Supply system

Abstract

To reduce power consumption when converting a voltage of output current.SOLUTION: A supply system S includes: a first converter 31 which supplies a first conversion current obtained by converting a voltage of output current of a fuel battery 21, to a motor 11 and an electrical apparatus 5 other than the motor 11, and in which second conversion efficiency in the case of a current value being equal to or higher than a prescribed value, is higher than first conversion efficiency in the case of a current value of output current being lower than a prescribed value; a second converter 32 which is provided in parallel to the first converter 31, and supplies a second conversion current obtained by converting a voltage of output current, to the electrical apparatus 5, and in which third conversion efficiency in the case of a current value being lower than a prescribed value, is higher than the first conversion efficiency; and a supply controller which causes the first conversion current to be supplied from the first converter 31 to the motor 11 and the electrical apparatus 5, and if a current value is lower than a prescribed value, the supply controller causes the second conversion current to be supplied from the second converter 32 to the electrical apparatus 5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a supply system for supplying an output current of a fuel cell to an electrically operated device. [Background technology]

[0002] Converters that convert the voltage of a fuel cell's output current are known. Patent Document 1 discloses a converter that is provided between a fuel cell and a motor and converts the voltage of the fuel cell's output current into a voltage suitable for the motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-165149 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the conversion efficiency of a converter when converting an output current into a voltage varies depending on the current value. Therefore, if the output current value is within a range where the converter's conversion efficiency is low, excess power is consumed during voltage conversion.

[0005] The present invention has been made in view of these points, and has as its object to reduce power consumption when converting the voltage of an output current. [Means for solving the problem]

[0006] In one aspect of the present invention, there is provided a supply system comprising: a first converter that supplies a first converted current, obtained by converting the voltage of an output current of a fuel cell, to a motor and an electrical device other than the motor, the first converter having a second conversion efficiency when the current value is equal to or greater than a predetermined value that is higher than a first conversion efficiency when the current value is less than a predetermined value; a second converter that is arranged in parallel with the first converter and supplies a second converted current, obtained by converting the voltage of the output current, to the electrical device, the second converter having a third conversion efficiency when the current value is less than the predetermined value that is higher than the first conversion efficiency; and a supply control unit that causes the first converter to supply the first converted current to the motor and the electrical device when the current value is equal to or greater than the predetermined value, and causes the second converter to supply the second converted current to the electrical device when the current value is less than the predetermined value.

[0007] The supply control unit may have one or more switches that switch whether or not to supply the output current to the first converter and whether or not to supply the output current to the second converter, and the supply control unit may switch the one or more switches to supply the output current to the first converter when the current value is greater than or equal to the predetermined value, and to supply the output current to the second converter when the current value is less than the predetermined value.

[0008] The first converter may be a converter that boosts the voltage of the output current to a voltage that can drive the motor, and the second converter may be a converter that lowers the voltage of the output current to a voltage that can drive the electrical device.

[0009] The output current of the fuel cell is a direct current, and the system may further include an inverter provided between the first converter and the motor and capable of converting the direct current into an alternating current, and a third converter provided between the inverter and the electrical equipment and converting the alternating current output by the inverter into a direct current capable of driving the electrical equipment and supplying the direct current to the electrical equipment.

[0010] The supply control unit may supply current to the electrical device from the third converter via the first converter even if the current value is less than the predetermined value, if the product of the conversion efficiency of the first converter corresponding to the current value and the conversion efficiency of the third converter is higher than the efficiency of the second converter corresponding to the current value.

[0011] The predetermined value may be set within a predetermined range including a current value at which the conversion efficiency of the first converter, which changes depending on the current value, and the conversion efficiency of the second converter, which changes depending on the current value, match.

[0012] The power supply control unit may have an acquisition unit that acquires a motor current value for driving the motor and an equipment current value for driving the electrical equipment, and the supply control unit may cause the first converter to supply the first converted current to the motor and the electrical equipment when the sum of the motor current value and the equipment current value is equal to or greater than the predetermined value, and cause the second converter to supply the second converted current to the electrical equipment when the current value is less than the predetermined value.

