JP5191644B2 - Fuel cell system, voltage determination device and voltage determination method - Google Patents

Description

  The present invention relates to a fuel cell system including a fuel cell that generates electricity by supplying fuel and a charge / discharge device that performs charge / discharge according to the amount of power supplied to a load, and a voltage connected to the fuel cell system. The present invention relates to a determination device and a voltage determination method that operates in the voltage determination device.

  2. Description of the Related Art In recent years, various fuel cell systems have been developed that combine a fuel cell that generates electricity when supplied with fuel and a charging / discharging device such as a secondary battery or a capacitor that charges and discharges electric energy. For the purpose of combining the fuel cell and the charging / discharging device, even if the output of the fuel cell decreases during the transient response when power is supplied to the load, the charging / discharging device compensates for the decreased output, thereby This is because a stable output can be obtained as a system.

  In order to improve the convenience of a fuel cell system as a power source for such a fuel cell system, a charge / discharge device that can be charged and discharged can be maintained and stored in a fully charged state (full charge), and power can be always taken out. A technique for making a state (see, for example, Patent Document 1) is known. Moreover, in order to obtain a high output density and energy density as a charging / discharging apparatus, the technique (for example, refer patent document 2, patent document 3) which makes a charging / discharging apparatus a full charge state is also known.

Thus, by always charging the charging / discharging device, the maximum amount of electricity or capacitance can always be obtained from the charging / discharging device, and the convenience as a power source can be improved.
JP 2006-54976 A JP 2005-135666 A JP 2005-269825 A

However, when the charging / discharging device is connected to the fuel cell, there is an output impedance (internal impedance) in the charging / discharging device.
Therefore, the present invention has been made in view of the above points, and even when a charge / discharge device is connected to a fuel cell, the fuel cell system can efficiently supply power generated by the fuel cell to a load. An object of the present invention is to provide a voltage determination device and a voltage determination method.

  In order to solve the above problems, a first feature according to the present invention includes a fuel cell that generates power when fuel is supplied, a voltage regulator that adjusts an output voltage output from the fuel cell to a predetermined voltage, and A charging / discharging device that is connected to the voltage regulating device and performs charging / discharging according to the magnitude of power supplied from the voltage regulating device to the load, and the predetermined voltage corresponds to the voltage of the charging / discharging device. The gist of the characteristic curve is a voltage corresponding to an output impedance lower than the maximum output impedance in the characteristic curve defined by the output impedance.

  According to this feature, the voltage regulator supplies the voltage corresponding to the output impedance lower than the maximum output impedance in the charge / discharge device to the charge / discharge device. Thereby, since the voltage regulator can supply the voltage which reduces the output impedance of the charging / discharging device to the charging / discharging device, it becomes difficult for the power to be consumed unnecessarily by the output impedance of the charging / discharging device, and the fuel cell The generated power can be efficiently supplied to the load.

  The second feature of the present application is summarized in that the predetermined voltage is a voltage corresponding to an impedance lower than an intermediate value between the maximum output impedance and the minimum output impedance in the characteristic curve.

  The third feature of the present invention is summarized in that the predetermined voltage is a voltage corresponding to the minimum output impedance in the characteristic curve.

  According to a fourth aspect of the present invention, there is provided a fuel cell that generates electric power when fuel is supplied, a voltage regulator that regulates an output voltage output from the fuel cell to a predetermined voltage, and a voltage regulator that is connected to the voltage regulator. A voltage determination device connected to a fuel cell system including a charging / discharging device that performs charging / discharging according to the magnitude of electric power supplied from an adjusting device to a load, the charging / discharging device corresponding to the voltage of the charging / discharging device And a voltage determination unit that determines a voltage corresponding to an output impedance lower than the maximum output impedance in the calculated characteristic curve as a predetermined voltage. And

  A fifth feature of the present invention is summarized in that the voltage determination unit determines a voltage corresponding to an impedance lower than the middle of the maximum output impedance and the minimum output impedance in the characteristic curve as the predetermined voltage. .

  The sixth feature of the present invention is summarized in that the voltage determining unit determines a voltage corresponding to the minimum output impedance in the characteristic curve as a predetermined voltage.

  ADVANTAGE OF THE INVENTION According to this invention, even if a charging / discharging apparatus is connected to a fuel cell, the electric power which the fuel cell generated can be supplied to a load efficiently.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a diagram schematically showing a fuel cell system according to the present invention.

