Fuel cell system

Abstract

The present invention relates to a fuel cell system comprising: a fuel cell stack comprising at least one fuel cell unit; a magnetic field forming unit that variably forms a magnetic field between the anode and the cathode of the at least one fuel cell; and a controller that, when the magnetic field is formed, selectively controls the direction of the magnetic field to any one of a first direction that faces the anode side from the cathode side and a second direction that faces the cathode side from the anode side.

Description

TECHNICAL FIELD

[0001] The present application relates to a fuel cell system capable of adjusting electrochemical reactivity and water discharge of a fuel cell by a magnetic field. BACKGROUND

[0002] A fuel cell converts chemical energy into electric energy using the oxidation-reduction reaction of hydrogen and oxygen supplied from a hydrogen supply device and an air supply device, and includes a fuel cell stack that generates electric energy and a cooling system for cooling the same.

[0003] That is, hydrogen is supplied to the anode side of the fuel cell stack, and the oxidation reaction of hydrogen is performed at the anode to generate hydrogen ions and electrons, and at this time, the generated hydrogen ions and electrons move to the cathode through an electrolyte membrane and a separator, respectively. At the cathode, water is generated through an electrochemical reaction involving hydrogen ions and electrons moved from the anode and oxygen in the air, and electric energy is generated from the flow of such electrons.

[0004] On the other hand, the electrochemical reaction as described above needs to be adjusted according to the state or control conditions of the fuel cell, the operating environment, etc. Likewise, the discharge of water generated through the electrochemical reaction also needs to be adjusted considering various factors.

[0005] Therefore, there is a need to propose a scheme capable of adjusting the electrochemical reactivity and water discharge of a fuel cell according to needs.

[0006] The above-described contents explained as background art are for the purpose of facilitating the understanding of the background of the present application, and should not be regarded as acknowledging that it belongs to the prior art known to those skilled in the art. SUMMARY

[0007] The object of the present application is to provide a fuel cell system capable of optimizing the operation of a fuel cell according to needs in various situations by adjusting the electrochemical reactivity and water discharge of the fuel cell by a magnetic field.

[0008] The technical problems of the present application are not limited to the above-mentioned technical problems, and those skilled in the art can further understand other technical problems that the present application can solve from the following contents.

[0009] A fuel cell system according to an embodiment of the present application for achieving the above-described object includes: a fuel cell stack including at least one fuel cell unit having an anode and a cathode; a magnetic field forming portion provided to the fuel cell stack and variably forming a magnetic field between the anode and the cathode of the at least one fuel cell unit; and a controller selectively controlling a magnetic field direction to either one of a first direction from the cathode side toward the anode side and a second direction from the anode side toward the cathode side when the magnetic field is formed by the magnetic field forming portion.

[0010] For example, the controller can be configured to control the magnetic field direction based on at least one of an amount of electricity of a battery connected to the fuel cell stack and a required output of the fuel cell stack.

[0011] For example, the controller can be configured to perform at least one of promotion control that controls the magnetic field direction to the first direction when the amount of electricity of the battery is below a preset lower limit amount of electricity and suppression control that controls the magnetic field direction to the second direction when the amount of electricity of the battery exceeds a preset upper limit amount of electricity.

[0012] For example, the controller can be configured to control the magnetic field direction based on a moisture state of the fuel cell stack when the amount of electricity of the battery is above the lower limit amount of electricity and below the upper limit amount of electricity, the moisture state including a flooded state and a dry state.

[0013] For example, the controller can be configured to perform the promotion control that controls the magnetic field direction to the first direction when a change amount per unit time of the required output of the fuel cell stack exceeds a preset change amount increase threshold value, the preset change amount increase threshold value being a positive number.

[0014] For example, the controller can be configured to control the magnetic field direction based on a stack voltage of the fuel cell stack and a preset upper limit voltage when the change amount per unit time of the required output of the fuel cell stack is below a preset change amount decrease threshold value, the preset change amount decrease threshold value being a negative number.

[0015] For example, the controller can be configured to perform the suppression control that controls the magnetic field direction to the second direction when the stack voltage of the fuel cell stack exceeds the upper limit voltage.

[0016] For example, the controller can be configured to control the magnetic field direction based on a moisture state of the fuel cell stack when the stack voltage of the fuel cell stack is below the upper limit voltage, the moisture state including a flooded state and a dry state.

[0017] For example, the controller can be configured to control the magnetic field direction based on a moisture state of the fuel cell stack, the moisture state including a flooded state and a dry state, if a change amount per unit time of the required output of the fuel cell stack is below a preset change amount increase threshold value and above a preset change amount decrease threshold value, the preset change amount increase threshold value being a positive number, and the preset change amount decrease threshold value being a negative number.

[0018] For example, the controller can be configured to perform at least one of suppression control and promotion control, the suppression control being control performed so that the magnetic field direction is the second direction when the moisture state of the fuel cell stack is the dry state, and the promotion control being control performed so that the magnetic field direction is the first direction when the moisture state of the fuel cell stack is the flooded state.

[0019] For example, the fuel cell stack can include a first sub-stack including a portion of the at least one fuel cell unit and a second sub-stack including: a remaining portion of the at least one fuel cell unit; the magnetic field forming portion can be configured to form the magnetic field independently for the fuel cell unit included in the first sub-stack and the fuel cell unit included in the second sub-stack, respectively; and the controller can be configured to control the magnetic field direction of the first sub-stack and the second sub-stack based on a temperature difference between the first sub-stack and the second sub-stack.

[0020] For example, the controller can be configured to control the magnetic field direction of either one of the first sub-stack and the second sub-stack when the temperature difference between the first sub-stack and the second sub-stack exceeds a preset reference temperature difference.

[0021] For example, the controller can be configured to perform the suppression control so that the magnetic field direction of the sub-stack having a relatively lower temperature among the first sub-stack and the second sub-stack is the second direction when the temperature difference between the first sub-stack and the second sub-stack exceeds the preset reference temperature difference and the moisture state of the fuel cell stack is the dry state.

[0022] For example, the controller can be configured to perform the promotion control so that the magnetic field direction of the sub-stack having a relatively higher temperature among the first sub-stack and the second sub-stack is the first direction when the temperature difference between the first sub-stack and the second sub-stack exceeds the preset reference temperature difference and the moisture state of the fuel cell stack is the flooded state.

[0023] For example, the controller can be configured to determine whether the dry state exists based on a voltage deviation between the fuel cell units of the fuel cell stack being below a preset reference voltage deviation, and perform the suppression control so that the magnetic field direction is the second direction if it is determined that the dry state does not exist.

[0024] For example, the controller can be configured to perform the determination of whether the dry state exists also in consideration of a temperature of the fuel cell stack, and maintain a current state of the magnetic field forming portion when the temperature of the fuel cell stack is below a preset reference temperature.

[0025] For example, the controller is configured to determine whether or not the flooding state is present when the voltage deviation between the cell units of the fuel cell stack exceeds a preset reference voltage deviation, and to maintain the current state of the magnetic field forming section if it is determined that the flooding state is not present.

[0026] For example, the controller is configured to variably control the strength of the magnetic field when the magnetic field is formed by the magnetic field forming section.

[0027] For example, the fuel cell stack can include a first sub-stack including a portion of the at least one fuel cell unit and a second sub-stack including the remaining portion of the at least one fuel cell unit, and the magnetic field forming section can include a first electromagnet forming a magnetic field for the first sub-stack and a second electromagnet forming a magnetic field for the second sub-stack.

