CN114937795B - Method for widening working range of solid oxide fuel cell system - Google Patents
Method for widening working range of solid oxide fuel cell system Download PDFInfo
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- 239000000446 fuel Substances 0.000 title claims abstract description 165
- 238000000034 method Methods 0.000 title claims abstract description 32
- 239000007787 solid Substances 0.000 title claims abstract description 17
- 230000033228 biological regulation Effects 0.000 claims abstract description 51
- 230000002829 reductive effect Effects 0.000 claims abstract description 48
- 230000001105 regulatory effect Effects 0.000 claims description 28
- 230000001276 controlling effect Effects 0.000 claims description 22
- 238000011084 recovery Methods 0.000 claims description 8
- 239000002918 waste heat Substances 0.000 claims description 8
- 230000004044 response Effects 0.000 abstract description 11
- 230000008859 change Effects 0.000 abstract description 9
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 9
- 239000000306 component Substances 0.000 description 8
- 230000007423 decrease Effects 0.000 description 7
- 230000003321 amplification Effects 0.000 description 5
- 230000000670 limiting effect Effects 0.000 description 5
- 238000003199 nucleic acid amplification method Methods 0.000 description 5
- 230000035939 shock Effects 0.000 description 5
- 230000008569 process Effects 0.000 description 4
- 230000003247 decreasing effect Effects 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000008358 core component Substances 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000036961 partial effect Effects 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
- H01M8/04858—Electric variables
- H01M8/04895—Current
- H01M8/0491—Current of fuel cell stacks
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
- H01M8/04746—Pressure; Flow
- H01M8/04753—Pressure; Flow of fuel cell reactants
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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
- Y02E60/50—Fuel cells
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Abstract
The invention discloses a method for widening the working range of a solid oxide fuel cell system, which comprises the following steps: when the external electric load is increased from the initial load to the first load, adopting a regulation mode for controlling the fuel flow; when the external electric load is increased from the initial load to the second load, adopting a regulation and control mode for controlling the fuel utilization rate; when the external electric load is reduced from the initial load to the third load, adopting a regulation mode of control voltage; when the external electric load is reduced from the initial load to the fourth load, adopting a regulation and control mode for controlling the fuel utilization rate; wherein the second load is greater than the first load and the fourth load is less than the third load. Therefore, the method can select corresponding regulation and control modes according to the external load change condition and the application range of each regulation and control mode, so that the system is always in a safe and efficient operation interval; and the load response range is widened, so that the system can realize wider power output, and the system working range is widened.
Description
Technical Field
The invention belongs to the technical field of fuel cells, and particularly relates to a method for widening the working range of a solid oxide fuel cell system.
Background
The Solid Oxide Fuel Cell (SOFC) is a device capable of directly converting chemical energy in fuel into electric energy, has the advantages of high power generation efficiency, wide fuel applicability, less emission and the like, and has good application prospects in the fields of distributed energy sources, mobile power sources, household energy systems and the like. SOFC systems generally include SOFC stacks, burners, reformers, heat exchangers, power components, control cabinets, and the like, and can supply electric power to the outside or realize cogeneration.
SOFC systems typically operate steadily under set conditions, but when external loads change, the system is required to respond quickly to the changing loads. However, the operating temperature of the galvanic pile, which is a core component of the system, is typically between 700 ℃ and 800 ℃, has a strong thermal inertia, and cannot respond quickly to load changes. Thus, maintaining the stability of the stack thermal balance during load response is one of the critical issues.
In addition, the output power of the system is related to parameters such as fuel flow, fuel utilization rate, working current, working voltage, working temperature and the like, the influence mechanism is complex, and the system parameters have an operation range. Therefore, the method for widening the working range of the solid oxide fuel cell system has the characteristics of high load response and great significance if the method can be provided for ensuring that the system operates in a safe interval under different output working conditions and maintaining the high efficiency of the system.
