JP2003346850A - Fuel cell device and method of operating the device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell device capable of preventing the lowering of an output when operating and starting, and a method of operating the fuel cell device. <P>SOLUTION: This fuel cell device comprises a fuel cell 11 for performing a specified power generation based on the supply of fuel, an output monitoring part (sample hold circuit 22) for monitoring the generated output of the fuel cell 11 by measuring the resistance of the fuel cell 11, a control circuit 12 for generating control signals according to signals from the output monitoring part, and output converting parts 15 and 17 disposed between the fuel cell 11 and a load 18 and controlling the generated power from the fuel cell 11 to the load so as to be converted according to the control signals from the control circuit 12. By the measurement of the resistance of the fuel cell 11, a humidifying control is enabled when the fuel cell 11 is dry to realize a stable power generation output. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell device capable of generating power by supplying a fuel such as hydrogen and a method of operating the same, and more particularly to a fuel cell device capable of continuing operation while improving the operation state and its operation. About the method.

[0002]

2. Description of the Related Art A fuel cell is a device for generating electric power in a power generator by supplying a fuel fluid such as hydrogen gas or methanol. Generally, a proton conductor membrane is sandwiched between an oxygen electrode and a hydrogen electrode. It has a rigid structure. Air is supplied to the oxygen-side electrode to supply oxygen, and fuel fluid is supplied to the other hydrogen-side electrode. When the fuel cell generates power, protons move in the electrolyte membrane, which is an ion exchange membrane, react with oxygen on the oxygen-side electrode to generate current, and water is generated on the oxygen-side electrode. The power generator part of the fuel cell is an electrolyte membrane / electrode complex or MEA (Membrane E
Electrode Assembly)
A fuel cell having a planar structure is formed by arranging the electrode composites alone or in a plane, or a fuel cell having a stacked structure (stack structure) is formed by stacking the electrode assemblies.

In recent years, such fuel cells are expected to be greatly applied to electric vehicles and hybrid vehicles in the field of transportation vehicles and the like, and are also expected to be put to practical use in residential power supply systems and the like. Research and development are also being conducted on portable devices and small power supplies that utilize the lightness and compactness of fuel cells.

[0004]

Generally, when a fuel cell is incorporated in an automobile or a cogeneration system, a stable output can be obtained by operating auxiliary devices such as a reformer, a humidifier, and an air pump in cooperation with each other. It is possible to obtain On the other hand, it is not always appropriate to employ such an expensive and complicated system for a small, small-output and portable fuel cell system. Therefore, a simpler open-air cell has been devised, but this open-air cell is used when exposed to a dry environment for a long time or when operation at high temperatures is suddenly stopped. A loss of water required for a perfluorosulfonic acid-based electrolyte membrane typified by trade name) due to drying may cause a decrease in output.

That is, as one type of fuel cell, a self-humidifying fuel cell has a structure without a humidifying device for maintaining humidity for an electrolyte membrane or the like. Moisture generated at the side electrodes wets the electrolyte membrane and promotes ion exchange. The evaporation control of the water content of the fuel cell controls the power generation performance of the fuel cell itself, and the output voltage directly affects the heat generation and the output current directly affects the generated water. Therefore, the self-humidifying fuel cell uses generated water that is directly affected by the output current so as to wet the electrolyte membrane in a well-balanced manner, while preventing excessive generated water from being generated and closing the oxygen supply path. Need to drive.

However, in the self-humidifying fuel cell as described above, when the load current is reduced during operation or when the amount of transpiration is increased due to an increase in temperature, the water content of the electrolyte membrane is reduced and the fuel cell is dried. Become In this dried fuel cell, the ion exchange characteristics of the electrolyte membrane are degraded, and the output itself of the fuel cell is greatly reduced. Also, not only when the load current during operation decreases,
For example, even if the fuel cell is left for a long time, the electrolyte membrane is in a dry state when restarting after leaving the fuel cell, and it is not easy to wet the electrolyte membrane again after the restart, and the required rated output It took a long time, such as several days, to recover to the original performance so that it could be obtained. In particular, the problem of drying the electrolyte membrane is as follows.
This is remarkable in an open-to-atmosphere type fuel cell that does not perform air pumping. There is a problem that drying is caused only by leaving the fuel cell after operation, and output characteristics are reduced in a short time.

If the output current of the fuel cell fluctuates due to a load fluctuation on the load side using the output of the fuel cell, the output voltage also fluctuates based on the output characteristics. It is common practice to provide a voltage converter to stabilize the output voltage. However, if the output is reduced in the above environment, the output becomes unstable even when the voltage converter is provided.

On the other hand, a system as shown in FIG. 7 is generally devised for photovoltaic power generation, and this system employs a maximum power tracking method (MPPT: Maximum Power Point Tacker).
Method). In the system of FIG. 7, two-stage DC-DC converters 103 and 105 are provided between the load 107 that uses the output of the solar cell 101 and the solar cell 101, and the two-stage DC-DC converters 103 and 105 are provided. An electric double layer capacitor 104 for stabilizing the output is provided therebetween. Each converter 1
The outputs from the circuits 03 and 105 are respectively A / D converted and monitored by the control circuit 102.
The output from the converters 103 and 105 is controlled by the signal from the control unit 02. In the operation according to the maximum power tracking method, the control circuit 102 searches for the maximum power point by the hill-climbing method and performs control so as to follow the maximum power point. It seems that the same system can be applied to fuel cells, but it is difficult to perform optimal operation control by simply replacing the fuel cell with the solar cell because the properties of the solar cell and the fuel cell are different. . This is because extracting the maximum power of the cell is not always good for the stability and life of the fuel cell.

In view of the above technical problems, an object of the present invention is to provide a fuel cell device and a method of operating the fuel cell device, which can prevent the problem of output reduction during operation and startup.

