Fuel cell system

Abstract

To control supply power to a load device so that the supply power will not exceed the upper limit of power of a fuel cell and a battery, without using a voltage converter, and provide a simpler and cheaper fuel cell system.SOLUTION: The fuel cell system includes a fuel cell (FC)1, a motor 2, a first power line 3 for connecting the FC1 and the motor 2, a battery 4, and a second power line 5 for connecting the battery 4 and the first power line 3. The first power line 3 is provided with an FC relay 7 for opening or closing the first power line 3 and the second power line 5 is provided with a battery relay 8 for opening or closing the second power line 5. The fuel cell system includes control means (ECU)10 for controlling opening or closing of both of the relays 7, 8 to control the upper limit of the output of the FC1 and the battery 4. An (EUC)10 controls both of the relays 7, 8 so that the relays will be closed when the charge rate of the battery 4 being monitored is smaller than 30%.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD

[0001] The technology disclosed in this specification relates to a fuel cell system that is used as a power source for electric vehicles and the like, and includes: a fuel cell connected to a load device; and a battery provided in a discharge path extending from the fuel cell to the load device and connected in parallel with the fuel cell. BACKGROUND ART

[0002] Conventionally, as this type of technology, for example, the "fuel cell system" described in the following Patent Document 1 is known. This system includes a fuel cell, a load device, a first wiring connecting the fuel cell and the load device, a battery, and a second wiring connected from the battery to the first wiring. The first wiring is provided with a voltage converter that performs voltage conversion between the voltage across the terminals of the fuel cell and the voltage on the load device side. PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0003] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2011-228294 SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0004] However, in the fuel cell system described in Patent Document 1, although the voltage converter can control the power supplied to the load device so as not to exceed the upper limit power of the fuel cell, there has been a concern that the voltage converter itself leads to increased cost and increased size of the system. In recent years, simple and inexpensive fuel cell systems to be mounted on electric vehicles and the like have been demanded.

[0005] The disclosed technology has been made in view of the above circumstances, and an object thereof is to provide a simple and more inexpensive fuel cell system that enables control of power supplied to a load device so as not to exceed the upper limit power of the fuel cell and the battery without using a voltage converter. [Means for solving the problem]

[0006] To achieve the above objective, the technology described in claim 1 is a fuel cell system comprising a fuel cell, a load device, a first power line connecting the fuel cell and the load device, a battery, and a second power line connecting the battery and the first power line, wherein the system comprises a first relay provided on the first power line for switching the first power line on and off, and a second relay provided on the second power line for switching the second power line on and off. The system includes relay control means for controlling the opening and closing of a first relay and a second relay in order to limit the upper limits of the fuel cell output and the battery output, and charge rate monitoring means for monitoring the battery charge rate, wherein the relay control means controls the closing of the first relay and the second relay when the battery charge rate monitored by the charge rate monitoring means is less than a third predetermined value. This is the purpose.

[0007] According to the above technology configuration, the power supply from the fuel cell to the load device is switched on and off by opening and closing the first relay, and the power supply from the battery to the load device is switched on and off by opening and closing the second relay. Therefore, by appropriately controlling the opening and closing of the first and second relays, it is possible to supply power to the load device in accordance with the output status of the fuel cell and battery. Furthermore, if the charge level of the monitored battery is lower than a third predetermined value, the relay control means closes the first and second relays, thereby allowing the fuel cell and battery outputs to remain unchanged. Consequently, the fuel cell and battery outputs are brought closer to the permissible operating range.

[0008] To achieve the above objective, the technology described in claim 2 is: A fuel cell system comprising a fuel cell, a load device, a first power line connecting the fuel cell and the load device, a battery, and a second power line connecting the battery and the first power line, further comprising: a first relay provided on the first power line for switching the first power line on and off; a second relay provided on the second power line for switching the second power line on and off; and a load output determination means for determining the instruction output value of the load device, wherein the load output determination means determines the instruction output value by subtracting the reduced output value of the fuel cell and the reduced output value of the battery from the requested output value of the load device. This is the purpose.

