High-temperature fuel cell system and its operating method

Abstract

A method is provided for controlling the operation of a PEM fuel cell system (PEMFCS), the PEMFCS comprising a set of one or more PEM fuel cells (PEMFCs), a compressor having one or more compressor stages for supplying a pressurized gaseous oxidant to the cathode side of the PEMFCs, and a controller for controlling the operation of the PEMFCS. The method controls the target power output of the PEMFCS during the operation of the PEMFCS. e The control of the PEMFCS by the controller is performed so that the compressor compresses the gaseous oxidant and provides it to the cathode side of the PEMFC as a function of the PEMFC. Specifically, controlling the PEMFCS involves controlling at least two of the following parameters: the pressure p at which the oxidant is compressed by the compressor, the flow rate r at which the pressurized oxidant is provided to the cathode side of the PEMFC, and the operating temperature T of the PEMFC, so that as the operating temperature T increases, at least one of the following occurs: a corresponding increase in pressure p and a corresponding decrease in the stoichiometric ratio λ of oxidant consumption in the electrochemical reaction with fuel in the PEMFC.

Description

[Technical Field]

[0001] The present invention relates to the field of proton exchange membrane (PEM) fuel cell systems (PEMFCS) comprising one or more PEM fuel cells (PEMFCs). Common use cases of PEMFCS include mobile applications (e.g., to power vehicles such as trucks, buses, or cars) and stationary applications (e.g., as local power plants for one or more buildings or industrial sites or server farms). Specifically, the present invention relates to methods for automatically operating PEMFCS, as well as controllers and PEMFCS configured to operate according to such methods. [Background technology]

[0002] Currently known PEMFCSs typically require relatively low operating temperatures. The temperature of PEMFCSs is limited by two main factors: (i) high temperatures reduce the concentration of the oxidizer and decrease thermal efficiency, and (ii) high temperatures reduce the humidity of the film, which can also reduce thermal efficiency and cause damage.

[0003] Therefore, on the one hand, known PEMFCSs, especially those for mobile applications, are at risk of performance degradation and damage when operating above 80°C. To keep PEMFCSs within such temperature ranges, fairly powerful, and therefore large, cooling devices are usually required, such as radiators with sufficient cooling capacity (and therefore large size) (e.g., in mobile applications). However, there are usually clear limitations on how much the cooling capacity can be increased in a given PEMFCS application. For example, in a vehicle, the forward area available for placing a radiator as a cooling device for the PEMFCS is naturally limited (even in large vehicles such as trucks or buses).

[0004] On the other hand, it is necessary to keep the fuel costs for operating the PEMFCS low, and therefore it is desirable to reduce its fuel consumption (e.g., average fuel consumption, or fuel consumption per unit of power output). Such a reduction in fuel consumption can be achieved if the maximum operating temperature of the PEMFCS can be increased without compromising its efficiency and integrity. This is particularly relevant to high-load vehicles (HDVs), such as long-haul trucks, which must be able to sustain their load even in hot environments such as summer, hot regions, and / or mountainous areas.

[0005] Conventional methods to overcome thermal constraints involve increasing the size of fuel cells and reducing the surface current density. However, this comes with increased installation space requirements for PEMFCS and generally higher costs. In cargo applications in particular, such increased space requirements can lead to a reduction in the cargo capacity available in commercial vehicles (and consequently, increased operating costs). [Overview of the project] [Problems that the invention aims to solve]

[0006] Therefore, an object of the present invention is to define an improved method for extending the usable operating temperature range of a PEMFCS to the higher temperature side, enabling the PEMFCS to operate efficiently and without damage. [Means for solving the problem]

[0007] A solution to this problem is provided by the teachings of the independent claims. Various preferred embodiments of the present invention are provided by the teachings of the dependent claims.

[0008] A first aspect of the present invention relates to a method for controlling the operation of a PEM fuel cell system (PEMFCS), the PEMFCS comprising one or more PEM fuel cells (PEMFCs), a compressor having one or more compressor stages for supplying a pressurized gaseous oxidant such as oxygen (O2) to the cathode side of the PEMFCs, and a controller for controlling the operation of the PEMFCS. The PEMFCs may particularly include a stack having multiple stacked and interconnected PEM fuel cells.

[0009] This method involves adjusting the target power output of the PEMFCS during its operation. e This includes controlling the PEMFCS by a controller so that the compressor compresses the gaseous oxidant and provides it to the cathode side of the PEMFC as a function of the PEMFCS.

[0010] Specifically, controlling PEMFCS involves the following parameters: (a) The pressure p under which the oxidizing agent is compressed by the compressor, (b) The flow rate r of the pressurized oxidizing agent supplied to the cathode side of the PEMFC, and (c) PEMFC operating temperature T, This involves controlling at least two of the following: a corresponding increase in pressure p and a corresponding decrease in the stoichiometric ratio λ of oxidizer consumption in the chemical reaction with fuel such as hydrogen (H2) within the PEMFC, as the operating temperature T increases.

[0011] As used herein, the term “operating temperature” may, in particular, refer to the temperature of the coolant applied to the temperature control of the PEMFC or a part thereof, especially the cooling. Alternatively, the operating temperature may be determined as a (non-identical) function of the coolant temperature in particular. The operating temperature may, in particular, be defined as the average, median, or maximum temperature occurring in the PEMFC or its coolant during the operating period of the PEMFCS under consideration.

[0012] As used in this specification, “target power output”, O eThe term may, in particular, refer to the output current or output power supplied by the PEMFCS during operation.

