JP2023146166A - fuel cell system - Google Patents

Abstract

To provide a technique capable of improving a power generation efficiency of a fuel cell in a fuel cell system.SOLUTION: A fuel cell system comprises: a fuel cell; a voltage rising converter; a secondary battery; and a control device. A power generation efficiency map writes a relationship between a net output power and a power generation efficiency. The control device is constructed so that a map updating processing is executed, including: a first processing; a second processing; and a third processing in a predetermined frequency. In the first processing, the relationship between the net output power and the power generation efficiency of the fuel cell is actually measured while changing the net output power of the fuel cell in a range where the secondary battery is discharged in a permission discharge amount or less. In the second processing, the relationship between the net output power and the power generation efficiency of the fuel cell is actually measured while changing the net output power of the fuel cell in a range where the secondary battery is charged in a permission charging amount or less. In the third processing, the power generation efficiency map is updated by using the relationship actually measured in the first processing and the second processing when a predetermined condition is satisfied.SELECTED DRAWING: Figure 3

Description

The technology disclosed herein relates to a fuel cell system.

Patent Document 1 describes a fuel cell system. This fuel cell system stores a fuel cell, a secondary battery connected in parallel to the fuel cell, and a power generation efficiency map of the fuel cell, and based on the required power of the load and the power generation efficiency map, A control device that controls power generation of the fuel cell and charging/discharging of the secondary battery, respectively. The power generation efficiency map describes the relationship between the net output power obtained by subtracting the power consumption of the fuel cell from the power generated by the fuel cell, and the power generation efficiency, which indicates the ratio of the net output power to the generated power. The control device determines the output distribution between the fuel cell and the secondary battery based on past operation history, and supplies the required power from the fuel cell and the secondary battery to the load according to the output distribution.

Japanese Patent Application Publication No. 2012-191845

The power generation efficiency of a fuel cell may differ from its design value depending on the environment in which the fuel cell system is used, individual differences in manufacturing of the fuel cell, deterioration due to use, and the like. Therefore, as in the above-mentioned fuel cell system, when the output distribution between the fuel cell and the secondary battery is determined based on a power generation efficiency map stored in advance, the power generation efficiency is actually maximized in that output distribution. There is a possibility that it will not happen.

In view of the above circumstances, this specification provides a technique for improving power generation efficiency of a fuel cell in a fuel cell system.

The technology disclosed herein is embodied in a fuel cell system that supplies power to a load. This fuel cell system includes a fuel cell, a boost converter that is connected between the fuel cell and the load and boosts the power supplied from the fuel cell, and is connected to the fuel cell via the boost converter. and stores a power generation efficiency map of a secondary battery connected in parallel with the boost converter and the fuel cell with respect to the load, and based on the power required by the load and the power generation efficiency map, A control device that controls power generation of the fuel cell and charging/discharging of the secondary battery, respectively. The power generation efficiency map describes the relationship between the net output power obtained by subtracting the power consumption of the fuel cell from the power generated by the fuel cell, and the power generation efficiency that indicates the ratio of the net output power to the generated power. The control device is configured to execute a map update process for updating the power generation efficiency map at a predetermined frequency.

The map update process includes a first process, a second process, and a third process. In the first process, when the remaining charge of the secondary battery is at least a first predetermined value and the allowable discharge power of the secondary battery is at least a second predetermined value, the fuel cell and the secondary battery are When supplying the required power from to the load, the net output power of the fuel cell is changed while the net output power of the fuel cell is varied within a range in which the secondary battery discharges at or below the allowable discharge power. The relationship between the power generation efficiency and the power generation efficiency is actually measured. In the second process, when the remaining charge amount of the secondary battery is less than or equal to a third predetermined value and the allowable charging power of the secondary battery is greater than or equal to a fourth predetermined value, the fuel cell and the secondary battery are When supplying the required power from the battery to the load, the net output power of the fuel cell is changed within a range in which the secondary battery is charged at less than the allowable charging power, and the net output power of the fuel cell is changed. The relationship between the output power and the power generation efficiency is actually measured. In the third process, when a predetermined condition is satisfied, the power generation efficiency map stored in the control device is updated using the relationship actually measured in the first process or the second process.