Disclosure of Invention
In order to improve the technical problem, the present invention provides a method for widening the operating domain of a solid oxide fuel cell system, wherein an electrical load of the system when the system is operated under an initial working condition is an initial load, and the method comprises:
when the external electric load is increased from the initial load to the first load, adopting a regulation and control mode for controlling the fuel flow;
when the external electric load is increased from the initial load to the second load, adopting a regulation and control mode for controlling the fuel utilization rate;
when the external electric load is reduced from the initial load to a third load, adopting a control mode of control voltage;
when the external electric load is reduced from the initial load to a fourth load, adopting a regulation and control mode for controlling the fuel utilization rate;
wherein the second load is greater than the first load and the fourth load is less than the third load.
Therefore, the corresponding regulation and control modes can be selected according to the external load change condition and the application range of each regulation and control mode, so that the system can quickly respond when facing load changes of different degrees, and the working range of the system is widened. The method adopts the combination of a plurality of regulation modes, so that the system is always in a safe and efficient operation interval; the load response range is also widened, so that the system can realize wider power output.
In addition, in the regulation and control process, the heat load of the electric pile is stable and unchanged, the temperature of the electric pile does not fluctuate severely, and the thermal shock and the performance attenuation caused by the thermal shock are avoided.
According to an embodiment of the present invention, the regulation manner for controlling the fuel flow includes: and maintaining the constant fuel flow of the system, and regulating the output current of the electric pile through the controller to ensure that the output power of the system is the same as that of an external electric load.
According to an embodiment of the invention, when the external electrical load is raised from the initial load to the first load, the output current of the stack is increased by adjusting the controller, and the air flow of the system is increased by adjusting the air valve.
According to an embodiment of the present invention, the regulation and control manner for controlling the fuel utilization rate includes: the fuel flow of the system is regulated through a fuel valve, and the output current of the electric pile is regulated through a controller, so that the output power of the system is the same as that of an external electric load; wherein, the fuel flow and the output current are equal in proportion, and the fuel utilization rate of the system is stable and unchanged.
According to an embodiment of the invention, when the external electrical load is raised from the initial load to a second load, the fuel flow is increased by adjusting the fuel valve, the output current of the stack is increased by adjusting the controller, and the air flow of the system is increased by adjusting the air valve.
According to an embodiment of the invention, when the external electrical load is reduced from the initial load to a fourth load, the fuel flow is reduced by adjusting the fuel valve, the output current of the stack is reduced by adjusting the controller, and the air flow of the system is reduced by adjusting the air valve.
According to an embodiment of the present invention, the control voltage regulation manner includes: the fuel flow of the system is regulated through a fuel valve, and the output current of the electric pile is regulated through a controller, so that the output power of the system is the same as that of an external electric load, and the voltage of the system is kept stable.
According to an embodiment of the present invention, when the external electric load is reduced from the initial load to the third load, the output current of the stack is reduced by adjusting the controller, the fuel flow rate of the system is reduced by adjusting the fuel valve, and the air flow rate of the system is reduced by adjusting the air valve.
According to the embodiment of the invention, under the initial working condition, the system output power is initial power, under the first load, the system output power is first power, under the second load, the system output power is second power, under the third load, the system output power is third power, and under the fourth load, the system output power is fourth power; the first power, the second power are both greater than the initial power, and the second power is greater than the first power; the third power, the fourth power are each less than the initial power, and the fourth power is less than the third power.
According to an embodiment of the present invention, the first power is increased by a first increase in comparison with the initial power, the first increase being greater than 0 and less than or equal to 5%; the second power is increased by a second increase compared with the initial power, wherein the second increase is more than 5% and less than or equal to 15%; the third power is increased by a third increase compared with the initial power, wherein the third increase is more than or equal to-4% and less than 0; the fourth power is increased by a fourth increase of-20% or more and less than-4% as compared with the initial power.
