CN116334691A - Multi-stack electrolytic tank power distribution method and system suitable for rapid power impact - Google Patents
Multi-stack electrolytic tank power distribution method and system suitable for rapid power impact Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
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- C25B1/00—Electrolytic production of inorganic compounds or non-metals
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- C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
- C25B9/60—Constructional parts of cells
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
- C25B9/70—Assemblies comprising two or more cells
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- Y02E60/30—Hydrogen technology
- Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
Abstract
The invention provides a multi-stack electrolyzer power distribution method and a system suitable for rapid power impact, which construct a multi-stack electrolyzer hydrogen production system, wherein the multi-stack electrolyzer hydrogen production system comprises a fluctuation power supply and a plurality of electrolyzer single stacks which adopt parallel topology, and each electrolyzer single stack comprises an electrolyzer and a DC/DC converter; calculating the operation efficiency of the single cell stack based on the voltage efficiency, faraday efficiency and auxiliary machine efficiency of the single cell stack; calculating total voltage degradation of the single cell stack based on the operating efficiency of the single cell stack; and setting turning power points to perform power distribution. The method has the advantages that the voltage degradation rate of the single cell stack under five different working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation is used as an ageing calculation index, the time of each single cell stack in the high-power interval operation is reduced through a step-by-step and average distribution strategy, the multi-stack ageing consistency is ensured, and ageing is effectively delayed.
Description
Technical Field
The invention relates to the technical field of hydrogen production by a water electrolysis cell, in particular to a multi-stack electrolysis cell power distribution method and system suitable for rapid power impact.
Background
Renewable energy sources such as wind power and photovoltaic have the advantages of no pollution, convenient acquisition and the like, so that more and more countries and regions begin to research and develop renewable energy sources. But the volatility and discontinuity of renewable energy sources render them not fully incorporated into the grid for consumption. In recent years, the peak clipping and valley filling of the output of renewable energy power generation by using an energy storage system to achieve the effect of stabilizing fluctuation is a research and application hot spot. The hydrogen energy is used as a clean energy source, has the characteristics of high energy density, long service life, convenient storage and transportation and the like, and has the application specific gravity in the hybrid energy storage system in recent years. The hydrogen is prepared by utilizing the rapid fluctuation power through the electrolytic cell so as to achieve the purpose of flexibly storing and recycling electric energy, however, the rapid fluctuation power impact can lead to the accelerated aging of the electrolytic cell, and the prior researches show that frequent start and stop, power fluctuation, high-frequency current ripple waves and the like can accelerate the dissolution, deactivation, agglomeration and passivation of the electrocatalyst of the electrolytic cell, and the degradation of the membrane and metal ion poisoning can also be aggravated.
At present, ageing researches on electrolytic cells under fluctuating power are mainly focused on the aspect of power distribution strategies, wherein the traditional power distribution strategies are mainly divided into an average distribution strategy and a chained distribution strategy, the average distribution strategy refers to that input power is evenly distributed into each single stack, and all electrolytic cells bear the fluctuation at the same time in the distribution mode; the chained distribution strategy refers to that each single stack is put into operation step by step, the next-stage electrolytic tank is started after the previous-stage electrolytic tank reaches rated input power, and the like, but the problem of ageing before starting is also accompanied at the same time, other power distribution strategies basically aim at the optimal efficiency, and the problem of balancing the ageing degree of the single stacks of the electrolytic tank is rarely considered.
Disclosure of Invention
The invention provides a multi-stack electrolytic cell power distribution method and a system suitable for rapid power impact, which are used for solving the problem of ageing of a multi-stack electrolytic cell array under the rapid power impact, so that the energy utilization rate of the system is reduced.
