JP2007095355A - Fuel cell system - Google Patents

Abstract

A fuel cell system that can warm up a fuel cell without overheating, and aims to reduce the weight of the system.
At least two or more fuel cells, an AC voltage converter for converting electric power generated in the fuel cell into an AC voltage, temperature detecting means for detecting the temperature of the fuel cell, and the temperature detecting means When the detected temperature of the first fuel cell is equal to or lower than a predetermined temperature, the electric power generated in the fuel cells other than the first fuel cell is guided to the AC voltage converter, and the converted AC voltage is converted into the first fuel. And a control means for applying to the battery.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell system that generates electrical energy through an electrochemical reaction.

  In the fuel cell system, electric energy is obtained by electrochemically reacting a combustion gas such as hydrogen and an oxidizing gas containing oxygen via an electrolyte. Since the fuel cell system has an operating temperature at which power can be generated, when the fuel cell has not reached a temperature at which it can generate power, such as during startup, the fuel cell is heated (warmed up) to quickly generate power. Some are configured to warm up to a possible temperature.

  As a first conventional technique, in a fuel cell system including a plurality of fuel cells, an arbitrary fuel cell is warmed up by a combustor, and electric power generated by the warmed-up fuel cell is supplied to the heater. There is a fuel cell system that warms up other fuel cells. According to this fuel cell system, another fuel cell can be warmed up using electric power obtained from an arbitrary fuel cell warmed up by a combustor (see Patent Document 1).

As a second prior art, there is a fuel cell system that converts a direct current supplied from a battery into an alternating current and applies it to the fuel cell, and heats the ice and solid polymer film inside the fuel cell by dielectric loss. is there. According to this fuel cell system, it is possible to warm up the fuel cell by directly heating the ice or polymer membrane inside the fuel cell by applying an alternating voltage (see Patent Document 2).
JP 2000-294263 A JP 2004-127758 A JP 2001-189164 A JP 2003-51332 A

  However, the prior art has the following problems. Since the first conventional technique uses a heater, the fuel cell may be overheated, and it may take time to warm up to heat a portion other than the portion to be heated. In addition, the second prior art uses an alternating voltage, and thus can prevent overheating of the fuel cell, but requires a battery for warm-up operation. is there.

  The present invention has been made in view of the above-described various problems, and is a fuel cell system that can be efficiently warmed up without overheating the fuel cell, and an object thereof is to reduce the weight of the system.

  The present invention includes at least two or more fuel cells, an AC voltage conversion device that converts electric power generated in the fuel cells into an AC voltage, temperature detection means for detecting the temperature of the fuel cell, and the temperature detection means. When the detected temperature of the first fuel cell is equal to or lower than a predetermined temperature, the electric power generated in the fuel cells other than the first fuel cell is guided to the AC voltage converter, and the converted AC voltage is converted into the first fuel. And a control means for applying to the battery.

  This fuel cell system detects the temperature of a plurality of fuel cells, and with respect to the first fuel cell having a predetermined temperature or less that requires warm-up operation, the power generated in the other fuel cell is converted by the AC voltage converter. Convert to AC voltage and apply. That is, it is possible to warm up by applying an AC voltage to another fuel cell using electric power generated in one of the two or more fuel cells.

  By applying this AC voltage, the electrolyte membrane of the MEA (Membarane Electrode Assembly) constituting the first fuel cell can be directly and efficiently heated, and the fuel cell can be quickly heated to perform normal operation. . Furthermore, since heating is performed with an alternating voltage, the entire MEA can be heated uniformly, and partial overheating can be prevented. Furthermore, since the power generated by the fuel cell itself is used for warming up, a heating device such as a heater or a battery for warming up becomes unnecessary, and the system can be reduced in weight compared to the conventional system. Become.

  The predetermined temperature is a temperature serving as a threshold for determining whether or not warm-up operation is required. For the first fuel cell, a fuel cell to be warmed up among the plurality of fuel cells may be set. For example, a temperature detecting means for detecting the temperature of the fuel cell is provided, and the detected fuel is the lowest. It is desirable that the battery is configured to be heated by application of an alternating voltage as the first fuel cell.

  In the fuel cell system according to the present invention, the control means guides the electric power generated in a fuel cell other than the first fuel cell to an AC voltage converter, and converts the converted AC voltage to the first fuel cell. A first step of applying, a second step of stopping the application of the AC voltage to the first fuel cell, and an AC voltage converted by introducing the power generated in the first fuel cell to an AC voltage converter. It is desirable to repeat the third step of applying a voltage to the fuel cell having the lowest temperature among the fuel cells other than the first fuel cell.

