JP2009099414A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system which can reduce a generated surplus power and suppress deterioration of the power generation efficiency of a fuel cell. <P>SOLUTION: An appropriate target value is set by generally judging the value of demanded power in the previous 15 minutes or shorter which is optimal time in consideration of the fluctuation velocity of the generated power of the fuel cell 20 and in consideration of supply of power in response to an increase-decrease tendency in actually demanded power. The fuel cell 20 is controlled in accordance with the target value set in such a manner so that the generated power is not affected by sudden or local fluctuation in demanded power and the fuel cell 20 is further controlled so as to moderate the fluctuation in the generated power. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system that supplies electric power according to demand.

Conventionally, what was described in patent document 1 is known as a technique which supplies electric power according to a demand. Patent Document 1 describes a system that includes a generator that generates electric power by rotating an armature winding with respect to a stator, and that controls the generator so that the generated electric power follows demand power. Yes.
JP 2002-238167 A

  However, when the generator control method as described above is applied to the fuel cell system so that the generated power of the fuel cell follows the demand power, the generated power of the fuel cell is compared with the fluctuation speed of the demand power. Therefore, there is a problem that, for example, when the power demand is suddenly reduced, it takes time until the power generated by the fuel cell decreases, and surplus power is generated. In addition, the fuel cell is a system that adjusts the generated power by controlling the supply amount of fuel and water, and it is difficult to adjust the generated power compared to other power generation systems, and it is desirable to suppress fluctuations in the generated power. However, when power is generated by following demand power that is subject to local fluctuations, the generated power frequently fluctuates, resulting in a problem that power generation efficiency is reduced.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a fuel cell system capable of reducing the generation of surplus power and suppressing a decrease in power generation efficiency of the fuel cell. And

  The fuel cell system according to the present invention includes a fuel cell that generates electric power and a control device that controls the fuel cell, and the control device targets the generated electric power of the fuel cell based on demand power within the past 15 minutes. It comprises a target value setting means for setting a value, and a generated power control means for controlling the fuel cell so as to generate electric power according to the target value.

  According to this fuel cell system, it is the optimum time when considering the fluctuation speed of the generated power of the fuel cell and supplying power in response to the actual increase / decrease in demand power. An appropriate target value can be set by judging the value of power demand within the past 15 minutes as a whole. By following the target value set in this way, the fuel cell can be controlled so that the generated power is not affected by sudden fluctuations or local fluctuations in demand power, and the fluctuations in the generated power are moderate. The fuel cell can be controlled so that As described above, it is possible to reduce the generation of surplus power and to prevent the power generation efficiency of the fuel cell from being lowered.

  In the fuel cell system according to the present invention, the target value setting means preferably sets the target value based on the minimum value of the demand power within the past 15 minutes. In this way, the target value is set based on the minimum value of the demand power within the past 15 minutes even if the demand power fluctuates suddenly or when it fluctuates locally. In addition to eliminating the influence of power fluctuations, it is possible to moderate fluctuations in generated power. As described above, it is possible to reduce the generation of surplus power and to prevent the power generation efficiency of the fuel cell from being lowered.

  According to the fuel cell system of the present invention, it is possible to reduce the generation of surplus power and suppress the decrease in power generation efficiency of the fuel cell.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a block diagram showing the configuration of the fuel cell system according to the embodiment, and FIG. 2 is a block diagram showing the configuration of the control device of FIG. As shown in FIG. 1, the fuel cell system 1 includes a hydrogen production device (FPS) 10, a fuel cell 20, an inverter 30, a control device 40, a burner fuel supply device 50, a hydrogen production raw material supply device 60, and a cooling water supply device. 70, an air supply device 80, a surplus heater 90, and measuring instruments 100 and 110.

  The FPS 10 generates hydrogen-rich reformed gas using the raw material for hydrogen production from the raw material supply device 60 for hydrogen production. As a raw material for hydrogen production, any substance that can obtain a reformed gas containing hydrogen by steam reforming can be used. For example, compounds having carbon and hydrogen in the molecule, such as hydrocarbons, alcohols, and ethers, can be used. Examples of raw materials that can be obtained inexpensively for industrial or consumer use include methanol, ethanol, dimethyl ether, methane, city gas, LPG (liquefied petroleum gas), and carbonized gasoline, naphtha, kerosene, light oil obtained from petroleum, etc. Mention may be made of hydrogen oil. Among these, liquid raw materials are preferable, and kerosene is particularly preferable because it is easily available and easy to handle.

