Device and method for controlling the cold start of a fuel cell system

Abstract

Device for controlling a cold start of a fuel cell system, comprising: a fuel cell (30) configured to supply current to a motor (10) during a cold start condition of the fuel cell system; and a torque limiting part (20) configured to limit a torque generated, when a rotor of the motor (10) rotates angularly forwards and backwards within a predetermined angular range based on an application of the current, wherein the output power consumption of the fuel cell (30) is increased due to the power consumed in the engine (10) during the cold start condition.

Description

BACKGROUND(a) Technical area

[0001] The present disclosure relates to a device and method for controlling a cold start of a fuel cell system. More specifically, the present invention relates to a device and method for controlling a cold start of a fuel cell system capable of increasing a fuel cell load to reduce a cold start time, using a kinetic energy storage method for a rotor of a motor for operating a fuel cell system. (b) Background of the prior art

[0002] In a hydrogen fuel cell system, cold-start performance can be difficult during the winter season (e.g., during substantially cold weather). Prior art methods have been developed to rapidly thaw pure water within a column, using a heating element to thaw an antifreeze liquid for a fuel cell stack as cooling water, and the like.

[0003] Despite the methods developed to ensure cold-start performance, when the fuel cell system is exposed to a substantially low-temperature environment, such as subzero temperatures, the temperature of the fuel cell stack with which the fuel cell system is equipped drops below zero degrees, causing the fuel cell stack to potentially freeze. To quickly raise the stack temperature during cold start-up of the fuel cell system, it is efficient for the fuel cell stack to output a significant current to utilize the heat generated by a unique chemical reaction within the stack.Accordingly, a method for outputting an output current of the stack by maximally utilizing various loads accommodated within a vehicle was developed, and a motor was used as a heating element to increase the current load of a stack.

[0004] In other words, a technology has been developed that contributes to increasing the stack temperature by transferring heat from a motor and an inverter to the stack by using the phase resistance heating of a running motor as a current load of the stack, but with control performed to interrupt motor torque generation so as not to prevent the motor from being driven. Accordingly, various technologies have been proposed for improving the cold start of the fuel cell system, but a more efficient method has been continuously needed.

[0005] KR 10 2015 0 078 448 A discloses a method for controlling a cold start of a fuel cell vehicle, which enables improvement in starting performance in a cold state of the fuel cell vehicle. The method includes a step of detecting a temperature of a fuel cell stack to determine whether or not the temperature is suitable for a cold start condition when a start request is detected; a step of outputting a PWM signal to drive a motor and executing a braking control to simultaneously generate a power loss when suitable for the cold start condition; and a step of shortening the time to reach an activation temperature by increasing the amount of output current of the fuel cell stack through the driving of the motor and the braking control under the cold start condition.

[0006] The above information disclosed in this section is only intended to facilitate understanding of the background of the invention and may therefore contain information that does not constitute prior art already known to a person skilled in the art in this country. SUMMARY

[0007] The invention is defined by the independent claims. The dependent claims define advantageous embodiments.

[0008] The present invention provides an apparatus and method for controlling a cold start of a fuel cell system, which can improve cold start performance by performing self-heating of a fuel cell stack based on increasing an output current amount of a fuel cell, by restricting a motor torque simultaneously with generating the torque while a current is applied to a motor when a vehicle stops to consume an output current of the fuel cell.

[0009] In one aspect, the present invention provides an apparatus for controlling a cold start of a fuel cell system, which may include: a fuel cell configured to apply a current to a motor during a cold start condition of the fuel cell system; and a torque limiting part configured to limit a torque generated when a rotor of the motor angularly rotates forward and backward within a predetermined angular range based on an application of the current, wherein the output power consumption of the fuel cell may be increased due to power consumed in the motor during the cold start condition. In addition, the torque limiting part may be configured as a park (P) stage pawl of a reduction gear.A reduction gear can be used, which is restrictively connected to an output shaft extending from the motor rotor to a drive wheel. The torque restriction or limiting part can be a hydraulic brake device of a drive wheel.

[0010] In another aspect, the present invention provides a method for controlling a cold start of a fuel cell system, which may include: applying an output current of a fuel cell to a motor during a cold start condition of the fuel cell system; increasing the output current consumption of the fuel cell by angularly rotating a rotor of the motor forward and reverse within a predetermined angular range based on an application of the current; and limiting a torque generated when the rotor of the motor angularly rotates.

