阅读说明：本技术 马达驱动控制方法和系统 (Motor drive control method and system ) 是由 康敏绣 柳昌锡 金成道 李东勋 于 2020-07-30 设计创作，主要内容包括：本发明提供一种用于控制马达速度以使马达的速度实测值跟随速度指令值的马达驱动控制方法。该方法包括以下步骤：基于速度指令值,通过以预定周期重复在马达中产生扭矩的开启区间和在马达中不产生扭矩的关闭区间来驱动马达,其中在驱动步骤中,在开启区间通过脉冲宽度调制方式仅对马达的多个相位中的一个相位施加相电压。(The invention provides a motor drive control method for controlling a motor speed so that an actual speed measurement value of a motor follows a speed command value. The method comprises the following steps: the motor is driven by repeating an on-period in which torque is generated in the motor and an off-period in which torque is not generated in the motor at a predetermined cycle based on the speed command value, wherein in the driving step, a phase voltage is applied to only one of a plurality of phases of the motor by a pulse width modulation manner in the on-period.)

1. A motor drive control method for controlling a motor speed so that a speed measured value of a motor follows a speed command value, comprising the steps of:

driving the motor by repeating an on interval in which torque is generated in the motor and an off interval in which torque is not generated in the motor at a predetermined cycle based on the speed command value,

wherein in the driving step, a phase voltage is applied to only one of the phases of the motor by a pulse width modulation method in the on interval.

2. The method of claim 1, wherein,

in the driving step, control is performed to always turn on or always turn off a phase to which the phase voltage is not applied among the plurality of phases of the motor in the on section.

3. The method of claim 1, wherein,

the start and end points of the on interval are respectively determined before and after a point of time at which a q-axis in a rotating coordinate system of the motor intersects an axis corresponding to one phase to which the phase voltage is applied in a fixed coordinate system.

4. The method of claim 1, wherein,

the driving step includes the steps of:

determining a target phase corresponding to one phase of the phase voltage to be applied for the open interval among the plurality of phases of the motor;

determining whether a q-axis in a rotating coordinate system of the motor is close to an axis in a fixed coordinate system corresponding to the target phase; and

when it is determined that the q-axis in the rotating coordinate system of the motor approaches the axis corresponding to the target phase in the fixed coordinate system by a predetermined angle, the phase voltage is applied only to the target phase through the pulse width modulation manner for a time corresponding to the on-interval.

5. The method of claim 4, wherein,

in the step of applying the phase voltages, control is performed to always turn on or always turn off the remaining phases other than the target phase for a time corresponding to the turn-on interval.

6. The method of claim 4, wherein,

the start point and the end point of the on-interval are respectively determined before and after a time point at which the q-axis in the rotating coordinate system of the motor intersects with an axis in the fixed coordinate system corresponding to one phase to which the phase voltage is applied.

7. The method of claim 1, wherein,

in the driving step, control is performed to make a driving current supplied to the motor substantially zero in the off interval.

8. The method as recited in claim 7, wherein,

in the driving step, a switching element included in an inverter that supplies a driving current to the motor is turned off in the off section.

9. The method of claim 7, wherein,

in the driving step, a switching element included in an inverter that applies a driving voltage to the motor is controlled so that the driving voltage applied to the motor in the off section is substantially equal to a back electromotive force of the motor.

10. A motor drive control system comprising:

a speed controller that determines a current command value of a drive current for driving a motor so that a speed measured value of the motor follows the speed command value of the motor;

a current controller that determines a voltage command value for driving the motor so that a motor drive current measured value of an inverter provided to the motor follows the current command value;

a voltage output converter that converts the voltage command value and performs on/off control of a switching element included in the inverter based on the voltage command value; and

a torque on/off determiner determining whether to perform a torque on/off mode for driving the motor by repeating an on interval in which torque is generated in the motor and an off interval in which torque is not generated in the motor at a predetermined period,

wherein the voltage output converter controls the inverter to apply a phase voltage to only one phase among a plurality of phases of the motor through a pulse width modulation scheme in the on-interval when the torque on/off determiner determines to perform the torque on/off mode.

11. The system of claim 10, wherein,

when the torque on/off determiner determines to execute the torque on/off mode, the voltage output converter controls the inverter to always turn on or always turn off a phase to which the phase voltage is not applied among the plurality of phases of the motor in the on section.

12. The system of claim 10, wherein,

the start and end points of the on interval are respectively determined before and after a point of time at which a q-axis in a rotating coordinate system of the motor intersects an axis corresponding to one phase to which the phase voltage is applied in a fixed coordinate system.

13. The system of claim 10, wherein,

when the torque on/off determiner determines to execute the torque on/off mode, the voltage output converter controls the switching element included in the inverter to apply the phase voltage only to a target phase corresponding to one phase to which the phase voltage is applied in the on section by the pulse width modulation manner within a preset time corresponding to the on section from a point in time when a q-axis in a rotational coordinate system of the motor approaches a predetermined angle of an axis corresponding to the target phase in a fixed coordinate system.