According to the above configuration, map update processing for updating the power generation efficiency map is executed at a predetermined frequency while the fuel cell system is being used. In the map update process, when supplying required power from the fuel cell and the secondary battery to the load, the net output power of the fuel cell is intentionally changed without being bound by the power generation efficiency map. Then, by actually measuring the power generation efficiency at each time while changing the net output power of the fuel cell, we broadly reconfirm the actual relationship between the net output power and power generation efficiency of current fuel cells. Specifically, when the remaining charge of the secondary battery is equal to or higher than the first predetermined value and the allowable discharge power of the secondary battery is equal to or higher than the second predetermined value, the first process is to discharge the discharge power from the secondary battery. The net output power of the fuel cell is changed within a range in which the discharge power is less than or equal to the allowable discharge power. That is, in the first process, since the secondary battery has discharge power, the net output power of the fuel cell is changed while discharging the portion that is insufficient for the required power from the secondary battery. On the other hand, when the remaining charge amount of the secondary battery is less than or equal to the third predetermined value and the allowable charging power of the secondary battery is greater than or equal to the fourth predetermined value, as a second process, the secondary battery is Varying the net output power of the fuel cell to the extent that it is charged below the charging power. That is, in the second process, the net output power of the fuel cell is changed while the secondary battery charges the portion that is excessive with respect to the required power because the secondary battery has a surplus power to be charged. According to such a configuration, the net output power of the fuel cell can be changed over a relatively wide range while supplying the required power from the fuel cell and the secondary battery to the load.

In the first process and the second process, the relationship between the net output power of the fuel cell and the power generation efficiency is actually measured while changing the net output power of the fuel cell. Then, when a predetermined condition is satisfied, as a third process, the power generation efficiency map stored in the control device is updated using the relationship between the actually measured net output power and power generation efficiency. The relationship between the actually measured net output power of a fuel cell and power generation efficiency reflects the environment in which the fuel cell system is used, the influence of individual differences in the manufacturing of fuel cells, deterioration due to use, etc. Therefore, by updating the power generation efficiency map stored in the control device using this relationship, the accuracy of the power generation efficiency map can be improved. Thereby, in the fuel cell system, it is possible to determine the net output power of the fuel cell while optimizing the power generation efficiency with respect to the power required by the load that changes in various ways.

1 is a diagram schematically showing the configuration of a fuel cell system 10 according to an example. A diagram showing an example of a power generation efficiency map EM that describes the relationship between the net output power PP obtained by subtracting the power consumption of the fuel cell 12 from the power generated by the fuel cell 12 and the power generation efficiency indicating the ratio of the net output power PP to the generated power. . FIG. 3 is a flow diagram showing an example of map update processing executed by the control device 18. FIG. 4 is a diagram for explaining the processing of step S16 and step S20 in the map update processing shown in FIG. 3. FIG.

In one embodiment of the present technology, the predetermined conditions include that the auxiliary equipment of the fuel cell is not operated for purposes other than power generation, that the temperature is within a predetermined range, and that the power generated by the fuel cell suddenly changes. It may also include at least one of the following. According to such a configuration, it is possible to avoid updating the power generation efficiency map based on the power generation efficiency actually measured in an abnormal state.

The fuel cell system 10 will be described with reference to the drawings. The fuel cell system 10 of this embodiment is installed in a fuel cell vehicle (for example, a car, a bus, a truck, a train), a stationary fuel cell device, or the like. Note that the fuel cell system 10 may be mounted on various types of moving bodies (for example, ships and airplanes) other than vehicles.

As shown in FIG. 1, the fuel cell system 10 includes a fuel cell 12. The fuel cell 12 has a stack structure in which a plurality of fuel cells are stacked. The fuel cell 12 generates electricity by causing a chemical reaction between fuel gas and oxidizing gas within a plurality of fuel cells. The fuel cell system 10 of this embodiment uses hydrogen gas as the fuel gas and air as the oxidizing gas. That is, in this embodiment, hydrogen gas is an example of a fuel gas, and air is an example of an oxidizing gas.