[0011] Furthermore, when increasing the output power consumption of the fuel cell while driving the motor, the power consumption, which is a value obtained by multiplying a forward (+) rotation speed of the rotor by a positive (+) torque generated when the motor rotates forward (+), can be generated, and the power consumption, which is a value obtained by multiplying a reverse (-) rotation speed of the rotor by a negative (-) torque generated when the rotor rotates in a reverse (-) direction, can be generated. In addition, when limiting the torque, a driver can perform shifting to a P-stage, thus restrictively connecting a P-stage pawl of a reduction gear to an output shaft of the rotor of a drive wheel.When limiting torque, a driver can operate a hydraulic brake device of a drive wheel to throttle the drive wheel, which is connected to the rotor via an output shaft.

[0012] With the above configuration, the present invention has the following effects.

[0013] First, it is possible to increase the output current amount of the fuel cell based on the consumption of kinetic energy of the rotor by causing the rotor to be the fuel cell load, and to reduce the cold start time by performing self-warming of the fuel cell stack based on the output current amount of the fuel cell by applying a current to the motor to drive the fuel cell system during the cold start state to generate the angular rotation and torque of the rotor.

[0014] Secondly, it may be possible to prevent the motor from driving the motor for the current driving before the motor torque of the motor is stopped by the torque limiting device (e.g., the P-stage pawl of the reduction gear and the hydraulic brake device of the drive wheel).

[0015] Third, since the rotor of the motor can be rotated forward and backward at a predetermined angle to generate torque, the IGBT for forward and reverse control of the rotor can be uniformly used among the plurality of IGBTs of the inverter, which is a type of control element configured for a current of the motor, and as a result, it may be possible to prevent the decrease in lifetime due to the intensive use of some of the IGBTs of the inverter.

[0016] Fourth, it may be possible to delaminate the interface between the respective bonded parts more easily by cooling, by vibrating the cooled parts of the fuel cell stack and the peripheral system based on the vibration generated by the rotation of the rotor of the motor and the generation of torque. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and further features of the present invention will now be described in detail with reference to exemplary embodiments thereof illustrated in the accompanying drawings, which are given hereinafter for illustrative purposes only and are therefore not limitative of the present invention, and in which: Fig. 1 is an exemplary schematic diagram illustrating a strategy for cold starting by inducing an increase in the temperature of a fuel cell using self-heating of a fuel cell, according to an exemplary embodiment of the present invention; Fig. 2 is an exemplary configuration diagram illustrating a device for controlling the cold start of a fuel cell system according to an exemplary embodiment of the present invention; Fig. 3 and Fig. 4 are exemplary schematic diagrams illustrating angular rotation of a rotor of a motor and generating torque based on the angular rotation to describe a principle of controlling cold start of a fuel cell system according to an exemplary embodiment of the present invention; Fig. 5 is an exemplary flowchart illustrating a method for controlling a cold start of a fuel cell system according to an exemplary embodiment of the present invention; Fig. 6 is an exemplary graph illustrating a process of consuming and restoring power based on movement of a rotor while controlling cold start of the fuel cell system according to the exemplary embodiment of the present invention; Fig. 7 is an exemplary graph illustrating rotor torque of a motor and consumed DC power during cold start control of the fuel cell system according to the exemplary embodiment of the present invention; Fig. 8 is an exemplary circuit diagram of an inverter illustrating when some of the plurality of IGBTs of the inverter are used based on the cold start control of the existing fuel cell system, according to the prior art; and Fig. 9 is an exemplary circuit diagram of the inverter illustrating the plurality of IGBTs of the inverter that may be used based on the cold start control of the fuel cell system according to the exemplary embodiment of the present invention.

[0018] It should be understood that the attached drawings are not necessarily to scale, being a somewhat simplified representation of the various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein include, for example, specific dimensions, orientations, locations, and shapes, which will be determined in part by the particular intended application and usage environment. In the figures, reference numerals refer to the same or equivalent parts of the present invention throughout the several figures of the drawing. DETAILED DESCRIPTION

[0019] The term "vehicle" or "vehicle-like" or other similar term, as used herein, is intended to be inclusive of motor vehicles in general, such as passenger automobiles, sport utility vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft, a variety of boats and ships, aircraft, and the like, and to include hybrid vehicles, electric vehicles, internal combustion engines, plug-in hybrid-electric vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels derived from resources other than oil). As referred to herein, a hybrid vehicle is a vehicle that has two or more power sources, for example, both gasoline-powered and electric-powered vehicles.