14. The system of claim 10, wherein,

when the torque on/off determiner determines to execute the torque on/off mode, the voltage output converter controls the switching element included in the inverter to make a driving current supplied to the motor substantially zero during the off period.

15. The system of claim 14, wherein,

the voltage output converter turns off the switching element included in the inverter in the off section when the torque on/off determiner determines to execute the torque on/off mode.

16. The system of claim 14, wherein,

when the torque on/off determiner determines to execute the torque on/off mode, the voltage output converter controls the switching element included in the inverter so that the applied driving voltage to the motor in the off section is substantially equal to a back electromotive force of the motor.

17. The system of claim 14, wherein,

the speed controller determines the current command value to be zero when the motor torque is off when the torque on/off determiner determines to execute the torque on/off mode.

18. The system of claim 10, wherein,

the torque on/off determiner determines to execute the torque on/off mode when the speed command value or the current command value is within a preset range.

19. A motor drive control method comprising:

determining a current command value of a drive current for driving a motor so that a speed measured value of the motor follows the speed command value of the motor;

determining a voltage command value for driving the motor so that a motor drive current measured value of an inverter provided to the motor follows the current command value;

converting the voltage command value, and performing on/off control of a switching element included in the inverter based on the voltage command value;

determining whether to perform a torque on/off mode for driving the motor by repeating an on interval in which torque is generated in the motor and an off interval in which torque is not generated in the motor at a predetermined cycle; and

when it is determined that the torque on/off mode is to be executed, the inverter is controlled such that a phase voltage is applied to only one of a plurality of phases of the motor by a pulse width modulation scheme in the on section, and such that a phase to which the phase voltage is not applied is always on or always off in the plurality of phases of the motor in the on section.

20. The method of claim 19, further comprising:

the start and end points of the on interval are respectively determined before and after a point of time at which a q-axis in a rotating coordinate system of the motor intersects an axis in a fixed coordinate system corresponding to one phase to which the phase voltage is applied.

Technical Field

The invention relates to a motor drive control method and system.

Background

When the fuel cell stack is operated at a high output under an operation condition where the cooling performance of the fuel cell vehicle is low, such as a high-temperature hill-climbing operation, the operating temperature of the fuel cell stack increases, the humidity of the supplied fuel decreases, and thus the fuel cell stack is dried, resulting in a drop in the stack operating voltage at the same current. In this case, a vicious circle may occur in which the heating value of the fuel cell stack increases due to a decrease in the stack voltage, and the operating temperature of the fuel cell further increases.

In order to prevent vicious cycles of an increase in the operating temperature of the fuel cell, a control technique of increasing the relative humidity of the cathode side by increasing the air pressure supplied to the cathode (cathode) is applied in recent years in a fuel cell system for a vehicle. Therefore, it is necessary to further increase the compression ratio of the air compressor that supplies air to the cathode side of the fuel cell stack.

Since it is necessary to further increase the compression ratio of the air supplied to the cathode side of the fuel cell stack, the air compressor is designed such that the compression ratio of the air compressor is further increased and shows the maximum efficiency point at the maximum pressure operation point. This design leads to an improvement in compressor efficiency in the high-flow high-compression-ratio section, but causes a problem of a decrease in efficiency in the relatively low-flow section. Therefore, when driving a vehicle in the city center, the power consumption of the air compressor is increased in the low flow rate section, which is the main driving section, thereby adversely affecting the fuel efficiency of the vehicle.

More specifically, since the booster-type air compressor, which further increases the air compression ratio as compared to the normal pressure type blower used in the related art, should further increase the driving speed of the built-in motor, the difference in the driving speed of the motor between the low flow rate section and the high flow rate section increases, so that there is a disadvantage that it is difficult to increase the efficiency of the air compressor itself. That is, the supercharged air compressor reduces the motor inductance to ensure a sufficient voltage margin with an increase in the motor rotation speed in the high-speed operation section, and the reduction in the motor inductance causes an increase in the three-phase ripple current, thereby reducing the efficiency of the motor/inverter. Particularly in a low-flow interval requiring relatively small output, the three-phase current is small, so that the current ripple is increased, and the efficiency reduction effect is remarkable. That is, the three-phase ripple current does not contribute to the motor torque as the secondary element, and the three-phase ripple current amount is relatively large compared to the three-phase sinusoidal current component in the low flow rate section where the motor torque is small, and therefore the motor/inverter efficiency is reduced compared to the high output section.

In addition, in order to rotate at a high speed, a wing bearing (airfoil bearing) is used for the motor rotation of the air compressor, and the wing bearing needs to rotate at a speed higher than a predetermined speed to maintain a lift state. Therefore, when the wing bearing continuously drives the motor at a speed of a predetermined speed or less to maintain the lift state, there is a problem that the wing bearing may be burned out by friction with the motor rotation shaft. Thus, to prevent the airfoil bearings from burning out, the air compressor has a minimum drive speed limit. Therefore, even if the fuel cell needs to operate at a low output, the air compressor is driven at a speed above the minimum driving speed, avoiding unnecessary air supply, thereby reducing the efficiency of the fuel cell system itself.

