阅读说明：本技术 用于驱动电机的逆变器控制装置和方法 (Inverter control apparatus and method for driving motor ) 是由 李镕在 河泰元 裴秀炫 申昊埈 金成奎 朴柱英 于 2018-12-05 设计创作，主要内容包括：本发明涉及一种用于驱动电机的逆变器控制装置,包括：电流控制器,其生成电压指令,该电压指令用于使测定由逆变器提供至电机的电流而得到的电流检测值跟踪用于驱动电机的电流指令；电压调制部,其生成脉冲宽度调制信号,该脉冲宽度调制信号基于上述电压指令以规定开关频率控制上述逆变器内开关元件的接通/关闭状态；和频率确定部,其基于上述电机的驱动信息来随机地变更上述开关频率。(The present invention relates to an inverter control device for driving a motor, including: a current controller that generates a voltage command for causing a current detection value obtained by measuring a current supplied to the motor by the inverter to follow a current command for driving the motor; a voltage modulation unit that generates a pulse width modulation signal that controls an on/off state of a switching element in the inverter at a predetermined switching frequency based on the voltage command; and a frequency determination unit that randomly changes the switching frequency based on the drive information of the motor.)

1. An inverter control device for driving a motor, characterized by comprising:

a current controller that generates a voltage command for causing a current detection value obtained by measuring a current supplied to the motor from the inverter to follow a current command for driving the motor;

a voltage modulation unit that generates a pulse width modulation signal that controls an on/off state of a switching element in the inverter at a predetermined switching frequency based on the voltage command; and

and a frequency determination unit that randomly changes the switching frequency based on the drive information of the motor.

2. The inverter control device for driving a motor according to claim 1, wherein:

the frequency determination section determines a change width of the switching frequency based on the drive information, and randomly changes the switching frequency within the determined change width.

3. The inverter control device for driving a motor according to claim 1, wherein:

the frequency determination section includes:

a random frequency band generation unit that determines a change width of the switching frequency based on the drive information;

a random number generation unit that randomly determines a constant within a predetermined range;

a fundamental frequency generation unit that generates a fundamental frequency as a reference for determining the switching frequency; and

and an adder for determining the switching frequency by adding the fundamental frequency generated by the fundamental frequency generation unit to a value obtained by multiplying the change width determined by the random frequency band generation unit by the constant generated by the random number generation unit.

4. The inverter control device for driving a motor according to claim 3, wherein:

the random frequency band generation unit includes:

a cost function calculation unit that calculates a cost value using a cost function in which all of the plurality of pieces of input drive information are variables; and

and a data map in which the frequency change width mapped to the cost value is stored in advance, the cost value calculated by the cost function calculation unit is input, and the frequency change width mapped thereto is output.

5. The inverter control device for driving a motor according to claim 3, wherein:

the random frequency band generation unit includes:

a plurality of cost function calculation units each including a cost function having the input drive information as a variable, and each calculating a cost value for the drive information; and

and a data map in which the frequency change width mapped to the cost value is stored in advance, a maximum value of the cost values calculated by the cost function calculation units is input, and the frequency change width mapped to the maximum value is output.

6. The inverter control device for driving a motor according to claim 1, wherein:

the drive information includes at least one of the current command, the current detection value, the temperature of the inverter, the temperature of the motor, and the speed of the motor.

7. The inverter control device for driving a motor according to claim 4 or 5, characterized in that:

the cost function calculation unit includes a cost function that outputs a higher cost value as the input drive information shows a higher tendency to exhibit a state of reduced controllability, and the data map constructs a map such that the frequency change width is reduced as the cost value is larger.

8. The inverter control device for driving a motor according to claim 3, wherein:

the random number generation unit randomly determines a constant value in a range of-1 or more and 1 or less.

9. The inverter control device for driving a motor according to claim 1, further comprising:

and a voltage modulation unit that generates a triangular wave-shaped carrier signal having a frequency corresponding to the switching frequency, and compares the voltage command with the carrier signal to generate the pulse width modulation signal in a rectangular wave form.

10. An inverter control method for driving a motor, comprising:

a step of generating a fundamental frequency as a reference for determining a switching frequency of a switching element within an inverter;

determining a frequency change width for changing the switching frequency based on drive information of a motor driven by receiving drive power from the inverter;

a step of randomly determining a constant value within a predetermined range; and

and a step of determining the switching frequency by adding the fundamental frequency to a value obtained by multiplying the frequency change amplitude by the constant.

