KR102496258B1 - Control method for driving motor of fuel cell vehicle - Google Patents

Abstract

recognizing whether the fuel cell is in a stop mode; determining whether wheel slip of the vehicle occurs when the fuel cell stop mode is recognized; and limiting the torque command of the drive motor when it is determined that wheel slip has occurred.

Description

Driving motor control method of fuel cell vehicle {CONTROL METHOD FOR DRIVING MOTOR OF FUEL CELL VEHICLE}

The present invention relates to a method for controlling a driving motor of a fuel cell vehicle, and more particularly, to a technique for limiting torque of a driving motor when wheel slip occurs.

A fuel cell, which has recently been in the limelight as an eco-friendly energy source, is a power generation device that converts the chemical energy of fuel into electrical energy by electrochemically reacting it in a fuel cell stack without converting it into heat through combustion. It can also be applied to the power supply of small electrical and electronic products.

In particular, as a power supply source for vehicle driving, a technology for generating electric energy through a chemical reaction with oxygen in the air using hydrogen as fuel has been developed. A fuel cell vehicle generally uses a hybrid power distribution method in which a fuel cell is used as a main power supply source and a high voltage battery is used as an auxiliary power source or a power storage device, and a method of driving using an electric motor is used.

A fuel cell vehicle is equipped with an idle stop operation function that runs in a fuel cell STOP mode that cuts off power generation of a fuel cell even while driving when a low-load or high-voltage battery has sufficient charge (SOC).

On the other hand, vehicles driven by electric motors have characteristics that can generate full torque when starting from a stop state, so wheel slip occurs excessively when rapidly accelerating on a road surface with low friction. In particular, in the case of a fuel cell vehicle, it takes response time until power generation starts from the fuel cell in the fuel cell STOP mode, and if wheel slip occurs during that time, the power consumption and RPM of the motor increase rapidly, enabling output of a high-voltage battery. power (approximately 40 kW).

As a result, the current of the high voltage battery increases rapidly and the voltage of the main bus terminal decreases. If the current of the high-voltage battery surges, overcurrent flows in the converter (BHDC: Bidirectional High-voltage DC/DC Converter) provided between the high-voltage battery and the main bus, or if the voltage of the main bus drops, the accessories connected to the main bus There was a problem that a low voltage was applied to the back, which could cause failure of the system device.

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 10-0867823 B KR 10-2009-0055053 A

The present invention has been proposed to solve this problem, and is intended to provide a technology for limiting the driving torque of a motor when wheel slip occurs in a fuel cell stop mode in a fuel cell vehicle.

According to the present invention for achieving the above object

According to the method for controlling a drive motor of a fuel cell vehicle of the present invention, when driving on a low-friction road surface in a fuel cell stop state, it has an effect of preventing a phenomenon in which power is excessively supplied from a battery until the power of the fuel cell is available. .

In addition, this has an effect of preventing an overcurrent from flowing through components such as a battery or a converter.

In addition, it has an effect of preventing a problem in which the voltage of the main bus terminal decreases and low voltage is applied to electric components connected to the main bus terminal.

1 shows a configuration diagram of a fuel cell system according to the prior art.
2 is a flowchart of a method for controlling a driving motor of a fuel cell vehicle according to an embodiment of the present invention.
3 illustrates a pre-stored map limiting a torque command of a driving motor according to an embodiment of the present invention.
4 illustrates a torque command limit state of a drive motor according to an embodiment of the present invention.

Specific structural or functional descriptions of the embodiments of the present invention disclosed in this specification or application are merely exemplified for the purpose of explaining the embodiments according to the present invention, and the embodiments according to the present invention may be implemented in various forms. and should not be construed as being limited to the embodiments described in this specification or application.

Embodiments according to the present invention can apply various changes and can have various forms, so specific embodiments are illustrated in the drawings and described in detail in this specification or application. However, this is not intended to limit the embodiments according to the concept of the present invention to a specific disclosed form, and should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

Terms such as first and/or second may be used to describe various components, but the components should not be limited by the terms. The above terms are only for the purpose of distinguishing one component from another component, e.g., without departing from the scope of rights according to the concept of the present invention, a first component may be termed a second component, and similarly The second component may also be referred to as the first component.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle. Other expressions describing the relationship between elements, such as "between" and "directly between" or "adjacent to" and "directly adjacent to", etc., should be interpreted similarly.