[0013] The power supply may include a battery that supplies power to at least one of the motor and the electrical device, the acquisition unit acquires a charging current value required to charge the battery, and the supply control unit may cause the first converter to supply the first converted current to the battery and the electrical device if the sum of the motor current value and the device current value is less than the predetermined value, but the sum of the motor current value and the device current value plus the charging current value is equal to or greater than the predetermined value. [Effects of the Invention]

[0014] The present invention provides an advantage in that it is possible to reduce power consumption when converting the voltage of an output current. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is a diagram illustrating a configuration of a supply system. [Figure 2]10 is a diagram for explaining conversion efficiency according to the current value of the output current. FIG. [Figure 3] FIG. 2 is a diagram illustrating the configuration of a supply control device. [Figure 4] 10 is a flowchart illustrating an example of a process for switching converters. [Figure 5] FIG. 10 is a diagram for explaining a supply system according to a first modified example. [Figure 6] FIG. 10 is a diagram illustrating a supply system according to a second modification. [Figure 7] FIG. 10 is a diagram for explaining a supply system according to a third modification. DETAILED DESCRIPTION OF THE INVENTION

[0016] [Configuration of supply system S] 1 is a diagram illustrating the configuration of a supply system S. The supply system S is a system that supplies electric power generated by a fuel cell 21 to a motor 11 and an electric device 5. The supply system S is installed in, for example, a vehicle. The supply system S includes an electric device 5, a supply control device 6, the motor 11, the fuel cell 21, a first converter 31, and a second converter 32.

[0017] The fuel cell 21 is an electrochemical cell that generates electricity when supplied with hydrogen and oxygen. Specifically, the fuel cell 21 generates electricity by converting the energy of an oxidation-reduction reaction between hydrogen and oxygen into electricity. The fuel cell 21 generates electricity using hydrogen and oxygen and outputs direct current. The fuel cell 21 supplies the output current to the motor 11 and the electrical device 5. Hydrogen is supplied to the fuel cell 21 from a hydrogen tank 22 that stores hydrogen. The hydrogen tank 22 is, for example, a pressure-resistant container that stores compressed hydrogen obtained by compressing gaseous hydrogen, but liquid hydrogen may also be stored therein.

[0018] The motor 11 operates when power is supplied from the fuel cell 21. The motor 11 receives power via a converter that converts the voltage of the output current of the fuel cell 21 into a voltage that can drive the motor 11. The motor 11 receives power from the fuel cell 21 and drives a driven device 12 that is connected to the output shaft of the motor 11. The driven device 12 is, for example, a transmission, but is not limited to this.

[0019] The electric device 5 is an electric device that is driven by electricity. Examples of the electric device 5 include, but are not limited to, an air conditioner, a sensor that detects the vehicle state and the surrounding environment, a display unit that displays information detected by the sensor, and a device that controls the vehicle based on the information detected by the sensor. The electric device 5 is powered by a supply of electric power from the fuel cell 21. The electric device 5 receives electric power via a converter that converts the voltage of the output current of the fuel cell 21 into a voltage that can drive the electric device 5.

[0020] When the fuel cell 21 is started, an imbalance occurs in the amounts of oxygen and hydrogen supplied, generating a reverse current that corrodes the carbon in the catalyst layer of the fuel cell 21. The carbon corrosion causes the platinum catalyst supported on the catalyst layer to aggregate. This reduces the area of ​​the platinum catalyst that can promote the reaction between hydrogen and oxygen, thereby reducing the performance of the fuel cell 21. When the performance of the fuel cell 21 decreases, the power generation efficiency of the fuel cell 21 decreases, and the amount of hydrogen consumed by the fuel cell 21 increases. In this way, the amount of hydrogen consumed increases as the number of times the fuel cell 21 is stopped and started increases. Therefore, the amount of hydrogen consumed when the fuel cell 21 continues to generate power, even at a low current, is less than the amount of hydrogen consumed when the fuel cell 21 is stopped and started.

[0021] However, the conversion efficiency of a converter varies depending on the current value. For example, a converter with high conversion efficiency at high current has a lower conversion efficiency at low current than at high current. In conventional technology, a converter with high conversion efficiency at high current converts the voltage of the output current of the fuel cell 21 and supplies it to the motor 11 and the electrical device 5. Therefore, when the fuel cell 21 generates power at low current, the voltage conversion efficiency of the converter with high conversion efficiency at high current is low. This requires extra power to supply the power required by the motor 11 and the electrical device 5, resulting in increased power consumption.

