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 an output stage, the method comprising step S2 of 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 of 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 the fuel cell system. [Background technology]

[0002] In recent years, research and development into fuel cells has been conducted to contribute to energy efficiency in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] Japanese Patent No. 7533678 discloses a power system for an electric vehicle that performs precharging using a boost converter. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7533678 Summary of the Invention [Problem to be solved by the invention]

[0005] A better fuel cell system startup method and fuel cell system are desired. To popularize fuel cell systems, minimizing the number of parts and reducing costs by integrating functional parts is required. In particular, precharge contactors, which are used to connect fuel cell systems to other systems within a vehicle, are components used only when starting the vehicle system and are devices that are not used during the majority of the vehicle system's operation. Therefore, there is a strong demand for simplification.

[0006] The present disclosure aims to solve the above-mentioned problems. [Means for solving the problem]

[0007] A first aspect of the present disclosure is a method for starting a fuel cell system including a fuel cell that generates electricity through an electrochemical reaction between hydrogen gas supplied to an anode electrode from a fuel gas supply device and oxidant gas supplied to a cathode electrode from an oxidant gas supply device, and a boost converter having a capacitor in an output stage that boosts the output voltage of the fuel cell, the method comprising the steps of supplying the hydrogen gas to the anode electrode when 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 pre-charging the capacitor with power supplied from the fuel cell configured as the hydrogen concentration cell.

[0008] A second aspect of the present disclosure is a fuel cell system comprising: a fuel cell that generates electricity through an electrochemical reaction between hydrogen gas supplied to an anode electrode from a fuel gas supply device and oxidant gas supplied to a cathode electrode from an oxidant gas supply device; a boost converter having a capacitor in an output stage that boosts 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 activated, supplies the hydrogen gas to the anode electrode, and generates an electromotive force based on the activity difference of the hydrogen gas between the anode electrode and the cathode electrode, configuring the fuel cell as a hydrogen concentration cell, and pre-charges the capacitor with power supplied from the fuel cell configured as the hydrogen concentration cell. [Effects of the Invention]

[0009] According to the present disclosure, a better fuel cell system startup method and fuel cell system can be provided. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 is a schematic diagram of a fuel cell vehicle incorporating a fuel cell system according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram of the FCVCU (Fuel Cell Voltage Control Unit). [Figure 3] FIG. 3 is a flowchart illustrating the startup process of the fuel cell system. [Figure 4] FIG. 4 is a flowchart illustrating the precharge process using the hydrogen concentration battery. [Figure 5] FIG. 5 is a schematic configuration diagram of an FCVCU (Fuel Cell Voltage Control Unit) in a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0011] 2. Description of the Related Art Conventionally, fuel cell systems have been proposed that include a fuel cell, a secondary battery, and a boost converter that has a smoothing capacitor in an output stage and boosts the output voltage of the fuel cell and applies it to a load and the secondary battery.

[0012] A conventional fuel cell system includes a main contactor between the smoothing capacitor and the secondary battery, and a precharge circuit connected in parallel to the main contactor. The precharge circuit includes a precharge contactor and a current-limiting resistor connected in series with the contactor. Before starting the fuel cell, this fuel cell system first closes the precharge contactor and charges the smoothing capacitor with the output power of the secondary battery via the current-limiting resistor. After the voltage across the smoothing capacitor rises and there is no longer any risk of welding due to overcurrent, the main contactor is closed and the fuel cell is started. Charging the smoothing capacitor via the precharge circuit before closing the main contactor is called precharging.

[0013] The precharge circuit is used only to precharge the smoothing capacitor. After the fuel cell is started, the precharge circuit is not used 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 a precharge circuit, the precharge circuit (precharge contactor and current limiting resistor) can be removed, minimizing the number of parts in the fuel cell system and reducing costs.

[0015] In the present disclosure, the capacitor can be precharged without using a precharge circuit. The fuel cell system and the method for starting the fuel cell system according to the present disclosure will be described below.

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

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

[0018] [Fuel cell system configuration] The fuel cell vehicle 12 is composed of 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 not be a single unit, but 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.

