Fuel cell vehicle, method of controlling startup thereof, and recording medium

Abstract

The invention relates to a fuel cell vehicle, a method of controlling startup thereof, and a recording medium. A fuel cell vehicle includes a cell and a cell stack including a plurality of unit cells stacked on top of each other. The fuel cell vehicle also includes a boost converter configured to boost and output a target voltage received from the stack in response to the switching signal. The fuel cell vehicle also includes a switching unit configured to be switched to connect the output side of the boost converter to the battery in response to the control signal. The fuel cell vehicle also includes a controller configured to generate a control signal upon request to start the fuel cell vehicle. The controller is further configured to vary a switching frequency of the switching signal in response to a difference between a first voltage output from the stack and a second voltage of the cell.

Description

Technical Field

[0001] The present disclosure relates to a fuel cell vehicle, a method of controlling startup thereof, and a recording medium storing a program for executing the method. Background Art

[0002] In a vehicle equipped with a fuel cell including a battery stack, a battery or a super capacitor is charged with power generated in the fuel cell. A load of the fuel cell vehicle, such as a motor, is driven using power stored in the battery or the super capacitor.

[0003] Generally, a fuel cell vehicle includes a boost converter that boosts a stack voltage generated in a fuel cell and a battery. When a voltage difference between an input side of the boost converter and an output side of the boost converter is small, an overcurrent may result, which may damage the boost converter. Summary of the invention

[0004] Accordingly, embodiments of the present disclosure provide a fuel cell vehicle, a method of controlling startup thereof, and a recording medium storing a program for executing the method that substantially obviate one or more problems due to limitations and disadvantages of the related art.

[0005] Embodiments of the present disclosure provide a fuel cell vehicle capable of normally achieving its startup using only one boost converter, a method of controlling its startup, and a recording medium storing a program for executing the method.

[0006] The objectives achieved by the embodiments of the present disclosure are not limited to the above objectives. A person skilled in the art should more clearly understand other objectives not mentioned herein from the following description.

[0007] Other advantages, purposes and features of the present disclosure are partially described in the following description, and those skilled in the art should partially understand other advantages, purposes and features of the present disclosure from the following description, or can understand other advantages, purposes and features of the present disclosure from the practice of the present disclosure. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and its claims and the drawings.

[0008] According to an embodiment, a fuel cell vehicle is provided. The fuel cell vehicle includes a battery and a battery stack, the battery stack including a plurality of unit cells stacked one above the other. The fuel cell vehicle also includes a boost converter, which is configured to increase and output a target voltage received from the battery stack in response to a switching signal. The fuel cell vehicle also includes a switching unit, which is configured to be switched in response to a control signal to connect the output side of the boost converter to the battery. The fuel cell vehicle further includes a controller, which is configured to generate a control signal when a fuel cell vehicle is requested to be started. The controller is also configured to change the switching frequency of the switching signal in response to the difference between the first voltage output from the battery stack and the second voltage of the battery.

[0009] In an embodiment, the fuel cell vehicle may further include a load configured to be connected to the output side of the boost converter through a switching operation of the switching unit.

[0010] In an embodiment, the fuel cell vehicle may further include a peripheral auxiliary device configured to be connected to the output side of the boost converter through a switching operation of the switching unit.

[0011] In an embodiment, the controller may be configured to reduce the switching frequency when the sum of the first voltage and the minimum duty cycle voltage is equal to or greater than the second voltage. The controller may also be configured to reduce the switching frequency until the sum of the minimum duty cycle voltage corresponding to the reduced switching frequency and the first voltage becomes less than the second voltage.

[0012] In an embodiment, the controller may be configured to restore the reduced switching frequency when a sum of a minimum duty cycle voltage corresponding to the switching frequency before reduction and the first voltage becomes smaller than the second voltage.

[0013] In an embodiment, the minimum duty cycle voltage may be calculated as follows:

[0014]

[0015] Wherein, VDMIN represents the minimum duty cycle voltage, VIMAX represents the maximum value of the first voltage, and DMIN represents the minimum duty cycle.

[0016] In an embodiment, the minimum duty cycle may be calculated according to the following formula:

[0017] ,

[0018] Wherein, T represents the minimum delay time of the boost converter, and F represents the switching frequency.

[0019] In an embodiment, the controller may be configured to generate the switching signal in a pulse width modulation manner.

[0020] In an embodiment, the boost converter may include a first capacitor connected between a first output terminal on the positive side of the battery stack and a second output terminal on the negative side of the battery stack. The boost converter may also include an inductor, the inductor including one end connected to the first output terminal. The boost converter may further include a diode including an anode connected to the other end of the inductor. The boost converter may further include a second capacitor arranged between the cathode of the diode and the second output terminal. The boost converter may further include a semiconductor switch configured to be switched in response to a switching signal and connected between the anode of the diode and the second output terminal.

[0021] In an embodiment, T may correspond to the on-time of the semiconductor switch.

[0022] According to another embodiment, a method for controlling the start of a fuel cell vehicle is provided. The fuel cell vehicle includes: a battery; a battery stack including a plurality of unit cells stacked one above the other; and a boost converter configured to increase and output a target voltage received from the battery stack in response to a switching signal. The method includes: when a fuel cell vehicle is requested to be started, connecting the output side of the boost converter to the battery. The method also includes operating the boost converter to receive the target voltage from the battery stack. The method also includes adjusting the switching frequency of the switching signal in response to a difference between a first voltage output from the battery stack and a second voltage of the battery.