[0013] As used herein, the term "stoichiometric ratio" refers to the ratio of the actual mass flow rate of reactants in a chemical reaction to the mass consumption rate of those reactants in the chemical reaction. In the present invention, the term "stoichiometric ratio" specifically refers to the ratio of the actual mass flow rate of a gaseous oxidizer in a chemical reaction with a fuel, such as hydrogen (H2), in a PEMFC to the mass consumption rate of that chemical reaction.

[0014] The terms “first,” “second,” “third,” etc., used herein and in the claims are used to distinguish similar elements and are not necessarily used to describe a sequential or chronological order. It should be understood that such terms are interchangeable under appropriate circumstances, and that embodiments of the Solution described herein may operate in other sequences than those described or illustrated herein.

[0015] Unless otherwise required by context, the terms “comprising,” “including,” or their variations “comprises,” “comprise,” or “include,” when used in this description and claims, should be interpreted as “including, but not limiting,” without excluding other elements or steps.

[0016] When an indefinite or definite article, such as "a," "an," or "the," is used to refer to a singular noun, it also includes the plural form of that noun unless otherwise specified.

[0017] Where phrases such as "in some embodiments," "in one embodiment," or "in an embodiment" appear in the description, their occurrences do not necessarily all refer to the same embodiment. Furthermore, certain features, structures, or characteristics can be combined in any preferred manner in one or more embodiments.

[0018] Furthermore, unless explicitly stated otherwise, "or" refers to an inclusive "or," not an exclusive "or." For example, condition A or B is satisfied by any one of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0019] According to this method, an increase in the operating temperature T is accompanied by a corresponding change in at least one other parameter, namely a corresponding increase in the (target) pressure p and / or a corresponding decrease in the (target) stoichiometric ratio λ, regardless of whether it is actively controlled or simply a result of given conditions such as ambient temperature or past or present electrical load of the PEMFCS. In this way, the thermal efficiency of the PEMFCS can be maintained or even further improved despite the increase in the operating temperature T. This is because the change in the pressure p and / or stoichiometric ratio λ (and therefore local mole fraction x) of the oxidizer supplied to the PEMFC also increases, compensating for, or in some cases reversing, the natural negative effect on the oxidizer concentration due to a mere temperature increase.

[0020] Specifically, increasing the pressure p has the effect of suppressing water evaporation, thereby preventing at least one of the following: a reduction in membrane humidity, a decrease in thermal efficiency, and humidity-dependent damage to the membrane.

[0021] On the other hand, if no countermeasures are taken, increasing the pressure p will naturally require more compressor power, which will generate more heat. However, by reducing the stoichiometric ratio λ, it becomes possible to reduce the compressor's power requirements, and while increasing the pressure p, it may be possible to mitigate, or in some cases completely avoid, a significant increase in the associated operating temperature T.

[0022] Therefore, this method provides an improved method for extending the usable operating temperature range of PEMFCS to higher temperatures without compromising the thermal efficiency and integrity of PEMFCS, particularly the integrity of the PEMFC film(s).

[0023] Preferred embodiments of the methods of the first embodiment are described below, which may be optionally combined with each other or with other embodiments of the invention, unless such combination is expressly excluded or technically impossible.

[0024] In some embodiments, the control of the PEMFCS is controlled by the target power output O e The system is configured to control at least two of the parameters as a function of the operating temperature T, such that as the operating temperature T increases, at least one of the following occurs: an increase in pressure p and a decrease in the stoichiometric ratio λ, thereby increasing the ratio (p·x) / T or maintaining it within at least the tolerance d = ±10%. Here, x is the molar concentration of the oxidizing agent in the pressurized oxidizing agent, for example, in the case of air, x = C O2 Therefore, these embodiments are based on using the ratio (p·x) / T, or an equivalent or corresponding quantity, as a control variable of the controller for controlling the operation of the PEMFCS, enabling the effective and efficient implementation of the control scheme performed by the controller.

[0025] In some embodiments, the control of PEMFCS involves adjusting the molar concentration x of the pressurized oxidizing agent to the target power output O e The minimum molar concentration of the oxidizing agent as a function of x minThis involves controlling at least two of the parameters to reduce the pressure rise effect to a certain value. In this way, the compensation specified above for the temperature rise effect due to the pressure rise can be optimized by a simultaneous decrease in the stoichiometric ratio λ (and therefore the molar concentration of the oxidizing agent x). Specifically, x min x can be defined as a function of the electrical output current of the PEMFCS or the associated current density. In the specific embodiments further described below with reference to the figure, the oxidizer is air, and its molar concentration x is instead C O2 It is listed as follows.

[0026] In some embodiments, controlling the PEMFCS involves controlling all parameters such that an increase in operating temperature T is accompanied by a corresponding increase in pressure p and a corresponding decrease in stoichiometric ratio λ. This allows for at least one of highly effective control of the PEMFCS and an optimal extension of the operating range of the PEMFCS to the higher temperature side. This is to mitigate, compensate for, or overcompensate for the effects of an increase in operating temperature, which would normally adversely affect the thermal efficiency and / or integrity of the PEMFCS, by using the maximum number of parameters.

[0027] In some embodiments, at least one of the compressor stages is equipped with a variable nozzle turbine VNT, and controlling the pressure p includes changing the effective aspect ratio of the VNT. Thus, the VNT provides an effective and space-efficient means for changing the pressure p in a controlled manner. The turbine may, in particular, be the exhaust-side turbine of an electric supercharger of at least one compressor stage.

