KR102591400B1 - Method for controlling motor and apparatus using the same - Google Patents

Abstract

An electric motor control method performed by a computing device according to an embodiment,
Receiving an angular velocity command and a voltage command of an electric motor, calculating a first magnetic flux command based on the angular velocity command and the voltage command, calculating a predetermined optimal overmodulation index in response to the value of the first magnetic flux command. A step of calculating a second magnetic flux command based on the optimal overmodulation index, calculating a current operating point based on the second magnetic flux command and a received torque command, and calculating a current operating point based on the current operating point. It may include a step of controlling.

Description

Electric motor control method and device using the same {METHOD FOR CONTROLLING MOTOR AND APPARATUS USING THE SAME}

This disclosure relates to an electric motor control method and a device using the same.

Emission regulations are being strengthened around the world, and the eco-friendly car market is continuously expanding.

In the above situation, the need for a motor control system utilizing a battery-inverter is expanding, and the need for a control algorithm that maximizes the motor drive efficiency of the inverter is increasing.

Permanent magnet synchronous motors used in eco-friendly automobile motors have the advantage of high torque and power density per unit volume. In the case of the efficiency of a permanent magnet synchronous motor, determining the optimal current operating point to reduce copper loss and iron loss and controlling the motor based on the determined operating point may be key.

The characteristic configuration of the present invention for achieving the purpose of the present invention as described above and realizing the characteristic effects of the present invention described later is as follows.

An electric motor control method performed by a computing device according to an embodiment of the present invention includes receiving an angular velocity command and a voltage command of an electric motor; calculating a first magnetic flux command based on the angular velocity command and the voltage command; calculating a predetermined optimal overmodulation index in response to the value of the first magnetic flux command; calculating a second magnetic flux command based on the optimal overmodulation index; calculating a current operating point based on the second magnetic flux command and the received torque command; And it may include controlling the electric motor based on the current operating point.

In calculating the overmodulation index, the overmodulation index may be determined based on an optimal MI (Modulation Index) Table including an optimal overmodulation index corresponding to the torque command and the first magnetic flux command.

In the optimal MI Table, when the magnetic flux command calculated at the current operating point controlled by MI = 1.1547 is greater than or equal to the magnetic flux of the MTPA (Maximum Torque Per Ampere) curve, the optimal overmodulation index is predetermined to be 1.1547, and MI = If the magnetic flux command calculated at the current operating point controlled by 1.2732 is less than or equal to the magnetic flux of MFPT (Minimum Flux Per Torque), the optimal overmodulation index is predetermined to be 1.2732, and MI = current operating point controlled by 1.1547. If the magnetic flux command calculated from is smaller than the magnetic flux of the MTPA (Maximum Torque Per Ampere) curve, or the magnetic flux command calculated from the current operating point controlled by MI = 1.2732 is greater than the magnetic flux of MFPT (Minimum Flux Per Torque), the maximum power The overmodulation index indicating efficiency may be predetermined as the optimal overmodulation index.

The step of calculating the overmodulation index is a step of converting the first magnetic flux command into a third magnetic flux command based on a magnetic flux command correction table including a magnetic flux command measured in advance so that the actual overmodulation index of the motor is calculated to be 1.1547. ; and determining the optimal overmodulation index based on the third magnetic flux command.

The step of controlling the electric motor includes controlling the electric motor based on a first voltage command calculated based on the current operating point, and when the magnitude of the first voltage command exceeds a predetermined threshold, the first voltage command The step of performing compensation may further be included.

A computing device that performs an electric motor control method includes: memory; and a processor, wherein the processor receives an angular velocity command and a voltage command of an electric motor, calculates a first magnetic flux command based on the angular velocity command and the voltage command, and calculates a predetermined value in response to the value of the first magnetic flux command. Calculate an optimal overmodulation index, calculate a second magnetic flux command based on the optimal overmodulation index, calculate a current operating point based on the second magnetic flux command and the received torque command, and calculate the current operating point. The electric motor can be controlled based on .