In order to solve these problems, korean registered patent No. 10-1988088 (applicant: modern automobile corporation) proposes a technique of performing motor torque on/off (on/off) control in a low speed region. According to the related patent, the inverter applies a control method in a driving torque on state of the motor: all phase switches of the motor are controlled by controlling a pulse width modulation duty ratio (duty) determined by the controller, thereby applying three-phase voltages of the motor. Compared with the conventional method of controlling the motor torque to the always-on state, the control method of the related patent has a torque-off section, and thus can prevent inverter switching loss, conduction loss, and current ripple loss, thereby improving efficiency.

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

Disclosure of Invention

The invention relates to a motor drive control method and system. The embodiment relates to a motor driving control method and system capable of remarkably improving motor efficiency by reducing current ripple loss and switching loss of an inverter in a low-speed driving section of a high-speed motor.

Embodiments of the present invention have been made keeping in mind the problems occurring in the prior art, and embodiments of the present invention provide a motor drive control method and system capable of minimizing switching loss and current ripple loss of an inverter, performing control such that a motor designed to generate maximum efficiency at a high speed repeatedly generates an on-interval of motor torque and an off-interval of no motor torque at a low speed, while controlling inverter switching elements such that only a phase voltage corresponding to one phase of the motor is applied in the on-interval.

An embodiment of the present invention provides a motor drive control method for controlling a motor speed so that a speed measured value of a motor follows a speed command value, the method including the steps of: the motor is driven by repeating an on-period in which torque is generated in the motor and an off-period in which torque is not generated in the motor at a predetermined cycle based on the speed command value, wherein in the driving step, a phase voltage is applied to only one of a plurality of phases of the motor by a pulse width modulation manner in the on-period.

According to an embodiment of the present invention, in the driving step, control may be performed to always turn on or always turn off a phase to which no phase voltage is applied among the plurality of phases of the motor, during the turn-on interval.

According to an embodiment of the present invention, the start point and the end point of the on-interval may be determined before and after a time point at which the q-axis in the rotational coordinate system of the motor intersects the axis corresponding to one phase of the applied phase voltage in the fixed coordinate system, respectively.

According to an embodiment of the present invention, the driving step may include the steps of: determining a target phase corresponding to one phase to which a phase voltage is to be applied in an on interval among a plurality of phases of the motor; determining whether a q-axis in a rotating coordinate system of the motor is close to an axis corresponding to the target phase in a fixed coordinate system; and applying a phase voltage to only the target phase by a pulse width modulation manner during a time corresponding to the on interval when it is determined in the determining step that the q axis in the rotating coordinate system of the motor approaches an axis corresponding to the target phase in the fixed coordinate system by a predetermined angle.

According to an embodiment of the present invention, in the step of applying the phase voltages, control may be performed to always turn on or always turn off the remaining phases except for the target phase for a time corresponding to the turn-on interval.

According to an embodiment of the present invention, the start point and the end point of the on-interval may be determined before and after a time point at which the q-axis in the rotational coordinate system of the motor intersects the axis corresponding to one phase of the applied phase voltage in the fixed coordinate system, respectively.

According to an embodiment of the present invention, in the driving step, control may be performed to make the driving current supplied to the motor substantially zero in the off interval.

According to an embodiment of the present invention, in the driving step, the switching elements included in the inverter that supplies the driving current to the motor may be turned off (off) in the off section.

According to an embodiment of the present invention, in the driving step, the switching element included in the inverter that applies the driving voltage to the motor may be controlled such that the driving voltage applied to the motor in the off section is substantially equal to the back electromotive force of the motor.

In addition, an embodiment of the present invention provides a motor drive control system including: a speed controller that determines a current command value of a drive current for driving the motor so that a speed actual measurement value of the motor follows the speed command value of the motor; a current controller that determines a voltage command value for driving the motor so that a motor drive current actual measurement value of an inverter actually supplied to the motor follows the current command value; a voltage output converter that converts the voltage command value and performs on/off (on/off) control of switching elements included in the inverter based on the voltage command value; and a torque on/off determiner determining whether to perform a torque on/off mode for driving the motor by repeating an on interval in which torque is generated in the motor and an off interval in which torque is not generated in the motor at a predetermined period, wherein when the torque on/off determiner determines to perform the torque on/off mode, the voltage output converter controls the inverter such that the phase voltage is applied to only one phase among the phases of the motor by a pulse width modulation manner at the on interval.

According to an embodiment of the present invention, when the torque on/off determiner determines to perform the torque on/off mode, the voltage output converter may control the inverter to always turn on or always turn off a phase to which the phase voltage is not applied among the phases of the motor in the turn-on section.