[0028] In some embodiments, controlling the flow rate r involves causing a change in the flow rate of at least one stage of the compressor. In particular, for a centrifugal compressor stage, controlling the flow rate r may involve controlling the rotational speed of the compressor stage. Thus, both the pressure p and the flow rate r may be set by (simply) controlling the operation of the compressor itself.

[0029] In some embodiments, controlling at least two parameters comprises reading, from one or more predetermined look-up tables that together define respective set values of each parameter to be controlled as a function of a target power output O e or as a function of at least one quantity corresponding thereto. This is particularly useful when performance (with respect to processing speed) is important and when one or more pre-defined set value functions can be used without degrading the effectiveness and / or efficiency of the method. Thus, the one or more set value functions that define each respective set value as a function of a related input such as the target power output O e or a quantity derived therefrom can be embodied in one or more look-up tables. Thereby, the output of the set value function becomes very quickly and reliably available from the one or more look-up tables. Further, look-up tables offer the advantage that they can be easily implemented even for functions that cannot be (efficiently or at all) defined closed-form by mathematical formulas. This is particularly useful when the function embodied in the look-up table has been experimentally derived, for example, by measuring a discrete set of a limited number of measurement points, rather than from some kind of mathematical calculation.

[0030] In some embodiments, the method further comprises determining a target power output O e , and determining O e comprises (i) measuring O e , (ii) measuring at least one quantity corresponding to O e and deriving O e based on such measured one or more quantities, (iii) receiving information representing at least one quantity corresponding to O e from an external information source of the PEMFCS and deriving O eThis includes determining at least one of the following: (i) and (ii), the method, or more specifically, the PEM fuel cell system implementing the method, becomes largely autonomous, while in case (iii), the method can utilize information acquired elsewhere, for example, information acquired by one or more sensors located elsewhere, sometimes for other purposes, in a system or device (e.g., a vehicle) driven by the fuel cell system, and in such dual-use situations, improved efficiency can be achieved in terms of saving space and / or cost.

[0031] In some embodiments, the PEMFCS is applied to power a vehicle engine, and the method is applied to control the PEMFCS while the electric vehicle engine is powered, at least partially, by electricity generated by the PEMFCS. This is particularly useful to cover operating conditions in which the power demand by a vehicle, including an electric engine, becomes very high and is accompanied by considerable high temperatures. Such conditions can occur, for example, when a vehicle (e.g., a heavy-duty truck) is traveling on mountain roads in high ambient temperatures, for example, in hot desert areas (such as the southwestern United States) or on hot summer days.

[0032] A second aspect of the present invention relates to a PEM fuel cell system (PEMFCS), which includes (1) a set of one or more PEM fuel cells (PEMFCs), (ii) a compressor having one or more compressor stages for supplying a pressurized gaseous oxidant such as oxygen to the cathode side of the PEMFCs, and (iii) a controller for controlling the operation of the PEMFCS. In this specification, the controller is configured to control the PEMFCS according to the method of the first aspect, for example, according to one or more of its embodiments described herein.

[0033] PEM fuel can be supplied, in particular, as a component of fuel cell stacks arranged in a stacked configuration. PEM fuel cell stacks are a well-known concept for arranging multiple, often hundreds, PEM fuel cells in a highly space-efficient manner and are used, for example, in the field of fuel cells for automotive applications.

[0034] The term "controller," as used herein, refers to any functional unit or set of functional units configured to control the operation of a PEMFCS, in particular, in whole or in part, in order to perform tasks related to the controller. Specifically, a controller may comprise one or more physical devices. For example, one or more of these devices may be implemented as hardware circuits including custom VLSI circuits or commercially available semiconductors such as gate arrays, logic chips, transistors, or other discrete components. Devices may also be implemented as programmable hardware devices such as field-programmable gate arrays, programmable array logic, or programmable logic means. A controller may also be implemented in software, at least in part, for execution by various types of processors. An identified device of executable code may include one or more physical or logical blocks of computer instructions, which may be configured, for example, as objects, procedures, or functions. However, the executable code of a particular device does not need to be physically located in the same place and may include different instructions stored in different locations. These instructions, when logically combined, constitute the device and achieve a predetermined purpose of the device. In fact, a device of executable code can be a single instruction, many instructions, or even distributed across several different code segments, different programs, and several memory means. Similarly, operational data may be identified and represented within a device as herein, materialized in any appropriate form, and organized within any appropriate type of data structure. Operational data may be collected as a single dataset or distributed across different locations, including different storage devices.

[0035] Preferred embodiments of the PEMFCS of the second embodiment are described below, which may be optionally combined with each other or with other embodiments of the invention, unless such combination is expressly excluded or technically impossible.

[0036] In some embodiments, the PEMFCS further comprises one or more temperature control devices (such as one or more radiators or other cooling devices, thermal heat pumps, or heaters) for regulating the temperature of the coolant flowing through the PEMFC. Thus, the temperature of the PEMFC can be actively influenced, particularly under the control of the controller, to bring the PEMFC to an optimal operating state or range of operating states, or to support maintaining them. Therefore, at least one of the temperature control devices may be controllable by the controller to control the above operating temperature of the PEMFC.

[0037] In some embodiments, at least one of the compressor stages includes one or more pressure-variating devices for changing the pressure p under the control of a controller. In this way, the pressure p is controlled in particular to the target power output O e For example, the pressure can be controlled to or maintained at a desired, particularly optimal, pressure level, as a function of the target output current.

[0038] In some embodiments, at least one of the pressure fluctuation devices includes a pressure control valve. This valve may, in particular, be located in the exhaust passage (e.g., for air) of the PEMFCS. Thus, under the control of a controller, the pressure p can be controlled using the valve.