  As shown in FIG. 1, the fuel cell system 1 includes a fuel cell 2, a voltage regulator 3, and a charge / discharge device 4, and supplies power to a load 5 that is an external circuit. The output terminal of the fuel cell 2 is connected to the input of the voltage regulator 3, and the output of the voltage regulator 3 is connected to the charge / discharge device 4 and a load 5 that is an external circuit. Here, the load 5 and the charging / discharging device 4 are connected in parallel.

  The fuel cell 2 includes a power generation cell 21, a fuel supplier 22, and a tank 23. Depending on the type of power generation cell 21, the fuel sent from the fuel supplier 22 to the power generation cell 21, and the mechanism of the fuel supplier 22 and the substance stored in the tank 23 are different.

If the power generation cell 21 is DMFC (D irect M ethanol F uel C ell) , the fuel fed from the fuel supply unit 22 to the power generation cell 21 is methanol. For this reason, the substance accommodated in the tank 23 is methanol or a compound capable of generating methanol by the fuel supplier 22.

  When the substance stored in the tank 23 is methanol or a methanol inclusion compound, the fuel supply unit 22 is mainly configured with a pump, a valve, and the like, and supplies methanol as fuel to the power generation cell 21.

  When the substance stored in the tank 23 is a compound capable of generating methanol with the fuel supply device 22, the fuel supply device 22 is a reactor capable of extracting methanol from the compound capable of generating methanol by chemical operation. And is configured to supply methanol as a fuel to the power generation cell 21.

  When the power generation cell 21 is a PEFC (Polymer Electrolyte Fuel Cell) that requires hydrogen as a fuel, the fuel sent from the fuel supplier 22 to the power generation cell 21 is hydrogen. For this reason, the substance accommodated in the tank 23 is hydrogen or a compound capable of generating hydrogen by the fuel supplier 22.

  When the substance stored in the tank 23 is hydrogen, the tank 23 is a liquid hydrogen cylinder, a high-pressure hydrogen cylinder, a hydrogen storage alloy tank, or the like, and stores hydrogen. The stored hydrogen is supplied to the power generation cell 21 by a fuel supplier 22 such as a valve or a regulator.

  When the substance stored in the tank 23 is a compound capable of generating hydrogen by the fuel supplier 22, the fuel supplier 22 generates hydrogen from the compound capable of generating hydrogen by chemical operation such as hydrolysis or steam reforming. The reactor is mainly composed of a reactor, a reformer, and the like that can take out hydrogen, and supplies hydrogen as a fuel to the power generation cell 21.

  Here, the compound capable of generating hydrogen in the fuel supplier 22 is an alcohol such as methanol, a metal hydride such as sodium borohydride (inorganic hydride), an organic hydride such as cyclohexane or decalin, aluminum or magnesium. Any material can be used as long as it can extract hydrogen by chemical operation, such as metal powder.

  The voltage adjustment device 3 adjusts the output voltage output from the fuel cell 2 to a predetermined voltage. For example, the voltage adjusting device 3 includes a device that adjusts the DC voltage input to the voltage adjusting device 3 and outputs a stabilized DC voltage or AC voltage. A voltage regulator that outputs a stabilized DC voltage is called a DC-DC converter. A voltage regulator that outputs a stabilized AC voltage is called a DC-AC converter.

  The DC-DC converter only needs to convert the DC voltage of the fuel cell into a DC voltage that does not hinder the operation of the load and supply power to the load. The supply voltage to the load is stabilized and constant. More preferably. For example, a DC-DC converter includes a series regulator, a switching regulator, a charge pump, a switched capacitor, and the like.

  Similarly, the DC-AC converter only needs to convert the DC voltage of the fuel cell into an AC voltage that does not hinder the operation of the load and supply power to the load. For example, a transformer etc. are mentioned in DC-AC converter.

  The set value of the output voltage (predetermined voltage) of the voltage adjusting device 3 varies depending on the type of secondary battery or capacitor constituting the charging / discharging device 4 mounted on the fuel cell system 1.

  The lower limit value of the set value of the output voltage of the voltage adjusting device 3 is preferably equal to or higher than the higher one of the operation lower limit voltage of the load 5 and the discharge end voltage of the secondary battery constituting the charge / discharge device 4. . Further, the upper limit value of the set value of the output voltage of the voltage regulator 3 is the lower of the charging voltage that can fully charge the secondary battery constituting the charging / discharging device 4 or the maximum withstand voltage of the load 5. The following is desirable.