According to an embodiment of the present invention, the start and end of the on-interval may be determined before and after a time point at which a q-axis in a rotational coordinate system of the motor intersects an axis corresponding to one phase of the applied phase voltage in a fixed coordinate system, respectively.

According to an embodiment of the present invention, when the torque on/off determiner determines that the torque on/off mode is executed, the voltage output converter may control the switching elements included in the inverter to apply the phase voltage only to the target phase by the pulse width modulation manner within a preset time corresponding to an on-period from a point in time when a q-axis in a rotational coordinate system of the motor approaches a predetermined angle with respect to an axis corresponding to the target phase corresponding to one phase to which the phase voltage is applied in the on-period in a fixed coordinate system.

According to an embodiment of the present invention, when the torque on/off determiner determines to perform the torque on/off mode, the voltage output converter may control the switching element included in the inverter to substantially zero the driving current supplied to the motor in the off section.

According to an embodiment of the present invention, the voltage output converter may turn off the switching elements included in the inverter in the off section when the torque on/off determiner determines to perform the torque on/off mode.

According to an embodiment of the present invention, when the torque on/off determiner determines to perform the torque on/off mode, the voltage output converter may control the switching element included in the inverter such that the driving voltage applied to the motor in the off section is substantially equal to the back electromotive force of the motor.

According to an embodiment of the present invention, when the torque on/off determiner determines to perform the torque on/off mode, the speed controller may determine the current command value to be zero when the motor torque is off.

According to an embodiment of the present invention, the torque on/off determiner may determine to perform the torque on/off mode when the speed command value or the current command value is within a preset range.

According to the motor drive control method and system, the efficiency of a system to which the motor is applied can be improved by reducing power consumption of the motor. In particular, in a fuel cell vehicle including an air compressor to which a motor is applied, the efficiency of the fuel cell system and the fuel efficiency of the vehicle can be improved by reducing power consumption by the air compressor.

In addition, according to the motor drive control method and system, any cost is not incurred due to the addition of additional hardware, and power consumption of the motor is easily reduced by performing on/off control of the motor torque in a specific speed section or a specific torque section.

In particular, according to the motor drive control method and system, when the motor torque on/off control is performed, the maximum torque is obtained in the corresponding phase by using only one of the phases of the motor in the on section where the motor torque is generated, so that it is possible to surely reduce the switching loss and the current ripple loss of the inverter.

Further, according to the motor drive control method and system, not only the efficiency of the motor in the constant speed driving state but also the efficiency in the acceleration/deceleration driving state of the motor can be improved.

The effects obtained in the embodiments of the present invention are not limited to the above-described effects, and other effects not mentioned above may be clearly understood by those skilled in the art from the following description.

Drawings

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

fig. 1 is a block diagram schematically showing an example of a fuel cell system to which a motor drive control method and system are applied according to an embodiment of the invention;

FIG. 2 is a block diagram illustrating a motor drive control system according to an embodiment of the present invention;

fig. 3 is a flowchart illustrating a motor drive control method according to an embodiment of the present invention;

fig. 4 is a graph showing a motor torque on/off control state applied to a motor driving control method according to an embodiment of the present invention;

FIG. 5 is a flowchart illustrating in more detail the steps of performing a torque on/off mode in a motor drive control method according to an embodiment of the present invention;

fig. 6 is a diagram showing a state of each phase in a motor torque-on interval and a motor torque-off interval applied in the motor drive control method and system according to the embodiment of the present invention; and

fig. 7 is a graph showing a relationship between a q-axis in a rotational coordinate system of a motor torque-on interval applied in a motor drive control method and system according to an embodiment of the present invention and one of three phase axes to which a phase voltage is applied by a pulse width modulation scheme.

Detailed Description

Hereinafter, a motor drive control method and system according to exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 is a block diagram schematically showing an example of a fuel cell system to which a motor drive control method and system are applied according to an embodiment of the present invention.

As shown in fig. 1, the fuel cell system may include: a fuel cell stack 100 including fuel cell units that receive hydrogen gas as a fuel and air as an oxidant to generate electric power through oxidation/reduction; an air compressor 10 supplying compressed air to a cathode (cathode) of the fuel cell stack 100; and a humidifier 200 supplying moisture to the compressed air of the air compressor 10 and delivering the compressed air to the fuel cell stack 100. Here, the humidifier 200 receives unreacted air of high humidity discharged from the fuel cell stack 100 and provides moisture to the air supplied to the fuel cell stack 100.

As described in the background art, in order to prevent drying of hydrogen due to heat generation of the fuel cell stack when high output is required in the fuel cell stack 100, the compression ratio of air supplied to the fuel cell stack 100 is increased. That is, the flow rate of air is increased by operating the air compressor 10 at a higher speed to further supply humidified air to the fuel cell stack 100, thereby avoiding the drying phenomenon.