[0010]

A fuel cell device according to the present invention includes a fuel cell unit for generating required electric power based on the supply of fuel and a power generation unit for the fuel cell unit by measuring the resistance of the fuel cell unit. An output monitoring unit that monitors an output, a control unit that generates a control signal for controlling a power generation output from the fuel cell unit according to a signal from the output monitoring unit, And an output converter for controlling the load so as to convert the power output from the fuel cell unit according to the control signal from the control unit.

In the fuel cell device of the present invention, the fuel cell unit can generate required power based on the supply of fuel. However, the power generation output is not always constant, and the temperature and the electrolyte constituting the fuel cell unit are not always constant. It also changes depending on the degree of drying of the film. Therefore, by directly measuring the resistance of the fuel cell unit, it is possible to grasp the state of the power generation output of the fuel cell unit relatively instantaneously, and to control the output conversion unit by a signal from the control unit. Exact control as a whole is realized.

Further, another fuel cell device of the present invention provides a fuel cell unit for performing required power generation based on the supply of fuel and a power generation output of the fuel cell unit by measuring the resistance of the fuel cell unit. An output monitoring unit for monitoring, a control unit for generating a control signal for controlling a power generation output from the fuel cell unit according to a signal from the output monitoring unit, and a control unit disposed between the fuel cell unit and a load. A first output converter for controlling the power output from the fuel cell unit to be convertible during operation according to the control signal from the control unit; and the control unit disposed between the fuel cell unit and a load. A second output converter for performing a required output when measuring the resistance of the fuel cell unit in response to the control signal from the unit.

Similarly, in the fuel cell device according to the present invention, the state of the power generation output of the fuel cell unit can be grasped relatively instantly by directly measuring the resistance of the fuel cell unit. By controlling the output conversion unit with a signal from the unit, accurate control as a whole is realized. In addition, by separating the first output converter that outputs during operation and the second output converter that outputs when measuring the resistance, the characteristics of the first output converter and the second output converter are changed. It can be configured differently, and optimal operation can be realized both during measurement and operation of the resistance component.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the drawings.

[First Embodiment] A first embodiment of a fuel cell device according to the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of the fuel cell device according to the first embodiment. The fuel cell device according to the present embodiment monitors the fuel cell 11 that performs required power generation based on the supply of fuel such as hydrogen or methanol, and the power generation output of the fuel cell 11 by measuring the resistance of the fuel cell 11. And a control circuit 12 comprising a microcomputer for controlling a power generation output from the fuel cell 11 in accordance with a signal from the sample and hold circuit 22, and a fuel cell. 11 and load 18
DC-DC converters 15, 1, which are output converters, which are arranged between the DC and DC converters and control the power generation output from the fuel cell unit so as to be able to convert the power generation output according to a control signal from a control circuit.
7 is a main component.

As shown in FIG. 2, the fuel cell 11 has an electrolyte membrane 41, which is a membrane through which protons pass, sandwiched between catalyst layers 48 and 49, and further has a fuel-side gas diffusion layer (GDL) 43 outside. And air side gas diffusion layer (GDL) 42
A fuel fluid such as hydrogen or methanol is supplied to the fuel-side gas diffusion layer 43 and the catalyst layer 48 through the guide groove 45 of the fuel-electrode-side current collector plate 44, and the air-side gas diffusion is performed. A power generator that generates an electromotive force between both electrodes by supplying air to the layer (GDL) 42 and the catalyst layer 49.
An electrolyte membrane electrode assembly having a structure in which an electrolyte membrane 41 is sandwiched between a fuel-side gas diffusion layer 43 and an air-side gas diffusion layer 42 is a MEA.
(Membrane Electrode Assembly) or a member called a membrane electrode assembly. The fuel-side gas diffusion layer 43 and the air-side gas diffusion layer 42 supply hydrogen (first active substance) and oxygen (second active substance) as active substances to the electrolyte membrane 41 provided with the catalyst layers 48 and 49. Fuel supply function for
A power collecting function of collecting the generated power and supplying the generated power to a load; power is taken out from an air electrode side through an air electrode side current collector plate 46 having an air hole 47 on its surface; The electric power is extracted through the fuel electrode side current collector plate 44 having the guide groove 45.

One example of an electrode manufacturing method will be described.
Platinum-supported carbon black is dispersed in a fluorine-based solid polymer resin, stirred sufficiently, applied to a carbon sheet, and then the applied portion is cured to form a carbon black. In the case of applying a material in which carbon black is dispersed in a polymer resin as described above, by curing the applied portion to form an electrode, the electrode interface is surrounded by carbon particles of 0.1 μm.
Pores of about m to about 10 μm will be distributed. These pores are gaps between carbon particles, and a catalyst such as platinum faces the pores.

The surface of the air-side gas diffusion layer 42 is open to the atmosphere through an air hole 47 formed on the surface of the fuel electrode-side current collector plate 44. The surface of the air-side electrode 42 and the electrolyte membrane are dried, and a problem such as a decrease in output occurs. In the present embodiment, as described later, the resistance component is measured by the current interruption method during operation, and an optimal operation method is selected. Therefore, drying of the electrolyte membrane or the like can be prevented beforehand, and a decrease in output can be suppressed.

A temperature sensor is attached to such a fuel cell 11, and the output of the temperature sensor is sent to a temperature sense amplifier 21. In general, the output of the fuel cell 11 is affected by the temperature. For example, when the drying degree of the fuel cell 11 becomes high due to high temperature, for example, a relatively large current is supplied for a certain period of time to promote humidification. Such control is performed to promote the production of water by activating the reaction of the active substance. If the amount of water generated increases,
The dryness of the fuel cell 11 can be reduced. The output of the temperature sense amplifier 21 is sent to the control circuit 12 via an A / D (analog / digital) converter 31. Therefore, the control circuit 12 can constantly monitor the temperature of the fuel cell 11.