11. The inverter control method for driving a motor according to claim 10, further comprising the steps of:

a triangular wave-shaped carrier signal having a frequency corresponding to the switching frequency determined in the step of determining the switching frequency is generated, and a rectangular wave-shaped pulse width modulation signal is generated by comparing a voltage command determined such that a current detection value obtained by measuring a current supplied to a motor by the inverter follows a current command for driving the motor with the carrier signal.

12. The inverter control method for driving a motor according to claim 10, wherein:

in the step of determining the amplitude of the frequency change,

calculating a cost value using a cost function in which all of the plurality of pieces of drive information are used as variables, and inputting the calculated cost value in a data map in which the frequency change amplitude mapped to the cost value is stored in advance, thereby determining the frequency change amplitude.

13. The inverter control method for driving a motor according to claim 10, wherein:

in the step of determining the amplitude of the frequency change,

calculating a plurality of cost values using respective cost functions using the respective motor drive information as variables, and inputting a maximum value among the plurality of cost values in a data map storing in advance the frequency change width mapped to the cost values, thereby determining the frequency change width.

14. The inverter control method for driving a motor according to claim 10, wherein:

the drive information includes at least one of a current command for driving the motor, a current detection value obtained by measuring a current supplied from the inverter to the motor, a temperature of the inverter, a temperature of the motor, and a speed of the motor.

15. The inverter control method for driving a motor according to claim 12 or 13, wherein:

the cost function outputs a higher cost value as the driving information shows a higher tendency to a state of reduced controllability, and the data map constructs a map so that the frequency change width is reduced as the cost value is higher.

16. The inverter control method for driving a motor according to claim 10, wherein:

in the step of determining a constant, the constant is randomly determined in a range of-1 or more and 1 or less.

Technical Field

The present invention relates to an inverter control device for driving a motor, and more particularly, to an inverter control device and method for driving a motor, which randomly changes a pulse width modulation frequency of an inverter that supplies driving power to the motor, and appropriately sets a change width of the pulse width modulation frequency in consideration of various environments and factors that drive the motor, thereby being capable of minimizing a reduction in controllability and efficiency of the motor and reducing switching noise.

Background

In general, a system for driving a motor may include: a power storage device (e.g., a battery); an inverter that converts the dc power stored in the power storage device into 3-phase ac power for driving the motor; and a controller for controlling the switching of the inverter based on a current command generated based on the motor and a torque command for driving the motor and a measured current actually supplied to the motor.

The inverter includes a plurality of switching elements, and the plurality of switching elements are controlled by a Pulse Width Modulation (PWM) method, whereby ac power can be generated. The ac power generated by the inverter is supplied to the motor, thereby operating the motor.

When the pulse width modulation signal for controlling the switching elements in the inverter has a fixed frequency, the control becomes simple and the controllability is excellent, whereby the entire motor drive system can be stably controlled. However, when the inverter is controlled by making the pulse width modulation signal a fixed frequency, there is a disadvantage that strong harmonic components occur in a frequency band corresponding to an integral multiple of the switching frequency to cause electromagnetic noise and vibration.

In order to solve the disadvantages caused by such a Pulse Width Modulation signal of a fixed switching frequency, a Random Pulse Width Modulation (RPWM) technique that instantaneously disperses a switching frequency band is known. When the random pulse width modulation technique is applied, although noise and vibration can be suppressed by energy dispersion, there is a problem that controllability is deteriorated because the switching frequency is randomly changed.

The matters described as background above are only for enhancement of understanding of the background of the invention and should not be construed as an admission that they are prior art known to those skilled in the art.

Disclosure of Invention

Technical problem to be solved by the invention

Accordingly, an object of the present invention is to provide an inverter control apparatus and method for driving a motor, which randomly varies a pulse width modulation frequency of an inverter that supplies driving power to the motor, and appropriately sets a variation width of the pulse width modulation frequency in consideration of various environments and factors that drive the motor, thereby being capable of minimizing a reduction in controllability and efficiency of the motor and reducing switching noise.

