Power System

Abstract

The present invention relates to a power supply system that provides a technology capable of improving the supply performance of driving power while suppressing manufacturing costs and weight increases. The power supply system (100) is a power supply system connected to an electric generator (11) of an electric vehicle (1), and the power supply system (100) includes a fuel cell (101), a secondary battery (102), a voltage converter (103), and a switch (104). The fuel cell (101) is directly connected to the electric generator (11). The secondary battery (102) is connected to the electric generator (11) via the voltage converter (103). The switch (104) can switch between a first state and a second state. In the first state, the secondary battery (102) and the voltage converter (103) are connected in parallel with the fuel cell (101). In the second state, the secondary battery (102) and the voltage converter (103) are connected in series with the fuel cell (101).

Description

Technical Field

[0001] The present invention relates to a power supply system including a fuel cell and a secondary battery. Background Art

[0002] In recent years, interest in developing vehicles that help reduce CO2 emissions has grown due to climate-related disasters. Electric vehicles are known to use fuel cells and secondary batteries as power sources for their drive motors. For example, Patent Document 1 describes an electric vehicle that includes a fuel cell and a secondary battery connected in parallel, with voltage converters provided at each output terminal of the fuel cell and secondary battery. This structure allows the output power from the fuel cell and secondary battery to be boosted, resulting in a higher drive output.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-153242 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] However, in the structure of Patent Document 1, voltage converters are provided in the fuel cell and the secondary battery respectively, which causes problems of increased manufacturing cost and weight.

[0008] To address this issue, a voltage converter could be installed on one of the fuel cell and the secondary battery. However, since this voltage converter operates to align the voltages of the output power from the fuel cell and the secondary battery, the voltage of the driving power supplied to the driving motor will be the output voltage of the power supply on the side of the fuel cell or secondary battery that lacks the voltage converter. Furthermore, as the power output of the power supply increases, the voltage decreases, leading to insufficient voltage for the driving motor and difficulty in achieving sufficient power.

[0009] Furthermore, when a power source equipped with a voltage converter, such as a fuel cell or secondary battery, serves as the primary energy source for driving a vehicle, the energy transferred through the voltage converter increases, reducing the energy efficiency of the electric vehicle due to losses in the voltage converter. Furthermore, the circuit size of the voltage converter installed in the power source serving as the primary energy source for driving the vehicle increases, leading to increased manufacturing costs and weight.

[0010] In particular, in configurations where only the voltage converter is incorporated into the fuel cell, in addition to the aforementioned issues of increased manufacturing cost and weight, there is also the problem of constantly boosting the output voltage from the fuel cell, which reduces the energy efficiency of the electric vehicle. Furthermore, in this configuration, the voltage of the driving power supplied to the drive motor is the output voltage of the secondary battery. Therefore, compared to configurations where the voltage converter is incorporated into both the fuel cell and the secondary battery, the voltage supplied to the drive motor is insufficient, making it difficult to achieve high power.

[0011] In this regard, it is also possible to consider adopting a structure in which a voltage converter is provided in the secondary battery but not in the fuel cell. However, in such a structure, the voltage of the driving power supplied to the driving motor becomes the output voltage of the fuel cell, so the voltage of the driving motor is insufficient and it is difficult to obtain a large output.

[0012] The present invention provides a power supply system capable of improving driving power supply performance while suppressing increases in manufacturing cost and weight.

[0013] Solutions to Problems

[0014] The present invention relates to a power supply system connected to a motor unit of an electric vehicle, wherein:

[0015] The power supply system comprises:

[0016] fuel cells;

[0017] Secondary batteries;

[0018] voltage converter; and

[0019] switch,

[0020] The fuel cell is directly connected to the motor unit,

[0021] The secondary battery is connected to the motor unit via the voltage converter.

[0022] The switch can switch between a first state in which the secondary battery and the voltage converter are connected in parallel with the fuel cell and a second state in which the secondary battery and the voltage converter are connected in series with the fuel cell.

[0023] Effects of the Invention

[0024] According to the present invention, it is possible to improve the supply performance of driving power while suppressing increases in manufacturing cost and weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1This is a block diagram (part 1) showing a schematic configuration of an electric vehicle 1 equipped with a power supply system 100 according to an embodiment of the present invention.

[0026] Figure 2 This is a block diagram (part 2) showing a schematic configuration of an electric vehicle 1 equipped with a power supply system 100 according to an embodiment of the present invention.