[0022] The supply system S according to this embodiment includes a first converter 31 with high conversion efficiency at high currents and a second converter 32 with high conversion efficiency at low currents. The supply system S switches between converters depending on the current value of the output current of the fuel cell 21. When the motor 11 is operating and the output current value is high, the supply system S supplies power to the motor 11 and the electrical device 5 using the first converter 31 with high conversion efficiency at high currents. When the motor 11 is stopped and the output current value is low, the supply system S supplies power to the electrical device 5 using the second converter 32 with high conversion efficiency at low currents. This allows the supply system S to supply power using an appropriate converter depending on the output current value, thereby suppressing excess power consumption and reducing power consumption when converting the voltage of the output current. Other configurations of the supply system S are described below.

[0023] The first converter 31 is a voltage conversion circuit that converts the voltage of a direct current into a voltage different from the direct current voltage, and is a so-called DC / DC converter. The first converter 31 converts the voltage value of the input direct current into a voltage value different from the direct current voltage. The first converter 31 is provided between the fuel cell 21 and the motor 11. The first converter 31 boosts the voltage of the output current of the fuel cell 21 to a voltage that can drive the motor 11. For example, the first converter 31 boosts the voltage of the output current of the fuel cell 21 to a rated voltage of the motor 11. The first converter 31 supplies a first converted current, which is the voltage of the output current boosted to the rated voltage of the motor 11, to the motor 11 and the electrical device 5. Specifically, the first converter 31 supplies the first converted current to the inverter 34, thereby supplying the first converted current to the motor 11 and the electrical device 5. The inverter 34 will be described in detail later.

[0024] The conversion efficiency of the first converter 31 at high currents is higher than the conversion efficiency of the first converter 31 at low currents. FIG. 2 is a diagram for explaining the conversion efficiency according to the current value of the output current. The horizontal axis of FIG. 2 represents the current value, and the vertical axis represents the conversion efficiency. Graph A is a graph showing the conversion efficiency of the first converter 31. Graph A of FIG. 2 is an upwardly convex graph. As shown in graph A, the conversion efficiency of the first converter 31 is higher when the current value is equal to or greater than a predetermined value D than when it is less than the predetermined value D. To give a specific example, the second conversion efficiency A2 when the current value is equal to or greater than the predetermined value D is higher than the first conversion efficiency A1 when the current value of the output current is less than the predetermined value D.

[0025] The second converter 32 is a DC / DC converter like the first converter 31. The second converter 32 converts the voltage value of the input direct current into a voltage value different from the voltage. The second converter 32 is provided in parallel with the first converter 31 between the fuel cell 21 and the electric device 5. The second converter 32 is provided, for example, on an electric wire that branches at a branch point 43 between the fuel cell 21 and the first converter 31 and connects the fuel cell 21 to the electric device 5. The second converter 32 steps down the voltage of the output current to a rated voltage of the electric device 5 that can drive the electric device 5. The second converter 32 supplies the electric device 5 with a second converted current obtained by stepping down the voltage of the output current to the rated voltage of the electric device 5.

[0026] The conversion efficiency of the second converter 32 at low currents is higher than the conversion efficiency of the second converter 32 at high currents. Graph B in FIG. 2 is a graph showing the conversion efficiency of the second converter 32. Like the first converter 31, the conversion efficiency of the second converter 32 is an upwardly convex graph. Unlike the first converter 31, the conversion efficiency of the second converter 32 is higher when the current value is less than a predetermined value D than when it is equal to or greater than the predetermined value D. To give a specific example, the fourth conversion efficiency B2 of the second converter 32 when the current value is equal to or greater than the predetermined value D is lower than the second conversion efficiency A2 of the first converter 31.

