Method for starting a fuel cell system and fuel cell system

Abstract

A method for starting a fuel cell system 10 comprising a fuel cell 18 and a boost converter 100 having a capacitor 130 in its output stage, comprising: step S2 supplying hydrogen gas to the anode electrode 57 while the fuel cell is not started, generating an electromotive force based on the activity difference of the hydrogen gas between the anode electrode and the cathode electrode 56, thereby configuring the fuel cell as a hydrogen concentration cell; and step S3 precharging the capacitor with power Pfc supplied from the fuel cell configured as a hydrogen concentration cell.

Description

Technical Field

[0001] The present disclosure relates to a method for starting a fuel cell system that generates electricity through an electrochemical reaction between a fuel gas and an oxidant gas, and a fuel cell system.

Background Art

[0002] In recent years, in order to enable more people to access affordable, reliable, sustainable, and advanced energy, research and development on fuel cells that contribute to energy efficiency have been carried out.

[0003] Japanese Patent No. 7533678 discloses a power system for an electric vehicle that performs pre-charging using a boost converter.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] There is a long-felt need for a better method for starting a fuel cell system and a fuel cell system. For the widespread use of fuel cell systems, minimization of the number of components through integration of functional components and cost reduction are required. In particular, a pre-charge contact used in an application where a fuel cell system is coupled with other systems in a vehicle is a component that is used only when the vehicle system is started and is a device that is not utilized for most of the usage time of the vehicle system, so simplification is strongly required.

[0006] The present disclosure aims to solve the above-described problems.

Means for Solving the Problems

[0007] A first aspect of the present disclosure is a method for starting a fuel cell system comprising: a fuel cell that generates electricity by an electrochemical reaction between hydrogen gas supplied from a fuel gas supply device to an anode electrode and an oxidant gas supplied from an oxidant gas supply device to a cathode electrode; and a boost converter having a capacitor in its output stage and boosting the output voltage of the fuel cell, the method comprising: supplying the hydrogen gas to the anode electrode while the fuel cell is not started, generating an electromotive force between the anode electrode and the cathode electrode based on the activity difference of the hydrogen gas, thereby configuring the fuel cell as a hydrogen concentration cell; and precharging the capacitor with power supplied from the fuel cell configured as a hydrogen concentration cell.

[0008] A second aspect of the present disclosure is a fuel cell system comprising: a fuel cell that generates electricity by an electrochemical reaction between hydrogen gas supplied from a fuel gas supply device to an anode electrode and an oxidant gas supplied from an oxidant gas supply device to a cathode electrode; a boost converter having a capacitor in the output stage for boosting the output voltage of the fuel cell; and a control device that controls the fuel gas supply device, the oxidant gas supply device, the fuel cell, and the boost converter, wherein the control device drives the fuel gas supply device when the fuel cell is not running, supplies the hydrogen gas to the anode electrode, generates an electromotive force based on the activity difference of the hydrogen gas between the anode electrode and the cathode electrode, configures the fuel cell as a hydrogen concentration cell, and precharges the capacitor with the power supplied from the fuel cell configured as a hydrogen concentration cell. [Effects of the Invention]

[0009] This disclosure may provide a better method for starting a fuel cell system and a better fuel cell system. [Brief explanation of the drawing]

[0010] [Figure 1]Figure 1 is a schematic diagram of a fuel cell vehicle incorporating a fuel cell system according to the embodiment. [Figure 2] Figure 2 is a schematic diagram of the FCVCU (Fuel Cell Voltage Control Unit). [Figure 3] Figure 3 is a flowchart illustrating the startup process of a fuel cell system. [Figure 4] Figure 4 is a flowchart illustrating the pre-charging process using a hydrogen concentration cell. [Figure 5] Figure 5 is a schematic diagram of the FCVCU (Fuel Cell Voltage Control Unit) in the comparative example. [Modes for carrying out the invention]

[0011] Conventionally, fuel cell systems have been proposed that include a fuel cell, a secondary battery, and a boost converter having a smoothing capacitor in the output stage, which boosts the output voltage of the fuel cell and applies it to the load and the secondary battery.

[0012] Conventional fuel cell systems include a main contactor and a pre-charge circuit connected in parallel with the main contactor, between the smoothing capacitor and the secondary battery. The pre-charge circuit comprises a pre-charge contactor and a current-limiting resistor connected in series with the contactor. Before starting the fuel cell, this fuel cell system first closes the pre-charge contactor and charges the smoothing capacitor with the output power of the secondary battery via the current-limiting resistor. After the voltage across the terminals of the smoothing capacitor rises and the risk of welding due to overcurrent is eliminated, the main contactor is closed and the fuel cell is started. Charging the smoothing capacitor via the pre-charge circuit before closing the main contactor is called pre-charging.

[0013] The precharge circuit is only used for precharging the smoothing capacitor. After starting the fuel cell, the precharge circuit is not used again until the fuel cell is started again. The operating time of the precharge circuit is very short compared to the operating time of the entire fuel cell system.

