production tank state of the connected hydrogen production tank system.
And moreover, the regulation reference value of the output current of each optimizer can be determined according to the comparison and judgment between the output capacity of the current converter and the distribution result, so that the output voltage of each converter is ensured to be matched with the voltage/current of the hydrogen production tank.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of a prior art DC-coupled off-grid hydrogen production system;
FIGS. 2 to 4 are schematic diagrams of three structures of a DC-coupled off-grid hydrogen production system provided in an embodiment of the present invention;
fig. 5 to 7 are flow charts of control methods of a dc-coupled off-grid hydrogen production system according to another embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The invention provides a control method of a direct-current coupling off-grid hydrogen production system, which aims to solve the problem that the on-line regulation of the output current of a converter cannot be realized in the prior art.
Referring to fig. 2, the dc-coupled off-grid hydrogen production system includes: hydrogen production tank system, intelligent communication unit and a plurality of converters. The output end of each converter is connected in parallel to the hydrogen production tank power supply end of the hydrogen production tank system to provide electrolysis electric energy for the hydrogen production tank; the system has a fault redundancy function and high system reliability. The hydrogen production tank generates hydrogen and oxygen by the principle of water electrolysis and stores the hydrogen and oxygen to the corresponding oxygen storage system and hydrogen storage system respectively. The hydrogen production tank in the hydrogen production tank system can be any one of an alkali liquor electrolytic tank, a PEM electrolytic tank or a solid oxide electrolytic tank; it is not specifically limited herein, and is within the scope of the present application, depending on the specific application environment.
The intelligent communication unit is used for realizing communication with the hydrogen production tank system and each converter, such as uploading of the number of the converters, issuing of the hydrogen production tank state, issuing of a hydrogen production tank current regulation instruction and the like. Specifically, one side of the intelligent communication unit is respectively connected with the controller of each converter, and the other side of the intelligent communication unit is connected with the communication end of the control cabinet of the hydrogen production tank system. The intelligent communication unit can be independently arranged externally, and can also be integrated in a hydrogen production tank system, such as a control cabinet.
If the converters are DC/DC converters, the input end of each DC/DC converter respectively receives the electric energy output by the corresponding photovoltaic group string; the photovoltaic group string can be composed of photovoltaic components with various power levels, can form a photovoltaic 1000V system, can also be a 1500V system, and can be a photovoltaic system with even higher voltage level. The DC/DC converter can be an isolation topology, a non-isolation topology, a voltage reduction topology or a voltage increase/decrease topology. According to the specific application environment requirement, a combiner box can be additionally arranged to realize the electric energy input of the multi-path photovoltaic group string, as shown in fig. 3; the number of the bus boxes connected to each DC/DC converter is not limited, and the number of the bus boxes can be 8, 16, 20 and the like. Of course, the system may also be without a combiner box if the DC/DC converter power is relatively small.
If the converters are AC/DC converters, the input end of each AC/DC converter receives the electric energy output by the corresponding fan through a corresponding DFIG (Doubly fed Induction Generator) or PMSG (permanent magnet synchronous Generator), as shown in fig. 4. In practical application, the AC/DC converter may be an isolated topology, a non-isolated topology, a boost topology, a buck topology, or a buck/boost topology; and is not particularly limited herein.
Referring to fig. 5, the method for controlling the dc-coupled off-grid hydrogen production system includes:
s101, generating a current regulating instruction with a total input current reference value according to the hydrogen production tank state by a hydrogen production tank system of the direct-current coupling off-grid hydrogen production system, and sending the current regulating instruction to an intelligent communication unit.
