Output control method

Abstract

To inhibit operation of a fuel battery system from being obstructed by output voltage reduction of a secondary battery in the fuel battery system.SOLUTION: Provided is an output control method for controlling a fuel battery system for supplying power to a load. The fuel battery system comprises a fuel battery, a converter connected between the fuel battery and the load to boost supply power from the fuel battery, a secondary battery connected to the fuel battery via the converter in parallel with the load, and an auxiliary machine that is connected to the fuel battery via the converter and connected to the secondary battery and is driven when the power is supplied from the secondary battery. The output control method includes a step of identifying use permission power for inhibiting output voltage of the secondary battery from becoming equal to or lower than a predetermined threshold when a predetermined restriction condition related to a driven situation of the auxiliary machine is established and a step of executing restriction control for controlling output power of the secondary battery depending on the use permission power.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an output control method. [Background technology]

[0002] Conventionally, there is known a fuel cell system that includes a fuel cell and a secondary battery, and the secondary battery is connected to a drive motor without a converter (for example, Patent Document 1). The electric power generated in the fuel cell system is supplied to the drive motor as well as to auxiliary equipment for operating the fuel cell system. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-146166 Summary of the Invention [Problem to be solved by the invention]

[0004] In such a system, when the output power from the secondary battery is large, the voltage of the secondary battery may drop, which may result in a drop in the output of the fuel cell system, such as a drop in the output of the auxiliary equipment required for fuel cell operation. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to one aspect of the present disclosure, there is provided an output control method for controlling a fuel cell system that supplies power to a load, the fuel cell system including a fuel cell, a converter connected between the fuel cell and the load and configured to boost the power supplied from the fuel cell, a secondary battery connected in parallel to the load via the converter to the fuel cell, and an accessory connected to the fuel cell via the converter and connected to the secondary battery to be driven by power supplied from the secondary battery, the output control method including the steps of: identifying a permitted power level at which the output voltage of the secondary battery does not fall below a predetermined threshold when a predetermined limiting condition related to the operating state of the accessory is satisfied; and executing limiting control to limit the output power of the secondary battery in accordance with the permitted power level. According to this form of output control method, when the restriction condition is met, the permitted power that will not cause the secondary battery's output voltage to fall below a predetermined threshold is identified, and restriction control is performed to control the output power of the secondary battery in accordance with the permitted power.This prevents the output voltage of the secondary battery from falling below a predetermined threshold and causing the output of the auxiliary equipment to decrease, and prevents the output of the fuel cell system from decreasing. (2) In the above embodiment, even if the restriction condition is met, the restriction control may not be executed if a predetermined restriction relaxation condition is met. According to this form of output control method, even if the restriction condition is met, the restriction control is not executed if a predetermined restriction relaxation condition is met, thereby preventing frequent switching between the restriction control and normal control and causing the operation of the fuel cell system to become unstable. (3) In the above embodiment, the restriction condition may include a condition that the fuel cell is generating power and the power required by the auxiliary device is equal to or greater than a predetermined threshold. According to this form of output control method, the restriction conditions include the condition that the fuel cell is generating electricity and the power required by the auxiliary equipment is equal to or greater than a predetermined threshold, so that it is possible to prevent a decrease in the output of the fuel cell system due to an increase in the power required by the auxiliary equipment. (4) In the above embodiment, the auxiliary equipment may include a cooling medium pump that supplies a cooling medium to the fuel cell, and the restriction relaxation condition may include at least one of the following conditions: the time during which the output voltage of the secondary battery becomes equal to or lower than a predetermined threshold due to an increase in the output power of the secondary battery is equal to or lower than a predetermined threshold time; the temperature of the auxiliary equipment is equal to or lower than a predetermined auxiliary equipment threshold temperature; and the temperature of the cooling medium supplied by the cooling medium pump is equal to or lower than a predetermined refrigerant threshold temperature. According to this form of output control method, limit control is not executed when at least one of the following conditions is met: the time during which the output voltage of the secondary battery falls below a predetermined threshold due to an increase in the output power of the secondary battery is below a predetermined threshold time; the temperature of the auxiliary equipment is below a predetermined auxiliary equipment threshold temperature; and the temperature of the cooling medium supplied by the cooling medium pump is below a predetermined refrigerant threshold temperature.Therefore, in such cases, frequent switching between limit control and normal control can be prevented, which would cause the operation of the fuel cell system to become unstable. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is an explanatory diagram showing an outline of a fuel cell system according to an embodiment of the present invention; [Figure 2] 3 is a flowchart showing the procedure of an output control method according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. Implementation: A-1. System Configuration: The fuel cell system 100 of this embodiment is mounted on a fuel cell vehicle, such as an automobile, bus, truck, etc. The fuel cell system 100 may also be mounted on various mobile bodies other than a vehicle, such as a train, ship, or airplane, or on a stationary fuel cell device independent of a power grid.