[0014] Therefore, if the smoothing capacitor can be precharged without using the precharge circuit, the precharge circuit (precharge contactor and current limiting resistor) can be removed, enabling minimization of the number of parts and cost reduction of the fuel cell system.

[0015] In the present disclosure, the capacitor can be precharged without using the precharge circuit. Hereinafter, the startup method of the fuel cell system of the present disclosure and the fuel cell system will be described.

[0016] [Embodiment] FIG. 1 is a schematic configuration diagram of a fuel cell vehicle 12 incorporating a fuel cell system 10 according to an embodiment.

[0017] Note that the fuel cell system 10 can also be incorporated into other moving bodies such as ships, aircraft, and other flying bodies, and robots, other than the fuel cell vehicle 12.

[0018] [Configuration of Fuel Cell System] The fuel cell vehicle 12 includes a fuel cell system 10, an output device 14 electrically connected to the fuel cell system 10, and a control device 16 that controls the entire fuel cell vehicle 12 (including the fuel cell system 10 and the output device 14). The control device 16 may be divided into two or more control devices, for example, one for the fuel cell system 10 and one for the output device 14, instead of being a single one.

[0019] The fuel cell system 10 includes a fuel cell stack (simply referred to as a fuel cell, also FC) 18, an oxidant gas supply device 22, a fuel gas supply device 24, and a refrigerant supply device 26.

[0020] The oxidizer gas supply system 22 includes an air compressor (CP) 28 and a humidifier (HUM) 30. The fuel gas supply system 24 includes a fuel tank (hydrogen tank, fuel gas tank) 20, an injector (INJ) 32, an ejector 34, and a gas-liquid separator 36. The injector 32 may be replaced with a pressure reducing valve. The refrigerant supply system 26 includes a refrigerant pump (WP) 38 and a radiator 39.

[0021] The output device 14 includes a voltage conversion unit 42, a power storage unit 43, and a motor (electric motor) 46. The voltage conversion unit 42 includes an inverter 45, an FCVCU (Fuel Cell Voltage Control Unit) 40, and a step-up / step-down DC / DC converter (SUDC) 41. The power storage unit 43 includes a high-voltage power storage device (high-voltage battery, HV BAT) 44, a step-down DC / DC converter (SDC) 47, and a low-voltage power storage device (low-voltage battery, LV BAT) 48.

[0022] A load is connected to the voltage conversion unit 42 and the energy storage unit 43. The load includes a motor 46 as the main unit, high-voltage auxiliary equipment supplied with power from a high-voltage energy storage device 44, and low-voltage auxiliary equipment supplied with power from a low-voltage energy storage device 48. The high-voltage auxiliary equipment includes, for example, a compressor 28, a refrigerant pump 38, and heaters (electric heaters) 60 and 62, which will be described later. The low-voltage auxiliary equipment includes a control device 16, various sensors, various solenoid valves, and injectors 32, etc.

[0023] As shown in Figure 2, the FCVCU40 has a DC / DC converter (SUC, boost converter) 100, which is a boost converter. The DC / DC converter 100 boosts the output voltage Vfc, which is the generated voltage of the DC voltage from the fuel cell stack 18, and applies a high voltage for driving to the DC terminal of the inverter 45, the DC / DC converter 41, and the aforementioned high-voltage auxiliary equipment. Details of the FCVCU40 will be described later.

[0024] Returning to Figure 1, the DC / DC converter 41 steps down the high voltage used for driving to the battery voltage Vbh of the energy storage device 44 and charges the high-voltage energy storage device 44. The DC / DC converter 47 steps down the battery voltage Vbh to the low-voltage battery voltage Vbl and charges the low-voltage energy storage device 48.

[0025] A high voltage, obtained by boosting the battery voltage Vbh by the DC / DC converter 41, is applied to the DC terminal of the inverter 45. In addition, a high voltage, obtained by boosting the output voltage Vfc by the FCVCU 40, is applied to the DC terminal of the inverter 45.

[0026] The inverter 45 converts the DC high voltage into a three-phase AC to drive the motor 46. The inverter 45 converts the regenerative voltage of the motor 46 into a DC high voltage. This DC high voltage is converted to a low voltage by the DC / DC converter 41 and applied to the high-voltage energy storage device 44 to charge the high-voltage energy storage device 44. The fuel cell vehicle 12 is driven by the driving force generated by the motor 46.

[0027] The fuel cell stack 18 comprises a plurality of power generation cells 50. The plurality of power generation cells 50 are stacked between end plates 64 and 66. Each power generation cell 50 comprises an electrolyte membrane / electrode structure 52 and separators 53 and 54 that sandwich the electrolyte membrane / electrode structure 52.