In order to solve the technical problems, the invention provides a multi-stack electrolytic cell power distribution method suitable for rapid power impact, which comprises the following steps:
step S1: constructing a multi-stack electrolyzer hydrogen production system, wherein the multi-stack electrolyzer hydrogen production system comprises a fluctuation power supply and a plurality of electrolyzer single stacks which adopt parallel topology, and each electrolyzer single stack comprises an electrolyzer and a DC/DC converter;
step S2: calculating the operation efficiency of the single cell stack based on the voltage degradation rate and the operation efficiency of the single cell stack under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation;
step S3: calculating the total voltage degradation of the single stack of the electrolytic tank based on the voltage degradation rate and the operation efficiency of the single stack of the electrolytic tank under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation;
step S4: setting turning power point to perform power distribution
The power distribution method comprises the following steps:
step S41: ranking based on total voltage degradation of each of the single stacks of cells;
step S42: when the fluctuation power supply power is smaller than the product of the number of the single stacks of the electrolytic cells and the turning power point, carrying out step-by-step delivery operation according to the sequencing sequence of the step S41, and preferentially operating the single stacks of the electrolytic cells with the minimum total voltage degradation;
step S43: when the fluctuation power supply power is larger than the product of the number of the single stacks of the electrolytic cells and the turning power point, the load is increased, and the excess power is evenly distributed to the single stacks of the electrolytic cells;
step S44: when the fluctuating mains power is reduced, the power of the cell stack with the greatest total voltage degradation is preferentially reduced until the operation is stopped.
Preferably, the cell stack in step S1 further comprises an external power source for maintaining a minimum operating voltage of the cell stack when no power is input.
Preferably, the expression for calculating the operating efficiency of the single stack of cells in step S2 is:
η el ＝η V ·η F ·η ae
wherein eta is el Indicating the total efficiency of the single stack of the electrolytic cell eta V Representing the voltage efficiency, eta of the single stack of the electrolytic cell F Representing Faraday efficiency, eta of a single stack of an electrolytic cell ae Representing the auxiliary machine efficiency of the electrolytic cell single pile;
wherein V is th Representing the thermal neutral voltage of the single stack of the electrolytic cell, V cell The cell voltage of the cell stack is represented, p represents the cell internal operating pressure of the cell stack, and i represents the cell current density of the cell stack.
Preferably, the total voltage degradation DeltaV of the single stack of cells is calculated in step S3 d The expression of (2) is:
ΔV d ＝n el ·(t m ·V m +t fl ·V fl +t ct ·V ct +t fh ·V fh +t cr ·V cr )
wherein V is m 、V fl 、V ct 、V fh And V cr Respectively represents voltage degradation rate under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation, t m 、t fl 、t ct 、t fh And t cr The operation time is respectively the operation time under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation.
Preferably, the power distribution adopts a Buck converter based on fuzzy PID control to supply power for each electrolytic cell single stack.
Preferably, the Buck converter adopts a double-input and three-output structure, wherein the double-input represents a power difference E and a difference change rate EC of the actual running power of a single stack of the input electrolytic tank and the distributed power of the system, and the three-output represents an output dynamic PID parameter K p 、K i 、K d Control is completed for PID controller, K p Representing the proportionality coefficient, K i Represent the integration time constant, K d Representing the differential time constant.
Preferably, the Buck converterThe fuzzy set { NB, NM, NS, ZO, PS, PM, PB } of seven variables is adopted to define a power difference E and a change rate EC, a membership function is selected as a triangle function, the fuzzy selection is performed to obtain the final output value of fuzzy reasoning by taking the center of gravity of the curve of the fuzzy membership function and the area of the surrounding city of the abscissa as the final output value of fuzzy reasoning, and a fuzzy rule table is established to continuously adjust and output a dynamic PID parameter K p 、K i 、K d NB represents negative big, NM represents negative middle, NS represents negative small, ZO represents zero, PS represents middle, PB represents positive big.
The invention also provides a multi-stack electrolytic cell power distribution system adapting to rapid power impact, which is characterized in that: the system comprises a multi-stack electrolytic cell hydrogen production system, an operation efficiency calculation module, a total voltage degradation calculation module, a power distribution module and a fuzzy control module;
the multi-stack electrolyzer hydrogen production system comprises a fluctuation power supply and a plurality of electrolyzer single stacks which adopt parallel topology, wherein each electrolyzer single stack comprises an electrolyzer and a DC/DC converter;
the operation efficiency calculation module is used for calculating the operation efficiency of the single cell stack based on the voltage efficiency, faraday efficiency and auxiliary machine efficiency of the single cell stack and outputting the operation efficiency to the total voltage degradation calculation module;
the total voltage degradation calculation module is used for calculating total voltage degradation based on the operation efficiency of the electrolytic cell single stack;
the power distribution module is used for setting turning power points and distributing power based on the total voltage degradation;
the power distribution method comprises the following steps: ranking based on total voltage degradation of each of the single stacks of cells; when the fluctuation power supply power is smaller than the product of the number of the single stacks of the electrolytic cells and the turning power point, carrying out step-by-step delivery operation according to a sequencing order, and preferentially operating the single stacks of the electrolytic cells with the minimum total voltage degradation; when the fluctuation power supply power is larger than the product of the number of the single stacks of the electrolytic cells and the turning power point, the load is increased, and the excess power is evenly distributed to the single stacks of the electrolytic cells; when the fluctuation power supply power is reduced, preferentially reducing the power of the electrolytic cell single stack with the maximum total voltage degradation until stopping operation;
the fuzzy control module is used for supplying power to the single cell stack by adopting a Buck converter based on fuzzy PID control, the Buck converter is of a double-input and three-output structure, the double-input represents a power difference E and a difference change rate EC of the actual running power of the single cell stack and the distributed power of the system, and the three-output represents an output dynamic PID parameter K p 、K i 、K d Control is completed for PID controller, K p Representing the proportionality coefficient, K i Represent the integration time constant, K d Representing the differential time constant.
