Control device for a fuel cell system

Abstract

The present application provides a fuel cell system control device capable of accurately notifying a period of restriction of output power of a fuel cell accompanying deterioration of a vehicle-mounted fuel cell. The fuel cell system control device controls a fuel cell system having a vehicle-mounted fuel cell mounted on a vehicle, and notifies a period of restriction of output power of the vehicle-mounted fuel cell accompanying deterioration of the vehicle-mounted fuel cell. The control device includes a map storage section that stores a prediction map, an output restriction section that restricts output power of power generation of the vehicle-mounted fuel cell, a map update section that updates the prediction map by correcting a prediction curve, and a notification section that, based on the prediction curve of the updated prediction map, predicts the period of restriction before the output power is restricted by the output restriction section, and notifies the predicted period of restriction.

Description

Technical Field

[0001] This invention relates to a control device for a fuel cell system. Background Technology

[0002] As an example of this technology, Patent Document 1 proposes a fuel cell output voltage prediction system that pre-stores the relationship between a reference degradation index of the fuel cell and the output voltage of the fuel cell, and predicts the output voltage of the fuel cell based on the degradation index of the on-board fuel cell and the stored reference degradation index.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2022-096769 Summary of the Invention

[0004] However, it is known that as the on-board fuel cell deteriorates over time, the high-load voltage output by the fuel cell decreases relative to the high-load power required during high-load driving. If the high-load voltage decreases, an excessive current flows through the fuel cell to meet the required high-load power. Therefore, sometimes when the voltage falls below a preset limit, control is implemented to limit the output power of the on-board fuel cell (limiting control). If such limiting control of the fuel cell's output power is implemented, the driver's ability to drive the vehicle is restricted. Therefore, the control device preferably notifies the driver of the restriction period in advance before implementing the limiting control. This notification allows for the replacement or maintenance of the vehicle's fuel cell before the limiting control is implemented.

[0005] Here, as shown in Patent Document 1, the relationship between the degradation of an on-board fuel cell and high load voltage can also be predicted based on characteristics previously measured in a reference fuel cell. However, it is conceivable that the relationship between the degradation of an on-board fuel cell and high load voltage may change over time due to deviations in the power output characteristics during the manufacture of the fuel cell or due to the operating state of the fuel cell caused by the driver's driving style. Therefore, it may be impossible to inform the driver of the limitation period before limiting the output power of the fuel cell.

[0006] The present invention was made in view of this, and its object is to provide a control device for a fuel cell system capable of accurately notifying the period of limited output power of the fuel cell caused by the deterioration of the on-board fuel cell mounted in a vehicle.

[0007] In view of the above-mentioned problems, the present invention relates to a control device for a fuel cell system that controls a fuel cell system having an on-board fuel cell mounted on a vehicle and notifies the limiting period of the output power of the on-board fuel cell due to degradation of the on-board fuel cell. The control device includes: a mapping storage unit that, in a reference fuel cell of the same type as the on-board fuel cell, periodically acquires a low-load voltage (less than a predetermined threshold) of low-load power output required by the reference fuel cell for the reference fuel cell, and a high-load voltage (above a predetermined threshold) of high-load power output required by the reference fuel cell for the reference fuel cell, plots the relationship between the acquired low-load voltage and the high-load voltage, and stores a prediction mapping map including an approximate curve based on multiple plotted points as a prediction curve for predicting the limiting period; and an output limiting unit that sets a pre-set limiting voltage as the high-load power output required by the on-board fuel cell for high-load driving of the vehicle. The following steps are taken: A prediction mapping unit records, at each predetermined elapsed time, the low-load voltage output by the on-board fuel cell for the required low-load power during low-load driving of the vehicle, and the high-load voltage output by the on-board fuel cell for the required high-load power during high-load driving of the vehicle. It plots the relationship between the low-load voltage and the high-load voltage recorded at each elapsed time in the prediction mapping, corrects the prediction curve based on the plotted points, and thereby updates the prediction mapping. A notification unit, based on the updated prediction mapping's prediction curve and the high-load voltage output during high-load driving of the vehicle, predicts the restriction period before the output limiting unit restricts the output power, and notifies the unit of the predicted restriction period.

[0008] Invention Effects

[0009] According to the present invention, by updating the prediction map that predicts the period of power limitation of the fuel cell output caused by the degradation of the on-board fuel cell mounted in the vehicle, the period of limitation can be notified with good accuracy. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of a fuel cell system according to an embodiment of the present invention.