[0020] Although the example embodiments are described using a plurality of units to perform the example process, it is understood that the example processes may also be performed by one or more modules. Additionally, the term controller / controller refers to a hardware device that includes a memory and a processor. The memory is configured to store the modules, and the processor is specifically configured to execute these modules to perform one or more processes, which are described further below.

[0021] Furthermore, the control logic of the present invention may be embedded as non-transitory computer-readable media on a computer-readable medium containing executable program instructions executed by a processor, controller, or the like. Examples of computer-readable media include, but are not limited to, ROM, RAM, compact disc (CD-ROMs), magnetic tapes, floppy disks, flash drives, smart cards, and optical data storage devices. The computer-readable recording medium may also be distributed among computer systems coupled to a network such that the computer-readable media is stored and executed in a distributed manner, e.g., through a telematics server or a controller area network (CAN).

[0022] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It is further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of the listed features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more related listed terms.

[0023] Unless specifically stated or obvious from the context, as used herein, the term "approximately" should be understood as within a range of normal tolerance in the art, for example, within 2 standard deviations of the mean. "Approximately" can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clearly indicated by the context, all values provided herein are modified with "approximately."

[0024] Reference will now be made in detail to various exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. While the invention will be described in connection with exemplary embodiments, it is to be understood that the present invention is not intended to limit the invention to these exemplary embodiments. On the contrary, the invention is intended to cover not only the exemplary embodiments, but also various alternatives, modifications, and other embodiments included within the scope of the disclosure.

[0025] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0026] With reference to Fig. 1, a fuel cell's output current may be consumed by various loads (e.g., HDC and BPCU, which may be a controller, a high-voltage battery, an air blower, a motor, an inverter, and the like) during a cold start condition, and thus self-heating of a stack may be induced. Therefore, in the exemplary embodiment of the present invention, the fuel cell system may utilize a substantial amount of fuel cell output current during the cold start condition to induce self-heating of the fuel cell and reduce the cold start time based on an increase in the fuel cell's temperature due to self-heating.

[0027] In other words, the exemplary embodiment of the present invention may be characterized in that a drive motor for the fuel cell system may be used as a fuel cell load during the cold start condition, and the drive motor may consume a substantial amount of the output current generated by the fuel cell stack to reduce the cold start time by increasing the temperature of the fuel cell based on the self-heating of the fuel cell stack. Accordingly, as in Fig. 2, a device for controlling a cold start of a fuel cell system may include: a fuel cell 30 configured to apply a current to a motor 10 during the cold start state of the fuel cell system, and a torque limiting part 20 configured to limit a torque generated when a rotor of the motor 10 rotates forward and backward based on application of the current.

[0028] Therefore, an output current of the fuel cell 30, i.e., direct current (DC) power, can be applied to the motor 10 by operating the inverter 12 during the cold start condition of the fuel cell. As described below, when the motor rotor is rotated (e.g., driven), the fuel cell output current consumption can be increased due to the power consumed. If the temperature of the fuel cell stack is increased based on the fuel cell output current consumption, the cold start condition of the fuel cell can be alleviated, and at the same time, the cold start time can be reduced.

[0029] Meanwhile, the torque limiting part 20 may be configured to interrupt the current driving of the motor due to the motor driving before the completion of the cold start by the torque generated while the rotor of the motor 10 is rotating. The torque limiting part 20 may be a P-stage pawl 22 of a reduction gear restrictively connected to an output shaft extending from the rotor of the motor 10 to a drive gear, and may be a hydraulic brake device configured to brake the drive gear connected to the rotor of the motor 10. The torque limiting part 20 may also be operated by a control member.

[0030] For reference, the fuel cell system can be driven by driving the motor based on the output current generated by the fuel cell stack, outputting power for reducing the gear based on the motor drive, performing appropriate shifting in the reduction gear, and applying the shifted power to the drive wheel. Therefore, when the output shaft of the motor is locked to prevent rotation (e.g., fixed) using the P-stage pawl 22 of the reduction gear, the torque based on the motor drive can be limited to a range in which actual driving is not performed.