[0027] 2 intersect at an intersection C. In other words, the conversion efficiency of the first converter 31 and the conversion efficiency of the second converter 32 match when the current value is a predetermined value D, and the magnitude relationship is reversed across the predetermined value D. To give a specific example, when the current value is less than the predetermined value D, a third conversion efficiency B1 of the second converter 32 is higher than the first conversion efficiency A1 of the first converter 31. Furthermore, when the current value is equal to or greater than the predetermined value D, a fourth conversion efficiency B2 of the second converter 32 is lower than the second conversion efficiency A2 of the first converter 31.

[0028] The inverter 34 is provided between the first converter 31 and the motor 11. The inverter 34 is an inverse conversion circuit capable of converting DC current into AC current. The inverter 34 converts the first converted current, which is the DC current boosted by the first converter 31, into AC current capable of driving the motor 11 and supplies the AC current to the motor 11.

[0029] The first switch 41 is an on / off switch that allows or stops the flow of current. When the first switch 41 is turned on, it allows current to flow, and when it is turned off, it stops the current. The first switch 41 is provided between the branch point 43 and the first converter 31. The first switch 41 can switch whether or not the output current of the fuel cell 21 is supplied to the first converter 31. When the first switch 41 is turned on, it allows the output current of the fuel cell 21 to flow to the first converter 31, thereby supplying the output current to the first converter 31. When the first switch 41 is turned off, it stops the output current of the fuel cell 21 and does not allow it to be supplied to the first converter 31.

[0030] The second switch 42, like the first switch 41, is an on / off switch that allows or stops the flow of current. The second switch 42 allows current to flow when turned on and stops the current when turned off. The second switch 42 is provided between the branch point 43 and the second converter 32. The second switch 42 can switch whether or not the second converted current is to be supplied from the second converter 32 to the electrical device 5. When turned on, the second switch 42 allows the output current of the fuel cell 21 to flow to the second converter 32, thereby supplying the output current to the second converter 32. When turned off, the second switch 42 stops the output current of the fuel cell 21 and prevents it from being supplied to the second converter 32.

[0031] The third converter 33 is a conversion circuit that converts AC current to DC current and converts the voltage of the current, and is a so-called AC / DC converter. The third converter 33 is provided between the inverter 34 and the electric device 5. The third converter 33 converts the AC current output by the inverter 34 into DC current that can drive the electric device 5, and converts the voltage of the converted DC current into a voltage that can drive the electric device 5 and supplies it to the electric device 5. The third converter 33 may convert the voltage of the AC current into a voltage that can drive the electric device 5, and then convert the AC current resulting from the converted voltage into DC current.

[0032] The battery 35 is a secondary battery that stores and supplies power. The battery 35 is connected to the inverter 34. The inverter 34 supplies power to at least one of the motor 11 and the electrical device 5. The battery 35 supplies power to at least one of the motor 11 and the electrical device 5 via the inverter 34.

[0033] [Configuration of supply control device 6] 3 is a diagram illustrating the configuration of the supply control device 6. The supply control device 6 switches the converter to be used depending on the current value. The supply control device 6 has a storage unit 61 and a control unit 62. The storage unit 61 is a storage medium including a ROM (Read Only Memory), a RAM (Random Access Memory), a hard disk, etc. The storage unit 61 stores a program executed by the control unit 62.

[0034] The control unit 62 is a computational resource including a processor such as a CPU (Central Processing Unit). The control unit 62 executes a program stored in the storage unit 61 to realize the functions of an acquisition unit 621 and a supply control unit 622.

[0035] The acquisition unit 621 acquires information related to the supply system S. The acquisition unit 621 acquires a motor current value for driving the motor 11. Specifically, the acquisition unit 621 acquires the motor current value from an ECU (Electronic Control Unit) that controls the motor 11. The acquisition unit 621 acquires an appliance current value for driving the electrical appliance 5 from the electrical appliance 5. The acquisition unit 621 acquires the motor current value and the sum of the appliance current values. The sum of the motor current value and the appliance current value corresponds to the current value of the output current of the fuel cell 21.

[0036] The supply control unit 622 adjusts the amount of hydrogen supplied from the hydrogen tank 22 to the fuel cell 21, thereby causing the fuel cell 21 to generate the desired amount of power. Specifically, the supply control unit 622 adjusts the amount of hydrogen supplied from the hydrogen tank 22 to the fuel cell 21 so that the fuel cell 21 can output an output current with a power value equal to the sum of the motor current value and the device current value.