Terms used in this specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "comprise" or "having" are intended to designate that the described feature, number, step, operation, component, part, or combination thereof exists, but one or more other features or numbers However, it should be understood that it does not preclude the presence or addition of steps, operations, components, parts, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined herein, they are not interpreted in an ideal or excessively formal meaning. .

Hereinafter, the present invention will be described in detail by describing preferred embodiments of the present invention with reference to the accompanying drawings. Like reference numerals in each figure indicate like elements.

1 shows a configuration diagram of a fuel cell system according to the prior art.

The fuel cell stack 10 is connected to the inverter 30 that supplies power to the driving motor 40 through the main bus terminal 20 . The battery 60 is connected to the main bus stage 20 through a converter 50. The battery 60 may receive power from the main bus terminal 20 or supply power to the main bus terminal 20 as the high voltage battery 60 is charged or discharged. The converter 50 may be a high voltage DC/DC converter (HDC) or a bidirectional high voltage DC/DC converter (BHDC) capable of supplying power in both directions.

In addition, accessories 70 (BOP) may be connected to the main bus stage 20. The accessories 70 may include devices such as a pump and an air blower for driving the fuel cell stack 10 . Power supplied from the fuel cell stack 10 or the battery 60 may be supplied to the main bus terminal 20 to drive the driving motor 40 or to accessories 70 through the inverter 30 .

The MCU (90, Motor Control Unit, motor controller) may be a controller that controls the RPM or torque of the driving motor 40 by controlling the inverter 30 that supplies power to the driving motor 40 . In addition, the FCU (80, fuel cell control unit, fuel cell controller) may be an upper controller that controls the MCU 90 and controls the fuel cell stack 10, accessories 70, converter 50, and the like. Hereinafter, the control method of the present invention may be a control method performed by the FCU.

2 is a flowchart of a method for controlling a driving motor of a fuel cell vehicle according to an embodiment of the present invention.

Referring further to FIG. 2 , a method for controlling a driving motor of a fuel cell vehicle according to an embodiment of the present invention includes the step of recognizing whether or not a fuel cell stop mode is present (S20); If it is recognized as a fuel cell stop mode, determining whether wheel slip of the vehicle has occurred (S30); and limiting the torque command of the driving motor 40 when it is determined that wheel slip has occurred (S50, S70).

First, vehicle information may be collected to check the current state of the fuel cell vehicle (S10). Information on the fuel cell, battery 60, etc. may be collected by receiving sensing values from a sensor or the like in the FCU 80.

In the step of recognizing whether the fuel cell is in the stop mode (S20), whether the fuel cell is in the stop mode can be recognized according to the collected information. In the fuel cell stop mode, power generation of the fuel cell may be stopped when the ignition of the fuel cell vehicle is off or when the vehicle is running at a low load with sufficient charge (SOC) of the battery 60 even when the ignition is on.

Here, the fuel cell stop mode includes not only a state in which power generation in the fuel cell stack 10 is stopped, but also a state in which power is not supplied to the main bus stage 20 even though some power generation is performed. That is, the fuel cell stop mode means a state in which the driving motor 40 or the accessories 70 are driven using only the power of the battery 60, not the power generated by the fuel cell.

Recognizing whether the fuel cell is in the stop mode ( S20 ) may be based on the current of the fuel cell stack 10 or the voltage of the fuel cell stack 10 . In general, in the fuel cell stop mode, the voltage of the fuel cell stack 10 is controlled to maintain a low state due to problems such as durability, and thus current is not supplied to the main bus stage 20. This is because the voltage of the fuel cell stack 10 must be higher than the voltage of the main bus terminal 20 in order for the power generated by the fuel cell stack 10 to be supplied to the main bus terminal 20 .

Therefore, when the amount of current flowing from the fuel cell stack 10 to the main bus stage 20 is sensed and is less than a predetermined current value, the fuel cell stop mode can be recognized, and the voltage of the fuel cell stack 10 When the sensing voltage is lower than a predetermined voltage value, it may be recognized as whether the fuel cell is in the stop mode.

