JP7364480B2 - fuel cell system - Google Patents

Description

The present invention relates to a fuel cell system.

Conventionally, fuel cell vehicles have been equipped with a fuel cell system equipped with a fuel cell that generates electricity to drive the fuel cell vehicle, but multiple power sources are required depending on the voltage requirements of the power supply destination. A system may be prepared. To achieve this, it is conceivable to connect a plurality of DC/DC converters in parallel to the fuel cell.

For example, a power supply system as a fuel cell system described in Patent Document 1 includes a fuel cell and a plurality of DC/DC converters. In the above power supply system, two DC/DC converters are connected to the fuel cell. For example, one of the two DC/DC converters is electrically connected to a motor as a load that drives the fuel cell vehicle, and the other of the two DC/DC converters is electrically connected to an auxiliary system. The other of the two DC/DC converters is connected to the fuel cell in parallel with one of the two DC/DC converters.

Japanese Patent Application Publication No. 2011-36101

By the way, the DC/DC converter may include a capacitor on the input side inside the DC/DC converter. When two DC/DC converters are provided with capacitors on their internal input sides, the two DC/DC converters transfer the voltage of the power stored in the capacitors to the power supply destination, such as the load or auxiliary equipment system. Convert to the required voltage.

Since the two DC/DC converters are connected in parallel to the fuel cell, the capacitors on the input side inside the two DC/DC converters are electrically connected to each other. Therefore, the charge of the capacitor on the input side of one of the two DC/DC converters may be drawn toward the other of the two DC/DC converters, or the charge of the capacitor on the input side of the other of the two DC/DC converters may be There is a possibility that it may be pulled toward one of the two DC/DC converters. In other words, since the power stored in the capacitor on the input side inside the DC/DC converter from which the charge is drawn is insufficient, the DC/DC converter from which the charge is drawn will use the power generated by the fuel cell. It may become impossible to convert the voltage of the fuel cell system, making it difficult to stabilize the driving state of the fuel cell system.

The present invention has been made by focusing on the problems existing in the conventional technology, and its purpose is to provide a fuel cell system that can stabilize the driving state.

A fuel cell system that solves the above problems includes a fuel cell, a first DC/DC converter that converts the voltage of the electric power generated by the fuel cell into a first voltage and has a first capacitor on the input side thereof, and a second DC/DC converter that is connected in parallel with the first DC/DC converter to the fuel cell, converts the voltage of the power generated by the fuel cell into a second voltage, and has a second capacitor on the internal input side; A fuel cell system comprising: a first wiring connected to the fuel cell; and a second wiring connected to the input side of the first DC/DC converter and electrically connected to the first capacitor. a first backflow prevention section electrically connected to the first wiring and the second wiring to prevent the electric charge of the first capacitor from flowing back toward the first wiring; 3 wiring, a fourth wiring electrically connected to the second capacitor while being connected to the input side of the second DC/DC converter, and a fourth wiring electrically connected to the third wiring and the fourth wiring, and the fourth wiring electrically connected to the third wiring and the fourth wiring, A second backflow prevention section that prevents the charge of the second capacitor from flowing back toward the third wiring is provided.

According to this, the movement of charges between the first capacitor provided on the input side inside the first DC/DC converter and the second capacitor provided on the input side inside the second DC/DC converter is caused by the first reverse flow. This is suppressed by the suppressing section and the second backflow suppressing section. Therefore, the power stored in the first capacitor and the second capacitor is prevented from running out, and the voltage of the power generated by the fuel cell cannot be converted. Therefore, the driving state of the fuel cell system can be stabilized.

In the above fuel cell system, the first backflow prevention section is a diode that only allows current to flow from the first wiring toward the second wiring, and the second backflow prevention section is a diode that allows electricity to flow only from the first wiring to the second wiring. It is preferable that the diode is a diode that only allows current to flow toward the fourth wiring.

According to this, it is possible to suppress the current from the first capacitor to the first wiring while allowing the current to flow from the first wiring to the second wiring, and to suppress the current from the first wiring to the fourth wiring while allowing the current to flow from the third wiring to the fourth wiring. Current flowing from the second capacitor to the third wiring can be suppressed. Therefore, the driving state of the fuel cell system can be suitably stabilized using a single diode.

In the above fuel cell system, the first DC/DC converter and the second DC/DC converter are switching regulators, and the first power storage device connected to the output side of the first DC/DC converter and the second DC/DC converter are switching regulators. a second power storage device connected to the output side of the DC converter; a charging rate detection unit that detects charging rates of each of the first power storage device and the second power storage device; and the first DC/DC converter based on the charging rate. and a control device that controls the second DC/DC converter, and a control unit that controls the conduction state of switching elements included in each of the first DC/DC converter and the second DC/DC converter based on a command output from the control device. further comprising: the control device executes high potential avoidance control to prevent the voltage of the fuel cell from exceeding a predetermined voltage; and in the high potential avoidance control, the charging rate of the first power storage device is a first charging control that changes the command output to the control unit of the first DC/DC converter according to the charging rate of the second power storage device; It is preferable to perform a second charging control that changes the command to be output.

A fuel cell is formed by stacking a plurality of cells. In fuel cells, when the amount of power generation increases, the voltage applied to each cell forming the fuel cell tends to decrease, and when the amount of power generation decreases, the voltage applied to each cell forming the fuel cell tends to increase. There is. Fuel cells generally stop driving when there is no demand for output, but when the fuel cell stops driving, the voltage of the cells forming the fuel cell increases, causing the fuel cell to deteriorate. There is a possibility that

In this respect, according to this, the control device implements high potential avoidance control. In the high potential avoidance control, the control device changes the command output to the control unit according to the charging rate of the first power storage device, and the control device changes the command output to the control unit according to the charging rate of the second power storage device. and second charging control that changes the command to be output. That is, even if the driving of the fuel cell is stopped, the control device changes the driving of the first DC/DC converter and the second DC/DC converter according to the respective charging rates of the first power storage device and the second power storage device, and By charging the first power storage device and the second power storage device with the power generated by the battery, the voltage of the fuel cell is prevented from exceeding a predetermined voltage. Therefore, deterioration of the fuel cell can be suppressed.

According to this invention, the driving state can be stabilized.

FIG. 1 is a block diagram showing the configuration of a fuel cell system. A schematic diagram showing the configuration of a first DC/DC converter and a second DC/DC converter. FIG. 3 is a schematic diagram showing a control flow of first charging control of the fuel cell system. FIG. 3 is a schematic diagram showing a control flow of second charging control of the fuel cell system. The schematic diagram which showed the example of a change of a 1st DC/DC converter and a 2nd DC/DC converter. The schematic diagram which showed the example of a change of a 1st backflow prevention part and a 2nd backflow prevention part.

Hereinafter, embodiments embodying a fuel cell system will be described with reference to FIGS. 1 to 4.
As shown in FIG. 1, a fuel cell system 1 of this embodiment is applied to industrial vehicles such as forklifts and towing tractors. The fuel cell system 1 includes a fuel cell 50. The fuel cell 50 is a stack formed by laminating a plurality of cells. The cell is, for example, a polymer electrolyte fuel cell. The fuel cell 50 generates electricity through a chemical reaction between fuel gas and oxidant gas. In this embodiment, power generation is performed using hydrogen gas as a fuel gas and oxygen in the air as an oxidant gas. Note that the voltage value of the electric power generated by the fuel cell 50 is, for example, 140V.

The fuel cell system 1 includes three power supply systems. The three power supply systems have different required voltages. The three power supply systems are respectively referred to as a first system 10, a second system 20, and a third system 30.

The first system 10 includes a load 11, a first power storage device 12, a first DC/DC converter 13, a first diode 41, a first positive wiring Lp11 for the first system, and a second positive wiring for the first system. Lp12, a third positive wiring Lp13 for the first system, a first negative wiring Ln11 for the first system, and a second negative wiring Ln12 for the first system.