  The first step is a step of warming up the first fuel cell by converting electric power generated in a fuel cell other than the first fuel cell into an alternating voltage and applying it to the first fuel cell. The second step is a step of stopping the application of the AC voltage to the first fuel cell, and is performed when the temperature of the first fuel cell is raised to a temperature at which power generation is possible. The third step is a step of warming up another fuel cell using the electric power generated by the first fuel cell warmed up in the second step. The fuel cell to be warmed up in the third step is preferably a fuel cell having the lowest temperature detected by the temperature detecting means, so that a fuel cell that cannot generate power at a low temperature can be warmed up preferentially and efficiently. .

  In the present invention, by repeatedly performing the first to third steps, other fuel cells can be warmed up using electric power generated by any fuel cell, and heating devices such as heaters and heat insulators are used. Therefore, it is possible to warm up the fuel cell more efficiently without the need for the fuel cell. Further, in the process of repeating the first to third steps, the first fuel cell to be warmed up should be changed as appropriate. For example, before the first step, the temperature of all fuel cells is detected by the temperature detecting means. And a step of setting the fuel cell having the lowest detected temperature as the first fuel cell may be provided. By further including the step of setting the first fuel cell, it is possible to appropriately set a fuel cell that requires warm-up operation, and it is possible to efficiently warm up a plurality of fuel cells.

  Furthermore, the fuel cell system according to the present invention further includes power detection means for detecting the generated power of the fuel cell, and the control means is detected by the power detection means among fuel cells other than the first fuel cell. It is desirable that the electric power generated from the fuel cell having the largest electric power is guided to the AC voltage converter, and the converted AC voltage is applied to the first fuel cell.

With the above configuration, the power of the fuel cell having the largest generated power detected by the power detection means is converted into an alternating voltage, and the first fuel cell is heated by applying the alternating voltage to the first fuel cell. it can. That is, since the other fuel cell is heated using the power of the fuel cell having the largest generated power, the power generation efficiency can be increased, and it is possible to warm up to a temperature at which power can be generated in a shorter time.

  The fuel cell system according to the present invention further includes voltage adjusting means for adjusting the voltage of the fuel cell, and the voltage adjusting means is configured to supply the generated power to the AC voltage conversion device. It is desirable to adjust so that it may become higher than one fuel cell.

  The first fuel cell to be warmed up is desirably lower than the voltage of the fuel cell that supplies the generated power, and in such a voltage relationship, warming up by the generated power can be performed efficiently. The present invention provides a fuel cell in which power generated by the voltage adjusting means is guided to an AC voltage converter, that is, a fuel cell that supplies generated power to a warm-up of another fuel cell, and a fuel cell that is warmed-up. Adjust the voltage of the fuel cell to be warmed down. The voltage adjusting means may be anything that can change the voltage of one fuel cell relative to the other fuel cell. For example, the voltage adjusting means may be configured to adjust the voltage by supplying nitrogen, or to adjust the voltage by consuming current.

  According to the fuel cell system of the present invention, since the other fuel cells are heated by the AC voltage using the generated power of at least one of the plurality of fuel cells, the fuel cell can be efficiently used without overheating. It is possible to warm up and reduce the weight of the fuel cell system.

  Embodiments of a fuel cell system according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a system configuration diagram of a fuel cell system 10 according to an embodiment. This fuel cell system 10 stores first and second fuel cells 1, 2 and hydrogen gas as a fuel gas, and high-pressure hydrogen as a hydrogen supply device for supplying hydrogen gas to the fuel cells 1, 2 Tank 3, air supply device 4 that supplies air to fuel cells 1 and 2, electronic control unit (ECU) 5 that controls various devices, and alternating current that converts power generated by fuel cells 1 and 2 into alternating voltage A voltage converter 6 and temperature sensors 7 and 8 as temperature detecting means for detecting the temperature of the fuel cells 1 and 2 are provided.

  The fuel cells 1 and 2 obtain electric energy by electrochemically reacting hydrogen gas and oxidizing gas via an electrolyte. The fuel cells 1 and 2 are solid polymer electrolyte fuel cells that are frequently used in electric vehicles that run using the fuel cell as a power source.

  The AC voltage conversion device 6 is a device that converts the electric power generated by one of the fuel cells 1 and 2 into an AC voltage, and the converted AC voltage is applied to the fuel cell to be warmed up. The application of electric power and the output voltage are controlled by the ECU 5.

