KR102497029B1 - Control method for fuel cell - Google Patents

Abstract

A fuel cell control method according to the present invention is a control method of a fuel cell forming a stack by connecting a plurality of sub-stacks in series, in a first mode in which a motor is driven only with power generated in one of the plurality of sub-stacks. and a setting step of configuring a vehicle driving mode including a second mode in which motors are driven with power generated from a plurality of serially connected substacks, a preparation step of calculating an output value of the driving motor according to the torque and RPM required for the vehicle, The voltage and current in the first mode and the voltage and current in the second mode to achieve the output value calculated in the preparation step are calculated, and the fuel efficiency in the first mode and the second mode is calculated based on the calculated voltage and current. It includes a processing step of predicting each and a decision step of selecting one of the first mode and the second mode using the information acquired in the processing step.

Description

Fuel cell control method {CONTROL METHOD FOR FUEL CELL}

The present invention relates to a fuel cell control method, and more particularly, to a fuel cell control method in which a stack is configured by connecting a plurality of sub-stack modules in series.

In general, a fuel cell is formed by connecting a plurality of cells in series to form one fuel cell stack. By forming the cells in multiple layers in this way, high voltage and current can be obtained.

However, when a plurality of cells are continuously stacked one-dimensionally, since the shape of the fuel cell stack becomes wide and low in the shape of a plate, it is difficult to effectively dispose the fuel cell stack in a narrow space.

Therefore, a method of increasing space utilization is used by preparing a plurality of sub-stack modules in which a plurality of cells are connected in series and connecting them in series through a bus bar to configure one fuel cell stack.

On the other hand, fuel cells for automobiles can typically produce a high output of 100 kW, but as the voltage of electricity generated from the fuel cell increases, switching loss and conduction (conduction) loss increase, resulting in lower fuel cell efficiency.

Therefore, there is a demand for a new fuel cell control method capable of solving the above problems.

The matters described as the background art above are only for improving understanding of the background of the present invention, and should not be taken as an admission that they correspond to prior art already known to those skilled in the art.

KR 10-2010-0047058 A (2010.05.07)

The present invention has been made to solve these problems, and an object of the present invention is to provide a fuel cell control method capable of minimizing loss and achieving high fuel efficiency.

In order to achieve the above object, a fuel cell control method according to an embodiment of the present invention is a control method of a fuel cell forming a stack by connecting a plurality of substacks in series, and a fuel cell control method occurs in one substack among a plurality of substacks. A setting step of configuring a vehicle driving mode including a first mode in which the motor is driven only with the electric power that is connected in series and a second mode in which the motor is driven with the electric power generated from a plurality of serially connected substacks, and a preparation step in which the output value of the driving motor is calculated. , A processing step of predicting the fuel efficiency of the first mode and the second mode for the output value of the driving motor calculated in the preparation step, and selecting one of the first mode and the second mode using the information obtained in the processing step. It includes a decision-making step.

In the preparation step, the output value of the driving motor may be calculated according to the torque and RPM required for the vehicle.

The processing step calculates the voltage and current in the first mode and the voltage and current in the second mode to achieve the output value calculated in the preparation step, and calculates the voltage and current in the first mode and the second mode based on the calculated voltage and current. The fuel efficiency of each of the two modes can be predicted.

In the determining step, a mode with high fuel efficiency predicted in the processing step may be selected from among the first mode and the second mode.

The setting step configures a vehicle driving mode by further including a third mode in which a battery is charged using power generated from a plurality of substacks and a motor is driven by simultaneously discharging the battery, and the determining step comprises: Any one of the first mode, the second mode, and the third mode may be selected using the information obtained in the processing step.

The processing step includes a first determination step of determining whether the calculated voltage of the first mode and the voltage of the second mode are equal to or less than a preset upper limit value, and the determining step comprises: voltage of the first mode in the first determination step. and a first selection step of selecting a mode with high fuel efficiency predicted in the processing step from among the first mode and the second mode when the voltages of the second mode are all equal to or less than the upper limit value.