The hydrogen production tank state refers to the conditions of the hydrogen production tank in the hydrogen production tank system, such as tank pressure, tank temperature, hydrogen/oxygen liquid level and the like. The hydrogen production tank state of the hydrogen production tank system is different under different conditions. The hydrogen production tank system needs controllable input current according to the conditions of tank pressure, tank temperature, hydrogen/oxygen liquid level and the like of the hydrogen production tank system so as to realize the matching between the state and the current; this requires the output current of the respective converter to which it is connected to be adjustable by it. In the specific adjusting process, firstly, a hydrogen production tank system is required to generate a matched total input current reference value according to the hydrogen production tank state of the hydrogen production tank system; and then the total input current reference value is transmitted to the intelligent communication unit through a current regulation instruction, so that the intelligent communication unit can perform further parameter calculation and instruction transmission with each converter according to the total input current reference value.
S102, the intelligent communication unit determines the number of converters for supplying power to the hydrogen production tank.
The specific process can be that the intelligent communication unit respectively communicates with each converter connected with the intelligent communication unit, such as handshaking communication, to determine the number of converters supplying power to the hydrogen production tank; or the intelligent communication unit can determine the number of the converters for supplying power to the hydrogen production tank by receiving the output voltage of each converter connected with the intelligent communication unit; it is not specifically limited herein, and is within the scope of the present application, depending on the application environment.
In practical applications, steps S101 and S102 are not limited to the sequence shown in fig. 5, and may be executed before step S103.
S103, distributing the total input current reference value by the intelligent communication unit according to the number of the converters to obtain a partial current instruction with an output current reference value and transmitting the partial current instruction to each converter for supplying power to the hydrogen production tank.
The intelligent communication unit can obtain a total input current reference value I _ ref of a hydrogen production tank power supply end of the hydrogen production tank system through the received current regulation instruction; the total input current reference value I _ ref is divided, for example, equally divided, according to the number N of converters, and the divided result is I _ ref/N. Then, according to the specific application environment, the distributed result I _ ref/N can be directly used as an output current reference value and is sent to each converter for supplying power to the hydrogen production tank through a partial current instruction; or carrying out optimization processing according to the distributed result I _ ref/N to obtain an output current reference value, and transmitting the output current reference value to each converter for supplying power to the hydrogen production tank through a current distribution instruction; it is not specifically limited herein, and is within the scope of the present application, depending on the application environment.
And S104, regulating the output current of each converter according to the divided current commands.
In practical application, each converter can directly regulate the output current to the output current reference value, or can regulate the output current according to the processed result after the output current reference value in the current dividing instruction is optimized; it is not specifically limited herein, and is within the scope of the present application, depending on the application environment.
According to the control method of the direct-current coupling off-grid hydrogen production system, through the principle, each converter respectively adjusts the output current of the converter, so that the output current of each converter is adjusted on line, and the output current of each converter is matched with the hydrogen production tank state of the connected hydrogen production tank system; reliable hydrogen production is realized through the coordination control between the converter and the hydrogen production tank system.
It is worth mentioning that when the output capacities of the new energy power sources connected to the converters are different, for example, the blocking of the photovoltaic panels is different or the wind speeds of the fans are different, if the output current distribution of the converters is only based on a simple distribution principle, the output voltage of all the converters may not match the voltage/current of the hydrogen production tank; therefore, another embodiment of the present invention further provides another method for controlling a dc-coupled off-grid hydrogen production system, based on the above embodiments and fig. 2 to 5, preferably, as shown in fig. 6, before obtaining a partial current command with an output current reference value and sending the partial current command to each converter for supplying power to a hydrogen production tank in S103, further comprising:
s201, the intelligent communication unit determines output power of each converter for supplying power to the hydrogen production tank in an MPPT control mode.
Under normal conditions, each converter works in the MPPT control mode, and the intelligent communication unit determines the specific mode of the output power of each converter, wherein the specific mode can be that the output power of the corresponding converter is calculated according to the output voltage and the output current of each converter in the MPPT control mode; alternatively, the output power of each converter in the MPPT control mode may be directly received; it is not specifically limited herein, and is within the scope of the present application, depending on the application environment.