[0027] Figure 3 This is a graph showing an example of the characteristics of DU10.

[0028] Figure 4 104 is a diagram showing an example of a change in the voltage of the driving power due to switching of the switch 104 .

[0029] Figure 5 1 is a diagram showing an example of a circuit configuration of the power supply system 100 .

[0030] Figure 6 This is a diagram (part 2) showing an example of the circuit configuration of the power supply system 100 .

[0031] Figure 7 10 is a diagram showing a configuration example of the voltage converter 103 and the switch 104 .

[0032] Figure 8 103 is a diagram showing another configuration example of the voltage converter 103 .

[0033] Figure 9 103 is a diagram showing still another configuration example of the voltage converter 103 .

[0034] Description of Reference Numerals

[0035] 1 Electric vehicles

[0036] 11 Motor generator (motor unit)

[0037] 100 Power System

[0038] 101 Fuel Cell

[0039] 102 Secondary Batteries

[0040] 103 Voltage Converter

[0041] 104 switch. DETAILED DESCRIPTION

[0042] Hereinafter, one embodiment of the power supply system of the present invention will be described with reference to the drawings.

[0043] (Implementation Method)

[0044] <Schematic Configuration of Electric Vehicle 1 Equipped with Power Supply System 100 According to One Embodiment of the Present Invention>

[0045] Figure 1 and Figure 2 This is a block diagram showing a schematic configuration of an electric vehicle 1 equipped with a power supply system 100 according to an embodiment of the present invention. Figure 1 、 Figure 2 The thick solid lines in the figure represent mechanical connections, the double dashed lines represent power wiring, and the thin solid arrows represent control signals. Figure 1 、 Figure 2 The illustrated electric vehicle 1 is a 1MOT type electric vehicle including a DU (Driving Unit) 10 and a power supply system 100 .

[0046] The DU 10 includes drive wheels W, a gearbox GB, a differential gear D, a motor generator (MG) 11 , and a PDU (Power Drive Unit) 13 .

[0047] The motor generator 11 is an example of a motor unit of the electric vehicle 1. It is driven by the driving power supplied from the power supply system 100 and generates power (torque) for the electric vehicle 1 to travel. The power generated by the motor generator 11 is transmitted to the drive wheels W via the gearbox GB including a variable speed or fixed speed and the differential gear D. In addition, the motor generator 11 operates as a generator when the electric vehicle 1 decelerates, thereby outputting the braking force of the electric vehicle 1. It should be noted that the regenerative power generated by the motor generator 11 operating as a generator is stored in the secondary battery 102 of the power supply system 100.

[0048] The PDU 13 converts the DC voltage into an AC voltage and applies the voltage to the motor generator 11. Furthermore, the PDU 13 converts the AC voltage input during the regenerative operation of the motor generator 11 into a DC voltage.

[0049] The power supply system 100 is capable of performing a driving operation in which driving power is supplied from the power supply system 100 to the motor generator 11 to generate power for the electric vehicle 1, as well as a regenerative operation in which the regenerated power from the motor generator 11 is stored in the secondary battery 102. The following description focuses on the driving operation as the operation of the power supply system 100. The terms "input" and "output" are used with reference to the flow of driving power during the driving operation of the power supply system 100.

[0050] The power supply system 100 includes a fuel cell (FC) 101 , a secondary battery (BATT) 102 , a voltage converter (VCU) 103 , and an ECU (Electronic Control Unit) 105 .

[0051] The fuel cell 101 includes a hydrogen tank, a hydrogen pump, and an FC stack. The hydrogen tank stores hydrogen, the fuel used to power the electric vehicle. The hydrogen pump adjusts the amount of hydrogen delivered from the tank to the FC stack. The hydrogen pump also adjusts the amount of hydrogen humidification by supplying the dried hydrogen stored in the tank to the FC stack via a water tank within the pump. The FC stack takes in the hydrogen supplied from the hydrogen pump and oxygen from the air, generating electrical energy through a chemical reaction. The electrical energy generated in the FC stack is supplied to the DU 10 or the secondary battery 102.

[0052] Fuel cell 101 can be applied to various fuel cells, including polymer electrolyte fuel cells (PEFC), phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC), and solid oxide fuel cells (SOFC). The closed-circuit voltage of fuel cell 101 fluctuates depending on the amount of discharge.