A sample and hold circuit 22 is connected to the output side of the fuel cell 11. Sample hold circuit 22
Is a circuit constituting an output monitoring unit for monitoring the power generation output of the fuel cell 11 by measuring the resistance component of the fuel cell 11 by a current interrupt (current interrupt) method. It is controlled to perform sampling when the gate signal is at a high level. This timing gate signal is also supplied to the gate of the MOS-FET 13 arranged at the output stage of the fuel cell 11 at the same time. The MOS-FET 13 is turned off by the timing gate signal from the control circuit 12, and the resistance of the fuel cell 11 is measured in detail as described later with reference to FIG. Become. As an example, the timing gate signal from the control circuit 12 is a sampling MOS-signal having one of the source and drain connected to the output terminal of the fuel cell 11 and the other of the source and drain connected to the capacitor.
Control circuit 1 is supplied to the gate of an FET (not shown).
When the timing gate signal from 2 is at a high level, the sampling MOS-FET is turned on, and the capacity is charged by the voltage of the output terminal of the fuel cell 11. The voltage value charged in the capacitor is a sampled voltage, and the voltage is output to the control circuit 12 via the A / D converter 32.

[0021] The output side of the fuel cell 11, in addition to the fuel cell output current I _FC and the fuel cell output voltage V _FC of the sample-and-hold circuit 22 is configured to be monitored. The control circuit 12, the fuel cell output current _{I FC} A / D
Was monitored via the converter 33, the fuel cell output voltage _{V FC} monitored via the A / D converter 34. The control circuit 12 is the sample-and-hold circuit 22 are possible resistance component measurement, the fuel cell output current I _FC and the fuel cell output voltage V _FC is monitored even in operating conditions, for example when performing the operation based on the maximum power follow-up scheme In, it is possible to search for the maximum power point by the hill-climbing method and perform control so as to follow the maximum power point. Further, in a time of constant current mode in which the target current is set operation, the difference between the fuel cell output current I _FC and the target current is calculated in the control circuit 12 so as to realize the current value. Further, in a time of constant voltage mode in which the target voltage is set operation, the difference between the fuel cell output voltage V _FC and the target voltage so as to realize the current value is calculated by the control circuit 12.

On the output side of the fuel cell 11, a two-stage DC-DC converter 15, which is an output converter for controlling the power output from the fuel cell 11 to be convertible between the load 18 and the load 18, is provided.
17 is connected. An electric double layer capacitor 16 for stabilizing the output is provided between the two-stage DC-DC converters 15 and 17, and furthermore, a DC-DC converter is provided.
A lead storage battery 19 is provided at the output of the converter 17. In FIG. 1, the DC-DC converter 15 is the first
DC-DC converter (No. 1)
The C converter 17 is a second DC-DC converter (No. 2).

The DC-DC converters 15 and 17 are circuits for adjusting a voltage fluctuation from the fuel cell 11 side to obtain a constant output. A control signal from the control circuit 12 is supplied to the DC-DC converter 15 by using a D / A converter 23 for converting a digital signal into an analog signal. In the D / A converter 23, a control signal is further supplied by a pulse width modulation module. Is converted into a signal having a required pulse width. Similarly, a control signal from the control circuit 12 is supplied to the DC-DC converter 17 by using a D / A converter 24 for converting a digital signal into an analog signal. The D / A converter 24 further includes a pulse width modulation module. Thus, the control signal is converted into a signal having a required pulse width. For example, when it is desired to increase the output of the DC-DC converter 15, the control circuit 12 outputs a digital signal as an operation result, and the control signal is converted into a pulse signal having a large pulse width and the DC signal is converted into a DC signal.
-It is supplied to the DC converter 15 and can be controlled so as to increase the output of the DC-DC converter 15. Note that the pulse width modulation method is merely an example as a method of the control signal, and various modulation methods such as pulse amplitude modulation (PAM) and pulse number modulation (PNM) may be used. Such control from the control circuit 12 enables stable power generation output as in a constant voltage mode or a constant current mode described later.

A capacitor for maintaining the load voltage at a predetermined value by discharging is disposed between the DC-DC converters 15 and 17, and particularly in the present embodiment, an electric double layer capacitor (EDLC) 16 is used as the capacitor. Is arranged. The electric double layer capacitor 16 is a capacitor whose operation principle is, for example, an electric double layer generated at the interface between activated carbon and an electrolytic solution. The electric double layer capacitor 16 is small, has a large capacitance, is resistant to overcharging and overdischarging, and has environmental resistance. And exhibits excellent charge / discharge characteristics at low voltage. By arranging the electric double layer capacitor 16 between the DC-DC converters 15 and 17, the electric double layer capacitor 16 is connected to the electric current generated by the DC-DC converter 15 operated according to the state of the fuel cell 11. Functions as a buffer for absorbing voltage fluctuations. That is, the DC-DC converter 15 charges the electric double layer capacitor 16 with electric charge when the current is intentionally taken out from the fuel cell 11, and conversely, the DC-DC converter 15 becomes The charging of the electric double layer capacitor 16 is stopped. The DC-DC converter 17 discharges the electric charge already charged in the electric double layer capacitor 16 and performs feedback so as to keep the load voltage constant. Further, the electric double layer capacitor 16 also plays a role of a buffer for preventing the influence of the current interruption operation in the resistance measurement operation from affecting the load side, as described later. In this way, the fuel cell 11 and the load 18 can operate to some extent independently.