[0009] According to the configuration of the above technology, The first relay switches the power supply from the fuel cell to the load device on and off by opening and closing it, and the second relay switches the power supply from the battery to the load device on and off by opening and closing it. Therefore, by appropriately controlling the opening and closing of the first and second relays, it is possible to supply power to the load device in accordance with the output status of the fuel cell and the battery. In addition, the instructed output value of the load device is determined to match the output capacity status of the fuel cell and the battery at that time.

[0010] To achieve the above objective, the technology described in claim 3 is, 1 In the technology described above, the relay control means (1) opens the first relay and the second relay when the monitored charge rate is equal to or greater than a first predetermined value, (2) opens the first relay and closes the second relay when the monitored charge rate is equal to or greater than a second predetermined value and less than a first predetermined value, (3) closes the first relay and the second relay when the monitored charge rate is equal to or greater than a third predetermined value and less than a second predetermined value and the load device is braking, and (4) opens the first relay and closes the second relay when the monitored charge rate is equal to or greater than a third predetermined value and less than a second predetermined value and the load device is regenerating, with the relationship first predetermined value > second predetermined value > third predetermined value.

[0011] According to the above technology configuration, 1 In addition to the operation of the technology described above, (1) when the monitored charge level is equal to or greater than a first predetermined value, the relay control means opens the first relay and the second relay, thereby reducing the output of the fuel cell and the battery to zero. (2) when the monitored charge level is equal to or greater than a second predetermined value and less than a first predetermined value, the relay control means opens the first relay and closes the second relay, thereby reducing the output of the fuel cell to zero and the output of the battery to normal. (3) when the monitored charge level is equal to or greater than a third predetermined value and less than a second predetermined value, and the load device is braking, the relay control means closes the first relay and the second relay, thereby reducing the output of the fuel cell and the output of the battery to normal. (4) when the monitored charge level is equal to or greater than a third predetermined value and less than a second predetermined value, and the load device is regenerating, the relay control means opens the first relay and closes the second relay, thereby reducing the output of the fuel cell to zero and the output of the battery to normal. Therefore, the control described in (1) to (4) above brings the output of the fuel cell and the battery closer to the permissible operating range.

[0012] To achieve the above objective, the technology described in claim 4 is, 1 Alternatively, in the technology described in 3, the relay control means is intended to correct the instruction output value according to the charge level in order to suppress the instruction output value of the load device when the monitored charge level is less than a third predetermined value.

[0013] According to the above technology configuration, 1 Alternatively, in addition to the operation of the technology described in 3, if the monitored charge level is less than a third predetermined value, the relay control means corrects the instruction output value according to the charge level in order to suppress the instruction output value of the load device. Therefore, if the charge level is less than a third predetermined value, the supply of power from the fuel cell and battery to the load device is precisely suppressed according to the charge level.

[0014] To achieve the above objective, the technology described in claim 5 is, 2In the technology described in The relay control means is intended to correct the instruction output value according to the charge level in order to suppress the instruction output value of the load device when the monitored charge level is less than a third predetermined value.

[0015] According to the configuration of the above technology, the claims 2 In addition to the operation of the technology described in When the charge level of the monitored battery is lower than a third predetermined value, the relay control means closes the first and second relays, thereby allowing the fuel cell and battery outputs to remain unchanged. Consequently, the fuel cell and battery outputs are brought closer to the permissible operating range.

Effects of the Invention

[0016] According to the technology of claim 1, the electric power supplied to a load device can be controlled so as not to exceed the upper limit power of the fuel cell and the battery without using a voltage converter, and a simple and less expensive fuel cell system can be provided. Furthermore, if the battery charge level decreases, the upper limits of the fuel cell output and battery output can be restricted.

[0017] According to the technology of claim 2, This system allows for the control of power supplied to load devices to prevent exceeding the maximum power limits of the fuel cell and battery, without the need for a voltage converter, thus providing a simpler and more affordable fuel cell system. Furthermore, it prevents excessive power loads from being placed on the fuel cell and battery.

[0018] According to the technology of claim 3, the claims 1 In addition to the effect of the technology described in, the upper limits of the output of the fuel cell and the output of the battery can be more precisely restricted according to changes in the charging rate of the battery.