Technical solution for solving technical problem

As a means for solving the above-described problems, the present invention provides an inverter control device for driving a motor, comprising:

a current controller that generates a voltage command for causing a current detection value obtained by measuring a current supplied to the motor from the inverter to follow a current command for driving the motor;

a voltage modulation unit that generates a pulse width modulation signal that controls an on/off state of a switching element in the inverter at a predetermined switching frequency based on the voltage command; and

and a frequency determining unit that randomly changes the switching frequency based on the drive information of the motor.

In one embodiment of the present invention, the frequency determining unit may determine a change width of the switching frequency based on the driving information, and randomly change the switching frequency within the determined change width.

In one embodiment of the present invention, the frequency determining unit may include: a random frequency band generating unit for determining a change width of the switching frequency based on the drive information; a random number generation unit that randomly determines a constant within a predetermined range; a fundamental frequency generation unit that generates a fundamental frequency as a reference for determining the switching frequency; and an adder for determining the switching frequency by adding the fundamental frequency generated by the fundamental frequency generation unit to a value obtained by multiplying the change width determined by the random frequency band generation unit by the constant generated by the random number generation unit.

In one embodiment of the present invention, the random frequency band generating unit may include: a cost function calculation unit that calculates a cost value using a cost function in which all of the plurality of pieces of input drive information are variables; and a data map in which the frequency change width mapped to the cost value is stored in advance, the cost value calculated by the cost function calculation unit is input, and the frequency change width mapped thereto is output.

In one embodiment of the present invention, the random frequency band generating unit may include: a plurality of cost function calculation units each including a cost function having a variable of each of the plurality of input drive information, and each calculating a cost value for the drive information; and a data map in which the frequency change width mapped to the cost value is stored in advance, a maximum value of the cost values calculated by the cost function calculation units is input, and the frequency change width mapped to the maximum value is output.

In one embodiment of the present invention, the driving information may include: the current command, the current detection value, the temperature of the inverter, the temperature of the motor, and the speed of the motor.

In one embodiment of the present invention, the cost function calculation unit may include a cost function that outputs a higher cost value as the tendency of the input drive information to show a state of reduced controllability is higher, and the data map may construct a map such that the frequency change width is reduced as the cost value is higher.

In one embodiment of the present invention, the random number generation unit may randomly determine the constant value in a range of-1 or more and 1 or less.

An embodiment of the present invention may further include: and a voltage modulation unit that generates a triangular-wave-shaped carrier signal having a frequency corresponding to the switching frequency, and generates the pulse width modulation signal in a rectangular wave form by comparing the voltage command with the carrier signal.

As another technical solution to solve the above technical problem, the present invention may provide an inverter control method for driving a motor, including:

a step of generating a fundamental frequency as a reference for determining a switching frequency of a switching element within an inverter;

determining a frequency change width for changing the switching frequency based on drive information of a motor driven by receiving drive power from the inverter;

a step of randomly determining a constant value within a predetermined range; and

and determining the switching frequency by adding the fundamental frequency to a value obtained by multiplying the frequency change width by the constant.

An embodiment of the present invention may further include the steps of: the step of determining the switching frequency generates a carrier signal having a triangular wave shape with a frequency corresponding to the switching frequency determined in the step of determining the switching frequency, and compares a voltage command determined such that a current detection value obtained by measuring a current supplied to the motor by the inverter follows a current command for driving the motor with the carrier signal to generate the pulse width modulation signal having a rectangular wave shape.

In one embodiment of the present invention, in the step of determining the frequency change width, a cost value may be calculated by using a cost function in which all of the plurality of drive information is used as a variable, and the calculated cost value may be input to a data map in which the frequency change width mapped to the cost value is stored in advance, thereby determining the frequency change width.

In one embodiment of the present invention, in the step of determining the frequency change width, a plurality of cost values are calculated by using respective cost functions having the respective plurality of motor drive information as variables, and a maximum value among the plurality of cost values is input to a data map storing the frequency change width mapped to the cost values in advance, thereby determining the frequency change width.

In one embodiment of the present invention, the driving information may include the current command, the current detection value, a temperature of the inverter, a temperature of the motor, and a speed of the motor.

In one embodiment of the present invention, the cost function outputs a higher cost value as the tendency of the state in which the drive information display controllability is lowered is higher, and the data map may construct a map so that the frequency change width is reduced as the cost value is higher.