Preferably, the total voltage degradation calculation module calculates a total voltage degradation Δv of the single stack of electrolytic cells d The expression of (2) is:
ΔV d ＝n el ·(t m ·V m +t fl ·V fl +t ct ·V ct +t fh ·V fh +t cr ·V cr )
wherein V is m 、V fl 、V ct 、V fh And V cr Respectively represents voltage degradation rate under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation, t m 、t fl 、t ct 、t fh And t cr The operation time is respectively the operation time under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation.
Preferably, the single cell stack in the multi-stack hydrogen production system further comprises an external power source for maintaining a minimum operating voltage of the single cell stack when no power is input.
The beneficial effects of the invention at least comprise the following aspects:
the method has the advantages that the single cell stack is used for maintaining operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation under five different working conditions as an ageing calculation index, the time of each single cell stack in a high-power interval is reduced through a step-by-step and then average distribution strategy, start-stop sequencing optimization is designed, multi-stack ageing consistency is guaranteed, the operation condition of each single cell stack is collected, the power distribution sequence of each single cell stack is determined through on-line calculation of the voltage degradation condition, the ageing of a multi-stack electrolytic cell array under rapid power impact is effectively delayed, the energy utilization rate of a system is improved, and the high-efficiency and stable operation of a multi-stack electrolytic cell hydrogen production system adapting to the rapid power impact is guaranteed.
As an additional technical feature, by designing an external power supply, the electrolytic tank is ensured to be maintained at the lowest working voltage when no input is provided, and the aging of the electrolytic tank caused by frequent start and stop is avoided; compared with the traditional PID control, the fuzzy PID control converter has smaller overshoot and faster response speed, and the following performance is enhanced.
Drawings
FIG. 1 is a schematic flow chart of a method according to an embodiment of the invention;
FIG. 2 is a schematic diagram of a multi-stack electrolyzer hydrogen production system in accordance with an embodiment of the present invention;
FIG. 3 is a flow chart illustrating power distribution according to an embodiment of the present invention;
FIG. 4 is a graph of 8760 hours output power of a 200kW fan for a year in an embodiment of the present invention;
FIG. 5 is a graph showing 8760 hours of variation of input power of each cell stack according to an embodiment of the present invention;
FIG. 6 is a graph showing a variation of the input power 148h of each stack in the test power distribution result according to the embodiment of the present invention;
FIG. 7 is a diagram illustrating a single stack run time in a test power allocation result in accordance with an embodiment of the present invention;
FIG. 8 is a graph showing voltage degradation of a single stack in a test power distribution result according to an embodiment of the present invention;
FIG. 9 is a graph showing the comparison of 8760 hours post-operation efficiency in the test power distribution results according to the embodiment of the present invention;
FIG. 10 is a graph showing the cumulative energy efficiency of the test power allocation results according to an embodiment of the present invention;
FIG. 11 is a schematic diagram illustrating fuzzy PID control in accordance with an embodiment of the invention;
fig. 12 is a graph showing output power of the Buck converter according to the test power distribution result in the embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is evident that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by a person skilled in the art without any inventive effort, are intended to be within the scope of the present invention, based on the embodiments of the present invention.
As shown in fig. 1, the embodiment of the invention provides a multi-stack electrolytic cell power distribution method suitable for rapid power impact, which comprises the following steps:
step S1: a multi-stack electrolytic cell hydrogen production system is constructed, and comprises a fluctuation power supply and a plurality of electrolytic cell single stacks which adopt parallel topology, wherein each electrolytic cell single stack comprises an electrolytic cell and a DC/DC converter.