According to an embodiment of the invention, the solid oxide fuel cell system comprises a fuel pump, a fuel preheater, a reformer, an SOFC stack, a combustor, a blower, an air preheater, a waste heat recovery component, an AC-DC converter, and a controller; the fuel pump is connected with the fuel preheater through a first pipeline, and a fuel valve is arranged on the first pipeline; the fuel preheater is connected with the reformer, and the reformer is connected with the SOFC stack; the air blower is connected with the air preheater through a second pipeline, and an air valve is arranged on the second pipeline; the air preheater is connected with the SOFC stack; the SOFC stack is connected with the burner, the burner is connected with the reformer, the reformer is connected with the air preheater, the air preheater is connected with the fuel preheater, and the fuel preheater is connected with the waste heat recovery component; the SOFC stack is connected with the AC/DC converter, and the controller is respectively connected with the AC/DC converter, the fuel valve and the air valve.
Drawings
Fig. 1 is a schematic structural view of a solid oxide fuel cell system of the present invention;
fig. 2 is a discharge curve of an SOFC stack in one embodiment of the present invention.
Detailed Description
Embodiments of the present application are described in detail below. The embodiments described below are exemplary only for the purpose of illustrating the present application and are not to be construed as limiting the present application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents used were not manufacturer-identified and were all commercially available conventional products.
Referring to fig. 1, a solid oxide fuel cell system includes a fuel pump, a fuel preheater, a reformer, an SOFC stack (SOFC in fig. 1), a burner, a blower, an air preheater, a waste heat recovery component, an AC-DC converter (DC/AC in fig. 1), a controller, the fuel pump being connected to the fuel preheater through a first pipe having a fuel valve disposed thereon, the fuel preheater being connected to the reformer, the reformer being connected to the SOFC stack; the air blower is connected with the air preheater through a second pipeline, an air valve is arranged on the second pipeline, and the air preheater is connected with the SOFC stack; the SOFC stack is connected with the burner, the burner is connected with the reformer, the reformer is connected with the air preheater, the air preheater is connected with the fuel preheater, and the fuel preheater is connected with the waste heat recovery component; the SOFC stack is connected with the AC/DC converter, and the controller is respectively connected with the AC/DC converter, the fuel valve and the air valve.
The output current of the SOFC stack can be regulated by a controller. In addition, the controller is connected to an air valve, which can monitor the air flow, through which the air flow of the system can be regulated. The controller is connected with the fuel valve, and the controller can monitor the fuel flow, can adjust the fuel flow of system through the fuel valve.
The fuel pump is used for delivering fuel to the SOFC electric pile, and is connected with the SOFC electric pile through the fuel preheater and the reformer. The blower is used for conveying air to the SOFC electric pile, and the blower is connected with the SOFC electric pile through the air preheater. Excessive fuel in the SOFC stack can be conveyed to a burner, and the burner is connected with a waste heat recovery component through a reformer, an air preheater and a fuel preheater, and the waste heat recovery component is used for supplying heat.
The invention provides a method for widening the operating domain of a solid oxide fuel cell system, wherein the electric load of the system when the system operates under an initial working condition is the initial load, and the method comprises the following steps:
when the external electric load rises from the initial load to the first load, a regulation mode (abbreviated as F-S) for controlling the fuel flow is adopted;
when the external electric load rises from the initial load to the second load, a regulation mode (abbreviated as U-S) for controlling the fuel utilization rate is adopted;
when the external electric load is reduced from the initial load to the third load, adopting a regulation mode (abbreviated as V-S) of control voltage;
when the external electric load is reduced from the initial load to the fourth load, a regulation mode (abbreviated as U-S) for controlling the fuel utilization rate is adopted;
wherein the second load is greater than the first load and the fourth load is less than the third load.
Therefore, the corresponding regulation and control modes can be selected according to the external load change condition and the application range of each regulation and control mode, so that the system can quickly respond when facing load changes of different degrees, the range of the output power of the system can be expanded, the matched load interval of the system can be widened, and the working range of the system can be widened.
In general, the method for widening the working domain of the SOFC system provided by the invention is applicable to various load change situations and has the following beneficial effects: when the external load of the system changes, the method can still ensure that the system can safely and reliably run and maintain high-performance output; in the response process, the temperature of the electric pile is always kept stable, and the quick response can be realized while the thermal shock is avoided; the comprehensive regulation strategy of the invention widens the range of the output power of the system.