[0028] The electrolyte membrane / electrode structure 52 comprises, for example, a solid polymer electrolyte membrane 55 which is a thin film of perfluorosulfonic acid containing water, and a cathode electrode 56 and an anode electrode 57 that sandwich the solid polymer electrolyte membrane 55.

[0029] The cathode electrode 56 and the anode electrode 57 have a gas diffusion layer (not shown) made of carbon paper or the like. An electrode catalyst layer (not shown) is formed on the surface of the gas diffusion layer by uniformly coating porous carbon particles on which a platinum alloy is supported on the surface. The electrode catalyst layer is formed on both sides of the solid polymer electrolyte membrane 55.

[0030] On the surface of one separator 53 facing the electrolyte membrane / electrode structure 52, a cathode channel (oxidant gas channel) 58 is formed along the cathode electrode 56. On the surface of the other separator 54 facing the electrolyte membrane / electrode structure 52, an anode channel (fuel gas channel) 59 is formed along the anode electrode 57.

[0031] Furthermore, the fuel cell stack 18 is equipped with a Cell Voltage Monitor (CVM) 96 that detects the voltage for each power generation cell 50, or for multiple power generation cells 50.

[0032] Plate-shaped heaters 60 and 62 are provided on the inside of the end plate 64 and the inside of the end plate 66, respectively. The heaters 60 and 62 heat the inside of the fuel cell stack 18 as needed.

[0033] The compressor 28 draws in outside air (atmosphere, air) from the outside air intake 70, pressurizes it, and supplies it to the fuel cell stack 18 through the humidifier 30.

[0034] An inlet-side sealing valve 74 is provided in the oxidizer gas supply channel 72, which connects the outside air intake 70 to the inlet of the cathode channel 58. Note that the channels such as the oxidizer gas supply channel 72, which are drawn with double lines, are formed by piping (the same applies hereinafter). The valve opening of the inlet-side sealing valve 74 can be variably controlled by the control device 16, and the inlet-side sealing valve 74 opens and closes the oxidizer gas supply channel 72.

[0035] An outlet-side sealing valve 78 is provided in the oxidizer off-gas discharge channel 76, which communicates with the outlet of the cathode channel 58. The outlet-side sealing valve 78 also functions as a back pressure valve. The valve opening of the outlet-side sealing valve 78 can be variably controlled by the control device 16, and the outlet-side sealing valve 78 opens and closes the oxidizer off-gas discharge channel 76.

[0036] The fuel tank 20 is a container that stores high-purity hydrogen compressed at high pressure. The fuel gas (hydrogen) discharged from the fuel tank 20 is supplied to the inlet of the anode passage 59 via an injector 32 and an ejector 34 provided in the fuel gas supply passage 80. The outlet of the anode passage 59 is connected to a gas-liquid separator 36 via a fuel off-gas discharge passage 82, and fuel off-gas is supplied to the gas-liquid separator 36.

[0037] The gas-liquid separator 36 separates the fuel off-gas into a gaseous component and a liquid component (liquid water). The gaseous component of the fuel off-gas (fuel off-gas) is supplied to the intake port of the ejector 34 through the circulation passage 84. The liquid component of the fuel off-gas (liquid water) is mixed with the exhaust gas discharged from the oxidizer off-gas discharge passage 76 and discharged to the outside (atmosphere) of the fuel cell vehicle 12 through the drain valve 86, the discharge passage 88, and the exhaust gas outlet 90.

[0038] The refrigerant supply device 26 includes a refrigerant passage 92 for circulating refrigerant (coolant), which is a heat transfer medium, a refrigerant pump 38, and a radiator 39. The refrigerant pump 38 circulates the refrigerant in the refrigerant passage 92.

[0039] Each component of the fuel cell system 10 described above is centrally controlled by the control device 16. The control device 16 is composed of an ECU (Electronic Control Unit). The ECU is composed of a computer having one or more processors (CPUs), memory, input / output interfaces, and electronic circuits. One or more processors (CPUs) execute programs (computer-executable commands) stored in memory (not shown).

[0040] The processor of the control device 16 performs calculations according to the program to control the operation of the fuel cell vehicle 12 and the fuel cell system 10.

[0041] The power switch (power SW) 94 of the fuel cell vehicle 12 is connected to the control device 16. The power switch 94 is operated by the user to start, continue (ON) or stop (OFF) the power generation operation of the fuel cell stack 18 of the fuel cell system 10.

[0042] [FCVCU Configuration] Figure 2 is a schematic diagram of the FCVCU40.

[0043] The FCVCU40 is a voltage converter equipped with a chopper-type DC / DC converter (SUC) 100. The FCVCU40 includes an input section 102 connected to the output terminal of the fuel cell stack 18, an input / output section 104 connected to the inverter 45, and an output section 106 connected to high-voltage auxiliary equipment such as a compressor 28. In addition to the inverter 45, the input / output section 104 is also connected to a high-voltage energy storage device 44 via a DC / DC converter 41 and a low-voltage energy storage device 48 via a DC / DC converter 47. Note that the DC / DC converter 47 and the energy storage device 48 are not shown in Figure 2.