Specifically, as shown in fig. 2, the multi-stack electrolyzer hydrogen production system structure comprises a plurality of electrolyzer single stacks which adopt parallel topology to increase electrolyzer power level, wherein each electrolyzer single stack comprises an electrolyzer and a DC/DC converter; the single-stack cascade DC/DC converters of the electrolytic cells are connected to the DC bus, so that each single-stack of the electrolytic cells can be independently controlled.
The electrolytic tank cannot be restarted instantaneously after the electrolytic tank is completely stopped, high fluctuation power cannot be matched, hydrogen is accumulated at the anode and permeates to the cathode through the membrane due to frequent start-stop switching, and safety problems are caused, so that when the electrolytic tank which is in dynamic operation does not have fluctuation power input, the electrolytic tank Shan Dui of the embodiment of the invention is further provided with an external power supply, and the external power supply is used for maintaining the lowest working voltage of the electrolytic tank single stack when no power is input, and hydrogen production is not performed at the moment.
Step S2: calculating the operation efficiency of the single cell stack based on the voltage efficiency, faraday efficiency and auxiliary machine efficiency of the single cell stack;
the expression for calculating the operation efficiency of the single stack of the electrolytic cell is:
η el ＝η V ·η F ·η ae
wherein eta is el Indicating the total efficiency of the single stack of the electrolytic cell eta V Representing the voltage efficiency, eta of the single stack of the electrolytic cell F Representing Faraday efficiency, eta of a single stack of an electrolytic cell ae Representing the auxiliary machine efficiency of the electrolytic cell single pile;
wherein V is th Representing the thermal neutral voltage of the single stack of the electrolytic cell, V cell The cell voltage of the cell stack is represented, p represents the cell internal operating pressure of the cell stack, and i represents the cell current density of the cell stack.
Step S3: calculating total voltage degradation of the single cell stack based on the voltage degradation rate and the operating efficiency of the single cell stack under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation;
dynamic operation is the main cause of the degradation of the elements of the electrolytic cell, and the degradation of the electrolytic cell leads to the rise of working voltage, such as the rise of activation overvoltage caused by catalyst dissolution and catalyst agglomeration caused by load circulation and start-stop switching, and the rise of ohmic overvoltage caused by catalyst agglomeration and electrode passivation caused by high current density, and the rise of ohmic overvoltage caused by passivation of a catalyst carrier and membrane poisoning.
Based on the reason of the degradation of each element of the electrolytic tank, the embodiment of the invention adopts the following formula to calculate the total voltage degradation delta V of the single stack of the electrolytic tank d ：
ΔV d ＝n el ·(t m ·V m +t fl ·V fl +t ct ·V ct +t fh ·V fh +t cr ·V cr )
Wherein V is m 、V fl 、V ct 、V fh And V cr Respectively represents voltage degradation rate under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation, t m 、t fl 、t ct 、t fh And t cr The operation time is respectively the operation time under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation.
Step S4: and setting turning power points to perform power distribution.
Specifically, as shown in fig. 3, when wind power is input, the system first determines the number of cell stacks put into operation and the power value allocated to each stack. And meanwhile, the operation condition of each single cell stack is collected, and the power distribution sequence of each single stack is determined by calculating the voltage degradation condition on line. If a single stack is temporarily without wind power input, the external power supply to the single stack is started to maintain operation. In addition, the system updates the efficiency curve of each individual stack according to the current voltage degradation conditions and monitors the run time of the external power source to calculate the energy utilization of the system.
Power turning point P t In order to change from low power fluctuation operation to high power fluctuation operation, the critical power is determined by the specific model of the electrolytic cell, and in the embodiment of the invention, if the current density exceeds 1A/cm 2 As a demarcation point, then for a 60kW electrolytic cell in the example of the invention, the turning power point takes 40kW; for other types of cells, other values are the case. In addition, the electrolytic tank can be aged after long-term operation, and the turning power point needs to be adjusted according to the aging condition.