The following drawings attached for use in explaining embodiments of the present invention are only some of the embodiments of the present invention, and those skilled in the art can use these drawings without making efforts to develop a separate invention. Other drawings may be obtained.
1A is a diagram illustrating an exemplary structure of a permanent magnet synchronous motor.
Figure 1b is a diagram for explaining the mathematical model of a permanent magnet synchronous motor.
FIG. 1C is a diagram showing the result of vectorizing and expressing the physical quantities explained through FIG. 1B.
Figure 2 is a diagram for explaining physical limiting conditions for the operation of a permanent magnet synchronous motor.
Figure 3 is a diagram showing an example of the current operating point moving in the MFPT operating area.
FIG. 4A is a diagram for explaining voltage overmodulation control applied to a motor control method according to an embodiment.
Figure 4b is a diagram for explaining the form of the output phase voltage depending on the size of the command voltage.
Figure 4c is a diagram for explaining the Volognani overmodulation method applied in the motor control method according to one embodiment.
FIG. 4D is a diagram illustrating a method of compensating for nonlinearity in the process of performing overmodulation control in a motor control method according to an embodiment.
FIG. 5 is a diagram illustrating loss trends according to current operating point movement according to one embodiment.
FIG. 6A is a diagram illustrating a method by which a computing device generates a flux-torque current map according to one embodiment.
FIG. 6B is a diagram illustrating an example of the final magnetic flux-torque current map generated through the procedure of FIG. 6A.
Figures 6c and 6d are diagrams exemplarily showing the results of data correction in the process of generating the final magnetic flux-torque current map.
Figure 7 is a diagram illustrating magnetic flux data and torque data according to data correction.
FIG. 8A is a diagram for explaining a method of controlling an electric motor according to an embodiment.
FIG. 8B is a diagram for explaining and comparing the current operating point selection method of the motor control method according to other prior literature and the motor control method according to one embodiment.
FIG. 9 is a diagram illustrating how a computing device determines a current operating point using an optimal MI Table according to an embodiment.
FIG. 10A is a diagram illustrating a method by which a computing device generates an optimal MI Table according to an embodiment.
Figure 10b may be a diagram showing the form of an optimal MI Table applied to an electric motor control method according to an embodiment.
Figure 11a is a diagram showing the results of comparing the efficiency of the present invention applying the optimal MI Table with a case applying another MI.
Figure 11b is a diagram showing the ripple improvement effect of the present invention using the optimal MI Table according to an embodiment.
Figure 12 is a flowchart for explaining an electric motor control method according to an embodiment.
Figure 13 is a conceptual diagram schematically showing the configuration of a computing device according to an embodiment.

The detailed description of the present invention described below refers to the accompanying drawings, which show by way of example specific embodiments in which the present invention may be practiced to make clear the objectives, technical solutions and advantages of the present invention. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention.

And throughout the description and claims of this disclosure, the word 'comprise' and variations thereof are not intended to exclude other technical features, attachments, components or steps. Additionally, 'one' or 'one' is used to mean more than one, and 'another' is limited to at least the second or more.

Other objects, advantages and features of the invention will appear to those skilled in the art, partly from this description and partly from practice of the invention. The examples and drawings below are provided by way of example and are not intended to limit the invention. Accordingly, the details disclosed in this disclosure regarding specific structures or functions should not be construed in a limiting sense, but merely provide guidance for those skilled in the art to variously practice the present invention with any detailed structures that are practically suitable. It should be interpreted as representative basic data.

Moreover, the present invention encompasses all possible combinations of the embodiments presented in this disclosure. It should be understood that the various embodiments of the invention are different from one another but are not necessarily mutually exclusive. For example, specific shapes, structures and characteristics described herein may be implemented in one embodiment without departing from the spirit and scope of the invention. Additionally, it should be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the present invention. Accordingly, the detailed description that follows is not intended to be taken in a limiting sense, and the scope of the invention is limited only by the appended claims, together with all equivalents to what those claims assert, if properly described. Similar reference numbers in the drawings refer to identical or similar functions across various aspects.

