Fuel cell system

Abstract

In a fuel cell system equipped with multiple batteries, the goal is to suppress the narrowing of the control range for the charge rate of each battery by reducing the difference in charge rates between the batteries. [Solution] The fuel cell system 1 comprises an FC stack 11 and a plurality of batteries 13A, 13B that charge the electricity generated by the FC stack 11. The plurality of batteries 13A, 13B are set to the same specified voltage and connected in series, and do not have a DC-DC converter. The fuel cell system 1 further comprises a plurality of electric cooling fans 21A to 21D that contribute to the operation of the system. Furthermore, the same number of cooling fans (21A, 21B) and (21C, 21D) are connected to each of the plurality of batteries 13A, 13B.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a fuel cell system including a fuel cell and a battery that charges the electric power generated by the fuel cell.

Background Art

[0002] Conventionally, for example, a "vehicle battery device" described in Patent Document 1 below is known. This device is configured to output a voltage higher than the voltage output by each battery by connecting a plurality of batteries in series, and in addition, is configured as a device without a DCDC converter.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the battery device described in Patent Document 1, differences in performance and deterioration may occur among a plurality of batteries, and differences in their state of charge (SOC) may occur. In this case, since the device is without a DCDC converter, there is a concern that the SOC control range of the battery with a low SOC becomes narrow depending on the SOC control range of the battery with a high SOC in controlling the SOC of each battery. In this regard, the same concern is assumed in a fuel cell system without a DCDC converter including a fuel cell and a plurality of batteries that charge the electric power generated by the fuel cell and configured to control the SOC of the plurality of batteries.

[0005] This disclosed technology has been made in view of the above circumstances, and its object is to suppress the narrowing of the control range of the state of charge of each battery by narrowing the difference in the state of charge of each battery in a fuel cell system including a plurality of batteries. [Means for solving the problem]

[0006] To achieve the above objective, the technology described in claim 1 comprises a fuel cell and a plurality of batteries for charging the electricity generated by the fuel cell, the plurality of batteries being set to the same specified voltage and connected in series, and a fuel cell system without a DC-DC converter, further comprising a plurality of electric auxiliary devices that contribute to the operation of the fuel cell system, wherein each of the plurality of batteries is connected to the same number of electric auxiliary devices.

[0007] According to the above technology configuration, each of the multiple batteries is connected to the same number of electric auxiliary devices. Therefore, if there is a difference in the charge level among the multiple batteries, the charge level of each battery is adjusted by adjusting the power consumed by each electric auxiliary device in accordance with that difference.

[0008] To achieve the above objective, the technology described in claim 2 further comprises a control device for controlling a plurality of electric auxiliary devices in the technology described in claim 1, wherein the control device is configured to measure the charge rate of each of the plurality of batteries, and controls the current supplied from the plurality of batteries to each electric auxiliary device connected to them so as to reduce the difference between the measured charge rates.

[0009] According to the configuration of the above technology, in addition to the operation of the technology described in claim 1, when there is a difference in the charge rate among multiple batteries, the power consumed by each battery in each electric auxiliary device is adjusted according to the difference in charge rate, and the charge rate of each battery is adjusted.

[0010] To achieve the above objective, the technology described in claim 3, in the technology described in claim 2, is intended to increase the current supplied to the electric auxiliary equipment connected to the battery with the higher measured charge rate above a reference value when the difference in charge rate is greater than a predetermined value, and to set the current supplied to the electric auxiliary equipment connected to the battery with the lower measured charge rate as the reference value.

[0011] According to the configuration of the above technology, in addition to the operation of the technology described in claim 2, when the difference in charge levels exceeds a predetermined value, the current supplied to the electric auxiliary equipment connected to the battery with the higher charge level increases above the reference value, and the current supplied to the electric auxiliary equipment connected to the battery with the lower charge level becomes the reference value.

[0012] To achieve the above objective, the technology described in claim 4 is intended to be the technology described in claim 3, wherein the control device changes the magnitude of the increase in the current value supplied to the electric auxiliary equipment according to the difference in charge rate.