The load 11 includes a travel motor 11a that generates a driving force for the towing tractor to travel, and an inverter 11b that drives the travel motor 11a. The traveling motor 11a and the inverter 11b are electrically connected. The load 11 is driven at 80V, for example.

The first power storage device 12 is a secondary battery, and uses a lithium ion capacitor, for example. The first power storage device 12 has a function of storing power for driving the driving motor 11a. The first power storage device 12 can be charged with power having a voltage value of 80V, for example.

The first positive electrode wiring Lp11 for the first system is connected to the positive electrode of the fuel cell 50. The second positive wiring Lp12 for the first system is connected to the positive input terminal 13a of the first DC/DC converter 13. One end of the first negative electrode wiring Ln11 for the first system is connected to the negative electrode of the fuel cell 50, and the other end is connected to the negative electrode input terminal 13b of the first DC/DC converter 13. The first diode 41 is provided between the first positive wiring Lp11 for the first system and the second positive wiring Lp12 for the first system. The first diode 41 is electrically connected to the first positive wiring Lp11 for the first system and the second positive wiring Lp12 for the first system. The first diode 41 is a diode that only allows current to flow from the first positive wiring Lp11 for the first system to the second positive wiring Lp12 for the first system.

The third positive wiring Lp13 for the first system connects the positive output terminal 13c of the first DC/DC converter 13 and the positive input terminal 12a of the first power storage device 12. The third positive wiring Lp13 for the first system connects the positive output terminal 13c of the first DC/DC converter 13 and the positive input terminal 11c of the load 11. The positive input terminal 12a of the first power storage device 12 and the positive input terminal 11c of the load 11 are electrically connected by a third positive wiring Lp13 for the first system. Note that the third positive electrode wiring Lp13 for the first system may be composed of a plurality of wirings, or may be composed of one wiring.

The second negative wiring Ln12 for the first system connects the negative output terminal 13d of the first DC/DC converter 13 and the negative input terminal 12b of the first power storage device 12. The second negative wiring Ln12 for the first system connects the negative output terminal 13d of the first DC/DC converter 13 and the negative input terminal 11d of the load 11. The negative input terminal 12b of the first power storage device 12 and the negative input terminal 11d of the load 11 are electrically connected by the second negative wiring Ln12 for the first system. The first power storage device 12 is connected to the output side of the first DC/DC converter 13 by a third positive wiring Lp13 for the first system and a second negative wiring Ln12 for the first system. Note that the second negative electrode wiring Ln12 for the first system may be composed of a plurality of wirings, or may be composed of one wiring.

The second system 20 includes a first auxiliary machine 21, a second power storage device 22, a second DC/DC converter 23, a second diode 42, a first positive electrode wiring Lp21 for the second system, and a first positive electrode wiring Lp21 for the second system. It has two positive electrode wiring Lp22, a third positive electrode wiring Lp23 for the second system, a first negative electrode wiring Ln21 for the second system, and a second negative electrode wiring Ln22 for the second system.

The first auxiliary machine 21 includes, for example, a solenoid valve and an electric compressor that assist the driving of the fuel cell 50. The solenoid valve is provided in a hydrogen supply pipe that connects a hydrogen tank (not shown) and the fuel cell 50, and has a function of opening and closing the hydrogen supply pipe. The electric compressor has a function of supplying air containing oxygen to the fuel cell 50 in a compressed state. The first auxiliary machine 21 is driven by, for example, 48V.

The second power storage device 22 is a secondary battery, and uses a lithium ion capacitor, for example. The second power storage device 22 has a function of storing power for driving the first auxiliary device 21 . The second power storage device 22 can be charged with power having a voltage value of 48V, for example.

The first positive wiring Lp21 for the second system is connected to the first positive wiring Lp11 for the first system. The second positive wiring Lp22 for the second system is connected to the positive input terminal 23a of the second DC/DC converter 23. One end of the first negative wiring Ln21 for the second system is connected to the first negative wiring Ln11 for the first system, and the other end is connected to the negative input terminal 23b of the second DC/DC converter 23. The second diode 42 is provided between the first positive wiring Lp21 for the second system and the second positive wiring Lp22 for the second system. The second diode 42 is electrically connected to the first positive wiring Lp21 for the second system and the second positive wiring Lp22 for the second system. The second diode 42 is a diode that only allows current to flow from the first positive wiring Lp21 for the second system to the second positive wiring Lp22 for the second system.

The third positive wiring Lp23 for the second system connects the positive output terminal 23c of the second DC/DC converter 23 and the positive input terminal 22a of the second power storage device 22. The third positive wiring Lp23 for the second system connects the positive output terminal 23c of the second DC/DC converter 23 and the positive input terminal 21a of the first auxiliary machine 21. The positive input end 22a of the second power storage device 22 and the positive input end 21a of the first auxiliary device 21 are electrically connected by a third positive wiring Lp23 for the second system. Note that the third positive electrode wiring Lp23 for the second system may be composed of a plurality of wirings, or may be composed of one wiring.

The second negative wiring Ln22 for the second system connects the negative output end 23d of the second DC/DC converter 23 and the negative input end 22b of the second power storage device 22. The second negative wiring Ln22 for the second system connects the negative output terminal 23d of the second DC/DC converter 23 and the negative input terminal 21b of the first auxiliary machine 21. The negative input terminal 22b of the second power storage device 22 and the negative input terminal 21b of the first auxiliary machine 21 are electrically connected by a second negative wiring Ln22 for the second system. The second power storage device 22 is connected to the output side of the second DC/DC converter 23 by a third positive wiring Lp23 for the second system and a second negative wiring Ln22 for the second system. Note that the second negative electrode wiring Ln22 for the second system may be composed of a plurality of wirings, or may be composed of one wiring.

The third system 30 includes a second auxiliary machine 31, a third power storage device 32, a third DC/DC converter 33, a first positive wiring Lp31 for the third system, and a second positive wiring Lp32 for the third system. It has a first negative electrode wiring Ln31 for the third system and a second negative electrode wiring Ln32 for the third system.

The second auxiliary machine 31 includes, for example, an air conditioner, a car navigation system, and lights, and an FCECU 34 as a control device that controls the air conditioner, car navigation system, lights, and first auxiliary machine 21 . The second auxiliary machine 31 is driven by, for example, 12V.

The third power storage device 32 is a secondary battery, and uses a lithium ion capacitor, for example. The third power storage device 32 has a function of storing power for driving the second auxiliary machine 31. The third power storage device 32 can be charged with power having a voltage value of 12V, for example.

One end of the first positive wiring Lp31 for the third system is connected to the third positive wiring Lp23 for the second system, and the other end is connected to the positive input terminal 33a of the third DC/DC converter 33. The second positive wiring Lp32 for the third system connects the positive output end 33c of the third DC/DC converter 33 and the positive input end 32a of the third power storage device 32. The second positive wiring Lp32 for the third system connects the positive output end 33c of the third DC/DC converter 33 and the positive input end 31a of the second auxiliary machine 31. The positive input end 32a of the third power storage device 32 and the positive input end 31a of the second auxiliary machine 31 are electrically connected by the second positive wiring Lp32 for the third system. Note that the second positive electrode wiring Lp32 for the third system may be composed of a plurality of wirings, or may be composed of one wiring.

One end of the first negative wiring Ln31 for the third system is connected to the second negative wiring Ln22 for the second system, and the other end is connected to the negative input terminal 33b of the third DC/DC converter 33. The second negative electrode wiring Ln32 for the third system connects the negative output end 33d of the third DC/DC converter 33 and the negative input end 32b of the third power storage device 32. The second negative wiring Ln32 for the third system connects the negative output end 33d of the third DC/DC converter 33 and the negative input end 31b of the second auxiliary machine 31. The negative input terminal 32b of the third power storage device 32 and the negative input terminal 31b of the second auxiliary machine 31 are electrically connected by the first negative wiring Ln31 for the third system. Note that the second negative electrode wiring Ln32 for the third system may be composed of a plurality of wirings, or may be composed of one wiring.