As shown in FIG. 1, the fuel cell system 10 further includes a compressor 14, a hydrogen supply valve 16, and a control device 18. The compressor 14 compresses air taken in from the outside and supplies it to the fuel cell 12. The hydrogen supply valve 16 is provided between a hydrogen tank (not shown) connected to the fuel cell system 10 and the fuel cell 12, and is configured to adjust the amount of hydrogen gas supplied from the hydrogen tank to the fuel cell 12. I can do it. The control device 18 is a computer device including a processor, memory, and the like. The control device 18 is communicatively connected to the fuel cell 12, the compressor 14, and the hydrogen supply valve 16, and can control and monitor their operations. For example, controller 18 can control compressor 14 to adjust the amount of air supplied to fuel cell 12 . Similarly, the control device 18 can control the hydrogen supply valve 16 to adjust the amount of hydrogen gas supplied from the hydrogen tank to the fuel cell 12.

The air and hydrogen gas that have passed through the fuel cell 12 are discharged from the fuel cell 12 to the outside. In this case, the gas discharged from the fuel cell 12 to the outside may contain unreacted hydrogen gas. Therefore, the fuel cell system 10 may further include a circulation path (not shown) so that unreacted hydrogen gas can be circulated to the fuel cell 12. Note that the compressor 14 is an example of a device that supplies air to the fuel cell 12. The hydrogen tank and hydrogen supply valve 16 are examples of equipment that supplies hydrogen to the fuel cell 12. Although not particularly limited, the fuel cell system 10 may further include a cooling system (not shown) that circulates cooling water through the fuel cell 12 to cool it.

As shown in FIG. 1, fuel cell system 10 further includes a boost converter 20 and a secondary battery 22. Boost converter 20 is connected between fuel cell 12 and external load 100 and can boost the power supplied from fuel cell 12 and supply it to load 100 . The secondary battery 22 is, for example, a lithium ion battery or a nickel metal hydride battery, and includes a plurality of secondary battery cells. The secondary battery 22 is connected to the fuel cell 12 via the boost converter 20, and is connected in parallel with the boost converter 20 to the load 100. The secondary battery 22 is communicably connected to the control device 18 , and the control device 18 controls the remaining state of charge (hereinafter referred to as SOC) of the secondary battery 22 and the state of charge of the secondary battery 22 . Allowable discharge power Wout and allowable charge power Win can be monitored. Control device 18 is also communicably connected to boost converter 20 and can control the output voltage of boost converter 20 according to requested power TP from load 100. By controlling the output voltage of the boost converter 20, the control device 18 can supply the discharge power DP from the secondary battery 22 to the load 100 while supplying the power supplied from the fuel cell 12 to the load 100. . The control device 18 can also charge the secondary battery 22 by supplying a portion of the supplied power to the secondary battery 22 while supplying the power supplied from the fuel cell 12 to the load 100.

Regarding the above point, the control device 18 stores the power generation efficiency map EM of the fuel cell 12, and based on the power request TP of the load 100 and the power generation efficiency map EM, the control device 18 determines the power generation of the fuel cell 12 and control the charging and discharging of each. As shown in FIG. 2, the power generation efficiency map EM shows the net output power PP obtained by subtracting the power consumption of the fuel cell 12 from the power generated by the fuel cell 12, and the power generation efficiency (hereinafter referred to as (sometimes simply referred to as "power generation efficiency"). For example, as shown in FIG. 2, it is assumed that the requested power TP from the load 100 is a value TP1. In this case, the control device 18 selects a selection range of the net output power PP to be allocated to the fuel cell 12 (i.e., from the lower limit LP to the upper limit UP) based on the allowable discharge power Wout and the allowable charge power Win of the secondary battery 22. range). The lower limit value LP of the selected range is the value obtained by subtracting the allowable discharge power Wout from the value TP1 of the required power TP, and the upper limit value UP of the selected range is the value obtained by adding the allowable charging power Win to the value TP1 of the required power TP. This is the value. The control device 18 determines a value PP1 of the net output power PP that maximizes the power generation efficiency within the determined selection range. In this example, since the value PP1 of the net output power PP is lower than the value TP1 of the required power TP of the load 100, the value TP1 of the required power TP of the load 100 and the value PP1 of the net output power PP of the fuel cell 12 are different. The difference value DP1 is supplied to the load 100 as the discharge power DP from the secondary battery 22.

