System and method for operating a fuel cell system

Abstract

The present application relates to a system and method for operating a fuel cell system, in particular a system and method for controlling operation of a fuel cell system, the fuel cell system comprising a fuel cell unit comprising a fuel cell stack comprising: a cathode and an anode; a cathode recirculation channel configured to divert a cathode exhaust stream to the cathode inlet line when a reduction of oxygen partial pressure in an air stream fed to the cathode via the cathode inlet line is required; and an inert gas generation system configured to generate an inert gas to be supplied to the cathode inlet line when a further reduction of the oxygen partial pressure in the air flow is required. When the fuel cell system is or is expected to operate at a reduced power demand, a value of a power output requested from the fuel cell system is compared to at least one threshold power level to determine whether to transfer a cathode exhaust flow and / or inert gas to the cathode inlet line.

Description

Technical Field

[0001] The present disclosure generally relates to operating a fuel cell system when a requested power output from the fuel cell system is reduced. The present disclosure relates to a fuel cell system, a control system for a fuel cell system, a fuel cell vehicle, and a method implemented therein for controlling the fuel cell system to operate in a low power mode.

[0002] The present disclosure may be applicable to heavy vehicles such as trucks, buses, and construction equipment, as well as generator sets. Background Art

[0003] A fuel cell is an electrochemical device that includes an electrolyte sandwiched between two electrodes such as an anode and a cathode. A solid polymer electrolyte fuel cell employing a proton exchange membrane (PEM) generates electric power or electrical energy via an electrochemical reaction between a fuel such as hydrogen received at the anode or anode side and an oxidant such as oxygen or air received at the cathode or cathode side. PEM fuel cells are considered well-suited for vehicle applications as well as stationary applications employing fuel cell systems. Two or more fuel cells are typically arranged together as a fuel cell stack to provide a higher output voltage. One or more fuel cell stacks may form a fuel cell unit, and a fuel cell system may include one or more fuel cell units.

[0004] In a fuel cell, metals such as palladium and platinum are used as catalysts to facilitate the electrochemical reaction between hydrogen and air or oxygen, where the reaction occurs on the membrane or electrolyte. A support structure made of a catalyst carrier material such as carbon is configured to support a membrane that may be coated with a metal-based catalyst on both sides. The condition of the catalyst and the carrier material defines the durability, life, and performance of the fuel cell system. The catalyst needs to operate within specific conditions to produce an effective reaction rate. Thus, an excessive increase in the single cell voltage may cause degradation of the catalyst and the carrier material, where the single cell voltage may be defined as the cell voltage of each fuel cell in each fuel cell stack in a fuel cell unit of a fuel cell system, where all fuel cells are considered to act as a single cell. Thus, during operation of the fuel cell system, it is necessary to maintain the single cell voltage (also referred to as the single cell potential) below a certain voltage level.

[0005] In high-power fuel cell systems that are increasingly receiving attention in the automotive and other fields, the fuel cell system has problems at low loads. Specifically, at a higher power level of the fuel cell system, the single cell potential can reach a safety threshold. Thus, as the power of the fuel cell system decreases, the single cell potential may increase to a value that has a negative impact on the condition of the catalyst and the carbon carrier material. Thus, it may be challenging to control the fuel cell system in a manner that takes into account the potential degradation of the catalyst and the carrier material at lower loads.

[0006] During vehicle idling, the excess power generated by the fuel cell system can be utilized to charge the vehicle's battery. However, in cases where the battery is, for example, fully charged and cannot accept the power surplus, it may be necessary to decide whether to dissipate the excess power generated by the fuel cell system for heating or whether to shut down the fuel cell system. However, releasing the power as heat into, for example, the surrounding environment is wasteful; and each fuel cell system shutdown event causes the fuel cell system to deteriorate faster.

[0007] Various methods have been proposed to reduce the single cell potential with a reduced power demand of the fuel cell system. However, there is still a need for improved methods to control the operation of the fuel cell system with a reduced power demand of the fuel cell system. SUMMARY OF THE INVENTION

[0008] Aspects of the present disclosure relate to controlling a fuel cell system at low load in a manner that limits the single cell voltage or potential to a value below 0.8 V when the power demand of the fuel cell system is reduced. This allows avoiding deterioration of the catalyst and the carrier material. The fuel cell system can be deployed in a fuel cell vehicle or in a stationary application.

[0009] According to aspects of the present disclosure, the efficiency of the fuel cell system is intentionally reduced to decrease the power output of the fuel cell system during vehicle idling or other low - power events. In this way, the single cell voltage is reduced, thereby reducing the risk of deterioration of the catalyst and the carrier material. In an example according to the present disclosure, the cathode exhaust stream generated by the cathode is diverted or recycled back to the cathode inlet or input pipeline. Additionally, an inert gas generation system that may be associated with the fuel cell system can be used to generate a controlled amount of inert gas that can be supplied to the cathode inlet pipeline. In this way, the oxygen partial pressure in the air stream supplied to the cathode will be reduced, thereby reducing the single cell potential.

[0010] In one aspect, a fuel cell system for a vehicle is provided. The fuel cell system includes at least one fuel cell unit, the at least one fuel cell unit including a fuel cell stack, the fuel cell stack including a cathode side, an anode side, an inert gas generation system, and a control system. The cathode side is configured to receive an air stream via a cathode inlet line and is configured to provide a cathode exhaust stream via a cathode outlet line, the cathode outlet line being fluidly coupled to a cathode recirculation passage that is configured to divert a portion of the cathode exhaust stream to the cathode inlet line. The inert gas generation system is configured to generate an inert gas that is supplied to the cathode inlet line. The anode side is configured to receive a hydrogen stream via an anode feed line that is configured to be in fluid communication with an anode inlet line and an anode bypass line, the anode inlet line being configured to supply the hydrogen stream to the anode side, the anode bypass line being configured to divert a portion of the hydrogen stream to the inert gas generation system. The control system includes processing circuitry that is configured to: determine that the fuel cell system has or will operate at a reduced power demand of the fuel cell system for a period longer than a threshold period; in response to determining that the fuel cell system has or will operate at the reduced power demand, compare a value of a power output requested from the fuel cell system with at least one threshold power level; in response to determining that the value of the power output is lower than at least one threshold power level including a first threshold power level and higher than at least one threshold power level including a second threshold power level, control the cathode recirculation passage to divert a portion of the cathode exhaust stream into the cathode inlet line; and in response to determining that the value of the power output is lower than the second threshold power level, control a cathode bypass loop fluidly coupled to the cathode recirculation passage to divert a portion of the cathode exhaust stream to the inert gas generation system or control an air stream bypass line fluidly coupled to the cathode inlet line to divert a portion of the air stream to the inert gas generation system, and control the anode bypass path to divert a portion of the hydrogen stream to the inert gas generation system, thereby causing the inert gas generation system to generate a controlled amount of inert gas.

[0011] Technical advantages include controlling a fuel cell system in a manner that allows the power demand or load of the fuel cell system to be reduced as needed while avoiding the risk of the single cell potential increasing above a 0.8 V safety threshold. By reducing the oxygen partial pressure in the cathode inlet stream (such as the air stream) in a controlled manner, the efficiency of the fuel cell system is intentionally reduced. To reduce the oxygen partial pressure, in addition to an inert gas generation system including a catalyst that can generate an inert gas (such as, for example, water vapor), reactants already present in the fuel cell system are also used. The reduction in the efficiency of the fuel cell system means that its output power may be reduced to a lower value, while the single cell voltage of the fuel cell stack does not increase above 0.8 V. Thus, the system of the present disclosure provides improved control of the fuel cell system at low power demand in a manner that avoids degradation of the catalyst and support materials of the fuel cell stack of the fuel cell system.

[0012] In some examples, when the vehicle is in an idle mode, it can be determined that the fuel cell system is operating or will operate with a reduced power demand.

[0013] In some examples, the processing circuitry of the control system can be configured to: in response to determining that the value of the power output is below the second threshold power level, control the cathode bypass channel to divert a portion of the cathode exhaust stream to the inert gas generation system, and control the anode bypass path to divert a portion of the hydrogen stream to the inert gas generation system, such that the inert gas generation system generates the controlled amount of inert gas based on the value of the power output.

[0014] In some examples, the processing circuitry of the control system can also be configured to control the cathode recirculation channel to divert a portion of the cathode exhaust stream into the cathode inlet line.

[0015] In some examples, the processing circuitry of the control system can be configured to: in response to determining that the value of the power output is below the second threshold power level, control the air stream bypass line to divert a portion of the air stream to the inert gas generation system, and control the anode bypass path to divert a portion of the hydrogen stream to the inert gas generation system, such that the inert gas generation system generates the controlled amount of inert gas based on the value of the power output.

[0016] In some examples, the determination that the fuel cell system is operating or will operate with the reduced power demand for a period longer than the threshold period is performed based on one or more characteristics of the route on which the vehicle is traveling.

[0017] In some examples, when the fuel cell system is no longer operating with the reduced power demand and / or when an increased amount of power is requested from the fuel cell system, the fuel cell system can be controlled to increase the oxygen partial pressure in the cathode inlet line.

[0018] Thus, in some examples, the processing circuitry of the control system can be configured to determine that the fuel cell system is no longer operating at the reduced power demand and that the value of the power output requested from the fuel cell system is greater than the at least one threshold power. The processing circuitry of the control system can also be configured to: in response to determining that the value of the power output is greater than the at least one threshold power, control the inert gas generation system to supply the reduced amount of inert gas to the cathode inlet line, control the cathode bypass line to divert the reduced amount of cathode exhaust flow to the inert gas generation system or control the air flow bypass line to divert the reduced amount of air flow to the inert gas generation system, and control the anode bypass path to divert the reduced amount of hydrogen flow to the inert gas generation system; and as the value of the power output further decreases and as the inert gas generation system stops supplying the inert gas to the cathode inlet line, control the cathode bypass line to stop diverting the cathode exhaust flow to the catalyst system and control the anode bypass path to stop diverting the hydrogen flow to the inert gas generation system.

[0019] In some examples, the processing circuitry can also be configured to control the cathode recirculation passage to gradually stop diverting the cathode exhaust flow into the cathode inlet line.

[0020] In some examples, a fuel cell vehicle is provided that includes a fuel cell system according to an example of the present disclosure.

[0021] In one aspect, a method for operating a fuel cell system of a vehicle is provided. The fuel cell system includes at least one fuel cell unit, and the at least one fuel cell unit includes a fuel cell stack. The fuel cell stack includes: a cathode side configured to receive an air stream and provide a cathode exhaust stream; and an anode side configured to receive a hydrogen stream. The method includes: determining that the fuel cell system has or will operate at a reduced power demand of the fuel cell system for a period longer than a threshold period; in response to determining that the fuel cell system has or will operate at a reduced power demand, comparing a value of a power output requested from the fuel cell system with at least one threshold power level; in response to determining that the value of the power output is lower than at least one threshold power level including a first threshold power level and higher than at least one threshold power level including a second threshold power level, reducing an oxygen partial pressure of the air stream in a cathode inlet line by diverting a portion of the cathode exhaust stream to the cathode inlet line, the cathode inlet line being configured to supply the air stream to the cathode; and in response to determining that the value of the power output is lower than the second threshold power level, reducing the oxygen partial pressure of the air stream in the cathode inlet line by controlling an inert gas generation system of the fuel cell system to generate an inert gas to be supplied to the cathode inlet line thereby further reducing the oxygen partial pressure of the air stream in the cathode inlet line.

[0022] In some examples, controlling the inert gas generation system to generate the inert gas includes diverting a portion of the cathode exhaust stream to the inert gas generation system and diverting a portion of hydrogen to the inert gas generation system.

[0023] In some examples, the method may include: in response to determining that the value of the power output is lower than the second threshold power level, diverting a portion of the cathode exhaust stream to the cathode inlet line.