The output of the DC-DC converter 15 is controlled by the control circuit 12 as described above, and the current and voltage around the electric double layer capacitor 16 are controlled by the fuel cell 1
1 is monitored in the same manner as the output unit. Specifically, the control circuit 12 controls the electric double layer capacitor current I
_C and an electric double layer capacitor voltage V _C is monitored.
The control circuit 12, an electric double layer capacitor current _{I C} to A /
It was monitored via a D converter 35, an electric double layer capacitor voltage V _C is monitored through the A / D converter 36. The current and voltage around the electric double layer capacitor 16 are the current and voltage of the output of the DC-DC converter 15 and the current and voltage of the output of the DC-DC converter 17. By monitoring these, highly accurate fuel cell operation is realized.

The DC-DC converter 17 also has a DC-D
Similarly to the C converter 15, a control signal from the control circuit 12 is supplied by using a D / A converter 24 for converting a digital signal into an analog signal, and the D / A converter 24 further requires a control signal by a pulse width modulation module. And the output voltage of the DC-DC converter 17 is controlled according to the pulse width. On the output side of the DC-DC converter 17, a lead storage battery 19 is arranged between the DC-DC converter 17 and a load 18. The lead storage battery 19 is a secondary battery disposed before the load 18, and has a floating connection in the present embodiment. It is also possible to adopt a configuration in which the lead storage battery 19 is not provided according to the conditions of the load 18. The current and voltage around the lead-acid battery 19 are respectively monitored similarly to the output of the electric double layer capacitor. Specifically, the control circuit 1
Lead-acid battery current I _C and the lead-acid battery voltage V _C is monitored by two. The control circuit 12, a lead-acid battery current _{I B} A /
The lead-acid battery voltage _VL is monitored via an A / D converter 38 and monitored via a D-converter 37.
The load current _{IL is} also monitored by the control circuit 12 via the A / D converter 39.

The fuel cell apparatus according to the present embodiment having the above-described circuit configuration operates as follows. First, during normal operation of the fuel cell device of the present embodiment, the output current and voltage are set so as to be selectable depending on the operation state. For example, operation in the maximum power follow-up mode, constant current mode or constant current mode is performed. Operation in voltage mode is selected. In the operation by the maximum power tracking method, the maximum power point is searched by the hill-climbing method, and the apparatus is operated so as to follow the searched point. The constant current mode is the operation mode to keep the current from the fuel cell constant, by comparing the target current and the fuel cell output current I _FC that is set, CPU arithmetic operation of the amount of the control circuit 12 in accordance with the difference I do. The calculation result is converted into a voltage value by the D / A converter 23, and this voltage is converted into a pulse width by the PWM modulator and input to the DC-DC converter 15. The DC-DC converter 15 receives the pulse width modulation signal from the D / A converter 23 and performs control so as to obtain an appropriate output value. Similar control is performed by the DC-DC converter 17 in the subsequent stage.
Is also performed. The constant voltage mode is an operation mode in which the output voltage of the fuel cell 11 is kept constant. It compares the set target voltage and the fuel cell output voltage V _FC, the amount of control circuit 12 CPU corresponding to the difference is computed. The operation result is converted to a voltage value by the D / A converter 23, and this voltage is converted to a pulse width by the PWM
Input to the C-DC converter 15. The DC-DC converter 15 receives the pulse width modulation signal from the D / A converter 23 and performs control so as to obtain an appropriate output value. Similar control is performed for the DC-DC converter 17 at the subsequent stage.

The above is an example of the normal operation. During the normal operation, the fuel cell device enters the resistance measuring mode periodically or randomly and measures the resistance of the fuel cell itself. When it is determined that the electrolyte membrane or the like is dry as a result of the resistance measurement, the humidification mode is entered. When it is determined that the electrolyte membrane or the like is not dry as a result of the resistance measurement, control is performed so as to return to normal operation.

FIG. 3 shows the flow of this control.
When the operation is started, the normal operation mode S11 is entered. For example, the operation in the constant current mode or the constant voltage mode as described above is selected. Next, it is determined whether or not it is the timing of measurement (S12). If it is not the timing of measurement (NO), it is determined in step S16 whether or not the operation for power generation has ended. If it is determined in step S16 that the operation is to be terminated, the process ends. If it is determined that the operation is to be continued, the process returns to the normal operation mode S11 and repeats the above procedure. In the normal operation mode, for example, the resistance component measurement mode is periodically entered, and the state of the electrolyte membrane is grasped, and if necessary, the mode shifts to the humidification mode. Standard I-
It is possible to grasp the degree of the situation compared to the V characteristic, and to adjust the current and voltage according to the degree.

If it is determined in step S12 that the timing of measurement has been reached (YES), the process enters the resistance measurement mode S13. In the present embodiment, since the resistance of the fuel cell is measured by the current interruption method, the timing gate signal from the control circuit 12 first shifts from a low level to a high level in the block diagram of FIG. MOS-FE
T13 enters the cutoff state, and transitions to a state in which the current on the output side stops flowing. At the same time, the sample-and-hold circuit 22 also shifts to the sampling state, and samples a rise in potential when the output current of the fuel cell 11 is stopped.

Here, the measurement mode of the resistance component of the fuel cell device will be described in detail with reference to FIG. When the voltage at the output terminal of the fuel cell 11 in the normal operation mode is V ₀
, And the now timing gate signal from the control circuit 12 at timing t ₁ is assumed to have shifted from the low level to the high level. As a result, the transition to the cutoff state of the MOS-FET 13, and increases the potential of the output terminal of the fuel cell 11, is the timing t ₂ in once abruptly timing a relatively short time after the sampling from the timing t ₁ of the start A state in which the increased voltage gradually increases.