It should be emphasized that, since the temperature parameter remains constant at all times, the 3 regulation modes (F-S, U-S, V-S) in the load tracking strategy are only related to the regulation of the flow parameter and the current parameter. The response time of the flow parameter and the current parameter is generally short, so that the strategy can realize the rapid response of the system to external load.
According to an embodiment of the present invention, fig. 2 shows the respective corresponding operating points of the 3 regulation modes on the discharge curve of the SOFC stack, where the abscissa is 0, the curve with the ordinate greater than 1.1 is the curve of the variation of the chip average voltage with the output current, the abscissa is 0, and the curve with the ordinate 0 is the curve of the variation of the chip average power with the output current. As shown in an initial point (a first dotted line from left) and an F-S operating point (a fourth dotted line from left) in fig. 2, the regulation manner for controlling the fuel flow includes: and maintaining the constant fuel flow of the system, and regulating the output current of the electric pile through the controller to ensure that the output power of the system is the same as that of an external electric load. Specifically, the system output power is changed by increasing or decreasing the operating current without changing the system fuel flow. Therefore, the two working points are on the same discharge curve.
According to an embodiment of the invention, when the external electrical load is raised from the initial load to the first load, the output current of the stack is increased by adjusting the controller, and the air flow of the system is increased by adjusting the air valve.
Increasing the output current increases the output power, while decreasing the output current decreases the output power. Thus, by increasing the output current, the output power can be increased. By adjusting the air flow of the system, the temperature of the pile can be kept stable.
When the output power is improved by adopting a regulation and control mode for controlling the fuel flow, the fuel utilization rate and the electric efficiency of the system are correspondingly improved; at the same time, the sheet average voltage decreases, the heat generated by the cell stack increases, and the air flow rate needs to be increased appropriately in order to maintain the temperature of the cell stack stable.
Specifically, the air flow rate is calculated based on the stack heat balance. The stable electric pile temperature can avoid the thermal shock in the electric pile and influence the service life; and can realize the fast tracking of the load.
The method of the invention can maintain the stability of the heat balance of the galvanic pile while realizing the rapid tracking of the system to wider external load, and ensure the safe and efficient operation of the system.
According to an embodiment of the present invention, referring to the initial point (the first dotted line from the left) and the U-S operating point (the third dotted line from the left) in fig. 2, the regulation manner for controlling the fuel utilization (abbreviated as U-S) includes: the fuel flow of the system is regulated through a fuel valve, and the output current of the electric pile is regulated through a controller, so that the output power of the system is the same as that of an external electric load; wherein, the fuel flow and the output current are equal in proportion, and the fuel utilization rate of the system is stable and unchanged. And finally, the system output power is improved or reduced. Therefore, the two working points are respectively on two discharge curves. In addition, when the U-S method is adopted, the stack heat load increases and decreases in the same direction as the output increases and decreases, and therefore, it is necessary to appropriately increase or decrease the air flow rate.
According to an embodiment of the invention, when the external electrical load is raised from the initial load to the second load, the fuel flow is increased by adjusting the fuel valve, the output current of the stack is increased by adjusting the controller, and the air flow of the system is increased by adjusting the air valve.
By increasing the fuel flow and the output current simultaneously, the output power can be increased and the system output power can be adjusted to be the same as the second load. By increasing the air flow rate of the system, the temperature of the pile can be kept stable.
When the output power is improved, the utilization rate of the system fuel is stable and unchanged, the sheet average voltage is slightly reduced, and the electrical efficiency of the system is almost unchanged; at the same time, the heat generated by the electric pile is increased slightly, and the air equivalent ratio is required to be increased to stabilize the temperature of the electric pile.
According to an embodiment of the invention, when the external electrical load is reduced from the initial load to the fourth load, the fuel flow is reduced by adjusting the fuel valve, the output current of the stack is reduced by adjusting the controller, and the air flow of the system is reduced by adjusting the air valve.
