JP5099992B2 - Fuel cell control device - Google Patents

Description

  The present invention relates to a fuel cell control device that performs output control of a fuel cell, and more particularly to a fuel cell control device in a power supply system in which a fuel concentration in a fuel cell is reduced by power generation.

  The fuel cell has nonlinear output characteristics as shown in FIG. In FIG. 14, curves 161, 162, and 163 represent the relationship between the output current (horizontal axis) of the fuel cell and the output voltage (vertical axis), and curves 171, 172, and 173 indicate the output current ( The relationship between the horizontal axis) and generated power (output power) (vertical axis) is shown.

  As shown in FIG. 14, the generated power increases as the output current increases from zero. When the output current becomes a certain current, the generated power becomes maximum, and when the output current further increases, the generated power decreases rapidly with a rapid decrease in the output voltage.

  Generally, when a current larger than the output current that gives the maximum value to the generated power is drawn from the fuel cell, the fuel cell is deteriorated or damaged. Therefore, in order to use the fuel cell safely, it is important to control so that the operating voltage does not fall below the voltage that gives the maximum value to the generated power.

  In order to extract the maximum power from the fuel cell while ensuring the safe operation of the fuel cell, a technique for determining an operating voltage (operating point) that gives the maximum power using a search method such as a hill-climbing method has been proposed. However, in order to realize such a technique, a large amount of data processing is required, and high-speed control is difficult due to this.

  By the way, in recent years, development of direct methanol fuel cells that generate electricity using methanol as a direct fuel has been actively developed. With respect to this type of fuel cell, there is also a method of mixing methanol and water using a circulation pump or the like (such a method is a kind of so-called active method) in order to obtain a desired fuel concentration in the fuel cell. Proposed. However, since a circulation pump or the like is necessary, the scale of the system increases, and it becomes difficult to mount it on a portable device.

  A so-called passive system that does not use a circulation pump or the like for controlling the concentration of methanol has been proposed in order to be mounted on a portable device. When the passive method is adopted, the fuel concentration in the fuel cell is reduced by power generation. When the fuel concentration decreases, the output current-output voltage characteristics change from curves 161 to 162 and 163, and the output current-output power characteristics change from curves 171 to 172 and 173. In other words, the output characteristics of the fuel cell change due to the change in the fuel concentration, and the voltage region (current region) in which the fuel cell can be safely used also changes.

  Even when the passive method is adopted, of course, control to ensure the safe operation of the fuel cell is necessary. However, if a concentration sensor or the like is installed to detect the fuel concentration in the fuel cell, it is disadvantageous in terms of cost and size. This is particularly unsuitable for portable devices.

  Patent Document 1 listed below discloses a technique for estimating an output current / voltage characteristic of a fuel cell using internal data and determining a required output voltage and a required output current based on the estimated output current / voltage characteristic. ing.

JP 2003-86211 A

  The actual situation is that an appropriate fuel cell control device (for example, having a simple configuration) used for a power supply system in which the fuel concentration in the fuel cell is reduced by power generation has not been proposed. For the sake of specific explanation, the problems of the prior art have been described focusing on the passive method, but it is important to ensure the safety of the operation of the fuel cell regardless of the classification of the passive method.

  Therefore, an object of the present invention is to provide a fuel cell control device that can operate a fuel cell safely with a simple configuration.

  In order to achieve the above object, a first fuel cell control device according to the present invention includes a total generated power amount detecting unit that detects a total generated power amount of a fuel cell, and the detected total generated power amount based on the detected total generated power amount. A lower limit voltage setting unit for setting a lower limit voltage of the output voltage of the fuel cell; a voltage converter provided on the output side of the fuel cell; and controlling the voltage converter so that the output voltage does not fall below the lower limit voltage And a control unit.

  Specifically, for example, the first fuel cell control device is used in a power supply system in which the fuel concentration in the fuel cell is reduced by power generation. In a power supply system in which the fuel concentration decreases with power generation, the fuel concentration decreases as the total power generation amount increases. On the other hand, the lower limit of the output voltage at which the fuel cell can be safely used varies with the change in the fuel concentration due to the characteristics of the fuel cell. Considering this, the lower limit voltage of the output voltage of the fuel cell is set based on the total amount of generated power, and control is performed so that the output voltage does not fall below the lower limit voltage. That is, according to said structure, it becomes possible to operate a fuel cell safely with a simple structure.

  Specifically, for example, the lower limit voltage setting unit increases the lower limit voltage to be set as the detected total amount of generated power increases.

  Further, for example, the lower limit voltage setting unit sets the lower limit voltage using a predetermined first function that represents a relationship between the detected total generated power amount and the lower limit voltage to be set.

  If the lower limit voltage is set using a function, it is possible to expect speeding up and simplification of processing.

  For example, the lower limit voltage is set to a voltage that does not fall below the output voltage of the fuel cell when the maximum electric power is output from the fuel cell.

  In addition, for example, a second function representing a relationship between a set voltage to be followed by the output voltage of the fuel cell and the total generated power amount is determined in advance, and the set voltage is always the same for the same total generated power amount. The control unit controls the voltage converter in accordance with the set voltage specified by the second function.

  If the second function is appropriately set according to the characteristics of the fuel cell, etc., the most desirable power in relation to the total power generation amount (for example, the maximum power that can be extracted or power approximate to it) is generated by the fuel cell. Control becomes possible, and high energy efficient operation of the fuel cell can be expected. In addition, since the set voltage is always equal to or higher than the lower limit voltage at the same total generated electric energy, safe operation of the fuel cell is ensured. Furthermore, if the set voltage is determined using a function, it is possible to expect speeding up and simplification of processing.

  For example, a load and a secondary battery may be connected in parallel on the output side of the voltage converter.

  When the output voltage of the fuel cell is made to follow a desired set voltage, a predetermined power is generated according to the set voltage. In this case, when surplus power that is not consumed by the load is generated, the secondary battery is charged by the surplus power, and the insufficient power for the load is covered by the discharge of the secondary battery. As described above, by connecting the secondary batteries in parallel to the load, it is possible to effectively use the electric power according to the light weight of the load.

  Further, for example, a temperature detection unit that detects a temperature of the fuel cell or a temperature around the fuel cell is further provided, and the lower limit voltage setting unit is based not only on the total amount of generated power but also on the detected temperature. Set the lower limit voltage.

  Fuel cells change their output characteristics due to the effects of self-heating due to chemical reactions and ambient temperature, and the safe operating area changes accordingly, but also based on the fuel cell temperature or ambient temperature as described above. If the lower limit voltage is set, the fuel cell can be operated more safely.