[0031] A method for controlling a cold start according to an exemplary embodiment of the present invention based on the configuration will be described below. First, a principle of storing and recovering kinetic energy based on an angular rotation of the rotor of the engine will be explained with reference to Fig. 3 and Fig. 4 described.

[0032] When a magnitude of the fuel cell output current, i.e., a phase current, is applied to the motor while being kept substantially constant, as in Fig. 3, the rotor 12 of the motor 10 may be configured to vibrate while rotating within a predetermined angular range (e.g., +20° to -20° or +40° to -40°) to generate the torque, as shown in Fig. 4. When the forward and reverse rotation angle of the rotor ranges from approximately +20° to -20°, the generated torque can be approximately zero (0). When the generated torque is equal to or greater than +20°, a positive torque can be increased. When the generated torque is equal to or less than -20°, a negative torque can be generated. The angular range of the rotor from which the torque is output can be changed based on the motor configuration and the magnitude of the phase current.

[0033] Due to the rotor torque generation principle, when the rotor vibrates within, for example, a range of approximately +40° to -40°, torque is generated to cause the rotor to repeatedly rotate angularly in a forward (+) direction and a reverse (-) direction. Specifically, the rotor of the motor can be configured to consume the output current of the fuel cell and output power, as represented by the following Equation 1. Power=Torque×Rotational speed

[0034] Therefore, as in Fig. 6, during operation (e.g., motor driving) of the motor, the power consumption, which is a value obtained by multiplying a forward (+) rotational speed of the rotor by a positive (+) torque generated when the rotor rotates forward (+), can be generated, and the power consumption, which is a value obtained by multiplying a reverse (-) rotational speed of the rotor by a negative (-) torque generated when the rotor rotates backward (-), can be generated.

[0035] Furthermore, when negative (-) torque is generated during forward (+) rotation of the rotor, or forward (+) torque is generated during reverse (-) rotation of the rotor, power can be recovered through regenerative braking. Specifically, when power is applied from the inverter to the motor, power loss, defined as the sum of losses due to copper loss and iron loss of the motor, inverter loss, and the like, may be present. Therefore, a significant amount of energy may be consumed during power consumption, and a reduced amount of energy may be recovered during power recovery, allowing the motor to be used as a larger fuel cell load during motor driving than during regenerative braking.

[0036] Therefore, it may be possible to increase the output current amount of the fuel cell based on the consumption of kinetic energy of the rotor by allowing the rotor to be the fuel cell load, and reduce the cold start time by performing self-heating of the fuel cell stack based on the output current amount of the fuel cell by applying a current to the motor for driving the fuel cell system during the cold start state to generate the angular rotation and torque of the rotor.

[0037] Specifically, the method for controlling a cold start according to the exemplary embodiment of the present invention, based on the principle of storing and recovering kinetic energy based on the angular rotation of the rotor of the engine as described above, will be described below. First, the driver can operate the torque limiting part 20 in advance to interrupt the current driving due to the engine running before the cold start is completed by the torque generated while the rotor of the engine 10 is rotating.

[0038] For example, the driver can shift to the P-speed so that the P-speed pawl of the reduction gear is restrictively connected to the output shaft extending from the rotor to the drive wheel, limiting the angular rotation of the rotor to an angle within the engine's running range for driving. Alternatively, the driver can operate the hydraulic brake device of the drive wheel to restrict or throttle the motor's rotor connected to the drive wheel, thus limiting the angular rotation of the rotor to the angle within the engine's running range for driving.

[0039] Furthermore, the output current of the fuel cell can be applied to the motor by a cold start command from an upper controller, and the angular rotation of the motor can be repeatedly performed forward and backward within a predetermined angular range (e.g., within a range of approximately +40° to -40°) based on the current application. Accordingly, if the motor rotor rotates repeatedly at an angular angle, the output current consumption of the fuel cell can be continuously increased.In other words, when a current is applied from the inverter to the motor as described above, a power loss, which is defined as a sum of the loss based on the copper loss and iron loss of the motor, the loss of an inverter, and the like, may be present, and therefore, a larger amount of energy may be consumed during power consumption based on the angular rotation of the motor rotor, and a smaller amount of energy may be recovered during power recovery, which causes the output power consumption of the fuel cell to increase during motor running based on the angular rotation of the rotor of the motor.