S202, the intelligent communication unit calculates and obtains an input voltage reference value of the hydrogen production tank according to the total input current reference value, the equivalent resistance and the minimum electrolysis voltage of the hydrogen production tank.
The calculation formula adopted is as follows: u shapeo＝[(Uo×I_ref)×Req]1/2+Uin_limit1(ii) a Wherein, Req is the equivalent resistance of the hydrogen production tank, Uin _ limit1 is the minimum electrolysis voltage of the hydrogen production tank, UoI _ ref is the total input current reference for the input voltage reference of the hydrogen production cell.
S203, the intelligent communication unit respectively calculates to obtain the output current value of each converter according to the input voltage reference value of the hydrogen production tank and the output power of each converter;
the calculation formula of the output current value of each converter is as follows: Pmpp/Uo(ii) a Where Pmpp is the output power of the converter, UoIs the input voltage reference value of the hydrogen production tank.
At this time, the intelligent communication unit in step S103 allocates the total input current reference value according to the number of converters, and may execute steps S201 to S203 simultaneously or not, and it is only required to ensure that all steps are executed before step S204, which is within the protection scope of the present application depending on the specific application environment.
S204, the intelligent communication unit respectively compares the output current value of each converter with the result of the distribution of the total input current reference value, and the smaller value is taken as the output current reference value of the corresponding converter.
The intelligent communication unit preliminarily determines the result I _ ref/N after the total input current reference value is allocated according to the number N of converters, and then compares (Pmpp/U)o) And (I _ ref/N) to determine an output current reference value for the respective converter; in particular when a certain converter is (Pmpp/U)o) When the current is greater than (I _ ref/N), the output current reference value in the current dividing instruction issued to the converter by the intelligent communication unit is (I _ ref/N), and the converter outputs current according to (I _ ref/N); when a certain converter is used(Pmpp/Uo) Less than or equal to (I _ ref/N), the output current reference value in the current distribution instruction issued by the intelligent communication unit to the converter is (Pmpp/U)o) The converter will be in accordance with (Pmpp/U)o) And outputting the current.
At this time, correspondingly, in step S104, each converter adjusts its own output current according to the divided current command, including:
each converter respectively adjusts the output current of the converter to an output current reference value.
The rest steps are the same as the previous embodiment, and are not described in detail here.
It should be noted that, in the above embodiment, the comparison and determination process between the outputable current value of each converter and the result after the total input current reference value is assigned may also be performed in each converter, and at this time, the output current reference value issued in step S103 refers to the result (I _ ref/N) after the total input current reference value is assigned.
Correspondingly, as shown in fig. 7, the method for controlling the dc-coupled off-grid hydrogen production system further includes, before obtaining a partial current command with an output current reference value and sending the partial current command to each converter for supplying power to the hydrogen production tank in step S103:
s301, the intelligent communication unit calculates and obtains an input voltage reference value of the hydrogen production tank according to the total input current reference value, the equivalent resistance of the hydrogen production tank and the minimum electrolysis voltage.
The calculation formula adopted is as follows: u shapeo＝[(Uo×I_ref)×Req]1/2+Uin_limit1(ii) a Wherein, Req is the equivalent resistance of the hydrogen production tank, Uin _ limit1 is the minimum electrolysis voltage of the hydrogen production tank, UoI _ ref is the total input current reference for the input voltage reference of the hydrogen production cell.
At this time, the intelligent communication unit in step S103 allocates the total input current reference value according to the number of converters, and may be executed simultaneously with or not at step S301, depending on the specific application environment, and all of them are within the protection scope of the present application.
In addition, the method for controlling the dc-coupled off-grid hydrogen production system, while obtaining a partial current command with an output current reference value and sending the partial current command to each converter for supplying power to the hydrogen production tank in step S103, further includes:
and S302, the intelligent communication unit issues the input voltage reference value of the hydrogen production tank to the corresponding converter.