  In addition, for example, a temperature detection unit that detects a temperature of the fuel cell or a temperature around the fuel cell is further provided, and the set voltage specified by the second function and the total generated power amount is detected. Correction is performed based on the temperature, and the control unit controls the voltage converter according to the corrected set voltage.

  This also enables safer operation of the fuel cell.

  In addition, for example, when the output voltage falls below the lower limit voltage despite the control of the voltage converter by the control unit, the control unit may disconnect the load and the fuel cell.

  In addition, for example, when the output voltage falls below the lower limit voltage despite the control of the voltage converter by the control unit, the control unit causes the voltage converter to stop the power generation of the fuel cell. You may control.

  Unexpected deterioration or breakage of the fuel cell can be prevented by disconnecting the load and the fuel cell or by stopping power generation.

  Further, for example, a control signal output unit that outputs a control signal for notifying the remaining amount of fuel when the detected total generated power amount reaches a predetermined set power amount may be further provided.

  In order to achieve the above object, the second fuel cell control device according to the present invention includes a control unit that changes the output voltage of the fuel cell in accordance with an elapsed time from a predetermined reference time point. And

  Specifically, for example, the control unit increases the output voltage as the elapsed time increases.

  In order to achieve the above object, a third fuel cell control device according to the present invention includes a control unit that changes the output voltage of the fuel cell according to the power generation time of the fuel cell. .

  Specifically, for example, the control unit increases the output voltage as the power generation time increases.

  Specifically, for example, the second or third fuel cell control device is used in a power supply system in which the fuel concentration in the fuel cell is reduced by power generation. According to the second or third fuel cell control device, the fuel cell can be safely operated with a simpler configuration.

  As described above, according to the fuel cell control device of the present invention, the fuel cell can be safely operated with a simple configuration.

<< First Embodiment >>
Hereinafter, a fuel cell power supply system according to a first embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing a cell structure of a fuel cell (fuel cell main body) 1 used in each embodiment of the present invention.

  The fuel cell 1 is a direct methanol fuel cell that generates electricity using methanol as a direct fuel, and includes a fuel electrode 31 that supports an electrode catalyst for promoting methanol oxidation, and an electrode catalyst for promoting an oxygen reduction reaction. It has a supported air electrode 32 and a solid polymer electrolyte membrane 33 sandwiched between the fuel electrode 31 and the air electrode 32.

  The fuel cartridge 30 stores methanol diluted with water. The methanol in the fuel cartridge 30 is supplied directly to the fuel electrode 31. The air electrode 32 is in contact with air.

In the fuel electrode 31, methanol reacts with water to become carbon dioxide, hydrogen ions, and electrons (CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ ). Hydrogen ions reach the air electrode 32 through the solid polymer electrolyte membrane 33, and electrons reach the air electrode 32 through an external circuit (such as a load). At the air electrode 32, hydrogen ions and oxygen in the air meet and take water from the electrode surface to become water (3/2 · O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O). Carbon dioxide generated at the fuel electrode 31 and water generated at the air electrode 32 are discharged to the outside through a discharge hole (not shown). The voltage between the two electrodes, with the fuel electrode 31 as the negative electrode and the air electrode 32 as the positive electrode, is output to the external circuit (such as a load) as the output voltage V _FC of the fuel cell 1.

  The fuel cartridge 30 is detachable from the fuel cell 1, and methanol (diluted methanol) is supplied to the fuel electrode 31 when the fuel cartridge 30 is mounted. The concentration of methanol in the unused fuel cartridge 30 (that is, the initial concentration) is, for example, 60% by weight. Further, a state in which an unused fuel cartridge 30 is mounted and power generation is not performed is referred to as an initial state.

  In order to obtain a desired concentration of methanol (fuel concentration) supplied to the fuel electrode 31, a method of mixing methanol and water using a circulation pump or the like has also been proposed. A so-called passive system that does not use a circulation pump or the like for control is adopted. In addition, air (oxygen) is supplied to the air electrode 32 by natural convection, but a method of supplying air (oxygen) to the air electrode 32 using a pump or the like may be employed.

  When configured as described above, the fuel concentration in the fuel electrode 31 of the fuel cell 1 is reduced from the initial concentration by power generation. When the fuel concentration changes, the power generation characteristics (output characteristics) of the fuel cell 1 also change.

Curves 61, 62 and 63 in FIG. 2 show the relationship between the output current I _FC (horizontal axis) and the output voltage V _FC (vertical axis) of the fuel cell 1 when the fuel concentrations are D1, D2 and D3, respectively. Represents. Here, it is assumed that the inequality: “D1>D2> D3” holds. As can be seen from FIG. 2, the current that can be output by the fuel cell 1 decreases as the fuel concentration decreases. Further, at the same fuel concentration, if the output current I _FC increases, the output voltage V _FC decreases.

Curves 71, 72 and 73 in FIG. 2 indicate the output current I _FC (horizontal axis) and generated power (output power) P _FC (vertical axis) of the fuel cell 1 when the fuel concentrations are D1, D2 and D3, respectively. Represents the relationship. When the output current I _FC increases from zero at the same fuel concentration, the generated power P _FC also increases. When the output current I _FC becomes a certain current corresponding to each fuel concentration, the generated power P _FC becomes maximum, and when the output current I _FC further increases, the generated power P _FC also increases with a sudden decrease in the output voltage V _FC. It decreases rapidly.

In the case where the fuel concentration is D1, the maximum value of the generated power P _FC (maximum power) and P1, the output current I _FC and output voltage V _FC gives the maximum value P1 in the generated power P _FC, respectively and I1 and V1 . In the case where the fuel concentration is D2, the maximum value of the generated power P _FC (maximum power) and P2, the output current I _FC and output voltage V _FC gives the maximum value P2 in generated power P _FC, respectively and I2 and V2 . In the case where the fuel concentration is D3, the maximum value of the generated power P _FC (maximum power) and P3, the output current I _FC and output voltage V _FC gives the maximum value P3 in the generated power P _FC, respectively and I3 and V3 . Once the fuel concentration, the maximum value of the generated power P _FC, and the output current I _FC and output voltage V _FC gives the maximum value in the generated power P _FC is determined.

  When the inequality: “D1> D2> D3” is satisfied as described above, the three inequalities: “I1> I2> I3”, “V1 <V2 <V3”, “P1> P2> P3” are obtained from the characteristics of the fuel cell 1. "Is established.

Generally, when a current larger than the output current I _FC (for example, I1 at the fuel concentration D1) that gives the maximum value to the generated power P _FC is drawn from the fuel cell 1, the fuel cell 1 is deteriorated or damaged. Therefore, in order to use the fuel cell 1 safely, it is necessary to prevent the output voltage V _FC from falling below V1 at the fuel concentration D1, for example (it is necessary to operate in a safe operation region that satisfies such conditions). is there).