In the processing step, when the voltage of the first mode or the voltage of the second mode exceeds the upper limit value in the first determination step, the second mode of determining whether both the voltage of the first mode and the voltage of the second mode exceed the upper limit value Further comprising a determination process, wherein the determination step is, when any one of the voltage of the first mode or the voltage of the second mode in the second determination process is equal to or less than the upper limit value, the voltage of the first mode and the second mode is equal to or less than the upper limit value. It may include a second selection process for selecting.

The determining step may include a third selection process of selecting a third mode when both the voltage of the first mode and the voltage of the second mode in the second determination process exceed an upper limit value.

After the first mode is selected in the determining step, a charging determination process of determining whether the charge amount of the battery is less than a preset reference value, and if the charge amount of the battery is less than the reference value in the charge determination process, the battery is used by using a sub-stack not used for driving the motor. A charging process of charging may be further included.

The plurality of substacks may be composed of two.

According to the fuel cell control method according to the present invention, the following effects are obtained.

First, fuel efficiency can be improved by increasing the efficiency of the fuel cell system.

Second, by reducing the operating voltage of the fuel cell, it is possible to reduce various losses and improve durability of the fuel cell stack.

Third, it is possible to reduce the accumulation of water in the separator by avoiding the low-current operating condition.

Fourth, by using the non-driven sub-stack as a generator to charge the battery, it is easy to manage the charge amount of the battery.

1 is a flowchart according to a first embodiment of the present invention.
2 is a flowchart according to a second embodiment of the present invention.

The terminology used herein is intended only to refer to specific embodiments and is not intended to limit the present invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. As used herein, the meaning of "comprising" specifies specific characteristics, regions, integers, steps, operations, elements, and/or components, and other specific characteristics, regions, integers, steps, operations, elements, elements, and/or groups. does not exclude the presence or addition of

Although not defined differently, all terms including technical terms and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Terms defined in commonly used dictionaries are additionally interpreted as having meanings consistent with related technical literature and currently disclosed content, and are not interpreted in ideal or very formal meanings unless defined.

Hereinafter, a fuel cell control method according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a flowchart of a first embodiment of the present invention.

As shown in FIG. 1, the first embodiment of the present invention largely includes a setting step (S100), a preparation step (S200), a processing step (S300), and a decision step (S400).

The setting step (S100) includes a first mode in which one of a plurality of serially connected substacks is selected and only the corresponding substack is directly connected to a motor, and a second mode in which all of the plurality of serially connected substacks are directly connected to a motor. This is a step of configuring a vehicle driving mode to be performed.

A plurality of substacks can be connected in series through a kind of switch. In the first mode, a single substack with relatively low voltage and high current is used by disconnecting the serial connection between the plurality of substacks and connecting only one substack to a motor. In the second mode, a plurality of sub-stacks are connected in series and connected to a motor to use a plurality of sub-stacks with relatively high voltage and low current. In subsequent steps, one of these sub-stacks is selected. .

The preparation step (S200) is a step of calculating the output value of the drive motor according to the torque and RPM required for the vehicle. More specifically, the required torque and RPM are determined according to the current speed and acceleration demand of the vehicle, and based on this, a target output value supplied to the motor is calculated.

In the processing step (S300), the voltage and current of the first mode and the voltage and current of the second mode are calculated respectively according to the target output value calculated in the preparation step (S200), and each mode is separately calculated according to the calculated voltage and current. This is the step of predicting fuel economy.

When the voltage and current values of the first mode and the second mode are calculated in the processing step (S300), if the target output value calculated in the preparation step (S200) is constant, a constant output value is obtained by controlling the voltage and current in an inverse proportion to each other. can That is, the first mode using a single sub-stack requires a relatively high amount of current to reach the target output value because the output voltage is small, and the second mode using a plurality of sub-stacks connected in series has a relatively high amount of current compared to the single sub-stack. Since the output voltage is high, a relatively small amount of current is required to reach the target output value.

As the voltage of electricity generated from the fuel cell increases and the current decreases, switching loss and conduction (conductive) loss increase, and the efficiency of the driving system, MCU, air compressor, and DC-DC converter decreases. In addition, if the current is kept low, the flow rate of gas supplied to the fuel cell may decrease, causing a problem in that water inside the separator is not easily discharged. This causes the efficiency of the fuel cell to decrease. On the other hand, as the voltage of the fuel cell decreases and the current increases, the power generation efficiency of the fuel cell stack decreases.