Step S41: ranking based on total voltage degradation of each cell stack;
step S42: when the fluctuation power supply power is smaller than the product of the number of the single stacks of the electrolytic cells and the turning power point, carrying out step-by-step delivery operation according to the sequencing sequence of the step S41, and preferentially operating the single stacks of the electrolytic cells with the minimum total voltage degradation;
step S43: when the fluctuation power supply power is larger than the product of the number of the single stacks of the electrolytic cell and the turning power point, the load is increased at the moment, and the excess power is evenly distributed to the single stacks of the electrolytic cell; specifically, when P source <(K·P t ) At the time P source For fluctuating power, K is the total number of electrolytic cells of the system, and the kth single-pile running power reaches a turning power point P t When the kth single-pile operation power is kept at P t At the same time, the (k+1) th single pile is put into operation; when P source >(K·P t ) When the power exceeding part is distributed to each single pile evenly;
step S44: when the fluctuating power supply power is reduced, the power of the electrolytic cell single stack with the largest total voltage degradation is preferentially reduced until the operation is stopped
In the embodiment of the invention, as shown in fig. 11, a Buck converter based on fuzzy PID control is used for supplying power to each electrolytic cell in a single stack.
The Buck converter adopts a double-input and three-output structure, wherein the double-input represents a power difference E and a difference change rate EC of the single-stack actual running power of the input electrolytic tank and the system distribution power, and the three-output represents an output dynamic PID parameter K p 、K i 、K d Control is completed for PID controller, K p Representing the proportionality coefficient, K i Represent the integration time constant, K d Representing the differential time constant.
The Buck converter adopts a fuzzy set { NB, NM, NS, ZO, PS, PM, PB } of seven variables to define a power difference E and a change rate EC, a membership function selects a triangle function, a fuzzy selection is performed by solving the fuzzy selection to obtain a final output value of fuzzy reasoning by taking the center of gravity of a curve of the fuzzy membership function and the area of a horizontal coordinate surrounding city as a final output value, and a fuzzy rule table is established to continuously adjust and output a dynamic PID parameter K p 、K i 、K d NB represents negative big, NM represents negative middle, NS represents negative small, ZO represents zero, PS represents middle, PB represents positive big.
In the power distribution control process, K is needed to be calculated p 、K i And K d The control effect can be optimized only by continuous adjustment,it is therefore necessary to build a fuzzy rule table of three parameters. And outputting a corresponding output value according to the specified rule by the fuzzy control system. The fuzzy rule table set for the three parameters should follow the following rules:
when the value of the power difference E is large, K is required to be calculated p The value of (2) is properly increased, so that the response speed of the system is increased; when the overshoot of the system is excessive, K is calculated i The value of (2) is properly reduced, and the overshoot of the system is reduced; and for K d The value of (2) needs to be limited to avoid the phenomenon of integral saturation.
When the values of the power difference E and the change rate EC are moderate, K i And K d It is also necessary to take on correspondingly moderate values, while K p The small value should be taken to avoid the overshoot phenomenon of the system.
When the value of the power difference E is small, K i And K d A larger value should be taken to ensure the stability of the system; when the value of the temperature difference change rate EC is large, K d Is more sensitive to changes in EC, in which case K d A smaller value should be taken.
Based on the above rules, a fuzzy rule table is set as shown in table one:
list one
Where NB represents negative big, NM represents negative medium, NS represents negative small, ZO represents zero, PS represents medium, PB represents positive big, kp represents proportionality coefficient, ki represents integral time constant, kd represents differential time constant.
The power of the electrolytic tank is a physical quantity with strong hysteresis and nonlinearity, and the fuzzy control shows better stability when processing complex systems such as nonlinearity, time-varying property and the like, and can be used for overcoming the defect of insufficient effect of the traditional PID control. Compared with the traditional PID control, the fuzzy PID control Buck converter has the advantages of smaller overshoot, quicker response speed and enhanced following property.
The embodiment of the invention is illustrated by taking a multi-stack system formed by single stacks of 4 60KW electrolytic cells as an example, and simulating rapid power impact P by wind power generation power source As shown in FIG. 5, the turning power point P is the output data of 8760 hours of a 200kW wind generating set in the whole year t And setting the voltage degradation rate at 40kW under each working condition as shown in a second table.