In general, for example, an internal impedance equivalent circuit of a fuel cell as shown in FIG. 5 has been proposed. When a current is interrupted, a DC resistance dependent on the conductivity of the electrolyte membrane: a voltage drop due to Rs = ( rs x is) is zero instantaneously, t ₂ after the electric double layer capacity: Faraday impedance electric charge charged in the Cd corresponds to the electrode reaction process:
A voltage change model that gradually discharges according to (Rθ + Zw) is considered and actually observed.

[0033] Here, if the sample-hold circuit 22 has performed the sampling at a timing t _2, the fuel cell 1
Since the degree of increase in the potential of the output terminal differs depending on the degree of drying of 1, different voltages are sampled. Voltage V _W shown by the solid line at the point of time t ₂ in FIG. 4 has a low dryness of the fuel cell 11 shows a state where the operation efficiently In the fuel cell 11 is wet in other words,
Voltage decreases sample-and-hold circuit 22 at the time of the timing t ₂ is sampled. In contrast, in the case of a high dryness of the fuel cell 11, voltage jumps significantly from the voltage V ₀ to the voltage V _D shown by a broken line at the point of time t ₂ in FIG. 4 in a short period, the fuel cell 11 on the dry Is clearly distinguished by the voltage value sampled by the sample and hold circuit 22.

The fact that a large jump in voltage at the time of sampling indicates that the dryness of the electrolyte membrane is high is derived as follows. In the fuel cell, the DC resistance component Rs is represented by _{Rs = (V D or V W} -V 0) / Is, where voltage V _D or the voltage _{V W} is the voltage at the sampling, the current Is Is the current at the time of sampling. The voltage V ₀ is the sampling previous voltage. The DC resistance component of the fuel cell is obtained by calculating the difference between the held voltages while measuring the current at the time of sampling from this equation.
Rs will be obtained. In a fuel cell, when the electrolyte membrane is dry, the proton conductivity is low and the resistance value is high. Therefore, by measuring the resistance of the fuel cell by such a current interruption method, it is possible to measure the degree of dryness of the electrolyte membrane. If the voltage jumps greatly at the time of sampling, it is determined that humidification is necessary. Then, the apparatus is controlled to enter the humidification mode.

Returning again to the flowchart of FIG. 3, in step S14, the timing t ₂ at the time of sampling in FIG.
Is the voltage on the voltage V _D (during drying) side or the voltage V _W
It is determined whether the voltage is on the (wet) side and the voltage V _D (dry)
If it is determined that the voltage is on the side, the process proceeds to step S15 to enter the humidification mode. Further, in the case where voltage when the timing t ₂ is determined as the voltage of the voltage V _{W (wet)} side,
The procedure returns to the normal operation mode in step S11, and each procedure in the previous normal operation mode is repeated.

Here, the humidification mode will be described. Generally, in a fuel cell, the humidification amount of the electrolyte membrane can be controlled by extracting a relatively large current from the fuel cell for a certain period. That is, the flow of an electric current promotes the reaction of the active substance, and the amount of water generated by the reaction increases in accordance with the reaction. Water generated at the reaction interface on the cathode side causes a concentration gradient and reverse diffusion of water toward the anode side, so that the electrolyte membrane is quickly and reliably humidified. However, if a current close to the short-circuit current is passed, it has an adverse effect on the carbon carried by the catalyst and the like, and it is necessary to limit the current. Therefore, in the above-described constant voltage mode, by controlling the voltage to be a certain set voltage, it is possible to flow a current corresponding to the state of the fuel cell at that time. If the fuel cell dries due to overheating, the temperature detected by the temperature sensor is determined.If the temperature is high, the fuel cell is cooled with a cooling fan to effectively humidify and the steam is saturated. Make it easier.

As described above, in the fuel cell device of this embodiment, the resistance of the fuel cell itself is measured during the normal operation mode. As a result of this measurement, when it is determined that the electrolyte membrane is dry, the mode shifts to the humidification mode, and the electrolyte membrane is reasonably wetted while selecting the maximum current that can be passed. After performing such humidification processing, it is possible to return to the normal operation mode again and continue power generation.

Second Embodiment A second embodiment of the fuel cell device according to the present invention will be described with reference to FIG.
FIG. 6 is a block diagram of the fuel cell device according to the second embodiment. The fuel cell device according to the present embodiment includes a fuel cell 51 that performs required power generation based on the supply of fuel such as hydrogen or methanol.
A sample and hold circuit 62 that constitutes an output monitoring unit for monitoring the power generation output of the fuel cell 51 by measuring the resistance of the fuel cell 51; and a fuel cell in accordance with a signal from the sample and hold circuit 62. A control circuit 52 comprising a required microcomputer for controlling the power generation output from the fuel cell 51, and the fuel cell unit disposed between the fuel cell 51 and the load 58 in accordance with a control signal from the control circuit. -DC converters 55, 57, and 60, which are output conversion units that control the power generation output from
Are the main components.

The fuel cell 51 is the same as the fuel cell 11 whose one example is shown in FIG. 2, and the duplicate description is omitted here for simplicity. Generally, the output of the fuel cell 11 is affected by the temperature. For example, when the drying degree of the fuel cell 11 is increased due to the high temperature,
For example, control is performed such that a relatively large current is applied for a certain period of time to promote humidification, and the reaction of the active substance is activated to promote the generation of water. If the amount of generated water increases, the degree of dryness of the fuel cell 51 can be reduced.

The output side of the fuel cell 51 is connected to a sample and hold circuit 62. Sample hold circuit 62
Is a circuit constituting an output monitoring unit for monitoring the power generation output of the fuel cell 51 by measuring the resistance component of the fuel cell 51 by a current interrupt (current interrupt) method. It is controlled to perform sampling when the gate signal is at a high level. This timing gate signal is also supplied to the gate of the MOS-FET 53 arranged at the output stage of the fuel cell 51 at the same time. The MOS-FET 53 is turned off by the timing gate signal from the control circuit 52, and the resistance of the fuel cell 51 is measured in detail by sampling in the sample and hold circuit 62.