[0037] The supply control unit 622 controls the supply destination of the output current of the fuel cell 21. The supply control unit 622 switches the first switch 41 and the second switch 42 depending on whether the current value of the output current is equal to or greater than a predetermined value D at which the magnitude relationship of the conversion efficiency is reversed, thereby switching the converter to which the output current is supplied to the fuel cell 21.

[0038] As shown in FIG. 2, the predetermined value D is a current value corresponding to the intersection C between the graphs A and B. However, the predetermined value D is not limited to this and may be set within a predetermined range including the predetermined value D. The predetermined range is a range in which a difference in conversion efficiency is tolerable. The range in which the difference is tolerable is a range in which the absolute value of the difference between the conversion efficiency of the first converter 31 and the conversion efficiency of the second converter 32 is equal to or less than a predetermined threshold. The range in which the difference is tolerable is, for example, equal to or greater than a lower limit D0 and equal to or less than an upper limit D1. The value obtained by subtracting the first conversion efficiency A1 from the third conversion efficiency B1 corresponding to the lower limit D0 is equal to the value obtained by subtracting the fourth conversion efficiency B2 from the second conversion efficiency A2 corresponding to the upper limit D1. The predetermined value D is stored, for example, in the memory unit 61.

[0039] When the current value is equal to or greater than the predetermined value D, the supply control unit 622 turns on the first switch 41 and turns off the second switch 42. As a result, the output current is supplied to the first converter 31 and not to the second converter 32. In this way, when the current value of the output current is equal to or greater than the predetermined value D, the supply control unit 622 can cause the first converter 31, which has high conversion efficiency at high currents, to supply the output current to the motor 11 and the electrical device 5, thereby reducing power consumption.

[0040] When the current value is less than the predetermined value D, the supply control unit 622 turns off the first switch 41 and turns on the second switch 42. As a result, the output current is supplied to the second converter 32 and not to the first converter 31. In this way, when the current value of the output current is less than the predetermined value D, the supply control unit 622 can cause the second converter 32, which has high conversion efficiency at low current, to supply the output current to the electrical device 5. In this way, the supply control unit 622 can supply power using a converter with high conversion efficiency depending on the current value, thereby reducing excess power consumption.

[0041] The supply control unit 622 may cause the first converter 31 to supply the output current to the electric device 5 even if the current value is less than the predetermined value D. For example, when the current value is less than the predetermined value D and the conversion efficiencies of the first converter 31 and the third converter 33 are higher than the conversion efficiency of the second converter 32, the supply control unit 622 causes the first converter 31 to supply the output current. Specifically, when the product of the conversion efficiency of the first converter 31 and the conversion efficiency of the third converter 33, corresponding to the current value of the output current, is higher than the conversion efficiency of the second converter 32, the supply control unit 622 causes the third converter 33 to supply the current to the electric device 5 via the first converter 31. In this way, the supply control unit 622 can supply power to the electric device 5 using the second converter 32 or the first converter 31 or the third converter 33, whichever has the higher conversion efficiency, thereby reducing excess power consumption.

[0042] The supply control unit 622 controls the first converter 31 to supply power to the electric device 5 when the current value is less than a predetermined value D but the current value becomes equal to or greater than the predetermined value D when the output current is supplied to a device other than the electric device 5. Specifically, when the current value is less than the predetermined value D and the current value becomes equal to or greater than the predetermined value D when the battery 35 is charged, the supply control unit 622 controls the first converter 31 to supply the output current to the battery 35 and the electric device 5. In this case, the acquisition unit 621 acquires a charging current value required to charge the battery 35. When the sum of the motor current value and the device current value plus the charging current value is equal to or greater than a predetermined value, the supply control unit 622 controls the first converter 31 to supply the first converted current to the battery and the electric device 5. In this way, the supply control unit 622 can more efficiently use the electric power generated by the fuel cell 21.

[0043] [Converter switching process] 4 is a flowchart showing an example of the converter switching process. The converter switching process is performed at predetermined intervals while the fuel cell 21 is operating. The predetermined interval is, for example, 100 milliseconds, but is not limited to this.