[0023] In an embodiment, adjusting the switching frequency may include: when a sum of the first voltage and the minimum duty cycle voltage is equal to or greater than the second voltage, reducing the switching frequency until the sum becomes less than the second voltage.

[0024] In an embodiment, the method may further include receiving a target voltage through a boost converter when the sum of a minimum duty cycle voltage corresponding to the reduced switching frequency and the first voltage becomes less than a second voltage. The method may further include restoring the reduced switching frequency when the sum of a minimum duty cycle voltage corresponding to the switching frequency before the reduction and the first voltage becomes less than the second voltage. The method may additionally include receiving a target voltage from a battery stack by a boost converter.

[0025] According to another embodiment, a recording medium storing a program is provided. The program can be configured to execute a method for controlling the start-up of a fuel cell vehicle, the fuel cell vehicle comprising: a battery; a battery stack comprising a plurality of unit cells stacked one above the other; and a boost converter configured to increase and output a target voltage received from the battery stack in response to a switching signal. When the program is executed by one or more processors, the one or more processors can implement a function of connecting the output side of the boost converter to the battery when requesting the start-up of the fuel cell vehicle, a function of operating the boost converter to receive a target voltage from the battery stack, and a function of adjusting the switching frequency of the switching signal in response to the difference between a first voltage output from the battery stack and a second voltage of the battery.

[0026] It should be understood that the above general description and the following detailed description of the present disclosure are illustrative and explanatory.The above general description and the following detailed description of embodiments of the present disclosure are intended to provide further explanation of the present disclosure as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are included to enable a further understanding of the embodiments of the present disclosure, and are incorporated in and constitute a part of this application. The accompanying drawings illustrate embodiments of the present disclosure and together with the description serve to explain the principles of the present disclosure. In the drawings:

[0028] Figure 1 is a block diagram of a fuel cell vehicle according to an embodiment;

[0029] Figure 2 yes Figure 1 A circuit diagram of an embodiment of a boost converter is shown;

[0030] Figure 3 is a flowchart for explaining a startup control method according to an embodiment; and

[0031] Figure 4 is a block diagram of a fuel cell vehicle according to a comparative example. DETAILED DESCRIPTION

[0032] The present disclosure is described more fully below with reference to the accompanying drawings, in which various embodiments are shown. However, embodiments may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to make the present disclosure more thorough and complete and to more fully convey the scope of the present disclosure to those of ordinary skill in the art.

[0033] It will be understood that when an element is referred to as being 'on' or "under" another element, it can be directly on / under the other element, and one or more intervening elements may also be present.

[0034] When an element is referred to as being “on” or “under”, it can mean “under the element” as well as “on the element” depending on the situation, depending on the element.

[0035] Furthermore, relational terms, such as “first,” “second,” “on / upper,” and “lower / lower,” are used merely to distinguish one object or element from another object or element without necessarily requiring or relating to any physical or logical relationship or sequence between the objects or elements.

[0036] When a component, device, element, etc. of the present disclosure is described as having a purpose or performing an operation, function, etc., the component, device, or element should be considered herein as being “configured to” satisfy the purpose or perform the operation or function.

[0037] Hereinafter, a vehicle including a fuel cell (sometimes referred to herein as a “fuel cell vehicle”) according to an embodiment is described with reference to the accompanying drawings.

[0038] Figure 1 is a block diagram of a fuel cell vehicle 100 according to an embodiment.

[0039] The fuel cell vehicle 100 may include a battery stack 110, a boost converter 120, a battery (or a high voltage battery) 130, a switching unit 150, and a controller 180. The fuel cell vehicle 100 may further include a load 170. In addition, the fuel cell vehicle 100 may include peripheral auxiliary equipment (balance of plant (BOP)) 140.

[0040] Examples of fuel cells that may be included in the fuel cell vehicle 100 according to an embodiment are briefly described below. However, the present disclosure is not limited to any specific form of fuel cell included in the fuel cell vehicle 100.

[0041] The fuel cell may be a polymer electrolyte membrane fuel cell (or proton exchange membrane fuel cell) (PEMFC), which has been most widely studied as a power source for driving a vehicle. The fuel cell may include a cell stack 110 .

[0042] The battery stack 110 may include a plurality of unit cells. The plurality of unit cells may be stacked on each other in a first direction. The number of unit cells may be determined according to the intensity of power generated in the fuel cell.

[0043] The first direction may be, for example, a traveling direction of the fuel cell vehicle 100. As another embodiment, the first direction may be a direction intersecting with the traveling direction of the fuel cell vehicle 100.

[0044] The voltage VS (hereinafter referred to as “stack voltage” or “first voltage”) generated and output from the battery stack 110 corresponds to the potential difference between the output terminal PO (hereinafter referred to as “first output terminal”) on the positive side of the battery stack 110 and the output terminal NO (hereinafter referred to as “second output terminal”) on the negative side of the battery stack 110.