[0011] Figure 2 yes Figure 1 The diagram shows the control block diagram of the control device for the fuel cell system.

[0012] Figure 3 yes Figure 2The flowchart shown illustrates the creation of the prediction mapping.

[0013] Figure 4 yes Figure 2 The flowchart of the control device is shown.

[0014] Figure 5 It is stored in Figure 1 The prediction mapping diagram in the control device shown. Detailed Implementation

[0015] The following is for reference. Figures 1-5 The fuel cell system 10 and the control device 6 for controlling the fuel cell system according to this embodiment will be described.

[0016] First, use Figure 1 The structure of the fuel cell system 10 according to an embodiment of the present invention will be described below. Figure 1 As shown, the fuel cell system 10 of this embodiment is a system that drives the traction motor M3 to rotate by supplying power from the on-board fuel cell 2 (hereinafter referred to as fuel cell 2) and the battery 52 mounted on the vehicle 1 to the traction motor M3 via the traction inverter 53. The fuel cell system 10 includes the fuel cell 2, an oxidizing gas piping system 3 for supplying air as an oxidizing gas to the fuel cell 2, and a hydrogen piping system 4 for supplying hydrogen as hydrogen to the fuel cell 2. The fuel cell system 10 also includes a power system 5 for charging and discharging power, a control device 6 for centralized control of the entire system, etc.

[0017] Fuel cell 2, for example, is composed of a solid polymer electrolyte and has a stacked structure with multiple individual cells stacked on top of each other. Each individual cell constituting fuel cell 2 has a membrane electrode assembly (MEA) formed by a polymer electrolyte membrane sandwiched between an anode and a cathode electrode, a plate clamping structure for supplying hydrogen and oxidizing gas, and a pair of plates clamping the cathode and anode electrodes from both sides. Hydrogen is supplied to the hydrogen flow path of one plate, and oxidizing gas is supplied to the oxidizing gas flow path of the other plate; through this gas supply, fuel cell 2 generates power. A current sensor 2a and a voltage sensor 2b are installed on fuel cell 2 to detect the current and voltage (output current and output voltage) during power generation.

[0018] The oxidizing gas piping system 3 includes an air compressor 31, an oxidizing gas supply line 32, a cathode exhaust gas path 34, and a motor M1 that drives the air compressor 31. The air compressor 31 is driven by the motor M1, which operates under the control command of the control device 6, and supplies air (oxidizing gas) drawn in from the outside air to the cathode of the fuel cell 2 via the oxidizing gas supply line 32. Cathode exhaust gas is discharged from the cathode of the fuel cell 2 via the cathode exhaust gas path 34.

[0019] The hydrogen piping system 4 includes a high-pressure hydrogen tank 41, a hydrogen supply pipeline 42, a hydrogen circulation pipeline 43, an anode tail gas flow path 44, a hydrogen circulation pump 45, a check valve 46, and a motor M2 for driving the hydrogen circulation pump 45.

[0020] High-pressure hydrogen tank 41 supplies hydrogen released from high-pressure hydrogen tank 41 to the anode of fuel cell 2 via hydrogen supply line 42. Hydrogen recirculation line 43 is a return gas flow path for returning unreacted hydrogen to fuel cell 2. Low-pressure unreacted hydrogen discharged from fuel cell 2 is pressurized by hydrogen recirculation pump 45 driven by motor M2, which operates under control commands from control device 6, and guided to hydrogen supply line 42. Anode exhaust flow path 44 discharges anode exhaust containing hydrogen exhaust from fuel cell 2 to the outside of the system.

[0021] The power system 5 includes a high-voltage DC / DC converter 51, a battery 52, a traction inverter 53, an auxiliary inverter 54, a traction motor M3, and an auxiliary motor M4. The high-voltage DC / DC converter 51 is a DC-DC voltage converter with the following functions: adjusting the DC voltage input from the battery 52 and outputting it to the traction inverter 53; and adjusting the DC voltage input from the fuel cell 2 or the traction motor M3 and outputting it to the battery 52. ​​These functions of the high-voltage DC / DC converter 51 enable the charging and discharging of the battery 52. ​​Furthermore, the high-voltage DC / DC converter 51 controls the output voltage of the fuel cell 2.