  By the way, since the reaction formula of the chemical reaction in the fuel electrode 31 and the air electrode 32 is known, it is possible to calculate how much methanol is consumed when a certain amount of electric power is generated. If the methanol content (or methanol weight) contained in the unused fuel cartridge 30 and the initial concentration are known, the fuel concentration at that time is estimated based on the total amount of generated power from the initial state. It is possible.

  Therefore, in the present embodiment, the fuel concentration is estimated based on the total power generation amount from the initial state with reference to the content and the initial concentration. This estimation is performed by, for example, a lower limit voltage setting unit 22 and / or a set voltage control unit 23 described later. Here, the total amount of generated power from the initial state is an integrated value of the generated power of the fuel cell 1 when the initial state is zero. Hereinafter, the total amount of generated power from the initial state is (in principle) simply referred to as the total amount of generated power Pt. In the experiment at the design stage, the fuel concentration in the relationship with the total power generation amount Pt is measured using a concentration sensor, and the relationship between the total power generation amount Pt and the fuel concentration is estimated based on the measurement result. Also good.

  The relationship between the total power generation amount Pt (horizontal axis) and the fuel concentration (vertical axis) is shown by a solid line 65 in FIG. As a matter of course, the fuel concentration decreases as the total power generation amount Pt increases. The fuel concentration at Pt = 0 coincides with the initial concentration.

Assume that the fuel concentrations estimated when the total power generation amount Pt is Pt1, Pt2, and Pt3 are D1, D2, and D3, respectively. If this estimation is ideally performed without error, when the total generated power amount Pt is Pt1, Pt2, and Pt3, the output voltages V _FC that give the maximum value to the generated power P _FC are V1, V2, and V3, respectively. It becomes.

The output voltage V _FC giving the maximum value to the generated power P _FC can be expressed as a function of the total generated power amount Pt (hereinafter referred to as “maximum power function”). The solid line 66 in FIG. 3 is a graph of this maximum power function, that is, a graph showing the relationship between the total generated power amount Pt (horizontal axis) and the output voltage V _FC (vertical axis) that gives the maximum value to the generated power P _FC. is there. (Pt1, V1), (Pt2, V2) and (Pt3, V3) are on the solid line 66. The solid line 67 will be described later.

In the present embodiment, control is performed so that the output voltage V _FC of the fuel cell 1 does not fall below the voltage specified by the maximum power function at an arbitrary total generated power amount Pt. FIG. 4 is an overall electrical configuration diagram of the fuel cell power supply system according to the first embodiment.

The positive electrode (air electrode 32) of the fuel cell 1 is connected to the positive electrode of the electrolytic capacitor 2, and the negative electrode (fuel electrode 31) of the fuel cell 1 is connected to the negative electrode of the electrolytic capacitor 2. The negative electrode of the fuel cell 1 is connected to a ground line having a reference potential, for example. A voltage detector 4 for detecting the output voltage V _FC of the fuel cell 1 is provided between both electrodes of the fuel cell 1. The positive electrode of the fuel cell 1 is connected to the non-inverting input terminal (+) of the error amplifier 5 and one end of the coil 6 via a current detector 3 (for example, a shunt resistor) for detecting the output current I _FC of the fuel cell 1. It is connected.

  The other end of the coil 6 is commonly connected to the drain of an N-channel field effect transistor 7 (hereinafter referred to as FET 7), the cathode of a diode 8, and the anode of a diode 9. The cathode of the diode 9 is commonly connected to the positive electrode of the electrolytic capacitor 10 and one end of the switch 11. The other end of the switch 11 is connected to the ground line via the load 12, and the source of the FET 7, the anode of the diode 8, and the negative electrode of the electrolytic capacitor 10 are also connected to the ground line.

  The set voltage Vref from the set voltage control unit 23 is applied to the inverting input terminal (−) of the error amplifier 5. The non-inverting input terminal (+) and the inverting input terminal (−) of the PWM comparator 13 are respectively supplied with the output voltage of the error amplifier 5 and the triangular wave voltage output from the triangular wave generating circuit 14. 13 supplies a pulse-width modulated signal to the gate of the FET 7.

The error amplifier 5 compares the output voltage V _FC of the fuel cell 1 with the set voltage Vref, and in a steady state, the FET 7 is on / off controlled so that these two voltages are equal. The coil 6, FET 7, and diodes 8 and 9 constitute a boost converter (voltage converter) that boosts and outputs the output voltage V _FC of the fuel cell 1.

The total generated power detection unit 21 sequentially receives the detection result of the output current I _FC by the current detector 3 and the detection result of the output voltage V _FC by the voltage detector 4, and the product of the output current I _FC and the output voltage V _FC. The total generated power amount Pt is sequentially calculated from the integrated value. The total generated power amount detection unit 21 updates the total generated power amount Pt output one after another at a predetermined interval.

The lower limit voltage setting unit 22 sets and outputs a lower limit voltage V _LL that is a lower limit of the output voltage V _FC based on the total generated power amount Pt calculated by the total generated power amount detection unit 21. At this time, the fuel concentration may be estimated based on the total power generation amount Pt, and the lower limit voltage V _LL may be set based on the estimated fuel concentration. The lower limit voltage V _LL is sequentially updated along with the update of the total power generation amount Pt.

The lower limit voltage V _LL is determined, for example, according to the above maximum power function (first function). That is, the lower limit voltage V _{LL at} a certain timing is equal to the output voltage V _FC that gives the maximum value to the generated power P _FC at the total generated power amount Pt at that timing. For example, if the value of a given total power generation amount Pt is Pt1, Pt2, and Pt3, V _LL is respectively V1, V2 and V3. Further, as is clear from the above description, the lower limit voltage V _LL increases as the total generated power amount Pt increases. Thereby, the fuel cell 1 can be reliably operated in the safe operation region.

The set voltage control unit 23 sets the set voltage Vref to be followed by the output voltage V _FC based on the total generated power amount Pt calculated by the total generated power amount detecting unit 21, and sets the set voltage Vref to the error amplifier 5. Output. At this time, the fuel concentration may be estimated based on the total generated power amount Pt, and the set voltage Vref may be set based on the estimated fuel concentration. The set voltage Vref is updated sequentially along with the update of the total generated power amount Pt.