[0045] The boost converter 120 may be a DC / DC converter that converts a DC input voltage into a DC output voltage having a higher level than the DC input voltage. The boost converter 120 may increase the output from the battery stack 110 and may output the output. For example, the output voltage VO of the boost converter 120 may be expressed using the following equation 1.

[0046] [Equation 1]

[0047] VO = VI × R

[0048] In Equation 1, VI represents an input voltage of the boost converter 120 , and R represents a boost ratio of the boost converter 120 .

[0049] In Equation 1, the output voltage VO is a fixed value. Therefore, when the input voltage VI decreases, the boost ratio R increases, and when the input voltage VI increases, the boost ratio R decreases.

[0050] For example, see Figure 1 , the boost converter 120 may receive the target voltage VT from the battery stack 110. The boost converter 120 may increase and output the target voltage VT received from the battery stack 110. As used herein, extracting the target voltage VT may mean extracting an amount of energy equal to the target voltage. In an embodiment, extracting the target voltage VT may refer to Figure 3 , as described in more detail below. In one embodiment, the boost converter 120 may continuously extract energy from the battery stack 110 until an amount of energy equal to the target voltage VT is input from the battery stack 110 to the boost converter 120. Here, the target voltage VT may be a voltage on the input side of the boost converter 120. The boost converter 120 may extract an amount of energy equal to the target voltage VT from the battery stack 110 in response to a switching signal SC output from the controller 180. The voltage output from the boost converter 120 corresponds to the potential difference between the output terminal P1 on its positive side (hereinafter referred to as the "third output terminal") and the output terminal N1 on its negative side (hereinafter referred to as the "fourth output terminal").

[0051] The battery stack 110 may be a passive device that provides an amount of energy equal to the target voltage VT required by the boost converter 120 when requested by the boost converter 120 .

[0052] However, the present disclosure is not limited to any particular operation of boost converter 120. In various embodiments, Figure 1 The illustrated boost converter 120 may perform a function corresponding to a DC / DC converter generally used in a fuel cell vehicle.

[0053] Figure 2 yes Figure 1 A circuit diagram of an embodiment of a boost converter 120 is shown.

[0054] Figure 1 The boost converter 120 shown is not limited to Figure 2 The embodiment shown.

[0055] Figure 2 The illustrated boost converter 120 may include first and second capacitors CA1 and CA2 , an inductor L, a diode D, and a semiconductor switch SS.

[0056] The first capacitor CA1 may be disposed between a first output terminal PO of the battery stack 110 and a second output terminal NO of the battery stack 110 .

[0057] The inductor L includes one end connected to the first output terminal PO of the battery stack 110 and the other end connected to the anode or positive electrode of the diode D. Therefore, the inductor L is disposed between the first output terminal PO of the battery stack 110 and the anode or positive electrode of the diode D.

[0058] The diode D includes a positive electrode or anode connected to the other end of the inductor L.

[0059] The second capacitor CA2 may be disposed between a negative electrode or cathode of the diode D and a second output terminal NO of the battery stack 110 .

[0060] The first capacitor CA1 and the second capacitor CA2 are smoothing capacitors.

[0061] The semiconductor switch SS may be turned on (or conducted) or off (or cut off) in response to the switching signal SC, and may be connected between the positive electrode or anode of the diode D and the second output terminal NO of the battery stack 110 .

[0062] The semiconductor switch SS may be implemented as an insulated gate bipolar transistor (IGBT) or a field effect transistor (FET). Figure 2 As shown, the semiconductor switch SS may be implemented as a transistor, which may include a gate G connected to the switching signal SC, a drain D connected to the anode or positive electrode of the diode D, and a source S connected to the second output terminal NO of the battery stack 110 .

[0063] The operation of the boost converter configured as described above according to an embodiment is described in more detail below.

[0064] The transistor as the semiconductor switch SS may be turned on in response to the switching signal SC output from the controller 180. The transistor may receive a target voltage from the battery stack 110. Receiving the target voltage may mean receiving an amount of energy equal to the target voltage.

[0065] The battery stack 110 may be used to generate main power required for the fuel cell vehicle 100. In addition, the battery 130 may be used to generate auxiliary power required for the fuel cell vehicle 100. Therefore, energy stored in the battery 130 may be provided to the load 170 as auxiliary power.

[0066] The switching unit 150 includes one side connected to the boost converter 120 and the other side connected to the battery 130. The switching unit 150 is turned on (or turned on) or off (or cut off) in response to the control signals C1 and C2. When the switching unit 150 is turned on, the output side of the boost converter 120 can be connected to the battery 130, the load 170, and the peripheral auxiliary device 140.

[0067] In an embodiment, the switching unit 150 may include a first switch 152 and a second switch 154. The first switch 152 is connected between the third output terminal P1 on the positive side of the boost converter 120 and the input terminal on the positive side of the battery 130. The first switch 152 performs a switching operation in response to a first control signal C1. The second switch 154 is connected between the fourth output terminal N1 on the negative side of the boost converter 120 and the input terminal on the negative side of the battery 130. The second switch 154 performs a switching operation in response to a second control signal C2. The first control signal C1 and the second control signal C2 may be generated in the controller 180.

[0068] According to an embodiment, when starting the vehicle is requested, the controller 180 may generate the first and second control signals C1 and C2 to turn on the first and second switches 152 and 154 of the switching unit 150 to connect the output side of the boost converter 120 to the battery 130 .