In one embodiment of the present invention, in the step of determining the constant, the constant may be randomly set within a range of-1 or more and 1 or less.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the inverter control device and method for driving a motor described above, by randomly changing the switching frequency of the inverter, it is possible to prevent a large harmonic component from being generated at a specific frequency, thereby having an effect of significantly reducing switching noise and the like.

In particular, in the inverter control device and method for driving a motor, since a change width of a switching frequency that affects controllability is determined in consideration of a plurality of types of motor drive information, appropriate controllability can be maintained even in a state where controllability is degraded, such as a state where a difference between a motor current command and an actual current supplied to the motor is large, or a state where a temperature of the motor or the inverter excessively rises.

Drawings

Fig. 1 is a circuit diagram of a motor drive system to which an inverter control device and method for driving a motor according to an embodiment of the present invention are applied.

Fig. 2 is a block diagram illustrating the configuration of an inverter control device for driving a motor according to an embodiment of the present invention in more detail.

Fig. 3 is a block diagram illustrating the configuration of the frequency determination unit of the inverter control device for driving the motor according to the embodiment of the present invention in more detail.

Fig. 4 and 5 are block diagrams illustrating in more detail a plurality of examples of the random frequency band generating unit for determining the frequency change width in the inverter control device for driving the motor according to the embodiment of the present invention.

Fig. 6 is a flowchart of an inverter control method for driving a motor according to an embodiment of the present invention.

Description of the reference numerals

10: energy storage device 20: DC link voltage (inverter input voltage)

30: inverter 40: electric machine

50: rotation angle sensor

100: controller (Motor drive inverter control device)

110: current command map 120: current control task part

121: the current controller 123: voltage modulation unit

125: frequency determination section 61: random frequency band generation unit

611. 611a to 611 e: cost function calculation unit

612: maximum value selecting unit 613: data diagram

63: random number generation unit 65: fundamental frequency generating unit

67: adder

Detailed Description

Embodiments of the present invention are described in detail so that those skilled in the art to which the present invention pertains can easily carry out the present invention.

Hereinafter, inverter control devices and methods for driving a motor according to various embodiments will be described in more detail with reference to the accompanying drawings.

Fig. 1 is a circuit diagram of a motor drive system to which an inverter control device for driving a motor according to an embodiment of the present invention is applied.

Referring to fig. 1, a motor driving system to which an inverter control device for driving a motor according to an embodiment of the present invention is applied may include an energy storage device (10), a dc link capacitor (20) connected between both ends of the energy storage device, an inverter (30), a motor (40), a rotation angle sensor (50), and a controller (100).

The energy storage device (10) is a means for storing electric energy for driving the motor (30) in the form of direct current, such as a battery, and outputs direct current power.

A DC link capacitor (20) is connected across the energy storage device (10) and forms a DC link voltage (Vdc) upon charging. The DC link voltage (Vdc) is an input voltage of the inverter (30).

The inverter (30) is a means for converting dc power stored in the energy storage device (10) into ac power for driving the motor, and may include: a plurality of switching elements (S1 to S6) controlling on/off states in accordance with a pulse width modulation signal provided by a controller (100). The switching of the inverter (30) is understood to mean the switching of the three-phase voltage output by the inverter.

The motor (40) is a member that receives three-phase ac power supplied from the inverter (30) to generate rotational force, and various types of motors known in the art may be employed. In an environment-friendly vehicle, a motor that provides a rotational force to a driving wheel of the vehicle may also be referred to as a driving motor.

The rotation angle sensor (50) is a member that detects the position of the rotor of the motor, that is, the rotation angle of the rotor of the motor, detects the angle of the rotor of the motor (40), and can continuously output a rotation angle detection signal including information on the detected rotation angle of the rotor. For example, the rotation angle sensor (40) may be implemented by a resolver or the like.

The controller (100) can perform control of a pulse width modulation method for appropriately adjusting the duty cycle of the switching elements (S1-S6) of the inverter (30) in order to basically control the torque of the motor (40) to a desired value (torque command). For this control, the controller (100) derives torque-related information of the motor (40) in driving, based on a signal supplied from the rotation angle sensor (50) and values (Ia, Ib) that detect the current supplied to the motor (40).

Next, the controller (100) controls the switching elements (S1-S6) in the inverter (30) so that the motor (40) can output a value corresponding to the torque command value, based on the result of comparing the externally input torque command value for the motor (40) (the torque target value desired to be obtained by the motor (40)) with the torque-related information of the motor (40) in the present drive.