[0053] The secondary battery 102 includes multiple power storage cells such as lithium-ion batteries and nickel-metal hydride batteries, and supplies driving power to the motor generator 11 via the voltage converter 103. The secondary battery 102 is not limited to lithium-ion batteries, nickel-metal hydride batteries, or the like. For example, a capacitor or capacitor having a small storage capacity but capable of charging and discharging a large amount of power in a short period of time may also be used as the secondary battery 102.

[0054] The voltage converter 103 is a voltage converter that steps down the output voltage of the secondary battery 102 while maintaining the DC voltage. The voltage converter 103 is also called a DC / DC converter.

[0055] The characteristics of the fuel cell 101 and the characteristics of the secondary battery 102 are different from each other. As long as the fuel cell 101 is supplied with hydrogen and oxygen as fuel, it can continuously discharge a large current. However, from the principle of generating electricity through the electrochemical reaction of the supplied fuel gas, it is difficult to make the output power of the fuel cell 101 fluctuate discontinuously in a short period of time. Considering these characteristics, it can be said that the fuel cell 101 has the characteristics of a high-capacity power source. On the other hand, from the principle of generating electricity through the electrochemical reaction of internal active materials, it is difficult to make the secondary battery 102 continuously discharge a large current, but it is not difficult to make its output fluctuate discontinuously in a short period of time. Considering these characteristics, it can be said that the secondary battery 102 has the characteristics of a high-output power source.

[0056] The fuel cell 101 is directly connected to the motor generator 11. Direct connection to the motor generator 11 means, for example, connection to the motor generator 11 without going through a voltage converter (VCU). Figure 1 、 Figure 2 In the example of FIG, the fuel cell 101 is connected to the motor generator 11 not via a voltage converter but via the PDU 13 .

[0057] The secondary battery 102 is connected to the motor generator 11 via the voltage converter 103. That is, the input end of the voltage converter 103 is connected to the secondary battery 102, and the output end of the voltage converter 103 is connected to the motor generator 11. Figure 1 In the example of FIG, the secondary battery 102 is connected to the motor generator 11 via the voltage converter 103, the switch 104 and the PDU 13. Figure 2 In the example of FIG, the secondary battery 102 is connected to the motor generator 11 via the voltage converter 103 , the switch 104 , the fuel cell 101 , and the PDU 13 .

[0058] The switch 104 is a switch capable of switching the power supply system 100 between a first state and a second state. Figure 1 As shown, the first state is a state in which the secondary battery 102 and the voltage converter 103 are connected in parallel with the fuel cell 101. Figure 2 As shown, the second state is a state in which the secondary battery 102 and the voltage converter 103 are connected in series with the fuel cell 101 .

[0059] Specifically, if Figure 1 As shown, switch 104 switches power supply system 100 to a first state by connecting the output of voltage converter 103 between DU 10 and fuel cell 101. Switch 104 also switches power supply system 100 to a second state by connecting the output of voltage converter 103 to fuel cell 101. Switch 104 is, for example, a magnetic switch, and switching of switch 104 is controlled by ECU 105.

[0060] In the first state, the secondary battery 102 and the voltage converter 103 are connected in parallel with the fuel cell 101, so the voltage of the driving power supplied to the motor generator 11 is low. The first state may also be referred to as "FC direct connection mode."

[0061] In the second state, the secondary battery 102 and the voltage converter 103 are connected in series with the fuel cell 101, so the voltage of the driving power supplied to the motor generator 11 is increased. The second state may also be referred to as a "boost mode" or the like.

[0062] The ECU 105 is a control circuit that performs various controls in the electric vehicle 1. Specifically, the controls performed by the ECU 105 include switching control of the switch 104. The controls performed by the ECU 105 may also include control of the fuel cell 101, the PDU 13, and the like.

[0063] For example, ECU 105 controls switch 104 to switch between the first state and the second state based on the required output value for motor generator 11. The required output value for motor generator 11 is set by ECU 105 based on, for example, an operation by the driver of electric vehicle 1 (e.g., the amount of operation on the accelerator pedal of electric vehicle 1) and the travel speed of electric vehicle 1. ECU 105 may also use information about the road on which electric vehicle 1 is traveling to set the required output value for motor generator 11.

[0064] Specifically, ECU 105 controls switch 104 so that it enters the first state when the required output value for motor generator 11 is less than a predetermined value. Thus, when the required output value for motor generator 11 is low, secondary battery 102 and voltage converter 103 can be connected in parallel with fuel cell 101 to supply low-voltage driving power to DU 10.