The set voltage Vref is determined according to a set voltage function (operating voltage function; second function) represented by a solid line 67 in FIG. The solid line 67 is a graph showing the relationship between the set voltage Vref total power generation amount Pt and the output voltage V _FC to be followed (operating voltage). Setting voltage Vref than the (output voltage V _FC giving the maximum value to the generated power P _FC) lower limit voltage V _LL at any same total power generation amount Pt, for example, always .DELTA.Va as high (although, .DELTA.Va> 0) . When the given value of total generated power Pt is Pt1, Pt2, and Pt3, Vref is, for example, (V1 + ΔVa), (V2 + ΔVa), and (V3 + ΔVa), respectively. Of course, Vref may be (V1 + ΔVa1), (V2 + ΔVa2), and (V3 + ΔVa3) when the value of the given total generated power amount Pt is Pt1, Pt2, and Pt3, respectively (ΔVa1, ΔVa2, and ΔVa3 are different from each other) Are all greater than zero).

The reason why the set voltage Vref is set higher than the lower limit voltage V _{LL in} this way is to ensure safer operation of the fuel cell 1. Items to be considered in determining ΔVa, ΔVa1, ΔVa2, and ΔVa3 will be described with reference to FIG. FIG. 5 is a graph showing the lower limit voltage V _LL , the set voltage Vref and the total generated power amount Pt on the horizontal axis when it is assumed that the fuel cell 1 continues to generate power of a certain constant power. is there.

A solid line 66a represents a graph of the maximum power function corresponding to the solid line 66 in FIG. 3 with the horizontal axis changed to time. A solid line 67a represents a graph of a set voltage function corresponding to the solid line 67 in FIG. 3 with the horizontal axis changed to time. A solid line 68 represents the total power generation amount Pt with time as the horizontal axis. A stepped broken line 69 represents the actual output voltage V _FC . The set voltage Vref is updated at timings T1, T2, and T3.

Originally, it is desirable that the output voltage V _FC always be on the solid line 67a. However, for example, immediately before the timing T2, the actual output voltage V _FC is lower than the voltage on the solid line 67a. That is, the actual output voltage V _FC approaches the solid line 66a indicating the limit of the safe operation area. This is because the set voltage Vref applied to the error amplifier 5 is maintained at the timing T1 immediately before the timing T2, even though the total generated power amount Pt is increased between the timings T1 and T2. Due to being. The above ΔVa, ΔVa1, ΔVa2, and ΔVa3 should be determined in consideration of the amount of deviation between the actual output voltage V _FC and the voltage on the solid line 67a that occurs during the update timing of the set voltage Vref. is there.

However, ΔVa = 0 (or ΔVa1 = ΔVa2 = ΔVa3 = 0) can be set when the interval of the update timing of the set voltage Vref reflecting the increase in the total power generation amount Pt is sufficiently short. In this case, the set voltage Vref and the lower limit voltage V _LL coincide. However, ΔVa> 0 is desirable from the viewpoint of ensuring higher safety.

The set voltage Vref whose voltage value is determined by the set voltage controller 23 is applied to the error amplifier 5 as described above. The PWM comparator 13 controls the ON / OFF duty ratio of the FET 7 based on the comparison result in the error amplifier 5, thereby controlling the output current I _FC and thereby controlling the output voltage V _FC (because (If the output current I _FC is determined, the output voltage V _FC is also determined).

In a steady state, the output voltage V _FC and the set voltage Vref basically coincide with each other. However, in the configuration of FIG. 4, when the load 12 is too light, the output voltage V _FC and the set voltage Vref do not match. If the load 12 is too light, the output voltage V _FC can be higher than the set voltage Vref because the load 12 draws only a small amount of current. In order to suppress the difference between the output voltage V _FC and the set voltage Vref, ΔVa, ΔVa1, ΔVa2, and ΔVa3 may be appropriately determined in consideration of the power consumption of the load 12.

By setting the set voltage Vref as described above, the output voltage V _FC becomes higher than V1 at the concentration D1, as shown by the operating point 75 in FIG. 6, and accordingly, the output current I _FC becomes higher than I1. generated power P _FC is less than the maximum value P1 with small. The same applies to the operating points 76 and 77 corresponding to the densities D2 and D3. In FIG. 6, the same parts as those in FIG. 2 are denoted by the same reference numerals.

The state monitoring unit 24 compares the lower limit voltage V _LL output from the lower limit voltage setting unit 22 with the output voltage V _FC detected by the voltage detector 4. When the output voltage V _FC falls below the lower limit voltage V _LL due to the occurrence of an abnormality such as a short circuit of the load 12 in spite of the output of the set voltage Vref by the set voltage control unit 23 (or the output voltage V _FC is lower limit voltage) When the voltage becomes V _LL or lower), the state monitoring unit 24 disconnects the load 12 and the fuel cell 1 by turning off the switch 11 (specifically, disconnects the connection between the cathode of the diode 9 and the load 12). ). Thereby, the fuel cell 1 is protected.

When the output voltage V _FC falls below the lower limit voltage V _LL (or when the output voltage V _FC becomes lower than the lower limit voltage V _LL ), the FET 7 is forcibly turned off instead of turning off the switch 11. You may make it maintain. In this case, the switch 11 can be omitted. Since the voltage converter composed of the coil 6, the FET 7, and the diodes 8 and 9 is a step-up converter, if the FET 7 is forcibly turned off, the power generation by the fuel cell 1 is stopped (however, the load 12 (Assuming the operating voltage is high enough).

  The state monitoring unit 24 also monitors the upper limit of the total generated power amount Pt. FIG. 7 shows an operation flow of the entire fuel cell power supply system including this monitoring. First, when the fuel cartridge 30 is mounted on the fuel cell 1, the fuel cell 1 is filled with fuel and is in an initial state. In the initial state, the total generated power amount Pt is reset (step S1). That is, it is set to zero. Next, in response to the total generated power amount Pt becoming zero, the set voltage Vref is set to an initial value according to the above set voltage function (step S2).

When power generation is started, the total generated power amount Pt is calculated as described above (step S3), and the set voltage Vref and the lower limit voltage V _LL corresponding to the calculated total generated power amount Pt are set (step S4). ). In step S5, it is determined whether the output voltage V _FC is equal to or higher than the lower limit voltage V _LL (or it is determined whether V _FC > V _LL is satisfied). Usually, the output voltage V _FC is equal to or higher than the lower limit voltage V _LL (or V _FC > V _LL ). In this case (Y in step S5), the process proceeds to step S6.

In step S6, the state monitoring unit 24 determines whether the total generated power amount Pt is equal to or greater than the set power amount _PTH . The set power amount P _TH corresponds to the total power generation amount Pt estimated that the fuel concentration has decreased to a predetermined concentration that requires replacement of the fuel cartridge 30, and the value is determined at the design stage of the fuel cell power system. In advance. If the total generated power amount Pt has not reached the set power amount P _TH (N in Step S6), the process returns to Step S3, and the operations after Step S3 are repeated. When the total generated power amount Pt reaches the set power amount P _TH (Y in step S6), the process proceeds to step S7, and the state monitoring unit 24 outputs a control signal for prompting replacement of the fuel cartridge 30.