For example, the timing gate signal from the control circuit 52 is a sampling MOS-FET in which one of the source and drain is connected to the output terminal of the fuel cell 51 and the other of the source and drain is connected to the capacitor.
(Not shown), the sampling MOS-FET is turned on when the timing gate signal from the control circuit 52 is at a high level, and the capacity of the fuel cell 5 is reduced.
1 is charged by the voltage of the output terminal. The voltage value charged to the capacitor is a sampled voltage, and the voltage is output to the control circuit 52 via the A / D converter 72.

The output side of the fuel cell 51, in addition to the fuel cell output current I _FC and the fuel cell output voltage V _FC of the sample-and-hold circuit 62 is configured to be monitored. The control circuit 52, the fuel cell output current _{I FC} A / D
Was monitored via the converter 73, the fuel cell output voltage _{V FC} monitored via the A / D converter 74. The control circuit 52 is the sample-and-hold circuit 62 are possible resistance component measurement, the fuel cell output current I _FC and the fuel cell output voltage V _FC is monitored even in operating conditions, for example when performing the operation based on the maximum power follow-up scheme In, it is possible to search for the maximum power point by the hill-climbing method and perform control so as to follow the maximum power point. Further, in a time of constant current mode in which the target current is set operation, the difference between the fuel cell output current I _FC and the target current is calculated in the control circuit 52 so as to realize the current value. Further, in a time of constant voltage mode in which the target voltage is set operation, the difference between the fuel cell output voltage V _FC and the target voltage so as to realize the current value is calculated by the control circuit 52.

On the output side of the fuel cell 51, a two-stage DC-DC converter 55, which is an output converter for controlling the power output from the fuel cell 51 to be convertible between the load 58 and the load 58,
57 are connected. An electric double layer capacitor 56 for stabilizing the output is provided between the two-stage DC-DC converters 55 and 57.
A lead storage battery 59 is provided at the output of the converter 57. In FIG. 5, the DC-DC converter 55 is the first
DC-DC converter (No. 1)
The C converter 57 is a second DC-DC converter (No. 2). In addition to the two-stage DC-DC converters 55 and 57, the fuel cell device of the present embodiment includes a DC-DC converter 60 used during normal operation. That is, two-stage DC-DC converters 55 and 57 are used at the time of resistance measurement, and one-stage D-DC converters 55 and 57 are used.
The C-DC converter 60 is used during normal operation. Two-stage DC-DC converters 55 and 57 and one-stage D
The C-DC converter 60 is connected in parallel between the load 58 and the fuel cell 51, and the converter is switched by a signal from the control circuit 52.

The DC-DC converters 55 and 57 are circuits for adjusting the fluctuation of the voltage from the fuel cell 51 to obtain a constant output. In the present embodiment, the DC-DC converters 55 and 57 are used when the resistance of the fuel cell 51 is measured. Is done. A control signal from the control circuit 52 is supplied to the DC-DC converter 55 by using a D / A converter 63 for converting a digital signal into an analog signal. In the D / A converter 63, a control signal is further supplied by a pulse width modulation module. Is converted into a signal having a required pulse width. Similarly, a control signal from the control circuit 52 is supplied to the DC-DC converter 57 by using a D / A converter 64 that converts a digital signal into an analog signal, and the D / A converter 64
Then, the control signal is converted into a signal having a required pulse width by the pulse width modulation module. For example, DC
When it is desired to increase the output of the DC converter 55, the control circuit 52 outputs a digital signal as a calculation result, and the control signal is converted into a pulse signal having a large pulse width and supplied to the DC-DC converter 55. DC
-It can be controlled to increase the output of the DC converter 55. Note that the pulse width modulation method is merely an example as a method of the control signal, and various modulation methods such as pulse code modulation, pulse number modulation, and pulse phase modulation may be used. By such control from the control circuit 52, a stable power generation output is possible as in a constant voltage mode or a constant current mode described later.

A capacitor for maintaining the load voltage at a predetermined value by discharging is provided between the DC-DC converters 55 and 57. In this embodiment, an electric double layer capacitor (EDLC) 56 is used as the capacitor. Is arranged. The electric double layer capacitor 56 is a capacitor whose operation principle is, for example, an electric double layer generated at an interface between activated carbon and an electrolytic solution. The electric double layer capacitor 56 is small, has a large capacitance, is resistant to overcharging and overdischarging, and is environmentally friendly. It is excellent and shows excellent charge / discharge characteristics at low voltage. By arranging the electric double-layer capacitor 56 between the DC-DC converters 55 and 57, the electric double-layer capacitor 56 is connected to the current generated by the DC-DC converter 55 operated according to the state of the fuel cell 51. Functions as a buffer for absorbing voltage fluctuations. That is, when it is desired to intentionally take out the current from the fuel cell 51, the DC-DC converter 55 charges the electric double layer capacitor 56 with electric charge, and when it is not desired to take out the current due to a decrease in output, the DC-DC converter 55 The charging of the electric double layer capacitor 56 is stopped. The DC-DC converter 57 discharges the electric charge already charged in the electric double layer capacitor 56, and performs feedback so as to keep the load voltage constant. Also,
The electric double layer capacitor 56 also serves as a buffer for preventing the influence of the current interruption operation in the resistance measurement operation from affecting the load side, as described later. In this manner, the fuel cell 51 and the load 58 can operate independently to some extent.