[0039] In some embodiments, at least one of the pressure fluctuation devices comprises a variable nozzle turbine VNT, the effective aspect ratio of which is controllable by a controller. Specifically, the VNT can be used in place of, or in combination with, the above-mentioned pressure control valve to control pressure p. The VNT is a very effective pressure control device and can, in some cases, be well controlled even by a single actuator using the corresponding control signal provided by the controller.

[0040] In some embodiments, at least one of the compressor stages is equipped with an electric supercharger controllable by a controller. This allows for extremely efficient (and particularly energy-efficient) pressurization of the oxidizer, such as air.

[0041] Specifically, in some of these embodiments, the electric supercharger includes a VNT. In this way, a highly efficient pressure fluctuation device can be achieved that is very compact. For example, the VNT may be part of the turbine side of the electric supercharger, or it may define the turbine side.

[0042] In some embodiments, the PEM fuel cell system further comprises a set of one or more sensors for measuring one or more of the following quantities: (i) the operating temperature T of the PEMFC (e.g., as the temperature of the coolant for temperature-conditioning the PEMFC), (ii) the flow rate Q of the oxidizer before compression by the compressor, (iii) the input pressure P of the oxidizer before compression by the compressor, and (iv) the current I generated by the PEMFC. Hereinafter, the controller is configured to control the PEMFC based on at least one of these quantities measured by the set of sensors. These embodiments are particularly useful for implementing the PEMFC as a large-scale autonomous system that can optimize the operation of the PEMFC under the control of the controller with little to no need for sensor data generated elsewhere.

[0043] In some embodiments, the controller is configured to control the speed of an actuator, such as a motor, that drives at least one of the compressor stages. Thus, since the pressure generated in each compressor stage is a function of speed, the controller can control the output pressure of each compressor stage.

[0044] In some embodiments, the PEMFCS further comprises a humidifier configured to humidify the oxidizer after compression by at least one (e.g., all) of the compressor stages. Thus, the humidifier may be located particularly downstream of the compressor and upstream of the PEMFC. The role of the humidifier is, in particular, to maintain the humidity of the oxidizer within a suitable humidity range, because if the humidity is too low, this can cause an increase in the ohmic resistance of the PEMFC and, consequently, a reduction in thermal efficiency.

[0045] When a humidifier is equipped with a gas-to-gas humidity exchanger, this is particularly relevant to rising temperatures and high temperatures. Such an exchange device allows cathode process air to pass through a gas-permeable membrane. Water vapor from the cathode outlet gas can diffuse through the membrane and humidify the cathode inlet gas. When the temperature rises in such a humidifier, the water vapor concentration in the PEMFC outlet gas typically decreases.

[0046] If the temperature rises too high and the humidity of the cathode inlet gas approaches a critical low level, the pressure p must be increased to compensate for this in order to maintain a sufficiently high level of thermal efficiency and prevent damage to the membrane.

[0047] A third aspect of the present invention relates to a controller for controlling the operation of a PEM fuel cell system (PEMFCS), the PEMFCS comprising a set of one or more PEM fuel cells (PEMFCs) and a compressor having one or more compressor stages for supplying a pressurized gaseous oxidant such as oxygen to the cathode side of the PEMFCs, and the control device is configured to control the PEMFCS according to the method of the first aspect.

[0048] A fourth aspect of the present invention relates to a computer program, in particular to a computer-readable storage medium on which the computer program is stored or is a non-temporary computer, the computer program including instructions, which, when executed by a controller of a PEM fuel cell system of the second aspect, cause the controller to perform the method of the first aspect.

[0049] The features and advantages described in relation to the first aspect of the present invention also apply to further aspects of the present invention.

[0050] The method according to the first embodiment is preferably configured to be implemented by a controller according to the second embodiment, or a PEMFCS (particularly its controller) according to the third embodiment, in particular as described herein.

[0051] A computer program (product) may be implemented, in particular, in the form of a data carrier in which one or more programs for performing a method are stored. Preferably, this is a data carrier such as a ROM or flash memory module. This may be advantageous if the computer program product is intended to be traded as a separate product independent of the processor platform on which the one or more programs are executed. In another embodiment, the computer program product is provided as a file on a data processing unit, in particular a server, and can be downloaded via a data connection, such as the Internet or a dedicated data connection such as a private network or local area network.

[0052] Therefore, the controller of the second embodiment and / or the PEMFCS of the third embodiment may each have program memory in which a computer program is stored. Alternatively, the system may also be configured to access, via a communication link, computer programs located externally, for example, on one or more external storage devices or on one or more servers or other data processing units, in particular for exchanging data used in the execution process of the computer programs or data representing the output of the computer programs.

[0053] Further advantages, features, and applications of the present invention are provided in the following detailed description and accompanying figures. [Brief explanation of the drawing]

[0054] [Figure 1A] A block diagram illustrating an exemplary embodiment of the method according to the first aspect is shown. [Figure 1B] An exemplary embodiment of a setting map for three of the setting values ​​defined by method 1A is shown. [Figure 1C] An exemplary embodiment of a setting map for three of the setting values ​​defined by method 1A is shown. [Figure 1D] An exemplary embodiment of a setting map for three of the setting values ​​defined by method 1A is shown. [Figure 2] This is a block diagram showing the first embodiment of PEMFCS. [Figure 3] This is a block diagram showing a second embodiment of PEMFCS. [Figure 4] This is a block diagram showing a third embodiment of PEMFCS. [Modes for carrying out the invention]

[0055] In these figures, the same reference numerals are used for the same or corresponding elements of the methods described herein and of the PEMFCS.