In order to achieve control of the air compressor 10, a controller 20 for controlling the air compressor 10, more precisely, a motor included in the air compressor 10 may be provided in the fuel cell system.

In describing the respective embodiments of the present invention, a motor control method implemented in the controller 20 for controlling the motor of the air compressor 10 included in the fuel cell system and a motor control system including the air compressor 10 and the controller 20 are taken as application examples. However, the described application example is not limited to the air compressor of the fuel cell system, and the technique of the invention can be widely applied to the control of various motors in other technical fields than the field of fuel cells.

Fig. 2 is a block diagram of a motor drive control system according to an embodiment of the present invention.

Referring to fig. 2, the motor drive control system according to the embodiment of the present invention may include a speed controller 21, a current controller 23, a voltage output converter 25, an inverter 27, and a torque on/off determiner 29. In fig. 2, the motor is given the same reference numeral "10" as the air compressor of fig. 1. This is because the various embodiments of the present invention are for controlling the driving of a motor, and particularly, for controlling the driving of a motor included in an air compressor in a fuel cell system, and thus, controlling the air compressor can be understood as being substantially the same as controlling the motor of the air compressor. In addition, controlling the air compressor throughout this specification may be understood to mean controlling the motor of the air compressor.

The speed controller 21 receives a speed command for controlling the motor speed from a host controller (not shown), and generates and outputs current command values (Id, Iq) of drive currents for driving the motor based on a motor speed measured value obtained by actually detecting the motor speed. Here, the upper controller may be a controller for controlling the fuel cell system or a vehicle controller for controlling a vehicle to which the fuel cell system is applied. The upper controller may determine the output of the fuel cell stack 100 based on the vehicle speed, the vehicle climbing angle, the opening degree of an accelerator operated by the driver, and the like, and may determine the motor rotation speed in consideration of the output and the temperature of the fuel cell stack 100. The upper controller supplies the determined motor rotation speed as a speed command value to the speed controller 21. The speed controller 21 compares the received speed command value with a motor speed measured value corresponding to an actual motor rotation speed to generate and output current command values (Id, Iq) so that the motor rotation speed can follow the speed command value.

Here, the current command values (Id, Iq) are command values for the drive current of the motor 10. Generally, when controlling a motor, a target torque of the motor is set and a driving current of the motor is controlled so that the motor follows the target torque. Since the embodiment of the present invention is applied to control the speed of the motor, the speed controller 21 determines a target torque, which the speed measured value can follow the speed command value, based on the speed measured value and the speed command value, and generates a current command value corresponding to the target torque to control the motor to follow the target speed command value. More specifically, the current command values (Id, Iq) output from the speed controller 21 may be a d-axis current command value and a q-axis current command value of the motor.

The speed controller 21 may apply a control technique, such as a Proportional Integral (PI) controller, that accumulates and reflects the error between the command value and the measured value in the control amount by integrating the error between the command value and the measured value. That is, the speed controller 21 may apply a control technique of integrating and reflecting an error between the speed command and the actual speed of the motor 10. In addition to the PI control technique, the speed controller 21 may apply a technique such as Proportional Integral Derivative (PID) control, Integral Proportional (IP) control, or IP-PI hybrid control.

Meanwhile, the motor 10 is provided with a sensor 13, such as a hall sensor or a resolver, for detecting the position of the motor rotor. A speed actual measurement value obtained by detecting the actual rotation speed of the motor 10 by the sensor 13 is supplied to the speed controller 21, and a current command value is generated.

The current controller 23 performs control so that the current supplied from the inverter 27 to the motor follows the current command values (Id, Iq), and outputs d-axis and q-axis voltage command values (Vd, Vq). The current controller 23 detects a part or all of the current supplied from the inverter 27 to each phase of the motor 10, and performs control to receive feedback of the driving current measured values converted into the d-axis current and the q-axis current, and to make the driving current measured values follow the current command values, i.e., the d-axis current command value and the q-axis current command values (Id, Iq).

As with the speed controller 21 described above, the current controller 23 may use a control technique including an integration process for accumulating an error between the actual current supplied from the inverter 27 to the motor and the current command value (Id, Iq), such as PI control, PID control, IP-PI hybrid control, or the like.

The voltage output converter 25 converts the d-axis voltage command value and the q-axis voltage command values (Vd, Vq) into three-phase voltage command values by coordinate conversion (DQ < - > three-phase (abc)), and generates drive signals for driving the switching elements in the inverter 27 based on the converted three-phase voltage command values and supplies the drive signals to the inverter 27. As the driving signal controls the switching of the switching elements in the inverter 27, the inverter 27 outputs three-phase currents for driving the motor 10.

In addition, the voltage output converter 25 may convert the measured values of the three-phase driving currents of the inverter 27 fed back to the current controller 23 for control again into DQ currents and supply them to the current controller 23.