In one embodiment of the present invention, a controller (100) generates a pulse Width Modulation signal by a Random Pulse Width Modulation (RPWM) method in which the frequency of a pulse Width Modulation signal for controlling the on/off of switching elements (S1-S6) in an inverter (30) is randomly determined. In particular, the controller (100) appropriately determines the frequency change amplitude of the pulse width modulation signal using various motor drive information to minimize the reduction in controllability and efficiency of the motor by applying a random pulse width modulation scheme and to reduce switching noise generated by frequency concentration.

In the system shown in fig. 1, the controller (100) may be the inverter control device according to the present invention, and the inverter control method executed by the controller (100) may be the inverter control method according to the present invention.

Fig. 2 is a block diagram illustrating in more detail the structure of an inverter control device for driving a motor according to an embodiment of the present invention, and it can be understood that the inverter control device illustrates: the specific configuration of the controller (100) of fig. 1 and a system including an inverter (30) controlled by the controller (100), a motor (40) driven by applying 3-phase voltages from the inverter (30), and the like.

Referring to fig. 2, an inverter control apparatus (controller (100) of fig. 1) for driving a motor according to an embodiment of the present invention may include: a current command map (110) which receives a torque command and a back-magnetic flux of the motor inputted from the outside and outputs a current command (IdqREF) of the motor corresponding thereto; a current control task unit (120) that compares a current command (IdqREF) and a current detection value obtained by detecting a current supplied to the motor (30) with each other, generates a voltage command (VdqssrEF) for causing the current detection value to track the current command (IdqREF), and generates a gate signal that controls the on/off of the switching element (S1-S6) by pulse width modulation so as to generate an output of the inverter (20) corresponding to the voltage command (VdqssrEF); a coordinate conversion unit (130) that converts the values obtained by detecting the phase currents (Ia, Ib) supplied to the motor (40) into d/q-axis currents (Idq); and a speed estimation unit (140) that derives the rotational speed of the motor (40) using the position of the motor rotor detected by the rotational angle sensor (50).

The current command map (110) may store in advance a current command (IdqREF) mapped to both a torque command for the motor (40) and a back-magnetic flux of the motor (40). Thus, the current command map (110) receives a torque command of the motor inputted from an external host controller or the like and a detected value of a back-magnetic flux outputted from the motor, and outputs a current command (IdqREF) corresponding thereto. The current command (IdqREF) may have the form of a d/q-axis current command of a stationary coordinate system.

Although the current command map (110) has been described in the embodiment of fig. 2 as outputting the current command (IdqREF) mapped to two values with the torque command for the motor (40) and the demagnetizing flux of the motor (40) as inputs, this is merely an example, and the current command may be output using a map in which the current command is mapped with respect to other input values. The current command map (110) is merely an example of a system that can be applied to generate a current, and a current command may be derived by substituting a specific input value into a predetermined equation and performing an operation in a system other than a map.

The current control task part (120) may include a current controller (121), a voltage modulation part (123), and a frequency determination part (125).

The current controller (121) can receive a d/q-axis current command (IdqREF) from a current command map (110), convert current detection values (Ia, Ib) of actually measured currents supplied to the motor into values (Idq) of the d/q-axis current from a coordinate conversion unit (130), and receive an estimated rotation speed (rotation frequency) (ω r) of the motor from a speed estimation unit (140). The current controller (121) may generate a voltage command (vdqsref) using the received information.

More specifically, the current controller (121) can generate the voltage command (vdqsreff) using a difference component between the d/q-axis current command (IdqREF) output by the current command map (110) and the measured d/q-axis current (Idq). In particular, the current controller (121) may be implemented in the form of a Proportional Integral (PI) controller, and may generate a d/q-axis voltage command (vdqssrf) that is controllable to cause a d/q-axis current (IdqREF) measured so as to proportionally integrate a difference component between the d/q-axis current command (IdqREF) and the measured d/q-axis current (Idq) to track the current command (IdqREF).