By reducing the fuel flow and the output current simultaneously, the output power can be reduced and the system output power can be adjusted to be the same as the fourth load. The heat generated by the electric pile is reduced slightly, and the temperature of the electric pile can be kept stable and unchanged by reducing the air flow rate of the system.
When the output power is reduced, the utilization rate of the system fuel is stable and unchanged, and the sheet average voltage is slightly increased; at the same time, the heat generated by the electric pile is reduced slightly, and the air equivalent ratio is required to be reduced to stabilize the temperature of the electric pile.
According to an embodiment of the present invention, referring to an initial point (a first dotted line from left) and a V-S operating point (a second dotted line from left) in fig. 2, the control voltage is controlled by: the fuel flow of the system is regulated through a fuel valve, and the output current of the electric pile is regulated through a controller, so that the output power of the system is the same as that of an external electric load, and the voltage of the system is kept stable. And finally, the increase or decrease of the output power of the system is realized. Therefore, the two operating points are not on the same discharge curve, but have the same discharge voltage.
According to an embodiment of the present invention, when the external electric load is reduced from the initial load to the third load, the output current of the stack is reduced by adjusting the controller, the fuel flow rate of the system is reduced by adjusting the fuel valve, and the air flow rate of the system is reduced by adjusting the air valve.
Increasing the output current and the fuel flow can increase the output power, and decreasing the output current and the fuel flow can decrease the output power; by adjusting the air flow of the system, the temperature of the pile can be kept stable.
When the V-S mode is adopted, the output power of the system is improved, the fuel utilization rate of the system can be rapidly reduced, and the electrical efficiency of the system is rapidly reduced, so that the method is suitable for the situation of reducing the external load.
When the V-S mode is adopted, when the output power is reduced, the fuel flow is rapidly reduced, and the fuel utilization rate and the electrical efficiency of the system are rapidly increased; at the same time, the heat generated by the electric pile is slightly reduced, and the air flow is required to be reduced so as to maintain the temperature stability of the electric pile.
According to the embodiment of the invention, under the initial working condition, the system output power is initial power, under the first load, the system output power is first power, under the second load, the system output power is second power, under the third load, the system output power is third power, and under the fourth load, the system output power is fourth power; the first power, the second power are both greater than the initial power, and the second power is greater than the first power; the third power, the fourth power are each less than the initial power, and the fourth power is less than the third power. Therefore, a person skilled in the art can select a corresponding regulation mode according to the change condition of the output power of the system under different loads.
According to an embodiment of the present invention, the first power is increased by a first increase in comparison with the initial power, the first increase being greater than 0 and less than or equal to 5%; the second power is increased by a second increase compared with the initial power, wherein the second increase is more than 5% and less than or equal to 15%; the third power is increased by a third increase compared with the initial power, wherein the third increase is more than or equal to-4% and less than 0; the fourth power is increased by a fourth increase of-20% or more and less than-4% as compared with the initial power. It should be noted that, the conditions satisfied by the different modes of the system operation domain method for widening the operation parameters in the solid oxide fuel cell system when the operation parameters in the method of the present invention are fixed are only for exemplary purposes, but not for limiting the present invention, that the first amplification is greater than 0 and less than or equal to 5%, the second amplification is greater than 5% and less than or equal to 15%, the third amplification is greater than or equal to-4% and less than 0, and the fourth amplification is greater than or equal to-20% and less than-4%. That is, when some operating parameters of the solid oxide fuel cell system are changed, even if the first gain is not within the range of greater than 0 and less than or equal to 5%, the control manner of controlling the fuel flow may be adopted, for example, in other embodiments, when the first gain is greater than 0 and less than or equal to 10%, specifically, when the first gain is 8%, the control manner of controlling the fuel flow is adopted, which is still within the scope of the present invention.
