JP6633998B2 - Fuel cell system mounted on industrial vehicles - Google Patents

Description

  The present invention relates to a fuel cell system mounted on an industrial vehicle, and more particularly, to a fuel cell system that controls power generated by a fuel cell stack in multiple stages.

  Commercialization of industrial vehicles such as forklifts equipped with a fuel cell system has been promoted. In a general fuel cell system, fluctuations in the generated power cause deterioration of the fuel cell stack.To prevent deterioration of the fuel cell stack, it is necessary to minimize fluctuations in the generated power and generate power at a constant power. preferable.

  2. Description of the Related Art Conventionally, there has been known a fuel cell system in which the generated power of a fuel cell stack is controlled in three predetermined steps without being continuously changed. In such a system, a capacitor is connected in parallel with the load connected to the fuel cell stack, and when the power generated by the fuel cell stack exceeds the required power of the load, surplus power is charged to the capacitor, If the generated power is lower than the required power of the load, the insufficient power is discharged from the capacitor.

  However, in a situation such as climbing a steep slope with a maximum load, even if power is generated with the maximum power of the above three stages, a large amount of power is taken out of the capacitor and the capacitor may be over-discharged. There is. As a countermeasure against such a case, Patent Literature 1 determines a possibility that a capacitor will be over-discharged based on a required power of a load including a traveling motor, a cargo handling motor, and the like. If it is determined that the electric power generated by the fuel cell stack is higher than the maximum electric power described above.

JP 2014-166110 A

  However, in the method of determining the possibility of the capacitor being over-discharged based on the required power of the load as in Patent Literature 1, the possibility of the capacitor being over-discharged in reality is not the situation. May be erroneously determined, and the generated power of the fuel cell stack may be increased beyond the maximum power.

  The present invention has been made in order to solve such a problem, and accurately determines the possibility that a capacitor will be overdischarged, and reduces the power generated by the fuel cell stack from a predetermined maximum power only when it is really necessary. It is an object of the present invention to provide a fuel cell system mounted on an industrial vehicle, which can increase the fuel consumption.

In order to solve the above problems, a fuel cell system mounted on a vehicle according to the present invention includes a fuel cell stack electrically connected to a vehicle load, and an electric connection to the fuel cell stack in parallel with the vehicle load. And a voltage estimating means for estimating an open circuit voltage of the capacitor; and a power generation circuit for generating a predetermined maximum power and a predetermined minimum power based on the open circuit voltage of the capacitor estimated by the voltage estimating means. Control means for switching at a constant power in multiple stages between the power supply and the control means, wherein the control means sets the power generated by the fuel cell stack to a power higher than the maximum power when the capacitor enters a predetermined discharge state. .

  The predetermined discharge condition is that when the fuel cell stack is generating the maximum power or when the open circuit voltage of the capacitor is lower than a predetermined threshold voltage, the voltage drop rate of the open circuit voltage of the capacitor is a predetermined value for a predetermined time. It may be a situation that exceeds the value.

  It further comprises current measuring means for measuring the output current of the capacitor, and the predetermined discharge state is when the fuel cell stack is generating the maximum power, or when the open circuit voltage of the capacitor is lower than a predetermined threshold voltage, There may be a situation where the output current of the capacitor exceeds a predetermined value for a certain period of time.

  The power higher than the maximum power may be determined as the required power of the vehicle load divided by the power generation efficiency of the fuel cell stack.

  ADVANTAGE OF THE INVENTION According to the fuel cell system mounted in the industrial vehicle according to the present invention, the possibility of the capacitor being overdischarged is accurately determined, and the generated power of the fuel cell stack is more than the predetermined maximum power only when really necessary. Can be increased.

FIG. 1 is a diagram showing a configuration of a fuel cell system mounted on an industrial vehicle according to Embodiment 1 of the present invention. FIG. 2 is a diagram showing a state of switching of generated power of a fuel cell stack in a fuel cell system mounted on an industrial vehicle according to Embodiment 1 of the present invention. 6 is a flowchart showing a process of a fuel cell stack mounted in an industrial vehicle according to Embodiment 1 of the present invention in a fuel cell stack output increase mode. FIG. 7 is a diagram showing a configuration of a fuel cell system mounted on an industrial vehicle according to Embodiment 2 of the present invention. 9 is a flowchart showing a process in a fuel cell stack output increase mode in the fuel cell system mounted on the industrial vehicle according to Embodiment 2 of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 shows a configuration of a fuel cell system 1 mounted on an industrial vehicle 100 according to the first embodiment of the present invention. It should be noted that specific examples of the industrial vehicle 100 include a forklift, a towing vehicle, and the like.