[0065] Furthermore, ECU 105 controls switch 104 so that it enters the second state when the output value requested of motor generator 11 is greater than a predetermined value. Thus, when the output value requested of motor generator 11 is high, secondary battery 102 and voltage converter 103 are connected in series with fuel cell 101 to supply high-voltage drive power to DU 10, thereby generating high power in motor generator 11.

[0066] like Figure 1 、 Figure 2 As shown, the power supply system 100 is configured without providing a voltage converter for boosting the output power from the fuel cell 101 , thereby reducing the manufacturing cost and weight of the power supply system 100 .

[0067] In addition, the power supply system 100 has a switch 104 that can switch between a first state and a second state. In the first state, the fuel cell 101 is connected in parallel with the secondary battery 102 and the voltage converter 103. In the second state, the fuel cell 101 is connected in series with the secondary battery 102 and the voltage converter 103.

[0068] Thus, even in a configuration where a voltage converter for boosting the output power from the fuel cell 101 is not provided, it is possible to supply high-voltage drive power by switching to the second state when a large output is required. Additionally, when the required output value is not high, it is possible to supply low-voltage drive power to DU10 by switching to the first state. At this time, since the output voltage from the fuel cell 101 is not always boosted by a voltage converter, the energy efficiency can be improved. That is, it is possible to supply high-voltage drive power according to the required output or supply drive power with high energy efficiency, thereby improving the supply performance of the drive power of the power supply system 100.

[0069] <Characteristics of DU10>

[0070] Figure 3 It is a graph showing an example of the characteristics of DU10. Figure 3 The horizontal axis represents the voltage of the drive power supplied to DU10. Figure 3 The left vertical axis represents the power of the drive power supplied to DU10. Figure 3 The right vertical axis represents the power (torque) of the electric vehicle 1 generated by DU10.

[0071] DU characteristic 30 represents the characteristic of the power of the electric vehicle 1 generated by DU10 with respect to the voltage of the drive power supplied to DU10. As shown by DU characteristic 30, the higher the voltage of the drive power supplied to DU10, the greater the power of the electric vehicle 1 that can be obtained. The maximum rating 30a is the maximum rating in DU characteristic 30, and the continuous rating 30b is the continuous rating in DU characteristic 30.

[0072] The dotted line FC characteristic 31 represents the characteristics of the voltage and power in the output power from the fuel cell 101 in the case where a configuration with a voltage converter for boosting the output power from the fuel cell 101 is assumed. As shown by FC characteristic 31, the output power from the fuel cell 101 has the characteristic that the higher the power, the lower the voltage. It should be noted that this characteristic is not limited to the fuel cell 101 but is common to ordinary power supplies. In the example of FC characteristic 31, the output power from the fuel cell 101 is boosted by a voltage converter to provide the continuous rating 30b of DU characteristic 30.

[0073] FC characteristic 32 represents in the case of adopting Figure 1 , Figure 2As shown, the voltage and power characteristics of the output power from the fuel cell 101 are shown in a configuration where a voltage converter is not provided to boost the output power from the fuel cell 101, and where the number of cells in the fuel cell 101 is increased compared to the example of FC characteristic 31. As shown in FC characteristics 31 and 32, the voltage of the output power from the fuel cell 101 can be increased by increasing the number of cells. The continuous rated value 30b of the DU characteristic 30 can be provided based on FC characteristic 32.

[0074] The BATT assist characteristic 33 indicated by the dotted arrow extending from the FC characteristic 32 indicates the secondary battery 102 and the voltage converter 103 (see FIG. 1 ) connected in parallel to the fuel cell 101. Figure 1 ) assist characteristic. As shown in the BATT assist characteristic 33, by connecting the secondary battery 102 and the voltage converter 103 in parallel with the fuel cell 101, the voltage of the driving power supplied to the DU 10 is maintained at the voltage of the FC characteristic 32, and the driving power supplied to the DU 10 is added to the output power of the secondary battery 102.

[0075] However, the voltage of the driving power supplied to DU 10 cannot be increased using BATT assist characteristic 33. Therefore, in the first state where fuel cell 101 is connected in parallel with secondary battery 102 and voltage converter 103, the power of electric vehicle 1 can only reach continuous rated value 30b. A voltage shortfall 34, indicated by the dashed-dotted arrow, occurs relative to the maximum rated value 30a of DU characteristic 30.