[0028] For example, the magnetic field forming section can include at least one electromagnet disposed inside a fastening band that fixes the at least one fuel cell unit in a stacked state.

[0029] According to various embodiments of the present application as described above, the electrochemical reactivity and the water drainage of the fuel cell are adjusted as needed by the magnetic field formed between the anode and the cathode of the fuel cell, and thus the operation strategy of the fuel cell can be diversified.

[0030] In addition, the operation of the fuel cell can be optimized according to the state of the fuel cell, the control conditions, the operation environment, etc. by the various operation strategies as described above.

[0031] The effects obtainable by the present application are not limited to the above-mentioned effects, and other effects not mentioned above can be understood from the following description by those having ordinary skill in the technical field to which the present application pertains. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 FIG. 1 is a diagram for illustrating the structure of a fuel cell system according to an embodiment of the present application.

[0033] Figures 2-3 FIG. 2 is a diagram for illustrating the direction of a magnetic field formed by a magnetic field forming section in a fuel cell system according to an embodiment of the present application.

[0034] Figures 4-10 FIG. 3 is a diagram for illustrating an implementation example of a magnetic field forming section according to an embodiment of the present application.

[0035] Figure 11 and Figure 12 FIG. 4 is a flowchart for illustrating a control process of a fuel cell system performed by a controller according to an embodiment of the present application.

[0036] REFERENCE NUMERALS

[0037] 100: fuel cell stack

[0038] 200: magnetic field forming portion

[0039] 300: controller DETAILED DESCRIPTION

[0040] In the embodiments of the present application disclosed in the present specification or application, the description of specific structures or functions is merely illustrative of the embodiments according to the present application, and is not a restrictive interpretation. The embodiments according to the present application can be implemented in various forms, and the scope of the embodiments should not be limited to the embodiments described in the present specification or application.

[0041] The embodiments according to the present application can be modified in various ways and have various forms, and thus a specific embodiment will be exemplarily illustrated in the accompanying drawings and described in detail. However, this is not intended to limit the embodiments of the present application to a specific disclosed form, and it should be understood that it encompasses all modified embodiments, equivalent embodiments, and alternative embodiments falling within the scope of the idea and technical scope of the present application.

[0042] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0043] Hereinafter, the embodiments disclosed in the present specification will be described in detail with reference to the accompanying drawings, and the same or similar components are given the same reference numerals, regardless of which drawing they are shown in, and repetitive description thereof will be omitted.

[0044] In the description of the following embodiments, the term "pre-set" means that the value of a parameter is determined in advance when the parameter is used in a process or algorithm. Depending on the embodiments, the value of the parameter can be set at the start of the process or algorithm, or dynamically adjusted during its implementation.

[0045] The suffixes "module" and "part" with respect to components used in the following description are given or mixed for the convenience of writing the specification, and do not have meanings or roles that are distinguished from each other by themselves.

[0046] In describing the embodiments disclosed in the present specification, when it is judged that a detailed description of the related art can hinder the understanding of the embodiments disclosed in the present specification, the detailed description thereof is omitted. In addition, the accompanying drawings are only used to assist in the understanding of the embodiments disclosed in the present specification, and the technical idea disclosed in the present specification is not limited by the drawings, and it should be understood that all modified embodiments, equivalent embodiments, and alternative embodiments of the present invention, which belong to the concept and technical scope of the present invention, are included in the protection scope of the present invention.

[0047] Terms including "first", "second", etc. can be used to distinguish different components, but such components are not limited by the terms themselves. Such terms are only used to distinguish one component from another.

[0048] It is to be understood that when a certain component is described as "connected" or "coupled" to another component, it can be directly connected or coupled to the other component, or there can be other components therebetween. In contrast, when a certain component is referred to as being "directly connected" or "directly coupled" to another component, it is to be understood that there are no other components therebetween.

[0049] Unless the context clearly indicates otherwise, the singular form of a term includes the plural.

[0050] In the present specification, the terms "include", "have", etc. are used to indicate that there is presence of the stated feature, number, step, action, element, component, or a combination thereof, but not to exclude the presence or addition of one or more other features, numbers, steps, actions, elements, components, or combinations thereof.

[0051] In addition, the unit or control unit included in the name of the fuel cell control unit (FCU: FUEL CELL Control Unit) and the like is only a naming method widely used in the name of the control device (Controller) that controls a specific function of a vehicle, and does not mean a generic function unit.

[0052] The controller (Controller) can include a communication device for communicating with other controllers or sensors in order to control the functions assumed thereby, a memory storing an operating system or a logic instruction and input / output information, and one or more processors for performing judgment, calculation, determination, etc. required for performing control of the functions assumed thereby.

[0053] The fuel cell system according to an embodiment of the present invention is configured to variably form a magnetic field between an anode and a cathode of a fuel cell unit, whereby it is possible to adjust electrochemical reactivity and drainability of the fuel cell.

[0054] Before describing a control process of a fuel cell system according to an embodiment of the present application, a structure of the fuel cell system will be described first.

[0055] Figure 1 A diagram showing a structure of a fuel cell system according to an embodiment of the present application.

[0056] Referring to Figure 1 A fuel cell system according to an embodiment of the present application can include a fuel cell stack 100, a magnetic field forming portion 200, a controller 300, and a battery 400. Note, however, that Figure 1 Only components relevant to the description of an embodiment of the present application are shown as the main components, and an actual fuel cell system can include more or less components than those shown in the diagram. For example, according to an embodiment, the battery 400 can not be included in the fuel cell system, but can be implemented in the form of being connected to the fuel cell system as a separate structure. Each structure will be described below.

[0057] First, the fuel cell stack 100 can generate electricity by converting chemical energy into electrical energy through an electrochemical reaction based on a redox reaction of supplied hydrogen and oxygen. To this end, the fuel cell stack 100 can include at least one fuel cell unit having an anode and a cathode, and in the fuel cell unit, an electrolyte membrane can be disposed between the anode and the cathode.

[0058] The magnetic field forming portion 200 can be provided to the fuel cell stack 100, and can variably form a magnetic field between the anode and the cathode of at least one fuel cell unit. The magnetic field forming portion 200 can be implemented, for example, by one or more electromagnets provided in the fuel cell stack 100. The effects of the magnetic field formed by the magnetic field forming portion 200 and the magnetic field on the electrochemical reaction and the water discharge will be described below with reference to Figures 2-3

[0059] Figures 2-3 A diagram for describing a direction of a magnetic field formed by a magnetic field forming portion according to an embodiment of the present application.

[0060] Referring to Figures 2-3 A direction of a magnetic field formed by the magnetic field forming portion 200 according to an embodiment of the present application is shown in the form of magnetic force lines (magnetic field lines).

[0061] Among them, Figure 2 A case where a first direction of the magnetic field direction from the cathode 112 side toward the anode 111 side is shown, Figure 3 A case where a second direction of the magnetic field direction from the anode 111 side toward the cathode 112 side is shown. According to the above-described magnetic field direction, the electrochemical reaction and the water discharge of the fuel cell can be promoted or inhibited.

[0062] ​More specifically, by means of the magnetic field formed by the magnetic field forming portion 200, oxygen and water molecules inside the fuel cell unit 110 are subjected to a force shown in the following equation, and thus the movement of the oxygen and water molecules can be adjusted.

[0063]

[0064] (where, F m represents a force applied to an oxygen molecule or a water molecule by a magnetic field, x represents a magnetic susceptibility of the oxygen molecule or the water molecule, u0represents a vacuum permeability, and B represents a strength of the magnetic field.)