[0019] The fuel cell system 10 is made up of a fuel cell stack (also simply referred to as a fuel cell, or FC) 18, an oxidizing gas supply device 22, a fuel gas supply device 24, and a coolant supply device .

[0020] The oxidant gas supply device 22 includes a compressor (CP) 28, which is an air compressor, and a humidifier (HUM) 30. The fuel gas supply device 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 coolant supply device 26 includes a coolant 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 DC / DC converter (SUDC) 41 which is a step-up / step-down converter. The power storage unit 43 includes a high-voltage power storage device (high-voltage battery, HV BAT) 44, a DC / DC converter (SDC) 47 which is a step-down converter, and a low-voltage power storage device (low-voltage battery, LV BAT) 48.

[0022] Loads are connected to the voltage conversion unit 42 and the power storage unit 43. The loads include a motor 46 as a main engine, high-voltage auxiliary equipment supplied with power from a high-voltage power storage device 44, and low-voltage auxiliary equipment supplied with power from a low-voltage power 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 the control device 16, various sensors, various solenoid valves, the injector 32, and the like.

[0023] As shown in Fig. 2, the FCVCU 40 has a DC / DC converter (SUC, boost converter) 100, which is a boost converter. The DC / DC converter 100 converts the output voltage Vfc, which is the DC voltage generated by the fuel cell stack 18, into a boost voltage, and applies a high driving voltage to the DC end of the inverter 45, the DC / DC converter 41, and the high-voltage auxiliary machinery described above. Details of the FCVCU 40 will be described later.

[0024] Returning to Fig. 1, DC / DC converter 41 converts the high driving voltage into a battery voltage Vbh of power storage device 44, and charges high-voltage power storage device 44. DC / DC converter 47 converts the battery voltage Vbh into a low-voltage battery voltage Vbl, and charges low-voltage power 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 high DC voltage into three-phase AC to drive the motor 46. The inverter 45 converts the regenerative voltage of the motor 46 into a high DC voltage. This high DC voltage is converted to a low voltage by the DC / DC converter 41 and applied to the high-voltage power storage device 44 to charge the high-voltage power storage device 44. The fuel cell vehicle 12 runs using the driving force generated by the motor 46.

[0027] The fuel cell stack 18 includes a plurality of power generating cells 50. The power generating cells 50 are stacked between an end plate 64 and an end plate 66. Each power generating cell 50 includes a membrane electrode assembly 52 and separators 53 and 54 that sandwich the membrane electrode assembly 52.

[0028] The membrane electrode assembly 52 includes a solid polymer electrolyte membrane 55, which is, for example, 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 each have a gas diffusion layer (not shown) made of carbon paper or the like. The surface of the gas diffusion layer is uniformly coated with porous carbon particles carrying a platinum alloy on its surface, thereby forming an electrode catalyst layer (not shown). The electrode catalyst layer is formed on both sides of the solid polymer electrolyte membrane 55.

[0030] A cathode flow path (oxidant gas flow path) 58 is formed along the cathode electrode 56 on the surface of one separator 53 facing the membrane electrode assembly 52. ​​An anode flow path (fuel gas flow path) 59 is formed along the anode electrode 57 on the surface of the other separator 54 facing the membrane electrode assembly 52.

[0031] Furthermore, the fuel cell stack 18 is provided with a voltage monitoring device (CVM: Cell Voltage Monitor) 96 that detects the voltage of each power generating cell 50 or each of a plurality of power generating cells 50.

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

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

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

[0035] An outlet-side sealing valve 78 is provided in an oxidant off-gas discharge flow path 76 that communicates with the outlet of the cathode flow path 58. The outlet-side sealing valve 78 also functions as a back pressure valve. The opening degree 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 oxidant off-gas discharge flow path 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 flow path 59 via an injector 32 and an ejector 34 provided in a fuel gas supply flow path 80. The outlet of the anode flow path 59 is connected to the gas-liquid separator 36 via a fuel off-gas discharge flow path 82, and the fuel off-gas is supplied to the gas-liquid separator 36.