The fuel cell system 1 includes a first charging rate detector 61 as a charging rate detector that detects a charging rate SOC1 of the first power storage device 12, and a charging rate detector 61 as a charging rate detector that detects the charging rate SOC2 of the second power storage device 22. A second charging rate detection section 62 is provided. The charging rate SOC1 detected by the first charging rate detector 61 and the charging rate SOC2 detected by the second charging rate detector 62 are input to the FCECU 34. The FCECU 34 outputs a first command S1, a second command S2, or a third command S3 to the first DC/DC converter 13 for controlling the first DC/DC converter 13 based on the input charging rate SOC1. The FCECU 34 outputs a first command S1, a second command S2, or a third command S3 to the second DC/DC converter 23 for controlling the second DC/DC converter 23 based on the input charging rate SOC2.

Next, the configurations of the first DC/DC converter 13 and the second DC/DC converter 23 will be described in detail.
As shown in FIG. 2, inside the first DC/DC converter 13, the first DC/DC converter 13 has a positive electrode bus 14 and a negative electrode bus 15. Inside the first DC/DC converter 13, the positive bus 14 connects the positive input end 13a and the positive output end 13c of the first DC/DC converter 13. Inside the first DC/DC converter 13, the negative bus 15 connects the negative input end 13b and the negative output end 13d of the first DC/DC converter 13. The positive electrode bus 14 is electrically connected to the second positive wiring Lp12 for the first system via the positive input terminal 13a of the first DC/DC converter 13, and is electrically connected to the second positive electrode wiring Lp12 for the first system through the positive output terminal 13c of the first DC/DC converter 13. and is electrically connected to the third positive electrode wiring Lp13 for the first system. The negative electrode bus 15 is electrically connected to the first negative wiring Ln11 for the first system via the negative input terminal 13b of the first DC/DC converter 13, and is electrically connected to the first negative electrode wiring Ln11 through the negative output terminal 13d of the first DC/DC converter 13. and is electrically connected to the second negative electrode wiring Ln12 for the first system.

The first DC/DC converter 13 has a first relay wiring 16, a second relay wiring 17, and a third relay wiring 18 that connect the positive electrode bus 14 and the negative electrode bus 15. The first relay wiring 16 , the second relay wiring 17 , and the third relay wiring 18 are connected inside the first DC/DC converter 13 from the input ends 13 a and 13 b of the first DC/DC converter 13 to the first DC/DC converter 13 . They are arranged in this order toward the output ends 13c and 13d. The first relay wiring 16 is provided inside the first DC/DC converter 13 near the input ends 13a and 13b of the first DC/DC converter 13. The third relay wiring 18 is provided inside the first DC/DC converter 13 near the output ends 13c and 13d of the first DC/DC converter 13. The second relay wiring 17 is provided inside the first DC/DC converter 13 between the first relay wiring 16 and the third relay wiring 18.

The first DC/DC converter 13 includes two capacitors Cd, one switching element Sw, one coil Co, one diode Di, one voltage sensor V, and one control section 19. There is. The two capacitors Cd are arranged on the first relay wiring 16 and the third relay wiring 18, respectively. The switching element Sw is arranged in a portion of the positive electrode bus bar 14 sandwiched between the first relay wiring 16 and the second relay wiring 17. The coil Co is arranged in a portion of the positive electrode bus bar 14 sandwiched between the second relay wiring 17 and the third relay wiring 18. A smoothing circuit of the first DC/DC converter 13 is formed by the coil Co and the capacitor Cd provided on the third relay wiring 18. The diode Di is arranged on the second relay wiring 17. The diode Di is arranged to allow only a current from the negative bus 15 side of the second relay wiring 17 toward the positive bus 14 side.

Inside the first DC/DC converter 13, the first relay wiring 16 side is the input side of the first DC/DC converter 13 with the second relay wiring 17 as a reference, and the third relay wiring 18 side is the input side of the first DC/DC converter 13 with the second relay wiring 17 as a reference. is the output side of the first DC/DC converter 13. If the capacitor Cd provided on the first relay wiring 16 inside the first DC/DC converter 13 is the first capacitor Cd1, the first capacitor Cd1 is the first DC/DC converter inside the first DC/DC converter 13. They are arranged near the input ends 13a and 13b of the DC converter 13. The first capacitor Cd1 is provided on the input side inside the first DC/DC converter 13.

The voltage sensor V is a sensor that detects the voltage of the power stored in the first capacitor Cd1. Since the first relay wiring 16, the positive bus bar 14, and the second positive wiring Lp12 for the first system are electrically connected, the first capacitor Cd1 and the second positive wiring Lp12 for the first system are electrically connected. has been done.

The control unit 19 includes a memory (not shown) and a microcomputer (not shown) that executes a program stored in the memory. The memory of the control unit 19 stores a program that calculates the on/off duty ratio of the switching element Sw. Then, the microcomputer of the control unit 19 controls the switching element Sw based on the duty ratio. The first DC/DC converter 13 configured in this manner is a switching regulator that has a function of stepping down the power generated by the fuel cell 50. The above duty ratio is up to 80V, which is the voltage that drives the voltage of the electric power generated by the fuel cell 50 to the load 11 connected to the third positive electrode wiring Lp13 for the first system and the second negative electrode wiring Ln12 for the first system. It is set from the perspective of lowering blood pressure. The first DC/DC converter 13 converts the voltage of the electric power generated by the fuel cell 50 to 80V, and has a first capacitor Cd1 on the internal input side. Note that 80V, which is the voltage that drives the load 11, is an example of the first voltage.

The second DC/DC converter 23 has the same configuration as the first DC/DC converter 13. Therefore, only the configuration different from the first DC/DC converter 13 will be described below.
The second DC/DC converter 23 is connected to the fuel cell 50 in parallel with the first DC/DC converter 13 .

The positive electrode bus 14 of the second DC/DC converter 23 is electrically connected to the second positive wiring Lp22 for the second system via the positive input terminal 23a of the second DC/DC converter 23. It is electrically connected to the third positive electrode wiring Lp23 for the second system via the positive electrode output end 23c. The negative electrode bus 15 is electrically connected to the first negative wiring Ln21 for the second system via the negative input terminal 23b of the second DC/DC converter 23, and is electrically connected to the negative electrode wiring Ln21 through the negative output terminal 23d of the second DC/DC converter 23. and is electrically connected to the second negative electrode wiring Ln22 for the second system.

Inside the second DC/DC converter 23, with the second relay wiring 17 as a reference, the first relay wiring 16 side is the input side of the second DC/DC converter 23, and the second relay wiring 17 is the input side of the third relay wiring 18. is the output side of the second DC/DC converter 23. Inside the second DC/DC converter 23, if the capacitor Cd provided on the first relay wiring 16 is the second capacitor Cd2, then the second capacitor Cd2 is the second DC/DC converter inside the second DC/DC converter 23. They are arranged near the input ends 23a and 23b of the DC converter 23. The second capacitor Cd2 is provided on the input side inside the second DC/DC converter 23.

The voltage sensor V is a sensor that detects the voltage of the power stored in the second capacitor Cd2. Since the first relay wiring 16, the positive bus bar 14, and the second positive wiring Lp22 for the second system are electrically connected, the second capacitor Cd2 and the second positive wiring Lp22 for the second system are electrically connected. has been done.