[0069] In an embodiment, the controller 180 determines whether to request to start the fuel cell vehicle 100 through the input terminal IN1. For example, a start command may be provided to the controller 180 through the input terminal IN1. In an embodiment, when a user desires to start the fuel cell vehicle 100, a start command may be generated in an interface (not shown) that may be operated by the user. The generated start command may be provided to the controller 180.

[0070] In addition, when the fuel cell vehicle 100 is requested to be started, the controller 180 may generate a switching signal SC to operate the boost converter 120. According to an embodiment, when the fuel cell vehicle is requested to be started, the controller 180 may change a switching frequency F of the switching signal SC in response to a difference between a first voltage VS output from the battery stack 110 and a voltage of the battery 130 (hereinafter referred to as a "second voltage").

[0071] According to an embodiment, the controller 180 may generate the switching signal SC using a pulse width modulation (PWM) method. For example, the controller 180 may adjust the on-time T of the semiconductor switch SS using the PWM method to adjust the duty cycle (ie, the width of the pulse) to control the output amount from the boost converter 120.

[0072] If the switching signal SC is generated using a pulse frequency modulation (PFM) method instead of a PWM method, in order to control the output amount of the boost converter 120 , the efficiency in a high load state may be improved.

[0073] However, it is necessary to additionally provide a component for implementing the PFM method in order to convert an operation using the PWM method into an operation using the PFM method. Therefore, according to an embodiment, the PWM method is used to generate the switching signal SC.

[0074] Hereinafter, the switching frequency F before the change is referred to as the "first switching frequency F1" or the "basic switching frequency". In addition, the changed switching frequency F2 is referred to as the "second switching frequency F2" or the "variable switching frequency". In addition, the minimum duty cycle voltage VDMIN corresponding to the first switching frequency F1 is referred to as the "first minimum duty cycle voltage". In addition, the minimum duty cycle voltage VDMIN corresponding to the second switching frequency F2 is referred to as the "second minimum duty cycle voltage". In addition, the sum of the first minimum duty cycle voltage and the first voltage VS is referred to as the "first sum S". In addition, the sum of the second minimum duty cycle voltage and the first voltage VS is referred to as the "second sum S'".

[0075] When the first sum S is equal to or greater than the second voltage, the controller 180 may reduce the first switching frequency and may output a switching signal SC having a second switching frequency as the reduced switching frequency. In an embodiment, the controller 180 may reduce the switching frequency until the second sum S' becomes less than the second voltage.

[0076] The minimum duty cycle voltage can be expressed using Equation 2 below.

[0077] [Equation 2]

[0078]

[0079] In Equation 2, VDMIN represents a minimum duty cycle voltage, VIMAX represents a maximum value of the first voltage VS, and DMIN represents a minimum duty cycle.

[0080] The boost converter 120 may have a minimum duty cycle due to hardware design limitations. The minimum duty cycle may be generated due to the delay time of the semiconductor switch SS. In this case, the minimum duty cycle can be expressed using the following equation 3.

[0081] [Equation 3]

[0082]

[0083] In Equation 3, T represents the minimum delay time (or switching delay time) of the semiconductor switch SS included in the boost converter 120, and F represents the switching frequency. The unit of DMIN is percentage (%). Figure 2 In the illustrated implementation of the boost converter 120 , T may correspond to the on-time of the semiconductor switch SS. The minimum duty cycle may correspond to the minimum duty cycle of the pulse width modulation signal that operates the boost converter 120 .

[0084] If the boost converter 120 is operated at a minimum duty cycle or a smaller duty cycle, a large amount of noise may be generated due to the switching delay time T. Such noise may cause abnormal operation of the boost converter 120. In addition, the duty cycle of the boost converter 120 has the following relationship with the boost ratio R: the lower the duty cycle, the lower the boost ratio R of the boost converter 120. Therefore, when the difference between the input voltage VI and the output voltage VO of the boost converter 120 is small, the voltage to be increased is reduced. Therefore, the boost converter 120 may not be able to operate normally at the minimum duty cycle or a smaller duty cycle. Therefore, according to an embodiment, the switching frequency is temporarily reduced in order to reduce the minimum duty cycle.

[0085] Hereinafter, the minimum duty ratio obtained by substituting the first switching frequency F1 into Equation 3 is referred to as a “first minimum duty ratio.” Furthermore, the minimum duty ratio obtained by substituting the second switching frequency F2 into Equation 3 is referred to as a “second minimum duty ratio.”

[0086] First, when the first sum S is equal to or greater than the second voltage, the controller 180 reduces the switching frequency F. For example, the controller 180 reduces the frequency of the switching signal SC from the first switching frequency F1 to the second switching frequency F2.

[0087] Thereafter, when the second sum S′ becomes smaller than the second voltage, the reduced second switching frequency is restored (or returned) to the first switching frequency F1.

[0088] The controller 180 may receive the first voltage VS or a value for calculating the first voltage VS through the input terminal IN2. The controller 180 may also receive the second voltage or a value for calculating the second voltage through the input terminal IN3.