[0044] The input unit 102 is equipped with a positive terminal P1 and a negative terminal N1. The input / output unit 104 is equipped with a positive terminal P2 and a negative terminal N2. The output unit 106 is equipped with a positive terminal P3 and a negative terminal N3 connected to the compressor 28, a positive terminal P4 and a negative terminal N4 connected to the refrigerant pump 38, and a positive terminal P5 and a negative terminal N5 connected to the heaters 60 and 62.

[0045] A DC / DC converter 100 and a main contactor 108 are provided between the input section 102 and the input / output section 104. The main contactor 108 functions as a switch that can be switched on and off (closed and open) by the control device 16.

[0046] The output unit 106 is connected to the secondary side of the DC / DC converter 100 and the primary side of the main contactor 108. When the main contactor 108 is turned on, the battery voltage Vbh is applied to the compressor inverter (INV) 228 via the output unit 106. Similarly, when the main contactor 108 is turned on, the battery voltage Vbh is applied to the refrigerant pump 38 and heaters 60 and 62 via the output unit 106.

[0047] The compressor 28, the refrigerant pump 38, and the heaters 60 and 62 are each equipped with smoothing capacitors 110, 112, and 114, respectively. These smoothing capacitors 110, 112, and 114 need to prevent overcurrent (inrush current) when the main contactor 108 is turned on.

[0048] The FCVCU40 is equipped with a current sensor 116, a voltage sensor 118, a current sensor 120, and a voltage sensor 122. The current sensor 116 detects the output current Ifc of the fuel cell stack 18 and outputs it to the control device 16. Similarly, the voltage sensor 118 detects the output voltage Vfc of the fuel cell stack 18, and the current sensor 120 detects the secondary current I2 of the DC / DC converter 100. The voltage sensor 122 detects the secondary voltage V2 of the DC / DC converter 100 (the terminal voltage of the smoothing capacitor 130, which will be described later). The detected current and voltage values ​​are all output to the control device 16.

[0049] The DC / DC converter 100 can employ various configurations, but as is well known, it basically consists of a reactor (inductor) 124, a switching element 126 such as a MOSFET or IGBT, a diode 128, and a smoothing capacitor (capacitor) 130. The switching element 126 is switched on / off (duty cycle controlled) by the control device 16 based on the power requirements of the load.

[0050] Specifically, as shown in FIG. 2, the DC / DC converter 100 includes a reactor 124, a switching element 126, a diode 128 (a unidirectional current passing element, a reverse current blocking element), a smoothing capacitor 130, and a discharge resistor 132. The switching element 126 is duty-controlled through a control device 16 that functions as a converter controller. Thereby, the DC / DC converter 100 boosts the output voltage Vfc of the fuel cell stack 18. Regarding the smoothing capacitor 130, it is necessary to prevent an overcurrent (inrush current) when the main contactor 108 is turned on.

[0051] When Vfc > V2, the fuel cell stack 18 and the smoothing capacitor 130 are directly connected through the reactor 124 and the diode 128, and the output voltage Vfc of the fuel cell stack 18 is directly connected to the voltage V2 between the terminals of the smoothing capacitor 130 without switching (however, V2 = Vfc - Vd ≒ Vfc, Vd << Vfc, Vd: forward voltage drop of the diode 128). The diode 128 operates as a boosting or direct connection and reverse current prevention function. Therefore, the DC / DC converter 100 performs a reverse current prevention operation and a direct connection operation (during power running, etc.) in addition to the boosting operation (during power running, etc.).

[0052] [Operation] The fuel cell system 10 according to this embodiment is basically configured as described above. Hereinafter, the startup method of the fuel cell system 10 will be described while referring to the flowcharts of FIGS. 3 and 4.

[0053] FIG. 3 is a flowchart for explaining the startup process of the fuel cell system 10. In the initial state, it is assumed that the power switch 94 of the fuel cell vehicle 12 is in the off state, and the fuel cell system 10 is in the soak state (operation stop state).

[0054] In the soak state, all valves of the fuel cell system 10 are closed. The cathode channel 58 of the fuel cell stack 18 is almost filled with a high concentration of inert gas (nitrogen gas) due to the power generation process during shutdown (so-called O2 lean power generation process). In addition to the inert gas (nitrogen gas), a small amount of water molecules may be present as water vapor in the cathode channel 58. An appropriate concentration of hydrogen gas remains in the anode channel 59 of the fuel cell stack 18.

[0055] In step S1, the power switch 94 receives an ON operation (FC start request) from the user. This initiates the start-up process of the fuel cell system 10.

[0056] Next, in step S2, the control device 16 controls the injector 32 to supply a predetermined amount of hydrogen gas to the anode flow path 59. The injector 32 can adjust the amount of fuel gas discharged by being driven, for example, by PWM control by the control device 16. As is well known, PWM driving is a power control method that creates a constant cycle of on and off pulse trains and changes the ON time width (ON duty cycle).