Next, the map update process executed by the control device 18 will be described with reference to FIGS. 3 and 4. In this map update process, the power generation efficiency map EM stored in the control device 18 is updated. The control device 18 is configured to increment a counter value when the fuel cell system 10 starts operating due to a user's operation or the like. As a result, the counter value increases by one. The counter value here is a value that is updated every trip from the start of operation of the fuel cell system 10 to the end of operation, and corresponds to the number of times the fuel cell system 10 is operated. Note that after this counter value reaches a predetermined number of times (that is, YES in step S10, which will be described later), the counter value is reset to zero at the next time the operation of the fuel cell system 10 is started.

As shown in FIG. 3, the control device 18 determines whether the counter value has reached a predetermined number of times (step S10). If NO in step S10, the control device 18 controls the fuel cell 12 so that the power generation efficiency of the fuel cell 12 is maximized based on the required power TP of the load 100 and the power generation efficiency map EM, as described above. Determine the net output power PP. Then, the power generation of the fuel cell 12 and the charging or discharging of the secondary battery 22 are controlled so that the fuel cell 12 outputs its net output power PP (step S12). On the other hand, if YES in step S10, the control device 18 executes the process in step S14. As a result, the process of step S14 (and related processes) is executed at a predetermined frequency (that is, each time the counter value reaches a predetermined number of times).

Next, the control device 18 determines whether the SOC of the secondary battery 22 is at least a first predetermined value and the allowable discharge power Wout of the secondary battery 22 is at least a second predetermined value (step S14 ). The allowable discharge power Wout of the secondary battery 22 here is a value determined as the maximum discharge amount that the secondary battery 22 can allow. Therefore, YES in step S14 means that the secondary battery 22 has a surplus capacity for discharging. Note that, although not particularly limited, each of the first predetermined value and the second predetermined value may be a value calculated by simulation or the like, or may be a value calculated experimentally.

If YES in step S14, the control device 18, when supplying the requested power TP from the fuel cell 12 and the secondary battery 22 to the load 100, uses the fuel within the range where the secondary battery 22 discharges at or below the allowable discharge power Wout. While changing the net output power PP of the battery 12, the relationship between the net output power PP of the fuel cell 12 and power generation efficiency is actually measured (step S16). For example, as shown in FIG. 4, it is assumed that the requested power TP from the load 100 is a value TP2. When the discharge power DP from the secondary battery 22 is a value DP2 that is less than or equal to the allowable discharge power Wout, the value PP2 of the difference obtained by subtracting the discharge power value DP2 from the value TP2 of the required power TP by the load 100 is The net output power PP from . That is, the net output power PP of the fuel cell 12 is changed by supplementing the power insufficient with respect to the required power TP from the load 100 with the discharge power DP from the secondary battery 22. In this way, in step S16, the electric power supplied to the load 100 from each of the fuel cell 12 and the secondary battery 22 is determined without being bound by the power generation efficiency map EM. As an example, the control device 18 causes the net output power PP from the fuel cell 12 to gradually increase from the low output side to the high output side within a range in which the secondary battery 22 discharges at or below the allowable discharge power Wout. The operating point of the fuel cell 12 is changed so as to.

If NO in step S14, the control device 18 determines whether the SOC of the secondary battery 22 is less than or equal to a third predetermined value and the allowable charging power Win of the secondary battery 22 is greater than or equal to a fourth predetermined value. (Step S18). The allowable charging power Win of the secondary battery 22 here is a value determined as the maximum charge amount that the secondary battery 22 can allow. Therefore, YES in step S18 means that the secondary battery 22 has remaining power to be charged. Note that, although not particularly limited, each of the third predetermined value and the fourth predetermined value may be a value calculated by simulation or the like, or may be a value calculated experimentally. Although this is an example, a value smaller than the first predetermined value is adopted as the third predetermined value.