  The fuel cell system 1 includes a fuel cell stack 2, a hydrogen tank 3 capable of supplying hydrogen gas, and an air compressor 4 capable of supplying air containing oxygen. Electric energy is generated by causing a chemical reaction in the fuel cell stack 2 with oxygen in the air supplied from the compressor 4. An electromagnetic valve 5 for adjusting the amount of hydrogen gas supplied to the fuel cell stack 2 is provided between the fuel cell stack 2 and the hydrogen tank 3, and the electromagnetic valve 5 and the air compressor 4 It is controlled by a control unit (ECU) 9.

  The output of the fuel cell stack 2 is connected to a vehicle load 7 and an auxiliary device 8 via a DC / DC converter 6, and the DC power generated by the fuel cell stack 2 is supplied to a predetermined voltage by the DC / DC converter 6. After the voltage is lowered to the vehicle load 7 and the auxiliary device 8, it is output.

  The vehicle load 7 includes a traveling motor and a cargo handling motor for driving the axle of the industrial vehicle 100, and the traveling motor and the cargo handling motor constituting the vehicle load 7 are driven by electric power supplied from the fuel cell system 1. As a result, the traveling operation and the cargo handling operation of the industrial vehicle 100 are performed.

  The auxiliary device 8 includes various sensors mounted on the industrial vehicle 100, an electronic control unit (ECU) 9 described later, and the like, and has lower power consumption than the vehicle load 7.

A capacitor 10 is connected to the output of the DC / DC converter 6 in parallel with the vehicle load 7 and the auxiliary device 8. Power obtained by subtracting the electric power consumed in the auxiliary device 8 from the generator power P _G of the fuel cell stack 2 when exceeding the required power P _W of the vehicle load 7, the surplus power is charged in the capacitor 10. On the other hand, when the electric power obtained by subtracting the electric power consumed in the auxiliary device 8 from the generator power P _G of the fuel cell stack 2 is below the required power P _W of the vehicle load 7, power shortage is discharged from the capacitor 10 .

  A voltage estimator 11 is attached to the capacitor 10. The voltage estimator 11 obtains a charge amount of the capacitor 10 by integrating currents input to and output from the capacitor 10, and estimates an open circuit voltage (OCV) of the capacitor 10 based on the charge amount.

Further, the fuel cell system 1 includes an electronic control unit (ECU) 9 configured by a microcomputer. The ECU 9 is supplied to the fuel cell stack 2 by controlling the opening of the solenoid valve 5 and the discharge amount of the air compressor 4 based on the open circuit voltage V _OCV of the capacitor 10 estimated by the voltage estimator 11. adjust the amount of hydrogen and oxygen, thereby controlling the generated power P _G of the fuel cell stack 2.

As described above, in order to prevent deterioration of the fuel cell stack 2 is preferably generated by a constant power while suppressing maximize the variation of the generated power P _G. Therefore, ECU 9 is a generated power _{P G} of the fuel cell stack 2 is controlled minimum power _{P L,} the intermediate power _{P M,} the three stages of the maximum power _{P H.} Here, the maximum power P _H is defined as the sum of the power P _W required by the vehicle load 7 and the power consumed by the auxiliary equipment 8 when the industrial vehicle 100 operates at the maximum high load, and the minimum power P _L the fuel cell stack 2 is defined as power that can be generated minimum value without degradation, intermediate power P _M is defined as a predetermined intermediate value between the maximum power P _H and the minimum power P _L .

The ECU 9 constantly monitors the open circuit voltage V _OCV of the capacitor 10 estimated by the voltage estimator 11, and as shown in FIG. 2, the open circuit voltage V _OCV of the capacitor 10 is set to a predetermined first threshold V _TH1 and a predetermined threshold V _TH1 . during normal lying between 2 threshold _{V TH2,} the generated power _{P G} of the fuel cell stack 2 to the intermediate power _{P M.}

When the ECU 9 detects that the charge amount of the capacitor 10 has decreased due to an increase in the required power _PW of the vehicle load 7 and the like, the open circuit voltage V _OCV has fallen below a predetermined first threshold value V _TH1. , generating power _{P G} switching from the intermediate power _{P M} to the maximum power _{P H,} the open-circuit voltage _{V OCV} is detected that exceeds the first threshold value _{V TH1} rises, the generated electric power _{P G} again intermediate power _{P M} Switch to

Further, ECU 9, when the open circuit voltage _{V OCV} increases the charge amount of the capacitor 10 it is detected that exceeds a predetermined second threshold value _{V TH2,} the minimum power generated power _{P G} from the intermediate power _{P M P L} the switching, the open circuit voltage _{V OCV} detects that falls below the second threshold value _{V TH2} decreases, switching the generated power _{P G} again to the intermediate power _{P M.}

  Next, in the fuel cell system 1 mounted on the industrial vehicle 100 according to the first embodiment, the operation is performed when there is a possibility that the capacitor 10 may be over-discharged, such as when climbing a steep slope with a maximum load. The power increase mode of the fuel cell stack 2 will be described.