The DC-DC converter 60 is a circuit for adjusting the fluctuation of the voltage from the fuel cell 51 to obtain a constant output. In the present embodiment, the DC-DC converter 60 is used during normal operation of the fuel cell 51. . DC-DC converter 60
, A control signal from the control circuit 52 is supplied using a D / A converter 65 that converts a digital signal into an analog signal. In the D / A converter 65, the control signal is further converted to a required pulse width by a pulse width modulation module. Is converted to a signal having The DC-DC converter 60 is, for example, a voltage conversion unit used as a power supply path when the humidification operation is completed and the operation mode is shifted to the normal operation mode. Thus, the DC-DC converter 60 is used as a power supply path. When used, the DC-DC converters 55 and 57, which are other power supply paths, are turned off. The DC-DC converter 60 requires fewer stages than the two-stage DC-DC converters 55 and 57, and the efficiency of one DC-DC converter is improved by using the single DC-DC converter 60. be able to.

Although the output of the DC-DC converter 55 is controlled by the control circuit 52 as described above, the current and voltage around the electric double layer capacitor 56 are
1 is monitored in the same manner as the output unit. Specifically, the control circuit 52 controls the electric double layer capacitor current I
_C and an electric double layer capacitor voltage V _C is monitored.
The control circuit 52, an electric double layer capacitor current _{I C} to A /
It was monitored via a D converter 75, an electric double layer capacitor voltage V _C is monitored via the A / D converter 76. The current and the voltage around the electric double layer capacitor 56 are the current and the voltage of the output of the DC-DC converter 55 and the current and the voltage of the output of the DC-DC converter 57. By monitoring these, highly accurate fuel cell operation is realized.

The DC-DC converter 57 also has a DC-D
Similarly to the C converter 55, a control signal from the control circuit 52 is supplied by using a D / A converter 64 for converting a digital signal into an analog signal. In the D / A converter 64, a control signal is further required by a pulse width modulation module. , And the output voltage of the DC-DC converter 57 is controlled according to the pulse width. On the output side of the DC-DC converter 57, a lead storage battery 59 is arranged between the DC-DC converter 57 and a load 58. The lead storage battery 59 is a secondary battery disposed before the load 58, and has a floating connection in the present embodiment. It is also possible to adopt a configuration in which the lead storage battery 59 is not provided according to the condition of the load 58. The current and the voltage around the lead storage battery 59 are respectively monitored similarly to the output part of the electric double layer capacitor. Specifically, the control circuit 5
Lead-acid battery current I _C and the lead-acid battery voltage V _C is monitored by two. The control circuit 52, a lead-acid battery current _{I B} A /
The lead-acid battery voltage _VL is monitored via an A / D converter 78 by monitoring via a D-converter 77.
The load current _{IL is} also monitored by the control circuit 52 via the A / D converter 79.

The DC-DC converter 60 also has a DC-D
Similarly to the C converter 55, a control signal from the control circuit 52 is supplied by using a D / A converter 65 for converting a digital signal into an analog signal. In the D / A converter 65, the control signal is further required by a pulse width modulation module. , And the output voltage of the DC-DC converter 60 is controlled according to the pulse width. As described above, in the present embodiment, DC
The path of the DC converter 60 is used during normal operation, and the paths of the two-stage DC-DC converters 55 and 57 are used during resistance measurement by the current interruption method. DC-DC
The converter 60 is a two-stage DC-DC converter 5
The number of stages is smaller than in the case of 5, 57, and the efficiency of one DC-DC converter can be improved by using the single DC-DC converter 60.

In the fuel cell device of the present embodiment, similarly to the fuel cell device of the first embodiment, a predetermined resistance measurement of the fuel cell itself is performed during the normal operation mode. As a result of this measurement, when it is determined that the electrolyte membrane is dry, the mode shifts to the humidification mode, and the electrolyte membrane is reasonably wetted while selecting the maximum current that can be passed. After performing such humidification processing, it is possible to return to the normal operation mode again and continue power generation. In the normal operation mode, the DC-DC converter 5
A single DC-DC converter 60 having a smaller number of stages than that of the converters 5 and 57 is used by switching, so that the efficiency is greatly improved.

In the present invention, any equipment on which the fuel cell device is mounted can be used.
Personal computers, mobile phones and PDAs (Persona
l Digital Assistant) and other electronic devices, the present invention
Printers and fax machines, PC peripherals, telephones, television receivers, image display devices, communication devices, cameras, audio / video devices, electric fans, refrigerators, hair dryers, irons, pots, vacuum cleaners, rice cookers, electromagnetic cookers, Lighting equipment, toys such as game consoles and radio control cars,
Power tools, medical equipment, measuring equipment, on-vehicle equipment, office equipment, health and beauty equipment, electronically controlled robots, clothing-type electronic equipment, various electric equipment, vehicles for transportation such as vehicles, ships, aircraft, home use or business It can be used for power generators and other applications.

In the present invention, an example in which hydrogen gas is mainly used as a fuel has been described. However, an alcohol such as methanol (liquid) may be used as a fuel in accordance with a so-called direct methanol method.

[0053]

According to the fuel cell device of the present invention, the resistance of the fuel cell itself is measured during the normal operation mode. When it is determined that the electrolyte membrane is dry as a result of the measurement, the mode shifts to the humidification mode, and the electrolyte membrane is reasonably wetted while, for example, selecting the maximum current that can be passed. For this reason, a stable output is performed without causing a decrease in the power generation output. Further, according to the fuel cell device of the present invention, it is possible to use different voltage converters at the time of resistance measurement and at the time of normal operation, and in particular, by using a voltage converter having a small number of stages for normal operation. Efficiency can be increased.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a circuit configuration of a fuel cell device according to a first embodiment of the present invention.

FIG. 2 is a schematic partial perspective view of a fuel cell portion of the fuel cell device according to the first embodiment of the present invention.

FIG. 3 is a flowchart illustrating a procedure of a power generation operation of the fuel cell device according to the first embodiment of the present invention.