[0022] Battery 52 is connected in parallel with traction motor M3, serving to store residual power or regenerative energy during regenerative braking, and acting as an energy buffer during load changes accompanying the acceleration or deceleration of the fuel cell vehicle. Battery 52 is a rechargeable secondary battery. A portion of the DC power generated by fuel cell 2 is boosted or bucked by high-voltage DC / DC converter 51 and used to charge battery 52. ​​Alternatively, a rechargeable energy storage device other than a secondary battery (e.g., a capacitor) can be used instead of battery 52.

[0023] Traction inverter 53 and auxiliary inverter 54 convert the DC power output from fuel cell 2 or battery 52 into three-phase AC power according to the given control commands, and supply it to traction motor M3 and auxiliary motor M4. Traction motor M3 is a motor used to drive wheels 7L and 7R. A speed detection sensor 5a is installed on traction motor M3 to detect its rotational speed. Auxiliary motor M4 is a motor used to drive various auxiliary devices. In this embodiment, all devices that operate by receiving power from fuel cell 2 are collectively referred to as load devices.

[0024] The control unit 6 is a computer system for centralized control of the various parts of the fuel cell system 10, and it has a CPU and various memories (ROM, RAM, etc.). The control unit 6 receives input signals from various sensors (e.g., signals from the speed detection sensor 5a or the throttle pedal sensor 6a that detects the throttle pedal opening), and calculates the load of the load device (required output). Then, the control unit 6 controls the output voltage and output current of the fuel cell 2 to generate output power corresponding to the load. Furthermore, the control unit 6 controls the output pulse width of the traction inverter 53 and the auxiliary inverter 54, etc., to control the traction motor M3 and the auxiliary motor M4.

[0025] As described above, the control device 6 is a device for controlling each device of the fuel cell system 10 having a fuel cell 2 mounted on the vehicle 1. The control device 6 notifies the period of power limitation of the fuel cell 2 due to the deterioration of the fuel cell 2.

[0026] In this embodiment, such as Figure 2 As shown, the control device 6 also includes a mapping map storage unit 61, an output limiting unit 62, a mapping map updating unit 63, and a notification unit 64. Figure 4 As shown, the mapping storage unit 61 stores a prediction mapping map M that includes a prediction curve C1 for predicting the restriction period of the restriction control (described later). Regarding the prediction curve C1 included in the prediction mapping map M, according to... Figure 3 The process shown is based on the same type of benchmark as fuel cell 2, using results pre-measured in the fuel cell.

[0027] Specifically, firstly, in step S31, a reference fuel cell (not shown) of the same type as fuel cell 2 is prepared. At this time, for the unused reference fuel cell, the low-load voltage VL and high-load voltage VH (described later) are measured as initial values ​​(see reference). Figure 5 ).

[0028] Next, in steps S32 to S36, for a low load power quantity required by the reference fuel cell that is less than a specified threshold, the low load voltage output by the reference fuel cell is obtained, and for a high load power quantity required by the reference fuel cell that is above the specified threshold, the high load voltage output by the reference fuel cell is obtained, and these values ​​are obtained over time as the reference fuel cell deteriorates.

[0029] Specifically, in step S32, by adjusting the supply of hydrogen and oxidant gas to the reference fuel cell, power generation is performed alternately and repeatedly at the same power required by the fuel cell 2 during low-load driving (low-load power) and high-load driving (high-load power) for a specified period. Here, the low-load power is a power amount less than a specified threshold, and the high-load power is a power amount greater than or equal to the specified threshold. This power generation can be achieved by actually installing the reference fuel cell in the vehicle and repeatedly performing high-load and low-load driving. Low-load driving is power generation control based on conditions such as driving the vehicle on a flat road, where the power required by the fuel cell is less than the specified threshold (low-load power). High-load driving is power generation control based on conditions such as driving the vehicle uphill, where the power required by the fuel cell is greater than the specified threshold (high-load power).

[0030] Next, in step S33, the low-load voltage (value) during low-load driving and the high-load voltage (value) during high-load driving are obtained. Here, it is known that as the fuel cell deteriorates, the low-load voltage output by the on-board fuel cell decreases relative to the low-load power required for low-load driving of the vehicle, and the high-load voltage output by the on-board fuel cell decreases relative to the high-load power required for high-load driving of the vehicle.