  For example, when the operation lower limit voltage of the load 5 is 3.3 V, the maximum withstand voltage is 6.0 V, and a lithium ion secondary battery is used as the charge / discharge device 4, the discharge end voltage of the charge / discharge device 4 is 3. Since 0V and the charging voltage are 4.2V, the output voltage of the voltage regulator 3 in this case is set in the range of 3.3V to 4.2V. In many cases, the set value of the output voltage of the voltage adjusting device 3 is preferably a voltage value in the vicinity of the nominal voltage of the secondary battery or the battery constituting the charging / discharging device 4, and a lithium ion secondary battery is used as the charging / discharging device 4. When used, the set value of the output voltage of the voltage regulator 3 is 3.6 to 3.8 V per lithium ion secondary battery cell.

A more effective setting value of the output voltage of the voltage adjusting device 3 is a series internal resistance value by direct current or alternating current by measuring a secondary battery constituting the charging / discharging device 4 using a measuring instrument such as an impedance analyzer, or an output impedance. Set based on the value.

Specifically, the relationship between the output impedance of the charging / discharging device 4 and the output voltage of the charging / discharging device 4 is measured, and a characteristic curve indicating the relationship between the two is calculated as shown in FIG. The output voltage corresponding to the value of the output impedance (or series internal resistance value) lower than the maximum output impedance in the characteristic curve is set as the output voltage (predetermined voltage) of the voltage regulator 3.

  Here, an example of a method for setting the output voltage of the voltage regulator 3 when a lithium ion secondary battery is used as the charge / discharge device 4 will be described. The current value such as the maximum current consumption assumed for the load 5 and the rated current value of the load 5 is Io, and the charge / discharge device voltage, which is the voltage of the lithium ion secondary battery immediately before outputting Io from the lithium ion secondary battery, is Vi. When the current is output from the lithium ion secondary battery, the voltage corresponding to the drop of the lithium ion secondary battery is defined as Vdd.

  In the present embodiment, Vdd is used as the following value. As shown in FIG. 3, after Io is output from the lithium ion secondary battery and the charging / discharging device voltage of the lithium ion secondary battery is lowered, the variation point at which the rate of change in the voltage drop of the lithium ion secondary battery changes is identified. To do. A value obtained by subtracting the voltage value corresponding to the mutation point from Vi is used as Vdd.

  In the setting method of the output voltage of the voltage regulator 3, first, the output impedance Rz when the charge / discharge device voltage of the lithium ion secondary battery is Vi is obtained from Rz = Vdd / Io. Then, the charging / discharging device voltage Vi of the lithium ion secondary battery is changed, and the output impedance Rz corresponding to the changed charging / discharging device voltage Vi is calculated in the same manner as described above. The output impedance Rz corresponding to the change in the charging / discharging device voltage Vi is a characteristic curve as shown in FIG.

  In the present embodiment, Vi corresponding to an impedance lower than the maximum output impedance is set as the output voltage of the voltage regulator 3 in the characteristic curve shown in FIG.

  In the above characteristic curve, it is preferable that an output voltage corresponding to an impedance lower than the middle between the maximum output impedance and the minimum output impedance is set as the output voltage (predetermined voltage) of the voltage regulator 3. In the above characteristic curve, the voltage corresponding to the minimum output impedance is most preferably set as the output voltage (predetermined voltage) of the voltage regulator 3.

  The charging / discharging device 4 is a secondary battery that can be repeatedly charged and discharged, such as a lead storage battery, a nickel hydride secondary battery, or a lithium ion secondary battery, or a voltage applied to a capacitor, a capacitor, an electric double layer capacitor, or the like. It is possible to use a capacitor that stores electric charge / electrostatic energy and obtains electric capacity. The secondary battery is preferably a battery that does not exhibit a memory effect, such as a nickel cadmium secondary battery. In addition, an appropriate secondary battery or capacitor type is selected according to the operating voltage, minimum operating voltage, load characteristics, etc. of the load 5, and the voltage supplied to the load 5 by connecting the secondary battery or capacitor in series as necessary. It is possible to adjust.