[0009] Fig. 1 is an explanatory diagram showing an outline of a fuel cell system 100 of this embodiment. As shown in Fig. 1, the fuel cell system 100 includes a fuel cell 10, a converter 20, a drive motor 30, a secondary battery 40, an accessory 50, and a control device 60. The control device 60 is configured to be able to communicate with the fuel cell 10, the converter 20, the drive motor 30, the secondary battery 40, and the accessory 50.

[0010] The fuel cell 10 has a stack structure in which multiple fuel cell cells are stacked. The fuel cell 10 generates electricity by chemically reacting fuel gas and oxidizing gas within the multiple fuel cell cells. In the fuel cell system 100 of this embodiment, hydrogen gas is used as the fuel gas and air is used as the oxidizing gas. Note that FIG. 1 does not show a fuel gas supply pipe for supplying fuel gas, an oxidizing gas supply pipe for supplying oxidizing gas, or a cooling water circulation pipe for circulating cooling water as a cooling medium to cool the fuel cell 10.

[0011] The converter 20 is connected between the fuel cell 10 and the drive motor 30, and boosts the power supplied from the fuel cell 10 before supplying it to the drive motor 30, the secondary battery 40, and the accessories 50. The drive motor 30 is a motor for driving a vehicle equipped with the fuel cell system 100. The drive motor 30 corresponds to the "load" in this disclosure.

[0012] The secondary battery 40 is, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery. The secondary battery 40 is connected to the fuel cell 10 via the converter 20, and is connected in parallel with the converter 20 to the drive motor 30. The secondary battery 40 functions as a power source for driving the drive motor 30 and the accessories 50. The secondary battery 40 is charged and discharged according to the power required by the drive motor 30 and the accessories 50 and the amount of power generated by the fuel cell 10. The charging and discharging of the secondary battery 40 is controlled by the control device 60 controlling the output voltage of the converter 20.

[0013] The accessories 50 are devices disposed in various parts of the fuel cell system 100. In this embodiment, the fuel cell system 100 includes a compressor 51 and a water pump 52 as the accessories 50. Note that the accessories 50 included in the fuel cell system 100 are not limited to those described above, and may include various other devices such as a hydrogen on-off valve that is installed in a fuel gas supply pipe to control the amount of fuel gas supplied, or a radiator that is installed in a coolant circulation pipe to cool the coolant.

[0014] The compressor 51 is installed in the oxidizing gas supply pipe and supplies air to the fuel cell 10. The compressor 51 is controlled by the control device 60 to adjust the amount of air supplied to the fuel cell 10. In this embodiment, the compressor 51 is driven by power supplied from at least one of the fuel cell 10 and the secondary battery 40. The compressor 51 also has a temperature sensor (not shown) that outputs the temperature of the compressor 51 body to the control device 60.

[0015] The water pump 52 is installed in the above-mentioned cooling water circulation pipe and supplies cooling water to the fuel cell 10. The water pump 52, which supplies cooling water as a cooling medium, corresponds to the "coolant pump" in this disclosure. The cooling medium supplied to the fuel cell 10 is not limited to water, and may be antifreeze water such as ethylene glycol, air, insulating oil, etc. The water pump 52 is controlled by the control device 60 to adjust the amount of cooling water supplied to the fuel cell 10. In this embodiment, the water pump 52 is driven by power supplied from at least one of the fuel cell 10 and the secondary battery 40. The water pump 52 also has a temperature sensor (not shown) that outputs the body temperature of the water pump 52 and the temperature of the cooling water supplied by the water pump 52 to the control device 60.