[0089] In an embodiment, after the startup is completed, the switching unit 150 remains in the on state. Therefore, the output from the boost converter 120 can be provided to the load 170, the battery 130, or the peripheral auxiliary device 140 that assists the operation of the battery stack 110 (e.g., necessary for driving the battery stack 110). The peripheral auxiliary device 140 can be connected to the output side of the boost converter 120 through the switching operation of the switching unit 150.

[0090] The load 170 may be connected to the main path formed by the switching unit 150 to receive the output from the boost converter 120. For example, the load 170 may be connected to the output side of the boost converter 120 by the switching operation of the switching unit 150. Alternatively, the load 170 may receive the second voltage charged in the battery 130 regardless of whether the switching unit 150 forms the main path.

[0091] In an embodiment, the load 170 may include an inverter (not shown) and a motor (not shown).

[0092] The inverter may be connected to the third output terminal P1 and the fourth output terminal N1 of the boost converter 120. The inverter may convert the received DC type voltage or the DC type second voltage stored in the battery 130 into an AC type voltage according to the driving state of the fuel cell vehicle 100, and may output the AC type voltage to the motor.

[0093] The motor may be driven in response to an AC type voltage output from the inverter. For example, the motor may rotate when receiving an AC voltage for the motor from the inverter, and thus may be used to drive the fuel cell vehicle 100. In an embodiment, the motor may be a three-phase AC rotating device including a rotor embedded with a permanent magnet. However, the present disclosure is not limited to any particular form of motor.

[0094] In addition, although not shown, the load 170 of the fuel cell vehicle 100 may include components necessary for driving the vehicle, such as a motor driven power steering (MDPS) device, a radiator fan, and a headlight. These various components included in the load 170 may be driven while receiving the voltage output from the boost converter 120 or the second voltage stored in the battery 130 as a driving voltage.

[0095] In the following, reference Figure 1 and Figure 3 A method of controlling the start-up of a fuel cell vehicle according to an embodiment is described. However, the present disclosure is not limited to Figure 1and Figure 3 The content shown in .

[0096] In addition, according to Figure 3 The startup control method 200 of the embodiment shown in FIG. Figure 1 However, the present disclosure is not limited thereto. For example, according to another embodiment, the fuel cell vehicle 100 shown in FIG. Figure 1 The fuel cell vehicle 100 shown in FIG. 1 is a fuel cell vehicle configured to perform various operations according to Figure 3 The startup control method 200 of the embodiment shown in FIG.

[0097] In an embodiment, Figure 1 The fuel cell vehicle 100 (eg, the controller 180) shown in FIG. 1 may execute the following Figure 3 The startup control method 200 of the embodiment shown in FIG. However, the present disclosure is not limited thereto. For example, according to another embodiment, Figure 1 The fuel cell vehicle 100 shown in FIG. 1 may perform the same operation as described above. Figure 3 The startup control method 200 of the embodiment shown in FIG. 1 is a startup control method configured differently.

[0098] Figure 3 is a flow chart of a startup control method 200 according to an embodiment.

[0099] In step or operation 210 , it is determined whether a start-up of the fuel cell vehicle 100 is requested.

[0100] When the fuel cell vehicle 100 is requested to start, the boost converter 120 is connected to the battery 130 in step or operation 212. In an embodiment, to connect the boost converter 120 to the battery 130, the controller 180 may turn on the switching unit 150 using the first control signal C1 and the second control signal C2.

[0101] In step or operation 214 , the controller 180 generates a switching signal SC to operate the boost converter 120 .

[0102] In step or operation 216, the controller 180 controls the boost converter 120 to follow the target voltage command. For example, under the control of the controller 180, the boost converter 120 may receive the target voltage VT from the battery stack 110, may boost the target voltage, and may output the boosted target voltage. To perform step or operation 216, the switching signal SC output from the controller 180 to the boost converter 120 has a first switching frequency.

[0103] In steps or operations 218 and 220 , the controller 180 adjusts the switching frequency of the switching signal SC in response to a difference between the first voltage VS output from the battery stack 110 and the second voltage of the battery 130 .

[0104] For example, in step or operation 218, the controller 180 determines whether the first sum S of the first voltage and the first minimum duty cycle voltage is equal to or greater than the second voltage. When the first sum S is not equal to or greater than the second voltage, the controller 180 proceeds to step or operation 216 to follow the target voltage command.

[0105] On the other hand, when the first voltage S is equal to or greater than the second voltage, it becomes difficult for the boost converter 120 to operate normally. Therefore, the switching frequency of the switching signal SC is adjusted in step or operation 220. For example, the minimum duty cycle can be reduced by reducing the switching frequency, and the minimum duty cycle voltage can be reduced by reducing the minimum duty cycle.

[0106] In the fuel cell vehicle 100, the battery stack 110 and the battery 130 have different voltage ranges from each other. Thus, the boost converter 120 is used. In a specific case such as cold shutdown (CSD), the voltage difference between the battery stack 110 and the battery 130 may be less than the minimum duty cycle voltage VDMIN of the boost converter 120 expressed using the above equation 2. In this case, the switching noise of the boost converter 120 may become serious, which may cause abnormal operation of the boost converter 120. Therefore, in order to avoid this problem, in the case where the difference between the input voltage VI and the output voltage VO of the boost converter 120 is small, for example, in the case where the first and S are equal to or greater than the second voltage V2, the switching frequency F shown in the above equation 3 is temporarily reduced from the first switching frequency to the second switching frequency. When the switching frequency F decreases, as shown in the above equation 3, the minimum duty cycle DMIN decreases. In addition, when the minimum duty cycle DMIN decreases, the minimum duty cycle voltage VDMIN decreases, as shown in the above equation 2. Therefore, the boost converter 120 can operate normally.