That is, the intelligent communication unit needs to issue not only the output current reference value (I _ ref/N), but also the input voltage reference value U of the hydrogen tanko(ii) a In practical applications, the simultaneous delivery is preferred, and the delivery may also be performed in batches, which is not specifically limited herein and is determined according to the specific application environment, and all of which are within the protection scope of the present application.
Correspondingly, step S104, each converter respectively adjusts its own output current according to the divided current command, including:
s401, calculating to obtain self-output current values by each converter according to the input voltage reference value of the hydrogen production tank and the self-output power;
and each converter tracks the maximum power Pmpp according to the current state and calculates the value of the current which can be output by the converter: Pmpp/Uo(ii) a Wherein, UoIs the input voltage reference value of the hydrogen production tank.
S402, each converter compares the output current value with the output current reference value, and the smaller value is used as the adjustment reference value of the output current.
The converters are compared separately (Pmpp/U)o) And (I _ ref/N) to determine its own output current reference value; in particular when a certain converter is (Pmpp/U)o) When the current is larger than (I _ ref/N), the converter outputs current by taking (I _ ref/N) as a regulation reference value of the output current of the converter; when a certain converter is (Pmpp/U)o) Less than or equal to (I _ ref/N), the converter being of the order of (Pmpp/U)o) And the current is output as a regulating reference value of the self output current.
In the two embodiments, for the direct-current coupled hydrogen production system with the multiple outputs connected in parallel with the hydrogen production tank system, information interaction between the converter and the hydrogen production tank system is realized through the intelligent communication unit, the number of the pre-stage converters is determined, the current regulation instruction issued by the hydrogen production tank is received, and the current distribution instruction is issued to the converter after corresponding processing; in addition, the online modification process of the system output current is not based on a simple distribution principle, but is based on the comparison and judgment of the output capacity of the current converter and the distribution result to output the current, so as to ensure that the output voltage of each converter is matched with the voltage/current of the hydrogen production tank.
Taking the structure shown in fig. 3 as an example, an on-line modification example of the current under the hydrogen production tank system with multiple parallel-connected converter outputs is given below, and for a 1000V photovoltaic system, the hydrogen production tank has 1MW, and a single DC/DC converter has a capacity of 100 KW: the operating voltage range of full-load MPPT at the input side is generally 550-850V, the voltage of an electrolytic tank is generally 100-150V, and the whole system consists of 10 DC/DC converters.
When the photovoltaic module is shielded, for example, the second photovoltaic string region and the tenth photovoltaic string region are shielded, the input power of the second DC/DC converter is 20KW, the input power of the tenth DC/DC converter is 80KW, the total input power is 900KW, and the total input current reference value in a current regulation instruction issued by the hydrogen making tank system is 5400A. The intelligent communication unit calculates that the input voltage reference value of the hydrogen production tank is 144.1V, and the result I _ ref/N after the total input current reference value is distributed is (5400/10) ═ 540A; for a 100KW DC/DC converter, it can output current value Pmpp/UoIs (100000/144.1) ═ 693.96>540, so that the output current reference value is 540A, the DC/DC converter exits the MPPT mode and works in a power limiting state; for a second DC/DC converter with 20KW input power, it can output current value Pmpp/UoIs (20000/144.1) ═ 138.79<540, so its output current reference is 138.79 a; for the tenth DC/DC converter with 80KW input power, it can output current value Pmpp/UoIs (80000/144.1) ═ 555.17>540, so its output current reference is 540A.
The control method for the dc-coupled off-grid hydrogen production system provided in each of the above embodiments preferably further includes, before step S101:
(1) when the system is started, the hydrogen production tank system issues a hydrogen production tank state to each converter for supplying power to the hydrogen production tank through the intelligent communication unit.
(2) When the hydrogen making tank state is normal, each converter respectively executes the starting action and enters the MPPT control mode.