  The temperature sensors 7, 8 detect the temperature of the anode (fuel electrode) off-gas discharged from the fuel cells 1, 2, and the ECU 5 estimates the temperature of the fuel cell based on the detected temperature. The off-gas discharged from the fuel cells 1 and 2 reflects the temperature of the fuel cell, and the fuel cell can be estimated based on the off-gas temperature. The temperature detected by the temperature sensors 7 and 8 is configured to be input to the ECU 5.

  The ECU 5 is configured to receive the temperature, voltage, and power generation amount of the fuel cells 1 and 2, select a fuel cell to be warmed up based on the input value, and convert the power amount into an AC voltage. And the amount of air supplied from the air supply device 4 is controlled. The ECU 5 includes functions of a control unit, a power detection unit, and a voltage adjustment unit according to the present invention.

  Hereinafter, temperature control of the fuel cell in the fuel cell system 10 configured as described above will be described in detail. Various controls described below are routines executed by the ECU 5 and repeated at regular intervals.

  In the temperature control of the fuel cell according to the present embodiment, the generated power of one of the first and second fuel cells 1 and 2 is guided to the AC voltage converter 6, and the AC voltage converter 6 In this control, the converted AC voltage is applied to the other fuel cell to warm up the other fuel cell. FIG. 2 is a flowchart showing temperature control of the fuel cell.

  First, the temperature sensors 7 and 8 detect the temperature FC1 of the first fuel cell 1 and the temperature FC2 of the second fuel cell 2 (step 101). This is to determine whether the fuel cells 1 and 2 need to be warmed up based on the temperature of the fuel cells 1 and 2. The temperatures of the fuel cells 1 and 2 detected by the temperature sensors 7 and 8 are input to the ECU 5.

  The ECU 5 determines whether at least one of the first fuel cell 1 and the second fuel cell 2 needs to be warmed up (step 102). In the present embodiment, it is assumed that the temperature FC1 of the first fuel cell 1 is lower than the temperature FC2 of the second fuel cell 2, and that the first fuel cell 1 needs to be warmed up. The predetermined temperature F0 is a threshold value for determining whether or not the fuel cell needs to be warmed up.

  As a result of the determination in step 102, when both the temperature of the first fuel cell 1 and the second fuel cell 2 are higher than the predetermined temperature F0 and the warm-up operation is not necessary, the process is terminated. On the other hand, if the result of determination in step 102 is that at least one of the fuel cells needs to be warmed up, the temperature FC1 of the first fuel cell is compared with the temperature of the second fuel cell FC2. A fuel cell to be operated is selected (step 103). In the present embodiment, since the temperature FC1 of the first fuel cell 1 is lower than the temperature FC2 of the second fuel cell 2, the first fuel cell 1 is warmed up.

  In order to warm up the first fuel cell 1, it is necessary that the generated power of the second fuel cell 2 be equal to or greater than a certain level, and thus the ECU 5 generates the generated power of the second fuel cell 2. It detects (step 104) and determines whether the said generated electric power is more than predetermined electric power (step 105). This predetermined electric power is a threshold value for determining whether electric power that can warm up the first fuel cell can be generated. When the detected generated power is less than the predetermined power, the ECU 5 performs a process of increasing the generated power of the second fuel cell 2 (step 106), and the generated power of the second fuel cell 2 becomes equal to or higher than the predetermined power. Repeat the process until.

  The above process is repeated, or when it is determined in step 105 that the generated power of the second fuel cell 2 is equal to or higher than the predetermined power, a process of reducing the voltage of the first fuel cell 1 is performed (step 107). . In order to apply an AC voltage to the first fuel cell 1, it is desirable that the voltage of the first fuel cell 1 be lower than the voltage of the second fuel cell 2. Therefore, the process of lowering the voltage of the first fuel cell 1 is performed before applying the AC voltage. Specifically, the air supply from the air supply device 4 to the first fuel cell 1 is blocked, and the voltage of the first fuel cell 1 is lowered.

After the voltage of the first fuel cell 1 is lowered, the electric power generated by the second fuel cell 2 is led to the AC voltage converter 6 and converted into an AC voltage (step 108). Next, the converted AC voltage is applied to the first fuel cell 1 to heat (warm up) the first fuel cell 1 (step 109). The electric power generated by the fuel cell is a DC voltage. The AC voltage can be applied to the first fuel cell 1 by converting this into an AC voltage by the AC voltage converter 6. As a result, the MEA of the fuel cell that is to be heated can be efficiently heated, and the whole can be heated uniformly, thereby preventing overheating.