The duty ratio calculated by the control unit 19 of the second DC/DC converter 23 connects the voltage of the electric power generated by the fuel cell 50 to the third positive wiring Lp23 for the second system and the second negative wiring Ln22 for the second system. The voltage is set from the viewpoint of lowering the voltage to 48V, which is the voltage that drives the first auxiliary machine 21. The second DC/DC converter 23 converts the voltage of the electric power generated by the fuel cell 50 to 48V, and has a second capacitor Cd2 on the internal input side. Note that 48V, which is the voltage for driving the first auxiliary device 21, is an example of the second voltage.

In the configuration of the fuel cell system 1 described above, the first positive electrode wiring Lp11 for the first system is an example of the first wiring, the second positive electrode wiring Lp12 for the first system is an example of the second wiring, and the second positive electrode wiring Lp12 for the first system is an example of the second wiring. The first positive electrode wiring Lp21 is an example of the third wiring, and the second positive electrode wiring Lp22 for the second system is an example of the fourth wiring. Therefore, the first diode 41 functions as a first backflow prevention section that prevents the charge of the first capacitor Cd1 from flowing back toward the first positive wiring Lp11 for the first system. Further, the second diode 42 functions as a second backflow prevention section that prevents the charge of the second capacitor Cd2 from flowing back toward the first positive wiring Lp21 for the second system. Note that the configuration of the third DC/DC converter 33 is similar to that of the first DC/DC converter 13 and the second DC/DC converter 23. The third DC/DC converter 33 is connected to the output side of the second DC/DC converter 23. The third DC/DC converter 33 is connected in parallel with the first auxiliary machine 21 to the second DC/DC converter 23 . Further, the third DC/DC converter 33 is connected in parallel to the second power storage device 22 with respect to the second DC/DC converter 23 . The third DC/DC converter 33 has a function of converting 48V, which is the voltage at which the first auxiliary device 21 is driven, to 12V, which is the voltage at which the second auxiliary device 31 is driven. 12V, which is the voltage at which the second auxiliary machine 31 is driven, is an example of the third voltage.

The first command S1, second command S2, or third command S3 output by the FCECU 34 is input to the control unit 19 of each of the first DC/DC converter 13 and the second DC/DC converter 23. The control unit 19 of the first DC/DC converter 13 controls the switching element of the first DC/DC converter 13 based on the input commands S1, S2, S3 and the voltage V1 of the first capacitor Cd1 detected by the voltage sensor V. The on/off duty ratio of Sw is calculated, and the switching element Sw is controlled based on the duty ratio. Similarly, the control unit 19 of the second DC/DC converter 23 controls the second DC/DC converter 23 based on the input commands S1, S2, S3 and the voltage V2 of the second capacitor Cd2 detected by the voltage sensor V. The on/off duty ratio of the switching element Sw is calculated, and the switching element Sw is controlled based on the duty ratio. That is, the FCECU 34 controls the first DC/DC converter 13 and the second DC/DC converter 23 based on the charging rates SOC1 and SOC2. The first DC/DC converter 13 and the second DC/DC converter 23 control the switching elements Sw of the first DC/DC converter 13 and the second DC/DC converter 23 based on commands S1, S2, and S3 output from the FCECU 34, respectively. It has a control section 19 for controlling.

In the fuel cell 50, when the amount of power generation increases, the voltage applied to each cell forming the fuel cell decreases, and when the amount of power generation decreases, the voltage applied to each cell forming the fuel cell 50 increases. There is a tendency to The fuel cell 50 generally stops driving when there is no output request, but if the driving of the fuel cell 50 is stopped, the voltage of the cells forming the fuel cell 50 increases, There is a possibility that the fuel cell 50 may deteriorate. In this embodiment, control is performed to suppress deterioration of the fuel cell 50.

As shown in FIGS. 3 and 4, the fuel cell system 1 performs normal power generation control, high potential avoidance control, first charging control, and second charging control based on charging rates SOC1 and SOC2. The normal power generation control and the high potential avoidance control are carried out in common for the first system 10 and the second system 20, but the first charging control is the control that is carried out for the first system 10, and the 2 charging control is control performed on the second system 20. The normal power generation control and high potential avoidance control of the fuel cell system 1 will be explained according to FIGS. 3 and 4. The control flow of the first charge control in the fuel cell system 1 will be explained according to FIG. 3, and the control flow of the second charge control in the fuel cell system 1 will be explained according to FIG.

As shown in FIGS. 3 and 4, the FCECU 34 detects the charging rates SOC1 and SOC2 when there is no output request from the fuel cell 50, such as when the towing tractor is keyed on and the accelerator is not depressed. (Step S101). The FCECU 34 determines whether the charging rate SOC1 is greater than or equal to the first basic value Thb1 and the charging rate SOC2 is greater than or equal to the second basic value Thb2 (step S102). The FCECU 34 determines that when the charging rate SOC1 is not the first basic value Thb1 or more and the charging rate SOC2 is not the second basic value Thb2 or more (NO in step S102), that is, the charging rate SOC1 is not the first basic value Thb1 or more. If at least one of the determinations of whether or not there is, and the determination of whether or not the charging rate SOC2 is equal to or greater than the second basic value Thb2 is negative, normal power generation control is performed (step S103). The first basic value Thb1 is set to a charging rate SOC1 of the first power storage device 12 that can sufficiently supply power from the first power storage device 12 to the load 11 when the power generation amount of the fuel cell 50 is insufficient when the fuel cell system 1 is started. It is set. In addition, the first basic value Thb1 is determined by the second power storage device 22 that can sufficiently supply power from the second power storage device 22 to the first auxiliary device 21 when the amount of power generated by the fuel cell 50 is insufficient at the time of startup of the fuel cell system 1. The charging rate is set to SOC2. That is, the normal power generation control is a control that stores power in the first power storage device 12 and the second power storage device 22 that can supplement the power of the load 11 and the first auxiliary device 21 when the fuel cell system 1 is started. After performing the normal power generation control, unless the towing tractor is turned off, steps S101 and S102 are performed again.

When the charging rate SOC1 is equal to or higher than the first basic value Thb1 and the charging rate SOC2 is equal to or higher than the second basic value Thb2 (YES in step S102), the FCECU 34 performs high potential avoidance control (step S104). The high potential avoidance control is a control in which a high potential avoidance reference voltage, which is a threshold value of the output voltage, is set in advance so as not to deteriorate the fuel cell 50, and the high potential avoidance reference voltage is not exceeded. Note that the high potential avoidance reference voltage refers to a predetermined voltage in the claims. Further, the high potential avoidance reference voltage is set to a voltage value that does not cause deterioration of the fuel cell 50, after experimentally confirming the voltage value that would cause deterioration of the fuel cell 50.

In the high potential avoidance control, first charging control and second charging control are performed. Hereinafter, each of the first charging control and the second charging control will be explained in detail.
As shown in FIG. 3, in the first charging control, the FCECU 34 determines whether the charging rate SOC1 is greater than or equal to the first threshold Th1 (step S105). If the charging rate SOC1 is not equal to or greater than the first threshold Th1 (NO in step S105), the FCECU 34 outputs the first command S1 to the control unit 19 of the first DC/DC converter 13 (step S106). When the charging rate SOC1 is greater than or equal to the first threshold Th1 (YES in step S105), the FCECU 34 determines whether the charging rate SOC1 is greater than or equal to the second threshold Th2 (step S107). If the charging rate SOC1 is not equal to or higher than the second threshold Th2 (NO in step S107), the FCECU 34 outputs the second command S2 to the control unit 19 of the first DC/DC converter 13 (step S108). When the charging rate SOC1 is greater than or equal to the second threshold Th2 (YES in step S107), the FCECU 34 outputs the third command S3 to the control unit 19 of the first DC/DC converter 13 (step S109). That is, the FCECU 34 changes the command output to the control unit 19 of the first DC/DC converter 13 according to the charging rate SOC1 of the first power storage device 12. Note that the first threshold Th1 is a value larger than the first basic value Thb1. The second threshold Th2 is a larger value than the first threshold Th1. The first threshold Th1 and the second threshold Th2 are values that indicate in stages the state before the first power storage device 12 becomes fully charged.