A voltage modulation unit (123) receives a voltage command (Vdqsref) and a switching frequency (or carrier frequency) generated by a frequency determination unit (125), and generates a pulse width modulation signal that determines the on/off state of a switching element in an inverter (30) based on the voltage command (Vdqsref) and the switching frequency (or carrier frequency). For example, the voltage modulation unit (125) generates a carrier signal in a triangular wave form based on the switching frequency (carrier frequency) determined by the frequency determination unit (125), and can generate a pulse width modulation signal in a rectangular wave form by comparing the carrier signal with the d/q-axis voltage command (vdqsreff). The pulse width modulation signal outputted from the voltage modulation unit (123) is supplied to the gates (gate) of the switching elements (S1-S6) in the inverter (30), and the on/off of the switching elements (S1-S6) is determined, whereby the 3-phase alternating voltage (3-phase alternating current) supplied from the inverter (30) to the motor (40) can be determined.

The frequency determination unit (125) is a means for determining the switching frequency of the inverter (30), and can randomly determine the switching frequency within a predetermined range and supply the switching frequency to the voltage modulation unit (123). In particular, the frequency determination unit (125) receives various information on the driving of the motor (40), determines the change width of the switching frequency based on the information, and can determine the switching frequency that changes randomly within the determined change width.

Fig. 3 is a block diagram illustrating the configuration of the frequency determination unit of the inverter control device for driving the motor according to the embodiment of the present invention in more detail.

Referring to fig. 3, the frequency determination section (125) may include: a random frequency band generation unit (61) that determines a change width (Frand) of a switching frequency for changing the frequency of the pulse width modulation signal; a random number generation unit (61) that specifies a random number (Krand) that is a random constant in a range of-1 or more and 1 or less and that is used to multiply the switching frequency change width (Frand) specified by the random band generation unit (61); a fundamental frequency generation unit (65) that generates a fundamental frequency (Fbase) that is a reference of the switching frequency; an adder (67) adds the fundamental frequency (Fbase) to a frequency determined by multiplying the random number (Krand) by the frequency change width (Frand), thereby determining the switching frequency (Fsw).

A frequency determination unit (125) determines a switching frequency (Fsw) which is randomly changed by adding a random frequency change value to the fundamental frequency (Fbase) determined by the fundamental frequency generation unit (65). The fundamental frequency generation unit (65) can determine the switching fundamental frequency by using a switching frequency determination method applied to another pulse width modulation method that generates a pulse width modulation signal at a fixed switching frequency.

For this purpose, a random frequency band generation unit (61) sets a frequency change width (Frand), and multiplies a random number (Krand) having a value of-1 or more and 1 or less by the frequency change width (Frand) to thereby randomly determine a frequency change value within the frequency change width.

A switching frequency (Fsw) determined by adding a frequency change value (Krand x Frand) to a fundamental frequency (Fbase) by an adder (67) is supplied to a voltage modulation unit (123), and the voltage modulation unit generates a pulse width modulation signal having a frequency corresponding to the switching frequency (Fsw) (corresponding to a carrier frequency). As described above, the voltage modulation unit (125) generates a carrier signal in a triangular wave form according to the switching frequency (Fsw) (carrier frequency) determined by the frequency determination unit (125), and can generate a pulse width modulation signal in a rectangular wave form by comparing the carrier signal with the d/q-axis voltage command (vdqsref).

On the other hand, in one embodiment of the present invention, the frequency change width may be determined using at least a part of various motor drive information such as a drive environment and a control state of the motor. That is, the random frequency band generating section (61) is inputted with the motor drive information and can determine the frequency based thereon.

Fig. 4 and 5 are block diagrams illustrating in more detail a plurality of examples of the random frequency band generating unit for determining the frequency change width in the inverter control device for driving the motor according to the embodiment of the present invention.

First, referring to fig. 4, the random band generating part (61) may include: a cost function calculation unit (611) to which various types of motor drive information are input, and which generates a cost value (Cmon) as a reference for determining the frequency change width (Frand) using one cost function in which each of the input motor drive information is used as a variable; a data map (613) stores in advance a frequency change width (Frand) mapped to a cost value (Cmon) and outputs the frequency change width (Frand) mapped to the cost value (Cmon) input by the cost function calculation unit (611).

The motor drive information input to the cost function calculation unit (611) may be d/q current commands (Id _ ref, Iq _ ref) corresponding to a torque command for driving the motor, current detection values (Id, Iq) obtained by detecting a current supplied from the inverter (30) to the motor (40), a rotation speed (ω rpm) of the motor (40), a temperature (Tinv) of the inverter (30), a temperature (Tmot) of the motor (40), and the like.