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

[0038] The refrigerant supply device 26 includes a refrigerant flow path 92 through which a refrigerant (coolant) serving as a heat medium flows, a refrigerant pump 38, and a radiator 39. The refrigerant pump 38 circulates the refrigerant within the refrigerant flow path 92.

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

[0040] The processor of the control device 16 controls the operation of the fuel cell vehicle 12 and the fuel cell system 10 by executing calculations in accordance with the program.

[0041] A 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 a user to start or continue (ON) or end (OFF) the power generation operation of the fuel cell stack 18 of the fuel cell system 10.

[0042] [FCVCU configuration] FIG. 2 is a schematic diagram of the FCVCU 40.

[0043] The FCVCU 40 is a voltage converter equipped with a chopper-type DC / DC converter (SUC) 100. The FCVCU 40 includes an input unit 102 connected to the output terminal of the fuel cell stack 18, an input / output unit 104 connected to the inverter 45, and an output unit 106 connected to high-voltage auxiliary machinery such as the compressor 28. In addition to the inverter 45, the input / output unit 104 is also connected to a high-voltage power storage device 44 via a DC / DC converter 41 and a low-voltage power storage device 48 via a DC / DC converter 47. Note that the DC / DC converter 47 and the power storage device 48 are not shown in FIG. 2.

[0044] The input unit 102 has a positive terminal P1 and a negative terminal N1. The input / output unit 104 has a positive terminal P2 and a negative terminal N2. The output unit 106 has 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, 62.

[0045] A DC / DC converter 100 and a main contactor 108 are provided between the input unit 102 and the input / output unit 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 the heaters 60, 62 via the output unit 106.

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

[0048] The FCVCU 40 is provided 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 voltage between the terminals of a smoothing capacitor 130, which will be described later). The detected current value and voltage value are both output to the control device 16.

[0049] The DC / DC converter 100 can have various configurations, but as is well known, it is basically composed of a reactor (inductor) 124, a switching element 126 such as a MOSFET or an IGBT, a diode 128, and a smoothing capacitor (capacitor) 130. The switching element 126 is subjected to on / off switching control (duty control) by the control device 16 based on the power required by 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, a method for starting the fuel cell system 10 will be described while referring to the flowcharts of FIGS. 3 and 4.

[0053] FIG. 3 is a flowchart used to explain 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 flow path 58 of the fuel cell stack 18 is almost filled with a high concentration of inert gas (nitrogen gas) due to the shutdown power generation process (so-called O2 lean power generation process). In addition to the inert gas (nitrogen gas), a small amount of water molecules may exist in the cathode flow path 58 as water vapor. An appropriate concentration of hydrogen gas remains in the anode flow path 59 of the fuel cell stack 18.

[0055] In step S1, the power switch 94 is turned on by the user (FC startup request), which starts the startup 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, for example, PWM driving under the control of 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).

[0057] When hydrogen gas is supplied to the anode flow channel 59, the hydrogen concentration increases on the anode electrode 57 side. On the other hand, the cathode electrode 56 side is almost filled with a high-concentration 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 side, which has a high hydrogen concentration, and the cathode electrode 56 side, which has a low hydrogen concentration. That is, an electromotive force is generated based on the difference in hydrogen gas activity. The activity of hydrogen gas can be expressed as concentration or partial pressure.

[0059] Therefore, at the anode electrode 57 where the hydrogen concentration is high, the hydrogen molecules (H2) are ionized and converted into protons (H + ) and electrons (e - ) is generated at the anode electrode 57. +The electrons (e - ) travels from the output terminal of the fuel cell stack 18 to the cathode electrode 56 side via the external circuit (FCVCU 40).

[0060] At the cathode electrode 56, protons (H + ) reaches the cathode electrode 56 via an external circuit, and - ) and hydrogen molecules (H2) are generated again. These reactions continue until the hydrogen concentration on the anode electrode 57 side and the hydrogen concentration on the cathode electrode 56 side reach equilibrium.

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

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

[0063] FIG. 4 is a flowchart illustrating the precharge process using the hydrogen concentration battery.