[0056] Figure 1A shows a block diagram illustrating an exemplary embodiment of method 100 for controlling the operation of a PEM fuel cell system (PEMFCS). Various embodiments of such PEMFCS are shown in Figures 2, 3, and 4. Hereafter, method 100 will be described with reference to Figures 1A to 1D in combination with the PEMFCS 200 shown in Figure 2, but any of the other embodiments of the PEMFCS provided herein, for example, any of the embodiments in Figures 3 and 4, may be referred to instead of the embodiment in Figure 2.

[0057] Referring first to Figure 2, the PEMFCS200 shown herein comprises a set (PEMFC)205 (e.g., a fuel cell stack) containing one or more PEM fuel cells, and a compressor having a first compressor stage 215 and a second compressor stage 220 (usually electric). The compressor is supplied with a gaseous oxidizer such as air at its inlet A in It receives the oxidizer and a pressurized flow AH at its outlet. in It is configured to generate and provide to the cathode side of the PEMFC205. In this embodiment, the second compressor stage 220 comprises an electric supercharger with a compressor wheel 220a and a turbine 220b. This electric supercharger is of the variable nozzle turbine (VNT) type, and the effective aspect ratio of its turbine 220b can be changed. Thus, the combination of stage 215 and stage 220 forms a VNT type two-stage electric supercharger (ETC). The PEMFCS200 further comprises a controller 230 for controlling the operation of the PEMFCS200. Such control includes, in particular, controlling the effective aspect ratio of the VNT turbine 220b and the rotational speed of at least the first stage 215 (and optionally further the second stage 220) via one or more actuators. Specifically, a control signal X can be used to control the effective aspect ratio of the VNT turbine 220b, and another control signal M can be used to control the speed(s) of each of the compressor stages(s). Furthermore, on the supply side of PEMFCS200, the inflow stream A of the gaseous oxidizer in A flow sensor may be provided to measure the flow rate Q.

[0058] Furthermore, the PEMFCS200 further includes a temperature control device 210 (or is alternatively connected to an external PEMFCS temperature control device). For example, in the case of a PEMFCS, particularly for automotive applications (such as powering a truck), the temperature control device 210 may include a radiator (e.g., the truck's main radiator). The coolant circulates through the PEMFCS205, in particular through each of its fuel cells in appropriate channels, and through the temperature control device. In particular, during the operation of the PEMFCS200, the flow of cold coolant C in The fluid flows from the temperature control device 210 (in this case, a cooling device, e.g., a radiator) to the PEMFC 205, where it absorbs the heat generated in the fuel cell, and then the return flow C out The heat is then returned to the temperature control device 210, thereby transporting heat from the PEMFC 205 to the temperature control device 210 for cooling.

[0059] The temperature sensor for measuring the temperature T of the PEMFC205 is in thermal contact with the coolant, for example, the flow C. in It is positioned to be in thermal contact with the other. In the latter case, temperature T corresponds to the temperature on the outlet side of the PEMFC205.

[0060] The PEMFC205 is equipped with a fuel inlet (not shown) for receiving fuel such as molecular hydrogen (H2) and supplying it to the anode side of the fuel cell of the PEMFC205. Furthermore, the PEMFC205 is equipped with a gaseous oxidizer flow FC such as air or a gas containing a higher percentage of oxygen (O2). in It includes a further inlet for receiving. Inside the fuel cell, the fuel chemically reacts with the oxidizer to generate electrical energy. When the PEMFC205 is connected to an electrical circuit, such as an electric engine, the current I generated by the PEMFC205 flows and can be measured by a suitable sensor, such as an ammeter.

[0061] At the outlet of the cathode-side PEMFC205, the return flow of (unconsumed) gaseous oxidizer is AFC. out The gas is discharged from the PEMFC205, and the return flow is AFC. outA suitable pressure sensor is provided to measure the pressure P.

[0062] The PEMFCS200 may further include a humidifier 225. Specifically, as shown in the figure, a gas flow AFC in and AFC out Both can be positioned to pass through it. Humidifier 225 receives the incoming gas flow AH from the compressor. in Humidify the humidified gas flow AFC in This ensures sufficiently high humidity in the PEM fuel cell membrane, and also facilitates gas flow AFC. in To capture moisture that is reused on the inlet side for humidification, the outlet gas flow AFC out Dehumidify the gas flow at the cathode outlet of the PEMFC205. Specifically, AFC out The humidity can be targeted to be close to 100% relative humidity (RH). This range can vary, particularly within the RH range of 80% to 120%. Dehumidified effluent gas flow AH out To achieve high effectiveness of the humidifier 225, it reaches the turbine 220b and drives the turbine 220b, ultimately leading to exhaust flow A out Gas flow AH when discharged as out Aim for a much lower RH to keep it low enough to reduce humidity condensation.

[0063] Optionally, the temperature control device 210 may have variable temperature control capabilities, such as a variable cooling capacity controllable by the controller 230 via a control signal R. Thus, the temperature T may be affected via the control signal R. For example, the cooling capacity of the temperature control device 210 can be increased using the control signal R to keep T below the temperature limit until the measured value of T increases and approaches or reaches a level that defines the upper limit of the operating range of the PEMFC 205.

[0064] All measurements taken by various sensors are provided to the controller 230 in the form of sensor data, and the controller 230 is configured to process the sensor data, for example, by one or more suitable computer programs, and derive control signals from it to control the operation of the PEMFCS200. Specifically, such control signals include control signals X and M for controlling the operation of a two-stage VNT type supercharger.