  The control signal is transmitted, for example, to a CPU (Central Processing Unit) (not shown) in a device on which the fuel cell power supply system is mounted. When the CPU receives the control signal, it notifies the remaining amount of fuel using a notifying unit (not shown) provided in the device. As the notification unit, various parts provided in the device such as a display panel, an LED (Light Emitting Diode), a speaker, and a buzzer can be applied. “Informing about the remaining amount of fuel” means that the user is prompted to replace the fuel cartridge 30 or that the user is informed that the remaining amount of the fuel cartridge 30 is low. It is.

  When the fuel cartridge 30 is replaced in accordance with the above notification, the fuel cell 1 is filled or supplemented with fuel, and the process returns to step S1 and the above-described operation is repeated. The state that has reached step S1 for the first time and the state that has reached step S1 after the second time can be collectively referred to as a reference state immediately after the fuel cell 1 is filled or replenished with fuel.

If it is determined in step S5 that the output voltage V _FC is lower than the lower limit voltage V _LL (or if V _FC ≦ V _LL is established), the process proceeds to step S9 (N in step S5). In step S9, the switch 11 is turned off by the state monitoring unit 24, and the load 12 and the fuel cell 1 are disconnected. Alternatively, the boost converter is controlled so that power generation by the fuel cell 1 is stopped.

Note that the processing in step S6 may be changed to the following processing. In step S6, the state monitoring unit 24 determines whether the output voltage V _FC is equal to or higher than the upper limit voltage V _UL (or whether V _FC > V _UL is established). When V _FC ≧ V _UL (or V _FC > V _UL ) is satisfied, the process proceeds to step S7. When V _FC ≧ V _UL (or V _FC > V _UL ) is not satisfied, the process returns to step S3. To do. The upper limit voltage _VUL is a voltage set in advance in the design stage of the fuel cell power supply system. Since the above set voltage function is determined so that the output voltage V _FC reaches the upper limit voltage V _UL when the total generated power amount Pt reaches the set power amount P _TH , the establishment of the inequality: V _FC ≧ V _UL , The establishment of the inequality: Pt ≧ P _TH is equivalent.

Further, the example in which the lower limit voltage V _LL is matched with the voltage determined according to the maximum power function (first function), that is, the output voltage V _FC giving the maximum value to the generated power P _FC has been described above. A voltage obtained by adding a slight margin to a voltage determined according to the maximum power function (first function) may be used as the lower limit voltage V _LL . For example, if the value of the total power generation amount Pt is Pt1, Pt2, and Pt3, the V _LL, respectively (V1 + .DELTA.Vb), may be used as (V2 + .DELTA.Vb) and (V3 + ΔVb) (where, .DELTA.Vb> 0). That is, the lower limit voltage V _LL is a voltage that does not fall below the output voltage V _FC when the fuel cell 1 outputs the maximum power.

  Moreover, you may make it further provide the temperature detection part (not shown) which detects the temperature of the fuel cell 1, or the surrounding temperature of the fuel cell 1. FIG. Specifically, for example, a thermistor is disposed on the surface of the housing (not shown) of the fuel cell 1 while being thermally coupled to the housing of the fuel cell 1, and the temperature of the fuel cell 1 is detected by detecting the resistance value of the thermistor. (Strictly speaking, the temperature of the surface of the casing or the temperature of the fuel cell 1 estimated from the temperature) is detected. At this time, in order to detect the temperature of the fuel electrode 31 of the fuel cell 1, the thermistor may be brought into contact with a portion of the housing close to the fuel electrode 31. Further, for example, a thermistor is disposed in the vicinity of the surface of the casing of the fuel cell 1, and the ambient temperature of the fuel cell 1 is detected by detecting the resistance value of the thermistor.

  As will be described later, when a fuel cell of an assembled battery in which single cells of a fuel cell such as the fuel cell 1 are connected in series (as the fuel cell 1) is adopted, one or a plurality of single cells are detected by the temperature detection unit. The cell temperature or the ambient temperature may be detected. When detecting each temperature (or each ambient temperature) of multiple single cells, for example, the average, maximum or minimum temperature of each detected temperature (or each ambient temperature) is adopted as the fuel cell temperature (or ambient temperature) You can also When stacking unit cells to form a battery pack having a stack structure, for example, a thermistor is disposed on the surface of a separator that separates the unit cells.

  Further, when adopting a planar arrangement structure in which the unit cells constituting the assembled battery are arranged on the same plane, the same as when the fuel cell is configured by one unit cell (that is, the fuel cell 1 of FIG. 1). As in the case), the thermistor may be brought into contact with a portion of the casing close to the fuel electrode in order to detect the temperature of the fuel electrode of each single cell or the ambient temperature. Further, when detecting the ambient temperature of the assembled battery, a thermistor may be disposed in the vicinity of the surface of the assembled battery housing (including the separator), and the resistance value of the thermistor may be detected.

Then, the lower limit voltage setting unit 22 corresponds to the temperature (the temperature of the fuel cell 1 or the ambient temperature of the fuel cell 1) detected by the temperature detection unit with respect to the lower limit voltage V _LL set based on the total generated power amount Pt. Correction is made so that the corrected lower limit voltage V _LL is output. The state monitoring unit 24 compares the corrected lower limit voltage V _LL with the output voltage V _FC .

The output characteristics of the fuel cell 1 change under the influence of self-heating caused by a chemical reaction or ambient temperature. When the output characteristic changes, the safe operation region also changes. Therefore, in order to use the fuel cell 1 more safely, it is desirable to correct the lower limit voltage V _{LL according} to the detected temperature.

For example, when the detected temperature is higher than a predetermined reference temperature at any given total generated power amount Pt, the lower limit voltage V _LL is set lower than that at the reference temperature. This corresponds to correcting the solid line 66 that is a graph of the maximum power function as shown by the solid line 66b in FIG. On the other hand, when the detected temperature is lower than a predetermined reference temperature at any given total generated power amount Pt, the lower limit voltage V _LL is set higher than that at the reference temperature. This corresponds to correcting the solid line 66 that is a graph of the maximum power function as indicated by a solid line 66c in FIG.

It should be noted that how to correct the lower limit voltage V _LL according to the detected temperature may be determined in advance according to the characteristics of the fuel cell 1 using experiments or the like.

Further, from the same point of view that the lower limit voltage _VLL is corrected according to the temperature of the fuel cell 1 and the like, the set voltage Vref is also corrected according to the detected temperature in order to use the fuel cell 1 more safely. Anyway. That is, the set voltage Vref set based on the total amount of generated power Pt is corrected according to the temperature (the temperature of the fuel cell 1 or the ambient temperature of the fuel cell 1) detected by the temperature detector, and the setting after the correction is made. The set voltage control unit 23 outputs the voltage Vref. Error amplifier 5 will be compared set voltage Vref and the corrected output voltage V _FC.