  The ECU 9 constantly checks the possibility of the capacitor 10 being over-discharged by repeatedly executing the process shown in FIG. 3 at a predetermined cycle in parallel with the normal power switching control shown in FIG.

Specifically, ECU 9, when the fuel cell stack 2 is generated by the maximum power _{P H} (S101 = YES), the voltage drop rate of the open circuit voltage _{V OCV} of the capacitor 10 that is estimated by the voltage estimator 11 beta If is greater than a predetermined value beta _C over a period of time _T 1 (approximately 0.1 to 0.2 seconds) (S102 = YES, S103 = YES), it is determined that the capacitor 10 may become over-discharged.

As is well known, since there is a correlation between the open circuit voltage V _OCV of the capacitor 10 and the charge amount, the voltage drop rate β of the open circuit voltage V _OCV of the capacitor 10 becomes a predetermined value β _C over a certain time T _1. because situation above means a situation that brought a large amount of power to (despite the fuel cell stack 2 is generated by the maximum power P _H), the vehicle load 7 from the capacitor 10.

The ECU 9 starts the output increasing mode of the fuel cell stack 2 when it is determined that all the conditions of S101 to S103 are satisfied and the capacitor 10 may be overdischarged (S104). In the output increase mode of the fuel cell stack 2, the amount of hydrogen gas and air supplied to the fuel cell stack 2 is further increased than the case of the maximum power P _H, the generated power P _G of the fuel cell stack 2 is maximum power It becomes higher power than P _H.

Specifically, the generated power P _H ′ of the fuel cell stack 2 in the output increase mode is determined by the following equation, where P _{W is} the required power of the vehicle load 7 and η is the power generation efficiency of the fuel cell stack 2.
P _H ′ = P _W / η

The power generation efficiency η of the fuel cell stack 2 is defined as a value obtained by dividing the energy supplied to the vehicle load 7 by the energy of hydrogen consumed at that time. Since this value varies depending on the required power _PW of the vehicle load 7, values at various required powers _PW are measured in advance and stored in the ECU 9. At this time, a margin of several% to several tens% may be provided for the measured value.

It is started and the output increase mode of the fuel cell stack 2 by the generated power P _G is increased to P _{H ',} from the fuel cell stack 2 in parallel with the power supply to the vehicle load 7 performed the charging of the capacitor 10 As a result, the open circuit voltage V _OCV of the capacitor 10 increases. When the open circuit voltage V _OCV of the capacitor 10 exceeds the predetermined threshold voltage V _TH (S105 = YES), and the ECU 9 determines that there is no possibility of overdischarge, the ECU 9 increases the output of the fuel cell stack 2 in the output increasing mode. Is terminated (S106).

As described above, in the fuel cell system 1 is mounted on an industrial vehicle 100 according to the first embodiment of the present invention, when the fuel cell stack 2 is generated by the maximum power P _H, the open-circuit of the capacitor 10 If the voltage drop rate beta voltage V _OCV exceeds a predetermined value beta _C over a period of time T _1, it is determined that there is a possibility that the capacitor 10 is over-discharged, the generated power P _G of the fuel cell stack 2 than the maximum power To a higher power P _H ′. Thus, it is possible to accurately determine the possibility that the capacitor 10 is over-discharged, the generated power P _G of the fuel cell stack 2 only when really needed is increased than the predetermined maximum power P _H P _H ′.

Embodiment 2 FIG.
Next, a fuel cell system 201 mounted on an industrial vehicle 200 according to a second embodiment of the present invention will be described. The detailed description of the same parts as in the first embodiment is omitted.

FIG. 4 shows a configuration of a fuel cell system 201 of an industrial vehicle 200 according to Embodiment 2 of the present invention. As shown in this figure, the fuel cell system 201 includes a current sensor 212 for measuring the output current I of the capacitor 10 in addition to the voltage estimator 11 for estimating the open circuit voltage V _OCV of the capacitor 10.