The cost function calculation unit (611) may include a cost function for generating a reference value (cost value) that can specify an appropriate switching frequency change width (Frand) using the various types of input motor drive information. The cost function is an expression in which the input motor drive information is used as a variable, and a weight value can be given to the motor drive information according to the type thereof as needed.

The data map 613 stores in advance the frequency change amplitude (Frand) mapped to the value of the representative value (Cmon), and when the input of the value of the representative value (Cmon) occurs, the frequency change amplitude (Frand) mapped to the input value of the representative value (Cmon) can be output. The data map (613) may have the following form: the frequency variation range (Frand) has its limits set for very low cost values or very high cost values. That is, the frequency change width (Frand) can be determined appropriately based on the cost value in a range between the maximum value and the minimum value by setting the maximum value and the minimum value in advance. The maximum value of the frequency change width (Frand) is a value that can generate the maximum switching frequency that can stably control the motor (40), and the minimum value of the frequency change width (Frand) can be 0, which corresponds to a case where the switching frequency is not changed by setting the switching frequency to the fundamental frequency.

Referring to fig. 5 illustrating another example of the random band generating part (61), the random band generating part (61) may include: a plurality of cost function calculation units (611a to 611e) that calculate cost functions for each of the d/q current commands (Id _ ref, Iq _ ref), d/q current detection values (Id, Iq) obtained by detecting a current supplied from the inverter (30) to the motor (40), the rotational speed (ω rpm) of the motor (40), the temperature (Tinv) of the inverter (30), and the temperature (Tmot) of the motor (40); a maximum value selection unit (612) that selects a maximum value from the cost values (Cmon1 to Cmon5) calculated by the cost function calculation units (611a to 611 e); and a data map (613) for storing the frequency change width (Frand) mapped to the cost value (Cmon), inputting the cost value selected by the maximum value selection unit (612), and outputting the frequency change width (Frand) corresponding thereto.

Unlike the example shown in fig. 4, in the example shown in fig. 5, cost function calculation units (611a to 611e) are applied to values calculated using each or a part of the plurality of pieces of input motor drive information to calculate a plurality of cost values, and then the frequency change width (Frand) for the maximum value among the calculated cost values (Cmon1 to Cmon5) can be determined.

For example, the first cost function calculation unit (611a) can calculate the cost value using a cost function having as variables the d/q current commands (Id _ ref, Iq _ ref) and the average value (Ierr) of the difference values between the d/q current detection values (Id, Iq) obtained by detecting the current supplied from the inverter (30) to the motor (40).

The second cost function calculation unit (611b) can calculate a cost value using a cost function having the inverter temperature (Tinv) as a variable, and the third cost function calculation unit (611c) can calculate a cost value using a cost function having the motor temperature (Tmot) as a variable. The fourth cost function operation unit (611d) can calculate the cost value by using a cost function having the average (Iamp) of the d/q current detection values as a variable, and the fifth cost function operation unit (611e) can calculate the cost value by using a cost function having the rotational speed (rpm) of the motor (40) as a variable.

Among the cost values thus calculated, the maximum value selection unit (612) selects the maximum value from among the plurality of cost values (Cmon1 to Cmon5) so that the switching frequency change width is determined in consideration of the information that is most affected by the random change of the switching frequency, and the data map (613) can determine the frequency change width (Frand) with the cost value having the maximum value as an input, as described with reference to fig. 4.

In fig. 4 and 5, the cost function may output a higher cost value as the input motor drive information shows a higher tendency to exhibit a state of reduced controllability, and the data map may be configured such that the frequency change width (Frand) is reduced as the input cost value is larger. For example, it is considered that the larger the average value (Ierr) of the difference values between the d/q current commands (Id _ ref, Iq _ ref) and the d/q current detection values (Id, Iq) obtained by detecting the current supplied from the inverter (30) to the motor (40), the more the motor control cannot be appropriately performed. In this case, the larger the average value (Ierr), the more the cost value increases, and the more the frequency change amplitude of the data map output may decrease. That is, in one embodiment of the present invention, under the condition that an increase in controllability is required, the frequency change width can be reduced to reduce the noise reduction effect, while the controllability can be improved. Examples of the drive information with reduced controllability include an increase in inverter temperature (Tinv), an increase in motor temperature (Tmot), an increase in average (Iamp) of d/q current detection values, and an increase in motor rotation speed (ω rpm). By driving the information, the cost value increases as the controllability decreases, and thus the frequency change width (Frand) may decrease.