  For example, when the detected temperature is higher than a predetermined reference temperature at any given total generated electric energy Pt, the set voltage Vref is set lower than that at the reference temperature. This corresponds to correcting the solid line 67, which is a graph of the set voltage function, as shown by the solid line 67b in FIG. On the other hand, when the detected temperature is lower than a predetermined reference temperature at any given total generated power amount Pt, the set voltage Vref is set higher than that at the reference temperature. This corresponds to correcting the solid line 67, which is a graph of the set voltage function, as indicated by the solid line 67c in FIG.

  Note that how to correct the set voltage Vref according to the detected temperature may be determined in advance according to the characteristics of the fuel cell 1 using experiments or the like.

<< Second Embodiment >>
Next, a fuel cell power supply system according to a second embodiment of the present invention will be described. FIG. 10 is an overall electrical configuration diagram of the fuel cell power supply system according to the second embodiment. The fuel cell power supply system according to the second embodiment is different from the fuel cell power supply system according to the first embodiment in that a secondary battery 15 connected in parallel with the load 12 is newly provided. In this respect, the fuel cell power supply systems in the first and second embodiments are the same. 10, parts that are the same as those in FIG. 4 are given the same reference numerals, and duplicate descriptions of the same parts are omitted.

  The secondary battery 15 is specifically a lithium ion secondary battery, for example. However, it goes without saying that any other secondary battery may be adopted as the secondary battery 15. A positive voltage output terminal (positive electrode) of the secondary battery 15 is connected to a connection point between the switch 11 and the load 12, and a negative voltage output terminal (negative electrode) of the secondary battery 15 is connected to the ground line.

  The operation of the fuel cell power supply system according to the second embodiment is the same as the operation in the first embodiment. However, charging / discharging of the secondary battery 15 is performed by connecting the secondary battery 15 to the load 12 in parallel.

  FIG. 11 illustrates a relationship between the power generation of the fuel cell 1 and the charge / discharge of the secondary battery 15 when the power consumption of the load 12 changes with time. Consider a case where the power consumption of the load 12 increases monotonously from zero with a certain point in time as indicated by a broken line 78. For simplification of description, power loss in the boost converter or the like is ignored.

  The power generated by the fuel cell 1 is maintained at the power corresponding to the set voltage Vref regardless of the power consumption of the load 12. For this reason, in the period when the generated power of the fuel cell 1 exceeds the power consumption of the load 12, the secondary battery uses surplus power (corresponding to the hatched portion 79 in FIG. 11) corresponding to the power obtained by subtracting the power consumption from the generated power. 15 is charged. On the other hand, during the period when the generated power of the fuel cell 1 is lower than the power consumption of the load 12, the insufficient power (corresponding to the hatched portion 80 in FIG. 11) corresponding to the power obtained by subtracting the generated power from the power consumption is the secondary battery. It is covered by 15 discharges. Thus, by connecting the secondary battery 15 to the load 12 in parallel, it is possible to effectively use the electric power according to the light weight of the load 12.

Of course, the temperature detection unit described in the first embodiment may be provided in the fuel cell power supply system in the second embodiment. In this case, also in the second embodiment, the lower limit voltage _VLL and the set voltage Vref are corrected according to the temperature of the fuel cell 1 or the ambient temperature of the fuel cell 1.

  When the secondary battery 15 such as a lithium ion secondary battery is provided, a thermistor for charge control protection for detecting the temperature of the secondary battery 15 is usually provided together with the secondary battery 15. This thermistor for charge control protection is provided on the surface of the secondary battery 15 or in the vicinity of the surface in order to monitor the abnormal heat generation of the secondary battery 15 during charging. When the secondary battery 15 and the fuel cell 1 are arranged close to each other, the charge control protection thermistor may be used as a temperature detection unit that detects the temperature of the fuel cell 1 or the ambient temperature of the fuel cell 1. Thereby, the number of parts can be reduced. For example, when the secondary battery 15 and the fuel cell 1 are arranged in the same housing to constitute one fuel cell unit, the temperature of the secondary battery 15 and the temperature of the fuel cell 1 or the fuel cell are constituted by one thermistor. 1 ambient temperature can be detected.

<< Third Embodiment >>
Next, a fuel cell power supply system according to a third embodiment of the present invention will be described. FIG. 12 is an overall electrical configuration diagram of the fuel cell power supply system according to the third embodiment. The fuel cell power supply system according to the third embodiment includes a current detector 3, a voltage detector 4, a total generated power amount detection unit 21, a lower limit voltage detection unit 22, and a set voltage control unit in the fuel cell power supply system of the first embodiment. 23 and the state monitoring unit 24 are replaced with a timer 26 and a main control unit 27. The fuel cell power supply system in the first and third embodiments is the same except for the part related to the replacement. In FIG. 12, the same parts as those in FIG. 4 are denoted by the same reference numerals, and the description of the same parts is omitted. In addition, with the deletion of the current detector 3, the positive electrode (air electrode 32) of the fuel cell 1 is directly connected to one end of the coil 6.

  When the fuel cartridge 30 is attached to the fuel cell 1, the fuel cell 30 is filled or replenished with fuel, or immediately after the fuel cell 1 is filled or replenished, the time when power generation by the fuel cell 1 is actually started is the reference time. And The timer 26 outputs a pulse to the main control unit 27 every time a certain time elapses. The main controller 27 recognizes the elapsed time from the reference time by counting the number of pulses from the timer 26, and changes the set voltage Vref to be output according to the elapsed time. Specifically, for example, the set voltage Vref output every time a pulse is given from the timer 26 is increased by a predetermined voltage.

  If there is no interruption in power generation after the start of power generation, the elapsed time and the power generation time (the time during which power generation is actually performed) match. If power generation is interrupted, the set voltage Vref may be changed according to the time obtained by subtracting the interruption time from the elapsed time (that is, the power generation time).

If the power consumption of the load 12 is constant, the total power generation amount can be estimated from the elapsed time or the power generation time without using a voltage detector or the like. The main control unit 27 regards the “estimated total generated power amount” as the “detected total generated power amount Pt” in the first and second embodiments, and sets the set voltage Vref according to the set voltage function. As a result, the set voltage Vref increases as the elapsed time or power generation time increases. The output voltage V _FC of the fuel cell 1 follows (in principle) the set voltage Vref. When the total amount of generated power is estimated ideally, the graph showing the relationship between the estimated total amount of generated power and the output voltage V _FC of the fuel cell 1 matches the solid line 67 in FIG.