Watch II
When P source Less than P t When wind power is born by one electrolytic tank Shan Dui. P as the wind power generation power level increases source Greater than P t When the next single pile is started, the wind power is shared by two piles, and the running power of the first pile started at the moment is kept at P t The method comprises the steps of carrying out a first treatment on the surface of the When P source Reaching 2P t When the third electric pile is started, the wind power is shared by the three electric piles, and the operation power of the first two electric piles started at the moment is kept at P t And so on. When P source Greater than K.P t When the excess power is distributed evenly to the individual stacks. In addition, the electrolytic cell cannot be restarted instantaneously after the complete stop of operation, and cannot match the high fluctuation of the input wind power. In the power distribution strategy provided by the invention, when the dynamically operated electrolytic cell does not input wind power, an external power supply of 600W is adopted to maintain the operation of the electrolytic cell at the lowest working voltage, and hydrogen production is not performed at the moment.
FIG. 6 shows a single stack input power profile for each cell. It can be seen that the operating conditions of the stacks are substantially similar, and there are no excessive output or longer idle times. And most of the time, each pile works below the turning power value, when the wind power input power exceeds the sum of the turning power, the exceeding part is evenly distributed to each pile, and the running time of a high-power interval is reduced.
Fig. 7 shows the test power distribution results, and it can be seen that in the embodiment of the present invention, under the power distribution strategy considering aging, the operation time of each stack is basically the same, and the stacks hardly operate in the full power state, the electrolytic cells which operate first will be sorted backwards in the next round of operation according to the aging condition, and take charge of wind power input power fluctuation in turn.
FIG. 8 shows the operation time of each cell stack under five conditions, and under the distribution strategy of the present invention, the operation time of each stack under different conditions is substantially the same, indirectly proving that the voltage degradation conditions are substantially the same.
Fig. 9 shows the voltage degradation of each stack, it can be seen that the system substantially guarantees multi-stack consistency and that each stack voltage degradation is optimized.
FIG. 10 shows an electrolyzer efficiency curve with a maximum electrolyzer stack efficiency of 65.28% and a 6.29% decrease from unaged with reduced aging ratio under the power distribution strategy of the present invention that accounts for aging.
FIG. 11 shows the efficiency of the cell after 8760 hours of operation of the stack and system. After 8760 hours of operation, the energy utilization rate of the system under the power distribution strategy considering aging reaches 61.65 percent, and the main reason is that each stack is low in aging speed and low in energy utilization rate reduction rate.
Figure 12 shows the power split values for the first 24 hours of single stack of cell number 1 under the strategy of the present invention. The actual output power of the Buck converter is better in following performance, the two curves are basically coincident, and feasibility and superiority of the Buck converter based on fuzzy PID control as an execution link of a wind-hydrogen system power distribution strategy are verified.
The invention also provides a multi-stack electrolytic cell power distribution system adapting to rapid power impact, which is characterized in that: the system comprises a multi-stack electrolytic cell hydrogen production system, an operation efficiency calculation module, a total voltage degradation calculation module, a power distribution module and a fuzzy control module;
the hydrogen production system with multiple electrolytic tanks comprises a fluctuation power supply and multiple electrolytic tank single stacks which adopt parallel topology, wherein each electrolytic tank single stack comprises an electrolytic tank and a DC/DC converter.
The operation efficiency calculation module is used for calculating the operation efficiency of the single cell stack based on the voltage efficiency, faraday efficiency and auxiliary machine efficiency of the single cell stack, and outputting the operation efficiency to the total voltage degradation calculation module.
And the total voltage degradation calculation module is used for calculating the total voltage degradation based on the operation efficiency of the single stack of the electrolytic cell.
And the power distribution module is used for setting turning power points and distributing power based on total voltage degradation.
The power distribution method comprises the following steps: ranking based on total voltage degradation of each cell stack; when the fluctuation power supply power is smaller than the product of the number of the single stacks of the electrolytic cells and the turning power point, carrying out step-by-step delivery operation according to the sequencing order, and preferentially operating the single stacks of the electrolytic cells with the minimum total voltage degradation; when the fluctuation power supply power is larger than the product of the number of the single stacks of the electrolytic cell and the turning power point, the load is increased at the moment, and the excess power is evenly distributed to the single stacks of the electrolytic cell; when the fluctuating mains power is reduced, the power of the cell stack with the greatest total voltage degradation is preferentially reduced until the operation is stopped.
The fuzzy control module is used for supplying power to the single cell stack by adopting a Buck converter based on fuzzy PID control, the Buck converter is of a double-input and three-output structure, the double-input represents a power difference E and a difference change rate EC of the actual running power of the single cell stack and the distributed power of the system, and the three-output represents an output dynamic PID parameter K p 、K i 、K d Control is completed for PID controller, K p Representing the proportionality coefficient, K i Represent the integration time constant, K d Representing the differential time constant.