[0024] In some examples, controlling the inert gas generation system to generate the inert gas includes diverting a portion of the air stream to the inert gas generation system and diverting a portion of hydrogen to the catalyst system.

[0025] In some examples, the method may include: determining that the fuel cell system is no longer operating at the reduced power demand and that the value of the power output requested from the fuel cell system is greater than the at least one threshold power; in response to determining that the value of the power output is greater than the at least one threshold power, controlling the inert gas generation system to supply the reduced amount of inert gas to the cathode inlet line, controlling the cathode bypass line to divert the reduced amount of cathode exhaust flow to the inert gas generation system or controlling the air flow bypass line to divert the reduced amount of air flow to the inert gas generation system, and controlling the anode bypass path to divert the reduced amount of hydrogen flow to the inert gas generation system; and as the value of the power output further decreases and as the inert gas generation system stops supplying the inert gas to the cathode inlet line, controlling (608) the cathode bypass line to stop diverting the cathode exhaust flow to the catalyst system and controlling the anode bypass path to stop diverting the hydrogen flow to the inert gas generation system.

[0026] The technical advantages of the method include advantages similar to those associated with the fuel cell system described above. Thus, the method of the present disclosure provides improved control of a fuel cell system at low power demand in a manner that avoids degrading the catalyst and carrier materials of the fuel cell stack of the fuel cell system.

[0027] Lower values of power output require lower oxygen partial pressures of the air flow.

[0028] In one aspect, a control system for controlling a fuel cell system of a fuel cell vehicle is provided. The control system includes a processing circuit configured to perform the method according to an example of the present disclosure.

[0029] In one aspect, a fuel cell vehicle is provided that includes the control system according to an example of the present disclosure and / or communicates with the control system.

[0030] In one aspect, a computer program product is provided that includes computer-executable instructions that, when executed by a processing circuit, cause the processing circuit to perform the method according to any aspect and example of the present disclosure. The processing circuit may be, for example, the processing circuit of the control system.

[0031] In one aspect, a computer-readable storage medium is provided that stores a computer program product that includes computer-executable instructions that, when executed by a processing circuit, cause the processing circuit to perform the method according to any aspect and example of the present disclosure. The processing circuit may be, for example, the processing circuit of the control system.

[0032] Additional features and advantages are disclosed in the following description, claims, and drawings. Additionally, those skilled in the art will appreciate additional advantages either clearly or by practicing the disclosure as described herein. Also disclosed herein are a control unit, a computer program product, and a computer-readable medium associated with the technical effects and corresponding advantages discussed above. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Aspects of the present disclosure, which are cited as examples, will be described in more detail below with reference to the drawings.

[0034] Figure 1 A side view of an example of a vehicle including a fuel cell system is shown, in which a method according to an example of the present disclosure can be implemented.

[0035] Figure 2A A block diagram showing a fuel cell system and a control system is shown, in which a method according to an example of the present disclosure can be implemented.

[0036] Figure 2B A block diagram showing a fuel cell system and a control system is shown, in which a method according to an example of the present disclosure can be implemented.

[0037] Figure 3 Shows Figure 2A An example block diagram of a fuel cell system.

[0038] Figure 4 Shows Figure 2A Another example block diagram of a fuel cell system.

[0039] Figure 5 A flowchart showing a method for controlling a fuel cell system according to an example.

[0040] Figure 6 A flowchart showing a method for controlling a fuel cell system according to an example.

[0041] Figure 7A And Figure 7B A schematic block diagram showing an example of a control system for a fuel cell system according to an example. DETAILED DESCRIPTION

[0042] In a fuel cell system, at low loads, the single cell voltage can reach a safety threshold at a power level higher than the desired value. For example, in some cases, it has reached 50 kW. For instance, in some cases, once the fuel cell system enters the idle mode or a low load (i.e., low current density) state, the single cell voltage may quickly reach the safety threshold. For example, when a vehicle including the fuel cell system is in the idle mode, the fuel cell system can be in the idle mode. Thus, although it may be necessary to further reduce the power generated by the fuel cell, this task may become challenging due to the increase in the single cell voltage. This makes it challenging to operate the fuel cell system correctly at low loads without damaging the catalyst and carrier materials of the fuel cell stack.

[0043] Therefore, in order to control catalyst degradation and thereby control the fuel cell system life, it is necessary to limit the maximum value that the single cell voltage can reach at low current density. When the single cell voltage (which can also be interchangeably referred to as the single cell potential) increases to a value of 0.8 V or higher than 0.8 V, platinum begins to dissolve, thereby reducing the electrochemically active surface area (ECSA), which in turn leads to a decrease in the efficiency and a shortening of the life of the fuel cell system. Thus, if the maximum value that the single cell voltage is allowed to reach is set to 0.8 V or slightly lower than 0.8 V (e.g., 0.79 V), the risk of catalyst and carrier material degradation can be reduced or avoided.

[0044] Solutions that have been used involve stop / start strategies such that the fuel cell system can be shut down when the single cell voltage reaches 0.8 V. For example, when the power required by the fuel cell system drops below a certain value (e.g., 50 kW in some scenarios), the fuel cell system may shut down. The drawback of such methods is that the frequent start and stop of the fuel cell system can trigger other degradation mechanisms, such as carbon corrosion in the catalyst carrier material. This leads to a reduction in platinum, which in turn leads to a decrease in ECSA, which causes the catalyst structure to collapse and thus increases mass transport losses. Therefore, the stop / start strategy may have a negative impact on the efficiency and life of the fuel cell system.

[0045] The methods and systems of the present disclosure employ a control strategy that involves using a cathode recirculation loop or passage that recirculates a cathode exhaust stream back into a cathode inlet line configured to transfer an air stream to the cathode in order to reduce the oxygen partial pressure in the air stream fed into the cathode inlet line. In addition to the cathode exhaust stream provided to the cathode inlet line, the control strategy can also involve generating an inert gas that can be fed into the inlet of the cathode. Depending on the configuration of the fuel cell system, the inert gas is generated by an inert gas generation system that is configured to use a portion of the cathode exhaust stream transferred to the inert gas generation system or use a portion of an air stream obtained from, for example, the surrounding environment to generate the inert gas. The inert gas generation system is configured to also receive a portion of the hydrogen stream transferred from the hydrogen stream fed to the anode. Dilution of the air stream in the cathode inlet line by the inert gas results in a further reduction in the oxygen partial pressure in the air stream.

[0046] In response to determining that the vehicle has or will operate at a reduced power demand and based on the power level requested from the fuel cell system at the reduced power demand, the supply of the cathode exhaust stream to the cathode inlet line is performed and, in some cases, additionally generating an inert gas that is also supplied to the cathode inlet line. As the requested power is reduced, a greater amount of the inert gas may be required to further reduce the oxygen partial pressure in the air stream fed into the cathode inlet line. In this way, the fuel cell system intentionally reduces efficiency, which, however, advantageously allows for improved operation of the fuel cell system at low loads in such a way that the single cell potential does not increase to above a safety threshold (i.e., 0.8 V). Another advantage is that, since the efficiency of the fuel cell system is reduced, the excess power generated by the fuel cell system is reduced. Thus, even if the energy storage system (ESS) of the fuel cell system cannot accept the excess power generated by the fuel cell system at low loads, less or no power is wasted in the form of heat. In addition, shutdown of the fuel cell system can be avoided, which increases the durability and lifespan of the fuel cell system. Accordingly, the systems and methods of the present disclosure advantageously provide improved control of the fuel cell system at low power demands.

[0047] Figure 1 A side view of a vehicle 10 according to an example of the present disclosure is depicted. The vehicle 10 is shown as a truck, such as a heavy-duty truck for towing one or more trailers (not shown). The vehicle 10 can be a fuel cell electric vehicle (FCEV) or a hybrid vehicle. It should be understood that the present disclosure is not limited to any other particular type of vehicle, but can be used for any other type of vehicle, such as a bus, construction equipment, e.g., a wheel loader or an excavator, a passenger vehicle, an aircraft, and a marine vessel. The present disclosure also applies to other applications unrelated to vehicles, including stationary applications.

[0048] AsFigure 1 As schematically shown in FIG. Figure 1 , the vehicle 10 includes a fuel cell system 20, which includes a fuel cell unit 21, and the fuel cell unit includes one or more fuel cell stacks 22. The fuel cell system 20 can be used to power one or more electric drive motors (not shown) that generate propulsion force for the vehicle 10. The fuel cell system 20 can additionally or alternatively be used to power other power-consuming devices of the vehicle 10 (not shown) (such as an electric motor for a crane, an electric motor for a refrigerator system, an electric motor for an air conditioning system, or any other power-consuming function of the vehicle 10). Thus, the fuel cell system 20 can additionally or alternatively be used to power a power take-off (PTO) device, which is a device that transfers the power of an electric motor to another piece of equipment. The vehicle 10 can include or be coupled to or associated with one or more PTO devices.

[0049] The fuel cell unit 21 of the fuel cell system 20 includes one or more fuel cell stacks 22, and each fuel cell stack includes one or more fuel cells. In the examples herein, the fuel cell unit 21 can include a plurality of fuel cell stacks 22, and any reference to a fuel cell stack 22 applies to two or more fuel cell stacks. The fuel cell system and / or the fuel cell unit 21 are arranged to supply the required hydrogen fuel (H2), an oxidant (such as air), cooling, heating, etc. to the fuel cells. The fuel cell system 20 can include Figure 1 various of its components not shown in FIG. Figure 1 . In some examples, the fuel cell system 20 can include more than one fuel cell unit 21, and each fuel cell unit can include its own controller system, which can be communicatively connected to a controller or control system configured to control the fuel cell system 20.

[0050] The fuel cell system 20 can include a single fuel cell system, two fuel cell systems, or more than two fuel cell systems, such as three or more fuel cell systems. Additionally, when several fuel cell units or systems are provided, the fuel cell systems can be controlled independently or jointly. When controllable independently, each fuel cell system can be controlled to an on state or an off state regardless of the state of other fuel cell systems. When two or more of the fuel cell systems can be controlled jointly, these fuel cell systems can be jointly controlled to an on state or an off state, i.e., all fuel cell systems are jointly controlled to the same state. In some cases, two fuel cell systems can be controlled dependently on each other such that one of the fuel cell systems is controlled to an on state or an off state according to the state of the other fuel cell system.

[0051] According to an example of the present disclosure, the vehicle 10 further includes a control device or control system 30. The control system 30 can be used to control the fuel cell system 20. The control system 30 can be a part of the fuel cell system 20 or the control system 30 can be separated from the fuel cell system 20. In some implementations, the control system 30 can be a part of the main vehicle controller (not shown). In some examples, the control system 30 can be a combination of one or more on-vehicle control systems or off-vehicle control systems. The control system 30 can be configured to control the fuel cell system 20 by sending control signals and by receiving status information related to the fuel cell system 20, for example, one or more fuel cell units 21. The control system 30 can be configured to receive information from various sensors, which sensors include temperature sensors, humidity sensors, voltage sensors, and one or more of other sensors included in the fuel cell system 20 and / or the vehicle 10 or associated with the fuel cell system and / or the vehicle. For example, one or more voltage sensors can be included in the fuel cell unit 21 to monitor the voltage of the fuel cell stack. Various other sensors can obtain measurements regarding the operation of the components of the fuel cell system 20.

[0052] The control system 30 can be communicatively coupled to an internal database, an external database, or a combination thereof to receive data related to, for example, the route the vehicle has traveled or will travel. The data related to the route can include a starting point, an ending point, and the path the vehicle 10 travels between the starting point and the ending point. The control system 30 can store and / or have access to data related to the route, which data includes terrain information, speed limits, obstacles, etc. The control system 30 can also receive real-time or near real-time information about the route, which information includes traffic congestion, accident reports, road closures, construction, etc. The control system 30 can also store and / or have access to historical data related to the driver's driving pattern, historical data regarding vehicle operation (e.g., locations the vehicle has traveled, frequency and locations of stops), historical data regarding environmental conditions at the locations the vehicle has traveled, etc. The control system 30 can also receive data from a weather service, which data can include data regarding predicted weather conditions and other types of data. The control system 30 can have data regarding the vehicle's current location and the locations the vehicle is expected to travel along the route.