[0107] The above-mentioned CSD may refer to safely stopping (S / D) the operation of the fuel cell system including the battery stack 110 by using additional after-treatment of the compressor to prevent the problem of internal condensed water freezing when the fuel cell vehicle is stopped in a cold shutdown situation.

[0108] In step or operation 222, the controller 180 determines whether the second sum S' is less than the second voltage. When the second sum S' is not less than the second voltage, the controller 180 proceeds to step or operation 220 to further reduce the switching frequency. Therefore, the controller 180 reduces the switching frequency until the second sum S' becomes less than the second voltage.

[0109] When the second sum S' is less than the second voltage, the controller 180 controls the boost converter 120 to follow the target voltage command in step or operation 224. To perform step or operation 224, the switching signal SC output to the boost converter 120 has a second switching frequency.

[0110] In step or operation 226 , the controller 180 determines whether the first sum S is less than the second voltage V2 . When the first sum S is not less than (ie, greater than or equal to) the second voltage V2 , the process proceeds to step or operation 224 .

[0111] On the other hand, when the first sum S is less than the second voltage V2, the controller 180 restores the switching frequency in step or operation 228. For example, the controller 180 restores the switching frequency in a manner of increasing the switching frequency from the second switching frequency to the first switching frequency.

[0112] In an embodiment, the reason for restoring the switching frequency is to enable the boost converter 120 to operate at a switching frequency as high as possible because the efficiency of the boost converter 120 decreases in a high load region at a low switching frequency.

[0113] In step or operation 230, the controller 180 controls the boost converter 120 to follow the target voltage command to complete startup. To perform step or operation 230, the switching signal SC output to the boost converter 120 has a first switching frequency.

[0114] Even after the startup is completed, the switching unit 150 may be maintained in the on state, and thus, the output from the boost converter 120 may be provided to the load 170 .

[0115] In the following, in order to better understand Figure 3 The method 200 shown in , provides an example, wherein the first voltage VS of the battery stack 110 is 350 V to 600 V, the second voltage is 630 V to 800 V, the first switching frequency is 25 kHz, the first minimum duty cycle at the first switching frequency is 10%, the switching delay time T is 4 milliseconds (ms), and the second switching frequency is 10 kilohertz (kHz).

[0116] When these conditions are substituted into Equation 2, the first minimum duty cycle voltage at the first switching frequency is calculated to be 66.66V, as shown in Equation 4 below.

[0117] [Equation 4]

[0118] VDMIN = maximum value of the first voltage × first minimum duty cycle / (1-first minimum duty cycle) = 600 × 0.1 / (1- 0.1) = 600 × 0.1 / 0.9

[0119] Therefore, the minimum value of the second voltage for normal operation of boost converter 120 is expressed using Equation 5 below.

[0120] [Equation 5]

[0121] Second voltage = first voltage + minimum duty cycle voltage = 600 + 66.66 = 666.66

[0122] Taking the margin into consideration, the minimum value of the second voltage needs to be 670 V or higher.

[0123] In this case, according to an embodiment, when the second voltage becomes below 670 V in step 218, the first switching frequency of 25 kHz is reduced to the second switching frequency of 10 kHz. Therefore, the first minimum duty cycle is reduced to 4% of the second minimum duty cycle, as shown in Equation 6 below.

[0124] [Equation 6]

[0125]

[0126] If the second minimum duty ratio obtained by the above Equation 6 is substituted into the above Equation 2, the second minimum duty ratio voltage is calculated to have a reduced value of 25V as shown in the following Equation 7.

[0127] [Equation 7]

[0128]

[0129] Therefore, the minimum value of the second voltage obtained by the above Equation 5 is reduced to 625 V as shown in the following Equation 8.

[0130] [Equation 8]

[0131] Second voltage = first voltage + second minimum duty cycle voltage = 600 + 25 = 625

[0132] See again Figure 1 In various embodiments, the fuel cell vehicle 100 may include various types of electronic control units (ECUs). Each ECU is a type of computer that stores software for implementing various functions of the fuel cell vehicle 100. The ECU may perform functions such as Figure 3 The startup control method 200 is a startup control method.

[0133] A computer-readable recording medium having recorded thereon a program for executing the start control method 200 performed by the fuel cell vehicle 100 may store the following program: when executed by one or more processors, the one or more processors are caused to implement a function of connecting the output side of the boost converter 120 to the battery 130 when the fuel cell vehicle 100 is requested to be started, a function of operating the boost converter 120 to receive a target voltage from the battery stack 110, and a function of adjusting a switching frequency of a switching signal in response to a difference between a first voltage output from the battery stack 110 and a second voltage of the battery 130. The computer-readable recording medium may be read by a computer system including one or more processors.