The electric capacity of the charging / discharging device is set so that when the fuel cell system 1 supplies power to the load 5 and the internal circuit of the fuel cell system 1, power is stably supplied when the load 5 and the fuel cell system 1 operate. It is necessary to have the minimum capacity possible.
According to such a feature, it is possible to minimize energy loss that occurs when converting the energy of the fuel that the fuel cell has into electrical energy required for power supply to the load and charging / discharging of the charging / discharging device. It is possible to reduce generation of useless power and fuel consumption due to the power generation of the battery, and to improve the energy conversion efficiency of the fuel cell system.

  That is, the voltage adjustment device 3 supplies the voltage corresponding to the output impedance lower than the maximum output impedance in the charge / discharge device 4 to the charge / discharge device 4. Thereby, since the voltage regulator 3 can supply the voltage which reduces the output impedance of the charging / discharging apparatus 4 to the charging / discharging apparatus 4, electric power becomes difficult to be consumed wastefully by the output impedance of the charging / discharging apparatus 4. The electric power generated by the fuel cell 2 can be efficiently supplied to the load.

  Moreover, since the voltage adjustment apparatus 3 can supply the voltage corresponding to the impedance lower than the intermediate | middle of the maximum output impedance and the minimum output impedance in the charging / discharging apparatus 4 to the charging / discharging apparatus 4, the charging / discharging apparatus 4 The wasteful power consumed by the output impedance can be effectively reduced, and the power generated by the fuel cell 2 can be efficiently supplied to the load.

  Furthermore, since the voltage regulator 3 supplies the voltage corresponding to the minimum output impedance in the charging / discharging device 4 to the charging / discharging device 4, the wasteful power consumed by the output impedance of the charging / discharging device 4 is more effectively reduced. The electric power generated by the fuel cell 2 can be supplied more efficiently to the load.

Example 1
FIG. 4 is a schematic diagram of a fuel cell to which the present invention is applied in this embodiment. The fuel cell 20 to which the present invention is applied may be any mechanism that can generate electricity by supplying fuel and generate electric power, and does not specifically limit the power generation cell, the fuel supplier, or the cylinder. The fuel cell 20 is configured by a PEFC type power generation cell 24 that generates power by supplying hydrogen, a pressure regulator as the fuel supplier 25, and a hydrogen storage alloy cylinder as the fuel tank 26.

  As a voltage regulator for inputting the output of the fuel cell 20, a switching regulator type voltage regulator 30 capable of step-up / step-down, which is a DC-DC converter, was used. The average voltage conversion efficiency of the voltage regulator 30 is 85%.

  The switch 6 was connected to the output of the voltage regulator 30 in series with the output of the voltage regulator 30. The switch 6 is used to prevent a reverse current flow or voltage application from the previously connected power storage element or load to the voltage regulator 30 or the fuel cell 20. The switch 6 may be a circuit element that can switch or cut off the path of the current flowing through the switch 6. For example, the switch 6 includes a diode such as a Schottky diode, a circuit element such as a field effect transistor (MOS-FET), a bipolar transistor, a relay element, and a toggle switch. Moreover, the switch 6 may be comprised by at least 1 or more of these circuit elements. In this embodiment, a Schottky diode 60 is used as the switch 6.

  Here, the power consumption of the load 50 is 3 W on average, the maximum withstand voltage whose input voltage range is the upper limit value of the voltage is 6.0 V, and the operating lower limit voltage which is the lower limit value of the voltage is 3.0 V. This load 50 has a pulse load characteristic, and the maximum current consumption is 1.6 A (0.4 seconds or less).

  Since the power generation cells constituting the fuel cell require a power generation capability capable of supplying 3 W, which is the average power consumption of the load 50, 3 [W] in consideration of the voltage conversion efficiency 85% of the voltage regulator 30 ÷ About 3.6W derived from 85% was configured to be output. The output voltage of the power generation cell when the power generation cell was 3.6 W, that is, the output voltage of the fuel cell 20 was 1.8V.

  In order to operate the load 50, the output of the fuel cell 20 alone cannot cope with the pulse load, and the load 50 may stop operating or malfunction. Therefore, it is necessary to select a charge / discharge device that can be applied in the input voltage range of the load 50. In the present embodiment, a lithium ion secondary battery having an output voltage within the input voltage range of the load 50 is used as the charge / discharge device 40.

  The usable voltage range of the lithium ion secondary battery is a charge voltage of 4.2 V, which is necessary for the upper limit to be in a fully charged state, and a lower limit voltage of 3.0 V, which is a discharge end voltage.