[0065] Further, the strength of the magnetic field can be represented by the following equation.

[0066]

[0067] (where, B represents a strength of the magnetic field, N represents a number of turns of a coil, I represents a current applied to the coil, L core represents a length of an electromagnet, μ represents a permeability of the electromagnet, L gap represents a distance from the electromagnet, and u0represents a vacuum permeability.)

[0068] In particular, the electrochemical reaction can be promoted or inhibited in accordance with the force acting on the oxygen molecule, because in the electrochemical reaction region inside the fuel cell unit 110, the oxygen partial pressure changes due to the force of the magnetic field acting on the oxygen molecule, resulting in a change in the exchange current density. Such a relationship between the oxygen partial pressure and the exchange current density can be represented by the following equation.

[0069]

[0070] (where, i0represents an exchange current density, represents a target value of the exchange current density, a c represents a specific surface area of a catalyst, L c represents a catalyst loading per unit volume, P r represents a reactant partial pressure, R represents a gas constant, and T represents a temperature, E c represents an activation energy, and γ represents a pressure coefficient.) For example, as shown in Figure 2 when the magnetic field direction is a first direction from the cathode 112 side toward the anode 111 side, the movement (dl) of the oxygen molecule having paramagnetism in the cathode 112 is guided by the magnetic force toward the direction from the cathode 112 side toward the anode 111 side. In this case, the oxygen inflow to the three-phase boundary side of the cathode 112 where the electrochemical reaction occurs increases, and thus the electrochemical reaction can be promoted.

[0071] On the contrary, as shown in Figure 3As shown in FIG. 6, when the magnetic field direction is the second direction from the anode 111 side toward the cathode 112 side, the movement (dl') of the oxygen molecules having paramagnetism is guided by the magnetic force in the cathode 112 toward the direction from the anode 111 side toward the cathode 112 side. In this case, the inflow of oxygen to the three-phase interface side of the cathode 112 where the electrochemical reaction occurs is reduced, and thus the electrochemical reaction can be suppressed.

[0072] On the other hand, unlike the oxygen molecules, the water molecules have diamagnetism, and thus are guided in the opposite direction in the same magnetic field. For example, as shown in FIG. 7, when the magnetic field direction is the first direction from the cathode 112 side toward the anode 111 side, the movement (d2) of the water molecules is guided by the magnetic force in the cathode 112 toward the direction from the anode 111 side toward the cathode 112 side. In this case, the water moves more or faster toward the outside of the cathode 112 where the water discharge occurs, and thus the water discharge can be promoted. Figure 2

[0073] On the other hand, unlike the oxygen molecules, the water molecules have diamagnetism, and thus are guided in the opposite direction in the same magnetic field. For example, as shown in FIG. 7, when the magnetic field direction is the first direction from the cathode 112 side toward the anode 111 side, the movement (d2) of the water molecules is guided by the magnetic force in the cathode 112 toward the direction from the anode 111 side toward the cathode 112 side. In this case, the water moves more or faster toward the outside of the cathode 112 where the water discharge occurs, and thus the water discharge can be promoted. Figure 3

[0074] When the magnetic field direction is the first direction, the electrochemical reaction and the water discharge are promoted, and when the magnetic field direction is the second direction, the electrochemical reaction and the water discharge are suppressed, and thus the control of the magnetic field direction being the first direction can be expressed as promotion control, and the control of the magnetic field direction being the second direction can be expressed as suppression control.

[0075] Hereinafter, a specific structure of the magnetic field forming portion 200 for forming a magnetic field as described above will be described with reference to Figures 4-10

[0076] Figures 4-10 This is an example for describing an embodiment of the present application, and in addition, the magnetic field forming portion 200 can be implemented in various structures and configurations that can variably form a magnetic field between the anode 111 and the cathode 112 of the fuel cell unit 110. Figures 4-10 First, an example of the magnetic field forming portion 200 that is formed on one side of the fuel cell unit 110 will be described with reference to

[0077] Figure 4 An example of the magnetic field forming portion 200 that is formed on both sides of the fuel cell unit 110 will be described with reference to

[0078] Figure 4 ​​​​​, the magnetic field forming portion 200 can include a plurality of electromagnets 210 arranged in parallel with both sides of the plurality of fuel cell units 110 in the direction in which the plurality of fuel cell units 110 are arranged. At this time, the polarity of the electromagnets 210 on both sides can be variably controlled, and when a magnetic field is formed, it is preferable that the polarity of the electromagnets 210 on both sides be opposite to each other. In addition, the electromagnets 210 on both sides can also be controlled to have no polarity, so that a magnetic field can not be formed, and in order to variably form a magnetic field as described above, the controller 300 can control the current applied to the electromagnets 210.

[0079] Then, Figure 5 An implementation example of the magnetic field forming portion 200 corresponding to each fuel cell unit 110 is shown.

[0080] Referring to Figure 5 , the magnetic field forming portion 200 can include a plurality of electromagnets 210 arranged in parallel with the anode 111 and the cathode 112 side of each fuel cell unit 110. In this case, similarly, the polarity of the electromagnets 210 corresponding to each fuel cell unit 110 can be variably controlled, and when a magnetic field is formed, it is preferable that the polarity of the electromagnets 210 on both sides be opposite to each other. In addition, the electromagnets 210 on both sides can also be controlled to have no polarity. As described above, in order to variably form a magnetic field, the controller 300 can control the current applied to the electromagnets 210. With Figure 4 , an implementation example in which the magnetic field forming portion 200 is formed as shown in Figure 5 , the electrochemical reaction and the water discharge control can be achieved by a magnetic field in units of fuel cell units 110.

[0081] On the other hand, unlike Figure 4 and Figure 5 , an example in which the magnetic field forming portion 200 is implemented by an electromagnet 210 arranged perpendicular to the fuel cell unit 110 is shown. Figure 6

[0082] Referring to Figure 6 , the magnetic field forming portion 200 can include an electromagnet 210 arranged in a direction perpendicular to the arrangement direction of the fuel cell unit 110. At this time, unlike the electromagnet 210 having only a single polarity in Figure 4 and Figure 5 , the electromagnet 210 of the present embodiment can have two poles at the same time. In this case, similarly, the polarity of the electromagnet 210 can be variably controlled, and when a magnetic field is formed, the electromagnet 210 has poles opposite to each other at both ends. In addition, the electromagnet 210 can also be controlled to have no polarity. As described above, in order to variably form a magnetic field, the controller 300 can control the current applied to the electromagnet 210.

[0083] In addition, unlike Figures 4-6 ​As shown, the magnetic field forming section 200 according to a further embodiment of the present application can be implemented in a form in which a plurality of electromagnets 210 having two poles are arranged on both sides (i.e., upper and lower sides in the drawing) of the fuel cell unit 110 in a direction perpendicular to the arrangement direction of the fuel cell unit 110, or a plurality of electromagnets 210 parallel or perpendicular to the fuel cell unit 110 form a layout surrounding three or four sides of the fuel cell unit 110.

[0084] On the other hand, Figures 7-10 An example of implementation of the manner in which the magnetic field forming section 200 is provided to the fuel cell stack 100 is shown.

[0085] Referring to Figures 7-10 The fuel cell stack 100 can be formed by arranging a plurality of fuel cell units 110 in a direction from the lower left end toward the upper right end on the drawing (or the reverse direction).