[0065] Here again, with reference to Figure 1A, the method 100 for controlling the PEMFCS200 will be described in more detail. This method includes receiving various inputs, in particular, the current or at least the most recent values ​​of the measured temperature T, pressure P, and flow rate Q.

[0066] Further input is the target power output O e In this embodiment, the target power output O e This is the target electrical output current I provided by the PEMFCS200, such as the current requested via throttle control by the driver of a vehicle powered by the PEMFCS200. Alternatively, it is the target power output O. e This can be set to be equal to the measured current that PEMFC205 can currently provide with a given flow rate Q. Controller 230 processes all of these inputs and derives a control signal from them to control PEMFCS200, and PEMFCS200 sets the target power output O e The aim is to approach this and (if possible) achieve it. Specifically, the fuel supply rate on the anode side may be controlled for this purpose. Furthermore, as will be described in more detail below, via control signals X and M, the controller 230 also controls the molar concentration and supply flow rate (flow rate) of the oxidizer on the cathode side of the PEMFC205 for this purpose.

[0067] The processing performed by the controller 230 includes calculating several setting values.

[0068] Specifically, the first process 105 includes determining the target pressure p of the gaseous oxidizer as a function p(I,T) of input quantities I and T. The determined target pressure p is set to a first set value S p Defines the outflow AFC out This may be related to the pressure. The actual pressure P is also measured. Set value S p A comparison 110 (for example, by a comparison device in the controller 230) is performed between the measured value P and the actual pressure, and from there a further set value S is determined, i.e., a set value that affects the actual pressure. x This is derived. In this embodiment, it is derived by controlling the effective aspect ratio of the turbine 220b of the VNT type ETC. Therefore, the control signal X is the determined set value S x It may be defined to be equal to, or otherwise correspond to, and as a result of applying the control signal X to the actuator(s) that affect the effective aspect ratio of turbine 220b, the set value S x The actual effective aspect ratio is reached, determined by [the specified factor].

[0069] Figure 1B shows an exemplary pressure setpoint map for determining the target pressure p as a function of temperature T and for three different values ​​of current I, for an exemplary fuel cell design. Thus, the cathode outlet pressure value p (and similarly P) may have the following characteristics, in particular: The cathode outlet pressure is higher than 100 kPa and lower than 350 kPa. The cathode outlet pressure is constant or increases with temperature T and current I. The cathode pressure fluctuation with temperature T is not directly proportional to the change in gas density.

[0070] Referring again to Figure 1A, the further process 115 involves the target molar concentration C of the gaseous oxidizer. O2 (In this embodiment, the concentration of O2 in the air) is a function of the current density j = I / A, which is related to the input quantity I and the area A of the current path of I. O2 This includes determining the target molar concentration C as (j). O2 This is a different setting value S C This defines the outflow AFC at the cathode-side outlet, in particular. out Molar concentration CO2 This may be related.

[0071] Figure 1C shows the target molar concentration C for an exemplary fuel cell design. O2 An exemplary molar concentration setpoint map for determining (j) is shown. O2 (j) may have the following characteristics in particular: C O2 (j) is defined as the Reynold number Re of the cathode channel being greater than 80 (Re>80) and / or the current density j>0.5A / cm². 2 The operating range is at least substantially proportional to the current density j. The slope is particularly pronounced for 2-4 mol m -3 cm 2 A -1 It could be within the range of.

[0072] Referring again to Figure 1A, further process 120 includes determining the target stoichiometric ratio λ of the oxidizer consumption in the electrochemical reaction with the fuel within the PEMFC205. The stoichiometric target ratio λ is given by the function λ(p, T, C O2 ) as, that is, the molar concentration C determined by the target pressure p, temperature T, and process 115. O2 It is determined as a function of (j). Specifically, λ can be calculated as follows using the molar gas constant R and the water crossover fitting parameter K of the MEA.

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[0073] Therefore, the output of process 120 is yet another setting value S λ We define =λ, and in particular, the inflow AH at the cathode-side inlet. in or AFC in This may be related to the stoichiometric ratio.

[0074] Figure 1D shows the target stoichiometric ratio S as a function of T, and for three different values ​​of current I. λAn exemplary stoichiometric ratio setting map for determining λ is shown. The cathode stoichiometric value λ may have the following properties in particular: λ is greater than 1 and decreases as pressure and temperature increase. At a given temperature T, λ increases with increasing current I.

[0075] Referring again to Figure 1A, a further process 125 includes determining the target flow rate.

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[0076] The determined target flow rate r is, in this specification, the mass flow rate.

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[0077] Referring again to Figure 1A, the further process 130 involves yet another setting value S M That is, the measured flow rate Q and the determined setpoint S m Function S M (Q,S m Process 130 includes determining the target flow rate of the gaseous oxidizer at the compressor outlet. m This includes a comparison between the measured value Q and the set value S (for example, by a comparison device in the controller 230), from which the set value S is obtained. M This leads to the conclusion that the control signal M is equal to the determined setpoint S. M It can be defined to be equal to or corresponding to. As a result of applying the control signal M to the actuator(s) (e.g., the electric drive(s) of the compressor(s)), the flow AH at the compressor outlet is inThe actual flow rate can reach the value determined by the set value SM.

[0078] Therefore, controlling the PEMFCS200 using method 100 requires the following parameters: (a) The oxidizer is compressed by the compressor 215 / 220 at pressure p, (b) Flow rate r (for example, the mass flow rate at which the pressurized oxidizer is supplied to the cathode side of the PEMFC205), (c) PEMFC205 operating temperature T, This involves controlling at least two of the following: a corresponding increase in pressure p and a corresponding decrease in the stoichiometric ratio λ of oxidizer consumption in the electrochemical reaction with fuel such as hydrogen (H2) in the PEMFC205, as the operating temperature T increases.