  As described above, by increasing the set voltage Vref according to an increase in elapsed time or power generation time, the fuel cell 1 can be always operated in the safe operation region. Further, since the current detector 3 and the voltage detector 4 are not necessary, the configuration is simplified. The third embodiment is particularly suitable for a fuel cell power supply system in which the power consumption of the load 12 is relatively stable. Examples of such a load 12 include lighting devices such as emergency lights and outdoor lights.

  When the elapsed time or the power generation time reaches a predetermined first set time, the main control unit 27 disconnects the load 12 and the fuel cell 1 by turning off the switch 11. Alternatively, the power generation by the fuel cell 1 is stopped by forcibly turning off the FET 7.

  Further, when the elapsed time or the power generation time reaches a predetermined second set time, the main control unit 27 outputs a control signal for prompting replacement of the fuel cartridge 30. This control signal is the same as the control signal output by the state monitoring unit 24 in FIG. 4 or FIG. 10, and the notification regarding the remaining amount of fuel is the same as in the first embodiment by the output of the control signal from the main control unit 27. Is done. The second set time is set to be equal to or shorter than the first set time.

  Similarly to the modification of the first embodiment to the second embodiment, the secondary battery 15 may be provided in parallel with the load 12 in the third embodiment.

  In addition, the temperature detection unit described in the first embodiment may be provided in the third embodiment. The set voltage Vref may be changed according to not only the elapsed time or the power generation time but also the detected temperature of the fuel cell 1 or the ambient temperature.

  For example, when the detected temperature is a predetermined reference temperature and the elapsed time or power generation time increases by ΔT (where ΔT> 0), the set voltage Vref is increased by ΔVref1 (where ΔVref1> 0). Think about the case. In this case, if the detected temperature is higher than the reference temperature, the set voltage Vref is increased by ΔVref2 (where ΔVref2> 0) when the elapsed time or power generation time increases by ΔT. Here, ΔVref1> ΔVref2 is established. How to set the difference between ΔVref1 and ΔVref2 may be determined in advance according to the characteristics of the fuel cell 1 using experiments or the like.

<< Deformation, etc. >>
The above-described embodiments can be arbitrarily combined as long as there is no contradiction. In each of the above-described embodiments, the configuration in which the fuel cartridge 30 is detachable from the fuel cell 1 and the fuel cartridge 30 is replaced when the fuel concentration decreases is illustrated. However, the relationship between the fuel cartridge and the fuel cell (fuel cell body) can be variously modified.

  For example, the fuel cartridge and the fuel cell (fuel cell main body) may be integrated into one fuel cell unit, and the entire fuel cell unit may be replaced when the fuel concentration decreases.

  Further, for example, as shown in FIG. 13, methanol (diluted methanol) as fuel may be temporarily supplied from the fuel cartridge 36 to the buffer tank 35. In FIG. 13, the same parts as those in FIG. The fuel transferred from the fuel cartridge 36 to the buffer tank 35 reacts in the fuel electrode 31 to generate power. In this case, the fuel cartridge 36 is detachable from the fuel cell (fuel cell main body) composed of the fuel electrode 31, the air electrode 32, the solid polymer electrolyte membrane 33 and the buffer tank 35, and the fuel to be supplied to the buffer tank 35. It is sufficient to replace only the fuel cartridge 36 when there is no more in the fuel cartridge 36. When the configuration in which the buffer tank 35 is provided is adopted, the process of step S7 in FIG. 7 is referred to as “supply of fuel from the fuel cartridge 36 to the buffer tank 35” (provided that the fuel cartridge 36 has sufficient fuel). .

  However, when the fuel cell shown in FIG. 13 is adopted, the fuel concentration in the fuel electrode 31 immediately after reaching step S1 through the process of step S7 may be different from that immediately after reaching step S1 last time. That is, every time step S1 is reached, the fuel concentration immediately after that can be different (for example, it decreases every time step S1 is reached). This is because the amount of water present in the buffer tank 35 increases every time step S7 is caused by the generation of water by the reaction.

Considering this, the number of times that the process has reached step S7 may be counted, and the lower limit voltage _VLL and the set voltage Vref may be corrected according to the number of times. Specifically, the lower limit voltage _VLL and the set voltage Vref are increased as the number of times reaching step S7 increases. Further, during the period from step S7 to step S1, a process of “excluding water in the buffer tank 35” may be inserted. Then, it is possible to omit the correction of the lower limit voltage V _LL and the set voltage Vref according to the above number of times.

  In the case where the water in the buffer tank 35 is removed when the fuel cartridge 36 is replaced, the counted number may be reset (set to zero) when the fuel cartridge 36 is replaced.

Further, for the sake of simplicity of illustration and description, the case where a single cell of a fuel cell as shown in FIG. 1 is adopted as the fuel cell 1 is shown. However, in each of the above embodiments, such a single cell is usually used. Are used instead of the fuel cell 1. When the assembled battery fuel cell is employed, the positive electrode (air electrode 32) of the single cell on the highest voltage side is connected to the positive electrode of the electrolytic capacitor 2 and the negative electrode (fuel electrode 31) of the single cell on the lowest voltage side is connected. The voltage between the negative electrode of the single cell on the lowest voltage side and the positive electrode of the single cell on the highest voltage side is the output voltage V _FC .

  As described above, in each embodiment, the coil 6, the FET 7, and the diodes 8 and 9 constitute a boost converter (voltage converter). In the first and second embodiments, the set voltage control unit 23, the state monitoring unit 24, the error amplifier 5, the PWM comparator 13, and the triangular wave generation circuit 14 constitute a control unit that controls the boost converter (voltage converter). . In the first and second embodiments, the fuel cell control device that performs output control of the fuel cell 1 includes, for example, the control unit, the total generated power amount detection unit 21, the lower limit voltage setting unit 22, and the boost converter (voltage Converter). In the first and second embodiments, the state monitoring unit 24 functions as a control signal output unit that outputs a control signal for performing notification regarding the remaining amount of fuel.

  In the third embodiment, the timer 26, the main control unit 27, the error amplifier 5, the PWM comparator 13, and the triangular wave generation circuit 14 constitute a control unit that controls the boost converter (voltage converter). Moreover, in 3rd Embodiment, the fuel cell control apparatus which performs output control of the fuel cell 1 contains said control part and a boost converter (voltage converter), for example. Moreover, in 3rd Embodiment, the main control part 27 functions as a control signal output part which outputs the control signal for alerting | reporting regarding the residual amount of fuel.