[0016] The control device 60 controls the fuel cell system 100. The control device 60 is configured as a computer having a CPU 61, a ROM 62, and a RAM 63. The control device 60 functions as an acquisition unit 71 and an output control unit 72 by loading a program stored in advance in the ROM 62 into the RAM 63 and executing it. The control device 60 also has functional units that execute various controls related to the operation of the above-mentioned fuel cell system 100, but in FIG. 1, only the functional units related to the execution of an output control method described below are shown, and the other functional units are not shown.

[0017] The acquisition unit 71 acquires accessory drive information. "Accessory drive information" refers to information related to the drive of the accessory 50. In this embodiment, the acquisition unit 71 acquires information as accessory drive information including the required power of each of the compressor 51 and the water pump 52, the body temperatures of the compressor 51 and the water pump 52, and the temperature of the coolant supplied by the water pump 52. The required power of each of the compressor 51 and the water pump 52 is determined, for example, according to the required power generation amount of the fuel cell 10 calculated according to the required output of the drive motor 30.

[0018] The output control unit 72 executes an output control method, which will be described later, and controls the output power of the fuel cell system 100 in accordance with the acquired accessory drive information.

[0019] A-2. Output control method: 2 is a flowchart showing the steps of the output control method of this embodiment. The output control method is started when the fuel cell system 100 starts operating, and is repeatedly executed while the fuel cell system 100 is operating.

[0020] In step S10, the acquisition unit 71 acquires the above-mentioned accessory drive information.

[0021] In step S20, the output control unit 72 determines whether or not the limiting conditions are met based on the acquired accessory drive information. In this embodiment, the output control unit 72 determines, as the limiting conditions, whether or not the fuel cell 10 is generating power and the power required by the accessory 50 is equal to or greater than a predetermined threshold.

[0022] If the power demand from the auxiliary device 50 is high and the state in which the secondary battery 40 is rapidly discharged continues, an imbalance in the ion concentration occurs in the electrolyte in the secondary battery 40, causing a decrease in cell performance and a drop in the output voltage of the secondary battery 40. This causes a drop in the output voltage of the entire fuel cell system 100, an increase in the drive current in the auxiliary device 50, causing the auxiliary device 50 to heat up, and the operation of the auxiliary device 50 may be restricted to prevent the auxiliary device 50 from overheating. This interferes with the operation of the fuel cell system 100, and there is a risk that the fuel cell system 100 may not be able to continue operating.

[0023] In order to avoid such a situation, the limiting control described below is executed. In the fuel cell system 100 of this embodiment, the above-mentioned limiting conditions are set in advance as conditions indicating a situation in which such limiting control should be executed, and in step S20, the output control unit 72 determines whether or not such limiting conditions are met.

[0024] If it is determined that the limiting condition is not met (step S20: No), in step S60, the output control unit 72 performs normal control without performing the limiting control described below. In normal control, the output control unit 72 controls the output voltage of the converter 20 so as to maximize the power generation efficiency of the fuel cell 10, for example, according to the power required by the accessories 50 and the drive motor 30. After step S60 is completed, the above-mentioned step S10 is executed again.

[0025] If it is determined that the restriction condition is met (step S20: Yes), in step S30, the output control unit 72 determines whether or not the restriction easing condition is met. The "restriction easing condition" is set in advance as a condition indicating that even if the above-mentioned restriction condition is met, it is not necessary to immediately execute restriction control. In this embodiment, as the restriction easing condition, it is determined whether or not all of the following conditions (1) to (3) are met. (1) The time during which the output voltage of the secondary battery becomes equal to or lower than a predetermined threshold due to an increase in the output power of the secondary battery is equal to or shorter than a predetermined threshold time. (2) The temperature of the main body of the auxiliary device 50 is equal to or lower than a predetermined auxiliary device threshold temperature. (3) The temperature of the coolant supplied by the water pump 52 is equal to or lower than a predetermined refrigerant threshold temperature.