[0013] According to the configuration of the above technology, in addition to the effects of the technology described in claim 3, the magnitude of the increase in the current value supplied to each electric auxiliary device changes according to the difference in charge rates between each battery. [Effects of the Invention]

[0014] According to the technology described in claim 1, in a fuel cell system equipped with multiple batteries, it is possible to suppress the narrowing of the control range of the charge rate of each battery by narrowing the difference in charge rates of each battery.

[0015] According to the technology described in claim 2, in addition to the effects of the technology described in claim 1, the amount of power consumed by each electric auxiliary device can be adjusted according to the difference in charge levels between each battery.

[0016] According to the technology described in claim 3, in addition to the effects of the technology described in claim 2, the difference in charge levels among multiple batteries can be narrowed by increasing the power consumption of the battery with the highest charge level.

[0017] According to the technology described in claim 4, in addition to the effects of the technology described in claim 3, the difference in charge rates between each battery can be efficiently narrowed according to the difference in charge rates between them. [Brief explanation of the drawing]

[0018] [Figure 1] A schematic diagram showing a fuel cell system according to the first embodiment. [Figure 2] Flowchart showing the details of the cooling fan control according to the first embodiment. [Figure 3] Table showing the relationship between the first fan duty and the second fan duty with respect to the difference in magnitude between the first charging rate and the second charging rate in the cooling fan control according to the first embodiment. [Figure 4] Schematic configuration diagram showing the fuel cell system according to the second embodiment.

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments in which the fuel cell system is embodied as a fuel cell system mounted on an electric vehicle will be described.

[0020] <First Embodiment> First, the first embodiment will be described in detail with reference to FIGS. 1 to 3.

[0021] [Regarding the Configuration of the Fuel Cell System] FIG. 1 shows a schematic configuration diagram of the fuel cell system 1 according to this embodiment. As shown in FIG. 1, the fuel cell system 1 of this embodiment is a simple DCDC converterless system without a DCDC converter. That is, this fuel cell system 1 includes an FC stack 11, a motor 12, and two batteries 13A and 13B. The two batteries 13A and 13B are the first battery 13A and the second battery 13B. The two batteries 13A and 13B are each set to the same specified voltage (24V) and are connected in series. The motor 12 and the two batteries 13A and 13B are each connected in parallel to the FC stack 11. Here, a DCDC converter is a device that converts DC (direct current) to DC (direct current), and is a device that converts the voltage used in the system to direct current. Since this fuel cell system 1 is DCDC converterless, its configuration can be simplified accordingly.

[0022] The FC stack 11 generates electricity by receiving hydrogen gas from the hydrogen system and air from the air system. A detailed explanation of the hydrogen system and air system is omitted here. In this embodiment, the fuel cell system 1 is configured as an "open cathode type" in which the air system configuration is shared with the cooling system. The FC stack 11 corresponds to an example of a "fuel cell" in this disclosed technology. The electricity generated by the FC stack 11 is supplied to the motor 12 and two batteries 13A and 13B.

[0023] The fuel cell system 1 further comprises four cooling fans 21A, 21B, 21C, and 21D. The four cooling fans 21A to 21D are used in both the air system, which supplies air to the FC stack 11, and the cooling system, which cools the FC stack 11, in order to contribute to the operation of the fuel cell system 1. The four cooling fans 21A to 21D are the first cooling fan 21A, the second cooling fan 21B, the third cooling fan 21C, and the fourth cooling fan 21D. Each cooling fan 21A to 21D is an electric fan driven by an electric motor. Each cooling fan 21A to 21D corresponds to an example of an "electric auxiliary" in this disclosed technology.

[0024] Each of the two batteries 13A and 13B is connected to two (the same number) cooling fans 21A and 21B and two cooling fans 21C and 21D. Specifically, the first battery 13A is connected to the first cooling fan 21A and the second cooling fan 21B via the first fan driver 15A. The second battery 13B is connected to the third cooling fan 21C and the fourth cooling fan 21D via the second fan driver 15B.