[0031] Therefore, in step S34, it is determined whether the reference fuel cell has deteriorated. Specifically, if the high load voltage obtained in step S33 decreases (specifically, if the difference between the high load voltage obtained previously and the high load voltage is greater than a predetermined value), it is determined that the reference fuel cell has deteriorated. In this case, proceed to step S35, where the low load voltage and high load voltage are recorded in step S33. Specifically, as follows... Figure 5 As indicated by the △ markers, the points corresponding to low load voltage and high load voltage are plotted on the prediction mapping map M. In step S34, assuming the reference fuel cell has not deteriorated, the process returns to step S32.

[0032] In step S36, it is determined whether the recorded high load voltage is lower than the limit voltage VR. If the recorded high load voltage is lower than the limit voltage VR, proceed to step S37; otherwise, return to step S32. Steps S32 to S36 are repeated until the recorded high load voltage becomes higher than the limit voltage VR. Thus, it is possible to record the values ​​of both the low load voltage and the high load voltage as the reference fuel cell deteriorates, and to... Figure 5 Multiple points, indicated by multiple △ markers, are plotted on the prediction map M as a relationship between the acquired low-load voltage and high-load voltage. In step S37, a prediction map M containing an approximate curve based on the plotted multiple points is created as the prediction curve C1 for the prediction limit period. The approximate curve is a higher-order function than a quadratic function; for example, a higher-order function of the low-load voltage, which becomes a variable of the prediction curve C1, is calculated using the least squares method. Thus, in Figure 4 In step S41, the predicted mapping map M is stored in the mapping map storage unit 61.

[0033] Here, if, as fuel cell 2 deteriorates and the high-load voltage drops to the specified output voltage (below the limiting voltage VR), then an excessive current flows through fuel cell 2 to meet the required high-load power. To prevent this excessive current flow, Figure 2 The output limiting unit 62 shown performs the following power generation limitation control: when the high load power required for high-load driving of vehicle 1 is below the preset limit voltage VR, the output power generated by the fuel cell is limited. This prevents damage to the fuel cell 2.

[0034] The mapping map update unit 63 records the low-load voltage and high-load voltage of the fuel cell 2 actually installed on the vehicle 1, and updates the prediction mapping map M. First, the mapping map update unit 63 records the low-load voltage and high-load voltage of the fuel cell 2 actually installed on the vehicle 1, and updates the prediction mapping map M. Figure 4 In steps S42 to S45 shown, the low-load power required for low-load driving of vehicle 1 and the low-load voltage output by fuel cell 2 are recorded at each specified elapsed time, and the specified high-load power required for high-load driving of vehicle 1 and the high-load voltage output by fuel cell 2 are recorded.

[0035] Specifically, in step S42, by driving the vehicle 1 for a predetermined period of time, the fuel cell 2 is subjected to power generation at the power required by the fuel cell 2 during low-load driving of the vehicle 1 (low-load power) and during high-load driving of the vehicle 1 (high-load power). Here, as described above, the low-load power is a power amount less than a predetermined threshold, and the high-load power is a power amount greater than or equal to the predetermined threshold. Low-load driving, for example, is power generation control of the fuel cell at a power amount less than the predetermined threshold (low-load power) when driving the vehicle on a flat road. High-load driving, for example, is power generation control of the fuel cell at a power amount greater than the predetermined threshold (high-load power) when driving the vehicle uphill.

[0036] Next, in step S43, the low-load voltage (value) during low-load driving and the high-load voltage (value) during high-load driving after step S42 are acquired. In step S44, it is determined whether the fuel cell 2 has deteriorated. Specifically, if the high-load voltage acquired in step S42 decreases (specifically, if the difference from the previously acquired high-load voltage is greater than a predetermined value), it is determined that the fuel cell 2 has deteriorated. In this case, proceed to step S45, where the last acquired low-load voltage and high-load voltage are recorded in step S43. Specifically, as follows... Figure 5 As indicated by the ● or ○ markers, the points corresponding to low load voltage and high load voltage are plotted on the prediction mapping map M. In step S44, assuming the reference fuel cell has not deteriorated, the process returns to step S42.