If YES in step S18, the control device 18 controls, when supplying the requested power TP from the fuel cell 12 and the secondary battery 22 to the load 100, the secondary battery 22 is charged within the range where the secondary battery 22 is charged at less than the allowable charging power Win. While changing the net output power PP of the fuel cell 12, the relationship between the net output power PP of the fuel cell 12 and power generation efficiency is actually measured (step S20). Again, as shown in FIG. 4, it is assumed that, for example, the requested power TP from the load 100 is the value TP2. When the charging power CP to the secondary battery 22 is a value CP1 that is less than or equal to the allowable charging power Win, the net power from the fuel cell 12 is the sum of the charging power value CP1 and the value TP2 of the required power TP by the load 100. The output power PP becomes the value PP3. That is, the net output power PP of the fuel cell 12 is changed by using the power that is excessive with respect to the required power TP from the load 100 as the charging power CP of the secondary battery 22 . In this way, in step S20, as in step S16 described above, the power to be supplied from the fuel cell 12 to each of the load 100 and the secondary battery 22 is determined without being bound by the power generation efficiency map EM. As an example, the control device 18 causes the net output power PP of the fuel cell 12 to gradually decrease from a high output side to a low output side within a range where the secondary battery 22 is charged with less than the allowable charging power Win. Thus, the operating point of the fuel cell 12 is changed. If NO in step S18, the control device 18 moves to step S12.

After executing the processes of step S16 and step S20, the control device 18 determines whether a predetermined condition is satisfied (step S22). The predetermined conditions here include that the auxiliary equipment of the fuel cell 12 is not operated for purposes other than power generation, that the temperature is within a predetermined range, and that the power generated by the fuel cell 12 (i.e., 12) is not at a sudden change in timing. However, the predetermined conditions do not need to include all of these conditions, but only need to include at least one of these conditions. Note that the control device 18 of this embodiment is configured to be able to acquire the power consumption of the auxiliary equipment of the fuel cell 12. At this time, the control device 18 may be electrically connected to the auxiliary equipment of the fuel cell 12, or may be communicably connected via a CAN (Controller Area Network) or the like.

If YES in step S22, the control device 18 updates the stored power generation efficiency map EM using the relationship actually measured in the process of step S16 or step S20 (step S24). Thereby, it is possible to avoid updating the power generation efficiency map EM with the power generation efficiency actually measured in an abnormal state.

Next, the control device 18 determines whether the termination condition is satisfied (step S26). The termination condition here includes, for example, that the fuel cell system 10 has completed its operation. If NO in step S26, the control device 18 returns to the process of step S10. On the other hand, if YES in step S26, the control device 18 ends the map update process shown in FIG. 3.

According to the above configuration, the map update process for updating the power generation efficiency map EM is executed at a predetermined frequency while the fuel cell system 10 is being used. In the map update process, when supplying the required power TP from the fuel cell 12 and the secondary battery 22 to the load 100, the net output power PP of the fuel cell 12 is intentionally changed without being bound by the power generation efficiency map EM. . Then, by actually measuring the power generation efficiency at each time while changing the net output power PP of the fuel cell 12, the actual relationship between the current net output power PP and power generation efficiency of the fuel cell 12 will be widely reconfirmed. Specifically, when the remaining charge amount of the secondary battery 22 is equal to or greater than the first predetermined value and the allowable discharge power Wout of the secondary battery 22 is equal to or greater than the second predetermined value, as a first process, the secondary battery 22 The net output power PP of the fuel cell 12 is changed within a range in which the discharge power DP from the fuel cell 12 is equal to or less than the allowable discharge power Wout (step S16). That is, in the first process, the net output power PP of the fuel cell 12 is changed while the secondary battery 22 is discharging the portion that is insufficient for the required power TP, since the secondary battery 22 has a surplus power for discharging. let On the other hand, when the remaining charge amount of the secondary battery 22 is less than or equal to the third predetermined value and the allowable charging power Win of the secondary battery 22 is greater than or equal to the fourth predetermined value, the secondary The net output power PP of the fuel cell 12 is changed within the range in which the battery 22 is charged with less than the allowable charging power Win (step S20). That is, in the second process, since the secondary battery 22 has a surplus power to be charged, the net output power PP of the fuel cell 12 is charged while the secondary battery 22 charges the excess amount with respect to the required power TP. change. According to such a configuration, the net output power PP of the fuel cell 12 can be changed over a relatively wide range while supplying the required power TP from the fuel cell 12 and the secondary battery 22 to the load 100.