[0026] If it is determined that the restriction relaxation condition is met (step S30: Yes), more specifically, if all of the above conditions (1) to (3) are met, the output control unit 72 executes the above-mentioned step S60. That is, in this embodiment, even if the above-mentioned restriction condition is met, if the restriction relaxation condition is met, the output control unit 72 does not execute the restriction control described below.

[0027] When the above condition (1) is met, the time during which the output voltage of the secondary battery 40 drops is short, and therefore, even if the drive current of the auxiliary device 50 increases as described above, the impact on the operation of the fuel cell system 100 can be said to be small. Note that the "time during which the output voltage of the secondary battery 40 becomes equal to or less than a predetermined threshold" is determined, for example, using the requested output power and requested output time in the output requests from the drive motor 30 and the auxiliary device 50. Furthermore, when the above conditions (2) and (3) are met, the body temperature of the auxiliary device 50 is low, and therefore, even if the auxiliary device 50 generates heat due to an increase in drive current, the operation of the auxiliary device 50 is not immediately restricted, and therefore, the impact on the operation of the fuel cell system 100 can be said to be small.

[0028] That is, when all of the above conditions (1) to (3) are met, even if the above-mentioned limiting conditions are met, it can be said that there is little impact on the operation of the fuel cell system 100, and therefore the output control unit 72 does not execute the above-mentioned limiting control. This makes it possible to prevent the operation of the fuel cell system 100 from becoming unstable due to frequent switching between limiting control and normal control.

[0029] If it is determined that the restriction relaxation condition is not met (step S30: No), more specifically, if at least one of the above conditions (1) to (3) is not met, in step S40, the output control unit 72 identifies the permitted use power of the secondary battery 40. In this embodiment, the output control unit 72 determines the permitted use power using the acquired accessory drive information so that the output voltage of the secondary battery 40 does not fall below a predetermined threshold. In this embodiment, the output control unit 72 determines the permitted use power using the acquired accessory drive information so that the output voltage of the secondary battery 40 falls within a predetermined appropriate range. By determining the permitted use power using the accessory drive information, it is possible to identify the permitted use power that will bring the output voltage of the secondary battery 40 into the predetermined appropriate range and that is appropriate for the drive status of the accessory 50.

[0030] In step S50, the output control unit 72 executes limit control. "Limit control" means suppressing the output power of the secondary battery 40 in accordance with the determined permitted use power. In this embodiment, the output control unit 72 controls the output voltage of the converter 20 so that the output power of the secondary battery 40 is equal to or less than the permitted use power. In addition, at this time, the output control unit 72 estimates the output voltage of the secondary battery 40 from the resistance value of the secondary battery 40 and the sweep current of the secondary battery 40, and executes feedback control of the output voltage of the secondary battery 40 using the estimated output voltage. The resistance value of the secondary battery 40 and the sweep current of the secondary battery 40 are detected by an electrical resistance sensor and a current sensor (not shown) provided in the fuel cell 10. After step S50 is completed, the above-mentioned step S10 is executed again.

[0031] According to the output control method in the fuel cell system 100 of the embodiment described above, when the restriction condition is met, the permitted power that will not cause the output voltage of the secondary battery 40 to fall below a predetermined threshold is identified, and restriction control is performed to control the output power of the secondary battery 40 in accordance with the permitted power. This prevents the output voltage of the secondary battery 40 from falling below a predetermined threshold and causing the output of the auxiliary equipment 50 to decrease, thereby preventing the output of the fuel cell system 100 from decreasing.

[0032] Furthermore, since the restriction control is not executed when a predetermined restriction relaxation condition is met, it is possible to prevent the operation of the fuel cell system 100 from becoming unstable due to frequent switching between the restriction control and normal control.

[0033] B. Other Embodiments: (B1) In the above embodiment, the output control unit 72 determines the permitted power use using the accessory drive information, but the present disclosure is not limited to this. The permitted power use may be set in advance and stored in the ROM 62. This configuration makes it easy to identify the permitted power use.