[0057] When hydrogen gas is supplied to the anode channel 59, the hydrogen concentration on the anode electrode 57 side increases. On the other hand, the cathode electrode 56 side is almost completely filled with a high concentration of inert gas (nitrogen gas). Therefore, the hydrogen concentration on the anode electrode 57 side is higher than the hydrogen concentration on the cathode electrode 56 side.

[0058] At this time, a hydrogen concentration cell is formed between the anode electrode 57, which has a high hydrogen concentration, and the cathode electrode 56, which has a low hydrogen concentration. That is, an electromotive force is generated based on the difference in the activity of the hydrogen gas. The activity of the hydrogen gas can be expressed as either its concentration or partial pressure.

[0059] Therefore, at the anode electrode 57 with a high hydrogen concentration, hydrogen molecules (H2) are ionized, and protons (H2) are formed. + ) and electrons (e - ) is generated. Protons (H) generated at the anode electrode 57 +The electrons (e) permeate the solid polymer electrolyte membrane 55 and move towards the cathode electrode 56 side where the hydrogen concentration is lower. - The fumes move from the output terminal of the fuel cell stack 18 to the cathode electrode 56 side via an external circuit (FCVCU 40).

[0060] At the cathode electrode 56, protons (H) that have permeated the solid polymer electrolyte membrane 55 and reached the cathode electrode 56 + ) electrons (e - The hydrogen molecules (H2) are then regenerated. These reactions continue until the hydrogen concentration on the anode electrode 57 and the hydrogen concentration on the cathode electrode 56 reach equilibrium.

[0061] The electromotive force of a hydrogen concentration cell can generally be calculated using the Nernst equation.

[0062] In step S2, when a predetermined amount of hydrogen gas is supplied to the anode channel 59, the process proceeds to step S3. In step S3, a pre-charge process of the smoothing capacitor 130 using a hydrogen concentration cell is performed.

[0063] Figure 4 is a flowchart illustrating the pre-charging process using a hydrogen concentration cell.

[0064] The pre-charge process (pre-charge operation) using hydrogen concentration cells begins with passive charging in step S31. Passive charging means keeping the switching element 126 of the FCVCU40 in the off state (open state) and directly connecting the fuel cell stack 18 and the smoothing capacitor 130 of the DC / DC converter 100 through the diode 128. When the switching element 126 is in the off state, the smoothing capacitor 130 is charged with the output voltage Vfc of the fuel cell stack 18 (the supply voltage as a hydrogen concentration cell).

[0065] When the switching element 126 is turned off (open), the smoothing capacitors 110, 112, and 114 provided on the compressor 28, refrigerant pump 38, and heaters 60 and 62 are also directly connected to the fuel cell stack 18 via the diode 128. As a result, the smoothing capacitors 110, 112, and 114 are also charged by the output voltage (supply voltage as a hydrogen concentration cell) Vfc of the fuel cell stack 18.

[0066] In step S32, it is determined whether or not charging by passive charging is complete. The control device 16 may, for example, compare the terminal voltage V2 of the smoothing capacitor 130 with a predetermined voltage value Vth1 during the execution of passive charging, and determine that charging by passive charging is complete if the terminal voltage V2 of the smoothing capacitor 130 reaches the predetermined voltage value Vth1. The predetermined voltage value Vth1 is set to a voltage value slightly lower than the output voltage Vfc of the fuel cell stack 18, taking into account the forward voltage drop Vd of the diode 128. If the terminal voltage V2 of the smoothing capacitor 130 is less than the predetermined voltage value Vth1, passive charging continues (step S32: NO).

[0067] In step S32, the control device 16 may determine the completion of passive charging using the output current Ifc of the fuel cell stack 18 instead of the terminal voltage V2 of the smoothing capacitor 130. That is, the control device 16 may determine that charging by passive charging is complete when the output current Ifc of the fuel cell stack 18 falls below a predetermined current value Ith during the execution of passive charging. The predetermined current value Ith is set to a value that, for example, prevents the charging current flowing into the smoothing capacitor 130 from becoming an overcurrent in the next step (step S33). This allows the system to proceed to the next step (step S33) and start active charging, which will be described later, even before the terminal voltage V2 of the smoothing capacitor 130 reaches a predetermined voltage value Vth1. If the output current Ifc of the fuel cell stack 18 is greater than or equal to the predetermined current value Ith, passive charging continues (step S32: NO).

[0068] Once the charging of the smoothing capacitor 130 by passive charging is complete (step S32: YES), proceed to step S33.

[0069] In step S33, the control device 16 starts the boost operation of the DC / DC converter 100. By controlling the on / off switching of the switching element 126, the DC / DC converter 100 boosts the output voltage Vfc of the fuel cell stack 18. As a result, more charge is stored in the smoothing capacitor 130, and the terminal voltage V2 of the smoothing capacitor 130 rises. Charging accompanied by the boost operation of the DC / DC converter 100 will be referred to as active charging below.