[0025] The fuel cell system 1 further includes an electronic control unit (ECU) 20 that controls four cooling fans 21A to 21D. The ECU 20 includes, for example, an arithmetic processing unit such as a CPU, a storage unit including a ROM that stores control programs and control data processed by the CPU, a RAM used as various work areas for control processing, and an input / output interface unit. The control unit 20 performs various controls on the fuel cell system 1 according to the control program stored in the storage unit. Here, since the power consumption of the ECU 0 is very small and negligible, the ECU 20 is connected only to the first battery 13A. The ECU 20 corresponds to an example of a "control unit" in this disclosed technology.

[0026] In this embodiment, the ECU 20 is configured to measure the state of charge (SOC) of the two batteries 13A and 13B. Specifically, the ECU 20 incorporates an SOC measurement circuit that measures the SOC of each battery 13A and 13B based on their current values. The ECU 20 also controls the current supplied to the cooling fans 21A to 21D via the fan drivers 15A and 15B based on the measured SOC.

[0027] Here, since this fuel cell system 1 is configured without a DC-DC converter, there is a concern that when controlling the SOC of each battery 13A, 13B, the SOC control range of the battery 13A, 13B with the lower SOC will be narrower, depending on the SOC control range of the other battery 13B, 13A with the higher SOC. Therefore, in this embodiment, in order to suitably control the SOC of each battery 13A, 13B, the following "cooling fan control" is implemented.

[0028] [Cooling fan control] Figure 2 shows a flowchart illustrating the "cooling fan control" process in this embodiment. When the process moves to this routine, in step 100, the ECU 20 acquires the first charge level (SOC1), which is the charge level of the first battery 13A, and the second SOC2, which is the charge level of the second battery 13B.

[0029] Next, in step 110, the ECU20 calculates the difference between the first charge level SOC1 and the second charge level SOC2 as (charge level difference)ΔSOC.

[0030] Next, in step 120, the ECU20 determines whether the charge level difference ΔSOC is greater than or equal to "-10 (%)" and less than or equal to "0 (%)". If the result of this determination is positive, that is, if the second charge level SOC2 is slightly greater than the first charge level SOC1, the ECU20 proceeds to step 130; otherwise, the ECU20 proceeds to step 140.

[0031] In step 130, ECU20 sets the reference fund duty BFDY as the first fund duty FDY1. ECU20 also sets the reference fund duty BFDY as the second fund duty FDY2. That is, both the first fund duty FDY1 and the second fund duty FDY2 are set to the reference fund duty BFDY in order to slightly reduce the charge level SOC1 of the first battery 13A and the charge level SOC2 of the second battery 13B to roughly the same level. After this, ECU20 terminates the process. The first fund duty FDY1 and the second fund duty FDY2 correspond to examples of "current values" in this disclosed technology. The reference fund duty BFDY corresponds to an example of a "reference value" in this disclosed technology.

[0032] Here, the first fan duty cycle FDY1 is the command value for the current sent to the first fan driver 15 to control the first and second cooling fans 21A and 21B. The ECU 20 supplies current to the first and second cooling fans 21A and 21B based on the set first fan duty cycle FDY1. The second fan duty cycle FDY2 is the command value for the current sent to the second fan driver 15B to control the third and fourth cooling fans 21C and 21D. The ECU 20 supplies current to the third and fourth cooling fans 21C and 21D based on the set second fan duty cycle FDY2. In this embodiment, each cooling fan 21A to 21D is configured to duty cycle control the current supplied to them. The process is similar in each of the following steps 150, 170, 190, 210, and 230.

[0033] On the other hand, in step 140, the ECU 20 determines whether the charge level difference ΔSOC is greater than or equal to "-20 (%)" and less than "-10 (%)". If the result of this determination is positive, that is, if the second charge level SOC2 is somewhat larger than the first charge level SOC1, the ECU 20 proceeds to step 150. If the result of this determination is negative, the ECU 20 proceeds to step 160.

[0034] In step 150, ECU20 sets the reference fan duty BFDY as the first fan duty FDY1. ECU20 also sets the second fan duty FDY2 as the value obtained by adding "10 (%)" to the reference fan duty BFDY. That is, in order to lower the charge level SOC2 of the second battery 13B, which has a charge level SOC greater than that of the first battery 13A, the second fan duty FDY2 is made somewhat larger than the first fan duty FDY1. After this, ECU20 terminates the process.