[0034] (B2) In the above embodiment, the output control unit 72 determines whether the restriction relaxation condition is met and does not execute restriction control if the restriction relaxation condition is met, but the present disclosure is not limited to this. The output control unit 72 may not determine whether the restriction relaxation condition is met, but may always execute restriction control if the restriction condition is met. This configuration also prevents the output voltage of the secondary battery 40 from falling below a predetermined threshold and thereby prevents the output of the auxiliary device 50 from decreasing, thereby preventing a decrease in the output of the fuel cell system 100. In addition, because it is not determined whether the restriction relaxation condition is met, an increase in the processing load on the control device 60 can be suppressed.

[0035] (B3) In the above embodiment, the output control unit 72 determines whether the limiting condition is that the fuel cell 10 is generating power and the power required by the auxiliary device 50 is equal to or greater than a predetermined threshold, but the present disclosure is not limited to this. For example, the output control unit 72 may determine whether the body temperature of the auxiliary device 50 is equal to or greater than a predetermined threshold, as the limiting condition. In other words, the "limiting condition" generally refers to a condition related to the operating status of the auxiliary device 50. Even with this configuration, limiting control can be executed when the body temperature of the auxiliary device 50 is equal to or greater than a predetermined threshold, and the same effect as the above embodiment can be achieved.

[0036] (B4) In the above embodiment, the output control unit 72 determines whether all of the above conditions (1) to (3) are satisfied as the restriction relaxation conditions, but the present disclosure is not limited to this. The output control unit 72 may determine whether at least one of the above conditions (1) to (3) is satisfied as the restriction relaxation conditions. This configuration also achieves the same effects as the above embodiment.

[0037] (B5) In the above embodiment, the fuel cell system 100 supplies power to the drive motor 30 as a load, but the present disclosure is not limited to this. The fuel cell system 100 may supply power to any electrical device as a load, such as a heater.

[0038] (B6) In the above embodiment, the fuel cell system 100 supplies power to the drive motor 30 as a load provided within the fuel cell system 100, but the present disclosure is not limited to this. The fuel cell system 100 may supply power to an external load provided outside the fuel cell system 100. This configuration also achieves the same effects as the above embodiment.

[0039] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0040] 10... fuel cell, 20... converter, 30... drive motor, 40... secondary battery, 50... auxiliary equipment, 51... compressor, 52... water pump, 60... control device, 61... CPU, 62... ROM, 63... RAM, 71... acquisition unit, 72... output control unit, 100... fuel cell system

Claims

1. 1. An output control method for controlling a fuel cell system that supplies power to a load, comprising: The fuel cell system includes: A fuel cell; a converter connected between the fuel cell and the load, for boosting the power supplied from the fuel cell; a secondary battery connected to the fuel cell via the converter in parallel with the load; an auxiliary machine connected to the fuel cell via the converter and connected to the secondary battery to be powered by the secondary battery; Equipped with The output control method includes: specifying a permitted use power that prevents the output voltage of the secondary battery from becoming equal to or lower than a predetermined threshold when a predetermined limiting condition related to the driving state of the auxiliary device is satisfied; executing a limit control to limit the output power of the secondary battery in accordance with the permitted power; Equipped with Output control method.

2. 2. The output control method according to claim 1, Even if the restriction condition is met, the restriction control is not executed if a predetermined restriction relaxation condition is met. Output control method.

3. 3. The output control method according to claim 1 or 2, the limiting conditions include a condition that the fuel cell is generating power and the power required by the auxiliary device is equal to or greater than a predetermined threshold; Output control method.

4. 3. The output control method according to claim 2, the auxiliary machine includes a coolant pump that supplies a coolant to the fuel cell; The restriction relaxation conditions are: the time during which the output voltage of the secondary battery is equal to or lower than a predetermined threshold due to an increase in the output power of the secondary battery is equal to or shorter than a predetermined threshold time; The temperature of the auxiliary equipment is equal to or lower than a predetermined auxiliary equipment threshold temperature; The temperature of the cooling medium supplied by the cooling medium pump is equal to or lower than a predetermined cooling medium threshold temperature; including at least one of the following conditions: Output control method.

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