  Here, the output voltage range of the voltage adjusting device 30 is 3.0 to 4.2 V from the input voltage range of the load 50 and the usable voltage range of the lithium ion secondary battery. In this example, a 1000 mAh charge / discharge device 40 was used.

  The output voltage of the voltage adjusting device 30 is determined from a characteristic curve indicating the voltage characteristics of the charging / discharging device 40 of the output impedance of the charging / discharging device 40. The measurement of the voltage characteristic of the output impedance for obtaining the characteristic curve is performed by calculating the charge / discharge device from the voltage drop (Vdd) of the battery voltage when the assumed maximum current value 1.6A of the charge / discharge device 40 is output. The output impedance Rz of 40 is obtained from Vdd ÷ 1.6 [A], and this Rz is set as the output impedance at the voltage value Vi before the current is output from the charge / discharge device 40. This measurement result is the characteristic curve diagram 2 shown above. Similarly, as shown in FIG. 3 described above, Vdd is obtained from the voltage value at that point when there is a variation point in the change over time in the voltage change after the charging / discharging device outputs the current.

  In the output voltage range of 3.0 to 4.2 V of the voltage adjusting device 30, the voltage value at which the output impedance of the charging / discharging device 40 takes the lowest value from the characteristic curve shown in FIG. The value (3.8V) was set as the output voltage value of the voltage regulator 30.

  As a result, energy loss during operation of the fuel cell system is reduced, and the conversion efficiency from the fuel of the fuel cell fuel to the electrical energy obtained from the fuel cell system is improved.

  That is, according to the present embodiment, the voltage adjustment device 30 supplies the voltage corresponding to the output impedance lower than the maximum output impedance in the charge / discharge device 40 to the charge / discharge device 40. Thereby, since the voltage regulator 30 is supplying the voltage which reduces the output impedance of the charging / discharging apparatus 40 to the charging / discharging apparatus 40, it becomes difficult to consume electric power wastefully by the output impedance of the charging / discharging apparatus 40, The electric power generated by the fuel cell 20 could be efficiently supplied to the load.

  In particular, in this embodiment, since the voltage adjustment device 30 supplies the voltage corresponding to the minimum output impedance in the charging / discharging device 40 to the charging / discharging device 40, wasted power consumed by the output impedance of the charging / discharging device 40. Can be effectively reduced, and the electric power generated by the fuel cell 20 can be efficiently supplied to the load.

(Example 2)
FIG. 5 is a diagram showing a schematic diagram of a fuel cell to which the present invention is applied in this embodiment. The same parts as those in FIG. 4 shown in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  The fuel cell to which the present invention is applied may be any mechanism that can generate electricity by supplying fuel as in the first embodiment, and does not specifically limit the power generation cell, the fuel supplier, or the cylinder, In this embodiment, the fuel cell 200 is constituted by a DMFC power generation cell 27 that generates power by supplying methanol, a liquid feed pump as the fuel supply device 28, and a cartridge charged with a methanol solution as the fuel tank 29. As the voltage conversion circuit, the voltage conversion circuit 31 in which only the output voltage was separately adjusted using the circuit used in the first embodiment was used.

  The load is a load 51 having an average current consumption of 3.2 A and an input voltage range of 10 to 15 V with no large pulse load current, and is operated by the fuel cell system 11.

  When supplying power to the load 51 and the internal circuit of the fuel cell system 11, the capacity capable of stably supplying power during the operation of the load 51 and the fuel cell system 11, and after the load 51 is operated, from the charge / discharge device The charge / discharge device used in this example as a charge / discharge device capable of supplying power from the time when power is supplied to the load 51 until the fuel cell is ready to output is a lithium ion secondary having a capacity of 3600 mAh. A charge / discharge device 41 having three batteries connected in series was used. As for the voltage range of this charging / discharging device 41, the upper limit is 12.6V, which is the charging voltage, and the lower limit discharge voltage is 9.0V. Therefore, the output voltage value of the voltage regulator 41 is in the range of 10V to 12.6V.

  FIG. 6 shows the measurement result of the battery voltage dependence of the output impedance Rz of the charge / discharge device 41. From this result, Vi taking the minimum Rz within the range of the output voltage of the voltage regulator 31 is 11.4V, so the output voltage of the voltage regulator 31 was set to 11.4V.