[0053] The control system 30 is an electronic control unit and can include processing circuitry adapted to execute a computer program, such as computer-executable instructions, to perform the methods according to aspects of the present disclosure. The control system 30 can include hardware and / or software for performing the methods according to aspects of the present disclosure. The control system 30 can be represented as a computer. The control system 30 can be composed of one or more separate sub-units, and the control system 30 can communicate by using wired and / or wireless communication technologies.

[0054] AsFigure 1 As shown, vehicle 10 includes an electrical energy storage system (ESS) 23, such as one or more batteries and / or one or more supercapacitors, which are used to store electrical energy, including excess electrical energy generated by fuel cell system 20. ESS 23 can store energy regenerated during braking (such as regenerative braking), and / or it can be configured to be charged by a charger (such as from an external power grid). ESS 23 is configured to assist fuel cell system 20 in supplying energy to the drive motor to meet the power / energy requirements of vehicle 10. ESS 23 can be configured to provide additional power in cases where fuel cell system 20 cannot provide all of the required power or fuel cell system 20 is not suitable for providing all of the required power. In various examples, ESS 23 can provide electrical energy storage for the electrical energy generated by the fuel cell system at low loads, assist fuel cell system 20 in generating electricity at higher loads, or can act as the primary energy supplier in some cases. Fuel cell system 20 and ESS 23 can supply power to one or more auxiliary systems of vehicle 10.

[0055] Vehicle 10 may also include Figure 1 various other components not shown.

[0056] Although the present disclosure is described with respect to a vehicle (such as a truck), aspects of the present disclosure are not limited to such a particular vehicle, but can also be used in other vehicles, such as passenger vehicles, off-road vehicles, aircraft, and marine vessels. The present disclosure can also be applied to ships and stationary applications, such as grid-connected auxiliary generators or generators independent of the grid.

[0057] Figure 2A and Figure 2B shows an example of a fuel cell system that can be deployed in a fuel cell vehicle (e.g., Figure 1 vehicle 10 in ). Figure 2A shows a fuel cell system in which an inert gas generation system is fed a hydrogen stream and a cathode exhaust stream that are transported or transferred to the inert gas generation system. Discussed below Figure 2B shows a fuel cell system in which an inert gas generation system is fed a hydrogen stream and an air stream.

[0058] Figure 2A shows an example of a fuel cell system 20a that can be deployed in a fuel cell vehicle, which can be, for example, Figure 1Vehicle 10. The fuel cell system 20a may be configured to perform the method according to an example of the present disclosure. Specifically, the fuel cell system 20a may be configured to operate such that the oxygen partial pressure in the air stream supplied to the cathode is controlled based on the power requested from the fuel cell system 20a (e.g., when the power demand of the fuel cell system 20a decreases). In the fuel cell system 20a, the cathode outlet line is fluidly coupled to a cathode recirculation passage configured to divert a portion of the cathode exhaust stream to the cathode inlet line. The fuel cell system 20a further includes a cathode bypass loop that is in fluid communication with the cathode recirculation passage and is configured to divert a portion of the cathode exhaust stream to an inert gas generation system.

[0059] As Figure 2A shown, the fuel cell system 20a includes a fuel cell unit 21a that includes a fuel cell stack 22a. The fuel cell unit 21a may include more than one fuel cell stack. The operation of the fuel cell system 20a may be controlled by a control system 30, also as Figure 1 shown.

[0060] The fuel cell stack 22a includes an anode side or anode 24, a cathode side or cathode 26, and an electrolyte (not shown), such as, for example, a proton exchange membrane (PEM) sandwiched between the anode 24 and the cathode 26. The fuel cell stack 22a is configured to generate power through an electrochemical reaction between hydrogen and an oxidant, such as air or oxygen.

[0061] The anode or anode side 24 is configured to receive a hydrogen gas stream via an anode feed line 28. The hydrogen gas stream can be supplied from, for example, a hydrogen storage device (not shown) or from any suitable hydrogen gas source. An anode outlet line 29 can be configured to receive by-products of the operation of the anode side 24 and divert them away from the anode 24. The anode feed line 28 is configured to be in fluid communication with an anode inlet line 32 and an anode bypass line 34, the anode inlet line being configured to supply the hydrogen gas stream to the anode side 24, the anode bypass line being configured to divert a portion of the hydrogen gas stream to an inert gas generation system 36, the inert gas generation system being configured to generate water vapor to be used as an inert gas. An anode inlet flow control valve 33, schematically shown, is located in the anode feed line 28 and can be controlled to allow a portion of the hydrogen gas stream to be diverted from the anode feed line 28 to the inert gas generation system 36. The anode inlet flow control valve 33 can be any suitable flow control valve and can include one or more valves. The anode inlet flow control valve 33 and other valves shown herein and used in accordance with the examples of the present disclosure can be any suitable flow control valve, e.g., a three-way proportional valve or other types of valves configured to control the amount of the corresponding flow in a line or path coupled to the valve. The anode feed line 28, the anode inlet line 32, the anode bypass line 34, and the anode outlet line 29 are shown in Figure 2A in dashed lines. Additionally, a dashed line shows line 35, which indicates that the inert gas generation system 36 may discharge a residual hydrogen gas stream 35 in the case where the hydrogen gas directed to the system 36 is not fully consumed. The residual hydrogen gas stream can be directed back to the anode side 24 ( Figure 2A not shown in the figure) or discharged to the external environment.

[0062] The cathode side 26 is configured to receive air or an air stream via a cathode inlet path or line 38 (e.g., from the surrounding environment). The cathode side 26 is configured to provide a cathode exhaust stream via a cathode outlet path or line 40. The cathode exhaust stream can include liquid water and steam produced as by-products of the electrochemical reaction in the fuel cell stack 22a. The cathode exhaust stream can be carried away from the cathode side 26, e.g., to the outside of the vehicle 10, as shown by line 50. In some implementations, the liquid water and steam can be at least partially treated and reused - for example, the liquid water can be extracted from the cathode exhaust stream.

[0063] In Figure 2AIn an example, the cathode outlet line 40 is fluidly coupled to a cathode recirculation channel or loop 42 configured to divert a portion of the cathode exhaust stream to the cathode inlet line 38. The cathode recirculation channel or loop 42 may also be referred to as an exhaust gas recirculation (EGR) loop or channel. The configuration of the cathode recirculation channel (such as, for example, cathode recirculation channel 42) according to aspects of the present disclosure may depend on the overall layout of the fuel cell system, the components used, the power level requirements, and the like.

[0064] In some examples, one or both of the cathode outlet line 40 and the cathode recirculation channel 42 may include a water separator or another similar component configured to extract water from the cathode exhaust stream. The presence of one or more water separators is optional and may depend on the amount of liquid water present in the cathode exhaust. In some examples, there may be one or more water separators, and the water separator(s) may be selectively activated, for example, when it is desired to reduce the amount of liquid water in the cathode exhaust stream. It may be desirable to provide a drier cathode exhaust to the air stream supplied to the cathode.

[0065] The fuel cell system 22a further includes a cathode bypass channel or loop 44 configured to be in fluid communication with the cathode recirculation channel 42 and configured to divert a portion of the cathode exhaust stream to the inert gas generation system 36. Thus, the inert gas generation system 36 is configured to generate an inert gas when the cathode exhaust and a hydrogen stream are fed to the system 36. The inert gas generation system 36 may include a catalyst, such as a platinum (Pt) or palladium (Pd) catalyst, and is configured to generate an inert gas, such as, for example, water, such as water vapor, when oxygen and hydrogen are supplied to the system 36. In some examples, the inert gas generation system 36 includes a catalytic container, such as, for example, a tank or a chamber, that includes a catalytic material that drives the production of water and nitrogen when reacting with the hydrogen and oxygen supplied to the container. The amount of inert gas generated by the inert gas generation system 36 may be proportional to the amount of hydrogen flowing into the system 36.

[0066] As Figure 2A shown, a cathode outlet flow control valve 41 may be located in the cathode outlet line 40 and may be controlled to allow a portion of the cathode exhaust stream to be diverted to the cathode recirculation channel 42. A recirculation pump 46 in the cathode recirculation channel 42 may be configured to pump the cathode exhaust stream through the cathode recirculation channel 42 and also through the cathode bypass loop 44.

[0067] Furthermore, as Figure 2AAs shown, by way of example, the first cathode bypass valve 45 may be located in the cathode recirculation passage 42 and may be controlled to allow a portion of the cathode exhaust stream to be diverted through the cathode bypass loop 44 that includes the inert gas generation system 36. The second cathode bypass valve 47 may be located in the cathode recirculation passage 42 and may be controlled to allow at least a portion of the inert gas generated by the inert gas generation system 36 to be provided from the cathode bypass loop 44 to the cathode inlet line 38 via the cathode recirculation passage 42. Additionally, the cathode inlet flow control valve 49 may be located in the cathode inlet line 38 and may be controlled to allow the cathode exhaust stream (which may be mixed with the inert gas when the cathode bypass loop 44 is open) to be provided to the cathode inlet line 38, thereby reducing the oxygen partial pressure in the air stream provided to the cathode side 26. The cathode inlet line 38, the cathode recirculation passage 42, the cathode bypass loop 44, and the cathode outlet line 50 are shown in Figure 2A solid lines.

[0068] The air stream for the cathode 26 may be obtained from the surrounding environment. The air may be filtered, for example, using a filter and pressurized by an air compressor 52. The air stream may be heated due to the compression by the air compressor 52. In some examples, the air compressor 52 may be an electric turbocharger (ETC) that includes a turbine and a compressor. The air compressor 52 may be fluidly coupled to a charge air cooler (CAC) 54 that is configured to cool the air stream in the cathode inlet line 38. The air stream may also be humidified by a humidifier 56.

[0069] Additionally, as Figure 2A schematically shown in, the fuel cell unit 21a includes a coolant loop or system 58 that is configured to circulate a coolant (referred to as a coolant stream) through the fuel cell unit 21. The coolant system 58 circulates the coolant stream that flows into the stack 22a via the coolant inlet line 60 and out of the stack 22a via the coolant outlet line 62. Although Figure 2A not shown in, the coolant system 58 may be in the form of a loop such that the coolant outlet line 62 may be in fluid communication with the coolant inlet line 60 to circulate the coolant through the stack 22a. The coolant system 58 may include components such as, for example, a radiator, a coolant tank for storing the coolant, a pump for circulating the coolant, and / or other components.

[0070] The operation of the fuel cell unit 21a may be controlled by the control system 30. In the examples herein, as Figure 2AAs shown, the control system 30 may include a processing circuit 32 configured to execute computer-executable instructions that, when executed by the processing circuit 32, may perform a method according to an example of the present disclosure. The control system 30 further includes a memory 31 configured to store the computer-executable instructions and various data.

[0071] The processing circuit 32 of the control system 30 may be configured to determine or estimate that the vehicle has or will operate with a reduced power demand from the fuel cell system for a period longer than a threshold period of time. The processing circuit 32 may be configured to control the operation of the fuel cell system 20a in response to estimating that the vehicle has or will operate with a reduced power demand such that a portion of the cathode exhaust flow is directed to the cathode inlet line 38. For example, a cathode outlet flow control valve 41 located at a point where the cathode outlet line 40 is coupled to the cathode recirculation passage 42 may be operated to allow a portion of the cathode exhaust flow to flow through the cathode recirculation passage 42. A first cathode bypass valve 45 and a second cathode bypass valve 47 located at points where the cathode bypass loop 44 is coupled to the cathode recirculation passage 42 may be operated to prevent the cathode exhaust flow from flowing through the cathode bypass loop 44 while the cathode exhaust flow is directed through the cathode recirculation passage 42 to the cathode inlet line 38. A cathode inlet flow control valve 49 located at a point where the cathode recirculation passage 42 is coupled to the cathode inlet line 38 may be controlled to, for example, partially open to allow the cathode exhaust flow to be directed to the cathode inlet line 38. Additionally, an anode inlet flow control valve 33 located at a point where the anode feed line 28 is coupled to the anode bypass line 34 may be controlled to, for example, partially open to allow a portion of the hydrogen gas stream that is normally fed to the anode 24 to be diverted to flow into the inert gas generation system 34 via the anode bypass line 34.