[0044] The acquisition unit 621 acquires a motor current value for driving the motor 11 (step S1). Specifically, the acquisition unit 621 acquires the motor current value from an ECU that controls the motor 11. The acquisition unit 621 acquires a device current value for driving the electric device 5 (step S2). The acquisition unit 621 acquires the device current value from the electric device 5. Note that step S2 may be executed before step S1 or may be executed in parallel with step S1.

[0045] The supply control unit 622 determines whether the sum of the motor current value and the device current value is equal to or greater than a predetermined value D (step S3). If the sum is equal to or greater than the predetermined value D (Yes in step S3), the supply control unit 622 causes the first converter 31 to supply output current to the motor 11 and the electric device 5 (step S4). Specifically, the supply control unit 622 turns on the first switch 41 and turns off the second switch 42, causing the first converter 31 to supply output current but not the second converter 32. The first converter 31 supplies the first converted current to both the motor 11 and the electric device 5 via the inverter 34.

[0046] If the sum is less than the predetermined value D (No in step S3), the acquisition unit 621 acquires the product of the conversion efficiencies of the first converter 31 and the third converter 33 corresponding to the current value of the output current (step S5). The supply control unit 622 acquires the conversion efficiency of the second converter 32 corresponding to the current value of the output current (step S6). Note that step S6 may be executed before step S5 or in parallel with step S5.

[0047] The supply control unit 622 determines whether the product of the conversion efficiencies is less than the conversion efficiency of the second converter 32 (step S7). If the product of the conversion efficiencies is less than the conversion efficiency of the second converter 32 (Yes in step S7), the supply control unit 622 causes the second converter 32 to supply an output current to the electric device 5 (step S8). Specifically, the supply control unit 622 turns off the first switch 41 and turns on the second switch 42 to cause the second converter 32 to supply an output current but not the first converter 31. The second converter 32 supplies the second converted current only to the electric device 5. If the product of the conversion efficiencies is equal to or greater than the conversion efficiency of the second converter 32 (No in step S7), the supply control unit 622 proceeds to step S4.

[0048] (Variation 1) The supply system S according to the above embodiment supplies power from the fuel cell 21 to the electrical device 5 via the inverter 34 and the third converter 33 when the current value is equal to or greater than a predetermined value. However, the inverter 34 and the third converter 33 consume power when converting the current. In other words, the supply system S according to the embodiment converts DC current to AC current and then converts it back to DC current, consuming excess power.

[0049] 5 is a diagram illustrating a supply system S according to Modification 1. The supply system S according to Modification 1 has a converter 361 and a converter 362 instead of the third converter 33. The fuel cell 21 according to Modification 1 outputs a DC current with a voltage value higher than the rated voltage of the electrical device 5.

[0050] The first converter 31 and the battery 35 of the supply system S according to the first modification example are connected without the inverter 34. A converter 361 is provided on an electric wire connecting the first converter 31 and the battery 35. The converter 361 is a DC / DC converter. The converter 361 converts the voltage value of the direct current supplied from the first converter 31 to a voltage value at which the battery 35 can be charged, and converts the voltage value of the direct current supplied from the battery 35 to a rated voltage of the motor 11. The electric wire connecting the first converter 31 and the converter 361 branches at a branch point 44 and is connected to the inverter 34.

[0051] The electric wire connecting the first converter 31 and the converter 361 branches at a branch point 45 between the branch point 44 and the converter 361, and is connected to the electric device 5. A converter 362 is provided between the branch point 45 and the electric device 5. The converter 362 is a voltage conversion circuit that converts the voltage of a direct current to a lower voltage, and is a so-called step-down DC / DC converter. The converter 362 steps down the voltage value that has been boosted to the rated voltage of the motor 11 by the first converter 31 or the converter 361 to the rated voltage of the electric device 5. As described above, the supply system S according to the first modification does not use the inverter 34 when supplying power from the battery 35 to the electric device 5, and therefore does not convert the direct current back to an alternating current. In other words, the supply system S according to the first modification can reduce unnecessary power consumption and improve the efficiency of voltage conversion.