[0019] According to the technology of claim 4, the claims 1 In addition to the effect of the technology described in any one of 2 or 3, when the charging rate of the battery further decreases, the upper limits of the output of the fuel cell and the output of the battery can be more precisely restricted.

[0020] According to the technology of claim 5, the claims 2 In addition to the effect of the technology described in When the battery charge level decreases, the upper limits of the fuel cell output and battery output can be restricted.

Brief Description of Drawings

[0021] [Figure 1] A block diagram showing a fuel cell system mounted on an electric cart according to an embodiment. [Figure 2] A flowchart showing an example of the content of "power supply control" according to an embodiment. [Figure 3] An output correction value map referred to for obtaining an output correction value according to the charging rate of a battery according to an embodiment. [Modes for carrying out the invention]

[0022] Below, one embodiment of a fuel cell system implemented in a small electric vehicle (electric cart) will be described in detail with reference to the drawings.

[0023] [Overview of Fuel Cell Systems] Figure 1 shows a block diagram of the fuel cell system mounted on the electric cart of this embodiment. This fuel cell system comprises a fuel cell (FC) 1, an electric motor 2, a first power line 3 connecting the FC 1 and the motor 2, a battery 4, and a second power line 5 connecting the battery 4 and the first power line 3.

[0024] FC1 is an electrochemical battery that converts the chemical energy of fuel and oxidizer into electricity through a redox reaction, and has a well-known configuration. Motor 2 has a well-known configuration and corresponds to an example of a “load device” in this disclosed technology. Battery 4 in this embodiment consists of a rechargeable secondary battery.

[0025] In this embodiment, a rectifier diode 6 and an FC relay 7 for switching the first power line 3 are provided in series with the first power line 3. The FC relay 7 corresponds to the "first relay" in this disclosed technology. The second power line 5 is connected to the first power line 3 between the diode 6 and the motor 2. The second power line 5 is provided with a battery relay 8 for switching the second power line 5. The battery relay 8 corresponds to the "second relay" in this disclosed technology. The FC relay 7 and the battery relay 8 each have a well-known configuration that allows them to be switched on and off by electrical operation. The fuel cell system further includes an electronic control unit (ECU) 10 for controlling the switching of each relay 7 and 8. The ECU 10 has a well-known configuration including a central processing unit (CPU) for arithmetic processing, memory, and input / output ports. The ECU 10 corresponds to an example of the "relay control means" in this disclosed technology.

[0026] In this embodiment, the motor 2 is driven and connected to the drive wheels 11 of the electric cart. An accelerator sensor 12 is connected to the ECU 10. The accelerator sensor 12 detects the operating angle of the pedal 13 operated by the user of the electric cart as the accelerator opening angle and outputs the detection signal to the ECU 10.

[0027] The ECU 10 is electrically connected to the battery 4 and is configured to monitor the battery's state of charge (SOC). The ECU 10 also corresponds to an example of a "state of charge monitoring means" in this disclosed technology. Furthermore, the ECU 10 is electrically connected to the FC 1 and the battery 4 and is configured to measure the current and voltage of the FC 1 and the current and voltage of the battery 4. The ECU 10 also corresponds to an example of a "current and voltage measuring means".

[0028] Furthermore, the ECU 10 is configured to determine the instruction output value (motor instruction output value) of the motor 2, which is a load device, and this corresponds to an example of the "load output determination means" in this disclosed technology.

[0029] Here, in order to limit the upper limits of the output of FC1 and battery 4, it is necessary to limit the output of motor 2. Therefore, in this embodiment, ECU 10 performs the following "power supply control" when the electric cart is in operation.

[0030] [Regarding power supply control] Figure 2 shows an example of the contents of the "power supply control" of this embodiment stored in the memory of the ECU 10 as a flowchart.

[0031] When the process moves to this routine, in step 100, the ECU 10 takes in the current value (FC current value) FCCV and voltage value (FC voltage value) FCVV of the FC1 being measured, and the current value (battery current value) BTCV and voltage value (battery voltage value) BTVV of the battery 4, respectively.

[0032] Next, in step 110, the ECU 10 calculates the real output value of FC1 (FC real output value) FCRO and the real output value of battery 4 (battery real output value) BTRO. Here, the ECU 10 can determine the FC real output value FCRO from the measured FC current value FCCV and FC voltage value FCVV. Also, the ECU 10 can determine the battery real output value BTFCRO from the measured battery current value BTCCV and battery voltage value BTVV.