In particular, when it is judged that it is necessary to control the motor 10 in a torque on/off mode in which an on interval in which the torque of the motor 10 is generated and an off interval in which the torque of the motor 10 is not generated are repeated at a predetermined cycle, the voltage output converter 25 may control the motor 10 to repeat the on interval and the off interval of a preset time interval. Whether to enter the torque on/off mode may be performed by the torque on/off determiner 29.

The torque on/off determiner 29 receives a speed command value supplied to the speed controller 21 or a current command value (Id, Iq) generated by the speed controller 21, and determines to perform torque on/off when the speed command value or the current command value (Id, Iq) is within a preset range.

When the torque on/off determiner 29 determines that it is necessary to repeatedly perform torque on/off of the motor 10, the determination result of the torque on/off determiner 29 may be provided to the voltage output converter 25 and the current controller 23. The voltage output converter 25, which receives the determination result of the torque on/off determiner 29, transmits a signal for controlling switching elements in the inverter 27 to turn on/off the torque of the motor 10. In addition, the current controller 23 receiving a command from the torque on/off determiner 29 enables appropriate control in the torque off section.

The torque on/off control of the motor will be more clearly understood through the following description of the motor driving control method according to the embodiment of the present invention.

Fig. 3 is a flowchart illustrating a motor drive control method according to an embodiment of the present invention. The embodiment shown in fig. 3 relates to an example of executing the motor torque on/off control when the speed command value or the current command value of the motor is within a preset range. The features of the embodiment of the present invention, to which the torque on/off pattern that repeats the on interval in which the motor torque is generated and the off interval in which the motor torque is not generated at a predetermined cycle is applied, are not limited to the specific conditions used in the example shown in fig. 3, and may be applied to the motor drive regardless of the magnitude of the speed command value or the current command value.

Referring to fig. 3, when the motor 10 is in the stopped state (S11), a non-zero speed command value is input to the speed controller 21 (S12), and control for generating the motor torque is started.

When the speed command value is input to the speed controller 21, the speed controller 21 derives a current command value (Id, Iq) for executing control and outputs the current command value (Id, Iq) to the current controller 23. So that the measured value of the speed of the motor 10 follows the speed command value. The current controller 23 derives and outputs the voltage command values (Vd, Vq) so that current measured values corresponding to values directly detecting the drive current supplied from the inverter 27 to the motor 10 follow the current command values (Id, Iq). The voltage output converter 25 converts the voltage command values (Vd, Vq) of the DQ coordinate into three-phase (u-phase, v-phase, and w-phase) voltages, generates PWM switching signals for controlling switching elements in the inverter 27, and outputs to the inverter 27 to output each three-phase voltage.

The driving of the motor is started through such a series of processes. The motor drive control method according to the exemplary embodiment of the present invention monitors the speed command value or the current command value by the torque on/off determiner 29 after the start of the driving of the motor 10 to determine whether to perform the torque on/off mode (S131, S132). That is, the torque on/off determiner 29 may determine to perform the torque on/off mode when the speed command value is within a preset range (greater than zero and less than a (positive number) in fig. 3) (S131) or the current command value is within a preset range (greater than zero and less than B (positive number) in fig. 3) (S132).

When the torque on/off determiner 29 determines that the torque on/off mode needs to be performed, the torque on/off determiner 29 may instruct the voltage output converter 25, which outputs a driving signal for controlling on/off (on/off) of the switching elements included in the inverter 27, to perform the torque on/off mode, and the voltage output converter 25 may control the switching elements in the inverter 27 according to the instruction (S14).

Fig. 4 is a graph illustrating a motor torque on/off control state applied to a motor driving control method according to an embodiment of the present invention.

As shown in fig. 4, according to an embodiment of the present invention, in step S14 of fig. 3, a torque on/off mode may be performed in which an on interval D1 in which motor torque is generated and an off interval D2 in which motor torque is not generated are repeated at a predetermined cycle. The time interval of the on-interval D1, the time interval of the off-interval D2, and the period of repeating the on-interval D1 and the off-interval D2 may be experimentally determined in advance to values at which the power consumption for each motor speed inverter is minimum and the operation stability can be ensured.

This torque on/off mode is preferably applied to a case where the speed of the motor 10 is not greatly changed by inertia driving even if the load affecting the motor 10 is small. When the load of the motor 10 is large, since deceleration is mainly generated in the torque-off interval, acceleration/deceleration of the motor speed due to repetition of torque on/off is large, and thus unnecessary energy loss may occur. Therefore, when the motor load is large, the effectiveness of the torque on/off repetitive control is significantly reduced. In particular, when the acceleration/deceleration amount of the motor speed due to the torque on/off control exceeds a predetermined level, there is a problem in that the power consumption of the motor 10 increases.

In addition, as the moment of inertia of the motor 10 increases, the influence of the on/off control on the motor torque may increase. That is, when the moment of inertia of the motor 10 is large, the speed fluctuation is small even in the torque-off section, so that the efficiency of the torque on/off control can be improved.