In another embodiment, the step of recognizing whether the fuel cell is in the stop mode ( S20 ) may recognize whether or not air is supplied to the fuel cell stack 10 or based on time from when air supply is resumed.

In general, in the fuel cell stop mode, the supply of air to the fuel cell stack 10 is cut off, and power generation in the fuel cell stack 10 is cut off. Therefore, the fuel cell stop mode can be recognized through whether or not air is supplied to the fuel cell stack 10 . When air supply to the fuel cell stack 10 is cut off, it can be recognized as a fuel cell stop mode.

In addition, even if air is being supplied to the fuel cell stack 10, immediately after the air supply is resumed, it is still in the fuel cell stop mode in which power cannot be supplied from the fuel cell stack 10 to the main bus stage 20. . Therefore, even if air is being supplied to the fuel cell stack 10, if the time from when the air supply is resumed is equal to or shorter than the preset time, the fuel cell stop mode may be recognized.

Determining whether wheel slip of the vehicle has occurred ( S30 ) may be determined based on a difference value of individual wheel speeds of the vehicle. In particular, in the step of determining whether wheel slip of the vehicle has occurred, it may be determined that wheel slip of the vehicle has occurred if the maximum value among the difference values of individual wheel speeds of the vehicle is equal to or greater than a predetermined speed value.

When wheel slip of the vehicle occurs, some wheels may rotate at a higher speed than the other wheels. Accordingly, a difference value between individual wheel speeds may be calculated by sensing or calculating the rotation speed of each wheel.

For example, the wheel rotational speed difference between the left front wheel and the left rear wheel and the wheel rotational speed difference between the right front wheel and the right rear wheel are calculated, respectively, and the larger value is the preset speed value (eg 5 [kph]) If it is abnormal, it can be determined that wheel slip has occurred.

In addition, all speed differences between individual wheels may be calculated, or the maximum value may be used by calculating the speed difference between the wheel speed calculated based on the rotational speed of the motor and the speed difference between individual wheels.

When the fuel cell is not in a stopped state or wheel slip does not occur, the driving torque may be controlled by a general driving torque command (S80).

3 illustrates a pre-stored map limiting a torque command of a driving motor according to an embodiment of the present invention.

Among them, FIG. 3A shows an increase rate map of the torque command of the drive motor 40 according to the ratio of motor consumption power among motor available power. Referring further to FIG. 3A , the step of limiting the torque command of the drive motor 40 (S50, S70) may limit the rate of increase of the torque command of the drive motor 40 as the power consumed by the motor increases ( S50).

Specifically, the rate of increase of the torque command of the drive motor 40 may be limited by a map of the rate of increase of the torque command of the drive motor 40 according to the ratio of motor consumption power among previously stored motor available power. That is, as the ratio of the motor consumption power to the motor available power increases, the rate of increase of the torque command of the driving motor 40 may be limited to decrease.

Before limiting the rate of increase of the torque command of the drive motor 40, the motor available power and motor consumption power may be calculated (S40). The available power of the motor can be calculated by multiplying the available power of the battery 60 by the efficiency and subtracting the consumed power of the accessories 70 . The available power of the battery 60 is a value that can be calculated in real time by the battery 60 or the converter 50, and the efficiency is variable by temperature, voltage, current, or SOC in consideration of the conversion efficiency of the converter 50. value that can be The power consumption of the accessories 70 can be calculated by summing the power consumed by the accessories 70 such as a pump, a radiator fan, a heater (PTC), and an air conditioner.

Motor consumption power can be calculated by multiplying the torque of the driving motor 40 and the rotational speed of the driving motor 40 . In addition, more precisely, motor consumption power can be calculated by dividing the efficiency of the drive motor 40 by the product of the torque of the drive motor 40 and the rotational speed of the drive motor 40 in consideration of the efficiency of the drive motor 40 . can The torque of the driving motor 40 and the rotational speed of the driving motor 40 may receive information from the MCU 90 . The efficiency of the drive motor 40 may be calculated by considering both electrical losses of the inverter 30 and the like or physical frictional losses between parts.