[0052] (Variation 2) The configuration in which the power of the fuel cell 21 and the power of the battery 35 are supplied to the electric device 5 without going through the inverter 34 is not limited to Modification 1. Fig. 6 is a diagram for explaining a supply system S according to Modification 2. The supply system S according to Modification 2 has converters 371, 372, and 373 instead of the converters 361 and 362 of Modification 1. Furthermore, the fuel cell 21 according to Modification 2 outputs a DC current with a voltage value higher than the rated voltage of the electric device 5.

[0053] The converter 371 is provided between the first converter 31 and the battery 35. The converter 371 is a DC / DC converter. The converter 371 converts the voltage value of the direct current supplied from the first converter 31 into a voltage value that can charge the battery 35, and converts the voltage value of the direct current supplied from the battery 35 into a rated voltage of the motor 11. The electric wire connecting the converter 371 and the fuel cell 21 branches at a branch point 44 and is connected to the inverter 34.

[0054] The converter 372 is provided between the battery 35 and the electric device 5. Specifically, the converter 372 is provided on an electric wire that branches off at a branch point 45 from an electric wire connecting the battery 35 and the converter 371 and is connected to the electric device 5. The converter 372 is a so-called step-down DC / DC converter.

[0055] The converter 373 is provided on an electric wire branching at a branch point 47 of an electric wire 46 connecting the second switch 42 and the second converter 32. Specifically, the converter 373 is provided on an electric wire connecting the branch point 47 and a connection point 48 between the branch point 44 and the converter 371. The converter 373 is a DC-DC converter with high conversion efficiency at low currents. The converter 373 is a boost converter that converts the voltage value of an input direct current into a voltage value higher than that voltage value.

[0056] When the current value is less than a predetermined value, the supply system S turns on the second switch 42 to supply power from the fuel cell 21 to the second converter 32 and the converter 373. The converter 373 is a DC-DC boost converter that boosts the voltage value of the direct current supplied from the fuel cell 21 to a voltage value capable of driving the motor 11. The converter 373 has a higher conversion efficiency at low currents than at high currents, and therefore can convert voltage with high conversion efficiency even when the voltage value of the output current of the fuel cell 21 is less than a predetermined value.

[0057] The supply system S according to the second modification includes an electric device 51 driven by an AC current, in addition to the electric device 5 driven by a DC current. The electric device 51 is connected to an electric wire branching off from an electric wire connecting the inverter 34 and the motor 11. The electric device 51 is, for example, an air conditioner (air compressor) or a group of devices (pumps, valves, injectors, regulators, etc.) for driving the fuel cell 21. In this way, the supply system S can drive the electric device 51 with the AC current converted by the inverter 34, eliminating the need to provide a separate inverter for driving the electric device 51, thereby simplifying the configuration.

[0058] (Variation 3) Fig. 7 is a diagram illustrating a supply system S according to Modification 3. The supply system S in Fig. 7 has a single changeover switch 49 instead of two on / off switches, the first switch 41 and the second switch 42. The changeover switch 49 can switch between supplying a first converted current from the first converter 31 to the motor 11 and the electric device 5, and supplying a second converted current from the second converter 32 to the electric device 5. The supply control unit 622 can switch the converter that converts the output current of the fuel cell 21 by switching the changeover switch 49.

[0059] Furthermore, the first converter 31 and the battery 35 of the supply system S according to the third modification are directly connected without passing through the inverter 34. The first converter 31 and the third converter 33 are also directly connected without passing through the inverter 34. The battery 35 and the third converter 33 are also directly connected without passing through the inverter 34. In this way, in the supply system S according to the modification, each component is directly connected without passing through the inverter 34, so that DC current can be directly supplied without voltage conversion by the inverter 34. In other words, in the supply system S, after DC voltage is converted into AC current by the inverter 34, the converted AC current is not converted back into DC current, so that unnecessary voltage conversion can be suppressed.