[0064] The precharge process (precharge operation) using the hydrogen concentration cell begins with passive charging in step S31. Passive charging refers to maintaining the switching element 126 of the FCVCU 40 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 via 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 in the compressor 28, refrigerant pump 38, and heaters 60 and 62, respectively, 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 Vfc of the fuel cell stack 18 (the supply voltage as a hydrogen concentration cell).

[0066] In step S32, it is determined whether charging by passive charging has been completed. For example, the control device 16 may compare the terminal voltage V2 of the smoothing capacitor 130 with a predetermined voltage value Vth1 while passive charging is being performed, and determine that charging by passive charging has been completed when 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 drop voltage Vd of the diode 128. If the terminal voltage V2 of the smoothing capacitor 130 is lower 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 inter-terminal voltage V2 of the smoothing capacitor 130. That is, the control device 16 may determine that passive charging is complete when the output current Ifc of the fuel cell stack 18 becomes less than a predetermined current value Ith during passive charging. The predetermined current value Ith is set, for example, to a value that prevents the charging current flowing into the smoothing capacitor 130 from becoming an overcurrent in the next step (step S33). This makes it possible to proceed to the next step (step S33) and start active charging, which will be described later, even before the inter-terminal voltage V2 of the smoothing capacitor 130 reaches the predetermined voltage value Vth1. If the output current Ifc of the fuel cell stack 18 is equal to or greater than the predetermined current value Ith, passive charging continues (step S32: NO).

[0068] When the charging of the smoothing capacitor 130 by passive charging is completed (step S32: YES), the process proceeds to step S33.

[0069] In step S33, the control device 16 starts the voltage step-up operation of the DC / DC converter 100. By controlling the on / off switching of the switching element 126, the DC / DC converter 100 steps up the output voltage Vfc of the fuel cell stack 18. As a result, further charge is stored in the smoothing capacitor 130, and the voltage V2 between the terminals of the smoothing capacitor 130 increases. Charging accompanied by the voltage step-up operation of the DC / DC converter 100 is hereinafter referred to as active charging.

[0070] In active charging, the control device 16 can 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 becomes a maximum (maximum power point tracking control, MPPT (Maximum Power Point Tracking) control).

[0071] Active charging continues until the inter-terminal voltage V2 of the smoothing capacitor 130 reaches a 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 power storage device 44 or a value related to the battery voltage Vbh. When the smoothing capacitor 130 has been 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 ends the pre-charging process using the hydrogen concentration battery.

[0072] The hydrogen concentration cell has the characteristic that the concentration difference is reduced by the transport of hydrogen from the anode to the cathode, and the electromotive force is reduced. For this reason, it is desirable to complete the above precharge operation (steps S31 to S35) in as short a time as possible so that the hydrogen partial pressure to which the cathode is exposed can be kept low.

[0073] Returning to the flowchart shown in FIG. 3, in step S4, the control device 16 turns on the main contactor 108. At this time, a sufficient charge is stored in the smoothing capacitor 130. 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-side seal valve 74 and the outlet-side seal valve 78 are opened to supply the oxidant gas to the cathode flow path 58. This allows the hydrogen gas (H gas) generated on the cathode electrode 56 side to be scavenged and discharged from the exhaust gas exhaust port 90. The inlet-side seal valve 74 and the outlet-side seal valve 78 may be opened in advance before the compressor 28 is started.

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

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

[0077] [Comparative Example] FIG. 5 is a schematic configuration diagram of the FCVCU 140 in the comparative example.

[0078] The FCVCU 140 in the comparative example is provided with a precharge circuit 134. In the comparative example, the components other than the precharge circuit 134 are common to the components of the FCVCU 40 shown in Figure 2, and therefore are assigned the same reference numerals as the components of the FCVCU 40.

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

[0080] That is, when the fuel cell 18 is started up, first the pre-charge contactor 136 is turned on (closed) while the main contactor 108 is in the off state. The battery voltage Vbh of the power storage device 44 is applied to the smoothing capacitor 130 via the current limiting resistor 138, and the smoothing capacitor 130 is pre-charged with power supplied from the power storage device 44 via the current limiting resistor 138 and the pre-charge contactor 136. After the voltage V2 between the terminals of the smoothing capacitor 130 rises and there is no longer any risk of overcurrent, the main contactor 108 is turned on (closed), and the fuel cell 18 is started up.