[0070] In active charging, the control device 16 may control the DC / DC converter 100 so that the output current Ifc of the fuel cell stack 18 becomes a predetermined current value (current control). The control device 16 may also control the DC / DC converter 100 so that the output voltage Vfc of the fuel cell stack 18 becomes a predetermined voltage value (voltage control). The control device 16 may also control the DC / DC converter 100 so that the power Pfc supplied from the fuel cell stack 18 is maximized (maximum power point tracking control, MPPT (Maximum Power Point Tracking) control).

[0071] Active charging continues until the terminal voltage V2 of the smoothing capacitor 130 reaches the target voltage (predetermined voltage value) Vth2 (step S34: NO). The target voltage Vth2 can be set to the high-voltage battery voltage Vbh of the energy storage device 44, or a value related to the battery voltage Vbh. When the smoothing capacitor 130 is charged to the target voltage Vth2 (step S34: YES), the control device 16 stops the boost operation of the DC / DC converter 100 in step S35 and terminates the pre-charge process using the hydrogen concentration battery.

[0072] Furthermore, hydrogen concentration cells have the characteristic that the concentration difference decreases and the electromotive force decreases as hydrogen is transported from the anode to the cathode during their operation. For this reason, it is desirable that the above pre-charge operation (steps S31 to S35) be completed in the shortest possible time so as to maintain a low hydrogen partial pressure to which the cathode is exposed.

[0073] Returning to the flowchart shown in Figure 3, in step S4, the control device 16 turns on the main contactor 108. At this time, the smoothing capacitor 130 has sufficient charge stored. The voltage difference |Vbh-V2| between the terminal voltage V2 of the smoothing capacitor 130 and the battery voltage Vbh becomes smaller than a predetermined threshold. Therefore, no large inrush current flows through the main contactor 108.

[0074] In step S5, the control device 16 starts the compressor 28. The inlet sealing valve 74 and the outlet sealing valve 78 are opened, and oxidizing gas is supplied to the cathode flow path 58. This allows hydrogen gas (H2 gas) generated on the cathode electrode 56 side to be scavenged and discharged from the exhaust gas outlet 90. The inlet sealing valve 74 and the outlet sealing valve 78 may be opened in advance before starting the compressor 28.

[0075] In step S6, the control device 16 starts the fuel cell (fuel cell stack) 18. While continuing to supply oxidant gas to the cathode electrode 56, hydrogen gas is supplied from the fuel tank 20 to the anode electrode 57. This starts the power generation of the fuel cell (fuel cell stack) 18 through the electrochemical reaction between the oxidant gas and hydrogen gas.

[0076] In step S35 described above, the control device 16 may proceed to step S4 without stopping the boosting operation of the DC / DC converter 100. That is, the control device 16 may start power generation of the fuel cell stack 18 without stopping the boosting operation of the DC / DC converter 100 and proceed to normal control (operation control) of the fuel cell stack 18.

[0077] [Comparative Example] Figure 5 is a schematic diagram of the FCVCU140 in a comparative example.

[0078] In the comparative example, the FCVCU140 is equipped with a pre-charge circuit 134. In the comparative example, the components other than the pre-charge circuit 134 are common to the components of the FCVCU40 shown in Figure 2, and therefore are given the same reference numerals as the components of the FCVCU40.

[0079] The precharge circuit 134 includes a precharge contactor 136 and a current-limiting resistor 138 connected in series with the precharge contactor 136. In this comparative example, the smoothing capacitor 130 is precharged with power supplied from a high-voltage energy storage device 44.

[0080] Specifically, when the fuel cell 18 is started, the pre-charge contactor 136 is first turned on (closed) while the main contactor 108 is in the off state. The battery voltage Vbh of the energy storage device 44 is applied to the smoothing capacitor 130 via the current limiting resistor 138, and the smoothing capacitor 130 is pre-charged by the power supplied from the energy storage device 44 via the current limiting resistor 138 and the pre-charge contactor 136. After the terminal voltage V2 of the smoothing capacitor 130 rises and the risk of overcurrent is eliminated, the main contactor 108 is turned on (closed), and the fuel cell 18 is started.

[0081] Thus, the pre-charge circuit 134 in the comparative example is a component used only when the fuel cell system 10 is started up, and is a device that is not utilized for most of the actual operating time of the fuel cell system 10, therefore simplification is required.

[0082] In contrast, the starting method for the fuel cell system 10 according to this embodiment includes step S2, which involves supplying hydrogen gas to the anode electrode 57 while the fuel cell 18 is not started, generating an electromotive force based on the activity difference (concentration difference, partial pressure difference) of the hydrogen gas between the anode electrode 57 and the cathode electrode 56, thereby configuring the fuel cell 18 as a hydrogen concentration cell; and step S3, which involves precharging the smoothing capacitor 130 with the power Pfc supplied from the fuel cell 18 configured as a hydrogen concentration cell.