Considering these factors, the fuel efficiency of each mode can be predicted through the voltage and current in the first mode and the voltage and current in the second mode.

The determining step (S400) is a step of selecting one of the first mode and the second mode using the information obtained in the processing step (S300). There may be several standards for this, but the simplest and most effective standard is to use a mode that exhibits high fuel efficiency among the first mode and the second mode.

That is, the first mode is used if the fuel efficiency of the first mode using a single sub-stack is relatively high, and the second mode is used if the fuel efficiency of the second mode using a plurality of sub-stacks connected in series is relatively high.

In general, a first mode using a single sub-stack may exhibit high efficiency in a low power range, and a second mode using a plurality of serially connected sub-stacks may exhibit high efficiency in a medium to high power range.

Meanwhile, FIG. 2 shows a flow chart of a second embodiment according to the present invention.

As shown in FIG. 2, the second embodiment according to the present invention, similar to the first embodiment, includes a setting step (S100), a preparation step (S200), a processing step (S300) and a decision step (S400). It consists of

However, the second embodiment according to the present invention has a difference in that the setting step (S100), the processing step (S300), and the determining step (S400) are more subdivided than the first embodiment. Hereinafter, each step of the second embodiment according to the present invention will be described in detail.

First, since the preparation step (S200) is performed in the same manner as in the first embodiment according to the present invention, duplicate descriptions will be omitted.

The setting step (S100), in addition to setting the first mode and the second mode as in the setting step (S100) of the first embodiment of the present invention described above, uses power generated from a plurality of serially connected substacks to charge the battery. A vehicle driving mode is set by further including a third mode in which the motor is driven by discharging the battery while charging. Unlike the first mode and the second mode, the third mode is a driving mode in which the motor is driven by discharging the battery while charging the battery through the sub-stack, instead of directly driving the motor with the power generated in the sub-stack.

In the processing step (S300), after calculating or predicting the voltage, current, and fuel efficiency of the first mode and the second mode, respectively, as in the processing step (S300) of the first embodiment of the present invention described above, the first judgment process ( S310) and a second judgment process (S320) are additionally included.

The first judgment process (S310) is a process of determining whether the first mode voltage and the second mode voltage calculated in the processing step (S300) are equal to or less than a preset upper limit value, and the second judgment process (S320) is a first judgment process. In step S310, when at least one of the first mode voltage and the second mode voltage exceeds the upper limit value, it is a process of determining whether both the first mode voltage and the second mode voltage exceed the upper limit value.

When the voltage of the power generated in the fuel cell stack is too high, the loss due to heat generation increases due to the increase in switching loss and conduction loss, and the flowability of the fuel cell is lowered due to the relatively reduced current amount. There may be problems with water accumulation.

Therefore, in the first judgment process (S310) and the second judgment process (S320), it is determined whether the voltages of the first mode and the second mode are less than or greater than the upper limit value, which is a preset safety range, and will be described later through the determination result. In the decision step (S400), a driving mode is selected.

In the determination step (S400), the first selection process (S410) performed when both the voltages of the first mode and the second mode are less than the upper limit value during the first decision process (S310), and the first selection process (S410) during the second decision process (S320). During the second selection process (S420), which is performed when the voltage of any one of the mode and the second mode exceeds the upper limit value, and the second decision process (S320), the voltage of both the first mode and the second mode exceeds the upper limit value. It is configured to include a third selection process (S430) performed when

In the first selection process (S410), since the voltages of the first mode and the second mode are both below the upper limit of the safe range, it is basically okay to use either of the first mode and the second mode. However, it would be more preferable to compare the fuel efficiency of the first mode with that of the second mode and select a mode exhibiting high fuel efficiency among them.

In the second selection process (S420), a mode having a voltage equal to or less than the upper limit value is selected from among the first mode and the second mode. In this case, the process of comparing fuel efficiency between the first mode and the second mode is omitted.

The third selection process (S430) is a process of selecting the third mode when both the voltages of the first mode and the second mode exceed the upper limit. That is, in all conditions in which one sub-stack is used alone or multiple sub-stacks connected in series to achieve the output required for the vehicle, when the voltage exceeds the upper limit and reaches the dangerous range, the sub-stack occurs. Instead of directly using the power to drive the motor, the battery is charged using the power generated in the sub-stack and then the battery is discharged to drive the motor.