  The FPS 10 includes a reforming unit 11, a burner 12, a shift unit 13, and a selective oxidation unit 14. The reforming unit 11 steam reforms the raw material for hydrogen production using the reforming water, and generates a hydrogen-rich reformed gas. Examples of the reforming catalyst for steam reforming include a catalyst in which a nickel, ruthenium, or rhodium metal is supported on a carrier made of alumina, zirconia, or the like. The burner 12 supplies heat necessary for steam reforming, which is an endothermic reaction. The burner 12 burns fuel from the burner fuel supply device 50 when the fuel cell system 1 is started. Further, the burner 12 burns off-gas that is a surplus of reformed gas discharged without being used in the fuel cell 20.

  The shift unit 13 removes CO in the reformed gas to about several thousand ppm by an aqueous shift reaction using a shift catalyst. Examples of the shift catalyst include a catalyst in which Cu, Zn, Fe, Cr or the like is supported on a carrier made of alumina, zirconia, or the like. The temperature range in which the aqueous shift reaction by the shift catalyst is activated is approximately 200 to 500 ° C., although it varies depending on the type of catalyst.

  The selective oxidation unit 14 removes CO in the reformed gas to about several tens of ppm by selective oxidation using a selective oxidation catalyst. As the selective oxidation catalyst, for example, a catalyst in which Pt, Ru or the like is supported on a carrier made of alumina, zirconia or the like can be mentioned. The temperature range in which the selective oxidation reaction by the selective oxidation catalyst is activated is approximately 120 to 180 ° C., although it varies depending on the type of catalyst. Further, the temperature range in which the reduction of the selective oxidation catalyst is promoted is approximately 200 to 250 ° C., although it varies depending on the type of catalyst. The selective oxidation unit 14 supplies the reformed gas to the fuel cell 20.

  The air supply device 80 supplies air as an oxygen source necessary for the selective oxidation reaction in the selective oxidation unit 14 to the selective oxidation unit 14.

  The cooling water supply device 70 supplies cooling water for cooling the shift unit 13 that performs an aqueous shift reaction that is an exothermic reaction and the selective oxidation unit 14 that performs a selective oxidation reaction that is an exothermic reaction.

  The fuel cell 20 is, for example, a solid polymer type (PEFC) battery stack, and is configured by stacking a plurality of battery cells. The fuel cell 20 generates electric power using the reformed gas generated by the FPS 10, and the inverter 30 Power is supplied to household electrical equipment EI. The battery cell has an anode, a cathode, and a polymer ion exchange membrane that is an electrolyte disposed between the anode and the cathode, and introduces a reformed gas to the anode side and air to the cathode side. By introducing, an electrochemical power generation reaction is performed in each battery cell. The inverter 30 converts the output DC current into an alternating current (AC) current. When the generated power of the fuel cell 20 is less than the demand power of the electric device EI, auxiliary power is supplied from the commercial power system CE to the electric device EI.

  The surplus heater 90 boils hot water, for example, using surplus power when the generated power of the fuel cell 20 exceeds the demand power of the electrical equipment EI.

  The measuring instrument 100 measures the supplied power supplied from the fuel cell 20 to the electric device EI and outputs a measured value of the supplied power to the control device 40. In addition, the measuring instrument 110 measures auxiliary power supplied from the commercial power system CE to the electrical equipment EI and outputs a measured value of auxiliary power to the control device 40.

  The control device 40 is, for example, a device that performs electronic control, and includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output interface, and the like. The input / output interface of the control device 40 includes the fuel cell 20, an ammeter provided therein, a burner fuel supply device 50, a raw material supply device 60 for hydrogen production, a cooling water supply device 70, an air supply device 80, and measuring instruments 100 and 110. In addition, they are logically connected directly or via a network so that signals can be transmitted and received.

  The control device 40 controls the fuel cell 20, and as shown in FIG. 2, a demand power acquisition unit 41, a storage unit 42, a target value setting unit (target value setting means) 43, and a generated power control unit. (Generated power control means) 44.