[0035] Meanwhile, in step 160, the ECU 20 determines whether the charge level difference ΔSOC is less than "-20 (%)". If this determination is positive, that is, if the second charge level SOC2 is greater than the first charge level SOC1, the ECU 20 proceeds to step 170; otherwise, the ECU 20 proceeds to step 180.

[0036] In step 170, ECU20 sets the reference fund duty cycle BFDY as the first fund duty cycle FDY1. ECU20 also sets the second fund duty cycle FDY2 as the value obtained by adding "20 (%)" to the reference fund duty cycle BFDY. That is, in order to further reduce the charge level SOC2 of the second battery 13B, which has a charge level SOC higher than that of the first battery 13A, the second fund duty cycle FDY2 is made even larger than the first fund duty cycle FDY1. After this, ECU20 terminates the process.

[0037] Meanwhile, in step 180, the ECU 20 determines whether the charge level difference ΔSOC is greater than or equal to "0 (%)" and less than or equal to "10 (%)". If the result of this determination is positive, that is, if the first charge level SOC1 is slightly greater than the second charge level SOC2, the ECU 20 proceeds to step 190. If the result of this determination is negative, the ECU 20 proceeds to step 200.

[0038] In step 190, ECU20 sets the reference fan duty BFDY as the first fan duty FDY1. ECU20 also sets the reference fan duty BFDY as the second fan duty FDY2. That is, both the first fan duty FDY1 and the second fan duty FDY2 are set to the reference fan duty BFDY in order to slightly reduce the charge level SOC1 of the first battery 13A and the charge level SOC2 of the second battery 13B to roughly the same level. After this, ECU20 terminates the process.

[0039] Meanwhile, in step 200, the ECU 20 determines whether the charge level difference ΔSOC is greater than "10 (%)" and less than "20 (%)". If this determination is positive, that is, if the first charge level SOC1 is somewhat greater than the second charge level SOC2, the ECU 20 proceeds to step 210; otherwise, the ECU 20 proceeds to step 220.

[0040] In step 210, ECU20 sets the first fan duty FDY1 as the value obtained by adding "10 (%)" to the reference fan duty BFDY. ECU20 also sets the reference fan duty BFDY as the second fan duty FDY2. In other words, to lower the charge level SOC1 of the first battery 13A, which has a charge level SOC greater than that of the second battery 13B, the first fan duty FDY1 is made somewhat larger than the second fan duty FDY2. After this, ECU20 terminates the process.

[0041] Meanwhile, in step 220, the ECU 20 determines whether the charge level difference ΔSOC is greater than "20 (%)". If the result of this determination is positive, that is, if the first charge level SOC1 is even greater than the second charge level SOC2, the ECU 20 proceeds to step 230. If the result of this determination is negative, the subsequent processing is terminated.

[0042] In step 230, ECU20 sets the first fan duty FDY1 as the value obtained by adding "20 (%)" to the reference fan duty BFDY. ECU20 also sets the reference fan duty BFDY as the second fan duty FDY2. In other words, in order to further reduce the charge level SOC1 of the first battery 13A, which has a charge level SOC that is even higher than that of the second battery 13B, the first fan duty FDY1 is made even larger than the second fan duty FDY2. After that, ECU20 terminates the process.

[0043] Figure 3 shows the relationship between the first fund duty cycle FDY1 and the second fund duty cycle FDY2 in relation to the difference in magnitude between the first charge level SOC1 and the second charge level SOC2 in the above control.

[0044] As shown in Figure 3, in this embodiment, if the second charge level SOC2 is higher than the first charge level SOC1 and the charge level difference ΔSOC is greater than a predetermined value (10%), the second fund duty FDY2 is increased from the reference fund duty BFDY, and the first fund duty FDY1 is set to the reference fund duty BFDY.

[0045] In contrast, as shown in Figure 3, if the first charge level SOC1 is higher than the second charge level SOC2, and the difference in charge levels ΔSOC is greater than a predetermined value (10%), the first fund duty FDY1 is increased from the reference fund duty BFDY, and the second fund duty FDY2 is set to the reference fund duty BFDY.