[0076] In contrast, when the output value requested of the DU 10 (motor generator 11) exceeds the output value of the continuous rated value 30b, the ECU 105 of this embodiment controls the switch 104 to the second state, connecting the fuel cell 101 in series with the secondary battery 102 and the voltage converter 103. This allows the voltage obtained by the secondary battery 102 and the voltage converter 103 to be added to the voltage indicated by the FC characteristic 32. Consequently, the maximum rated value 30a of the DU characteristic 30 can be provided.

[0077] On the other hand, when the required output value for the DU 10 is less than or equal to the continuous rated value 30b, the ECU 105 controls the switch 104 to the first state, connecting the fuel cell 101 in parallel with the secondary battery 102 and the voltage converter 103. This ensures that the continuous rated value 30b of the DU characteristic 30 is provided without constantly boosting the output power of the fuel cell 101, thereby enabling the supply of driving power to the DU 10 with high energy efficiency.

[0078] <Voltage Change of Driving Power Due to Switching of Switch 104>

[0079] Figure 4 104 is a diagram showing an example of a voltage change of the driving power caused by switching of the switch 104. Figure 4 In FIG, the horizontal axis represents time and the vertical axis represents voltage. The supply voltage 40 represents the voltage of the driving power supplied from the power supply system 100 to the DU 10. Figure 4 , an example is shown in which the switch 104 is controlled by the ECU 105 to switch from the first state (FC direct connection mode) to the second state (boost mode) at time t1.

[0080] The FC voltage on the vertical axis represents the output voltage of the fuel cell 101 , and the BATT voltage on the vertical axis represents the output voltage of the secondary battery 102 .

[0081] In the first state, the fuel cell 101 is connected in parallel with the secondary battery 102 and the voltage converter 103, and the supply voltage 40 is the same as the output voltage (FC voltage) of the fuel cell 101. At this time, the voltage converter 103 performs a step-down 41 to reduce the output power of the secondary battery 102 to the FC voltage.

[0082] In the second state, the fuel cell 101 is connected in series with the secondary battery 102 and the voltage converter 103. The supply voltage 40 is obtained by adding the output voltage (FC voltage) of the fuel cell 101, the output voltage (BATT voltage) of the secondary battery 102, and the voltage change generated by the voltage converter 103. This allows the DU 10 to be supplied with driving power at a higher voltage than in the first state. It should be noted that the difference 42 between the supply voltage 40 in the first and second states is variable within the range of 0-BATT voltage.

[0083] <Circuit Configuration of Power Supply System 100>

[0084] Figure 5 and Figure 6 1 is a diagram showing an example of a circuit configuration of the power supply system 100. Figure 5 、 Figure 6 In the example, the power supply system 100 has Figure 1 、 Figure 2 In addition to the structure shown in FIG, a diode 106 is also provided. Figure 5 The illustration of ECU 105 is omitted. Figure 5 、 Figure 6 The output terminals “P” and “N” of each block in represent the positive pole (in other words, the high potential side) and the negative pole (in other words, the low potential side) of the output terminal of the block. Figure 5 Indicates the first state, Figure 6 Indicates the second state.

[0085] The diode 106 is provided between the DU 10 and the cathode of the fuel cell 101 in such a direction that current flows only from the DU 10 to the fuel cell 101. The cathode of the voltage converter 103 is connected between the DU 10 and the diode 106.

[0086] The input terminal of the switch 104 is connected to the positive terminal of the voltage converter 103. The switch 104 has two output terminals, one of which is connected between the positive terminal of the fuel cell 101 and the DU 10, and the other of which is connected between the negative terminal of the fuel cell 101 and the diode 106.

[0087] like Figure 5 As shown, when the switch 104 connects the positive electrode of the voltage converter 103 to the positive electrode of the fuel cell 101 and between the DU 10 , the fuel cell 101 is in the first state connected in parallel with the secondary battery 102 and the voltage converter 103 .

[0088] like Figure 6 As shown, when switch 104 connects the positive electrode of voltage converter 103 to the cathode of fuel cell 101 and diode 106, a second state is established in which fuel cell 101 is connected in series with secondary battery 102 and voltage converter 103. In this state, diode 106 is positioned so that current from the positive electrode of voltage converter 103 does not flow to the cathode of voltage converter 103 and DU 10.