The judgment of whether the hydrogen production tank is normal or not may be implemented by a controller as a communication host in each converter built-in controller, may be implemented by the built-in controllers of each converter respectively, or may be implemented by a master controller of each converter without a built-in controller, and is not specifically limited herein.
Each converter is in an MPPT control mode in a normal working state, so that the control of each converter is mutually decoupled, the control is simple, and the scheme is easy to realize; and moreover, multiple MPPT paths can also maximally utilize photovoltaic/wind power energy to produce hydrogen.
It should be noted that, in practical application, a new energy hydrogen production power station may be provided with a plurality of dc-coupled off-grid hydrogen production systems, each dc-coupled off-grid hydrogen production system is provided with one hydrogen production tank system, and each hydrogen production tank system is provided with a corresponding intelligent communication unit, a plurality of converters, and different new energy power supplies connected to the converters; multiple hydrogen production cell systems may share an oxygen storage system and a hydrogen storage system. And each direct current coupling off-grid hydrogen production system is operated and controlled by adopting the control method, and the detailed description is omitted.
The embodiments of the invention are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments can be referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make numerous possible variations and modifications to the present teachings, or modify equivalent embodiments to equivalent variations, without departing from the scope of the present teachings, using the methods and techniques disclosed above. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention, unless the contents of the technical solution of the present invention are departed.
Claims (13)
1. A control method of a direct-current coupling off-grid hydrogen production system is characterized in that the direct-current coupling off-grid hydrogen production system comprises an intelligent communication unit and a plurality of converters with output ends connected in parallel to a hydrogen production tank power supply end of a hydrogen production tank system; the control method comprises the following steps:
the hydrogen production tank system of the direct-current coupling off-grid hydrogen production system generates a current regulation instruction with a total input current reference value according to the hydrogen production tank state and sends the current regulation instruction to the intelligent communication unit;
the intelligent communication unit determines the number of converters for supplying power to the hydrogen production tank;
the intelligent communication unit distributes the total input current reference value according to the number of the converters to obtain a partial current instruction with an output current reference value and sends the partial current instruction to each converter for supplying power to the hydrogen production tank;
and each converter respectively adjusts the output current of the converter according to the current dividing instruction.
2. The method for controlling the dc-coupled off-grid hydrogen production system according to claim 1, wherein before obtaining a partial current command with an output current reference value and sending the partial current command to each converter for supplying power to the hydrogen production tank, the method further comprises:
the intelligent communication unit determines the output power of each converter for supplying power to the hydrogen production tank in an MPPT control mode;
the intelligent communication unit calculates an input voltage reference value of the hydrogen production tank according to the total input current reference value, the equivalent resistance of the hydrogen production tank and the minimum electrolysis voltage;
the intelligent communication unit respectively calculates the output current value of each converter according to the input voltage reference value of the hydrogen production tank and the output power of each converter;
and the intelligent communication unit respectively compares the output current value of each converter with the result of the distribution of the total input current reference value, and takes the smaller value as the output current reference value of the corresponding converter.
3. The method for controlling the dc-coupled off-grid hydrogen production system according to claim 2, wherein each converter adjusts its output current according to the sub-current command, and the method comprises:
each converter respectively adjusts the output current of the converter to the output current reference value.
4. The method for controlling the dc-coupled off-grid hydrogen production system according to claim 2, wherein the determining, by the intelligent communication unit, the output power of each converter supplying power to the hydrogen production cell in the MPPT control mode comprises:
the intelligent communication unit calculates output power of the corresponding converter according to output voltage and output current of each converter under the MPPT control mode;
or,
and the intelligent communication unit respectively receives the output power of each converter under the MPPT control mode.
5. The control method of the direct-current coupled off-grid hydrogen production system according to claim 2, wherein the intelligent communication unit respectively calculates the output current value of each converter according to the input voltage reference value of the hydrogen production tank and the output power of each converter, and the adopted calculation formula is as follows: Pmpp/Uo；
Where Pmpp is the output power of the converter, UoIs the input voltage reference value of the hydrogen production tank.