[0086] In addition, a first sub-stack 100-1 including a part of the plurality of fuel cell units 110 that constitute the fuel cell stack 100 and a second sub-stack 100-2 including the remaining fuel cell units 110 can be included. At this time, the first sub-stack 100-1 can also be described as an upper end sub-stack, and the second sub-stack 100-2 can also be described as a lower end sub-stack.

[0087] In the first sub-stack 100-1 and the second sub-stack 100-2, fuel (hydrogen), air, and coolant can be independently supplied, and temperature sensors s1, s2 can be provided on the side of a coolant outlet through which the coolant performing heat exchange with each is discharged. At this time, the controller 300 can use the temperature detected by the temperature sensors s1, s2 as an index representing the temperature of the first sub-stack 100-1 and the second sub-stack 100-2.

[0088] On the other hand, the first sub-stack 100-1 and the second sub-stack 100-2 can be pressurized and fixed in a stacked state by a fastening band b.

[0089] Based on the structure of the fuel cell stack 100 as described above, referring to Figure 7 The magnetic field forming section 200 according to an embodiment can be implemented by a plurality of electromagnets 210 provided on one side of the fuel cell stack 100. Although not shown in the drawing, at this time, a plurality of electromagnets 210 can also be provided on the other side of the fuel cell stack 100, and further, can also be provided inside the fuel cell stack 100.

[0090] On the other hand, each of the plurality of electromagnets 210 can form a magnetic field and can be independently controlled. At this time, according to a combination of independent control of each, a magnetic field can be formed in a variety of ways in the fuel cell stack 100.

[0091] Specifically, a part of the plurality of electromagnets 210 can form a magnetic field, and the remaining part can not form a magnetic field, and the direction or strength of the magnetic field formed by all or a part of the plurality of electromagnets 210 can also be different.

[0092] For example, Figure 7 As shown, only the electromagnets 210' corresponding to the specific part of the fuel cell stack 100 among the plurality of electromagnets 210 form a magnetic field, and the other electromagnets can not form a magnetic field, thereby the magnetic field can be concentratedly formed at the specific part of the fuel cell stack 100. Therefore, when imbalance occurs due to abnormality of the cell voltage or temperature of the specific part of the fuel cell stack 100, the electrochemical reaction is promoted or inhibited by concentratingly forming a magnetic field at the corresponding part, so that the imbalance can be eliminated.

[0093] Referring to Figure 8 , unlike Figure 7 As shown, the magnetic field forming part 200 according to an embodiment can also be implemented by the first electromagnet 210-1 and the second electromagnet 210-2 corresponding to the first sub-stack 100-1 and the second sub-stack 100-2, respectively. At this time, the first electromagnet 210-1 forms a magnetic field with respect to the first sub-stack 100-1, which can have an influence on the electrochemical reaction and the water discharge of the first sub-stack 100-1, and the second electromagnet 210-2 forms a magnetic field with respect to the second sub-stack 100-2, which can have an influence on the electrochemical reaction and the water discharge of the second sub-stack 100-2. Therefore, the magnetic field forming part 200 implemented by the first electromagnet 210-1 and the second electromagnet 210-2 can independently adjust the electrochemical reaction and the water discharge of the first sub-stack 100-1 and the second sub-stack 100-2.

[0094] Referring to Figure 9 , unlike Figure 7 and Figure 8 As shown, the magnetic field forming part 200 can be provided in the fuel cell stack 100 in parallel with the arrangement direction of the fuel cell units 110, or can be provided at both sides of the fuel cell stack 100. In addition, referring to Figure 10 , the magnetic field forming part 200 can also be formed inside the fastening band b.

[0095] On the other hand, the electromagnets 210 constituting the magnetic field forming part 200 can be implemented in a plate shape as shown in Figures 7-10 , but it is not necessarily limited thereto, and various forms of electromagnets 210 such as a coil shape can be applied to the magnetic field forming part 200. In addition, as described above, the electromagnets 210 can be implemented as a single pole or a double pole.

[0096] Hereinafter, referring again to Figure 1 , based on the above-described configuration and structure of the fuel cell system, the magnetic field variable control performed by the controller 300 of the fuel cell system will be described.

[0097] When the magnetic field is formed by the magnetic field forming portion 200, the controller 300 can selectively control the magnetic field direction to either of a first direction from the cathode 112 side toward the anode 111 side and a second direction from the anode 111 side toward the cathode 112 side, thereby adjusting the electrochemical reaction and the water discharge of the fuel cell. In addition, the controller 300 can variably control the strength of the formed magnetic field.

[0098] In order to form the magnetic field by the magnetic field forming portion 200 and adjust the magnetic field direction and the strength, the controller 300 can control the power supply to the magnetic field forming portion 200. At this time, the controller 300 can supply the power stored in the battery 400 to the magnetic field forming portion 200, or supply the power generated in the fuel cell stack 100 to the magnetic field forming portion 200, to control the magnetic field formation, the magnetic field direction, and the strength by the magnetic field forming portion 200. However, it is not limited thereto, and according to the embodiment, the power supply to the magnetic field forming portion 200 can be implemented in various ways, for example, the controller 300 can control such that a separate auxiliary battery equipped in the fuel cell system supplies the power to the magnetic field forming portion 200.

[0099] On the other hand, in association with the magnetic field direction control, the controller 300 can control the magnetic field direction based on at least one of the power amount of the battery 400 connected to the fuel cell stack 100 and the required output of the fuel cell stack 100. That is, the controller 300 can control the magnetic field direction based on the power amount of the battery 400, or control the magnetic field direction based on the required output of the fuel cell stack 100, or control the magnetic field direction taking both into account.

[0100] More specifically, as an index indicating the power amount of the battery 400, the state of charge (SOC) in % unit can be used, and if the power amount of the battery 400 is lower than a preset lower limit power amount, the controller 300 can control the magnetic field direction to the first direction. Herein, the lower limit power amount can serve as a reference for starting the control for mitigating the over-discharge of the battery 400, and for example, can be set to 35%, however, the value can vary depending on the specifications of the fuel cell stack 100 and the battery 400 applied in the fuel cell system. As described above, when the power amount of the battery 400 is lower than the lower limit power amount, the magnetic field direction is controlled to the first direction, the electrochemical reaction of the fuel cell can be promoted, thereby increasing the power generation amount of the fuel cell stack 100. At this time, the power amount obtained by the power generation power can be increased, and thus, the over-discharge state of the battery 400 can be eventually mitigated, for example, the time for which the power amount of the battery 400 is maintained below the lower limit power amount can be shortened, etc.

[0101] In addition, if the amount of charge of the battery 400 exceeds a preset upper limit amount of charge, the controller 300 can control the direction of the magnetic field to the second direction. The upper limit amount of charge can serve as a reference for starting control for mitigating overcharging of the battery 400, and can be set to 80%, for example, but the value can vary depending on the specifications of the fuel cell stack 100 and the battery 400 applied in the fuel cell system. As described above, when the amount of charge of the battery 400 exceeds the upper limit amount of charge, the direction of the magnetic field is controlled to the second direction, and the electrochemical reaction of the fuel cell is suppressed, thereby reducing the power generation amount of the fuel cell stack 100. At this time, the amount of charge obtained by the power generation of the battery 400 is reduced, and thus the overcharged state of the battery 400 can be eventually mitigated, for example, by reducing the time for which the amount of charge of the battery 400 is maintained to exceed the upper limit amount of charge.