That is, since the available power of the motor is maintained almost constant, the power consumed by the motor rapidly changes according to the driving state, it is possible to limit the rate of increase of the torque command of the driving motor 40 using only the consumed power of the motor, More precisely, the rate of increase of the torque command of the driving motor 40 may be limited by calculating the ratio of motor consumption power to available motor power.

FIG. 3B shows a map of the torque limit value TLv according to the converter 50 voltage. 3B, the step of limiting the torque command of the drive motor 40 (S50, S70) is the input or output voltage of the converter 50 connecting the high voltage battery 60 and the main bus terminal 20. Based on the size, the torque command of the driving motor 40 may be limited (S70).

Specifically, the step of limiting the torque command of the drive motor 40 (S50, S70) is the smaller of the torque limit value according to the magnitude of the voltage input or output to the converter 50 and the torque value required by the drive motor 40. Depending on the value, the torque command of the drive motor 40 may be set.

Since the battery 60 is discharging in the fuel cell stop mode, the torque limit value depends on the voltage input from the battery 60 to the converter 50 or the voltage output from the converter 50 to the main bus terminal 20. can be set.

As shown in FIG. 3B , the torque limit value may be maintained constant in a high voltage state, but rapidly decrease when the voltage drops below a certain level. This is because when the voltage of the converter 50 decreases, the voltage of the main bus terminal 20 drops and damage may occur due to low voltage being applied to devices such as accessories 70 connected to the main bus terminal 20. because to prevent this.

3C shows a map of the torque limit value TLi according to the converter 50 current. Referring further to FIG. 3C, the steps of limiting the torque command of the drive motor 40 (S50, S70) are input or output to the converter 50 disposed between the high voltage battery 60 and the main bus terminal 20. Based on the size of the current, the torque command of the drive motor 40 may be limited (S70).

More specifically, the step of limiting the torque command of the drive motor 40 is driven according to the smaller value of the torque limit value according to the magnitude of the current input or output to the converter 50 and the torque value required by the drive motor 40. A torque command for the motor 40 can be set.

Since the battery 60 will be discharging in the fuel cell stop mode, the driving motor ( 40) torque command can be limited.

As shown in FIG. 3C , the torque limit value may be maintained constant when the current is small, but may rapidly decrease when the current exceeds a certain level. This is to prevent a situation in which, as a high current flows through the converter 50, an allowable current of the battery 60 or the converter 50 may exceed the allowable current, causing damage to components.

In FIG. 3A, the driving torque command limiting the torque command increase rate, in FIG. 3B, the torque command according to the torque limit value according to the converter 50 voltage size, and in FIG. 3C, the torque command according to the torque limit value based on the converter 50 current size. It is possible to limit the driving torque of the driving motor 40 by calculating all of them and setting the driving torque command to the minimum value among them (S70).

4 shows a torque command limit state of the driving motor 40 according to an embodiment of the present invention.

Referring to FIG. 4 , when the accelerator is stepped on for full acceleration (WOT: Wide Open Throttle), conventionally, the drive torque command of the drive motor 40 rapidly increases (solid line). However, as the ratio of motor consumption power among motor available power increases, the driving torque command increase rate of the drive motor 40 is limited, and thus the slope of the drive torque command decreases and increases (dotted dashed line).

When the voltage of the converter 50 decreases below the preset voltage or when the current of the converter 50 increases above the preset current, the drive motor ( 40) is limited to a smaller driving torque command (dotted line).

Therefore, when wheel slip occurs in the fuel cell stop mode, the effect of limiting the driving torque command of the driving motor 40 can be confirmed. In addition, according to this, it can be confirmed that the voltage of the converter 50 immediately rises again, and the current of the converter 50 also immediately drops and returns to an appropriate level.

Although shown and described in relation to specific embodiments of the present invention, it is known in the art that the present invention can be variously improved and changed without departing from the technical spirit of the present invention provided by the claims below. It will be self-evident to those skilled in the art.