[0072] If a further reduction in the power requested from the fuel cell system occurs, the processing circuit 32 may instruct the fuel cell system 20a to generate an inert gas that is directed, along with a portion of the cathode exhaust flow, to the cathode inlet line 38. To cause the inert gas generation system 36 to generate the inert gas, the first cathode bypass valve 45 and the second cathode bypass valve 47 located at respective points where the cathode bypass loop 44 is coupled to the cathode recirculation passage 42 may be operated to allow at least a portion of the cathode exhaust flow to flow through the cathode bypass loop 44. The cathode exhaust flow enters the inert gas generation system 36 at an inlet 36i of the inert gas generation system 36, and the inert gas is provided at an output 36o of the inert gas generation system 36 such that a portion of the cathode bypass loop 44 carries the inert gas that is supplied to the cathode inlet line 38. It should be noted that in Figure 2A the hydrogen gas stream is shown as entering the inert gas generation system 36 from one side, i.e., from Figure 2AThe top entry shown in [Figure] is opposite the inlet 36i of the inert gas generation system 36 where the cathode exhaust stream enters the system 36; however, this is merely illustrative as the hydrogen and cathode exhaust streams can enter the inert gas generation system 36 from any suitable side, including entering from the same side, to cause the catalyst in the inert gas generation system 36 to generate inert gas. The cathode exhaust stream and the hydrogen stream can enter the inert gas generation system in a co-current flow or a cross-flow or any other combination.

[0073] In some examples, both the cathode exhaust stream from the cathode recirculation channel 42 and the inert gas from the cathode bypass loop 44 are carried to the inert gas generation system 36. Thus, the air stream fed to the cathode 26 can be mixed with the cathode exhaust stream and with the inert gas (such as, for example, water vapor), so that the oxygen partial pressure in the air stream is reduced according to the required increase in power requested from the fuel cell system. It should be noted that the cathode inlet or input stream fed to the cathode as an oxidant source for the electrochemical reaction in the fuel cell stack is referred to as an air stream, even if, for example, the air stream taken from the ambient environment is mixed with the cathode exhaust and / or with the inert gas. This notation is for descriptive purposes, but it should be understood that, according to examples of the present disclosure, the air stream with reduced oxygen partial pressure includes other components such as those found in the cathode exhaust stream and the inert gas (e.g., water vapor). The cathode exhaust stream can be filtered to remove impurities before being supplied to the cathode inlet line.

[0074] In some examples, the cathode exhaust stream can be directed to flow only to the inert gas generation system 36 without allowing the cathode exhaust stream to flow to the cathode inlet line 38. For example, a first cathode bypass valve 45 located at the point where the cathode recirculation channel 42 is connected to the cathode bypass loop 44 can be operated to direct all of the cathode exhaust stream in the cathode recirculation channel 42 to the cathode bypass loop 44. Thus, the air stream fed to the cathode 26 can be mixed only with the inert gas (such as, for example, water vapor), so that the oxygen partial pressure in the air stream is reduced according to the required increase in power requested from the fuel cell system.

[0075] Figure 2B An example of a fuel cell system 220 is shown, which includes a fuel cell unit 221 where the inert gas generation system is configured to receive an air stream taken from the external environment. Thus, in this example, instead of using the cathode exhaust stream, the air stream is the oxygen source for generating inert gas through the inert gas generation system. When the power demand of the fuel cell system decreases, the cathode exhaust stream can be delivered to the cathode inlet line, and when a greater reduction in power is needed, the air stream can be diverted to the inert gas generation system. When the inert gas is being generated, the cathode exhaust stream can continue to be delivered to the cathode inlet line, thereby reducing the oxygen partial pressure of the air stream in the cathode inlet line.

[0076] Figure 2B The fuel cell system 220 is generally similar to Figure 2A the fuel cell system 20a, and the discussion of similar components denoted by similar reference numerals will not be repeated in conjunction with Figure 2B this.

[0077] Figure 2B The fuel cell unit 221 of includes one or more fuel cell stacks, where Figure 2B the fuel cell stack 222 in is an example of a fuel cell stack. The fuel cell stack 222 includes an anode or anode side 224 and a cathode or cathode side 226 separated by an electrolyte (not shown), such as a PEM sandwiched between the anode 224 and the cathode 226.

[0078] The anode or anode side 224 is configured to receive a hydrogen gas stream via an anode feed line 228 and provide by-products of the operation of the anode side 224 to an anode outlet line 229, which is configured to draw the by-products out of the anode side 224. The anode feed line 228 is configured to be in fluid communication with an anode inlet line 232 and an anode bypass line 234, the anode inlet line being configured to supply a hydrogen gas stream to the anode side 224, the anode bypass line being configured to divert a portion of the hydrogen gas stream to an inert gas generation system 236. The inert gas generation system 236 includes a catalytic container, such as a tank or a chamber, that includes a catalytic material (e.g., a platinum (Pt) or palladium (Pd) catalyst), which drives the production of water and nitrogen when reacting with the hydrogen and oxygen supplied to the container.

[0079] Residual hydrogen gas unused in the inert gas generation system 236 can be discharged from the inert gas generation system 336 via a hydrogen gas residue line 235. The anode feed line 228, the anode outlet line 229, the anode inlet line 232, the anode bypass line 234, and the hydrogen gas residue line 235 are shown in Figure 2B in dashed lines.

[0080] The cathode side 226 is configured to receive air or an air stream via a cathode inlet path or 238 (e.g., from the surrounding environment). The air can be pressurized by an air compressor 252 and cooled by a CAC 254. There may also be a humidifier 256, which is configured to humidify the air stream in the cathode inlet path, as Figure 2B shown.

[0081] The cathode side 226 is configured to provide a cathode exhaust stream generated as a by - product of the electrochemical reaction in the fuel cell stack 222 via a cathode outlet path or line 240. The cathode outlet line 240 is fluidly coupled to a cathode recirculation loop or passage 242 that is configured to divert a portion of the cathode exhaust stream to the cathode inlet line 238. The cathode recirculation passage or loop 242 may also be referred to as an EGR loop or passage. A cathode outlet flow control valve 241 located at the point where the cathode recirculation passage 242 is coupled to the cathode outlet line 240 may be used to control the flow of the cathode exhaust stream from the cathode outlet line 240 to the cathode recirculation passage 242.

[0082] The cathode outlet line 240 may include a recirculation pump, which may be similar to Figure 2B the recirculation pump 46 shown. In some examples, as Figure 2B shown, there may be no recirculation pump because less power may be required to circulate the cathode exhaust stream through the cathode recirculation passage when there is no cathode bypass loop.

[0083] As Figure 2B shown, the cathode recirculation passage 242 is coupled to the cathode inlet line 238 downstream of the humidifier 256. As used herein, a downstream position is a position along the cathode inlet line that is closer to the cathode and farther from the air compressor in the direction in which air in the cathode inlet line flows toward the cathode. As used herein, an upstream position is a position along the cathode inlet line that is closer to the air compressor and farther from the cathode in a direction opposite to the direction in which the air flow is carried toward the cathode in the cathode inlet line.

[0084] A cathode inlet flow control valve 249 located at the point where the cathode recirculation passage 242 is coupled to the cathode inlet line 238 may be used to control the flow of the cathode exhaust stream from the cathode recirculation passage 242 to the cathode inlet line 238. When the power demand of the fuel cell system 220 is reduced, valves 241 and 249 may be controlled to allow a portion of the cathode exhaust stream to be diverted from the cathode outlet line 240 through the cathode recirculation passage 242 into the cathode inlet line 238.

[0085] In some examples, one or both of the cathode outlet line 240 and the cathode recirculation passage 242 may include a water separator or another similar component configured to extract water from the cathode exhaust stream.

[0086] As Figure 2BAs shown, the fuel cell system 220 includes an air flow bypass line 264 that is in fluid communication with the cathode inlet line 238, where the air flow bypass line 264 is configured to divert a portion of the air flow from the cathode inlet line 238 to the inert gas generation system 236 in the direction schematically shown by arrow 270. The air flow bypass line 264 is also configured to supply the inert gas generated by the inert gas generation system 236 to the cathode inlet line 238, as schematically shown by arrow 272. Thus, a portion of the air flow bypass line 264 is configured to convey or supply air to the inert gas generation system 236, while another portion of the air flow bypass line 264 is configured to convey or supply the inert gas to the cathode inlet line 238. If the fuel cell system requires lower power, a greater amount of the air flow will be directed through the catalyst of the inert gas generation system 236.

[0087] In this example, the air flow bypass line 264 is fluidly coupled to the cathode inlet line 238 at a point labeled A upstream of the CAC 254 such that ambient air pressurized by the air compressor 252 is supplied as an input to the catalyst of the inert gas generation system 236. A first air flow control valve 237 located at the point or junction A between the cathode inlet line 238 and the air flow bypass line 264 is configured to control the flow of ambient air to the bypass line 264. In this implementation, when the air flow (e.g., fresh air) bypasses to flow to the system 236 after the air compressor 252 and before the CAC 254, the air temperature in the air flow will be much higher compared to the air that has passed through the CAC 254. In some scenarios, feeding warmer air to the cathode can improve the efficiency of the inert gas generation system 236, which requires less external energy for operation compared to the case of delivering colder air to the cathode. Figure 2B

[0088] As Figure 2B shown, the air flow bypass line 264 is also fluidly coupled to the cathode inlet line 238 at a point labeled B downstream of the CAC 254, where the inert gas can be provided to the cathode inlet line 238. The flow rate of the inert gas entering the cathode inlet line 238 can be controlled by a second air flow control valve 239 located at the point or junction B between the cathode inlet line 238 and the air flow bypass line 264. The first air flow valve 237 and the second air flow valve 239 can be controlled (e.g., their opening degrees can be controlled) to allow a portion of the air flow provided by the air compressor 252 to be directed to the air flow bypass line 264. This may occur when the oxygen partial pressure in the air flow supplied to the cathode 226 needs to be further reduced as the power demand of the fuel cell system 220 is further decreased.

[0089] ​It should be noted that in some implementations, the air flow bypass line 264 can be coupled to the cathode inlet line 238 to supply an inert gas to the cathode inlet line 238 downstream of the humidifier 256. In such implementations, for example, point B can be located downstream of the humidifier 256, and a valve (such as, for example, the second air flow control valve 239) can be located downstream of the humidifier 256.

[0090] In addition, in some implementations, the air flow bypass line 264 can be coupled to the cathode inlet line 238 to receive air from the cathode inlet line 238 downstream of the CAC 254 and upstream of the humidifier 256 (e.g., between the CAC 254 and the humidifier 256). Thus, the point corresponding to Figure 2B point A as shown can be located between the CAC 254 and the humidifier 256, rather than Figure 2B upstream of the CAC 254 as shown.