[0102] In addition, the controller 300 can control the direction of the magnetic field formed by the magnetic field forming portion 200 based on a required output of the fuel cell stack 100, which can represent a target amount of output (amount of charge) of the fuel cell stack 100.

[0103] More specifically, the controller 300 can control the direction of the magnetic field based on the amount of change per unit time of the required output, and when the amount of change per unit time of the required output exceeds a preset change amount increase threshold, the direction of the magnetic field can be controlled to the first direction. The change amount increase threshold can serve as a reference for determining whether the required output is rapidly increasing, and can be set to a positive value for this purpose. The specific value can vary depending on the specifications of the fuel cell stack 100 applied in the fuel cell system.

[0104] As described above, when the amount of change per unit time of the required output exceeds the preset change amount increase threshold, the direction of the magnetic field is controlled to the first direction, and thus if the required output rapidly increases, the output performance of the fuel cell stack 100 can be improved by promoting the electrochemical reaction of the fuel cell.

[0105] In addition, when the amount of change per unit time of the required output is lower than a preset change amount decrease threshold, the controller 300 can control the direction of the magnetic field based on the voltage of the stack 100 and an upper limit voltage. The change amount decrease threshold can serve as a reference for determining whether the required output is rapidly decreasing, and can be set to a negative value for this purpose. The specific value can vary depending on the specifications of the fuel cell stack 100 applied in the fuel cell system. In addition, the setting of the upper limit voltage can be used to protect the fuel cell stack 100 and ensure stable operation, and the voltage of the fuel cell stack 100 can be limited according to the upper limit voltage. Specifically, when the amount of change per unit time of the required output is lower than the change amount decrease threshold, if the voltage of the fuel cell stack 100 exceeds the upper limit voltage, the controller 300 can control the direction of the magnetic field to the second direction.

[0106] As described above, in a case where the amount of change in the required output per unit time is lower than the preset change amount reduction threshold, when the upper limit voltage is reached, the magnetic field direction is controlled to the second direction, and thus the voltage of the fuel cell stack 100 can be reduced by suppressing the electrochemical reaction of the fuel cell, and the state where the voltage of the fuel cell stack 100 exceeds the upper limit voltage can be eliminated. On the other hand, when the amount of charge of the battery 400 is equal to or higher than the preset lower limit amount of charge and equal to or lower than the preset upper limit amount of charge, the controller 300 can control the magnetic field direction based on the water state of the fuel cell stack, the water state including a flooded state and a dry state. In addition, when the amount of change in the required output per unit time is lower than the change amount reduction threshold, if the voltage of the fuel cell stack 100 is equal to or lower than the upper limit voltage, the controller 300 can control the magnetic field direction based on the water state of the fuel cell stack 100, the water state including the dry state and the flooded state.

[0107] Here, the flooded state can be understood as a state in which water generated by the electrochemical reaction cannot be properly discharged to the outside and hinders the diffusion of fuel (hydrogen), and the dry state can be understood as a state in which the movement of ions and electrons is slowed down due to lower humidity within the fuel cell unit.

[0108] Specifically, when the water state of the fuel cell stack 100 is the dry state, the controller 300 can control so that the magnetic field direction is the second direction. In this case, the electrochemical reaction is suppressed, and the discharge of water generated by the electrochemical reaction is also suppressed, and thus it can be helpful to eliminate the dry state.

[0109] Unlike this, when the water state of the fuel cell stack 100 is the flooded state, the controller 300 can control so that the magnetic field direction is the first direction. In this case, the electrochemical reaction is promoted, and the discharge of water generated by the electrochemical reaction is also promoted, and thus it can be helpful to eliminate the flooded state.

[0110] On the other hand, the controller 300 can independently control the magnetic field formed by the magnetic field forming portion 200 in units of sub-stacks. For example, in a case where the fuel cell stack 100 includes a first sub-stack 100-1 including a part of the fuel cell units 110 and a second sub-stack 100-2 including the remaining part of the fuel cell units, the controller 300 can control the magnetic field forming portion 200 so that the magnetic field is formed independently for the fuel cell units 110 included in the first sub-stack 100-1 and the fuel cell units 110 included in the second sub-stack 100-2, respectively. Further, in the fuel cell stack 100, in addition to the first sub-stack 110-1 and the second sub-stack 110-3, an additional sub-stack can be provided, and in this case, the controller 300 can also independently control the magnetic field in units of sub-stacks.

[0111] As described above, when the magnetic field is controlled in units of the sub-stacks constituting the fuel cell stack 100, the controller 300 can control the magnetic field direction of the first sub-stack 100-1 and the second sub-stack 100-2 based on the temperature difference between the first sub-stack 100-1 and the second sub-stack 100-2.

[0112] Specifically, when the temperature difference between the first sub-stack 100-1 and the second sub-stack 100-2 exceeds a preset reference temperature difference, the controller 300 can control the magnetic field direction of either of the first sub-stack 100-1 and the second sub-stack 100-2. Here, the temperature difference between the first sub-stack 100-1 and the second sub-stack 100-2 and the reference temperature difference can be used as an index for judging the degree of imbalance between the sub-stacks, and the reference temperature difference can be set to 2°C, for example, but can vary depending on the specifications of the fuel cell system.

[0113] For example, when the temperature difference between the first sub-stack 100-1 and the second sub-stack 100-2 exceeds the preset reference temperature difference and the moisture state of the fuel cell stack 100 is the dry state, the controller 300 can control the magnetic field direction of the sub-stack having a relatively lower temperature among the first sub-stack 100-1 and the second sub-stack 100-2 to the second direction.

[0114] At this time, the electrochemical reaction of the sub-stack having a relatively low temperature can be suppressed while the water discharge is suppressed, thereby preventing the deterioration of the dry state. In addition, in this case, the oxygen inflow to the cathode is reduced, so that the mass transfer resistance of the sub-stack having a relatively low temperature increases, and thus the heat generation amount of the sub-stack having a relatively low temperature increases, so that the temperature difference between the sub-stacks can be reduced.

[0115] In addition, when the temperature difference between the first sub-stack 100-1 and the second sub-stack 100-2 exceeds the preset reference temperature difference and the moisture state of the fuel cell stack 100 is the flooded state, the controller 300 can control the magnetic field direction of the sub-stack having a relatively high temperature among the first sub-stack 100-1 and the second sub-stack 100-2 to the first direction.

[0116] At this time, the electrochemical reaction of the sub-stack having a relatively high temperature can be promoted while the water discharge is promoted, thereby preventing the deterioration of the flooded state. In addition, in this case, the oxygen inflow to the cathode is increased, so that the mass transfer resistance of the sub-stack having a relatively high temperature decreases, and thus the heat generation amount of the sub-stack having a relatively high temperature decreases, so that the temperature difference between the sub-stacks can be reduced.

[0117] As described above, by independently controlling the magnetic field of the sub-stacks based on the temperature difference between the sub-stacks, the voltage deviation between the fuel cell units due to the imbalance state between the sub-stacks can be prevented from becoming large.

[0118] On the other hand, when the temperature difference between the first sub stack 100-1 and the second sub stack 100-2 is below the preset reference temperature difference, the controller 300 can control the magnetic field directions of the first and second sub stacks together. That is, in this case, the magnetic fields of the first and second sub stacks can be controlled to be in the same direction.