As shown in FIG. 4, in the second charging control, the FCECU 34 determines whether the charging rate SOC2 is equal to or higher than the third threshold Th3 (step S111). If the charging rate SOC2 is not equal to or higher than the third threshold Th3 (NO in step S111), the FCECU 34 outputs the first command S1 to the control unit 19 of the second DC/DC converter 23 (step S112). If the charging rate SOC2 is greater than or equal to the third threshold Th3 (YES in step S111), the FCECU 34 determines whether the charging rate SOC2 is greater than or equal to the fourth threshold Th4 (step S113). If the charging rate SOC2 is not equal to or higher than the fourth threshold Th4 (NO in step S113), the FCECU 34 outputs the second command S2 to the control unit 19 of the second DC/DC converter 23 (step S114). If the charging rate SOC2 is equal to or greater than the fourth threshold Th4 (YES in step S113), the FCECU 34 outputs the third command S3 to the control unit 19 of the second DC/DC converter 23 (step S115). That is, FCECU 34 changes the command output to control unit 19 of second DC/DC converter 23 according to charging rate SOC2 of second power storage device 22. Note that the third threshold Th3 is a larger value than the second basic value Thb2. The fourth threshold Th4 is a larger value than the third threshold Th3. The third threshold Th3 and the fourth threshold Th4 are values that indicate in stages the state before the second power storage device 22 becomes fully charged.

Here, the first command S1 is such that the voltage of the first capacitor Cd1 and the second capacitor Cd2 is a value obtained by multiplying the first specified value Tc1, which is the voltage applied to the cells forming the fuel cell 50, by the number of stacked cells. This is a command to cause the control unit 19 to calculate the duty ratio so that . The first specified value Tc1 is higher than the cell voltage in normal power generation control. The first specified value Tc1 is, for example, 0.85V.

The second command S2 is such that the voltage of the first capacitor Cd1 and the second capacitor Cd2 becomes a value obtained by multiplying the second specified value Tc2, which is the voltage applied to the cells forming the fuel cell 50, by the number of stacked cells. This is a command to cause the control unit 19 to calculate the duty ratio. The second specified value Tc2 is a larger value than the first specified value Tc1. The second specified value Tc2 is, for example, 0.9V.

The third command S3 is such that the voltage of the first capacitor Cd1 and the second capacitor Cd2 becomes a value obtained by multiplying the third specified value Tc3, which is the voltage applied to the cells forming the fuel cell 50, by the number of stacked cells. This is a command to cause the control unit 19 to calculate the duty ratio. The third specified value Tc3 is a larger value than the second specified value Tc2. The third specified value Tc3 is, for example, 0.95V.

As shown in FIG. 3, in the first charging control, when the first command S1, the second command S2, or the third command S3 is output to the control unit 19 of the first DC/DC converter 13, the first DC/DC converter 13 The control unit 19 calculates a duty ratio for controlling the switching element Sw of the first DC/DC converter 13 (step S110).

As shown in FIGS. 2 and 3, in step S110, when the first command S1 is input to the control unit 19 of the first DC/DC converter 13, the control unit 19 of the first DC/DC converter 13 The voltage V1 of Cd1 is compared with the voltage of the fuel cell 50 calculated by multiplying the first specified value Tc1 by the number of stacked cells. If the voltage V1 of the first capacitor Cd1 does not reach the voltage of the fuel cell 50, which is calculated by multiplying the first specified value Tc1 by the number of stacked cells, the control unit 19 sets the duty ratio to "0". That is, the control unit 19 always maintains the switching element Sw of the first DC/DC converter 13 in an open state. Thereby, the control unit 19 sets the voltage of the first capacitor Cd1 to the first specified value Tc1 by not charging the first power storage device 12 and storing the power generated by the fuel cell 50 in the first capacitor Cd1. The voltage of the fuel cell 50 is calculated by multiplying by the number of stacked cells. When the voltage V1 of the first capacitor Cd1 reaches the voltage of the fuel cell 50, which is calculated by multiplying the first specified value Tc1 by the number of stacked cells, the control unit 19 multiplies the first specified value Tc1 by the number of stacked cells. A duty ratio is calculated to convert the voltage of the fuel cell 50, which is calculated by multiplying The first power storage device 12 is charged by changing the open/close state of Sw.

In step S110, when the second command S2 is input to the control unit 19 of the first DC/DC converter 13, the control unit 19 of the first DC/DC converter 13 sets the voltage V1 of the first capacitor Cd1 and the second specified value. The voltage of the fuel cell 50 calculated by multiplying Tc2 by the number of stacked cells is compared. If the voltage V1 of the first capacitor Cd1 does not reach the voltage of the fuel cell 50 calculated by multiplying the second specified value Tc2 by the number of stacked cells, the control unit 19 sets the duty ratio to "0". That is, the control unit 19 always maintains the switching element Sw of the first DC/DC converter 13 in an open state. Thereby, the control unit 19 sets the voltage of the first capacitor Cd1 to the second specified value Tc2 by not charging the first power storage device 12 and storing the power generated by the fuel cell 50 in the first capacitor Cd1. The voltage of the fuel cell 50 is calculated by multiplying by the number of stacked cells. When the voltage V1 of the first capacitor Cd1 reaches the voltage of the fuel cell 50, which is calculated by multiplying the second specified value Tc2 by the number of stacked cells, the control unit 19 multiplies the second specified value Tc2 by the number of stacked cells. A duty ratio is calculated to convert the voltage of the fuel cell 50, which is calculated by multiplying The first power storage device 12 is charged by changing the open/close state of Sw.

In step S110, when the third command S3 is input to the control unit 19 of the first DC/DC converter 13, the control unit 19 of the first DC/DC converter 13 sets the voltage V1 of the first capacitor Cd1 and the third specified value. The voltage of the fuel cell 50 calculated by multiplying Tc3 by the number of stacked cells is compared. When the voltage V1 of the first capacitor Cd1 does not reach the voltage of the fuel cell 50 calculated by multiplying the third specified value Tc3 by the number of stacked cells, the control unit 19 sets the duty ratio to "0". That is, the control unit 19 always maintains the switching element Sw of the first DC/DC converter 13 in an open state. Thereby, the control unit 19 sets the voltage of the first capacitor Cd1 to the third specified value Tc3 by not charging the first power storage device 12 and storing the power generated by the fuel cell 50 in the first capacitor Cd1. The voltage of the fuel cell 50 is calculated by multiplying by the number of stacked cells. When the voltage V1 of the first capacitor Cd1 reaches the voltage of the fuel cell 50, which is calculated by multiplying the third specified value Tc3 by the number of stacked cells, the control unit 19 multiplies the third specified value Tc3 by the number of stacked cells. A duty ratio is calculated to convert the voltage of the fuel cell 50, which is calculated by multiplying The first power storage device 12 is charged by changing the open/close state of Sw.

In the first charging control, after step S110 is completed, the above control is repeated from step S101 unless the towing tractor is turned off.
As shown in FIG. 4, in the second charging control, when the first command S1, the second command S2, or the third command S3 is output to the control unit 19 of the second DC/DC converter 23, the second DC/DC converter 23 The control unit 19 calculates a duty ratio for controlling the switching element Sw of the second DC/DC converter 23 (step S116).