[0079] Figure 3 is a block diagram of a second embodiment 300 of the PEMFCS. This has a large resemblance to the first embodiment 200 (and is therefore not described again here), but differs in the following respects: The compressor 220 includes an electric supercharger (ETC) configured such that the compressor wheel 220a functions as a first compressor stage and the turbine 220b downstream thereof functions as a second compressor stage (rather than acting as a conventional turbo turbine in the exhaust passage). The speed of the compressor 220 is controlled by a controller via a control signal M. Furthermore, a pressure control valve 235 is located in the outflow (exhaust passage) and is configured to be controlled by a controller 230 via a control signal X to change the actual pressure P toward a target pressure p.

[0080] Figure 4 is a block diagram of a third embodiment 400 of the PEMFCS. This also has significant similarities to the first embodiment 200 (and is therefore not described again here), but differs in the following respects: The compressor 220 includes an electric supercharger (ETC) configured such that the compressor wheel 220a functions as the first compressor stage and the turbine 220b functions as a turbo turbine, which is its normal role in the exhaust passage. The speed of the compressor 220 is controlled by a controller via a control signal M. Furthermore, a pressure control valve 235 is located in the outflow (exhaust passage) between the humidifier 225 and the turbine 220b and is configured to be controlled by a controller 230 via a control signal X to change the actual pressure P toward a target pressure p.

[0081] While at least one exemplary embodiment of the present invention has been described above, it should be noted that numerous modifications exist thereto. Furthermore, it should be understood that the described exemplary embodiments merely illustrate non-limiting examples of how the present invention can be carried out and are not intended to limit the scope, applications, or configurations of the apparatus and methods described herein. Rather, the foregoing description provides a configuration for carrying out at least one exemplary embodiment of the present invention to those skilled in the art, and it should be understood that various modifications can be made to the function and arrangement of components of the exemplary embodiment without departing from the scope of the invention as defined by the appended claims. [Explanation of Symbols]

[0082] 100 How to control the operation of PEMFCS 105 Process for determining the target pressure setting 110 Process for determining actuator setpoints that affect actual pressure 115 Process for determining the target molar concentration setting 120 Process for determining the target stoichiometric ratio 125 Process for determining the target flow rate 130 Process for determining actuator settings that affect actual flow rate First Embodiment of 200 PEMFCS 205 PEM Fuel Cell (PEMFC) Set 210 Temperature control devices (e.g., radiators) 215 First compressor stage 220 Electric Supercharger (ETC) (especially as a second compressor stage) 220a Compressor Wheel 220b Turbine (e.g., VNT) 225 Humidifier 230 Controllers 235 Pressure control valve Second embodiment of 300 PEMFCS Third Embodiment of 400 PEMFCS Effective cross-sectional area for determining current density j from AI A in The flow of oxidizer from the inlet to the compressor A out Oxidizer flow from PEMFCS (in the exhaust passage) AFC in Flow of oxidizing agent from humidifier to PEMFC AFC out Oxidizing agent flow from PEMFC to humidifier AH in Flow of oxidizing agent from compressor to humidifier AH out Flow of oxidizing agent from the humidifier towards the exhaust passage C is a constant in the equation for the stoichiometric ratio λ. C in Coolant flow from temperature control device to PEMFC C out Coolant flow from PEMFC to temperature control unit C O2 Molar concentration of oxidizing agent η humidifier Humidifier steam exchange efficiency F is Faraday's constant, F = 96495 C / mol I. Target current (or currently possible current as measured) I 1,…, I3 Current Value Current density corresponding to current I Fitting parameter regarding water crossover of K MEA λ Stoichiometric ratio

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Claims

1. A method (100) for controlling the operation of a PEM fuel cell system (PEMFCS, 200, 300, 400), wherein the PEMFCS (200, 300, 400) includes a set (205) of one or more PEM fuel cells (PEMFCs), a compressor having one or more compressor stages (215, 220) for supplying a pressurized gaseous oxidant to the cathode side (205) of the PEMFCs, and a controller (230) for controlling the operation of the PEMFCS (200, 300, 400), wherein the method (100) is: During the operation of the PEMFCS (200, 300, 400), the target power output of the PEMFCS (200, 300, 400) ｅ The control of the PEMFCS(200, 300, 400) by the controller (230) is a function of the compressor compressing the gaseous oxidizer and supplying it to the cathode side (205) of the PEMFC, and the control of the PEMFCS(200, 300, 400) is a function of the following parameters: (a) The pressure p at which the oxidizing agent is compressed by the compressor, (b) The flow rate r of the pressurized oxidizing agent supplied to the cathode side of the PEMFC (205), and (c) Operating temperature T of the PEMFC (205) The method (100), comprising controlling at least two of the following, such that as the operating temperature T increases, at least one of the following occurs: a corresponding increase in the pressure p and a corresponding decrease in the stoichiometric ratio λ of the consumption of the oxidizer in the electrochemical reaction with the fuel in the PEMFC.

2. Controlling the PEMFCS (200, 300, 400) is equivalent to controlling the target power output O ｅ The method according to claim 1 (100), comprising controlling at least two of the parameters as a function of such that, as the operating temperature T increases, at least one of the following occurs: an increase in pressure p and a decrease in the stoichiometric ratio λ, thereby increasing the ratio (p・x) / T or maintaining it within at least the tolerance range M = ±10%, where x is the molar concentration x of the pressurized oxidizing agent.