[0119] For example, when the temperature difference between the first sub stack 100-1 and the second sub stack 100-2 is below the preset reference temperature difference and the moisture state of the fuel cell stack 100 is the dry state, the controller 300 can control the magnetic fields of the first and second sub stacks 100-1 and 100-2 to be in the second direction. Also, when the temperature difference between the first sub stack 100-1 and the second sub stack 100-2 is below the preset reference temperature difference and the moisture state of the fuel cell stack 100 is the flooded state, the controller 300 can control the magnetic fields of the first and second sub stacks 100-1 and 100-2 to be in the first direction.

[0120] On the other hand, when the magnetic field is controlled based on the temperature difference between the sub stacks as described above, the controller 300 can determine the temperature difference between the first sub stack 100-1 and the second sub stack 100-2 based on the coolant temperature at the outlet side of the coolant, which flows out after heat exchange with the fuel cell stack 100, for which the sensing results of the temperature sensors s1 and s2 provided in each sub stack can be used. At this time, the coolant at the outlet side of the coolant has reached thermal equilibrium with the sub stacks through heat exchange with the sub stacks, and thus can be used as a means to effectively reflect the temperature of the sub stacks. However, the temperature difference between the sub stacks is not necessarily determined based on the coolant temperature at the outlet side of the coolant as described above, but can be determined based on the temperature of each sub stack measured, determined, or estimated in various ways.

[0121] On the other hand, the controller 300 can perform either of the determination of whether it is the flooded state and the determination of whether it is the dry state, according to the comparison result of the voltage deviation between the cell units of the fuel cell stack 100 and the preset reference voltage deviation. Here, the voltage deviation between the cell units can represent a value obtained by subtracting the voltage of the fuel cell unit having the lowest voltage from the average cell unit voltage obtained by dividing the entire stack voltage by the number of fuel cell units, and the reference voltage deviation can be set to 40 mV, for example, but the specific value thereof can vary depending on the specifications of the fuel cell system.

[0122] Specifically, when the voltage deviation between the cell units is below the preset reference voltage deviation, the controller 300 can determine whether it is the dry state, and if it is determined that it is not the dry state, control such that the magnetic field direction is the second direction to suppress the electrochemical reaction, so that the voltage of the fuel cell unit can be lowered.

[0123] In addition, when the voltage deviation between the battery cells exceeds the preset reference voltage deviation, the controller 300 can determine whether it is a flooded state, and as a result, if it is determined that it is not a flooded state, the current state of the magnetic field forming portion 200 can be maintained. For example, when the current magnetic field is formed in the first direction, the magnetic field direction can be maintained as the first direction, and in a state in which the current magnetic field forming portion 200 does not form a magnetic field, the state in which the magnetic field is not formed can be maintained. In addition, the controller 300 can maintain other operating conditions of the fuel cell in addition to the state of the magnetic field forming portion 200. Furthermore, in this case, it can be considered that the voltage deviation between the battery cells is caused by a cause other than the flooded state, and thus the controller 300 can determine other causes of the voltage deviation between the battery cells, such as whether low flow control is performed.

[0124] On the other hand, the controller 300 can further consider the temperature of the fuel cell stack 100 to perform determination of whether it is a dry state. Here, the temperature of the fuel cell stack 100 can indicate an average temperature of the entire fuel cell stack 100 or a temperature of a specific point, and can also indicate a coolant temperature at the outlet side of the fuel cell stack 100.

[0125] At this time, when the temperature of the fuel cell stack 100 is below a preset reference temperature, the controller 300 can maintain the current state of the magnetic field forming portion 200, and can maintain other operating conditions of the fuel cell in addition to the state of the magnetic field forming portion 200. Here, the reference temperature can be set through a vehicle test or the like, and for example, can be set to 75°C, but the specific value thereof can vary depending on the specifications of the fuel cell system.

[0126] On the other hand, the determination of whether it is a flooded state and the determination of whether it is a dry state as described above can be performed based on Electrochemical Impedance Spectroscopy (EIS).

[0127] For example, the determination of whether it is a dry state can be performed based on a High Frequency Resistance (HFR) value measured in a state in which a drain valve for discharging water generated by an electrochemical reaction of the fuel cell to the outside is closed.

[0128] In addition, the determination of whether it is a flooded state can be performed based on a Mid Frequency Resistance (MFR) and a Low Frequency Resistance (LFR) value measured in a state in which a drain valve for discharging water generated by an electrochemical reaction of the fuel cell to the outside is closed.

[0129] On the other hand, the controller 300 can not only control the direction of the generated magnetic field but also control the strength of the magnetic field, and can adjust the degree of promotion or inhibition of the electrochemical reaction and water discharge of the fuel cell in accordance with the strength adjustment of the magnetic field. In addition, as described above, the controller 300 can take into account the state of the fuel cell stack 100 when adjusting the strength of the magnetic field.

[0130] Specifically, when the fuel cell stack 100 is implemented in a manner including a plurality of sub-stacks, the controller 300 can control the strength of the magnetic field based on the temperature difference between the sub-stacks. For example, the controller 300 can control the strength of the magnetic field so that it is relatively reduced when the temperature difference between the sub-stacks is small compared to when the temperature difference between the sub-stacks is large. At this time, the controller 300 can also gradually reduce the strength of the magnetic field in a process of making the temperatures between the sub-stacks tend to be the same by magnetic field control, and can also cancel the generation of the magnetic field after the temperatures between the sub-stacks are the same. In addition, the controller 300 can also control the strength of the magnetic field based on the voltage deviation between the cell units. For example, the controller 300 can control the strength of the magnetic field so that it is relatively reduced when the voltage deviation between the cell units is small compared to when the voltage deviation between the cell units is large. At this time, the controller 300 can also gradually reduce the strength of the magnetic field in a process of alleviating the voltage deviation between the cell units by magnetic field control, and can also cancel the generation of the magnetic field after the voltage deviation between the cell units is eliminated.

[0131] In addition to the above examples, the controller 300 can control the strength of the magnetic field in consideration of the state of the fuel cell stack 100 from the perspective of promoting or inhibiting the electrochemical reaction and water discharge of the fuel cell.

[0132] Hereinafter, the control process performed by the above-described controller 300 will be described through a flowchart.

[0133] Figure 11 and Figure 12 A sequence diagram for a control process of a fuel cell system performed by a controller according to an embodiment of the present application.

[0134] First, referring to Figure 11 , a flowchart of magnetic field control based on the battery 400 power is shown. The controller 300 can determine the power of the battery 400 before controlling the magnetic field generated by the magnetic field generation unit 200 (S1101), and the controller 300 controls the magnetic field generation unit 200 based on the determined power of the battery 400, thereby controlling the direction of the magnetic field formed in the fuel cell unit. At this time, the process (S1101) can be performed in a state in which a water discharge valve for discharging water generated by the electrochemical reaction of the fuel cell to the outside is closed.

[0135] Specifically, when the judged battery 400 electric quantity is lower than the preset lower limit electric quantity (S1102), the controller 300 controls the magnetic field direction formed by the magnetic field forming part 200 to the first direction (S1103) to promote the electrochemical reaction and drainage, thereby relieving the over-discharge state of the battery 400.

[0136] Different from this, when the judged battery 400 electric quantity exceeds the preset upper limit electric quantity (S1104), the controller 300 controls the magnetic field direction formed by the magnetic field forming part 200 to the second direction (S1105) to inhibit the electrochemical reaction and drainage, thereby relieving the over-charge state of the battery 400.

[0137] On the other hand, when the judged battery 400 electric quantity is above the lower limit electric quantity and below the upper limit electric quantity (S1106), the controller 300 can judge the temperature of the fuel cell stack 100 (S1107), and control the magnetic field forming part 200 based on the judged temperature of the fuel cell stack 100. Moreover, at this time, the temperature of the fuel cell stack 100 can be judged respectively in the sub-stack unit.