[0081] As such, the precharge circuit 134 in the comparative example is a component that is used only when the fuel cell system 10 is started up, and is a device that is not utilized during the majority of the actual use time of the fuel cell system 10, and therefore requires simplification.

[0082] In contrast, the startup method of the fuel cell system 10 according to this embodiment includes step S2 of 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 of precharging the smoothing capacitor 130 with the power Pfc supplied from the fuel cell 18 configured as a hydrogen concentration cell.

[0083] In addition, the fuel cell system 10 according to this embodiment is equipped with a control device 16, which drives the fuel gas supply device 24 when the fuel cell 18 is not activated, supplies hydrogen gas to the anode electrode 57, and generates 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 pre-charges 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 precharged without using the precharge circuit 134 (the precharge contactor 136 and the current limiting resistor 138). As a result, there is no need to provide the precharge circuit 134 for the main contactor 108. The precharge circuit 134 can be removed from the FCVCU 140, minimizing the number of parts in the fuel cell system 10 and reducing costs.

[0085] The following additional notes are further disclosed regarding the above-described embodiment.

[0086] (Appendix 1) A start-up method for a fuel cell system (10) according to the present disclosure includes a fuel cell (18) that generates electricity by an electrochemical reaction between hydrogen gas supplied to an anode electrode (57) from a fuel gas supply device (24) and an oxidant gas supplied to a cathode electrode (56) from an oxidant gas supply device (22), and a boost converter (100) having a capacitor (130) in an output stage and that boosts an output voltage (Vfc) of the fuel cell, the start-up method comprising the steps of: 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 pre-charging the capacitor with power (Pfc) supplied from the fuel cell configured as the hydrogen concentration cell.

[0087] This method allows the capacitor to be precharged without using a precharge circuit, thereby minimizing the number of components in the fuel cell system and reducing costs, and providing a better method for starting up the fuel cell system.

[0088] (Appendix 2) In the method for starting a fuel cell system described in Appendix 1, it is preferable that the step of precharging the capacitor includes a step (S31) of electrically connecting the fuel cell and the capacitor and applying the output voltage of the fuel cell configured as the hydrogen concentration cell to the capacitor to charge the capacitor, and a step (S32) of driving the boost converter to boost the output voltage of the fuel cell after the capacitor has been charged by the output voltage of the fuel cell and applying the boosted voltage to the capacitor to charge the capacitor.

[0089] This method allows the capacitor to be precharged quickly.

[0090] (Appendix 3) A method for starting a fuel cell system according to claim 1 or 2, wherein the fuel cell system further comprises: an electric storage device (44); a contactor (108) provided between the electric storage device and the capacitor; and a contactor (108) connected in parallel with the capacitor on the primary side of the contactor. Compressor (28) included the oxidant gas supply device, and a step (S34) of determining that precharging of the capacitor is completed when the capacitor is charged to a predetermined voltage value (Vth2), and when it is determined that precharging of the capacitor is completed, closing the contactor to discharge the oxidant gas from the power storage device. Compressor Power is supplied to the Compressor and (S5) driving the oxidant gas supply device to supply the oxidant gas to the cathode electrode.

[0091] According to this method, the hydrogen gas produced at the cathode electrode can be purged to the outside of the fuel cell stack.

[0092] (Appendix 4) A method for starting a fuel cell system according to claim 1 or 2, wherein the fuel cell system further comprises: an electric storage device (44); a contactor (108) provided between the electric storage device and the capacitor; and auxiliary devices (28, 38, 60, 62 ), and preferably further comprising the steps of: a step (S34) of determining that precharging of the capacitor is complete when the capacitor is charged to a predetermined voltage value (Vth2); a step (S5) of closing the contactor to supply power from the power storage device to the auxiliary machinery when it is determined that precharging of the capacitor is complete; and a step (S6) of driving the auxiliary machinery based on the supplied power, supplying the hydrogen gas to the anode electrode and the oxidant gas to the cathode electrode, and causing the fuel cell to generate power by an electrochemical reaction between the hydrogen gas and the oxidant gas.