[0134] The computer-readable recording medium may include various types of storage devices that store data that can be read by a computer system. Examples of computer-readable recording media may include ROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical data storage devices. The computer-readable recording medium may also be distributed on a network-coupled computer system, thereby storing and executing computer-readable code in a distributed manner. In addition, a person of ordinary skill in the art to which the present disclosure belongs may understand the functional program, code, and code segment for implementing the startup control method of the present disclosure.

[0135] Hereinafter, a fuel cell vehicle according to a comparative example and a fuel cell vehicle according to an embodiment of the present disclosure are described.

[0136] Figure 4 is a block diagram of a fuel cell vehicle according to a comparative example.

[0137] The fuel cell vehicle according to the comparative example includes a battery stack 10, a boost converter 20, a load 70, a super capacitor 30, an initial charging converter 40, and a first switching unit 50 and a second switching unit 52. The battery stack 10, the boost converter 20, the super capacitor 30 and the load 70 can generally perform the same Figure 1 The battery stack 110 , boost converter 120 , battery 130 , and load 170 shown have the same functionality.

[0138] according to Figure 4 The fuel cell vehicle of the illustrated comparative example uses two converters 20 and 40 to reduce the time taken to satisfy the conditions for normal operation of boost converter 20 .

[0139] To this end, the initial charging converter 40 first operates to charge the voltage of the battery stack 10 to the supercapacitor 30. When the voltage charged in the supercapacitor 30 becomes greater than the voltage of the battery stack 10, the boost converter 20 immediately operates during the operation of the initial charging converter 40, thereby solving the problem of the minimum duty cycle.

[0140] However, according to the fuel cell vehicle of the comparative example, there is a problem in that two converters 20 and 40 are required.

[0141] In contrast, in the fuel cell vehicle 100 according to the embodiment, when the difference between the input voltage VI and the output voltage VO of the boost converter 120 is small, the switching frequency of the boost converter 120 is temporarily reduced to reduce the minimum duty ratio, thereby solving the situation where the difference between the first voltage and the second voltage is small using one boost converter 120. In other words, according to the embodiment, when the difference between the input voltage VI and the output voltage VO of the boost converter 120 is small, the switching frequency is changed to reduce the minimum duty ratio so that the boost converter 120 operates normally.

[0142] Theoretically, the boost converter 120 does not have a minimum duty cycle. However, the semiconductor element SS included in the actual boost converter 120 has a switching time when the semiconductor element SS is switched on between the on state and the off state. During the switching time, the boost converter 120 does not perform any other operation. This time is the switching delay time T. In other words, during the switch on / off period, the boost converter 120 cannot execute a new instruction. Therefore, as shown in Equation 3 of the boost converter 120, the switching delay time T is reflected in the minimum duty cycle. Therefore, in the case where the operation of the boost converter 120 is not feasible due to the limitation of the hardware (H / W) in the area of ​​the minimum duty cycle or lower, the embodiments of the present disclosure can be implemented by Figure 3 The method 200 shown in FIG. 2 overcomes the limitations of hardware.

[0143] As a result, according to an embodiment, the operation of the boost converter 120 is possible even when the difference between the first voltage and the second voltage is small. In addition, in special cases such as cold shutdown (CSD), the boost converter 120 may be used without considering the voltage difference.

[0144] As described above, the minimum value of the second voltage for normal operation of boost converter 120 may be 666.66 V. However, if the second voltage becomes lower than 666.66 V, boost converter 120 may not operate normally due to the limitation on the first minimum duty ratio caused by switching delay time T. Therefore, in order to maintain the voltage on the upstream side of the additional converter to be less than or equal to the first sum S, an additional converter needs to be provided on the downstream side of boost converter 120 or the upstream side of battery 130.

[0145] For example, Figure 4 As shown, the initial charging converter 40 may be placed on the upstream side of the supercapacitor 30. The initial charging converter 40 has the following two operation modes.

[0146] First, when the second voltage is 666.66 V or higher, initial charge converter 40 is maintained in a standby state while changing the power output from battery stack 10. Next, when the second voltage becomes lower than 666.66 V, initial charge converter 40 starts operating to maintain the voltage between boost converter 20 and initial charge converter 40 at 666.66 V or higher. To this end, the switching operations of first switching unit 52 and second switching unit 54 may be controlled.

[0147] In contrast, according to an embodiment of the present disclosure, when the minimum value of the second voltage is 666.66 V as described above, the switching frequency is changed to the second switching frequency to reduce the minimum value of the second voltage to 625 V, with the result that the boost converter 120 can always operate normally.

[0148] As is apparent from the above description, in a fuel cell vehicle, a method for controlling the startup thereof, and a recording medium storing a program for executing the method according to an embodiment of the present disclosure, since no additional converter is required, losses due to the addition of a converter can be avoided. For example, the cost of manufacturing a startup control system can be reduced, the process of manufacturing a startup control system can be simplified, and its volume can be reduced. In addition, since the control process is simplified, the overall efficiency of the startup control system can be improved, and its packaging can be improved.

[0149] However, the effects that can be achieved by the present disclosure are not limited to the above effects. A person skilled in the art will more clearly understand other effects not mentioned herein from the above description.

[0150] The various embodiments described above may be combined with each other without departing from the scope of the present disclosure unless they are incompatible with each other.

[0151] In addition, for any element or process that is not described in detail in any of the various embodiments, unless otherwise specified, reference can be made to the description of the element or process having the same reference numeral in another embodiment.