That is, the specific conditions satisfied by the different regulation modes of the system operation domain widening method are not fixed, and the conditions can be adjusted according to the operation parameters of the solid oxide fuel cell system, but the general trend of adopting the different regulation modes is unchanged. The electric load of the system when running under the initial working condition is the initial load, when the second load is larger than the first load and the fourth load is smaller than the third load, the method can be adopted, and particularly, when the external electric load is lifted from the initial load to the first load, a regulation mode for controlling the fuel flow is adopted; when the external electric load is increased from the initial load to the second load, adopting a regulation and control mode for controlling the fuel utilization rate; when the external electric load is reduced from the initial load to a third load, adopting a control mode of control voltage; and when the external electric load is reduced from the initial load to a fourth load, adopting a regulation mode for controlling the fuel utilization rate.
In order to ensure that the system is always in a safe operation interval in the regulation and control process, the method for widening the operation domain of the solid oxide fuel cell system has two judgment criteria, namely a fuel utilization rate criterion and a sheet average voltage criterion.
The fuel utilization criteria requirement means that the adjusted system fuel utilization should be below the upper fuel utilization limit. I.e. during regulation, the fuel utilization of the system cannot be higher than a certain value, for example 80%. Too high a fuel utilization rate may cause a fuel shortage phenomenon at an anode runner near an outlet inside the stack, thereby affecting system performance and life.
The upper limit of the fuel utilization rate can be obtained through a pile discharge curve experiment, and the situation that the pile has partial fuel deficiency can be effectively avoided when the fuel utilization rate is lower than the upper limit, so that the performance of the pile is ensured not to be attenuated rapidly.
The rule of the sheet average voltage requires that the regulated sheet average voltage should be within the upper and lower limit intervals of the voltage, i.e. the battery sheet average voltage should be within a certain range, for example 0.65V-0.85V in the regulation process. Too low chip average voltage can directly reduce the system performance and also reduce the service life of the system; too high a chip average voltage can reduce the system power density, rendering the system impractical.
The upper voltage limit may be based on the system nominal sheet average voltage, typically higher than the nominal sheet average voltage; the lower voltage limit is determined according to a pile discharge curve experiment.
It should be emphasized that the specific values in the constraint criteria mentioned above are only referenced. In practical application, a reasonable constraint range should be formulated according to the pile performance, so that the safe operation of the system is ensured.
The invention will now be described with reference to specific examples, which are intended to be illustrative only and not limiting in any way.
Initially, the system stably operates under an initial working condition, and the output power of the system is P 0 The working current is I 0 The working voltage is V 0 The fuel flow is m fuel,0 Air flow is m air,0 The fuel utilization rate of the system is u F0 。
When the external load is increased to P 1 And is connected with P 0 When the contrast increase is less than or equal to 5%, the F-S mode is adopted for regulation and control.
After adjustment, the fuel flow of the system is kept unchanged and is still m fuel,0 The working current is increased to I 1 The output power corresponding to the current is P 1 . And adjust the air flow to m air,1 To maintain the thermal load of the pile stable and unchanged. Under the working condition, the working voltage and the fuel utilization rate are respectively V 1 And u F1 。
When the external load is increased to P 2 And is connected with P 0 When the compared amplification is more than 5%, the U-S mode is adopted for regulation and control.
After adjustment, the fuel utilization rate of the system is kept unchanged and is u F0 Equal proportion of operating current and fuel flow increases to I 2 And m fuel,2 The corresponding output power is P 2 . Air flow is adjusted to m air,2 The voltage at this time is V 2 。
When the external load is reduced to P 3 And is connected with P 0 When the amplitude reduction is not more than 4%, the V-S mode is adopted for regulation and control.
After the adjustment, the system voltage is kept unchanged and is V 0 The working current and the fuel flow are adjusted to I 3 And m fuel,3 The corresponding output power is P 3 . At this time, the fuel utilization rate of the system is u F3 The air flow is adjusted to m air,3 。
When the external load is reduced to P 4 And is connected with P 0 When the reduction is more than 4%, the U-S mode is adopted for regulation and control.