As shown in FIG. 5, ECU209, when the fuel cell stack 2 is generated by the maximum power _{P H} (S201 = YES), the output current I is constant time of the capacitor 10 to be measured by the current sensor 212 T ₂ when above a predetermined value _{I C} for (0.1 seconds to 0.2 seconds) (S202 = YES, S203 = YES), determines that the capacitor 10 may become over-discharged, the fuel cell stack 2 Is started (S204).

After that, when the open circuit voltage V _OCV of the capacitor 10 exceeds the predetermined threshold voltage V _TH (S205 = YES) and it is determined that there is no possibility of overdischarge, the ECU 9 increases the output of the fuel cell stack 2 in the output increasing mode. Is terminated (S206).

As described above, in the fuel cell system 201 is mounted to the industrial vehicle 200 according to the second embodiment of the present invention, when the fuel cell stack 2 is generated by the maximum power P _H, the output current of the capacitor 10 If I is greater than a predetermined value I _C over a period of time T _2, it is determined that there is a possibility that the capacitor 10 is over-discharged, the generated power P _G of the fuel cell stack 2 to the higher power P _{H 'than} the maximum power I do.

That is, in the first embodiment, the possibility of overdischarge is determined based on the voltage drop rate β of the open circuit voltage _VOCV of the capacitor 10, whereas in the second embodiment, the output of the capacitor 10 is The possibility of overdischarge is determined based on the current I. Even in such construction, it is possible to accurately determine the possibility that the capacitor 10 is over-discharged, the generated power P _G of the fuel cell stack 2 only when really needed than a predetermined maximum power P _H Can also be increased to P _H ′.

Other embodiments.
In the first and second embodiments, the case where the present invention is applied to the fuel cell systems 1 and 201 that controls the power generated by the fuel cell stack 2 in three stages has been described. However, the applicable range of the present invention is as follows. The present invention is not limited to this, and the present invention can be applied to any fuel cell system that controls the generated power of the fuel cell stack in two or more stages.

Further, in S101 of the first and second embodiments, the fuel cell stack 2 is in place to determine whether or not the power generation at the maximum power P _H, the open-circuit voltage V _OCV predetermined threshold voltage V of the capacitor 10 You may make it determine whether it is less than _TH .

In the first embodiment, the possibility of overdischarge is determined based on the voltage drop rate β of the open circuit voltage _VOCV of the capacitor 10, and in the second embodiment, the overdischarge is determined based on the output current I of the capacitor 10. Although the possibility of discharging has been determined, the possibility of overdischarging may be determined based on, for example, the output power of the capacitor 10.

  100,200 industrial vehicle, 1,201 fuel cell system, 2 fuel cell stack, 7 vehicle load, 9,209 ECU (control means), 10 capacitor, 11 voltage estimator (voltage estimating means), 212 current sensor (current measurement means).

Claims (4)

A fuel cell system mounted on an industrial vehicle,
A fuel cell stack electrically connected to the vehicle load;
A capacitor electrically connected to the fuel cell stack in parallel with the vehicle load;
Voltage estimating means for estimating an open circuit voltage of the capacitor;
Control means for switching the generated power of the fuel cell stack between a predetermined maximum power and a predetermined minimum power at a constant power in multiple stages based on the open circuit voltage of the capacitor estimated by the voltage estimating means. Prepared,
The fuel cell system mounted on an industrial vehicle, wherein the control means sets the power generated by the fuel cell stack to a power higher than the maximum power when the capacitor enters a predetermined discharge state.   The predetermined discharge state is a voltage drop rate of the open circuit voltage of the capacitor when the fuel cell stack is generating the maximum power or when the open circuit voltage of the capacitor is lower than a predetermined threshold voltage. 2. The fuel cell system according to claim 1, wherein the fuel cell system exceeds a predetermined value for a predetermined time. A current measuring unit for measuring an output current of the capacitor,
The predetermined discharge condition is that when the fuel cell stack is generating the maximum power, or when the open circuit voltage of the capacitor is lower than a predetermined threshold voltage, the output current of the capacitor is maintained for a predetermined time. The fuel cell system mounted on an industrial vehicle according to claim 1, wherein the fuel cell system is in a situation exceeding a value.   The power higher than the maximum power is determined as a value obtained by dividing the required power of the vehicle load by the power generation efficiency of the fuel cell stack, The power according to any one of claims 1 to 3, wherein Fuel cell system mounted on industrial vehicles.

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