[0046] On the other hand, as shown in Figure 3, if the first charge level SOC1 and the second charge level SOC2 are the same, or if the difference between them ΔSOC is less than a predetermined value, then both the first fund duty FDY1 and the second fund duty FDY2 are set to the reference fund duty BFDY.

[0047] Furthermore, as shown in Figure 3, as the charge level difference ΔSOC increases to "10%" and "20%", the fan duty cycles FDY1 and FDY2 (current values) supplied to each cooling fan 21A to 21D are increased to "10%" and "20%", respectively.

[0048] According to the above control, the ECU 20 is configured to measure the charge levels of the two batteries 13A and 13B, namely the first charge level SOC1 and the second charge level SOC2, respectively. The ECU 20 then controls the current supplied from the two batteries 13A and 13B to the respective cooling fans 21A to 21D connected to them, so that the difference between the first charge level SOC1 and the second charge level SOC2, namely the charge level difference ΔSOC, is minimized.

[0049] Furthermore, according to the above control, if the charge rate difference ΔSOC is greater than a predetermined value (10%), the ECU 20 increases the fan duty cycles FDY1 and FDY2 (current values) supplied to the cooling fans 21A to 21D connected to batteries 13A and 13B with higher measured charge rates SOC1 and SOC2, compared to the reference fan duty cycle BFDY (reference value). The fan duty cycles FDY2 and FDY1 (current values) supplied to the cooling fans 21A to 21D connected to batteries 13B and 13A with lower measured charge rates SOC1 and SOC2 are set as the reference fan duty cycle BFDY (reference value).

[0050] Furthermore, according to the above control, the ECU 20 calculates the charge level difference ΔSOC for the two batteries 13A and 13B, and changes the magnitude of the increase in the fan duty cycles FDY1 and FDY2 (current values) supplied to each cooling fan 21A to 21D according to the charge level difference ΔSOC.

[0051] [Regarding the operation and effects of fuel cell systems] According to the configuration of the fuel cell system 1 of this embodiment described above, two identical cooling fans (21A, 21B) and (21C, 21D) are connected to each of the two batteries 13A and 13B. Therefore, when there is a difference in SOC between the two batteries 13A and 13B, the SOC of each battery 13A and 13B is adjusted by adjusting the power consumed by each cooling fan (21A, 21B) and (21C, 21D) according to that difference. Thus, in a fuel cell system 1 equipped with two batteries 13A and 13B, it is possible to suppress the narrowing of the control range of the SOC of each battery 13A and 13B by narrowing the difference in SOC between the two batteries 13A and 13B.

[0052] According to the configuration of this embodiment, when there is a difference in State of Charge (SOC) between the two batteries 13A and 13B, the power consumed by each cooling fan (21A, 21B) and (21C, 21D) from each battery 13A and 13B is adjusted according to the difference in charge rate ΔSOC, and the SOC of each battery 13A and 13B is adjusted accordingly. Therefore, the power consumption by each cooling fan (21A, 21B) and (21C, 21D) can be adjusted according to the difference in SOC between the two batteries 13A and 13B.

[0053] Furthermore, according to the configuration of this embodiment, when the charge rate difference ΔSOC exceeds a predetermined value (10%), the fan duty cycles FDY1 and FDY2 (current values) supplied to each cooling fan (21A, 21B) and (21C, 21D) connected to batteries 13A and 13B with higher SOCs increase compared to the reference fan duty cycle BFDY (reference value). Also, the fan duty cycles FDY2 and FDY1 supplied to each cooling fan (21C, 21D) and (21A, 21B) connected to batteries 13B and 13A with lower SOCs become the reference fan duty cycle BFDY. Therefore, by increasing the power consumption of batteries 13A and 13B with higher SOCs, the difference in charge rates between the two batteries 13A and 13B can be narrowed.

[0054] Furthermore, according to the configuration of this embodiment, the increase in each fan duty FDY1, FDY2 supplied to each cooling fan (21A, 21B), (21C, 21D) changes according to the charge level difference ΔSOC between the two batteries 13A and 13B. Therefore, the difference in charge levels between the two batteries 13A and 13B can be efficiently narrowed according to the difference in charge levels.