After adjustment, the fuel utilization rate of the system is still u F0 The equal proportion of the working current and the fuel flow is reduced to I 4 And m fuel,4 The corresponding output power is P 4 . Air flow is adjusted to m air,4 The voltage at this time is V 4 。
Table 1 lists design parameters of each key component of the 1kW methanol SOFC cogeneration system, and table 2 sets the state corresponding to each parameter in table 1 as an initial working condition, and sets the state corresponding to small increase of external load as working condition 1 compared with the initial working condition; compared with the initial working condition, the state corresponding to the greatly increased external load is the working condition 2; the state corresponding to the small reduction of the external load is working condition 3 compared with the initial working condition; the state corresponding to the greatly reduced external load compared with the initial working condition is working condition 4, and the operating parameters of the system under the 5 working conditions are listed in table 2.
TABLE 1kW methanol SOFC cogeneration System design parameters
Table 2 5 operating parameters of 1kW methanol SOFC cogeneration system
| Initial condition of operation | Working condition 1 | Working condition 2 | Working condition 3 | Working condition 4 | |
| Fuel flow rate | 7.8g/min | 7.8g/min | 8.9g/min | 6.9g/min | 6.8g/min |
| Air flow rate | 82L/min | 95L/min | 105L/min | 79L/min | 64L/min |
| Fuel utilization rate | 73.3％ | 78.4％ | 73.5％ | 79.9％ | 73.4％ |
| Sheet average voltage | 0.8V | 0.778V | 0.768V | 0.8V | 0.826V |
| Discharge current | 62.5A | 66.8A | 71.6A | 60.0A | 54.5A |
| Electric power | 1000W | 1040W | 1100W | 960W | 900W |
| Electric efficiency | 38.1％ | 39.7％ | 36.7％ | 41.5％ | 39.4％ |
| Pile heat load | 100W | 100W | 101W | 99W | 100W |
As can be seen from Table 2, when the external load fluctuates by + -100W around 1000W of the initial power of the system, the load response strategy provided by the invention can be adopted to realize the adjustment of the output power of the system within the range of + -10%. The system electrical efficiency also varies around 38.1% of the initial electrical efficiency, at a minimum not less than 36.7%, and the system operating parameters are all within the safe zone. At the same time, the heat load of the electric pile is always kept near the initial value of 100W, and no thermal shock exists inside the electric pile.
In this embodiment, the safety interval constraint conditions used are: 1. the fuel utilization rate is less than or equal to 80 percent; 2. the sheet average voltage is between 0.75V and 0.85V.
Based on the constraint criteria, the application ranges of the respective control modes in the response strategies of the present embodiment are listed in table 3 below.
Table 3 application ranges of the respective regulation modes
| Power interval | Amplitude of variation | Control mode |
| 800W–960W | -20％--4％ | U-S mode |
| 960W-1000W | -4％-0％ | V-S mode |
| 1000W | 0％ | Initial power |
| 1000W–1050W | 0％-+5％ | F-S mode |
| 1050W–1150W | +5％-+15％ | U-S mode |
Table 3 shows the final response strategy of this example. In the embodiment, the system can track the external load change in real time near the rated working point, and the corresponding regulation and control mode is selected according to the load change condition by tracking the load change, so that the application range is-20% to +15%, the daily operation requirement of the system can be met, and the working field of the system is widened.
Although the invention has been described above with reference to the accompanying drawings and simulation examples, it is to be understood that the invention is not limited to the specific embodiment. But not limited thereto, it will be apparent to those skilled in the art that various modifications and variations can be made without inventive work by those skilled in the art, on the basis of the technical solutions of the present invention, while remaining within the scope of the present invention.
It should be noted that, in the present specification, the terms "first," "second," "third," "fourth" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
Although embodiments of the present application have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the application, and that variations, modifications, alternatives, and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the application.