The total voltage degradation calculation module calculates total voltage degradation delta V of the single cell stack d The expression of (2) is:
ΔV d ＝n el ·(t m ·V m +t fl ·V fl +t ct ·V ct +t fh ·V fh +t cr ·V cr )
wherein V is m 、V fl 、V ct 、V fh And V cr Respectively represents voltage degradation rate under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation, t m 、t fl 、t ct 、t fh And t cr The operation time is respectively the operation time under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation.
The single cell stack in the multi-stack electrolyser hydrogen production system further includes an external power source for maintaining a minimum operating voltage of the single cell stack when no power is input.
The foregoing embodiments may be combined in any way, and all possible combinations of the features of the foregoing embodiments are not described for brevity, but only the preferred embodiments of the invention are described in detail, which should not be construed as limiting the scope of the invention. The scope of the present specification should be considered as long as there is no contradiction between the combinations of these technical features.
It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (10)
1. A multi-stack electrolytic cell power distribution method suitable for rapid power impact is characterized in that: the method comprises the following steps:
step S1: constructing a multi-stack electrolyzer hydrogen production system, wherein the multi-stack electrolyzer hydrogen production system comprises a fluctuation power supply and a plurality of electrolyzer single stacks which adopt parallel topology, and each electrolyzer single stack comprises an electrolyzer and a DC/DC converter;
step S2: calculating the operation efficiency of the single cell stack based on the voltage efficiency, faraday efficiency and auxiliary machine efficiency of the single cell stack;
step S3: calculating the total voltage degradation of the single stack of the electrolytic tank based on the voltage degradation rate and the operation efficiency of the single stack of the electrolytic tank under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation;
step S4: setting turning power points and performing power distribution;
the power distribution method comprises the following steps:
step S41: ranking based on total voltage degradation of each of the single stacks of cells;
step S42: when the fluctuation power supply power is smaller than the product of the number of the single stacks of the electrolytic cells and the turning power point, carrying out step-by-step delivery operation according to the sequencing sequence of the step S41, and preferentially operating the single stacks of the electrolytic cells with the minimum total voltage degradation;
step S43: when the fluctuation power supply power is larger than the product of the number of the single stacks of the electrolytic cells and the turning power point, the load is increased, and the excess power is evenly distributed to the single stacks of the electrolytic cells;
step S44: when the fluctuating mains power is reduced, the power of the cell stack with the greatest total voltage degradation is preferentially reduced until the operation is stopped.
2. A multi-stack electrolyzer power distribution method adapted to rapid power surge according to claim 1, characterized in that: the cell stack in step S1 further comprises an external power source for maintaining a minimum operating voltage of the cell stack when no power is input.
3. A multi-stack electrolyzer power distribution method adapted to rapid power surge according to claim 1, characterized in that: in the step S2, the expression for calculating the operation efficiency of the electrolytic cell single stack is as follows:
η el ＝η V ·η F ·η ae
wherein eta is el Indicating the total efficiency of the single stack of the electrolytic cell eta V Representing the voltage efficiency, eta of the single stack of the electrolytic cell F Representing Faraday efficiency, eta of a single stack of an electrolytic cell ae Representing the auxiliary machine efficiency of the electrolytic cell single pile;
wherein V is th Representing the thermal neutral voltage of the single stack of the electrolytic cell, V cell The cell voltage of the cell stack is represented, p represents the cell internal operating pressure of the cell stack, and i represents the cell current density of the cell stack.
4. A multi-stack electrolyzer power distribution method adapted to rapid power surge according to claim 1, characterized in that: in step S3, the total voltage degradation DeltaV of the single stack of the electrolytic tank is calculated d The expression of (2) is:
ΔV d ＝n el ·(t m ·V m +t fl ·V fl +t ct ·V ct +t fh ·V fh +t cr ·V cr )
wherein V is m 、V fl 、V ct 、V fh And V cr Respectively represents voltage degradation rate under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation, t m 、t fl 、t ct 、t fh And t cr The operation time is respectively the operation time under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation.
5. A multi-stack electrolyzer power distribution method adapted to fast power shocks as recited in claim 4 characterized by: and the power distribution adopts a Buck converter based on fuzzy PID control to supply power to each electrolytic cell single stack.
