MOTOR TORQUE CONTROL METHOD, APPARATUS, AND COMPUTER READABLE MEDIUM FOR AIR BLOWER

Abstract

A motor torque control method for an air blower may include: setting a phase current command value of a motor of the air blower based on a temperature of the motor, calculating a d-axis current command value other than zero in compliance with the set phase current command value, and outputting the calculated d-axis current command value.

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to and the benefit of Korean Patent Application Number 10-2014-0067873 filed on Jun. 3, 2014, the entire contents of which application are incorporated herein for all purposes by this reference.

BACKGROUND

1. Technical Field

The present disclosure relates, in general, to a motor torque control method for an air blower and, more particularly, to a motor torque control method for an air blower, which can rapidly raise the temperature of a fuel cell stack in a cold-start condition.

2. Description of the Related Art

As is understood in the art, a typical fuel cell vehicle includes a fuel cell stack in which a plurality of fuel cells used as a power source are stacked one on top of another, a fuel supply system for supplying a fuel (e.g., hydrogen or the like) to the fuel cell stack, an air supply system for supplying oxygen, which is an oxidant required for electrochemical reactions, a water/heat management system for controlling the temperature of the fuel cell stack, etc. The fuel supply system decompresses compressed hydrogen in a hydrogen tank and supplies decompressed hydrogen to the fuel electrode (anode) of the stack. The air supply system supplies external air, drawn in by operating an air blower, to the air electrode (cathode) of the stack.

When hydrogen is supplied to the anode of the stack and oxygen is supplied to the cathode, hydrogen ions are separated at the anode via a catalytic reaction. The separated hydrogen ions are transferred to an oxidation electrode, which is the cathode, through an electrolyte membrane. The hydrogen ions separated at the anode, electrons and oxygen together cause an electrochemical reaction at the oxidation electrode, and thus, electrical energy can be obtained through such a reaction. In detail, an electrochemical oxidation of hydrogen occurs at the anode, and an electrochemical reduction of oxygen occurs at the cathode. Due to the movement of electrons generated in this procedure, electricity and heat are generated, and vapor or water is generated due to a chemical action in which hydrogen and oxygen combine.

A discharge device is provided to discharge by-products such as vapor, water and heat, which are produced when generating the electrical energy of the fuel cell stack, the unreacted hydrogen, oxygen, etc. Gases such as vapor, hydrogen and oxygen are discharged to the atmosphere through a discharge path.

Components such as an air blower, a hydrogen recirculation blower, and a water pump for driving fuel cells, are connected to a main bus terminal to facilitate starting of the fuel cells. Various types of relays for facilitating power disconnection and connection, as well as a diode for preventing a reverse current from flowing into the fuel cell, may be connected to the main bus terminal.

Air supplied through the air blower is humidified by a humidifier, and is then supplied to the cathode (air electrode) of the fuel cell stack. An exhaust gas from the cathode is transferred to the humidifier with the exhaust gas humidified by internally generated water components, and may be used to humidify dry air to be supplied to the cathode through the air blower. Such an air blower may include a motor, a magnetic rotor for generating turning force (torque), a blade for drawing in air, and the like.

Meanwhile, the motor included in the air blower may be a permanent magnet synchronous motor. FIG. 1 is a graph showing a relationship between a q-axis current command i_q* and a d-axis current command i_d* in a permanent magnet synchronous motor control system. Typically, in compliance with a torque command from an upper-level controller or an external system, a current command generator (not shown) generates a q-axis current command (e.g., torque split current command) corresponding to the torque command, and generates a d-axis current command (e.g., magnetic flux split current command), wherein the d-axis current command is set to ‘0’ in order to operate the motor at maximum efficiency.

The current commands generated by the current command generator are output to a current controller (not shown), and the current controller generates d-axis and q-axis voltage commands. Thereafter, a 3-phase voltage command is generated, and the motor is controlled via a pulse width modulation (PWM) procedure and a 3-phase current control procedure.

Meanwhile, when the fuel cell vehicle stops, an amount of water generated during driving remains in the fuel cell stack. Further, when the external temperature of the vehicle is very low, such remaining water is condensed to cause a phase change to ice, and then a problem arises in that starting of the fuel cell vehicle is impossible. In order to secure cold-startability in such a cold-start environment, a method for rapidly defrosting a coolant using a heater and a method of installing a heater on an air supply system line and raising the temperature of air may be utilized.

However, a method of installing a heater on a suction line between the air blower and the humidifier during cold-starting, or a method of heating the fuel cell stack by circulating warm air discharged from the fuel cell stack through the inside of an enclosure that surrounds the fuel cell stack is problematic in that an additional heater must be mounted, and the structural change of the fuel cell stack is required, thus complicating the arrangement design of component parts and increasing production costs. In addition, there is a problem in that excessive time is required to operate a heater and raise the temperature of the fuel cell stack to a suitable level.