Through this process, it is possible to prevent the voltage of the power generated in the sub-stack from exceeding the upper limit value and reaching a dangerous range when driving the motor, and problems such as increased loss due to overvoltage.

In addition to this, the second embodiment according to the present invention may further include a charging determination process (S510) and a charging process (S520).

The charging determination process (S510) is a process of determining whether the charge amount of the battery is equal to or less than a predetermined reference value after the first mode is selected in the determination step (S400).

More specifically, the fuel efficiency of the first mode is predicted to be higher in the first selection process (S410) and the first mode is selected, or the voltage of the first mode is calculated to be less than the upper limit in the second selection process (S420). When the first mode is selected, it is determined whether the charge amount of the battery installed in the vehicle is equal to or less than a predetermined reference value.

In the charging process (S520), when the charge amount of the battery is less than the reference value in the charging determination process (S510), the battery is charged with power generated in the remaining sub-stacks that are not directly connected to the motor, that is, non-driving stacks.

Through this, when a motor is driven using only one sub-stack, idle energy can be effectively utilized by charging the battery with the remaining sub-stack, the charge amount of the battery can be easily managed, and charging/discharging efficiency can be improved. .

Although the number of substacks is not particularly limited in the first and second embodiments according to the present invention described above, the first mode uses one substack and the second mode uses two substacks. You will be able to drive motors using substacks.

Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art can realize that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. you will be able to understand

Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting. The scope of the present invention is indicated by the claims to be described later rather than the detailed description above, and all changes or modified forms derived from the meaning and scope of the claims and equivalent concepts thereof should be construed as being included in the scope of the present invention. .

S100: Setting step
S200: preparation step
S300: processing step
S400: decision step

Claims (10)

A control method of a fuel cell capable of disconnecting a serial connection between substacks by connecting a plurality of substacks in series through a switch, the method comprising:
A first mode in which a motor is driven only with power generated in one of a plurality of substacks through release of a switch, and a second mode in which a motor is driven with power generated in a plurality of serially connected substacks by connecting a switch, and a setting step of configuring a vehicle driving mode including a third mode in which a battery is charged using power generated from a plurality of substacks by connecting a switch and a motor is driven by simultaneously discharging the battery;
A preparation step of calculating an output value of a driving motor;
The voltage and current in the first mode and the voltage and current in the second mode are calculated to achieve the output value of the driving motor calculated in the preparation step, and the calculated voltage and current in the first mode and the voltage in the second mode are set in advance. a processing step of determining whether the upper limit value is exceeded; and
and a determination step of selecting a third mode when both the voltage of the first mode and the voltage of the second mode in the processing step exceed an upper limit value.
The method of claim 1,
In the preparation step, the fuel cell control method is characterized in that the output value of the driving motor is calculated according to the torque and RPM required for the vehicle.
The method of claim 1,
The fuel cell control method, characterized in that the processing step predicts fuel efficiency in the first mode and the second mode, respectively, based on the calculated voltage and current.
The method of claim 3,
The fuel cell control method, characterized in that the determining step selects a mode with high fuel efficiency predicted in the processing step from among the first mode and the second mode.
delete The method of claim 4,
In the determining step, when both the voltage of the first mode and the voltage of the second mode are equal to or less than the upper limit value in the processing step, a first selection is performed to select a mode with high fuel efficiency predicted in the processing step from among the first mode and the second mode. A method for controlling a fuel cell, characterized in that it comprises a process.
The method of claim 1,
The determining step includes a second selection process of selecting a mode in which the voltage is less than or equal to the upper limit value among the first mode and the second mode when either the voltage of the first mode or the voltage of the second mode is less than or equal to the upper limit value in the processing step. Characterized in that, a fuel cell control method.
delete According to claim 4 or 7,
After the first mode is selected in the determining step, a charging determination process of determining whether the charge amount of the battery is less than a preset reference value, and if the charge amount of the battery is less than the reference value in the charge determination process, the battery is used by using a sub-stack not used for driving the motor. Characterized in that it further comprises a charging process of charging the fuel cell control method.
The method of claim 1,
The fuel cell control method, characterized in that the plurality of sub-stacks are composed of two.

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