6. A multi-stack electrolyzer power distribution method adapted to fast power shocks as recited in claim 5 characterized by: the Buck converter adopts a double-input and three-output structure, wherein the double-input represents a power difference E and a difference change rate EC of the actual running power of a single stack of an input electrolytic tank and the distributed power of a system, and the three-output represents an output dynamic PID parameter K p 、K i 、K d Control is completed for PID controller, K p Representing the proportionality coefficient, K i Represent the integration time constant, K d Representing the differential time constant.
7. A multi-stack electrolyzer power distribution method adapted to fast power shocks as recited in claim 6 characterized by: the Buck converter adopts a fuzzy set { NB, NM, NS, ZO, PS, PM, PB } of seven variables to define a power difference E and a change rate EC, a membership function selects a triangle function, a fuzzy selection is performed by solving the fuzzy selection to obtain a final output value of fuzzy reasoning by taking the center of gravity of a curve of the fuzzy membership function and the area of a horizontal coordinate surrounding city as a final output value, and a fuzzy rule table is established to continuously adjust and output a dynamic PID parameter K p 、K i 、K d NB represents negative big, NM represents negative middle, NS represents negative small, ZO represents zero, PS represents middle, PB represents positive big.
8. A multi-stack electrolytic cell power distribution system suitable for rapid power impact is characterized in that: the system comprises a multi-stack electrolytic cell hydrogen production system, an operation efficiency calculation module, a total voltage degradation calculation module, a power distribution module and a fuzzy control module;
the multi-stack electrolyzer hydrogen production system comprises a fluctuation power supply and a plurality of electrolyzer single stacks which adopt parallel topology, wherein each electrolyzer single stack comprises an electrolyzer and a DC/DC converter;
the operation efficiency calculation module is used for calculating the operation efficiency of the single cell stack based on the voltage efficiency, faraday efficiency and auxiliary machine efficiency of the single cell stack and outputting the operation efficiency to the total voltage degradation calculation module;
the total voltage degradation calculation module is used for calculating the total voltage degradation of the single stack of the electrolytic tank based on the voltage degradation rate under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation, constant rated power operation and the operation efficiency of the single stack of the electrolytic tank;
the power distribution module is used for setting turning power points and distributing power based on the total voltage degradation;
the power distribution method comprises the following steps: ranking based on total voltage degradation of each of the single stacks of cells; when the fluctuation power supply power is smaller than the product of the number of the single stacks of the electrolytic cells and the turning power point, carrying out step-by-step delivery operation according to a sequencing order, and preferentially operating the single stacks of the electrolytic cells with the minimum total voltage degradation; when the fluctuation power supply power is larger than the product of the number of the single stacks of the electrolytic cells and the turning power point, the load is increased, and the excess power is evenly distributed to the single stacks of the electrolytic cells; when the fluctuation power supply power is reduced, preferentially reducing the power of the electrolytic cell single stack with the maximum total voltage degradation until stopping operation;
the fuzzy control module is used for supplying power to the single cell stack by adopting a Buck converter based on fuzzy PID control, the Buck converter is of a double-input and three-output structure, the double-input represents a power difference E and a difference change rate EC of the actual running power of the single cell stack and the distributed power of the system, and the three-output represents an output dynamic PID parameter K p 、K i 、K d Control is completed for PID controller, K p Representing the proportionality coefficient, K i Represent the integration time constant, K d Representing the differential time constant.
9. A multi-stack electrolyzer power distribution system adapted to fast power surge as recited in claim 8 characterized by: the total voltage degradation calculation module calculates the total voltage degradation delta V of the single cell stack d The expression of (2) is:
ΔV d ＝n el ·(t m ·V m +t fl ·V fl +t ct ·V ct +t fh ·V fh +t cr ·V cr )
wherein V is m 、V fl 、V ct 、V fh And V cr Respectively represents voltage degradation rate under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation, t m 、t fl 、t ct 、t fh And t cr The operation time is respectively the operation time under the working conditions of maintenance operation, low-power fluctuation operation, constant turning power operation, high-power fluctuation operation and constant rated power operation.
10. A multi-stack electrolyzer power distribution system adapted to fast power surge as recited in claim 8 characterized by: the single cell stack in the multi-stack hydrogen production system further includes an external power source for maintaining a minimum operating voltage of the single cell stack when no power is input.
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