3. Controlling the PEMFCS (200, 300, 400) controls the molar concentration x of the pressurized oxidizing agent, and the target power output O ｅ The method according to any one of the prior claims (100), comprising controlling at least two of the parameters to reduce the oxidizing agent molar concentration to a minimum that is a function of .

4. The method according to any one of the prior claims (100), wherein controlling the PEMFCS (200, 300, 400) includes controlling all of the parameters such that an increase in the operating temperature T is accompanied by a corresponding increase in the pressure p and a corresponding decrease in the stoichiometric ratio λ.

5. The method according to any one of the prior claims (100), wherein at least one of the compressor stages (220) comprises a variable nozzle turbine (VNT, 220b), and controlling the pressure p includes changing the effective aspect ratio of the VNT (220b).

6. The method according to any one of the prior claims (100), wherein controlling the flow rate r includes causing a change in the flow rate of at least one stage of the compressor.

7. Controlling the at least two parameters means that the set value of each parameter to be controlled is set to the target power output O ｅ The method according to any one of the prior claims (100), comprising reading from one or more predetermined lookup tables that define such setting values ​​together as a function of or as a function of at least one corresponding quantity.

8. The target power output O ｅ This further includes determining, where O ｅ To decide is O ｅ To measure, O ｅ measuring at least one quantity corresponding to O, and deriving O based on one or more such measured quantities ｅ therefrom From PEMFCS external information sources O ｅ It receives information representing at least one quantity corresponding to and based on the received information O ｅ To determine, The method according to any one of the prior claims (100), comprising at least one of the above.

9. The method (100) of any one of the prior claims, wherein the PEMFCS (200, 300, 400) is applied to supply power to an electric vehicle engine, and the method (100) is applied to control the PEMFCS (200, 300, 400) during the operation of the electric vehicle engine while the electric vehicle engine is at least partially powered by electricity generated by the PEMFCS (200, 300, 400).

10. A controller (230) for controlling the operation of a PEM fuel cell system (PEMFCS, 200, 300, 400), wherein the PEMFCS (200, 300, 400) includes a set (205) of one or more PEM fuel cells (PEMFCs) and a compressor having one or more compressor stages (215, 220) for supplying a pressurized gaseous oxidant to the cathode side of the PEMFCs (205), and the controller (230) is configured to control the PEMFCS (200, 300, 400) according to the method (100) of any one of the prior claims.

11. A PEM fuel cell system (PEMFCS, 200, 300, 400), wherein the PEMFCS is A set of one or more PEM fuel cells (PEMFCs) (205), A compressor having one or more compressor stages (215, 220) for supplying a pressurized gaseous oxidant to the cathode side of the PEMFC (205), The system includes a controller (230) for controlling the operation of the PEMFCS (200, 300, 400), The PEM fuel cell system, wherein the controller (230) is configured to control the PEM FCS (200, 300, 400) according to the method (100) of any one of claims 1 to 10.

12. The PEM fuel cell system (200, 300, 400) according to claim 11, further comprising one or more temperature control devices (210) for adjusting the temperature of the coolant flowing through the PEMFC (205).

13. The PEM fuel cell system (200, 300, 400) according to claim 12, wherein at least one of the temperature control devices (210) is controllable by the controller (230) to control the operating temperature of the PEMFC (205).

14. The PEM fuel cell system (200) according to any one of claims 11 to 13, wherein one or more of the compressor stages (215, 220) are provided with at least one pressure fluctuation device for changing the pressure p under the control of the controller (230).

15. The PEM fuel cell system (300, 400) according to claim 14, wherein at least one of the pressure fluctuation devices is a pressure control valve (235).

16. The PEM fuel cell system (200) according to claim 14 or 15, wherein at least one of the pressure fluctuation devices comprises a variable nozzle turbine (VNT, 220b), the effective aspect ratio of which is controllable by the controller (230).

17. The PEM fuel cell system (200, 300, 400) according to any one of claims 11 to 16, wherein at least one of the compressor stages (215, 220) is an electric supercharger controllable by the controller (230).

18. The PEM fuel cell system (200) according to claims 16 and 17, wherein the electric supercharger comprises the VNT (220b).

19. The PEM fuel cell system (200, 300, 400), wherein the following quantities: The operating temperature T of the aforementioned PEMFCS (200, 300, 400) The flow rate Q of the oxidizing agent before compression by the compressor, The input pressure P of the oxidizer before compression by the compressor, The current generated by the PEMFC (205), It further comprises a set of one or more sensors for measuring one or more of the following: The PEM fuel cell system (200, 300, 400) according to any one of claims 11 to 18, wherein the controller (230) is configured to control the PEMFC (205) based on at least one of the quantities measured by the set of sensors.

20. The PEM fuel cell system (200, 300, 400) according to any one of claims 11 to 19, wherein the controller (230) is configured to control the speed of an actuator that drives at least one of the compressor stages (215, 220).

21. The PEM fuel cell system (200, 300, 400) according to any one of claims 11 to 20, further comprising a humidifier (225) configured to humidify the oxidizer after it has been compressed by at least one of the compressor stages (215, 220).

22. A computer program, in particular a computer-readable storage medium on which the computer program is stored or a non-temporary computer, wherein the computer program includes instructions, which, when executed by the controller (230) of a PEM fuel cell system (200, 300, 400) according to any one of claims 11 to 21, cause the controller (230) to execute the method (100) according to any one of claims 1 to 9.

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