[0091] In some implementations, the air flow bypass line 264 can be coupled to the cathode inlet line 238 to receive air from the cathode inlet line 238 upstream of the humidifier 256. Thus, the point corresponding to Figure 2B point A in

[0092] In addition, Figure 2B point B (marking a portion of the cathode inlet line 238 where the air flow bypass line 264 is coupled to the cathode inlet line) as shown in Figure 2B can be located at a position different from the position shown in

[0093] depending on the position of point A. Those skilled in the art will understand how to implement the fuel cell system such that the air flow bypass line is coupled to the cathode inlet line at various positions along the cathode inlet line, and thus examples of such implementations are not shown in detail herein. Figure 2A The fuel cell system 220 also includes a coolant system 258 shown in dashed lines, which is similar to the

[0094] coolant system 58 of Figure 2BThe control system 30) shown is used for control. When it is estimated that a vehicle including the fuel cell system 220 is operating or is expected to operate with a reduced power demand of the fuel cell system in the near future, the fuel cell system 220 can be controlled according to the requested power requested from the fuel cell system. The cathode exhaust stream can be recycled to the cathode inlet line 238 and / or the inert gas generation system 236 can be controlled to generate inert gas using a portion of the air stream and a portion of the hydrogen stream.

[0095] In an implementation of a fuel cell system according to an example of the present disclosure, the cathode recirculation channel can be coupled to the cathode inlet line at various positions along the cathode inlet line. Thus, referring again to Figure 2A , the cathode recirculation channel 42 is coupled to the cathode inlet line 38 downstream of the humidifier 56, which is located downstream of the air compressor 52 and the CAC 54.

[0096] Figure 3 and Figure 4 illustrate examples of different positions where the cathode recirculation channel of a fuel cell system can be coupled to the cathode inlet line, which is configured to deliver the cathode inlet flow to the cathode. Figure 3 and Figure 4 The fuel cell systems of Figure 2A are similar to the fuel cell systems of Figure 3 and Figure 4 and thus the components of the fuel cell systems shown in Figure 3 and Figure 4 will not be described in detail herein. Similar components are labeled with similar reference numerals, and similar features (e.g., valves and recirculation pumps) are shown using similar symbols. The valves are not labeled in Figure 3 and Figure 4 and it should be understood that they are controlled according to the requested power requested from the fuel cell system when the power demand of the fuel cell system is reduced.

[0097] Figure 3 illustrates an example of a fuel cell system 320 that includes a fuel cell unit 321, which includes one or more fuel cell stacks, where Figure 3 the fuel cell stack 322 shown in is an example of a battery stack. The battery stack 322 includes an anode or anode side 324 and a cathode or cathode side 326 separated by an electrolyte (not shown), such as, for example, a PEM sandwiched between the anode 324 and the cathode 326.

[0098] The anode or anode side 324 is configured to receive a hydrogen gas stream via an anode feed line 328 and provide by-products of the operation of the anode side 324 to an anode outlet line 329, which is configured to draw the by-products out of the anode side 324. The anode feed line 328 is configured to be in fluid communication with an anode inlet line 332 and an anode bypass line 334, the anode inlet line being configured to supply a hydrogen gas stream to the anode side 324, the anode bypass line being configured to divert a portion of the hydrogen gas stream to an inert gas generation system 336. Residual hydrogen gas not consumed in the inert gas generation system 336 can be discharged from the inert gas generation system 336 via a hydrogen gas residue line 335. The anode feed line 328, the anode outlet line 329, the anode inlet line 332, the anode bypass line 334, and the hydrogen gas residue line 335 are shown in Figure 3 dashed lines in

[0099] The cathode side 326 is configured to receive air or an air stream via a cathode inlet line 338 (e.g., from the ambient environment). The cathode side 326 is configured to provide a cathode exhaust stream via a cathode outlet path or line 340. The cathode outlet line 340 is fluidly coupled to a cathode recirculation channel or loop 342, which is configured to divert a portion of the cathode exhaust stream to the cathode inlet line 338. The cathode recirculation channel or loop 342 may also be referred to as an exhaust gas recirculation (EGR) loop or channel. As Figure 3 shown, the cathode recirculation channel 342 is coupled to the cathode inlet line 338 downstream of an air compressor 352 but upstream of a CAC 354. A humidifier may also be present, and it may be located downstream of the CAC 354.

[0100] In some examples, one or both of the cathode outlet line 340 and the cathode recirculation channel 342 may include a water separator or another similar component configured to extract water from the cathode exhaust stream.

[0101] The fuel cell system 322 further includes a cathode bypass channel or loop 344, which is configured to be in fluid communication with the cathode recirculation channel 342. The cathode bypass loop 344 is configured to divert a portion of the cathode exhaust stream to the inert gas generation system 336 and supply an inert gas to the cathode recirculation channel 342, which carries the inert gas to the cathode inlet channel 338. The cathode inlet line 338, the cathode recirculation loop 342, the cathode bypass loop 344, and the cathode output line 350 are shown in Figure 3 solid lines in

[0102] The coolant system 358 includes a coolant inlet line 360 and a coolant outlet line 362 shown in dashed lines.

[0103] The operation of the fuel cell system 322 can be controlled by a controller or control system that can be similar to the control system 300 ( Figure 3 not shown). When it is estimated that the vehicle including the fuel cell system 322 is operating or is expected to operate with a reduced power demand of the fuel cell system, the fuel cell system 322 can be controlled based on the requested power requested from the fuel cell system. The cathode exhaust stream can be recirculated to the cathode inlet line 338 and / or the inert gas generation system 336 can be controlled to use a portion of the cathode exhaust stream and a portion of the hydrogen stream to generate inert gas.

[0104] Figure 4 An example of a fuel cell system 420 is shown, which includes a fuel cell unit 421 that includes one or more fuel cell stacks, where Figure 4 the fuel cell stack 422 shown therein is an example of a battery stack. The battery stack 422 includes an anode or anode side 424 and a cathode or cathode side 426.

[0105] The anode or anode side 424 is configured to receive a hydrogen stream via an anode feed line 428 and provide a by-product of the operation of the anode side 424 to an anode outlet line 429, which is configured to draw the by-product out of the anode side 424. The anode feed line 428 is configured to be in fluid communication with an anode inlet line 432 and an anode bypass line 434, the anode inlet line being configured to supply a hydrogen stream to the anode side 424, the anode bypass line being configured to divert a portion of the hydrogen stream to an inert gas generation system 436. Residual hydrogen not consumed in the inert gas generation system 436 can be discharged from the inert gas generation system 436 via a hydrogen residue line 435. The anode feed line 428, the anode outlet line 429, the anode inlet line 432, the anode bypass line 434, and the hydrogen residue line 435 are shown in Figure 4 dashed lines.

[0106] The cathode side 426 is configured to receive air or an air stream via a cathode inlet path or line 438 (e.g., from the surrounding environment). The cathode side 426 is configured to provide a cathode exhaust stream via a cathode outlet path or line 440. The cathode outlet line 440 is fluidly coupled to a cathode recirculation channel or loop 442, which is configured to divert a portion of the cathode exhaust stream to the cathode inlet line 438. As Figure 4 shown, the cathode recirculation channel 442 is coupled to the cathode inlet line 438 upstream of an air compressor 452. A CAC 354 is located downstream of the air compressor 452. A humidifier may also be present downstream of the CAC 454.

[0107] The fuel cell system 420 also includes a cathode bypass channel or loop 444 that is configured to be in fluid communication with the cathode recirculation channel 442. The cathode bypass loop 444 is configured to divert a portion of the cathode exhaust stream to the inert gas generation system 436 and provide the inert gas to the cathode recirculation channel 442, which carries the inert gas to the cathode inlet channel 438. The cathode inlet line 438, the cathode recirculation loop 442, the cathode bypass loop 444, and the cathode output line 450 are connected in a manner similar to the embodiment of the present invention. Figure 4 Shown in solid line.

[0108] Coolant system 458 includes a coolant inlet line and a coolant outlet line, shown in phantom.

[0109] The operation of the fuel cell system 420 may be similar to Figure 1 as well as Figure 2A and Figure 2B The controller or control system of the control system 30 ( Figure 4 When it is estimated that the vehicle including the fuel cell system 420 is operating or is expected to operate with a reduced power demand of the fuel cell system, the fuel cell system 420 may be controlled according to the requested power requested from the fuel cell system. The cathode exhaust stream may be recycled to the cathode inlet line 438 and / or the inert gas generation system 436 may be controlled to generate an inert gas using a portion of the cathode exhaust stream and a portion of the hydrogen stream.

[0110] Figure 5 An example process or method 500 is shown for operating a fuel cell system for a vehicle, the fuel cell system including a fuel cell unit including a fuel cell stack including a cathode side and an anode side, the cathode side being configured to receive an air flow and provide a cathode exhaust flow, the anode side being configured to receive a hydrogen flow. The fuel cell system may be Figure 1 The fuel cell system 20, or the fuel cell system 20a ( Figure 2A ), or a fuel cell system 220 ( Figure 2B ), or a fuel cell system 320 ( Figure 3 ), or a fuel cell system 420 ( Figure 4 ), or a fuel cell system having another configuration. The fuel cell system may be deployed in a fuel cell vehicle (e.g., Figure 1 The fuel cell system includes a cathode recirculation passage and an inert gas generating system, which are controlled to supply a cathode exhaust flow and an inert gas to an inlet of the cathode side, respectively, to reduce the oxygen partial pressure in the air flow fed to the cathode side.

[0111] The method 500 may be performed by a controller or control system (e.g.,Figure 1 , Figure 2A and Figure 2B The control system 30). The processing circuit 32 of the control system 30 can execute computer-executable instructions stored in, for example, the memory 31 of the control system 30, where the computer-executable instructions, when executed, cause the processing circuit to execute method 500.

[0112] Process 502 can start at any suitable time, for example, when the power output of the fuel cell system decreases. It should be understood that if the fuel cell system and some processing (e.g., obtaining the value of the power output and / or monitoring the state of the vehicle) can be continuously performed, then process 502 can be performed as part of the overall operation control regardless of whether the vehicle is operating in a low-power mode.

[0113] At block 502, the control system can obtain or acquire the value of the power output (also referred to as the requested power) requested from the fuel cell system during vehicle operation. The value of the power output can be the requested power currently requested from the fuel cell system during vehicle operation. In some examples, the value of the power output can be a predicted value of the power output expected to be requested from the fuel cell system. For example, for a fuel cell vehicle traveling on a route, the control system can predict that the vehicle is approaching a downhill section of the route where the vehicle will travel downhill. Based on the steepness of the hill, the length of the downhill section, and other factors (e.g., the weight of the vehicle that can carry a load), a forthcoming decrease in the power demand of the fuel cell system can be predicted or estimated. The decrease in power demand indicates that one or more lower values of power output are expected to be requested from the fuel cell system.

[0114] As another example, the control system can predict that the vehicle is expected to enter an idle mode, in which one or more lower values of power output are expected to be requested from the fuel cell system.

[0115] The value of the power output requested from the fuel cell system of the vehicle can include multiple values obtained during vehicle operation.

[0116] At optional block 503, the single cell voltage of the fuel cell stack of the fuel cell unit of the fuel cell system can be monitored. The measured value obtained by, for example, a voltage sensor can be used to determine the single cell voltage of the fuel cell stack. In some examples, the single cell voltage of the fuel cell stack can be determined as the measured voltage of the fuel cell stack divided by the number of fuel cells in the fuel cell stack. Thus, the single cell voltage can be determined as the average single cell voltage, and it represents the voltage of each fuel cell in each fuel cell stack, and the value of this voltage shall not exceed a safety threshold. In some examples, the single cell voltage can be determined by the measured voltage of the entire fuel cell unit, in which case the measured voltage is divided by the number of cell stacks and the number of cells in each cell stack. In some examples, the voltage of each fuel cell is measured, and the average of these measured voltages can be regarded as the single cell voltage of the fuel cell stack. Regardless of the method used to measure the single cell voltage of the fuel cell stack, the fuel cell system is controlled such that the single cell voltage does not exceed 0.8 V or 0.79 V as in some examples of the present disclosure.

[0117] It should be understood that when the fuel cell system is operating, the process at block 503 can be continuously executed. In addition, the process at block 503 can be executed simultaneously with Figure 5 other processing actions or operations shown in

[0118] At block 504, the control system determines whether the fuel cell system has or will operate with a reduced power demand for a period longer than a threshold period.