[0033] Next, in step 120, ECU10 sets the reduced output value of FC1 (FC reduced output value) FCDO as the result of subtracting the upper limit output value of FC1 (FC upper limit output value) FCUO from the FC real output value FCRO, and the result is a value greater than or equal to "0". The FC upper limit output value FCUO is a predetermined setting value.

[0034] Next, in step 130, the ECU 10 subtracts the upper limit output value of battery 4 (battery upper limit output value) BTUO from the real battery output value BTRO, and sets the reduced output value of battery 4 (battery reduced output value) BTDO to a value greater than or equal to "0". The upper limit output value of battery BTUO is a predetermined setting value.

[0035] Next, in step 140, the ECU 10 imposes an upper limit on the motor 2's command output value (motor command output value) MTCO by subtracting the FC reduction output value FCDO and the battery reduction output value BTDO from the motor 2's requested output value (motor requested output value) MTRO. In other words, it limits the motor output based on the battery output and FC output.

[0036] Next, in step 150, ECU10 retrieves the State of Charge (SOC) of battery 4.

[0037] Next, in step 160, the ECU 10 determines whether the State of Charge (SOC) is 80% or higher. 80% is an example of the "first predetermined value" in this disclosed technology. If the result of this determination is positive, the ECU 10 proceeds to step 170; otherwise, it proceeds to step 190.

[0038] In step 170, the ECU 10 controls the FC relay 7 and the battery relay 8 to open.

[0039] Next, in step 180, the ECU 10 controls motor 2 using the motor instruction output value MTCO, and then terminates the subsequent processing.

[0040] On the other hand, moving from step 160 to step 190, the ECU 10 determines whether the State of Charge (SOC) is "70%" or higher and less than "80%". "70%" is an example of the "second predetermined value" in this disclosed technology. If the result of this determination is positive, the ECU 10 moves to step 200; if the result is negative, it moves to step 210.

[0041] In step 200, the ECU 10 controls the FC relay 7 to open and the battery relay 8 to close, and then proceeds to step 180.

[0042] Meanwhile, in step 210, the ECU 10 determines whether the State of Charge (SOC) is "30%" or more and less than "70%". "30%" corresponds to an example of the "third predetermined value" (first predetermined value > second predetermined value > third predetermined value) of this disclosed technology. If the result of this determination is positive, the ECU 10 proceeds to step 220; if the result of this determination is negative, it proceeds to step 240.

[0043] In step 220, the ECU 10 controls the FC relay 7 and the battery relay 8 to close while the motor 2 is being braked.

[0044] Next, in step 230, the ECU 10 controls the FC relay 7 to open and the battery relay 8 to close while the motor 2 is regenerating, and then proceeds to step 180.

[0045] Meanwhile, in step 240, ECU10 determines whether the State of Charge (SOC) is less than 30%. If the result of this determination is positive, ECU10 proceeds to step 250; otherwise, it proceeds to step 180.

[0046] In step 250, the ECU 10 controls the FC relay 7 and the battery relay 8 to close.

[0047] Next, in step 260, the ECU 10 calculates an output correction value KO corresponding to the charge level (SOC). The ECU 10 can determine the output correction value KO corresponding to the charge level (SOC) by referring to an output correction value map, for example, as shown in Figure 3.

[0048] Next, in step 270, the ECU 10 sets the battery real output value BTRO as the motor command output value MTCO, or sets the motor command output value MTCO as the result of multiplying the motor command output value MTCO by the output correction value KO, and then proceeds to step 180.

[0049] According to the power supply control described above, the ECU 10 is configured to close the FC relay 7 and the battery relay 8 if the monitored battery 4's state of charge (SOC) is less than "30%" (third predetermined value) in order to limit the upper limits of the output of the FC1 and the battery 4.