[0060] [Effects of Supply System S] The supply system S has a first converter 31 that has a second conversion efficiency A2 higher when the current value is equal to or greater than a predetermined value than a first conversion efficiency A1 when the current value is less than a predetermined value D, and a second converter 32 that has a third conversion efficiency B1 higher than the first conversion efficiency A1 when the current value is less than the predetermined value D. When the current value of the output current of the fuel cell 21 is equal to or greater than the predetermined value D, the supply system S supplies the motor 11 and the electric device 5 with a first converted current whose voltage has been converted using the first converter 31. When the current value is less than the predetermined value D, the supply system S supplies the electric device 5 with a second converted current whose voltage has been converted using the second converter 32.

[0061] In this way, the supply system S can convert the voltage to a voltage appropriate for the motor 11 or electrical device 5 that uses the power, using a converter with higher conversion efficiency, depending on the current value of the output current of the fuel cell. As a result, the supply system S can increase the conversion efficiency when converting the voltage of the output current, thereby reducing the power consumption when converting the voltage of the output current.

[0062] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by functionally or physically distributing or integrating any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination also have the effects of the original embodiments. [Explanation of symbols]

[0063] S Supply System 11 Motor 12 Driven equipment 21 Fuel Cell 22 Hydrogen Tank 31 First Converter 32 Second Converter 33 Third Converter 34 Inverter 35 Battery 41 First Switch 42 Second Switch 43 Branching Point 49 Changeover switch 5. Electrical Equipment 6. Supply control device 61 Storage section 62 Control Unit 621 Acquisition Department 622 Supply control section

Claims

1. a first converter that supplies a first converted current obtained by converting the voltage of an output current of a fuel cell to a motor and an electrical device other than the motor, the first converter having a second conversion efficiency higher than a first conversion efficiency when the current value of the output current is equal to or greater than a predetermined value; a second converter provided in parallel with the first converter and configured to supply a second converted current obtained by converting a voltage of the output current to the electrical device, the second converter having a third conversion efficiency higher than the first conversion efficiency when the current value is less than the predetermined value; a supply control unit that causes the first converter to supply the first converted current to the motor and the electrical device when the current value is equal to or greater than the predetermined value, and causes the second converter to supply the second converted current to the electrical device when the current value is less than the predetermined value; A supply system having:

2. one or more switches for switching whether the first converter supplies the output current or not and whether the second converter supplies the output current or not; the supply control unit switches the one or more switches to cause the first converter to supply the output current when the current value is equal to or greater than the predetermined value, and causes the second converter to supply the output current when the current value is less than the predetermined value. The delivery system of claim 1 .

3. the first converter is a converter that boosts a voltage of the output current to a voltage that can drive the motor, the second converter is a converter that steps down a voltage of the output current to a voltage that can drive the electrical device.

3. A supply system according to claim 1 or 2.

4. the output current of the fuel cell is a direct current; an inverter provided between the first converter and the motor and capable of converting direct current into alternating current; a third converter provided between the inverter and the electric device, for converting AC current output by the inverter into DC current capable of driving the electric device and supplying the DC current to the electric device; The delivery system of claim 3 .

5. the supply control unit controls the third converter to supply current to the electrical device via the first converter when the product of the conversion efficiency of the first converter corresponding to the current value and the conversion efficiency of the third converter corresponding to the current value is higher than the efficiency of the second converter corresponding to the current value, even if the current value is less than the predetermined value.

5. The delivery system of claim 4.

6. the predetermined value is set within a predetermined range including a current value at which the conversion efficiency of the first converter, which changes depending on the current value, and the conversion efficiency of the second converter, which changes depending on the current value, match.

3. A supply system according to claim 1 or 2.

7. an acquisition unit that acquires a motor current value for driving the motor and a device current value for driving the electrical device; the supply control unit controls the first converter to supply the first converted current to the motor and the electric device when the sum of the motor current value and the electric device current value is equal to or greater than the predetermined value, and controls the second converter to supply the second converted current to the electric device when the current value is less than the predetermined value.

3. A supply system according to claim 1 or 2.

8. a battery for supplying power to at least one of the motor and the electrical device; the acquisition unit acquires a charging current value required to charge the battery, the supply control unit controls the first converter to supply the first converted current to the battery and the electrical device when a value obtained by adding the charging current value to the sum of the motor current value and the device current value is equal to or greater than the predetermined value, even if the sum of the motor current value and the device current value is less than the predetermined value.

8. The delivery system of claim 7.

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