10: fuel cell stack 20: main bus stage
30: inverter 40: drive motor
50: converter 60: battery
70: Accessories 80: FCU
90: MCU

Claims (14)

recognizing whether the fuel cell is in a stop mode;
determining whether wheel slip of the vehicle occurs when the fuel cell stop mode is recognized; and
If it is determined that wheel slip has occurred, limiting the torque command of the drive motor; includes,
The step of limiting the torque command of the drive motor limits the torque command of the drive motor based on the size of the input or output voltage of the converter connecting the high-voltage battery and the main bus stage, and the step of limiting the torque command of the drive motor is the converter. A method for controlling a drive motor of a fuel cell vehicle, characterized in that a torque command of the drive motor is set according to a smaller value between a torque limit value according to the magnitude of voltage input or output to the drive motor and a torque value required by the drive motor. The method of claim 1,
A method for controlling a driving motor of a fuel cell vehicle, wherein the step of recognizing whether or not the fuel cell stop mode is in the fuel cell stack is based on a current of the fuel cell stack or a voltage of the fuel cell stack. The method of claim 1,
A method for controlling a driving motor of a fuel cell vehicle, wherein the step of recognizing whether or not the fuel cell is in the stop mode is based on whether or not air is supplied to the fuel cell stack or based on time from when air supply is resumed. The method of claim 1,
A method for controlling a drive motor of a fuel cell vehicle, wherein the step of determining whether wheel slip of the vehicle has occurred is determined based on a difference value of individual wheel speeds of the vehicle. The method of claim 4,
In the step of determining whether wheel slip of the vehicle has occurred, it is determined that wheel slip of the vehicle has occurred when the maximum value among the difference values of individual wheel speeds of the vehicle is equal to or greater than a preset speed value. . The method of claim 1,
A method for controlling a drive motor of a fuel cell vehicle, wherein the step of limiting the torque command of the drive motor limits an increasing rate of the torque command of the drive motor as power consumed by the motor increases. The method of claim 6,
A method for controlling a drive motor of a fuel cell vehicle, characterized in that an increase rate of the torque command of the drive motor is limited by an increase rate map of the torque command of the drive motor according to a ratio of motor consumption power among previously stored motor available power. recognizing whether the fuel cell is in a stop mode;
determining whether wheel slip of the vehicle occurs when the fuel cell stop mode is recognized; and
If it is determined that wheel slip has occurred, limiting the torque command of the drive motor; includes,
The step of limiting the torque command of the drive motor limits the torque command of the drive motor based on the amount of current input or output to the converter disposed between the high voltage battery and the main bus stage, and the step of limiting the torque command of the drive motor A method for controlling a drive motor of a fuel cell vehicle, characterized in that a torque command of a drive motor is set according to a smaller value between a torque limit value according to the magnitude of current input or output to a converter and a torque value required by the drive motor. The method of claim 8,
A method for controlling a driving motor of a fuel cell vehicle, wherein the step of recognizing whether or not the fuel cell stop mode is in the fuel cell stack is based on a current of the fuel cell stack or a voltage of the fuel cell stack. The method of claim 8,
A method for controlling a driving motor of a fuel cell vehicle, wherein the step of recognizing whether or not the fuel cell is in the stop mode is based on whether or not air is supplied to the fuel cell stack or based on time from when air supply is resumed. The method of claim 8,
A method for controlling a drive motor of a fuel cell vehicle, wherein the step of determining whether wheel slip of the vehicle has occurred is determined based on a difference value of individual wheel speeds of the vehicle. The method of claim 11,
In the step of determining whether wheel slip of the vehicle has occurred, it is determined that wheel slip of the vehicle has occurred when the maximum value among the difference values of individual wheel speeds of the vehicle is equal to or greater than a preset speed value. . The method of claim 8,
A method for controlling a drive motor of a fuel cell vehicle, wherein the step of limiting the torque command of the drive motor limits an increasing rate of the torque command of the drive motor as power consumed by the motor increases. The method of claim 13,
A method for controlling a drive motor of a fuel cell vehicle, characterized in that an increase rate of the torque command of the drive motor is limited by an increase rate map of the torque command of the drive motor according to a ratio of motor consumption power among previously stored motor available power.

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