[0152] Although the present disclosure has been specifically shown and described with reference to several embodiments of the present disclosure, these embodiments are provided for illustrative purposes only. The described embodiments do not limit the present disclosure. It should be clear to those of ordinary skill in the art that different changes can be made in form and detail without departing from the essential features of the embodiments set forth herein. For example, the corresponding configurations set forth in the embodiments can be modified and applied. In addition, the differences in these modifications and applications should be interpreted as falling within the scope of the present disclosure as defined by the appended claims.

Claims

1. A fuel cell vehicle, comprising: Battery; A battery stack, comprising a plurality of unit cells stacked on top of each other; a boost converter configured to boost and output a target voltage received from the battery stack in response to a switching signal; a switching unit configured to switch in response to a control signal to connect the output side of the boost converter to the battery; as well as controller, the controller being configured to generating the control signal when starting the fuel cell vehicle is requested, and In response to a difference between a first voltage output from the battery stack and a second voltage of the battery, a switching frequency of the switching signal is changed.

2. The fuel cell vehicle according to claim 1, further comprising: A load is configured to be connected to the output side of the boost converter through a switching operation of the switching unit.

3. The fuel cell vehicle according to claim 2, further comprising: A peripheral auxiliary device is configured to be connected to the output side of the boost converter through a switching operation of the switching unit.

4. The fuel cell vehicle according to claim 1, wherein: The controller is configured to: When the sum of the first voltage and the minimum duty cycle voltage is equal to or greater than the second voltage, reducing the switching frequency; and The switching frequency is reduced until a sum of a minimum duty cycle voltage corresponding to the reduced switching frequency and the first voltage becomes smaller than the second voltage.

5. The fuel cell vehicle according to claim 4, wherein: The controller is configured to restore the reduced switching frequency when a sum of a minimum duty ratio voltage corresponding to the switching frequency before reduction and the first voltage becomes smaller than the second voltage.

6. The fuel cell vehicle according to claim 4, wherein: The minimum duty cycle voltage is calculated according to the following formula: , in, VDMIN represents the minimum duty cycle voltage, VIMAX represents the maximum value of the first voltage, and DMIN represents the minimum duty cycle.

7. The fuel cell vehicle according to claim 5, wherein: The minimum duty cycle voltage is calculated according to the following formula: , in, VDMIN represents the minimum duty cycle voltage, VIMAX represents the maximum value of the first voltage, and DMIN represents the minimum duty cycle.

8. The fuel cell vehicle according to claim 6, wherein: The minimum duty cycle is calculated according to the following formula: , in, T represents the minimum delay time of the boost converter, and F represents the switching frequency.

9. The fuel cell vehicle according to claim 8, wherein: The controller is configured to generate the switching signal in a pulse width modulation manner.

10. The fuel cell vehicle according to claim 9, wherein: The boost converter comprises: a first capacitor connected between a first output terminal on the positive side of the battery stack and a second output terminal on the negative side of the battery stack; an inductor including one end connected to the first output terminal; a diode including an anode connected to the other end of the inductor; a second capacitor disposed between a cathode of the diode and the second output terminal; and A semiconductor switch is configured to switch in response to the switching signal and is connected between the anode of the diode and the second output terminal.

11. The fuel cell vehicle according to claim 10, wherein: T corresponds to the switch-on time of the semiconductor switch.

12. A method for controlling the start-up of a fuel cell vehicle, the fuel cell vehicle comprising: A battery; a battery stack comprising a plurality of unit cells stacked on top of each other; and a boost converter configured to boost and output a target voltage received from the battery stack in response to a switching signal, the method comprising: When it is required to start the fuel cell vehicle, connecting the output side of the boost converter to the battery; operating the boost converter to receive the target voltage from the battery stack; and In response to a difference between a first voltage output from the battery stack and a second voltage of the battery, a switching frequency of the switching signal is adjusted.

13. The method according to claim 12, wherein: Adjusting the switching frequency includes: when a sum of the first voltage and a minimum duty cycle voltage is equal to or greater than the second voltage, reducing the switching frequency until the sum becomes less than the second voltage.

14. The method according to claim 13, further comprising: receiving the target voltage by the boost converter when a sum of a minimum duty cycle voltage corresponding to a reduced switching frequency and the first voltage becomes smaller than the second voltage; When a sum of a minimum duty cycle voltage corresponding to the switching frequency before reduction and the first voltage becomes smaller than the second voltage, restoring the reduced switching frequency; and The target voltage is received from the battery stack through the boost converter.

15. A computer-readable recording medium storing a program for executing a method of controlling the start-up of a fuel cell vehicle, the fuel cell vehicle comprising: Battery; a battery stack comprising a plurality of unit batteries stacked one on top of the other; and a boost converter configured to boost and output a target voltage received from the battery stack in response to a switching signal, wherein the recording medium stores a program that, when executed by one or more processors, causes the one or more processors to implement: a function of connecting the output side of the boost converter to the battery when a start of the fuel cell vehicle is requested; a function of operating the boost converter to receive the target voltage from the battery stack; as well as A function of adjusting a switching frequency of the switching signal according to a difference between a first voltage output from the battery stack and a second voltage of the battery.

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