SUMMARY

Accordingly, the present disclosure has been made keeping in mind the above problems occurring in the related art, and an object of the present disclosure is to provide a motor torque control method for an air blower, which can rapidly raise the temperature of a fuel cell stack by operating the motor of the air blower of a fuel cell vehicle at low efficiency.

In order to accomplish the above object, the present disclosure provides a motor torque control method for an air blower, including setting a phase current command value of a motor of the air blower based on a temperature of the motor; calculating a d-axis current command value other than zero in compliance with the set phase current command value; and outputting the calculated d-axis current command value.

The d-axis current command value may be calculated using the set phase current command value and a q-axis current command value determined in compliance with an input speed command value.

A value at which the phase current command value is set may decrease as the temperature of the motor of the air blower increases.

The motor torque control method may further include determining whether a present condition is a cold-start condition in which an external temperature of a fuel cell vehicle is less than or equal to a preset temperature, wherein the phase current command value of the motor may be set based on the temperature of the motor only when it is determined that the present condition is a cold-start condition.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG. 1 is a graph showing a relationship between a q-axis current command i_q* and a d-axis current command i_d* in a conventional permanent magnet synchronous motor control system;

FIG. 2 is a graph showing d-axis and q-axis current commands in the low-efficiency operation of the motor of an air blower according to embodiments of the present disclosure; and

FIG. 3 is a flowchart showing a motor torque control method for an air blower according to embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Specific structural or functional descriptions related to embodiments according to the present disclosure and disclosed in the present specification or application are merely illustrated to describe embodiments of the present disclosure, and the embodiments of the present disclosure may be implemented in various forms and should not be interpreted as being limited to the embodiments described herein. The embodiments according to the present disclosure may be modified in various manners and may have various forms, so that specific embodiments are intended to be illustrated in the drawings and described in detail in the present specification or application. However, it should be understood that those embodiments are not intended to limit the embodiments based on the concept of the present invention to specific disclosure forms and they include all changes, equivalents or modifications included in the spirit and scope of the present disclosure.

The terms such as “first” and “second” may be used to describe various components, but those components should not be limited by the terms. The terms are merely used to distinguish one component from other components, and a first component may be designated as a second component and a second component may be designated as a first component in the similar manner, without departing from the scope based on the concept of the present disclosure.

Throughout the entire specification, it should be understood that a representation indicating that a first component is “connected” or “coupled” to a second component may include the case where the first component is connected or coupled to the second component with some other component interposed therebetween, as well as the case where the first component is “directly connected” or “directly coupled” to the second component. In contrast, it should be understood that a representation indicating that a first component is “directly connected” or “directly coupled” to a second component means that no component is interposed between the first and second components.

Other representations describing relationships among components, that is, “between” and “directly between” or “adjacent to,” and “directly adjacent to,” should be interpreted in similar manners.

The terms used in the present specification are merely used to describe specific embodiments and are not intended to limit the present disclosure. A singular expression includes a plural expression unless a description to the contrary is specifically pointed out in context. In the present specification, it should be understood that the terms such as “include” or “have” are merely intended to indicate that features, numbers, steps, operations, components, parts, or combinations thereof are present, and are not intended to exclude a possibility that one or more other features, numbers, steps, operations, components, parts, or combinations thereof will be present or added.

It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles.

Unless differently defined, all terms used here including technical or scientific terms have the same meanings as the terms generally understood by those skilled in the art to which the present invention pertains. The terms identical to those defined in generally used dictionaries should be interpreted as having meanings identical to contextual meanings of the related art, and are not interpreted as being ideal or excessively formal meanings unless they are definitely defined in the present specification.

Additionally, it is understood that the below methods may be executed by at least one controller. The term “controller” refers to a hardware device that includes a memory and a processor. The memory is configured to store program instructions, and the processor is configured to execute the program instructions to perform one or more processes which are described further below. Moreover, it is understood that the below methods may be executed by an apparatus comprising the controller, whereby the apparatus is known in the art to be suitable for performing a motor torque control method for an air blower, which can rapidly raise the temperature of a fuel cell stack in a cold-start condition.

Furthermore, the controller of the present disclosure may be embodied as non-transitory computer readable media on a computer readable medium containing executable program instructions executed by a processor, controller or the like. Examples of the computer readable mediums include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards and optical data storage devices. The computer readable recording medium can also be distributed in network coupled computer systems so that the computer readable media is stored and executed in a distributed fashion, e.g., by a telematics server or a Controller Area Network (CAN).

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the attached drawings. The same reference numerals are used throughout the different drawings to designate the same or similar components.