  For convenience of operating the fuel cell system 11, although not shown in detail, the switch 61 uses an N-channel MOS-FET 62 and a timer, and connects the drain of the MOS-FET 62 to the output of the voltage regulator 31. The source of the MOS-FET 62 was connected to the output of the charge / discharge device. A 10 mΩ resistor 7 for current detection was connected in series between the charge / discharge device 41 and the load 51, and both ends of the resistor 7 were input to the voltage amplification amplifier 8. The amplifier 8 amplifies the potential difference between the two input voltages by 1000 times, and the output is input to the fuel supplier 28 constituting the fuel cell 21 and the timer constituting the switch 61. When there is an input from an amplifier exceeding 1V, the fuel supplier 28 constituting the fuel cell 21 starts operation and supplies methanol as fuel to the power generation cell. The timer constituting the switch 61 starts operation when there is an input from an amplifier exceeding 1V, and 10 seconds after the input from the amplifier exceeding 1V is received, the battery of the charge / discharge device 41 is connected to the gate of the MOS-FET 62. A voltage is applied. With this configuration, when a current of 100 mA or more is output from the charging / discharging device 41 to the load 51 after the load 51 is started, the output from the amplifier 8 becomes 1 V or more, and the pump operates and 10 seconds later. The output of the fuel cell 21 is supplied to the load 51 and the charge / discharge device 41 via the voltage adjustment device 31.

  By setting the output voltage of the voltage regulator 31 to 11.4V, the average supply power to the load 51 is 11.4 [V] × 3.2 [A] = 36.48 [W]. On the other hand, when the output voltage of the voltage regulator is set to 12.6 V in series with the lithium ion secondary battery 3 as in the prior art, the average power supplied to the load 51 is 12.6 [V] × 3.2 [ A] = 40.32 [W]. Therefore, by applying the present invention, it is possible to reduce the energy loss corresponding to about 4 W and improve the energy conversion efficiency as the fuel cell system.

  Further, according to the present embodiment, the voltage adjustment device 31 supplies the voltage corresponding to the output impedance lower than the maximum output impedance in the charge / discharge device 41 to the charge / discharge device 41. Thereby, since the voltage regulator 31 is supplying the voltage which reduces the output impedance of the charging / discharging apparatus 41 to the charging / discharging apparatus 41, it becomes difficult to consume electric power wastefully by the output impedance of the charging / discharging apparatus 41, The electric power generated by the fuel cell 200 could be efficiently supplied to the load.

  In particular, in this embodiment, since the voltage regulator 31 supplies the voltage corresponding to the minimum output impedance in the charging / discharging device 41 to the charging / discharging device 41, wasted power consumed by the output impedance of the charging / discharging device 41. The electric power generated by the fuel cell 200 can be efficiently supplied to the load.

(Other embodiments)
The predetermined voltage supplied to the charging / discharging device 41 by the fuel cell system 11 may be determined, or the voltage determining device 300 connected to the fuel cell system 11 is supplied to the charging / discharging device 41 as shown in FIG. Of course, the predetermined voltage to be determined may be determined.

  Specifically, the voltage determination device 300 includes a calculation unit 301 that calculates a characteristic curve determined by the output impedance of the charge / discharge device 41 corresponding to the voltage of the charge / discharge device 41, and the maximum output impedance in the calculated characteristic curve. A voltage determination unit 302 that determines a voltage corresponding to a lower output impedance as a predetermined voltage. Note that the operation of the voltage determination device 300 is the same as that of the above-described embodiment, and thus detailed description thereof is omitted here.

  In addition, it is preferable that the voltage determination unit 302 determines a voltage corresponding to an impedance lower than the middle between the maximum output impedance and the minimum output impedance in the characteristic curve as the predetermined voltage. Most preferably, the voltage determination unit 302 determines the voltage corresponding to the minimum output impedance in the characteristic curve as the predetermined voltage.

  The voltage determination method that operates in the voltage determination device 300 includes a calculation step for calculating a characteristic curve determined by the output impedance of the charge / discharge device 41 corresponding to the voltage of the charge / discharge device 41, and a maximum in the calculated characteristic curve. And a voltage determining step of determining a voltage corresponding to an output impedance lower than the output impedance as a predetermined voltage.

  In the voltage determination step, it is preferable that a voltage corresponding to an impedance lower than the middle between the maximum output impedance and the minimum output impedance in the characteristic curve is determined as the predetermined voltage. In the voltage determination step, the voltage corresponding to the minimum output impedance in the characteristic curve is most preferably determined as the predetermined voltage.