FIG. 4 is a time chart for explaining resistance measurement by a current interruption method in the fuel cell device according to the first embodiment of the present invention.

FIG. 5 is an internal impedance equivalent circuit diagram of the fuel cell in the fuel cell device according to the first embodiment of the present invention.

FIG. 6 is a block diagram illustrating a circuit configuration of a fuel cell device according to a second embodiment of the present invention.

FIG. 7 is a block diagram illustrating a circuit configuration of a conventional solar cell device.

[Explanation of symbols]

11 Fuel cell 12 Control circuit 13 Sampling 15 DC-DC converter 16 Electric double layer capacitors 17 DC-DC converter 18 Load 19 Lead storage battery 21 Temperature sense amplifier 22 Sample hold circuit 23, 24 D / A converter 31-39 A / D converter 41 electrolyte membrane 42 Air-side gas diffusion layer 43 Fuel side gas diffusion layer 44 Fuel electrode side current collector 45 Guide groove 46 Air electrode side current collector 47 air hole 48, 49 catalyst layer 51 Fuel cell 52 control circuit 53 MOS-FET 55 DC-DC converter 56 Electric Double Layer Capacitor 57 DC-DC converter 58 load 59 Lead storage battery 60 DC-DC converter 72 Sample hold circuit 63-65 D / A converter 72-79 A / D converter

Claims (19)

[Claims] 1. A fuel cell unit for performing required power generation based on supply of fuel, an output monitoring unit for monitoring a power generation output of the fuel cell unit by measuring a resistance component of the fuel cell unit, and the output monitoring. A control unit for generating a control signal for controlling a power generation output from the fuel cell unit in response to a signal from the unit, and a control signal from the control unit disposed between the fuel cell unit and a load. The fuel cell device according to claim 1, further comprising an output conversion unit that controls the load so that the power generation output from the fuel cell unit can be converted. 2. The fuel cell device according to claim 1, wherein the fuel cell unit has a structure in which an electrolyte membrane is sandwiched between a fuel electrode and an air electrode. 3. The fuel cell device according to claim 2, wherein the air-side electrode of the fuel cell unit is open to the atmosphere. 4. The fuel cell device according to claim 1, wherein the output monitoring unit measures the resistance of the fuel cell unit while interrupting a current supplied to a load. 5. The fuel cell device according to claim 4, wherein the interruption of the current is performed by controlling on / off of a semiconductor active element disposed between the fuel cell unit and the output conversion unit. . 6. The fuel cell device according to claim 1, wherein the resistance of the fuel cell unit is measured by a voltage change when a predetermined current flows through the fuel cell unit. 7. The output converter has a configuration in which a pair of voltage converters are connected in series between the fuel cell unit and the load, and has a capacity for maintaining a load voltage at a predetermined value by discharging. The fuel cell device according to claim 1, wherein the fuel cell device is disposed between the pair of voltage conversion units. 8. The fuel cell device according to claim 1, wherein the capacitance is formed of an electric double layer capacitor. 9. The fuel cell device according to claim 1, wherein the fuel cell unit is controlled so as to be humidified during drying. 10. A fuel cell unit for performing required power generation based on fuel supply, an output monitoring unit for monitoring a power generation output of the fuel cell unit by measuring a resistance component of the fuel cell unit, and the output monitoring. A control unit for generating a control signal for controlling a power generation output from the fuel cell unit in response to a signal from the unit, and a control signal from the control unit disposed between the fuel cell unit and a load. A first output conversion unit that controls the power generation output from the fuel cell unit to be convertible during operation in response to the control signal from the control unit disposed between the fuel cell unit and a load. A fuel cell device comprising: a second output converter that performs a required output when measuring the resistance of the fuel cell unit. 11. The fuel cell device according to claim 10, wherein the output monitoring unit measures the resistance of the fuel cell unit while interrupting a current supplied to a load. 12. The method according to claim 10, wherein the interruption of the current is performed by controlling on / off of a semiconductor active element disposed between the fuel cell unit and the output conversion unit.
The fuel cell device according to claim 1. 13. The fuel cell device according to claim 10, wherein the resistance of the fuel cell unit is measured by a voltage change when a predetermined current is applied to the fuel cell unit. 14. The second output converter has a configuration in which a pair of voltage converters are connected in series between the fuel cell unit and the load, and maintains the load voltage at a predetermined value by discharging. 11. The fuel cell device according to claim 10, wherein the capacity of the fuel cell is disposed between the pair of voltage conversion units. 15. The fuel cell device according to claim 10, wherein said capacitance is formed of an electric double layer capacitor. 16. The fuel cell device according to claim 10, wherein the fuel cell unit is controlled so as to be humidified during drying. 17. A fuel cell unit supplies fuel to the fuel cell unit to generate required electric power, and monitors a power generation output of the fuel cell unit by measuring a resistance component of the fuel cell unit. A control signal for controlling the power generation output from the fuel cell unit is generated according to the monitored result, and the power generation output from the fuel cell unit is controlled to be convertible according to the control signal. An operation method of the fuel cell device. 18. A fuel cell unit supplies fuel to the fuel cell unit to generate required power, and monitors a power generation output of the fuel cell unit by measuring a resistance component of the fuel cell unit. A control signal for controlling a power generation output from the fuel cell unit is generated in accordance with the monitored result, and in operation, the power generation output from the fuel cell unit is controlled to be convertible in accordance with the control signal and the fuel is controlled. A method for operating a fuel cell device, comprising: controlling the output of power from the fuel cell unit so that the output of the fuel cell unit can be converted through a different path from that used during the operation when measuring the resistance of the battery unit. 19. The method according to claim 18, wherein a capacity for maintaining a load voltage at a predetermined value by discharging is provided in the different paths.