[0050] Furthermore, according to the power supply control described above, the ECU 10 controls the following: (1) If the monitored charge rate SOC is 80% (first predetermined value) or higher, it opens the FC relay 7 and the battery relay 8; (2) If the monitored charge rate SOC is 70% (second predetermined value) or higher but less than 80%, it opens the FC relay 7 and closes the battery relay 8; (3) If the monitored charge rate SOC is 30% or higher but less than 70% and the motor 2 is braking, it closes the FC relay 7 and the battery relay 8; and (4) If the monitored charge rate SOC is 30% or higher but less than 70% and the motor 2 is regenerating, it opens the FC relay 7 and closes the battery relay 8.

[0051] Furthermore, according to the power supply control described above, if the monitored charge rate SOC is less than "30%", the ECU 10 corrects the motor command output value MTCO according to the charge rate SOC in order to suppress the motor command output value MTCO of motor 2.

[0052] In addition, according to the power supply control described above, the ECU 10 determines the motor command output value MTCO by subtracting the FC reduction output value FCDO and the battery reduction output value BTDO from the motor request output value MTOR.

[0053] [Regarding the operation and effects of fuel cell systems] As described above, with the configuration of the fuel cell system of this embodiment, the power supply from FC1 to motor2 is switched on and off by opening and closing the FC relay 7, and the power supply from battery 4 to motor2 is switched on and off by opening and closing the battery relay 8. Therefore, by appropriately controlling the opening and closing of the FC relay 7 and battery relay 8, it is possible to supply power to motor2 in accordance with the output status of FC1 and battery 4. For this reason, the power supplied to motor2 can be controlled so as not to exceed the upper limit power of FC1 and battery 4 without using a voltage converter, and a simpler and more inexpensive fuel cell system can be provided.

[0054] According to the configuration of this embodiment, when the State of Charge (SOC) of the monitored battery 4 is less than "30%" (third predetermined value), the ECU 10 controls the FC relay 7 and the battery relay 8 to close, thereby allowing the outputs of FC1 and battery 4 to function as they normally would. Consequently, the outputs of FC1 and battery 4 are brought closer to the permissible operating range. Therefore, when the State of Charge (SOC) of battery 4 decreases, the upper limits of the outputs of FC1 and battery 4 can be restricted.

[0055] According to the configuration of this embodiment, (1) when the monitored charge level SOC is 80% (first predetermined value) or higher, the ECU 10 controls the FC relay 7 and the battery relay 8 to open, so that the output of FC1 and the output of battery 4 become zero. (2) when the monitored charge level SOC is 70% (second predetermined value) or higher and less than 80%, the ECU 10 controls the FC relay 7 to open and the battery relay 8 to close, so that the output of FC1 becomes zero and the output of battery 4 becomes normal. (3) when the monitored charge level SOC is 30% (third predetermined value) or higher and less than 70%, and the motor 2 is braking, the ECU 10 controls the FC relay 7 and the battery relay 8 to close, so that the output of FC1 and the output of battery 4 become normal. (4) When the monitored charge level SOC is 30% or higher and less than 70%, and motor 2 is regenerating, ECU 10 controls FC relay 7 to open and battery relay 8 to close, thereby reducing the output of FC1 to zero and the output of battery 4 to normal. As a result, the output of FC1 and battery 4 are brought closer to the permissible operating range. Therefore, the controls described in (1) to (4) above allow for more precise limiting of the upper limits of the output of FC1 and battery 4 in response to changes in the charge level SOC of battery 4.

[0056] According to the configuration of this embodiment, when the monitored state of charge (SOC) is less than "30%", the ECU 10 corrects the power demand value according to the SOC in order to suppress the power demand value of the motor 2. Therefore, when the charge level is less than a third predetermined value, the power supply from the fuel cell and battery to the load device (motor instruction output value MTCO) is precisely suppressed according to the charge level. As a result, when the charge level (SOC) of the battery 4 decreases further, the upper limits of the output of the FC1 and the battery 4 can be more precisely limited.

[0057] According to the configuration of this embodiment, the ECU 10 determines the motor command output value MTCO by subtracting the FC reduction output value FCDO and the battery reduction output value BTDO from the motor request output value MTOR. Therefore, the motor command output value MTCO is determined that is appropriate to the output capacity status of the FC1 and the battery 4 at any given time. This prevents excessive output load from being placed on the FC1 and the battery 4.