1 is a schematic configuration diagram of a fuel cell system according to an embodiment. It is a characteristic curve which shows the relationship between the charging / discharging apparatus voltage and output impedance of a charging / discharging apparatus. It is a figure which shows the time change of the charging / discharging apparatus voltage of a charging / discharging apparatus. 1 is a schematic configuration diagram of a fuel cell system according to Embodiment 1 of the present invention. It is a schematic block diagram of the fuel cell system which concerns on Example 2 of this invention. It is a characteristic curve which shows the relationship between the charging / discharging apparatus voltage and output impedance of the charging / discharging apparatus shown in FIG. It is a schematic block diagram of the fuel cell according to other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel cell, 3 ... Voltage regulator, 4 ... Charging / discharging apparatus, 5 ... Load, 6 ... Switch, 7 ... Resistor, 8 ... Amplifier, 10 ... Fuel cell system, 11 ... Fuel Battery system, 20 ... Fuel cell, 21 ... Power generation cell, 22 ... Fuel supply, 23 ... Fuel tank, 24 ... Power generation cell, 25 ... Fuel supply, 26 ... Fuel tank, 27 ... Power generation cell, 28 ... Fuel supply , 29 ... Fuel tank, 30 ... Voltage converter, 31 ... Voltage converter, 40 ... Charge / discharge device, 41 ... Charge / discharge device, 50 ... Load, 51 ... Load, 61 ... Switch, 200 ... Fuel cell, 300 ... Voltage determining device 301... Calculation unit 302. Voltage determining unit

Claims (8)

A fuel cell that generates electricity when supplied with fuel, a voltage regulator that regulates an output voltage output from the fuel cell to a predetermined voltage, and is connected to the voltage regulator and is supplied from the voltage regulator to a load. A voltage determining device connected to a fuel cell system comprising a charging / discharging device that performs charging / discharging according to the magnitude of the electric power,
A calculation unit that calculates a characteristic curve defined by an output impedance of the charge / discharge device corresponding to a voltage of the charge / discharge device;
A voltage determination device comprising: a voltage determination unit that determines, as the predetermined voltage, a voltage corresponding to an output impedance lower than a maximum output impedance in the calculated characteristic curve. Said voltage determining unit, a voltage corresponding to a lower impedance than the intermediate between the maximum output impedance and minimum output impedance at the characteristic curve, a voltage determination device according to claim 1 for determining as the predetermined voltage. The voltage determination device according to claim 2 , wherein the voltage determination unit determines a voltage corresponding to a minimum output impedance in the characteristic curve as the predetermined voltage.   A fuel cell system connected to the voltage determination device according to any one of claims 1 to 3,
  A fuel cell system comprising a switcher for switching a path of a current flowing through the output side of the voltage regulator.   The fuel cell system according to claim 4, wherein
  A resistor connected between the charge / discharge device and the load;
  An amplifier that inputs voltages at both ends of the resistor and amplifies a potential difference between the two input voltages;
  With
  The switch operates according to the magnitude of the potential difference amplified by the FET, the drain of which is connected to the output side of the voltage regulator, the source of which is connected to the output side of the charge / discharge device, and the amplifier, And a timer for applying an output voltage of the charging / discharging device to the gate of the FET when a predetermined time has elapsed. A fuel cell that generates electricity when supplied with fuel, a voltage regulator that adjusts the output voltage output from the fuel cell to a predetermined voltage, and a magnitude of electric power supplied from the voltage regulator to the load A voltage determination method that operates in a voltage determination device connected to a fuel cell system including a charge / discharge device that performs charge / discharge,
A calculation step for calculating a characteristic curve defined by an output impedance of the charge / discharge device corresponding to a voltage of the charge / discharge device;
A voltage determination method comprising: a voltage determination step of determining, as the predetermined voltage, a voltage corresponding to an output impedance lower than a maximum output impedance in the calculated characteristic curve. The voltage determination method according to claim 6 , wherein in the voltage determination step, a voltage corresponding to an impedance lower than an intermediate value between a maximum output impedance and a minimum output impedance in the characteristic curve is determined as the predetermined voltage. The voltage determination method according to claim 7 , wherein in the voltage determination step, a voltage corresponding to a minimum output impedance in the characteristic curve is determined as the predetermined voltage.

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