  Each of the above embodiments is based on the premise that a so-called passive system that does not use a circulation pump or the like for controlling the concentration of methanol is used, but the present invention is a power supply system using a circulation pump or the like. It is applicable to. In this type of system, there is one that attempts to keep the fuel concentration of the fuel electrode of the fuel cell substantially constant while circulating the fuel in a buffer tank (not shown) (this system is hereinafter referred to as “system A”). "). However, since fuel is consumed by power generation in the same manner as in the passive system, the fuel concentration in the fuel electrode of the fuel cell gradually decreases by power generation unless new fuel is added to the buffer tank.

  In the system A, for example, a fuel sensor (not shown) for detecting the fuel concentration is provided, and when the fuel concentration falls below a predetermined threshold, fuel is supplied from the main tank (not shown) to the buffer tank. Add. When the time point at which fuel is supplied from the main tank to the buffer tank is referred to as “fuel supply time point”, when the method A is adopted, the fuel of the fuel cell in a period from a certain fuel supply time point to the next fuel supply time point is used. The fuel concentration at the pole will be reduced by power generation.

  For this reason, even when the method A is adopted, the total generated power amount of the fuel cell from the fuel supply time point is detected as in the first and second embodiments, and the lower limit voltage or the like is set according to the detected total generated power amount. If set, the fuel cell can be operated safely. When the method A is adopted in the first and second embodiments, the above-mentioned “total generated power amount Pt” may be read as the total generated power amount of the fuel cell from the fuel supply time point.

  For the same reason, it is possible to adopt the method A in the third embodiment. In this case, the “elapsed time” may be read as the elapsed time from the fuel supply time, and the “power generation time” may be read as the power generation time from the fuel supply time. The method A can be considered as a kind of so-called active method.

  The present invention is suitable for a driving power source for portable devices such as a mobile phone, a portable personal computer, and a portable game machine, and is suitable for a driving power source for all electrical devices including the portable device.

It is a schematic diagram which shows the cell structure of the fuel cell used for each embodiment of this invention. It is a figure showing the relationship between the output current and output voltage of the fuel cell of FIG. 1, and the relationship between output current and generated electric power. FIG. 2 is a diagram illustrating a relationship between a total generated power amount of the fuel cell of FIG. 1 and an estimated fuel concentration, and a relationship between a total generated power amount, a lower limit voltage and a set voltage. 1 is an overall electrical configuration diagram of a fuel cell power supply system according to a first embodiment of the present invention. FIG. 5 is a diagram for explaining control of an output voltage of the fuel cell in FIG. 4. FIG. 5 is a diagram for explaining control of an output voltage of the fuel cell in FIG. 4. 6 is a flowchart for explaining the operation of the fuel cell power supply system of FIG. It is a figure which shows the correction method of the minimum voltage according to temperature by the minimum voltage setting part of FIG. It is a figure which shows the correction method of the setting voltage according to temperature by the setting voltage control part of FIG. It is an electrical whole block diagram of the fuel cell power supply system which concerns on 2nd Embodiment of this invention. It is a figure for demonstrating charging / discharging of a secondary battery in the relationship with the power consumption of the load of FIG. It is an electrical whole block diagram of the fuel cell power supply system which concerns on 3rd Embodiment of this invention. It is a figure which shows the modification of the fuel cell and fuel cartridge of FIG. It is a figure which shows the output characteristic of a fuel cell.

Explanation of symbols

1 Fuel Cell 3 Current Detector 4 Voltage Detector 5 Error Amplifier 6 Coil 7 FET
DESCRIPTION OF SYMBOLS 9 Diode 11 Switch 12 Load 13 PWM comparator 14 Triangle wave generation circuit 15 Secondary battery 21 Total electric power generation detection part 22 Lower limit voltage setting part 23 Setting voltage control part 24 State monitoring part 26 Timer 27 Main control part 30 Fuel cartridge 31 Fuel Electrode 32 Air electrode 33 Solid polymer electrolyte membrane 35 Buffer tank 36 Fuel cartridge

Claims (10)

A fuel concentration estimator for estimating the fuel concentration in the fuel cell in which the fuel concentration decreases from the initial state ;
A lower limit voltage setting unit for setting a lower limit voltage of the output voltage of the fuel cell based on the estimated fuel concentration;
A voltage converter provided on the output side of the fuel cell;
E Bei and a control unit for the output voltage to control the voltage converter so as not to fall below the lower limit voltage,
A total generated power detection unit that detects a total generated power that is an integrated value of the generated power of the fuel cell from an initial state in which the fuel cell is filled with fuel;
The fuel cell control device, wherein the fuel concentration is estimated based on the detected total generated power amount . A fuel concentration estimator for estimating the fuel concentration in the fuel cell in which the fuel concentration decreases from the initial state;
A lower limit voltage setting unit for setting a lower limit voltage of the output voltage of the fuel cell based on the estimated fuel concentration;
A voltage converter provided on the output side of the fuel cell;
A controller that controls the voltage converter so that the output voltage does not fall below the lower limit voltage, and
The fuel concentration is estimated according to the elapsed time from a predetermined reference time.
A fuel cell control device. A fuel concentration estimator for estimating the fuel concentration in the fuel cell in which the fuel concentration decreases from the initial state;
A lower limit voltage setting unit for setting a lower limit voltage of the output voltage of the fuel cell based on the estimated fuel concentration;
A voltage converter provided on the output side of the fuel cell;
A controller that controls the voltage converter so that the output voltage does not fall below the lower limit voltage, and
Estimating the fuel concentration according to the power generation time of the fuel cell
A fuel cell control device. 4. The fuel cell control device according to claim 1, wherein the lower limit voltage to be set is increased as the estimated fuel concentration decreases . The fuel cell according to any one of claims 1 to 4, wherein the lower limit voltage is set to a voltage that does not fall below an output voltage of the fuel cell when the maximum electric power is output to the fuel cell. Control device. The fuel cell control device according to any one of claims 1 to 5, wherein a load and a secondary battery are connected in parallel on an output side of the voltage converter . A temperature detection unit for detecting a temperature of the fuel cell or a temperature around the fuel cell;
The fuel cell control device according to any one of claims 1 to 6, wherein the lower limit voltage setting unit sets the lower limit voltage based on not only the fuel concentration but also the detected temperature. . The control unit disconnects a load and a fuel cell when the output voltage falls below the lower limit voltage despite the control of the voltage converter by the control unit. The fuel cell control device according to claim 7. Regardless of the control of the voltage converter by the control unit, when the output voltage falls below the lower limit voltage, the control unit controls the voltage converter so that power generation of the fuel cell is stopped. The fuel cell control device according to any one of claims 1 to 7, wherein: When the total generated power amount detected has reached a predetermined set amount of power, according to claim 1, wherein, further comprising a control signal output unit for outputting a control signal for performing notification relating to the remaining amount of fuel the fuel cell control system according to.

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