According to the embodiment of the present invention, as a specific technique of the motor torque on/off repetition control, a technique of applying a phase voltage to only one phase among a plurality of phases of the motor 10 by a pulse width modulation method at the on interval D1 where the motor torque is generated may be used. When the phase voltage is applied to only one phase of the motor instead of the phases at the turn-on interval D1, the switching frequency of the switching elements in the inverter 27 can be relatively reduced. In contrast, since only one phase is used to drive the motor, it is preferable to perform control so that the maximum torque is generated in the corresponding phase.

Fig. 5 is a flowchart illustrating in more detail the steps of performing the torque on/off mode in the motor drive control method according to the embodiment of the present invention. Fig. 6 is a diagram illustrating a state of each phase in a motor torque-on interval and a motor torque-off interval applied in the motor drive control method and system according to the embodiment of the present invention. In addition, fig. 7 is a graph showing a relationship between a q-axis in a rotational coordinate system of a motor torque-on interval applied in a motor drive control method and system according to an embodiment of the present invention and one of three phase axes to which a phase voltage is applied by a pulse width modulation scheme.

Referring to fig. 5 to 7, a torque on/off mode of the motor drive control method according to an embodiment of the present invention will be more clearly understood.

Referring to fig. 5, the step of controlling the motor in the torque on/off mode (S14 of fig. 3) includes: a step (S141) of determining a target phase, which is one phase to which a phase voltage is to be applied in the open section D1, among the multiple phases (u-phase, v-phase, and w-phase) of the motor 10; a step (S142) of determining whether or not a q-axis in a rotating coordinate system of the motor is close to an axis corresponding to the target phase in a fixed coordinate system; a step (S143) of applying a phase voltage to only the target phase by a pulse width modulation manner for a time Deltat corresponding to a preset on-interval D1 when it is determined that the q-axis in the rotational coordinate system of the motor approaches an axis corresponding to the target phase in the fixed coordinate system to a predetermined angle; and a step (S145) of entering the closing interval D2 after the time Deltat has elapsed.

In general, when space vector pulse width modulation control for controlling a motor is executed, in a rotational coordinate system of the motor, a q-axis is a point where a maximum torque is generated, and a d-axis is a point where no torque is generated. With such motor characteristics, as shown in fig. 6, in step S143, an on-interval D1 in which motor torque is generated is set when the q-axis in the rotational coordinate system of the motor approaches the axis of the target phase (u-phase in fig. 6) corresponding to one phase selected from the u-phase, v-phase, and w-phase in the fixed coordinate system, and pulse width modulation control is performed on the selected one phase at the on-interval D1, whereby the maximum torque can be generated on the selected one phase.

In this case, the remaining phases other than the selected one may be controlled to be always on or always off.

That is, as shown in fig. 7, the start time point of the open interval D1 may be a time point at which the q-axis in the rotating coordinate system rotates to approach the axis corresponding to one phase selected from among the three phases in the selected fixed coordinate system by a predetermined angle, and the end time point of the open interval D1 may be a time point at which the q-axis in the rotating coordinate system rotates and deviates by a predetermined angle through the axis corresponding to one phase from among the three phases in the fixed coordinate system. Therefore, the start point and the end point of the open section D1 may be respectively determined before and after the time point at which the q-axis in the rotating coordinate system of the motor 10 intersects the axis corresponding to the target phase in the fixed coordinate system.

As described above, according to the embodiments of the present invention, switching control of an inverter according to a predetermined pulse width modulation duty ratio is performed only for one target phase to generate a phase voltage corresponding to one phase in an on-period, and switching control is not performed for the remaining phases, thereby preventing inverter switching loss, conduction loss, and current ripple loss. That is, the efficiency according to the embodiment of the present invention can be significantly improved as compared to the method of performing the switching control on all of the plurality of phases of the motor at the turn-on interval D1. In addition, since the switching control time point of the target phase is controlled such that the axis of the target phase of the motor is synchronized with the q-axis in the rotational coordinate system of the motor, it is possible to generate the maximum torque that can be implemented as the target phase, thereby preventing a reduction in speed following performance.

Referring again to fig. 3, in the section where the motor torque is set to off, the switching elements included in the inverter 27 are all off (off) (100% off duty ratio) to block the driving current supplied to the motor. That is, in the interval in which the motor torque remains off, the voltage output converter 25 may output a control signal for turning off all the switching elements to the inverter 27.

The inverter 27 that provides torque (drive current) for driving the three-phase motor typically implements a three-phase switching full-bridge circuit using six switching elements (e.g., IGBTs, etc.). The current controller 23 compares the current command value with the measured motor driving current, and outputs a voltage command value (DQ coordinate) whose error can be reduced. The voltage output converter 25 converts the voltage command value into a three-phase voltage and determines the duty ratio of the switching elements so that the converted three-phase voltage can be applied to the motor 10, thereby performing on/off control of the switching elements of each phase.