6. The control method of the dc-coupled off-grid hydrogen production system according to claim 1, wherein the output current reference value is a result of the total input current reference value assignment;
in the control method, before obtaining a partial current instruction with an output current reference value and sending the partial current instruction to each converter for supplying power to the hydrogen production tank, the method further comprises the following steps:
the intelligent communication unit calculates an input voltage reference value of the hydrogen production tank according to the total input current reference value, the equivalent resistance of the hydrogen production tank and the minimum electrolysis voltage;
in the control method, when a partial current instruction with an output current reference value is obtained and sent to each converter for supplying power to the hydrogen production tank, the method further comprises the following steps:
and the intelligent communication unit issues the input voltage reference value of the hydrogen production tank to the corresponding converter.
7. The method for controlling the dc-coupled off-grid hydrogen production system according to claim 6, wherein each converter adjusts its output current according to the sub-current command, and the method comprises:
each converter calculates to obtain the output current value of the converter according to the input voltage reference value of the hydrogen production tank and the output power of the converter;
each converter respectively compares the output current value of the converter with the output current reference value, and the smaller value is taken as the adjustment reference value of the output current of the converter.
8. The control method of the direct-current coupled off-grid hydrogen production system according to claim 7, wherein each converter calculates its own outputtable current value according to the input voltage reference value of the hydrogen production tank and its own output power, and the adopted calculation formula is: Pmpp/Uo；
Where Pmpp is the output power of the converter, UoTo said systemAn input voltage reference for the hydrogen tank.
9. The control method of the direct-current coupled off-grid hydrogen production system according to any one of claims 2 to 8, wherein the intelligent communication unit calculates the input voltage reference value of the hydrogen production cell according to the total input current reference value, the equivalent resistance of the hydrogen production cell and the minimum electrolysis voltage, and the adopted calculation formula is as follows:
Uo＝[(Uo×I_ref)×Req]1/2+Uin_limit1；
wherein Req is the equivalent resistance of the hydrogen production cell, Uin _ limit1 is the minimum electrolysis voltage of the hydrogen production cell, UoAnd I _ ref is the input voltage reference value of the hydrogen production cell and the total input current reference value.
10. The method for controlling the direct-current coupled off-grid hydrogen production system according to any one of claims 1 to 8, wherein the intelligent communication unit determines the number of converters for supplying power to the hydrogen production cell, and comprises the following steps:
the intelligent communication unit is respectively communicated with each converter connected with the intelligent communication unit, or receives the output voltage of each converter connected with the intelligent communication unit, and determines the number of the converters for supplying power to the hydrogen production tank.
11. The method for controlling the direct-current coupled off-grid hydrogen production system according to any one of claims 1 to 8, wherein before the hydrogen production tank system of the direct-current coupled off-grid hydrogen production system generates a current regulation instruction with a total input current reference value according to a hydrogen production tank state and issues the current regulation instruction to the intelligent communication unit, the method further comprises:
when the system is started, the hydrogen production tank system issues a hydrogen production tank state to each converter for supplying power to the hydrogen production tank through the intelligent communication unit;
and when the hydrogen tank state is normal, each converter respectively executes the starting action and enters the MPPT control mode.
12. The method for controlling the direct-current coupled off-grid hydrogen production system according to any one of claims 1 to 8, wherein the intelligent communication unit is arranged outside the hydrogen production tank system, or the intelligent communication unit is integrated inside the hydrogen production tank system.
13. The control method of the direct current coupling off-grid hydrogen production system according to any one of claims 1 to 8, wherein if the converters are DC/DC converters, the input end of each DC/DC converter receives the electric energy output by the corresponding photovoltaic group string;
and if the converter is an AC/DC converter, the input end of each AC/DC converter receives the electric energy output by the corresponding fan through the corresponding double-fed induction motor DFIG or the permanent magnet synchronous generator PMSG.
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