[0089] <Configuration Example of Voltage Converter 103 and Switch 104>

[0090] Figure 7 10 is a diagram showing a configuration example of the voltage converter 103 and the switch 104 . Figure 7 The voltage converter 103 shown is a single-phase circuit using a step-down chopper. Specifically, Figure 7 The voltage converter 103 shown has a capacitor 71 , transistors 72 , 73 , diodes 74 , 75 , a capacitor 76 and a coil 77 .

[0091] A first terminal of capacitor 71 is connected to the positive electrode of secondary battery 102, and a second terminal of capacitor 71 is connected to the negative electrode of secondary battery 102. Transistors 72 and 73 are connected in series and in parallel with capacitor 71. Diodes 74 and 75 are connected in parallel with transistors 72 and 73, respectively.

[0092] A first end of coil 77 is connected between transistors 72 and 73, and a second end of coil 77 is connected to the positive terminal of voltage converter 103. A first end of capacitor 76 is connected between coil 77 and the positive terminal of voltage converter 103, and a second end of capacitor 76 is connected to the negative terminal of voltage converter 103. The negative terminal of voltage converter 103 is connected to the negative terminal of secondary battery 102, the second end of capacitor 71, the output terminal of transistor 73, and the second end of capacitor 76.

[0093] like Figure 7 As shown, switch 104 includes, for example, transistors 78 and 79 and a diode 80. A first end of transistor 78 is connected to the positive electrode of voltage converter 103, and a second end of transistor 78 is connected between the positive electrode of fuel cell 101 and DU 10. A first end of transistor 79 is connected to the positive electrode of voltage converter 103, and a second end of transistor 79 is connected between the negative electrode of fuel cell 101 and diode 106. Diode 80 is connected in parallel with transistor 78. It should be noted that transistor 79 is not connected in parallel with the diode.

[0094] The ECU 105 switches between the first state and the second state by switching the transistors 78 and 79 on and off. Specifically, the first state is achieved when the transistor 78 is on and the transistor 79 is off, and the second state is achieved when the transistor 78 is off and the transistor 79 is on.

[0095] exist Figure 7 In the example, a capacitor 61 is provided in the power supply system 100 . A first end of the capacitor 61 is connected between the positive electrode of the fuel cell 101 and the DU 10 , and a second end of the capacitor 61 is connected between the negative electrode of the fuel cell 101 and the diode 106 .

[0096] <Another Configuration Example of Voltage Converter 103>

[0097] Figure 8 103 is a diagram showing another configuration example of the voltage converter 103 . Figure 8 The voltage converter 103 shown is a two-phase magnetic coupling circuit in which two step-down choppers are connected in parallel. Specifically, Figure 8 The voltage converter 103 shown is Figure 7 In addition to the voltage converter 103 shown, the device further includes transistors 82 , 83 , diodes 84 , 85 , and a coil 87 , which are the same step-down chopper as the transistors 72 , 73 , diodes 74 , 75 , and coil 77 (step-down chopper).

[0098] Like transistors 72 and 73, transistors 82 and 83 are connected in series with each other and in parallel with capacitor 71. Diodes 84 and 85 are connected in parallel with transistors 82 and 83, respectively. A first end of coil 87 is connected between transistors 82 and 83, and a second end of coil 87 is connected to the positive terminal of voltage converter 103, that is, between transistors 78 and 79 of switch 104.

[0099] <Another Configuration Example of Voltage Converter 103>

[0100] Figure 9 This is a diagram showing another configuration example of the voltage converter 103. The voltage converter 103 is not limited to Figure 7 、 Figure 8 The structure shown can also be Figure 9 The structure shown. Figure 9 The voltage converter 103 shown is a circuit using a step-up / step-down chopper. Specifically, Figure 9 The voltage converter 103 shown has a capacitor 91, transistors 92, 93, diodes 94, 95, a capacitor 96 and a coil 97. Figure 9 In the structure of the voltage converter 103 shown in FIG. Figure 7 、 Figure 8 In the structure shown, the positive and negative electrodes of the secondary battery 102 are opposite. Figure 9 In the voltage converter 103 shown, even if the output voltage (BATT voltage) of the secondary battery 102 is low, it is possible to switch between the first state and the second state.