[0119] The state of the vehicle can be monitored, which can be done by the control system and / or another controller (e.g., the vehicle main controller communicatively coupled to the fuel cell system control system). In addition, various information related to the current, past, and / or predicted state of the vehicle can be obtained.

[0120] When the vehicle decelerates and / or when the vehicle idles to a stop (i.e., stops while operating in a low power mode), the power demand of the fuel cell system can be reduced. In some examples, when it is determined that the fuel cell system has or will operate with a reduced power demand for a period longer than a threshold period, the vehicle may be in an idle mode. As the vehicle may enter an idle mode when facing traffic conditions and other situations and being in or preparing for a braking event.

[0121] The control system can detect that the vehicle is currently operating with a reduced power demand of the fuel cell system, and the duration of this situation has been longer than a threshold duration. At block 502, a value of the power output requested from the fuel cell system can be obtained, and the power output value can be used to determine that the fuel cell system has been operating with a reduced power demand, or in other words, the load on the fuel cell system has been reduced.

[0122] In some examples, the control system can determine or predict or estimate that the vehicle is about to enter a mode or state where the power demand of the vehicle's fuel cell system is reduced. For example, the vehicle may be traveling on a route, such as as part of a mission / task assigned to the vehicle, and the control system can predict that the vehicle is expected to operate with a reduced power demand of the fuel cell system based on information about the route and information about the vehicle. The control system can store and / or obtain information about the driver's previous driving history of the vehicle, one or more routes traveled by the vehicle (including stops of the vehicle at certain locations), information about current and predicted environmental conditions, traffic information including roadblocks and congestion, and / or any other information that can be used to predict that the vehicle is about to enter a lower power mode (e.g., an idle mode). In some examples, the vehicle can be part of a fleet, and the mission assigned to the vehicle can have a starting point and an ending point, and information about the route between the starting point and the ending point, as well as the surrounding environment and the driver's behavior, can be used to predict when the vehicle is expected to enter the low power mode. Thus, the control system can cause the fuel cell system to start preparing in advance for the vehicle's low power mode, in which the power demand of the vehicle for the fuel cell system will be reduced.

[0123] It should be noted that the processing at block 504 can include the processing at block 502, or the processing at blocks 502 and 504 can be performed as part of the same processing. Thus, when obtaining the values of the power output requested or to be requested from the fuel cell system, the control system can determine that these values indicate a reduced power demand of the fuel cell system, and it has been detected or is expected that the power demand reduction will occur for a period longer than the threshold duration.

[0124] The threshold time period can be a time period when the vehicle's ESS (e.g., one or more batteries) is fully charged or nearly fully charged such that it cannot accept the excess power generated by the fuel cell system when the load on the fuel cell system is reduced (e.g., when the vehicle decelerates or enters an idle mode). The threshold time period can be set based on the state of charge and charge capacity of the ESS and other factors. In some examples, the threshold time period can be set dynamically such that it is selected based on the current state of charge of the ESS. In any case, the threshold time period can be selected to account for the fact that idle and low power operation events may occur for a duration long enough to fully charge the ESS such that the excess power or energy generated by the fuel cell system may need to be handled in some other way. For example, the excess power will need to be dissipated to the surrounding environment or the fuel cell system may even need to be shut down. To avoid these two undesirable options, the method according to an example of the present disclosure involves intentionally reducing the efficiency of the fuel cell system. Thus, the power generated by the fuel cell system can be reduced to a lower value without the risk of the single cell voltage increasing to a value where stack degradation may occur. Accordingly, the durability and lifespan of the fuel cell stack and the entire fuel cell system can be increased. As another advantage, more stable control of the net power of the fuel cell can be achieved.

[0125] At block 506, in response to determining that the vehicle has or will operate with a reduced power demand on the fuel cell system, the control system can compare the value of the power output requested from the fuel cell system with at least one threshold power level. The value of the requested power can be compared with one or more threshold power levels to determine if the power demand on the fuel cell system is low enough to require reducing the oxygen partial pressure in the cathode inlet stream fed to the cathode, thereby reducing the efficiency of the fuel cell system.

[0126] At block 508, the control system can determine if the value of the power output is below at least one threshold power level including a first threshold power level and above at least one threshold power level including a second threshold power level, where the second threshold power level is lower than the first threshold power level. In other words, it can be determined if the value of the power output is between the second threshold power level and the first threshold power level.

[0127] In some examples, the value of the requested power output may be below the first threshold power level but above a second threshold power level that is lower than the first threshold power. Thus, to allow the power output of the fuel cell system to be reduced to the desired lower value, it may be sufficient to supply a portion of the cathode exhaust stream to the cathode inlet line. If the value of the requested power output is further reduced, e.g., reduced to a value below the second threshold power level, then the oxygen partial pressure in the air stream fed to the cathode will need to be further reduced accordingly, as discussed below.

[0128] The first threshold power level can be, for example, about 60 kW. In some examples, the first threshold power level can vary in the range of about 60 kW to about 75 kW, or in the range of about 60 kW to about 70 kW. The second threshold power level can be, for example, about 50 kW, or about 40 kW, or about 30 kW, or about 20 kW. In some examples, the second threshold power level can include more than one value such that the value of the requested power output can be compared with more than one value of the second threshold power level. The first threshold power level and the second threshold power level can include other values as the examples of the present disclosure are not limited in this regard.

[0129] At block 510, in response to determining that the value of the power output is below at least one threshold power level including the first threshold power level and above the second threshold power level that is lower than the first threshold power level, the control system reduces the oxygen partial pressure of the air flow in the cathode inlet line by diverting a portion of the cathode exhaust flow to the cathode inlet line, which is configured to supply the air flow to the cathode.

[0130] The cathode exhaust flow has a low oxygen concentration because the oxygen in the air flow supplied at the input of the cathode has been consumed in the fuel cell stack. Thus, mixing the air flow with the air flow in the cathode inlet line reduces the oxygen partial pressure of the air flow in the cathode inlet line. In the cathode exhaust flow, most of the water may be in the gas phase.

[0131] In combination Figure 2A 、 Figure 2B 、 Figure 3 and Figure 4 describe examples of controlling a fuel cell system to divert a portion of the cathode exhaust flow to the cathode inlet line. For example, referring to Figure 2A , a portion of the cathode exhaust flow can be diverted to the cathode inlet line 38 via the cathode recirculation channel 42. Similarly, referring to Figure 2B , a portion of the cathode exhaust flow can be diverted to the cathode inlet line 238 via the cathode recirculation channel 242.

[0132] The amount of the cathode exhaust flow diverted to the cathode inlet line depends on the desired reduction in the oxygen partial pressure of the air flow delivered from an air source (e.g., ambient air) through the cathode inlet line to the cathode inlet. The control can be performed by controlling the opening degree of one or more valves configured to control the flow rate of the cathode exhaust flow entering the cathode inlet line via the cathode recirculation channel. Since the air flow is mixed with the cathode exhaust flow, the oxygen partial pressure in the air flow is reduced. The oxygen partial pressure in the air flow is reduced according to the requested power.

[0133] At block 512, in response to determining that the value of the power output requested from the fuel cell system is not between the second threshold power level and the first threshold power level, the control system determines whether the value of the power output is below at least one threshold power level including the second threshold power level.

[0134] In response to determining that the value of the power output is not below at least one threshold power level including the second threshold power level, process 500 can return to block 502 where another value of the power output can be obtained.

[0135] At block 514, in response to determining that the value of the power output requested from the fuel cell system is between the second threshold power level and the first threshold power level (i.e., the value of the power output is below at least one threshold power level including the second threshold power level), the control system reduces the oxygen partial pressure of the air flow in the cathode inlet line by controlling the inert gas generation system of the fuel cell system to generate an inert gas to be supplied to the cathode inlet line thereby further reducing the oxygen partial pressure of the air flow in the cathode inlet line.

[0136] The catalyst in the inert gas generation system can be configured to produce water mainly in the gas phase. Supplying the vapor to the cathode inlet line can further reduce the oxygen partial pressure of the air flow in the cathode inlet line. When a portion of the cathode exhaust flow is supplied to the air flow in the cathode inlet line, the inert gas in the form of vapor can allow the oxygen partial pressure of the air flow to be reduced to a lower value. Thus, a greater degree of reduction in the oxygen partial pressure can be achieved.

[0137] In some examples, the value of the requested power output may be low enough such that it is below a second threshold power level that is lower than the first threshold power level. For example, the vehicle may suddenly decelerate and the value of the requested power may rapidly decrease to a value lower than the second threshold power. In some examples, the value of the power output requested from the fuel cell system can decrease more slowly such that the value of the power output can first decrease to below the first threshold power level but above the second threshold power level, and then further decrease to below the second threshold power level which can include one or more values. As an example, the value of the power output can first decrease to below the first threshold power level (which can be 60 KW or a value greater than 60 kW), then decrease to below 40 KW, and then decrease to below 30 KW, where the second threshold power includes two second threshold power levels: -40 kW and 30 kW. As another example, the second threshold power can include 40 kW, or 30 kW, or 20 kW, or other suitable values.

[0138] In some cases, the value of the power output requested from the fuel cell system does not decrease to become below the second threshold power level.

[0139] The control system can control the fuel cell system to reduce the oxygen partial pressure of the air flow in the cathode inlet pipeline by controlling the inert gas generation system of the fuel cell system to generate inert gas, and the inert gas is supplied to the cathode inlet pipeline, and the cathode inlet pipeline transports the air flow mixed with the inert gas to the cathode.

[0140] In some examples, the cathode exhaust flow can also be diverted to the cathode inlet pipeline, such that both a portion of the cathode exhaust flow and the inert gas are supplied to the cathode inlet pipeline. In some examples, only the inert gas is supplied to the cathode inlet pipeline.

[0141] According to an example of the present disclosure, when the value of the power output requested from the fuel cell system is lower than or less than a second threshold power level, this indicates that it may be necessary to further reduce the oxygen partial pressure in the cathode air flow. The oxygen partial pressure in the air flow is reduced according to the requested power.

[0142] The second threshold power or power level can include more than one threshold power level, such that the value of the requested power can be compared with more than one value of the second threshold power. In some examples, the value of the requested power requested from the fuel cell system can first be reduced to be lower than a first threshold power but higher than the second threshold power, and then further reduced to or below the second threshold power, and the second threshold power can include one or more values. As an example, the value of the requested power can first be reduced to be lower than the first threshold power (the first threshold power can be 60 KW or a value greater than 60 kW), then reduced to be lower than 40 KW, and then reduced to be lower than 30 KW, where the second threshold power includes two second threshold power levels: -40 kW and 30 kW. The second threshold power can have any other value lower than the first threshold power. For example, the second threshold power can include 40 kW, or 30 kW, or 20 kW, or other suitable values.

[0143] It should be noted that the specific value or value range of the first threshold power and the one or more values of the second threshold power can depend on the nature of the fuel cell unit and the entire fuel cell system that can include one or more fuel cell units. In some examples according to aspects of the present disclosure, the fuel cell system includes one fuel cell unit, that is, a single fuel cell unit with high efficiency or higher efficiency.

[0144] In some examples, controlling the inert gas generation system to generate inert gas includes transferring a portion of the cathode exhaust stream provided to the cathode outlet line from the cathode side to the inert gas generation system and transferring a portion of the hydrogen gas to the inert gas generation system. The portion of the cathode exhaust stream can be transferred to the inert gas generation system via a cathode bypass circuit configured to be fluidly coupled to the cathode recirculation loop. The cathode bypass circuit can be controlled to transfer a portion of the cathode exhaust stream to the inert gas generation system, as discussed, for example, in conjunction with Figure 2A , Figure 3 and Figure 4 . The portion of the hydrogen gas can be transferred to the inert gas generation system via an anode bypass line configured to be fluidly coupled to the anode feed line. The anode bypass path can be controlled to transfer a portion of the hydrogen gas stream to the inert gas generation system, as discussed, for example, in conjunction with Figure 2A , Figure 2B , Figure 3 and Figure 4 .