[0138] Then, the controller 300 can perform the judgment of whether it is the flooded state or the judgment of whether it is the dry-out state based on the voltage deviation between the battery cells (S1108). At this time, when the voltage deviation between the battery cells exceeds the preset reference voltage deviation (YES of S1108), the controller 300 can judge whether it is the flooded state (S1109), and if the result of the judgment is the flooded state (YES of S1109), the controller 300 can control the magnetic field in the sub-stack unit based on the temperature difference between the sub-stacks (S1110). Specifically, when the temperature difference between the sub-stacks exceeds the preset reference temperature difference (YES of S1110), the controller 300 can control the magnetic field direction of the sub-stack with relatively high temperature to the first direction (S1111) to prevent the deterioration of the flooded state and eliminate the temperature difference between the sub-stacks. On the contrary, when the temperature difference between the sub-stacks is below the preset reference temperature difference (NO of S1110), the magnetic field direction can be controlled to the first direction (S1112) for the entire fuel cell stack 100 to prevent the deterioration of the flooded state.

[0139] On the other hand, for the judgment result of whether it is the flooded state, if it is judged that it is not the flooded state (NO of S1109), the controller 300 can maintain the current state of the magnetic field forming part 200 and judge other causes of the voltage deviation between the battery cells.

[0140] Different from this, when the voltage deviation between the battery cells is below the preset reference voltage deviation (NO of S1108), the controller 300 can also perform the judgment of whether it is the dry-out state considering the temperature of the fuel cell stack 100 (S1114).

[0141] At this time, when the temperature of the fuel cell stack 100 is below the preset reference temperature (NO in S1114), the controller 300 can maintain the current state of the magnetic field forming portion 200 without making a determination as to whether it is in the dry-out state.

[0142] In contrast, when the temperature of the fuel cell stack 100 exceeds the preset reference temperature (YES in S1114), a determination can be made as to whether it is in the dry-out state (S1116). At this time, when it is determined that it is not in the dry-out state (NO in S1116), the controller 300 can control the magnetic field direction of the entire fuel cell stack 100 to the second direction to suppress the electrochemical reaction.

[0143] In contrast, when it is determined that it is in the dry-out state (YES in S1116), the magnetic field control can be performed on a sub-stack unit basis based on the temperature difference between the sub-stacks (S1118). At this time, if the temperature difference between the sub-stacks exceeds the preset reference temperature difference (YES in S1118), the controller 300 can control the magnetic field direction of the sub-stack that is relatively low in temperature to the second direction (S1119) to prevent the dry-out state from worsening and eliminate the temperature difference between the sub-stacks, and when the temperature difference between the sub-stacks is below the preset reference temperature difference (NO in S1118), the magnetic field direction of the entire fuel cell stack 100 can be controlled to the second direction (S1120) to prevent the dry-out state from worsening.

[0144] On the other hand, regarding the magnetic field control based on the required output of the fuel cell stack 100, a description will be made below with reference to Figure 12 .

[0145] With reference to Figure 12 , the controller 300 can determine the amount of change in the required output of the fuel cell stack 100 per unit time before controlling the magnetic field formed by the magnetic field forming portion 200 (S1201), and the controller 300 controls the magnetic field direction formed at the fuel cell unit by controlling the magnetic field forming portion 200 based on the determined amount of change in the required output per unit time.

[0146] Specifically, when the determined amount of change in the required output per unit time exceeds a preset change amount increase threshold (S1202), the controller 300 controls the magnetic field direction formed by the magnetic field forming portion 200 to the first direction (S1203) to promote the electrochemical reaction, whereby the output of the fuel cell stack 100 can be increased in correspondence with an increase in the required output.

[0147] In contrast, when the judged amount of change in the required output per unit time is below the preset amount of change reduction threshold (S1204), the controller 300 can control the magnetic field direction of the magnetic field forming portion 200 based on the voltage of the fuel cell stack 100 and the upper limit voltage (S1205). At this time, if the voltage of the fuel cell stack 100 exceeds the upper limit voltage (NO in S1205), the controller 300 controls the magnetic field direction formed by the magnetic field forming portion 200 to the second direction (S1205'), to suppress the electrochemical reaction, whereby the voltage of the fuel cell stack 100 can be reduced, and the state of exceeding the upper limit voltage can be eliminated.

[0148] On the other hand, when the voltage of the fuel cell stack 100 is below the upper limit voltage (YES in S1205), and the judged state of charge of the battery 400 is above the lower limit state of charge and below the upper limit state of charge (S1206), the controller 300 can judge the temperature of the fuel cell stack 100 (S1207), and control the magnetic field forming portion 200 based on the judged temperature of the fuel cell stack 100. Also, the temperature of the fuel cell stack 100 can be judged separately for each sub-stack at this time.

[0149] Then, the controller 300 can perform the judgment of whether or not it is a flooded state or the judgment of whether or not it is a dry state based on the voltage deviation between the battery cells (S1208). At this time, when the voltage deviation between the battery cells exceeds the preset reference voltage deviation (YES in S1208), the controller 300 can judge whether or not it is a flooded state (S1209), and if the result of the judgment is that it is a flooded state (YES in S1209), the magnetic field can be controlled for each sub-stack based on the temperature difference between the sub-stacks (S1210).

[0150] Specifically, when the temperature difference between the sub-stacks exceeds the preset reference temperature difference (YES in S1210), the magnetic field direction of the sub-stack having a relatively high temperature can be controlled to the first direction (S1211), to prevent the deterioration of the flooded state, and to eliminate the temperature difference between the sub-stacks.

[0151] In contrast, when the temperature difference between the sub-stacks is below the preset reference temperature difference (NO in S1210), the magnetic field direction of the entire fuel cell stack 100 can be controlled to the first direction (S1212), to prevent the deterioration of the flooded state.

[0152] On the other hand, for the result of the judgment of whether or not it is a flooded state, if it is judged that it is not a flooded state (NO in S1209), the controller 300 can maintain the current state of the magnetic field forming portion 200, and judge other causes of the voltage deviation between the battery cells.

[0153] On the other hand, when the voltage deviation between the battery cells is below the preset reference voltage deviation (NO in S1208), the controller 300 can further consider the temperature of the fuel cell stack 100 to perform the determination of whether it is in the dry-out state (S1214).

[0154] At this time, when the temperature of the fuel cell stack 100 is below the preset reference temperature (NO in S1214), the controller 300 can maintain the current state of the magnetic field forming portion 200 without performing the determination of whether it is in the dry-out state.

[0155] On the other hand, when the temperature of the fuel cell stack 100 exceeds the preset reference temperature (YES in S1214), the determination of whether it is in the dry-out state can be performed (S1216). At this time, when it is determined that it is not in the dry-out state (NO in S1216), the controller 300 can control the magnetic field direction of the entire fuel cell stack 100 to the second direction to suppress the electrochemical reaction.

[0156] On the other hand, when it is determined that it is in the dry-out state (YES in S1216), the magnetic field control can be performed on a sub-stack unit basis based on the temperature difference between the sub-stacks (S1218). At this time, if the temperature difference between the sub-stacks exceeds the preset reference temperature difference (YES in S1218), the controller 300 can control the magnetic field direction of the sub-stack having a relatively low temperature among the sub-stacks to the second direction (S1219) to prevent the dry-out state from deteriorating and eliminate the temperature difference between the sub-stacks, and when the temperature difference between the sub-stacks is below the preset reference temperature difference (NO in S1218), the magnetic field direction of the entire fuel cell stack 100 can be controlled to the second direction (S1220) to prevent the dry-out state from deteriorating.