  The demand power acquisition unit 41 has a function of acquiring demand power from the electrical equipment EI based on the supply power and auxiliary power input from the measuring instruments 100 and 110. Demand power is calculated by the sum of supplied power and auxiliary power. The demand power acquisition unit 41 has a function of outputting the demand power to the storage unit 42 when the demand power is acquired.

  The storage unit 42 has a function of storing a demand power plot drawn by demand power from the past to the present based on the demand power input from the demand power acquisition unit 41. The power demand plot is a graph indicated by Wz in FIGS. The storage unit 42 has a function of outputting a demand power plot to the target value setting unit 43.

  The target value setting unit 43 has a function of setting a target value of generated power of the fuel cell 20 based on the demand power plot input from the storage unit 42. Specifically, the target value setting unit 43 refers to the demand power plot within the past several minutes and sets the minimum value of the demand power in the range as the target value. If the retroactive time is too short, surplus power may be generated due to the influence of the fluctuation speed of the generated power of the fuel cell 20. On the other hand, if it is too long, it responds to the actual increase / decrease in demand power. Therefore, it is preferable to go back to the past 15 minutes, and it is more preferable to go back to the past 5 to 10 minutes. The target value setting unit 43 has a function of outputting the generated power control unit 44 when the target value is set.

  The generated power control unit 44 has a function of controlling the fuel cell 20 so as to generate power according to the target value acquired from the target value setting unit 43. Specifically, the generated power control unit 44 outputs control signals to the burner fuel supply device 50, the raw material supply device 60 for hydrogen production, the cooling water supply device 70, and the air supply device 80. The fuel cell 20 is controlled by adjusting the supply amount of the raw material for production, the supply amount of the cooling water, and the supply amount of air.

  Next, operation | movement of the control apparatus 40 of the fuel cell system 1 which concerns on this embodiment is demonstrated with reference to FIG. FIG. 3 is a flowchart showing the operation of the control device.

  The control device 40 repeatedly executes the control process shown in FIG. 3 at a predetermined timing. First, the control device 40 starts from the demand power acquisition process (S10). The process of S10 is a process that is executed by the demand power acquisition unit 41 and acquires the demand power from the electrical equipment EI. When the process of S10 ends, the process proceeds to a demand power plot acquisition process (S12).

  The process of S <b> 12 is executed by the target value setting unit 43 and acquires a demand power plot from the storage unit 42. The demand power plot is updated each time new demand power is acquired in S10 as time elapses. When the process of S12 ends, the process proceeds to a target value setting process (S14).

  The process of S14 is a process that is executed by the target value setting unit 43 and sets the target value of the generated power of the fuel cell 20 based on the demand power plot acquired in S12.

  Here, the details of the method for setting the target value in S14 will be specifically described with reference to FIG. FIG. 4 is a diagram illustrating a method for setting a target value for the generated power of the fuel cell.

  As shown in FIGS. 4A to 4C, in the demand power plot Wz from the past to the present, the minimum minimum point is P1, the time after the minimum point P1, and the next minimum after the minimum point P1. The minimum point is P3, and the times at that time are T1 and T3, respectively. Further, a point that is the same value as the value of the minimum point P3 between the minimum point P1 and the minimum point P3 is defined as an intermediate point P2, and the time at that time is defined as T2. In the figure, the current time is Tn, and the time that is a predetermined time backward from the present is Tb. When the time is set in this way, the minimum value of the demand power between the time Tn and the time Tb is set as the target value Pd of the generated power of the fuel cell 20.

  As shown in FIG. 4A, when the time Tb is before the time T1, the minimum demand power between the time Tn and the time Tb is given by the demand power at the time T1, that is, the minimum point P1. Therefore, the target value Pd is set to the same value as the demand power at the minimum point P1.

  As shown in FIG. 4B, when the time Tb is after the time T1 and before the time T2, the minimum demand power between the time Tn and the time Tb is the demand power at the time Tb ( (Indicated as Pm in the figure). Therefore, the target value Pd is set to the same value as the demand power at Pm. At this time, the gradient of the target value plot Wt drawn by the target value Pd up to now is the same as the gradient of the demand power plot between the minimum point P1 and the intermediate point P2.

  As shown in FIG. 4C, when time Tb is after time T2 and before time T3, the minimum demand power between time Tn and time Tb is the demand power at time T3, that is, the minimum Given by point P3. Therefore, the target value Pd is set to the same value as the demand power at the minimum point P3.