[0093] According to this method, the capacitor can be precharged without using a precharge circuit, and the fuel cell can be started.

[0094] (Appendix 5) The fuel cell system according to the present disclosure comprises a fuel cell (18) that generates electricity through an electrochemical reaction between hydrogen gas supplied from a fuel gas supply device (24) to an anode electrode (57) and an oxidant gas supplied from an oxidant gas supply device (22) to a cathode electrode (56), a boost converter (100) having a capacitor (130) in an output stage and that boosts an 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 activated, supplies the hydrogen gas to the anode electrode, and generates 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 pre-charges the capacitor with power (Pfc) supplied from the fuel cell configured as the hydrogen concentration cell.

[0095] With this configuration, the capacitor can be precharged without using a precharge circuit, which minimizes the number of components in the fuel cell system and reduces costs, making it possible to provide a better fuel cell system.

[0096] Although the present disclosure has been described in detail above, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments. [Explanation of symbols]

[0097] 10...Fuel cell system 16...Control device 18... fuel cell stack (fuel cell) 22... oxidant 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 an anode electrode from a fuel gas supply device and oxidant gas supplied to a cathode electrode from an oxidant gas supply device; a boost converter having a capacitor at an output stage for boosting the output voltage of the fuel cell; A method for starting a fuel cell system comprising: supplying the hydrogen gas to the anode electrode while the fuel cell is not activated, and 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; precharging the capacitor with power supplied from the fuel cell configured as the hydrogen concentration cell; A method for starting a fuel cell system, comprising:

2. 2. A method for starting a fuel cell system according to claim 1, comprising: The step of precharging the capacitor comprises: a step of electrically connecting the fuel cell and the capacitor and applying the output voltage of the fuel cell configured as the hydrogen concentration cell to the capacitor to charge the capacitor; After the capacitor is charged by the output voltage of the fuel cell, driving the boost converter to boost the output voltage of the fuel cell, and applying the boosted voltage to the capacitor to charge the capacitor; A method for starting a fuel cell system, comprising:

3. 3. A method for starting a fuel cell system according to claim 1 or 2, comprising: The fuel cell system further comprises: a power storage device; a contactor provided between the power storage device and the capacitor; the oxidant gas supply device including a compressor connected in parallel with the capacitor on the primary side of the contactor; and determining that precharging of the capacitor is complete when the capacitor is charged to a predetermined voltage value; when it is determined that the precharging of the capacitor is completed, closing the contactor to supply power from the power storage device to the compressor to drive the compressor, and supplying the oxidant gas from the oxidant gas supply device to the cathode electrode; A method for starting a fuel cell system, comprising:

4. 3. A method for starting a fuel cell system according to claim 1 or 2, comprising: The fuel cell system further comprises: a power storage device; a contactor provided between the power storage device and the capacitor; Auxiliary devices connected in parallel with the capacitor on the primary side of the contactor; and determining that precharging of the capacitor is complete when the capacitor is charged to a predetermined voltage value; when it is determined that the precharging of the capacitor is completed, closing the contactor to supply power from the power storage device to the auxiliary machinery; driving the auxiliary machinery based on the supplied electric power, supplying the hydrogen gas to the anode electrode and the oxidant gas to the cathode electrode, and causing the fuel cell to generate electricity through an electrochemical reaction between the hydrogen gas and the oxidant gas; A method for starting a fuel cell system, comprising:

5. a fuel cell that generates electricity through an electrochemical reaction between hydrogen gas supplied to an anode electrode from a fuel gas supply device and oxidant gas supplied to a cathode electrode from an oxidant gas supply device; a boost converter having a capacitor at an output stage for boosting the output voltage of the fuel cell; a control device that controls the fuel gas supply device, the oxidant gas supply device, the fuel cell, and the boost converter; A fuel cell system comprising: The control device The fuel gas supply device is driven while the fuel cell is not activated, and the hydrogen gas is supplied to the anode electrode; an electromotive force is generated 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; precharging the capacitor with power supplied from the fuel cell configured as the hydrogen concentration cell; Fuel cell system.

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