[0145] In some examples, additionally, the cathode recirculation loop can be controlled to transfer a portion of the cathode exhaust stream into the cathode inlet line.

[0146] In some examples, controlling the inert gas generation system to generate inert gas includes: in response to a requested power being lower than a second threshold power, controlling an air stream bypass line of the fuel cell system to transfer a portion of the air stream to the inert gas generation system, and controlling the anode bypass path to transfer a portion of the hydrogen gas stream to the inert gas generation system, such that the inert gas generation system generates a controlled amount of inert gas based on the requested power. For example, as shown in Figure 2B , the air stream can be transferred to the inert gas generation system 236 via the air stream bypass line 264, and the inert gas generation system 236 generates inert gas based on the rate and amount of the air stream and hydrogen gas transferred to the inert gas generation system 236.

[0147] As the value of the requested power output continues to decrease, the fuel cell system and / or the inert gas generation system can be controlled to continue operating such that the inert gas generation system generates inert gas, which can be supplied to the air stream fed to the cathode. The amount and flow rate of the hydrogen gas stream and the amount and flow rate of the cathode exhaust stream or air stream can be adjusted to thereby control the generation of inert gas by the inert gas generation system.

[0148] In some cases, the value of the requested power output can remain relatively stable, such that the inert gas can be generated at a relatively constant rate (such as without increase). In any case, the fuel cell system can control the supply of the required reactants to the inert gas generation system according to the power requested from the fuel cell system, and the inert gas generation system can generate water vapor in a controller manner according to the power requested from the fuel cell system. Although Figure 5 is not explicitly shown, for example, when the vehicle is operating in an idle mode or a low power mode, the value of the power output requested from the fuel cell system can be continuously obtained.

[0149] At block 516, the control system can optionally determine whether the value of the power output requested from the fuel cell system is further reduced. If this is the case, the process 500 can return to block 514 to continue reducing the oxygen partial pressure of the air flow in the cathode inlet line.

[0150] In response to determining that the value of the power output is no longer further reduced, the process 500 can end, as Figure 5 shown. However, it should be understood that the process 500 can be continuously executed when the fuel cell system is operating. For example, as the load on the fuel cell system increases, the process 500 can return to block 502, where one or more subsequent values of the requested power output can be obtained or acquired.

[0151] Figure 6 An example of a process 600 that can be executed when the value of the power output requested from the fuel cell system increases is shown. The fuel cell system can be Figure 1 the fuel cell system 20, or the fuel cell system 20a ( Figure 2A ), or the fuel cell system 220 ( Figure 2B ), or the fuel cell system 320 ( Figure 3 ), or the fuel cell system 420 ( Figure 4 ), or a fuel cell system with another configuration. The fuel cell system can be deployed in a fuel cell vehicle (e.g., Figure 1 the vehicle 10 in).

[0152] For example, when the vehicle exits the idle mode or the low power mode, the load on the fuel cell system may increase. For example, the vehicle may start to accelerate, or the vehicle may start to move after idling for a period of time.

[0153] The process 600 can be executed by the control system 30. When the fuel cell system is operating, for example, when the vehicle is traveling on a route and the load on the fuel cell system changes such that the power demand of the fuel cell system changes, as the power demand decreases, the control system 30 can according to Figure 5Process 500 performs processing, and as the power demand increases (which may occur after a power demand decrease), the control system can, in accordance with Figure 6 process 600 performs processing.

[0154] At block 602, the control system can obtain or acquire or receive a value of the power output (also referred to as the requested power) requested from the fuel cell system during vehicle operation. The value of the power output can be the requested power currently requested from the fuel cell system during vehicle operation. In some examples, the value of the power output can be a predicted value of the power output expected to be requested from the fuel cell system. It should be noted that the processing at block 602 can be performed as part of the processing at block 502 in Figure 5 since processes 500 and 600 can be performed as part of the coordinated control of the operation of the fuel cell system.

[0155] At block 604, the control system can determine that the fuel cell system is no longer operating at a reduced power demand and that the requested power is greater than at least one threshold power level. This can be determined based on the acquired value of the power output requested from the fuel cell system. The at least one threshold power level can be, for example, the second threshold power level associated with Figure 5 described. However, in some examples, the at least one threshold power level can have a value different from the second threshold power level. In other words, when the power demand of the fuel cell system increases, the control of the fuel cell system does not need to be based on the same threshold levels as those used to control the fuel cell system when the power demand of the fuel cell system decreases.

[0156] At block 606, in response to determining that the requested power is greater than at least one threshold power level, the control system can control the inert gas generation system to supply a reduced amount of inert gas to the cathode inlet line, control the cathode bypass loop to divert a reduced amount of the cathode exhaust flow to the inert gas generation system or control the air flow bypass line to divert a reduced amount of the air flow to the inert gas generation system, and control the anode bypass path to divert a reduced amount of the hydrogen flow to the catalyst system.

[0157] As discussed above, the inert gas generation system can receive a portion of the cathode exhaust flow or a portion of the air flow as an oxygen source for the catalyst of the inert gas generation system. Thus, in some examples, for example, as Figure 2A shown, the fuel cell system can be controlled such that the cathode bypass loop is controlled to divert a reduced amount of the cathode exhaust flow to the inert gas generation system. In some examples, for example, as Figure 2B shown, the fuel cell system can be controlled such that the air flow bypass line is controlled to divert a reduced amount of the air flow to the inert gas generation system.

[0158] At block 608, as the requested power output is further reduced and as the inert gas generation system stops supplying inert gas to the cathode inlet line, the control system can control the cathode bypass loop to stop diverting the cathode exhaust stream to the inert gas generation system or control the anode bypass path to stop diverting the hydrogen stream to the inert gas generation system. The further reduction of the requested power output can be detected based on a monitored value of the power output requested from the fuel cell system. The value of the power output can also be compared to at least one threshold power level.

[0159] In some examples, such as as Figure 2A shown, the fuel cell system can be controlled such that the cathode bypass loop is controlled to stop diverting the cathode exhaust stream to the inert gas generation system. In one example, such as as Figure 2B shown, the fuel cell system can be controlled such that the air flow bypass line is controlled to stop diverting the air flow to the inert gas generation system.

[0160] At block 610, the control system can control the cathode recirculation passage to gradually stop diverting the cathode exhaust stream into the cathode inlet line. As mentioned above, when inert gas is generated and supplied to the cathode inlet line, the cathode recirculation passage can divert a portion of the cathode exhaust stream. In such examples, the flow rate of the cathode exhaust entering the cathode inlet line can be gradually reduced until it stops completely.

[0161] In some cases, in addition to the inert gas, no cathode exhaust stream may be supplied to the cathode inlet line.

[0162] Process 600 can be performed as the power demand on the fuel cell system increases until, for example, the fuel cell system returns to normal operating conditions. The value of the power output requested from the fuel cell system can be continuously obtained, and the vehicle state can be monitored to determine whether, when the power demand of the fuel cell system decreases, the fuel cell system may then need to again reduce the oxygen partial pressure in the air stream supplied to the cathode.

[0163] To perform the method steps described herein, control system 30 can be configured to perform the processes described in connection with Figure 5 and Figure 6 and / or any other example according to the present disclosure. As shown, for example, in Figure 2A and Figure 2B control system 30 can include, for example, the arrangement shown in Figure 7A and Figure 7B Control system 30 can be located in any suitable location of vehicle 10 or in another system that implements the methods according to aspects of the present disclosure.

[0164] As Figure 7AAs shown, control system 30 includes processing circuitry 32, a memory 31, and an input and output interface 700 that is configured to communicate with any necessary components and / or entities of the examples herein. The input and output interface 700 may include wireless and / or wired receivers and wireless and / or wired transmitters. In some examples, the input and output interface 700 may include wireless and / or wired transceivers. Control system 30 may use the input and output interface 700 to control and communicate with various sensors, actuators, subsystems, and / or interfaces in the fuel cell system and vehicle 10 by using any one or more of the following: a controller area network (CAN) bus, an Ethernet cable, Wi-Fi, Bluetooth, and / or other network interfaces.

[0165] The methods described herein may be implemented using processing circuitry (e.g., one or more processors such as processing circuitry 32 of control system 30) together with computer program code stored in a computer-readable storage medium for performing the functions and actions of the examples herein.

[0166] Memory 31 may include one or more memory units. Memory 31 includes computer-executable instructions executable by processing circuitry 32 of control system 30. Memory 31 is configured to store, for example, information, data, etc., as well as computer-executable instructions that, when executed by processing circuitry 32, perform the methods according to the examples herein. Control system 30 may additionally obtain information from an external memory.

[0167] The methods according to aspects of the present disclosure may be implemented, for example, by a computer program product 710 or a computer program including computer-executable instructions (i.e., software code portions) that, when executed on at least one processor (e.g., processing circuitry 32), cause the at least one processor to perform the actions described herein as performed by control system 30.

[0168] In some examples, computer program product 710 is stored on a computer-readable storage medium 720. The computer-readable storage medium 720 may be, for example, a disk, a universal serial bus (USB) stick, or a similar device. The computer-readable storage medium 720 having the computer program product stored thereon may include computer-executable instructions that, when executed by processing circuitry 32, cause processing circuitry 32 to perform the actions of the methods according to the examples of the present disclosure described herein as performed by control system 30.

[0169] As Figure 7B shown, control system 30 may include an obtaining unit 702. Control unit system 30, processing circuitry 32, and / or obtaining unit 702 may be configured to

[0170] Obtain or acquire the value of the power output (also referred to as the requested power) requested from the fuel cell system during vehicle operation.

[0171] The control system 30 may include a monitoring unit 704. The control unit system 30, the processing circuit 32, and / or the monitoring unit 704 may be configured to monitor the single cell voltage, as discussed, for example, in connection with Figure 5 block 503.

[0172] As Figure 7B shown, the control system 30 may include a determination unit 706. The control system 30, the processing circuit 32, and / or the determination unit 706 may be configured to estimate or determine whether the fuel cell system has or will operate at a reduced power demand of the fuel cell system for a period longer than a threshold period, as discussed, for example, in connection with Figure 5 block 504.

[0173] The control system 30, the processing circuit 32, and / or the determination unit 706 are configured to estimate or determine whether the fuel cell system has or will operate at a reduced power demand of the fuel cell system for a period longer than a threshold period, as discussed, for example, in connection with Figure 5 block 504.

[0174] The control system 30, the processing circuit 32, and / or the determination unit 706 may be configured to compare the value of the power output requested from the fuel cell system with at least one threshold power level, as discussed, for example, in connection with Figure 5 block 506.

[0175] The control system 30, the processing circuit 32, and / or the determination unit 706 are configured to determine whether the value of the power output is below at least one threshold power level including a first threshold power level and above at least one threshold power level including a second threshold power level, where the second threshold power level is lower than the first threshold power level. In other words, it may be determined whether the value of the power output is between the second threshold power level and the first threshold power level, as discussed in connection with Figure 5 block 508.

[0176] As Figure 7B further shown, the control system 30 may include a control unit 708. The control system 30, the processing circuit 32, and / or the determination unit 708 may be configured to, in response to determining that the value of the power output is below at least one threshold power level including a first threshold power level and above a second threshold power level lower than the first threshold power level, reduce the oxygen partial pressure of the air flow in the cathode inlet line by diverting a portion of the cathode exhaust flow to the cathode inlet line, which is configured to supply the air flow to the cathode. For example, in connection with Figure 5The box 510 describes an example of such processing.

[0177] The control system 30, the processing circuit 32, and / or the control unit 708 may also be configured to determine whether the value of the power output requested from the fuel cell system is below at least one threshold power level including the second threshold power level in response to determining that the value of the power output requested from the fuel cell system is not between the second threshold power level and the first threshold power level.