[0037] In step S46, the mapping map update unit 63 corrects the prediction curve C1 based on multiple points drawn on the prediction mapping map M, thereby updating the prediction mapping map M. Specifically, the coordinates of the drawn points are substituted into the approximate curves of higher-order functions constructed from the prediction curve C1, and the coefficients of each degree of these higher-order functions are corrected. Here, by... Figure 4 The illustrated process repeats the high-order function a certain number of times, enabling multiple points to be plotted on the prediction map M, and obtaining corrected new prediction curves C2 and C3. Figure 5 In the case of prediction curve C2, it can be determined that the degradation of fuel cell 2 is slow compared to the reference fuel cell. On the other hand, in the case of prediction curve C3, it can be determined that the degradation of fuel cell 2 is rapid compared to the reference fuel cell.

[0038] In step S47, the notification unit 64 predicts the limitation period based on the prediction curves C2, C3, etc., and the high-load voltage output by the vehicle 1 during high-load driving, before the output limiting unit 62 limits the output power. In step S48, the predicted limitation period is notified. Here, it is known that the horizontal axis of the prediction mapping map M also corresponds to the time of degradation of the fuel cell 2, and this is used to predict the limitation period.

[0039] Specifically, such as Figure 5 As shown, in the prediction curve C2 (reference ○ mark), the difference va between the measured low-load voltage Va and the low-load voltage VA (reference □ mark) in the high-load voltage limiting voltage VR is calculated. The difference vLa between the measured low-load voltage Va and the initial low-load voltage VL is calculated. The period Ta from the initial state of fuel cell 2 to the measurement of low-load voltage Va is determined. By calculating va × Ta / vLa, the start time of the output power limiting control performed by the output limiting unit 62 can be calculated from the current moment, and the limiting period (the period limited by the limiting voltage VR) can be predicted. Similarly, in the prediction curve C3, by calculating vb × Tb / vLb, the start time of the output power limiting control performed by the output limiting unit 62 can be calculated from the current moment, and the limiting period (the period limited by the limiting voltage VR) can be predicted.

[0040] Thus, in step S48, if the predicted limitation period is notified, the replacement or maintenance of the fuel cell 2 can be performed before the limitation control by the output limitation unit 62. In particular, if... Figure 5 As shown in the prediction curves C2 and C3, the relationship between the degradation of the on-board fuel cell and the high-load voltage sometimes changes over time depending on deviations in the power output characteristics during the manufacturing of the fuel cell or the operating state of the fuel cell caused by the driver's driving style. Even in this case, the driver can be notified of the limitation period before the output power of the fuel cell 2 is limited. Thus, the limitation period of the fuel cell 2's output power caused by the degradation of the fuel cell 2 mounted on the vehicle 1 can be notified with good accuracy.

[0041] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments, and various design changes can be made without departing from the spirit of the present invention as set forth in the claims.

[0042] Symbol Explanation

[0043] 1-Vehicle, 10-Fuel cell system, 2-On-board fuel cell (fuel cell), 6-Control device, 61-Mapping storage unit, 62-Output limiting unit, 63-Mapping update unit, 64-Notification unit.

Claims

1. A control device for a fuel cell system, comprising controlling a fuel cell system having an on-board fuel cell mounted on a vehicle, and notifying the user of a period of power limitation of the on-board fuel cell due to degradation of the on-board fuel cell, the control device for the fuel cell system being characterized by comprising: The mapping storage unit acquires, over time, the low-load voltage (below a predetermined threshold) of the low-load power output required by the reference fuel cell for the reference fuel cell, and the high-load voltage (above a predetermined threshold) of the high-load power output required by the reference fuel cell for the reference fuel cell, as the reference fuel cell deteriorates. It plots the relationship between the acquired low-load voltage and the high-load voltage and stores a prediction mapping diagram that includes an approximate curve based on multiple plotted points as a prediction curve for predicting the limiting period. The output limiting unit limits the output power of the on-board fuel cell when the high-load voltage output by the on-board fuel cell for the high-load power required during high-load driving of the vehicle is below a preset limiting voltage. The prediction mapping update unit records, at each predetermined elapsed time, the low-load voltage output by the onboard fuel cell for the low-load power required during low-load driving of the vehicle, and the high-load voltage output by the onboard fuel cell for the high-load power required during high-load driving of the vehicle. It plots the relationship between the low-load voltage and the high-load voltage recorded at each elapsed time in the prediction mapping map, corrects the prediction curve based on the plotted points, and thereby updates the prediction mapping map; and The notification unit, based on the prediction curve of the updated prediction map and the high-load voltage output by the vehicle during high-load driving, predicts the limiting period before the output limiting unit limits the output power, and notifies the predicted limiting period.

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