As shown in FIGS. 2 and 4, in step S116, when the first command S1 is input to the control unit 19 of the second DC/DC converter 23, the control unit 19 of the second DC/DC converter 23 The voltage V2 of Cd2 is compared with the voltage of the fuel cell 50 calculated by multiplying the first specified value Tc1 by the number of stacked cells. If the voltage V2 of the second capacitor Cd2 does not reach the voltage of the fuel cell 50, which is calculated by multiplying the first specified value Tc1 by the number of stacked cells, the control unit 19 sets the duty ratio to "0". That is, the control unit 19 always maintains the switching element Sw of the second DC/DC converter 23 in an open state. Thereby, the control unit 19 sets the voltage of the second capacitor Cd2 to the first specified value Tc1 by not charging the second power storage device 22 and storing the power generated by the fuel cell 50 in the second capacitor Cd2. The voltage of the fuel cell 50 is calculated by multiplying by the number of stacked cells. When the voltage V2 of the second capacitor Cd2 reaches the voltage of the fuel cell 50, which is calculated by multiplying the first specified value Tc1 by the number of stacked cells, the control unit 19 multiplies the first specified value Tc1 by the number of stacked cells. calculates a duty ratio for converting the voltage of the fuel cell 50 calculated by multiplying by That is, the second power storage device 22 is charged by changing the open/close state of the switching element Sw.

In step S116, when the second command S2 is input to the control unit 19 of the second DC/DC converter 23, the control unit 19 of the second DC/DC converter 23 controls the voltage V2 of the second capacitor Cd2 and the second specified value. The voltage of the fuel cell 50 calculated by multiplying Tc2 by the number of stacked cells is compared. When the voltage V2 of the second capacitor Cd2 does not reach the voltage of the fuel cell 50 calculated by multiplying the second specified value Tc2 by the number of stacked cells, the control unit 19 sets the duty ratio to "0". That is, the control unit 19 always maintains the switching element Sw of the second DC/DC converter 23 in an open state. Thereby, the control unit 19 sets the voltage of the second capacitor Cd2 to the second specified value Tc2 by not charging the second power storage device 22 and storing the power generated by the fuel cell 50 in the second capacitor Cd2. The voltage of the fuel cell 50 is calculated by multiplying by the number of stacked cells. When the voltage V2 of the second capacitor Cd2 reaches the voltage of the fuel cell 50, which is calculated by multiplying the second specified value Tc2 by the number of stacked cells, the control unit 19 multiplies the second specified value Tc2 by the number of stacked cells. calculates a duty ratio for converting the voltage of the fuel cell 50 calculated by multiplying by That is, the second power storage device 22 is charged by changing the open/close state of the switching element Sw.

In step S116, when the third command S3 is input to the control unit 19 of the second DC/DC converter 23, the control unit 19 of the second DC/DC converter 23 controls the voltage V2 of the second capacitor Cd2 and the third specified value. The voltage of the fuel cell 50 calculated by multiplying Tc3 by the number of stacked cells is compared. If the voltage V2 of the second capacitor Cd2 does not reach the voltage of the fuel cell 50 calculated by multiplying the third specified value Tc3 by the number of stacked cells, the control unit 19 sets the duty ratio to "0". That is, the control unit 19 always maintains the switching element Sw of the second DC/DC converter 23 in an open state. Thereby, the control unit 19 sets the voltage of the second capacitor Cd2 to the third specified value Tc3 by not charging the second power storage device 22 and storing the power generated by the fuel cell 50 in the second capacitor Cd2. The voltage of the fuel cell 50 is calculated by multiplying by the number of stacked cells. When the voltage V2 of the second capacitor Cd2 reaches the voltage of the fuel cell 50, which is calculated by multiplying the third specified value Tc3 by the number of stacked cells, the control unit 19 multiplies the third specified value Tc3 by the number of stacked cells. calculates a duty ratio for converting the voltage of the fuel cell 50 calculated by multiplying by That is, the second power storage device 22 is charged by changing the open/close state of the switching element Sw.

In the second charging control, after step S116 is completed, the above control is repeated from step S101 unless the towing tractor is turned off.
In the first charge control and the second charge control, considering the relationship between the power generation amount of the fuel cell 50 and the voltage applied to the cells forming the fuel cell 50, the The first command S1, the second command S2, and the third command S3 are such that the larger the charging rate SOC1 of the first power storage device 12 and the charging rate SOC2 of the second power storage device 22, the less the amount of power generated by the fuel cell 50 is. It is set so that the first power storage device 12 and the second power storage device 22 are not charged. Although not shown in FIGS. 3 and 4, if the first power storage device 12 and the second power storage device 22 are fully charged with no output request from the fuel cell 50, and the towing tractor is not turned off, the temporary The drive of the fuel cell 50 is stopped immediately.

The operation of this embodiment will be explained.
Electric power generated by the fuel cell 50 is supplied to the first system 10 and the second system 20. The voltage of the power supplied to the first system 10 is stepped down to 80V by the first DC/DC converter 13 and is supplied to the load 11 and charged to the first power storage device 12 . The voltage of the electric power supplied to the second system 20 is stepped down to 48V by the second DC/DC converter 23, and is supplied to the first auxiliary machine 21 and charged to the second power storage device 22. The power supplied to the second system 20 is also supplied to the third system 30. The electric power supplied to the third system 30 is stepped down to 12V by the third DC/DC converter 33 and is supplied to the second auxiliary machine 31 and charged to the third power storage device 32.

The power generated by the fuel cell 50 is stored in the first capacitor Cd1 of the first DC/DC converter 13, and the voltage of the power stored in the first capacitor Cd1 is converted to 80V, which is the voltage required by the load 11. The power generated by the fuel cell 50 is stored in the second capacitor Cd2 of the second DC/DC converter 23, and the voltage of the power stored in the second capacitor Cd2 is converted to 48V, which is the required voltage of the first auxiliary device 21. be done. The charge on the first capacitor Cd1 is prevented from being drawn to the second capacitor Cd2 by the first diode 41, and the charge on the second capacitor Cd2 is prevented from being drawn to the first capacitor Cd1 by the second diode 42. There is.

Further, in the first charging control, the FCECU 34 changes commands S1, S2, and S3 output to the control unit 19 of the first DC/DC converter 13 according to the charging rate SOC1 of the first power storage device 12. The control unit 19 changes the duty ratio for controlling the switching element Sw of the first DC/DC converter 13 according to input commands S1, S2, and S3. Therefore, the method of charging the first power storage device 12 is changed by commands S1, S2, and S3 output from the FCECU 34 to the control unit 19. Therefore, in the first charging control, the FCECU 34 changes the commands S1, S2, and S3 output to the control unit 19 of the first DC/DC converter 13 according to the charging rate SOC1 of the first power storage device 12 during the high potential avoidance control. As a result, the method of charging the first power storage device 12 is changed.

Furthermore, in the second charging control, the FCECU 34 changes commands S1, S2, and S3 output to the control unit 19 of the second DC/DC converter 23 according to the charging rate SOC2 of the second power storage device 22. The control unit 19 changes the duty ratio for controlling the switching element Sw of the second DC/DC converter 23 in accordance with input commands S1, S2, and S3. Therefore, the method of charging the second power storage device 22 is changed by commands S1, S2, and S3 output from the FCECU 34 to the control unit 19. Therefore, in the second charging control, the FCECU 34 changes the commands S1, S2, and S3 output to the control unit 19 of the second DC/DC converter 23 according to the charging rate SOC2 of the second power storage device 22 during the high voltage avoidance control. As a result, the method of charging the second power storage device 22 is changed.

The effects of this embodiment will be explained.
(1) The movement of charges between the first capacitor Cd1 provided on the input side inside the first DC/DC converter 13 and the second capacitor Cd2 provided on the input side inside the second DC/DC converter 23 is This is suppressed by the first diode 41 and the second diode 42. Therefore, the power stored in the first capacitor Cd1 and the second capacitor Cd2 is prevented from running out, and the voltage of the power generated by the fuel cell 50 cannot be converted. Therefore, the driving state of the fuel cell system 1 can be stabilized.