[0055] <Second Embodiment> Next, the second embodiment will be described in detail with reference to Figure 4. In the following description, components equivalent to those in the first embodiment will be denoted by the same reference numerals and their descriptions will be omitted, with the focus being on the differences.

[0056] Figure 4 shows a schematic configuration diagram of the fuel cell system 1 according to this embodiment. As shown in Figure 4, this embodiment differs from the first embodiment mainly in the number of batteries, fan drivers, and cooling fans that constitute the fuel cell system 1. Specifically, the fuel cell system 1 of this embodiment includes a third battery 13C in addition to the first and second batteries 13A and 13B. It also includes a third fan driver 15C in addition to the first and second fan drivers 15A and 15B. Furthermore, it includes fifth and sixth cooling fans 21E and 21F in addition to the first to fourth cooling fans 21A to 21D.

[0057] Then, the same number (2) of cooling fans 21E and 21F as the others are connected to the newly added third battery 13C. The ECU 20 is configured to control the fifth and sixth cooling fans 21E and 21F via the third fan driver 15C. The ECU 20 is also configured to measure the charge level of the third battery 13C (third charge level SOC3). Based on the three measured charge levels SOC1, SOC2, and SOC3, the ECU 20 controls the current supplied to each cooling fan 21A to 21F via each fan driver 15A to 15C. The content of the "cooling fan control" in this embodiment can be similar to the flowchart shown in Figure 2.

[0058] [Regarding the operation and effects of fuel cell systems] Therefore, although the number of batteries and the like differs, the fuel cell system 1 of this embodiment can obtain the same operation and effects as the first embodiment.

[0059] <Another embodiment> 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.

[0060] In the embodiments described above, the fuel cell system 1 was provided in the case of being installed in an electric vehicle, but it is also possible to provide the fuel cell system in the case of being installed in a vehicle other than an electric vehicle.

[0061] This disclosed technology can be used, for example, in fuel cell systems installed in electric vehicles. [Explanation of symbols]

[0062] 1. Fuel cell system 11 FC Stack (Fuel Cell) 13A Battery 1 13B Second Battery 13C Third Battery 20 ECU (Control Unit) 21A First cooling fan (electric auxiliary) 21B Second cooling fan (electric auxiliary) 21C Third Cooling Fan (Electric Auxiliary) 21D 4th Cooling Fan (Electric Auxiliary) 21E Fifth cooling fan (electric auxiliary) 21F 6th Cooling Fan (Electric Auxiliary) SOC1 First charge level (measured charge level) SOC2 Second charge level (measured charge level) SOC3 Third charge level (measured charge level) ΔSOC (Surface Charge Level) difference (difference between multiple charge levels) BFDY Standard Fund Duty (Standard Value) FDY1 First Fund Duty (Current Value) FDY2 Second Fund Duty Cycle (Current Value)

Claims

1. In a fuel cell system comprising a fuel cell and a plurality of batteries for charging the electricity generated by the fuel cell, wherein the plurality of batteries are set to the same specified voltage and connected in series, and the system does not include a DC-DC converter, The fuel cell system further comprises a plurality of electric auxiliary devices that contribute to the operation of the fuel cell system, Each of the multiple batteries is connected to the same number of the aforementioned electric auxiliary devices. A fuel cell system characterized by the following features.

2. In the fuel cell system according to claim 1, The system further comprises a control device for controlling multiple aforementioned electric auxiliary devices, The control device is configured to measure the charge rate of each of the multiple batteries and to control the current supplied from the multiple batteries to each of the electric auxiliary devices connected to them so as to minimize the difference between the measured charge rates. A fuel cell system characterized by the following features.

3. In the fuel cell system according to claim 2, If the difference in charge levels exceeds a predetermined value, the control device increases the current supplied to the electric auxiliary device connected to the battery with the higher measured charge level above a reference value, and sets the current supplied to the electric auxiliary device connected to the battery with the lower measured charge level to the reference value. A fuel cell system characterized by the following features.

4. In the fuel cell system according to claim 3, The control device changes the magnitude of the increase in the current value supplied to the electric auxiliary equipment according to the difference in the charge level. A fuel cell system characterized by the following features.

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