The frequency change value is determined by multiplying the frequency change width (Frand) determined by the random band generating unit (61) which can be realized by the example shown in fig. 4 or fig. 5 by an arbitrary random number (Krand) in the range of-1 or more and 1 or less generated by the random number generating unit (63), and the switching frequency (Fsw) is determined by adding the frequency change value to the fundamental frequency (Fbase) generated by the fundamental frequency generating unit (65).

In another aspect, the present invention also provides an inverter control method using the above-described inverter control device for driving a motor.

Fig. 6 is a flowchart of an inverter control method for driving a motor according to an embodiment of the present invention.

Referring to fig. 6, an inverter control method for driving a motor according to an embodiment of the present invention may be started from a step (S12) of generating a fundamental frequency (Fbase) in a fundamental frequency generating unit (65) for switching of an inverter (30) (S11), and inputting motor driving information to a random frequency band generating unit (61) to determine a frequency change width (Frand). Of course, a general inverter control, for example, a control in which a current command is generated based on a torque command of the motor (40) inputted from the outside and a voltage command is generated by comparing the current command with a current detection value obtained by detecting an actual current supplied to the motor (40), may be performed immediately after the motor drive is started.

In the step (S11) of generating the fundamental frequency (Fbase), the fundamental frequency may be generated by applying a fixed switching frequency other than the random pulse width modulation method to the pulse width modulation method.

In step (S12), as described with reference to fig. 4 and 5, a method may be selectively applied in which all of the plurality of pieces of motor drive information are used as variables to generate one cost value, and then the frequency change width (Frand) corresponding to the one cost value is determined using the data map, or the cost values for each of the plurality of pieces of motor drive information are generated, and then the frequency change width (Frand) corresponding to the one cost value is determined based on the maximum value among the plurality of cost values.

In addition, in parallel with the steps (S11, S12), a random number (Krand) having a random value in the range of-1 or more and 1 or less may be generated by the random number generation unit (63), and the frequency change value may be determined by multiplying the frequency change width (Frand) by the random number (Krand) in the step (S13).

Then, the adder (67) adds the frequency change value to the fundamental frequency (Fbase) to determine the switching frequency (Fsw) of the pulse width modulation signal for controlling the inverter (30), and supplies the switching frequency (Fsw) to the voltage modulation unit (123) (S14).

Next, the voltage modulation unit (123) receives the voltage command (vdqsref) and the switching frequency (Fsw) (or carrier frequency) generated by the adder (67) and generates a pulse width modulation signal that determines the on/off state of the switching element in the inverter (30) based on these input (S15). As described above, in step (S15), the voltage modulation unit (125) generates a carrier signal in a triangular wave form corresponding to the switching frequency (Fsw) (carrier frequency) generated by the adder (67), and can form a pulse width modulation signal in a rectangular wave form by comparing the carrier signal with the d/q-axis voltage command (vdqsreff).

The pulse width modulation signal generated by the voltage modulation section (123) is supplied to the gates of the switching elements (S1-S6) in the inverter (30), and the on/off states of the switching elements (S1-S6) can be controlled.

Since a series of control flows shown in fig. 6 are continuously repeated during the motor driving, the switching frequency can be randomly determined each time such a control flow is repeated.

As described above, the inverter control device and method for driving a motor according to various embodiments of the present invention can prevent generation of a large harmonic component at a specific frequency by randomly changing the switching frequency of the inverter, thereby significantly reducing switching noise and the like.

In particular, the inverter control device and method for driving a motor according to various embodiments of the present invention determine the change width of the switching frequency that affects the controllability by inputting various motor driving information in consideration thereof, and thus can maintain appropriate controllability even in a state where the controllability of the motor is reduced (for example, in a state where a difference between a motor current command and an actual current supplied to the motor is large, or in a state where the temperature of the motor or the inverter is excessively increased).

While the specific embodiments of the present invention have been shown and described, it is needless to say that those skilled in the art can make various improvements and modifications to the present invention without departing from the technical idea of the present invention provided by the scope of the claims.