(2) The first diode 41 allows the current to flow from the first positive wiring Lp11 for the first system to the second positive wiring Lp12 for the first system, while allowing the current to flow from the first capacitor Cd1 to the first positive wiring Lp11 for the first system. Current can be suppressed. The second diode 42 allows current to flow from the first positive wiring Lp21 for the second system to the second positive wiring Lp22 for the second system, while allowing current to flow from the second capacitor Cd2 to the first positive wiring Lp21 for the second system. can be suppressed. Therefore, the driving state of the fuel cell system 1 can be suitably stabilized using a single diode.

(3) The FCECU 34 implements high potential avoidance control. The high potential avoidance control includes first charging control in which a command output by FCECU 34 to control unit 19 of first DC/DC converter 13 is changed according to charging rate SOC1 of first power storage device 12, and charging of second power storage device 22. A second charging control is performed in which a command output from the FCECU 34 to the control unit 19 of the second DC/DC converter 23 is changed according to the rate SOC2. That is, even if the driving of the fuel cell 50 is stopped, the FCECU 34 controls the driving of the first DC/DC converter 13 and the second DC/DC converter 23 at the charging rates SOC1 and SOC2 of the first power storage device 12 and the second power storage device 22, respectively. By charging the first power storage device 12 and the second power storage device 22 with the electric power generated by the fuel cell 50, the voltage of the fuel cell 50 is prevented from exceeding the high potential avoidance reference voltage. . Therefore, deterioration of the fuel cell 50 can be suppressed.

(4) In the first charging control, the first DC/DC converter 13 is controlled according to the charging rate SOC1 of the first power storage device 12, and in the second charging control, the first DC/DC converter 13 is controlled according to the charging rate SOC2 of the second power storage device 22. 2DC/DC converter 23 is controlled. That is, the first charge control and the second charge control are performed in parallel with each other, and the charge control command of one power supply system does not affect the command of the other power supply system, so that the charge control of the fuel cell system 1 is performed. It can be made simple.

(5) By connecting the first positive wiring Lp31 for the third system to the first positive wiring Lp11 for the first system, and connecting the first negative wiring Ln31 for the third system to the first negative wiring Ln11 for the first system. Although the third DC/DC converter 33 can step down the voltage of 140V, which is the voltage of the electric power generated by the fuel cell 50, to 12V, the voltage of 140V, which is the voltage of the electric power generated by the fuel cell 50, and the second auxiliary machine There is a large difference between 12V, which is the voltage at which 31 is driven. Therefore, the third DC/DC converter 33 is required to have high withstand voltage performance. Generally, a converter with high withstand voltage performance is expensive, so the manufacturing cost of the fuel cell system 1 becomes high.

In this respect, the third system 30 is electrically connected to the output side of the second DC/DC converter 23. The third DC/DC converter 33 only needs to convert 48V, which is the voltage that drives the first auxiliary machine 21 of the second system 20, to 12V, which is the voltage that the second auxiliary machine 31 drives. There is no need to make the withstand voltage performance of the converter 33 higher than necessary. Therefore, the manufacturing cost of the fuel cell system 1 can be suppressed.

Note that this embodiment can be implemented with the following modifications. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
○ Each of the first DC/DC converter 13 and the second DC/DC converter 23 was equipped with a control section 19, but for example, it is possible to install these control sections 19 outside the first DC/DC converter 13 and the second DC/DC converter 23. You may change it so that it is provided. Further, these control sections 19 may be integrated to form one new control section.

○ Each of the first DC/DC converter 13 and the second DC/DC converter 23 has a control section 19, and the control section 19 controls the switching element Sw by calculating the duty ratio. Not exclusively. For example, the control unit 19 may be omitted from each of the first DC/DC converter 13 and the second DC/DC converter 23, and the FCECU 34 may have the function of calculating the duty ratio. In this case, the voltage V1 of the first capacitor Cd1 and the voltage V2 of the second capacitor Cd2 are input to the FCECU 34. Moreover, it is not necessary to output the first command S1, the second command S2, or the third command S3 from the FCECU 34. That is, the first charging control and the second charging control may be changed so that they can be performed only by the FCECU 34.

○ In high potential avoidance control, it is not necessary to perform the first charging control and the second charging control. For example, if a discharging resistor is newly installed in the fuel cell system 1 and there is no output request from the fuel cell 50, the power generated by the fuel cell 50 is released to the discharging resistor, and the discharging resistor converts the electric power into heat and dissipates the heat. You may let them. In this case, it is preferable that the heat radiated by the discharge resistor be used, for example, for air conditioning of a towing tractor. In addition, in this example of a change, the 1st charging rate detection part 61 and the 2nd charging rate detection part 62 may be omitted.

○ By connecting the first positive wiring Lp31 for the third system to the first positive wiring Lp11 for the first system and connecting the first negative wiring Ln31 for the third system to the first negative wiring Ln11 for the first system, The 3DC/DC converter 33 may be connected to the fuel cell 50 in parallel with the first DC/DC converter 13. In this case, the first positive electrode wiring Lp31 for the third system is connected to the first branch wiring connected to the first positive electrode wiring Lp11 for the first system, and the second branch wiring connected to the positive electrode on the input side of the third DC/DC converter 33. It is preferable that the third diode is formed between the first branch wiring and the second branch wiring. It is preferable that the third diode is arranged so as to allow only conduction of current from the first branch wiring to the second branch wiring. Here, the third DC/DC converter 33 is an example of a second DC/DC converter. The first branch wiring is an example of the third wiring, and the second branch wiring is an example of the fourth wiring. The third diode is an example of a second backflow prevention unit that prevents the charge of the capacitor Cd, which is the second capacitor on the input side inside the third DC/DC converter 33, from flowing back toward the first branch wiring.

The first DC/DC converter 13 and the second DC/DC converter 23 may be switching regulators that boost the voltage of the electric power generated by the fuel cell 50. Note that when changing in this way, the voltage at which the load 11 is driven is higher than the voltage generated by the fuel cell 50, and the voltage at which the first auxiliary device 21 is driven is higher than the voltage generated by the fuel cell 50. is the premise. For example, the first DC/DC converter 13 and the second DC/DC converter 23 may be changed as follows. Note that since the first DC/DC converter 13 and the second DC/DC converter 23 have the same configuration, only the changes in the configuration of the first DC/DC converter 13 will be explained, and the details of the second DC/DC converter 23 will be explained. I will omit the explanation of the configuration.

As shown in FIG. 5, the coil Co of the first DC/DC converter 13 is arranged at a portion of the positive electrode bus 14 sandwiched between the first relay wiring 16 and the second relay wiring 17. The switching element Sw is arranged on the second relay wiring 17. The diode Di is arranged at a portion of the positive bus bar 14 sandwiched between the second relay wiring 17 and the third relay wiring 18. The diode Di is arranged so that the portion of the positive electrode bus 14 sandwiched between the second relay wiring 17 and the third relay wiring 18 is allowed to be energized only from the second relay wiring 17 side to the third relay wiring 18 side. Ru.

When the first DC/DC converter 13 and the second DC/DC converter 23 are used as boost converters, they are not limited to switching regulators, and may be linear regulators. However, the first capacitor Cd1 is provided on the input side inside the first DC/DC converter 13, and the second capacitor Cd2 is provided on the input side inside the second DC/DC converter 23.

○ The first backflow prevention section and the second backflow prevention section may be changed as follows.
As shown in FIG. 6, between the first positive wiring Lp11 for the first system and the second positive wiring Lp12 for the first system, the first positive wiring Lp11 for the first system and the second positive wiring Lp12 for the first system are connected. A first switch member 81 is provided to switch between a coupled state in which the Lp 12 is electrically connected and a cutoff state in which the Lp 12 is electrically interrupted. A current sensor 70 is provided on the second positive electrode wiring Lp12 for the first system.