Claims (4)
1. A method of widening the operating range of a solid oxide fuel cell system, wherein the electrical load of the system when operating at an initial operating condition is an initial load, the method comprising:
when the external electric load is increased from the initial load to the first load, adopting a regulation and control mode for controlling the fuel flow;
the regulation and control mode for controlling the fuel flow comprises the following steps: maintaining the constant fuel flow of the system, regulating the output current of the electric pile through a controller to enable the output power of the system to be the same as the external electric load, increasing the output current of the electric pile through regulating the controller when the external electric load is lifted to a first load from the initial load, and increasing the air flow of the system through regulating an air valve;
when the external electric load is increased from the initial load to the second load, adopting a regulation and control mode for controlling the fuel utilization rate;
the regulation and control mode for controlling the fuel utilization rate comprises the following steps: the fuel flow of the system is regulated through a fuel valve, the output current of the electric pile is regulated through a controller, the output power of the system is the same as the external electric load, wherein the fuel flow and the output current are in equal proportion, the fuel utilization rate of the system is stable and unchanged, when the external electric load is lifted from the initial load to the second load, the fuel flow is increased through regulating the fuel valve, the output current of the electric pile is increased through regulating the controller, and the air flow of the system is increased through regulating an air valve;
when the external electric load is reduced from the initial load to a third load, adopting a control mode of control voltage;
the control voltage regulation and control mode comprises the following steps: regulating the fuel flow of the system through a fuel valve, regulating the output current of the electric pile through a controller, enabling the output power of the system to be the same as the external electric load, maintaining the voltage of the system to be stable, reducing the output current of the electric pile through the controller when the external electric load is reduced from the initial load to a third load, reducing the fuel flow of the system through the fuel valve, and reducing the air flow of the system through the air valve;
when the external electric load is reduced from the initial load to a fourth load, adopting a regulation and control mode for controlling the fuel utilization rate;
the regulation and control mode for controlling the fuel utilization rate comprises the following steps: the fuel flow of the system is regulated through a fuel valve, the output current of the electric pile is regulated through a controller, the output power of the system is the same as the external electric load, wherein the fuel flow and the output current are in equal proportion, the fuel utilization rate of the system is stable and unchanged, when the external electric load is reduced from the initial load to a fourth load, the fuel flow is reduced through regulating the fuel valve, the output current of the electric pile is reduced through regulating the controller, and the air flow of the system is reduced through regulating an air valve;
wherein the second load is greater than the first load and the fourth load is less than the third load.
2. The method of claim 1, wherein the system output power is an initial power under initial conditions, the system output power is a first power under a first load, the system output power is a second power under a second load, the system output power is a third power under a third load, and the system output power is a fourth power under a fourth load;
the first power, the second power are both greater than the initial power, and the second power is greater than the first power;
the third power, the fourth power are each less than the initial power, and the fourth power is less than the third power.
3. The method of claim 2, wherein the first power is increased by a first increase in comparison to the initial power, the first increase being greater than 0 and less than or equal to 5%;
the second power is increased by a second increase compared with the initial power, wherein the second increase is more than 5% and less than or equal to 15%;
the third power is increased by a third increase compared with the initial power, wherein the third increase is more than or equal to-4% and less than 0;
the fourth power is increased by a fourth increase of-20% or more and less than-4% as compared with the initial power.
4. The method of claim 1, wherein the solid oxide fuel cell system comprises a fuel pump, a fuel preheater, a reformer, an SOFC stack, a combustor, a blower, an air preheater, a waste heat recovery component, an ac-dc converter, a controller;
the fuel pump is connected with the fuel preheater through a first pipeline, and a fuel valve is arranged on the first pipeline;
the fuel preheater is connected with the reformer, and the reformer is connected with the SOFC stack;
the air blower is connected with the air preheater through a second pipeline, and an air valve is arranged on the second pipeline;
the air preheater is connected with the SOFC stack;
the SOFC stack is connected with the burner, the burner is connected with the reformer, the reformer is connected with the air preheater, the air preheater is connected with the fuel preheater, and the fuel preheater is connected with the waste heat recovery component;
the SOFC stack is connected with the AC/DC converter, and the controller is respectively connected with the AC/DC converter, the fuel valve and the air valve.
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