[0083] Furthermore, the fuel cell system 10 according to this embodiment includes a control device 16, which drives the fuel gas supply device 24 when the fuel cell 18 is not running, supplies hydrogen gas to the anode electrode 57, generates an electromotive force based on the activity difference (concentration difference, partial pressure difference) of hydrogen gas between the anode electrode 57 and the cathode electrode 56, configures the fuel cell 18 as a hydrogen concentration cell, and precharges the smoothing capacitor 130 with the power Pfc supplied from the fuel cell 18 configured as a hydrogen concentration cell.

[0084] As a result, in this embodiment, the smoothing capacitor 130 can be pre-charged without using the pre-charge circuit 134 (pre-charge contactor 136 and current-limiting resistor 138). Consequently, there is no need to provide the pre-charge circuit 134 for the main contactor 108. The pre-charge circuit 134 can be removed from the FCVCU 140, which makes it possible to minimize the number of components in the fuel cell system 10 and reduce costs.

[0085] With regard to the embodiments described above, the following additional information is disclosed.

[0086] (Note 1) A method for starting a fuel cell system (10) according to the present disclosure comprises: a fuel cell (18) that generates electricity by an electrochemical reaction between hydrogen gas supplied from a fuel gas supply device (24) to an anode electrode (57) and oxidant gas supplied from an oxidant gas supply device (22) to a cathode electrode (56); and a boost converter (100) having a capacitor (130) in its output stage and boosting the output voltage (Vfc) of the fuel cell, the method for starting a fuel cell system comprising: (S2) supplying the hydrogen gas to the anode electrode while the fuel cell is not started, generating an electromotive force based on the activity difference of the hydrogen gas between the anode electrode and the cathode electrode, thereby configuring the fuel cell as a hydrogen concentration cell; and (S3) precharging the capacitor with power (Pfc) supplied from the fuel cell configured as a hydrogen concentration cell.

[0087] This method allows for precharging of the capacitor without the need for a precharge circuit. Therefore, it is possible to minimize the number of components in the fuel cell system, reduce costs, and provide a better starting method for the fuel cell system.

[0088] (Note 2) A method for starting a fuel cell system as described in Appendix 1, wherein the step of precharging the capacitor preferably includes the steps of: connecting the fuel cell and the capacitor, applying the output voltage of the fuel cell configured as a hydrogen concentration cell to the capacitor to charge the capacitor (S31); and, after the capacitor has been charged by the output voltage of the fuel cell, driving the boost converter to boost the output voltage of the fuel cell, applying the boosted voltage to the capacitor to charge the capacitor (S32).

[0089] This method allows for rapid pre-charging of the capacitor.

[0090] (Note 3) A method for starting a fuel cell system as described in Appendix 1 or 2, wherein the fuel cell system further comprises a power storage device (44), a contactor (108) provided between the power storage device and the capacitor, and an oxidant gas supply device connected in parallel with the capacitor on the primary side of the contactor, and preferably includes the steps of: determining that precharging of the capacitor is complete when the capacitor is charged to a predetermined voltage value (Vth2) (S34); and, when it is determined that precharging of the capacitor is complete, closing the contactor to supply power from the power storage device to the oxidant gas supply device to drive the oxidant gas supply device and supplying the oxidant gas from the oxidant gas supply device to the cathode electrode (S5).

[0091] This method allows hydrogen gas generated at the cathode electrode to be scavenged to the outside of the fuel cell stack.

[0092] (Note 4) A method for starting a fuel cell system as described in Appendix 1 or 2, wherein the fuel cell system further comprises: an energy storage device (44); a contactor (108) provided between the energy storage device and the capacitor; and auxiliary equipment (28, 38, 60, 66) connected in parallel with the capacitor on the primary side of the contactor, and preferably includes the steps of: determining that precharging of the capacitor is complete when the capacitor is charged to a predetermined voltage value (Vth2) (S34); closing the contactor and supplying power from the energy storage device to the auxiliary equipment when it is determined that precharging of the capacitor is complete (S5); and driving the auxiliary equipment based on the supplied power, supplying the hydrogen gas to the anode electrode and supplying the oxidizing gas to the cathode electrode, and generating electricity from the fuel cell by an electrochemical reaction between the hydrogen gas and the oxidizing gas (S6).

[0093] This method allows the capacitor to be pre-charged and the fuel cell to be started without using a pre-charge circuit.