[0058] Furthermore, this disclosed technology is not limited to the embodiments described above, and it can be implemented by appropriately modifying a part of the configuration without departing from the spirit of the disclosed technology.

[0059] For example, in the above embodiment, an electric motor 2 was used as the load device, but other types of electric motors may also be used. [Industrial applicability]

[0060] This disclosed technology can be used in fuel cell systems installed in electric vehicles. [Explanation of Symbols]

[0061] 1 FC (fuel cell) 2. Motor (load device) 3. First power line 4 batteries 5. Second power line 7 FC Relay (1st Relay) 8. Battery relay (second relay) 10 ECU (relay control means, charge rate monitoring means, load output determination means)

Claims

1. Fuel cells and Load device and A first power line connecting the fuel cell and the load device, Battery and The battery and the second power line connecting the first power line and In a fuel cell system equipped with, A first relay is provided on the first power line for switching the first power line on and off, A second relay is provided on the second power line for switching the second power line on and off, In order to limit the upper limits of the output of the fuel cell and the battery, relay control means control the opening and closing of the first relay and the second relay, The system includes a charge rate monitoring means for monitoring the charge rate of the aforementioned battery, The relay control means controls the first relay and the second relay to close when the charge level of the battery, as monitored by the charge level monitoring means, is less than a third predetermined value. A fuel cell system characterized by the following features.

2. A fuel cell, Load device and A first power line connecting the fuel cell and the load device, Battery and The battery and the second power line connecting the first power line and In a fuel cell system equipped with, A first relay is provided on the first power line for switching the first power line on and off, A second relay is provided on the second power line for switching the second power line on and off, The load device comprises a load output determination means for determining the instruction output value of the load device, The load output determination means determines the instructed output value by subtracting the reduced output value of the fuel cell and the reduced output value of the battery from the requested output value of the load device. A fuel cell system characterized by the following features.

3. In the fuel cell system according to claim 1, The relay control means is (1) When the monitored charge level reaches a first predetermined value or higher, the first relay and the second relay are controlled to open. (2) When the monitored charge level is greater than or equal to a second predetermined value and less than a first predetermined value, the first relay is opened and the second relay is closed. (3) When the monitored charge rate is greater than or equal to the third predetermined value and less than the second predetermined value, and the load device is in braking state, the first relay and the second relay are closed. (4) When the monitored charge rate is greater than or equal to the third predetermined value and less than the second predetermined value, and the load device is in regenerative mode, the first relay is opened and the second relay is closed. The relationship is such that the first predetermined value > the second predetermined value > the third predetermined value. A fuel cell system characterized by the following features.

4. In the fuel cell system according to claim 1 or 3, The relay control means corrects the instruction output value according to the charge rate in order to suppress the instruction output value of the load device when the monitored charge rate is less than the third predetermined value. A fuel cell system characterized by the following features.

5. In the fuel cell system according to claim 2, In order to limit the upper limits of the output of the fuel cell and the battery, relay control means control the opening and closing of the first relay and the second relay, A charge rate monitoring means for monitoring the charge rate of the aforementioned battery, Equipped with, The relay control means controls the first relay and the second relay to close when the charge level of the battery, as monitored by the charge level monitoring means, is less than a third predetermined value. A fuel cell system characterized by the following features.

6. In the fuel cell system according to claim 5, The relay control means is (1) When the monitored charge level reaches a first predetermined value or higher, the first relay and the second relay are controlled to open. (2) When the monitored charge level is greater than or equal to a second predetermined value and less than a first predetermined value, the first relay is opened and the second relay is closed. (3) When the monitored charge rate is greater than or equal to the third predetermined value and less than the second predetermined value, and the load device is in braking state, the first relay and the second relay are closed. (4) When the monitored charge rate is greater than or equal to the third predetermined value and less than the second predetermined value, and the load device is in regenerative mode, the first relay is opened and the second relay is closed. The relationship is such that the first predetermined value > the second predetermined value > the third predetermined value. A fuel cell system characterized by the following features.

7. In the fuel cell system according to claim 5 or 6, The relay control means corrects the instruction output value according to the charge rate in order to suppress the instruction output value of the load device when the monitored charge rate is less than the third predetermined value. A fuel cell system characterized by the following features.

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