  After heating the first fuel cell 1 for a predetermined time, the temperature sensor 7 detects the temperature FC1 of the first fuel cell 1 (step 110), and the temperature FC1 of the first fuel cell 1 is higher than the predetermined temperature F0. It is determined again whether it is below (step 111). As a result of the determination in step 110, when the temperature of the first fuel cell 1 is equal to or lower than the predetermined temperature F0, the generated power of the second fuel cell 2 is detected again to warm up the first fuel cell 1. continue.

  The above steps are repeated or, as a result of the determination in step 111, if the temperature FC1 of the first fuel cell 1 is higher than the predetermined temperature F0, the warm-up of the first fuel cell 1 is terminated (step 112). Since the first fuel cell 1 has been warmed up by the above processing, the temperatures of the first fuel cell 1 and the second fuel cell 2 are detected again (step 101).

  Since the first fuel cell 1 is heated to a temperature at which electric power can be generated by warming up, if the temperature FC2 of the second fuel cell 2 is equal to or lower than the predetermined temperature F0, the second fuel cell 1 is warmed up. Do. Thereafter, after a predetermined time has elapsed, the temperatures of the first fuel cell 1 and the second fuel cell 2 are detected (step 101), and the generated power of one fuel cell having a higher temperature is used to detect the other temperature having the lower temperature. The process of warming up the fuel cell is repeated alternately.

  Thus, the present invention can warm up the fuel cell without providing a heating device such as a heater or a battery for warming up by performing the warming up operation using the fuel cell itself, Compared with a conventional fuel cell system, the weight can be reduced. In addition, since the fuel cell is heated by applying an alternating voltage, the MEA to be heated can be efficiently heated, and deformation and deterioration of the MEA due to overheating can be prevented.

  In addition, since the fuel cell system according to the embodiment has two fuel cells, the first fuel cell 1 to be warmed up and the second fuel cell 2 that supplies generated power are set. In the fuel cell system having three or more fuel cells, it is desirable to include a process of appropriately selecting the second fuel cell 2 that supplies the generated power.

  Specifically, for example, in a fuel cell system including three fuel cells, the temperature of the three fuel cells is detected, the first fuel cell to be warmed up is selected, and then the other two fuel cells. The amount of power generation is detected, and the fuel cell with the largest detected power is set as the second fuel cell. That is, in a fuel cell system including a plurality of fuel cells other than the first fuel cell to be warmed up, the first fuel cell is warmed up using the power of the fuel cell with the largest amount of generated power. By comprising in this way, it becomes possible to heat-process more efficiently.

  As described above, according to the fuel cell system of the present invention, the fuel to be warmed up is heated in order to heat the other fuel cells with the AC voltage using the generated power of at least one of the plurality of fuel cells. The fuel cell can be warmed up without overheating by directly heating the MEA of the battery. Further, unlike the conventional fuel cell system, a heater and a battery for heat treatment are not required, and thus the weight of the fuel cell system can be reduced.

1 is a configuration diagram of a fuel cell system according to an embodiment. FIG. It is a flowchart which shows the temperature control of a fuel cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st fuel cell 2 2nd fuel cell 3 High pressure hydrogen tank 4 Air supply device 5 Electronic control unit (ECU)
6 AC voltage converter 7, 8 Temperature sensor

Claims (4)

At least two fuel cells;
An alternating voltage converter for converting electric power generated in the fuel cell into an alternating voltage;
Temperature detecting means for detecting the temperature of the fuel cell;
When the temperature of the first fuel cell detected by the temperature detection means is equal to or lower than a predetermined temperature, the power generated in the fuel cells other than the first fuel cell is led to an AC voltage converter, and the converted AC voltage And a control means for applying to the first fuel cell. The control means directs the electric power generated in a fuel cell other than the first fuel cell to an AC voltage converter, and applies the converted AC voltage to the first fuel cell;
A second step of stopping application of the alternating voltage to the first fuel cell;
A third step of guiding the electric power generated in the first fuel cell to an AC voltage converter and applying the converted AC voltage to a fuel cell having the lowest temperature among fuel cells other than the first fuel cell; The fuel cell system according to claim 1, wherein the fuel cell system is repeatedly performed. Further comprising power detection means for detecting power generated by the fuel cell;
The control means guides the electric power generated from the fuel cell having the largest electric power detected by the electric power detection means among the fuel cells other than the first fuel cell to the AC voltage converter, and the converted AC voltage The fuel cell system according to claim 1, wherein the fuel cell system is applied to the first fuel cell. A voltage adjusting means for adjusting the voltage of the fuel cell;
The voltage adjustment means adjusts the generated power so that the voltage of the fuel cell led to the AC voltage converter is higher than that of the first fuel cell. The fuel cell system described in 1.

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