[0157] On the other hand, Figure 11 and Figure 12 The embodiment in which the fuel cell system includes a plurality of sub-stacks and performs individual control on a sub-stack unit basis is illustrated, however, referring to the contents described in Figures 1-10 the fuel cell system according to another embodiment can also be implemented in a manner in which the magnetic field of a single fuel cell stack is collectively controlled, or in a manner in which the magnetic field of the entire sub-stacks is collectively controlled although the fuel cell system includes a plurality of sub-stacks. Also, according to the embodiment, the magnetic field of a single fuel cell stack or a plurality of sub-stacks can also be controlled in zones through individual control of a plurality of electromagnets.

[0158] According to the various embodiments of the present application as described above, the electrochemical reactivity and the water drainage of the fuel cell can be adjusted as needed through the magnetic field formed between the anode and the cathode of the fuel cell, and thus the diversification of the fuel cell operation strategy can be achieved.

[0159] In addition, through the various operation strategies as described above, the operation of the fuel cell can be optimized according to the state of the fuel cell, the control conditions, the operation environment, etc.

[0160] In view of the foregoing, it will be seen that the several advantages of the application are achieved and attained by means of the structures and combinations of matter, components, and steps described in full above, and which are thus also regarded as being within the scope of the application, which has been described with reference to the preferred embodiments.

Claims

1. A fuel cell system comprising: a fuel cell stack including at least one fuel cell unit having an anode and a cathode; a magnetic field forming portion provided to the fuel cell stack and variably forming a magnetic field between the anode and the cathode of the at least one fuel cell unit; and a controller selectively controlling a direction of the magnetic field to either one of a first direction from the cathode side toward the anode side and a second direction from the anode side toward the cathode side when the magnetic field is formed by the magnetic field forming portion. The controller is configured to:

2. The fuel cell system according to claim 1, characterized by control the direction of the magnetic field based on at least one of an amount of electricity of a battery connected to the fuel cell stack and a required output of the fuel cell stack. The controller is configured to:

3. The fuel cell system of claim 2, wherein, perform at least one of promotion control that controls the direction of the magnetic field to the first direction when the amount of electricity of the battery is below a preset lower limit amount of electricity and suppression control that controls the direction of the magnetic field to the second direction when the amount of electricity of the battery exceeds a preset upper limit amount of electricity. The controller is configured to:

4. The fuel cell system according to claim 2, wherein: control the direction of the magnetic field based on a moisture state of the fuel cell stack when the amount of electricity of the battery is above the lower limit amount of electricity and below the upper limit amount of electricity, the moisture state including a flooded state and a dry state. The controller is configured to:

5. The fuel cell system of claim 2, wherein perform the promotion control that controls the direction of the magnetic field to the first direction when a change amount per unit time of the required output of the fuel cell stack exceeds a preset change amount increase threshold value, the preset change amount increase threshold value being a positive number. The controller is configured to:

6. The fuel cell system of claim 2, wherein control the direction of the magnetic field based on a stack voltage of the fuel cell stack and a preset upper limit voltage when the change amount per unit time of the required output of the fuel cell stack is below a preset change amount decrease threshold value, the preset change amount decrease threshold value being a negative number. The controller is configured to:

7. The fuel cell system of claim 6, wherein perform the suppression control that controls the direction of the magnetic field to the second direction when the stack voltage of the fuel cell stack exceeds the upper limit voltage. The controller is configured to:

8. The fuel cell system of claim 6, wherein control the direction of the magnetic field based on the moisture state of the fuel cell stack when the stack voltage of the fuel cell stack is below the upper limit voltage, the moisture state including the flooded state and the dry state. The controller is configured to:

9. The fuel cell system of claim 2, wherein control the direction of the magnetic field based on the moisture state of the fuel cell stack when the change amount per unit time of the required output of the fuel cell stack is below the preset change amount increase threshold value and above the preset change amount decrease threshold value, the preset change amount increase threshold value being a positive number, the preset change amount decrease threshold value being a negative number. The controller is configured to:

10. The fuel cell system of claim 1, wherein perform at least one of suppression control that controls so that the direction of the magnetic field is the second direction when the moisture state of the fuel cell stack is the dry state and promotion control that controls so that the direction of the magnetic field is the first direction when the moisture state of the fuel cell stack is the flooded state.

11. The fuel cell system according to claim 1, wherein the fuel cell stack includes a first sub-stack including a part of the at least one fuel cell unit and a second sub-stack including a remaining part of the at least one fuel cell unit. ​ The magnetic field forming portion is configured to form a magnetic field independently for the fuel cell unit included in the first sub stack and the fuel cell unit included in the second sub stack, respectively. The controller is configured to control the direction of the magnetic field of the first sub stack and the second sub stack based on a temperature difference between the first sub stack and the second sub stack.

12. The fuel cell system of claim 11, wherein, The controller is configured to: control the direction of the magnetic field of either one of the first sub stack and the second sub stack when the temperature difference between the first sub stack and the second sub stack exceeds a predetermined reference temperature difference.

13. The fuel cell system of claim 12, wherein, The controller is configured to: perform suppression control so that the direction of the magnetic field of the sub stack having a relatively lower temperature among the first sub stack and the second sub stack is the second direction when the temperature difference between the first sub stack and the second sub stack exceeds the predetermined reference temperature difference and the moisture state of the fuel cell stack is a dry state.

14. The fuel cell system of claim 12, wherein, The controller is configured to: perform promotion control so that the direction of the magnetic field of the sub stack having a relatively higher temperature among the first sub stack and the second sub stack is the first direction when the temperature difference between the first sub stack and the second sub stack exceeds the predetermined reference temperature difference and the moisture state of the fuel cell stack is a flooded state.

15. The fuel cell system of claim 1, wherein, The controller is configured to: determine whether or not it is the dry state when the voltage deviation between the cell units of the fuel cell stack is equal to or less than a predetermined reference voltage deviation, and perform suppression control so that the direction of the magnetic field is the second direction if it is determined that it is not the dry state.

16. The fuel cell system of claim 15, wherein, The controller is further configured to: perform the determination of whether or not it is the dry state in consideration of the temperature of the fuel cell stack, and maintain the current state of the magnetic field forming portion when the temperature of the fuel cell stack is equal to or less than a predetermined reference temperature.

17. The fuel cell system of claim 1, wherein The controller is configured to: determine whether or not it is the flooded state when the voltage deviation between the cell units of the fuel cell stack exceeds the predetermined reference voltage deviation, and maintain the current state of the magnetic field forming portion if it is determined that it is not the flooded state.

18. The fuel cell system of claim 1, wherein, The controller is configured to: be capable of variably controlling the strength of the magnetic field when the magnetic field is formed by the magnetic field forming portion.

19. The fuel cell system according to claim 1, wherein the fuel cell stack includes a first sub stack including a part of the at least one fuel cell unit and a second sub stack including the remaining part of the at least one fuel cell unit; the magnetic field forming portion includes a first electromagnet forming a magnetic field for the first sub stack and a second electromagnet forming a magnetic field for the second sub stack.

20. The fuel cell system according to claim 1, wherein the magnetic field forming portion includes at least one electromagnet disposed inside a fastening band that fastens the at least one fuel cell unit in a stacked state.

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