[0101] The above describes the embodiment of the present invention, but the present invention is not limited to the above embodiment and can be modified or improved as appropriate. It should be noted that the above embodiment can be modified or improved as appropriate. For example, the structure in which the voltage converter 103 steps down the output voltage of the secondary battery 102 is described, but the present invention is not limited to such a structure. For example, when the voltage converter 103 is Figure 9 In the case of the illustrated configuration, a configuration in which the voltage converter 103 boosts the output voltage of the secondary battery 102 may be employed.

[0102] While the control for switching between the first and second states based on the required output value of the motor generator 11 has been described, the present invention is not limited to this control. For example, when the power supply system 100 is in the first state, the ECU 105 may control the switch 104 to switch the power supply system 100 to the second state, under conditions that cover the output voltage (FC voltage) of the fuel cell 101 and the output voltage (BATT voltage) of the secondary battery 102. This eliminates the voltage difference between the FC voltage and the BATT voltage when the fuel cell 101, secondary battery 102, and voltage converter 103 are connected in parallel, thus preventing voltage converter 103 from becoming difficult to control.

[0103] While the description primarily focuses on the driving operation in which the power supply system 100 supplies driving power to the motor generator 11 to generate power for the electric vehicle 1, the ECU 105 can also control the switch 104 to place the power supply system in the first state during regenerative operation, where the regenerative power from the motor generator 11 is stored in the secondary battery 102. This allows the first state to supply driving power to the DU 10 with high energy efficiency during regenerative operation. It should be noted that during regenerative operation, the diode 106 operates so that the regenerative power from the DU 10 flows to the secondary battery 102 instead of the fuel cell 101.

[0104] While the configuration described above includes a diode 106 between the negative electrode of the fuel cell 101 and the DU 10, an on / off switch may be provided instead of the diode 106. In this case, the ECU 105 controls the on / off switch to be on in the first state and to be off in the second state.

[0105] In addition, at least the following matters are described in this specification: It should be noted that, although corresponding components in the above-mentioned embodiment are shown in parentheses, the present invention is not limited thereto.

[0106] (1) A power supply system (power supply system 100) connected to a motor unit (motor generator 11) of an electric vehicle (electric vehicle 1), wherein:

[0107] The power supply system comprises:

[0108] Fuel cell (fuel cell 101);

[0109] Secondary battery (secondary battery 102);

[0110] a voltage converter (voltage converter 103); and

[0111] switch (switch 104),

[0112] The fuel cell is directly connected to the motor unit,

[0113] The secondary battery is connected to the motor unit via the voltage converter.

[0114] The switch can switch between a first state in which the secondary battery and the voltage converter are connected in parallel with the fuel cell and a second state in which the secondary battery and the voltage converter are connected in series with the fuel cell.

[0115] According to (1), by adopting a structure that does not include a voltage converter for boosting the output power from the fuel cell, the manufacturing cost and weight of the power supply system can be reduced. In addition, by switching between the first state and the second state by a switch, it is possible to supply driving power with high energy efficiency or supply high-voltage driving power, thereby improving the driving power supply performance of the power supply system 100.

[0116] (2) The power supply system according to (1), wherein

[0117] The first state and the second state are switched by the switch according to a required output value of the motor unit.

[0118] According to (2), it is possible to switch between the first state in which drive power can be supplied with high energy efficiency and the second state in which high-voltage drive power can be supplied, in accordance with the required output of the motor unit.

[0119] (3) The power supply system according to (2), wherein

[0120] When the required output value is smaller than a predetermined value, the switch is switched to the first state.

[0121] When the requested output value is equal to or greater than the predetermined value, the switch is switched to the second state.

[0122] According to (3), when the required output of the motor unit is not high, the first state is set to supply driving power with high energy efficiency. In addition, when the required output of the motor unit is high, the second state is set to supply high-voltage driving power.

Claims

1. A power supply system connected to a motor unit of an electric vehicle, wherein: The power supply system comprises: fuel cells; Secondary batteries; voltage converters; as well as switch, The fuel cell is directly connected to the motor unit, The secondary battery is connected to the motor unit via the voltage converter. The switch can switch between a first state in which the secondary battery and the voltage converter are connected in parallel with the fuel cell and a second state in which the secondary battery and the voltage converter are connected in series with the fuel cell.

2. The power supply system according to claim 1, wherein: The first state and the second state are switched by the switch according to a required output value of the motor unit.

3. The power supply system according to claim 2, wherein: When the required output value is smaller than a predetermined value, the switch is switched to the first state. When the requested output value is equal to or greater than the predetermined value, the switch is switched to the second state.

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