[0094] (Note 5) The fuel cell system according to this disclosure comprises a fuel cell (18) that generates electricity by an electrochemical reaction between hydrogen gas supplied from a fuel gas supply device (24) to an anode electrode (57) and oxidant gas supplied from an oxidant gas supply device (22) to a cathode electrode (56); a boost converter (100) having a capacitor (130) in its output stage that boosts the output voltage (Vfc) of the fuel cell; and a control device (16) that controls the fuel gas supply device, the oxidant gas supply device, the fuel cell, and the boost converter, wherein the control device drives the fuel gas supply device when the fuel cell is not running, supplies the hydrogen gas to the anode electrode, generates an electromotive force based on the activity difference of the hydrogen gas between the anode electrode and the cathode electrode, configures the fuel cell as a hydrogen concentration cell, and precharges the capacitor with the power (Pfc) supplied from the fuel cell configured as a hydrogen concentration cell.

[0095] With this configuration, the capacitor can be pre-charged without using a pre-charge circuit. Therefore, it is possible to minimize the number of components in the fuel cell system, reduce costs, and provide a better fuel cell system.

[0096] Although the present disclosure has been described in detail above, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of the present disclosure or from the intent of the present disclosure derived from the claims and their equivalents. Furthermore, these embodiments can be implemented in combination. For example, the order of operations and processes in the embodiments described above are shown as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. [Explanation of Symbols]

[0097] 10…Fuel cell system 16…Control device 18…Fuel cell stack (fuel cell) 22…Oxidizer gas supply device 24...Fuel gas supply device 56...Cathode electrode 57... Anode electrode 100... DC / DC converter (boost converter) 130... Smoothing capacitor (capacitor) Pfc...Power supply Vfc...Output voltage

Claims

1. A fuel cell that generates electricity through an electrochemical reaction between hydrogen gas supplied to the anode electrode from a fuel gas supply device and oxidizer gas supplied to the cathode electrode from an oxidizer gas supply device, A boost converter having a capacitor in the output stage and boosting the output voltage of the fuel cell, A method for starting a fuel cell system comprising: The steps include: supplying the hydrogen gas to the anode electrode while the fuel cell is not running, generating an electromotive force based on the activity difference of the hydrogen gas between the anode electrode and the cathode electrode, thereby configuring the fuel cell as a hydrogen concentration cell; The steps include: precharging the capacitor with power supplied from the fuel cell configured as a hydrogen concentration cell; A method for starting a fuel cell system, comprising the following:

2. A method for starting a fuel cell system according to claim 1, The step of pre-charging the capacitor is: The steps include: connecting the fuel cell and the capacitor, applying the output voltage of the fuel cell configured as a hydrogen concentration cell to the capacitor to charge the capacitor; The steps include: charging the capacitor with the output voltage of the fuel cell, driving the boost converter to boost the output voltage of the fuel cell, applying the boosted voltage to the capacitor to charge the capacitor; A method for starting a fuel cell system, including the method described above.

3. A method for starting a fuel cell system according to claim 1 or 2, The aforementioned fuel cell system further, Energy storage device, A contactor is provided between the energy storage device and the capacitor, On the primary side of the contactor, the oxidizing gas supply device is connected in parallel with the capacitor, It has, The steps include determining that pre-charging of the capacitor is complete when the capacitor has been charged to a predetermined voltage value, When it is determined that the pre-charging of the capacitor is complete, the contactor is closed to supply power from the energy storage device to the oxidizer gas supply device to drive the oxidizer gas supply device, and the oxidizer gas is supplied from the oxidizer gas supply device to the cathode electrode. A method for starting a fuel cell system, comprising the following:

4. A method for starting a fuel cell system according to claim 1 or 2, The aforementioned fuel cell system further, Energy storage device, A contactor is provided between the energy storage device and the capacitor, On the primary side of the contactor, auxiliary equipment connected in parallel with the capacitor, It has, The steps include determining that pre-charging of the capacitor is complete when the capacitor has been charged to a predetermined voltage value, When it is determined that the pre-charging of the capacitor is complete, the contactor is closed and power is supplied from the energy storage device to the auxiliary equipment. The steps include: driving the auxiliary equipment based on the supplied power, supplying the hydrogen gas to the anode electrode and the oxidizing gas to the cathode electrode, and generating electricity in the fuel cell by the electrochemical reaction between the hydrogen gas and the oxidizing gas; A method for starting a fuel cell system, comprising the following:

5. A fuel cell that generates electricity through an electrochemical reaction between hydrogen gas supplied to the anode electrode from a fuel gas supply device and oxidizer gas supplied to the cathode electrode from an oxidizer gas supply device, A boost converter having a capacitor in the output stage and boosting the output voltage of the fuel cell, A control device that controls the fuel gas supply device, the oxidizer gas supply device, the fuel cell, and the boost converter, A fuel cell system comprising, The control device is The fuel gas supply device is driven while the fuel cell is not running, and the hydrogen gas is supplied to the anode electrode. The fuel cell is configured as a hydrogen concentration cell by generating an electromotive force based on the activity difference of the hydrogen gas between the anode electrode and the cathode electrode. The capacitor is pre-charged with power supplied from the fuel cell configured as a hydrogen concentration cell. Fuel cell system.

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