  Returning to FIG. 3, when the process of S14 is completed, the process proceeds to a generated power control process (S16). The process of S16 is a process that is executed by the generated power control unit 44 and controls the fuel cell 20 so as to generate power according to the target value Pd set in S14. When the process of S16 ends, the power generation process of the fuel cell 20 shown in FIG. 3 ends.

  As described above, when considering the fluctuation speed of the generated power of the fuel cell 20 and supplying power in response to the actual increase / decrease in demand power, the optimum time is within the past 15 minutes. An appropriate target value can be set by judging the value of the demand power of the whole. By following the target value set in this way, it is possible to control the fuel cell 20 so that the generated power is not affected by sudden fluctuations or local fluctuations in the demand power. The fuel cell 20 can be controlled to be gradual. As described above, it is possible to reduce the generation of surplus power and to suppress the power generation efficiency of the fuel cell 20 from being lowered.

  Moreover, even if the demand power fluctuates rapidly or locally, the target value is set based on the minimum value of demand power within the past 15 minutes, so the fluctuation in demand power In addition to eliminating the influence, fluctuations in generated power can be moderated. As described above, it is possible to reduce the generation of surplus power and to suppress the power generation efficiency of the fuel cell 20 from being lowered.

  The present invention is not limited to the embodiment described above.

  In this embodiment, the minimum value of demand power within the past several minutes is set as the target value, but a value obtained by adding several watts of power to the minimum value may be set as the target value. In addition, when there is a local abnormal decrease in demand power, the target value may be set so as to ignore the minimum value at that location.

  In addition, although a polymer electrolyte type (PEFC) type is applied as a fuel cell, other types of fuel such as an alkaline electrolyte type, a phosphoric acid type, a molten carbonate type or a solid oxide type are not limited thereto. It may be a battery.

  Hereinafter, examples and comparative examples implemented by the present inventors will be described in order to confirm the above effects. The results are shown in FIG.

(Comparative example)
In FIG. 5, a graph Wz indicated by a solid line is a demand power plot, and a graph Wh indicated by a dotted line is a plot of the generated power of the fuel cell when control is performed so that the generated power of the fuel cell follows the demand power. is there. As shown in FIG. 5, the fluctuation speed of the demand power is several hundred watts per second, whereas the fluctuation speed of the generated power of the fuel cell is only about several watts per second, and the fluctuation speed is slow. Therefore, if the demand power increases rapidly, the generated power gradually increases, and if the demand power decreases rapidly, the generated power gradually decreases, so that surplus power is generated. In the comparative example, surplus power as indicated by Er in FIG. 5 is generated. In addition, since the generated power fluctuates greatly, the power generation efficiency of the fuel cell decreases.

(Example)
In FIG. 5, a graph Wp indicated by a one-dot chain line refers to a demand power plot within the past 5 minutes and generates a fuel cell when control is performed by setting the minimum value of demand power in the range as a target value. It is a power plot. As shown in FIG. 5, the fuel cell responds to the actual increase / decrease in power demand, but is hardly affected by sudden fluctuations in power demand and generates power without generating surplus power. is doing. In addition, the fluctuation of the generated power is moderate as compared with the comparative example, and this can suppress a decrease in the power generation efficiency of the fuel cell.

It is a block diagram which shows the structure of the fuel cell system which concerns on embodiment. It is a block diagram which shows the structure of the control apparatus of FIG. It is a flowchart which shows operation | movement of a control apparatus. It is a figure which shows the setting method of the target value of the electric power generated of a fuel cell, (a) is time Tb before time T1, (b) is time Tb after time T1 and before time T2. (C) shows a case where the time Tb is after the time T2 and before the time T3. It is a diagram which shows the result of an Example and a comparative example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 20 ... Fuel cell, 40 ... Control apparatus, 43 ... Target value setting part (target value setting means), 44 ... Generated power control part (generated power control means).

Claims (2)

A fuel cell that generates electricity;
A control device for controlling the fuel cell,
The controller is
Target value setting means for setting a target value of generated power of the fuel cell based on demand power within the past 15 minutes;
Generated power control means for controlling the fuel cell so as to generate power according to the target value;
A fuel cell system comprising:   2. The fuel cell system according to claim 1, wherein the target value setting means sets the target value based on a minimum value of the demand power within the past 15 minutes.

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