[0040] In other words, as described above, when the output power consumption of the fuel cell is increased during motor driving of the motor, the power consumption, which is the value obtained by multiplying the forward (+) rotation speed of the rotor by the positive (+) torque generated when the rotor rotates forward (+), can be generated, and the power consumption, which is the value obtained by multiplying the reverse (-) rotation speed of the rotor by the negative (-) torque generated when the rotor rotates reversely (-), can be generated.

[0041] As in Fig. As shown in Figure 7, when cold start control according to the exemplary embodiment of the present invention is performed based on the principle of storing and recovering the kinetic energy of the rotor, it can be appreciated that the DC power consumption supplied by the fuel cell is further increased than when the copper loss of the stator is utilized. Specifically, when the cold start ends along with the release of the cold start state, the upper controller may be configured to release the cold state control and operate the motor to switch to the driving mode for the initial driving.

[0042] As described above, the output current of the fuel cell can be increased based on the consumption of kinetic energy of the motor rotor, and the self-heating of the fuel cell stack can be performed based on the increase in the output current of the fuel cell to significantly reduce the cold start time. However, if phase resistance heating of the motor is used within the existing cold start methods, since only a constant current is applied from the motor inverter to drive the rotor to the angle at which the rotor does not generate torque, as shown in Fig. As shown in Fig. 8, some of the plurality of IGBTs of the inverter, which is a type of control element that applies current to the motor, are used, so that the life and durability of the inverter may be reduced.

[0043] Furthermore, according to the exemplary embodiment of the present invention, since the rotor of the motor can be rotated forward and backward at a predetermined angle to generate a torque, as shown in Fig. 9, the plurality of IGBTs of the inverter, including the IGBT used during forward rotation, the IGBT used during reverse rotation, and the like, can be used uniformly, and thus, deterioration of the service life of the inverter can be prevented.

[0044] The invention has been described in detail with reference to exemplary embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made to these exemplary embodiments without departing from the principles of the invention.

[0045] The reference numbers listed in the drawings include reference to the following elements, as discussed below: 10 Engine 12 inverters 20 Torque limiting part 22 P-stage pawl of the reduction gear 30 fuel cells

Claims

[1] Device for controlling a cold start of a fuel cell system, comprising: a fuel cell (30) configured to supply current to a motor (10) during a cold start condition of the fuel cell system; and a torque limiting part (20) configured to limit a torque generated, when a rotor of the motor (10) rotates angularly forwards and backwards within a predetermined angular range based on an application of the current, wherein the output power consumption of the fuel cell (30) is increased due to the power consumed in the engine (10) during the cold start condition. [2] The device according to claim 1, wherein the torque limiting member is a parking stage pawl (22) of a reduction gear restrictively attached to an output shaft extending from the rotor of the motor (10) to a drive wheel. [3] The device according to claim 1, wherein the torque limiting member is a hydraulic braking device of the drive wheel. [4] A method for controlling a cold start of a fuel cell system, comprising: Applying, by a control element, an output current of a fuel cell (30) to a motor (10) during a cold start condition of the fuel cell system; Increasing, by the control element, the output current consumption of the fuel cell (30) by angularly rotating a rotor of the motor (10) forward and backward within a predetermined angular range based on an application of the current; and Limiting, by the control element, a torque which is generated when the rotor of the motor (10) rotates angularly. [5] The method according to claim 4, wherein in increasing the output power consumption of the fuel cell (30) during operation of the engine (10), the power consumption which is a value obtained by multiplying a forward (+) rotational speed of the rotor by a positive (+) torque generated when the rotor rotates forward (+) is generated, and the power consumption which is a value obtained by multiplying a reverse (-) rotational speed of the rotor by a negative (-) torque generated when the rotor rotates reversely (-) is generated. [6] The method of claim 4, wherein in limiting the torque, switching to a park stage pawl (22) is performed to restrictively attach a park stage pawl (22) of a reduction gear to an output shaft from the rotor to a drive wheel. [7] The method of claim 4, wherein limiting the torque comprises operating a hydraulic braking device of a drive wheel to limit the drive wheel connected to the rotor via an output shaft. [8] The method according to claim 4, wherein the output current of the fuel cell (30) is applied to the motor (10) by a cold start command of an upper control member, and the angular rotation is repeatedly performed forward and backward within the predetermined angular range of the motor (10) based on the application of the current.

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