[0178] The control system 30, the processing circuit 32, and / or the control unit 708 are configured to reduce the oxygen partial pressure of the air flow in the cathode inlet line by controlling the inert gas generation system of the fuel cell system to generate the inert gas to be supplied to the cathode inlet line to thereby further reduce the oxygen partial pressure of the air flow in the cathode inlet line in response to determining that the value of the power output requested from the fuel cell system is between the second threshold power level and the first threshold power level (i.e., the value of the power output is below at least one threshold power level including the second threshold power level). For example, in combination with Figure 5 The box 514 describes an example of such processing.

[0179] The control system 30 may be configured to execute Figure 6 The process 600 shown. Thus, the control system 30, the processing circuit 32, and / or the determination unit 706 may be configured to determine that the fuel cell system is no longer operating at the reduced power demand and that the value of the power output requested from the fuel cell system is greater than the at least one threshold power, as discussed in connection with Figure 6 The box 604. The control system 30, the processing circuit 32, and / or the control unit 708 may be configured to: in response to determining that the value of the power output is greater than the at least one threshold power, control the inert gas generation system to supply the reduced amount of inert gas to the cathode inlet line, control the cathode bypass line to divert the reduced amount of cathode exhaust flow to the inert gas generation system or control the air flow bypass line to divert the reduced amount of air flow to the inert gas generation system, and control the anode bypass path to divert the reduced amount of hydrogen flow to the inert gas generation system; and as the value of the power output further decreases and as the inert gas generation system stops supplying the inert gas to the cathode inlet line, control the cathode bypass line to stop diverting the cathode exhaust flow to the catalyst system and control the anode bypass path to stop diverting the hydrogen flow to the inert gas generation system.

[0180] In some examples, the control system 30, the processing circuit 32, and / or the control unit 708 may be configured to gradually stop diverting the cathode exhaust flow into the cathode inlet line in the cathode recirculation channel.

[0181] The control system 30 and / or the processing circuitry 32 may include other units or subunits configured to perform processing in accordance with examples of the present disclosure.

[0182] Those skilled in the art will appreciate that the units in the control system 30 described above may refer to a combination of analog and digital circuitry and / or one or more processors configured with, for example, software and / or firmware stored in the control system 30, which software and / or firmware, when executed by the corresponding one or more processors, may perform the methods according to the embodiments of the present disclosure. One or more of these processors and other digital hardware may be included in a single application specific integrated circuit (ASIC), or several processors and various digital hardware may be distributed across several separate components, either individually packaged or assembled into a system-on-chip.

[0183] The operational steps described in any of the exemplary aspects herein are described to provide examples and discussion. These steps may be performed by hardware components, embodied in machine-executable instructions to cause a processor to perform these steps, or performed by a combination of hardware and software. Although a specific order of method steps may be shown or described, the order of the steps may vary. Additionally, two or more steps may be performed simultaneously or partially simultaneously.

[0184] The terms used herein are for the purpose of describing particular aspects only and are not intended to limit the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term "and / or" includes any and all combinations of the associated listed items. It should also be understood that the terms "comprises" and / or "comprising", when used herein, specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0185] It should be understood that although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the present disclosure, a first element may be termed a second element, and similarly, a second element may be termed a first element.

[0186] In this document, relative terms such as "below" or "above", or "upper" or "lower", or "horizontal" or "vertical" may be used to describe the relationship of one element to another element, as shown in the figures. It should be understood that these terms, as well as those discussed above, are intended to cover different device orientations in addition to the orientation depicted in the figures. It should be understood that when an element is referred to as "connected to" or "coupled to" another element, the element can be directly connected or coupled to the other element or there may be intervening elements. In contrast, when an element is referred to as "directly connected to" or "directly coupled to" another element, there are no intervening elements.

[0187] Unless otherwise defined, all terms used in this document (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It should also be understood that, unless clearly defined herein, the terms used in this document should be interpreted as having a meaning consistent with their meaning in the context of this specification and the relevant art, and should not be interpreted in an idealized or overly formal sense.

[0188] It should be understood that the present disclosure is not limited to the aspects described above and shown in the figures; rather, those skilled in the art will recognize that many changes and modifications can be made within the scope of the present disclosure and the appended claims. In the figures and the specification, several aspects have been disclosed for illustrative purposes only and not for limiting purposes, and the scope of the inventive concept is set forth in the claims above.

Claims

1. A fuel cell system (20, 20a, 220, 320, 420) for a vehicle (10), the fuel cell system comprising: At least one fuel cell unit (21, 221, 321, 421), the at least one fuel cell unit comprising a fuel cell stack (22, 22a, 222, 322, 422), the fuel cell stack comprising: a cathode side (26, 226, 326, 426) configured to receive an air flow via a cathode inlet line and configured to provide a cathode exhaust flow via a cathode outlet line, the cathode outlet line being fluidly coupled to a cathode recirculation passage configured to divert a portion of the cathode exhaust flow to the cathode inlet line; an inert gas generation system (36, 236, 336, 436) configured to generate an inert gas supplied to the cathode inlet line; an anode side (24, 224, 324, 424) configured to receive a hydrogen gas stream via an anode feed line configured to be in fluid communication with an anode inlet line configured to supply the hydrogen gas stream to the anode side and an anode bypass line configured to divert a portion of the hydrogen gas stream to the inert gas generation system; and A control system (30), the control system comprising a processing circuit (32), the processing circuit being configured to: determining that the fuel cell system has been or will be operated at a reduced power demand of the fuel cell system for a period of time longer than a threshold period of time; responsive to determining that the fuel cell system has been or will be operating at the reduced power demand, comparing the value of the power output requested from the fuel cell system to at least one threshold power level; in response to determining that the value of the power output is below the at least one threshold power level including a first threshold power level and above the at least one threshold power level including a second threshold power level, controlling the cathode recirculation passage to divert a portion of the cathode exhaust flow into the cathode inlet line; and In response to determining that the value of the power output is below the second threshold power level, controlling a cathode bypass loop in fluid communication with the cathode recirculation channel to divert a portion of the cathode exhaust stream to the inert gas generation system or controlling an air flow bypass line in fluid communication with the cathode inlet line to divert a portion of the air flow to the inert gas generation system, and The anode bypass path is controlled to divert a portion of the hydrogen flow to the inert gas generation system, thereby causing the inert gas generation system to generate a controlled amount of inert gas. 2 . The fuel cell system of claim 1 , wherein when the vehicle is in an idle mode, it is determined that the fuel cell system has been or will be operated at the reduced power demand.

3. A fuel cell system according to claim 1 or 2, wherein the processing circuit of the control system is configured to control the cathode bypass channel to divert the portion of the cathode exhaust flow to the inert gas generation system in response to determining that the value of the power output is lower than the second threshold power level, and control the anode bypass path to divert the portion of the hydrogen flow to the inert gas generation system, so that the inert gas generation system generates the controlled amount of inert gas according to the value of the power output. 4 . The fuel cell system of claim 3 , wherein the processing circuit is further configured to control the cathode recirculation passage to divert a portion of the cathode exhaust flow into the cathode inlet line.

5. A fuel cell system according to claim 1 or 2, wherein the processing circuit is configured to control the air flow bypass line to divert the portion of the air flow to the inert gas generation system, and control the anode bypass path to divert the portion of the hydrogen flow to the inert gas generation system in response to determining that the value of the power output is lower than the second threshold power level, so that the inert gas generation system generates the controlled amount of inert gas according to the value of the power output.

6. A fuel cell system according to any one of claims 1 to 5, wherein determining that the fuel cell system has been or will be operating at the reduced power demand for a period of time longer than the threshold time period is performed based on one or more characteristics of the route traveled by the vehicle.

7. The fuel cell system according to any one of claims 1 to 6, wherein the processing circuit is configured to: determining that the fuel cell system is no longer operating at the reduced power demand and the value of the power output requested from the fuel cell system is greater than the at least one threshold power; in response to determining that the value of the power output is greater than the at least one threshold power, controlling the inert gas generation system to supply the reduced amount of inert gas to the cathode inlet line, controlling the cathode bypass line to divert the reduced amount of cathode exhaust flow to the inert gas generation system or controlling the air flow bypass line to divert the reduced amount of air flow to the inert gas generation system, and controlling the anode bypass path to divert the reduced amount of hydrogen flow to the inert gas generation system; as well as As the value of the power output further decreases and as the inert gas generation system stops supplying the inert gas to the cathode inlet pipeline, the cathode bypass line is controlled to stop diverting the cathode exhaust flow to the catalyst system and the anode bypass path is controlled to stop diverting the hydrogen flow to the inert gas generation system.

8. The fuel cell system according to claim 7, wherein the processing circuit is further configured to The cathode recirculation passage is controlled to gradually stop diverting the cathode exhaust flow into the cathode inlet line.

9. A fuel cell vehicle (10) comprising the fuel cell system according to any one of claims 1 to 8.

10. A method for operating a fuel cell system for a vehicle, the fuel cell system comprising at least one fuel cell unit, the at least one fuel cell unit comprising a fuel cell stack, the fuel cell stack comprising: a cathode side configured to receive an air flow and provide a cathode exhaust flow; and an anode side, the anode side being configured to receive a flow of hydrogen, the method comprising: determining ( 504 ) that the fuel cell system has been or will be operated at a reduced power demand of the fuel cell system for a period of time longer than a threshold period of time; In response to determining that the fuel cell system has been or will be operating at a reduced power demand, comparing the value of the power output requested from the fuel cell system to at least one threshold power level (506); In response to determining that the value of the power output is below the at least one threshold power level including a first threshold power level and above the at least one threshold power level including a second threshold power level, reducing (510) an oxygen partial pressure of the gas flow in the cathode inlet line by diverting a portion of the cathode exhaust flow into a cathode inlet line configured to supply the gas flow to the cathode; and In response to determining that the value of the power output is below the second threshold power level, the oxygen partial pressure of the air flow in the cathode inlet pipeline is reduced (514) by controlling an inert gas generation system of the fuel cell system to generate an inert gas that is supplied to the cathode inlet pipeline to thereby further reduce the oxygen partial pressure of the air flow in the cathode inlet pipeline.

11. The method according to claim 10, wherein controlling the inert gas generation system to generate the inert gas comprises: diverting a portion of the cathode exhaust stream to the inert gas generation system; as well as A portion of the hydrogen gas is transferred to the inert gas generation system.

12. A method according to claim 10 or 11, comprising, in response to determining that the value of the power output is below the second threshold power level, diverting a portion of the cathode exhaust flow into the cathode inlet line.

13. The method according to claim 12, wherein controlling the inert gas generation system to generate the inert gas comprises: diverting a portion of the air stream to the inert gas generation system; as well as A portion of the hydrogen is transferred to the catalyst system.

14. The method according to any one of claims 10 to 13, comprising: determining (604) that the fuel cell system is no longer operating at the reduced power demand and that the value of the power output requested from the fuel cell system is greater than the at least one threshold power; in response to determining that the value of the power output is greater than the at least one threshold power, controlling (606) the inert gas generation system to supply the reduced amount of inert gas to the cathode inlet line, controlling the cathode bypass line to divert the reduced amount of cathode exhaust flow to the inert gas generation system or controlling the air flow bypass line to divert the reduced amount of air flow to the inert gas generation system, and controlling the anode bypass path to divert the reduced amount of hydrogen flow to the inert gas generation system; as well as As the value of the power output further decreases, and as the inert gas generation system stops supplying the inert gas to the cathode inlet line, the cathode bypass line is controlled (608) to stop diverting the cathode exhaust flow to the catalyst system and the anode bypass path is controlled to stop diverting the hydrogen flow to the inert gas generation system.

15. A control system (30) for controlling a fuel cell system (20, 20a, 220, 320, 420) of a fuel cell vehicle (10), the control system (30) comprising a processing circuit (32) configured to execute the method according to any one of claims 11 to 14.

Images