In the motor drive control method according to the embodiment of the invention, the torque on/off control repeats the on interval and the off interval at a predetermined cycle. Here, in the torque-on section, the inverter switching elements are controlled to apply a phase voltage to one of the phases of the motor as described above, and in the torque-off section, the inverter switching elements are all turned off, thereby performing the torque-on/off mode.

As another method of controlling the switching elements of the inverter 27 at the torque-off interval D2, a method of performing on/off control of the switching elements of each phase in the inverter 27 to generate a driving voltage having a voltage magnitude substantially equal to the counter electromotive force generated in the motor 10 may be applied. When the back electromotive force of the motor 10 is the same as the three-phase drive voltage of the inverter 27, no potential difference occurs, and therefore a zero-current control state in which no current is supplied from the inverter 27 to the motor 10, that is, a state in which no motor torque is generated may occur.

When the motor torque on/off control, i.e., the torque on/off mode, is performed (S14), the integration control performed by the current controller 23 is preferably stopped (S161) during the motor torque off interval (S15). When the current controller 23 allows integration of the error between the command value and the measured value in the motor torque off interval, a large output is applied from each controller due to the integration error at the time point when the torque is turned on again, causing system instability, and the effect of the torque on/off control is seriously hindered due to the change in the speed command value and the current command value. Of course, in the motor torque on interval (S15), the integration control is preferably performed by the current controller 23 (S162).

As another example, instead of the method of stopping the integral control of the current controller 23 in the motor torque off section, a method of stopping the entire control operation and outputting the current command value as zero in the motor torque off section when the speed controller 21 changes the motor torque from on to off may be applied. That is, the three-phase output is blocked by causing the speed controller 21 to output the current command value as zero, so that the integration in the current controller 23 due to the error between the current command value and the measured current is interrupted in the torque-off interval in which no torque and output are generated. Therefore, it is possible to prevent an excessive output from being generated due to an accumulated error at a time point when the motor torque is turned on again. Of course, normal speed controller operation may resume when the motor torque should change from the off state to the on state. Since the operation of the speed controller 21 is stopped during the motor torque off interval, when the motor torque is turned on again, the output of the speed controller 21 is maintained at the output value just before the motor torque is turned off, thereby ensuring the stability of the speed control without unnecessary acceleration and deceleration.

Meanwhile, when the motor speed exceeds the preset range or the current command output from the current controller 23 exceeds the preset range, the torque on/off determiner 29 enables a typical control method in which the three-phase driving current of the inverter 27 is determined according to the current command value without performing the torque on/off mode (S17). As described above, when the speed of the motor 10 is equal to or higher than the preset speed, the load torque on the motor side is increased (for example, in the fuel cell system, the load torque of the air compressor is increased due to the increase in the flow rate and pressure when the speed is increased), and thus the amount of deceleration generated in the torque-off interval of the motor 10 should be compensated in the torque-on interval, thereby generating an unnecessary amount of acceleration and deceleration, which are generated in excess of the switching loss and the three-phase current ripple loss reduced by the torque-on/off control. When the current command value is equal to or higher than the preset value, it can be regarded as a rapid acceleration region or a high-speed rotation state, and thus the motor torque on/off repetitive control method is less efficient than a typical continuous torque application method.

As one of the cases where the above-described current command is out of the preset range, there may be a case where regenerative braking torque is applied to the motor. When regenerative braking is performed, torque is applied in a direction opposite to the rotational direction, which is regarded as a state where the torque is negative. Therefore, it can be regarded that the current command value is out of the range greater than 0 and less than B (positive number) in step S132 of fig. 3. Even in the case where the motor is decelerated to perform regenerative braking, it is preferable to stop the motor torque on/off control. This is because in the regenerative braking state, it is advantageous in terms of efficiency to recover energy by continuous motor torque control.

As described above, the motor drive control method and system according to various embodiments of the present invention may improve the efficiency of a system to which a motor is applied by reducing power consumption of the motor. In particular, in a fuel cell vehicle including an air compressor to which a motor is applied, by reducing power consumption by the air compressor, the efficiency of the fuel cell system and the fuel efficiency of the vehicle can be improved.

In addition, the motor drive control method and system according to various embodiments of the present invention do not incur costs due to the addition of separate hardware, and can easily reduce power consumption of the motor by performing motor torque on/off control in a specific speed section or a specific torque section.

In particular, in the motor drive control method and system according to various embodiments of the present invention, when the motor torque on/off control is performed, the maximum torque is obtained in the corresponding phase by using only one phase among the phases of the motor in the section where the motor torque is generated, so that it is possible to ensure reduction of the switching loss and the current ripple loss of the inverter and to significantly improve the efficiency.

In addition, according to the motor drive control method and system, not only the efficiency of the motor in the constant speed driving state can be improved, but also the efficiency of the motor in the acceleration/deceleration driving state can be provided.

While the invention has been shown and described with respect to certain embodiments, it will be apparent to those skilled in the art that various modifications and changes may be made without departing from the inventive concept as provided by the appended claims.