The first positive wiring Lp21 for the second system and the second positive wiring Lp22 for the second system are electrically connected between the first positive wiring Lp21 for the second system and the second positive wiring Lp22 for the second system. A second switch member 82 is provided to switch between a coupled state in which the first positive electrode wiring Lp21 for the second system and a cutoff state electrically disconnect the second positive electrode wiring Lp22 for the second system. A current sensor 70 is provided on the second positive electrode wiring Lp22 for the second system.

Signals detected by each current sensor 70 are input to the FCECU 34. The FCECU 34 determines whether the electric charge of the first capacitor Cd1 is flowing backward to the second positive electrode wiring Lp12 for the first system based on the input signals detected by each current sensor 70, and It is determined whether the charge of the second capacitor Cd2 is flowing backward into the second positive electrode wiring Lp22.

When the FCECU 34 determines that the charge of the first capacitor Cd1 is flowing backward into the second positive wiring Lp12 for the first system, the FCECU 34 opens the first switch member 81 to bring it into the cutoff state. The first switch member 81 functions as a first backflow prevention section that prevents the charge of the first capacitor Cd1 from flowing back toward the first positive wiring Lp11 for the first system.

When the FCECU 34 determines that the charge of the second capacitor Cd2 is flowing backward into the second positive wiring Lp22 for the second system, the FCECU 34 opens the second switch member 82 to bring it into the cutoff state. The second switch member 82 functions as a second backflow prevention section that prevents the charge of the second capacitor Cd2 from flowing back toward the first positive wiring Lp21 for the second system.

The first system 10 is a system that supplies power to the load 11, and the second system 20 is a system that supplies power to the first auxiliary machine 21, but the present invention is not limited to this. The first system 10 and the second system 20 have different required voltages and may be changed in any way as long as they are driven by the electric power generated by the fuel cell 50. Note that the third system 30 may also be changed in the same manner.

○ The voltage of the electric power generated by the fuel cell 50 was 140V, the voltage at which the load 11 was driven was 80V, the voltage at which the first auxiliary machine 21 was driven was 48V, and the voltage at which the second auxiliary machine 31 was driven was 12V. , the required voltage may be changed as appropriate. Accordingly, whether the first DC/DC converter 13, the second DC/DC converter 23, and the third DC/DC converter 33 are used as a step-down converter or a step-up converter may be changed as appropriate.

Inside the first DC/DC converter 13, the positive electrode bus 14 may be a wiring provided between a connection point with the first relay wiring 16 and a connection point with the third relay wiring 18. Similarly, the negative electrode bus 15 may be a wiring provided between a connection point with the first relay wiring 16 and a connection point with the third relay wiring 18. In this case, the second positive electrode wiring Lp12 for the first system may be extended to the connection point between the positive electrode bus 14 and the first relay wiring 16 inside the first DC/DC converter 13. The first negative wiring Ln11 for the first system may be extended to the connection point between the negative bus 15 and the first relay wiring 16 inside the first DC/DC converter 13. The third positive electrode wiring Lp13 for the first system may be extended to the connection point between the positive electrode bus 14 and the third relay wiring 18 inside the first DC/DC converter 13. The second negative wiring Ln12 for the first system may be extended to the connection point between the negative bus 15 and the third relay wiring 18 inside the first DC/DC converter 13. When changing in this way, the input terminals 13a, 13b and the output terminals 13c, 13d of the first DC/DC converter 13 are not provided, and each wiring Lp12, Ln11, Lp13, Ln12 is directly connected to the inside of the first DC/DC converter 13. may be extended.

Similarly, inside the second DC/DC converter 23 , the positive electrode bus 14 may be a wiring provided between a connection point with the first relay wiring 16 and a connection point with the third relay wiring 18 . Similarly, the negative electrode bus 15 may be a wiring provided between a connection point with the first relay wiring 16 and a connection point with the third relay wiring 18. In this case, the second positive electrode wiring Lp22 for the second system may be extended to the connection point between the positive electrode bus 14 and the first relay wiring 16 inside the second DC/DC converter 13. The first negative wiring Ln21 for the second system may be extended to the connection point between the negative bus 15 and the first relay wiring 16 inside the second DC/DC converter 23. The third positive electrode wiring Lp23 for the second system may be extended to the connection point between the positive electrode bus 14 and the third relay wiring 18 inside the second DC/DC converter 23. The second negative wiring Ln22 for the second system may be extended to the connection point between the negative bus 15 and the third relay wiring 18 inside the second DC/DC converter 23. When changing in this way, the input ends 23a, 23b and the output ends 23c, 23d of the second DC/DC converter 23 are not provided, and each wiring Lp22, Ln21, Lp23, Ln22 is directly connected to the inside of the second DC/DC converter 23. may be extended.

○ The fuel cell system 1 has been applied to industrial vehicles such as forklifts and towing tractors, but is not limited to this. For example, the fuel cell system 1 may be applied to a fuel cell vehicle.

DESCRIPTION OF SYMBOLS 1... Fuel cell system, 10... First system, 11... Load, 12... First power storage device, 13... First DC/DC converter, 19... Control unit, 20... Second system, 21... First auxiliary machine, 22 ...Second power storage device, 23...Second DC/DC converter, 30...Third system, 31...Second auxiliary equipment, 32...Third power storage device, 33...Third DC/DC converter, 41...First diode, 42... Second diode, 50... Fuel cell, 61... First charge rate detection section, 62... Second charge rate detection section, 81... First switch member, 82... Second switch member, Lp11... First positive electrode for first system Wiring, Lp12...second positive electrode wiring for the first system, Lp21...first positive electrode wiring for the second system, Lp22...second positive electrode wiring for the second system, Cd1...first capacitor, Cd2...second capacitor, Sw...switching Element, S1...first command, S2...second command, S3...third command, SOC1, SOC2...charging rate.

Claims (3)

fuel cell and
a first DC/DC converter that converts the voltage of the power generated by the fuel cell into a first voltage and has a first capacitor on an internal input side;
a second DC/DC converter that is connected in parallel with the first DC/DC converter to the fuel cell, converts the voltage of the power generated by the fuel cell into a second voltage, and has a second capacitor on an internal input side; A fuel cell system comprising a converter,
a first wiring connected to the fuel cell;
a second wiring electrically connected to the first capacitor while being connected to the input side of the first DC/DC converter;
a first backflow prevention part that is electrically connected to the first wiring and the second wiring and prevents the electric charge of the first capacitor from flowing back toward the first wiring;
a third wiring connected to the first wiring;
a fourth wiring electrically connected to the second capacitor while being connected to the input side of the second DC/DC converter;
A fuel cell system comprising: a second backflow prevention section that is electrically connected to the third wiring and the fourth wiring and prevents the electric charge of the second capacitor from flowing back toward the third wiring. The first backflow prevention section is a diode that only allows current to flow from the first wiring to the second wiring,
2. The fuel cell system according to claim 1, wherein the second backflow prevention section is a diode that only allows current to flow from the third wiring to the fourth wiring. The first DC/DC converter and the second DC/DC converter are switching regulators,
a first power storage device connected to the output side of the first DC/DC converter;
a second power storage device connected to the output side of the second DC/DC converter;
a charging rate detection unit that detects charging rates of each of the first power storage device and the second power storage device;
a control device that controls the first DC/DC converter and the second DC/DC converter based on the charging rate;
a control unit that controls conduction states of switching elements included in each of the first DC/DC converter and the second DC/DC converter based on a command output from the control device,
The control device includes:
Executing high potential avoidance control to prevent the voltage of the fuel cell from exceeding a predetermined voltage;
In the high potential avoidance control,
a first charging control that changes the command output to the control unit of the first DC/DC converter according to the charging rate of the first power storage device;
2. A second charging control that changes the command output to the control unit of the second DC/DC converter according to the charging rate of the second power storage device. 2. The fuel cell system according to 2.