FIG. 2 is a graph showing d-axis and q-axis current commands in the low-efficiency operation of the motor of an air blower according to embodiments of the present disclosure. Referring to FIG. 2, it can be seen that a d-axis current command i_d* is not zero as in the case of FIG. 1. When the d-axis current command is not zero, it means that the efficiency of a current command value for the required torque is not 100%. The motor acts as a single additional load because the d-axis current command is not operated at maximum efficiency when the motor of the air blower is operated. As the motor is not operated at the maximum efficiency, that is, as much power is used for the same output, thermal energy is generated, and the temperature of the fuel cell stack may be raised via the thermal energy. Further, since much power is used, the consumption of electric power generated by the fuel cell stack is further increased, so that the required output of the fuel cell stack is increased, thus further activating an electrochemical reaction in the fuel cell stack. As a result, a heating value is increased, and thus the temperature of the fuel cell stack can be rapidly raised.

Further, in the conditions in which low-efficiency operation of the motor, other than maximum-efficiency operation, is required, as well as a cold-start condition, for example, in the flooded state of the fuel cell stack or in a case where the high voltage battery is in a fully-charged state during driving on a long downhill road, the motor of the air blower may be operated as an additional load.

FIG. 3 is a flowchart showing a motor torque control method for an air blower according to embodiments of the present disclosure.

Referring to FIG. 3, it is determined whether a present condition is a cold-start condition in which the external temperature of the fuel cell vehicle is equal to or less than a preset temperature at step S301. If it is determined that the present condition is a cold-start condition, the phase current command value I_s of the motor of the air blower is set based on the temperature of the motor at step S303. Such a phase current command value I_s may be determined based on the temperature of the motor and the current capacity of the Insulated Gate Bipolar Transistor (IGBT) of an inverter.

If the phase current command value I_s of the motor of the air blower is set based on the temperature of the motor, a d-axis current command value i_d* other than zero is calculated in compliance with the set phase current command value at step S305. Then, the calculated d-axis current command value may be output at step S309. The d-axis current command value is calculated using the set phase current command value I_s and a q-axis current command value i_q* determined in compliance with an input speed command value. The phase current command value may be set to a smaller value as the temperature of the motor of the air blower increases, whereas it may be set to a larger value as the temperature of the motor of the air blower decreases.

A relationship between the set phase current command value, the d-axis current command value and the q-axis current command value may be represented by the following Equation (1):

i_d*=I_s²−i_q*²  (1)

That is, as the value of I_s is set to a larger value, the d-axis current command value is increased. Further, as the temperature of the motor is lower, the d-axis current command value is increased.

In conditions other than the cold-start condition, the d-axis current command value is set to zero as in existing schemes, and the q-axis current command value may be the output of a speed controller at step S307. The determined d-axis current command value and q-axis current command value are output to a current controller (not shown).

In accordance with the motor torque control method for an air blower according to embodiments of the present disclosure, there is an advantage in that the current command value of the air blower is adjusted to operate the motor at low efficiency, so that, as required power is increased, an electrochemical reaction in a fuel cell stack can be increased, and a heating value can also be increased, thus rapidly raising the temperature of the fuel cell stack. Further, the motor of the air blower is operated as an additional load, thus preventing the air blower from being operated at an open circuit voltage and preventing the fuel cell stack from being flooded. Furthermore, when a high voltage battery is in a fully-charged state, regenerative braking energy can be consumed by the motor of the air blower.

Although the embodiments of the present disclosure have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the disclosure as disclosed in the accompanying claims. Therefore, the technical scope of the present disclosure should be defined by the technical spirit and scope of the accompanying claims.

Claims

1. A motor torque control method for an air blower, comprising:

setting, by a controller, a phase current command value of a motor of the air blower based on a temperature of the motor;

calculating, by the controller, a d-axis current command value other than zero in compliance with the set phase current command value; and

outputting, by the controller, the calculated d-axis current command value.

2. The motor torque control method of claim 1, wherein the d-axis current command value is calculated using the set phase current command value and a q-axis current command value determined in compliance with an input speed command value.

3. The motor torque control method of claim 1, wherein a value at which the phase current command value is set decreases as the temperature of the motor increases.

4. The motor torque control method of claim 1, further comprising determining, by the controller, whether a present condition is a cold-start condition in which an external temperature of a fuel cell vehicle is less than or equal to a preset temperature, wherein

the phase current command value of the motor is set based on the temperature of the motor only when it is determined that the present condition is a cold-start condition.

5. A motor torque control apparatus for an air blower, comprising:

a memory configured to store program instructions; and

a processor configured to execute the program instructions so as to perform a process including: setting a phase current command value of a motor of the air blower based on a temperature of the motor, calculating a d-axis current command value other than zero in compliance with the set phase current command value, and outputting the calculated d-axis current command value.

6. A non-transitory computer readable medium containing program instructions for performing a motor torque control method for an air blower, executed by a processor or controller, the computer readable medium comprising:

program instructions that set a phase current command value of a motor of the air blower based on a temperature of the motor;

program instructions that calculate a d-axis current command value other than zero in compliance with the set phase current command value; and

program instructions that output the calculated d-axis current command value.