In the first process and the second process, the relationship between the net output power PP of the fuel cell 12 and the power generation efficiency is actually measured while changing the net output power PP of the fuel cell 12 (steps S16, S20). Then, when a predetermined condition is satisfied, as a third process, the power generation efficiency map EM stored in the control device 18 is updated using the relationship between the actually measured net output power PP and the power generation efficiency ( Step S24). The relationship between the measured net output power PP of the fuel cell 12 and the power generation efficiency reflects the environment in which the fuel cell system 10 is used, individual differences in manufacturing of the fuel cells 12, deterioration due to use, etc. has been done. Therefore, by updating the power generation efficiency map EM stored in the control device 18 using this relationship, the accuracy of the power generation efficiency map EM can be improved. Thereby, in the fuel cell system 10, the net output power PP of the fuel cell 12 can be determined while optimizing the power generation efficiency with respect to the variously changing power demands TP of the load 100.

Although several specific examples have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The techniques described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical utility alone or in combination.

10: Fuel cell system 12: Fuel cell 14: Compressor 16: Hydrogen supply valve 18: Control device 20: Boost converter 22: Secondary battery 100: Load CP: Charging power DP: Discharging power EM: Power generation efficiency map LP: Lower limit value PP: Net output power TP: Required power UP: Upper limit Win: Allowable charging power Wout: Allowable discharging power

Claims (2)

A fuel cell system that supplies power to a load,
fuel cell and
a boost converter connected between the fuel cell and the load and boosting the power supplied from the fuel cell;
a secondary battery connected to the fuel cell via the boost converter and connected in parallel to the boost converter with respect to the load;
a control device that stores a power generation efficiency map of the fuel cell, and controls power generation of the fuel cell and charging/discharging of the secondary battery, respectively, based on the power required by the load and the power generation efficiency map;
Equipped with
The power generation efficiency map describes the relationship between the net output power obtained by subtracting the power consumption of the fuel cell from the power generated by the fuel cell, and the power generation efficiency that indicates the ratio of the net output power to the generated power,
The control device is configured to execute a map update process for updating the power generation efficiency map at a predetermined frequency,
The map update process is
When the remaining charge of the secondary battery is at least a first predetermined value and the allowable discharge power of the secondary battery is at least a second predetermined value, the request is made from the fuel cell and the secondary battery to the load. When supplying power, while changing the net output power of the fuel cell within a range in which the secondary battery discharges at or below the allowable discharge power, the net output power of the fuel cell and the power generation efficiency are adjusted. a first process of actually measuring the relationship;
When the remaining charge amount of the secondary battery is less than or equal to a third predetermined value and the allowable charging power of the secondary battery is greater than or equal to a fourth predetermined value, the charge from the fuel cell and the secondary battery to the load is When supplying the requested power, the net output power of the fuel cell is varied within a range in which the secondary battery is charged at less than the allowable charging power, and the net output power of the fuel cell and the power generation efficiency are changed. a second process of actually measuring the relationship between
and a third process of updating the power generation efficiency map stored in the control device using the relationship actually measured in the first process or the second process when a predetermined condition is satisfied. , fuel cell system. The predetermined conditions include that the auxiliary equipment of the fuel cell is not operated for purposes other than power generation, that the temperature is within a predetermined range, and that the generated power of the fuel cell is not at a timing when there is a sudden change. The fuel cell system according to claim 1, comprising at least one of the following.

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