In this disclosure, unless otherwise indicated or clearly contradictory to the context, items referred to in the singular include the plural, unless the context otherwise requires. Additionally, in describing the present invention, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present invention, the detailed description will be omitted.

Hereinafter, in order to enable those skilled in the art to easily practice the present invention, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

1A is a diagram illustrating an exemplary structure of a permanent magnet synchronous motor.

Permanent magnet synchronous motors to which the control method of this specification is applied can be divided into SPMSM (Surface Permanent Magnet Synchronous Motor) shown on the left and IPMSM (Interior Permanent Magnet Synchronous Motor) shown on the right, depending on the type of permanent magnets installed. there is.

SPMSM is an electric motor with a permanent magnet attached to the surface of the rotor. Since the inductance size of the phase winding has constant characteristics regardless of the rotor position, it can only generate magnetic torque.

IPMSM is a type of electric motor with a magnet inserted inside the rotor. It generates a salient polarity in which the size of the inductance varies depending on the position of the rotor, so it can utilize reluctance torque in addition to magnetic torque, and has a relatively lower torque compared to SPMSM. can produce large output.

Figure 1b is a diagram for explaining the mathematical model of a permanent magnet synchronous motor.

Figure 1b shows that the rotor has an electrical angular velocity A three-phase permanent magnet motor rotating at an angle from the a-phase winding It may be an equivalent model representing a state of rotation.

According to the above model, the three-phase stator voltage equation of a permanent magnet synchronous motor can be expressed as Equation 1.

represents the armature resistance, is the magnetic flux linked to the three-phase winding, is the voltage of each phase, may mean the current of each phase.

Based on Equation 1, the magnetic flux generated in the armature winding of each phase of SPMSM can be expressed as Equation 2.

is the flux matrix, is the inductance matrix, is the current matrix, is the magnetic flux matrix linked to the stator winding, is the magnitude of magnetizing inductance, is the size of the leakage inductance, can represent the magnitude of magnetic flux linked to the stator winding by the rotor permanent magnet.

In the case of IPMSM, unlike SPMSM, the size of the inductance varies depending on the rotation of the rotor, and the magnetic flux linkage of IPMSM can be expressed as Equation 3.

is the flux matrix, is the inductance matrix, is the current matrix, is the magnetic flux matrix linked to the stator winding, is the average value of magnetizing inductance, is the amplitude of magnetizing inductance that varies depending on the rotor position, is the size of the leakage inductance, can represent the magnitude of magnetic flux linked to the stator winding by the rotor permanent magnet.

For convenience of calculation, when Clark transformation and Park transformation are performed to express the magnetic flux about the D-Q axis, it can be expressed as Equation 4, and the power input to the permanent magnet synchronous motor based on Equation 3 is Equation It can be expressed as 5.

, are D-axis and Q-axis magnetic flux, respectively, is the sum of the magnetic flux of each axis, , are the D-axis inductance, Q-axis inductance, and , are the D-axis current, Q-axis current, and can represent the magnitude of magnetic flux linked to the stator winding.

The mechanical energy output excluding the armature copper loss and magnetic field energy variation among the input power can be replaced by the product of torque and speed, and the torque of IPMSM and SPMSM can be expressed by Equation 6 and Equation 7.

represents the output torque, can represent the number of poles of the electric motor.

FIG. 1C is a diagram showing the result of vectorizing and expressing the physical quantities explained through FIG. 1B.

In Figure 1c , are the D-axis current, Q-axis current, and is the input current, is the magnetic flux of the permanent magnet, , is the D-axis inductance, Q-axis inductance, , is D-axis magnetic flux, Q-axis magnetic flux, is the air gap flux, may be the angular velocity of the rotor.

As can be seen in Figure 1c, the air gap magnetic flux The size of can be determined by combining the D-axis and Q-axis magnetic fluxes.

Rotor angular velocity on each axis flux magnitude A voltage of the magnitude multiplied by must be approved. In addition to the voltage induced by the magnetic flux, the voltage drop component occurs due to copper loss in the armature winding. plus may correspond to the size of the voltage to be output from the final inverter.

The size of the required voltage required to control the motor is the air gap voltage. Since it is determined by the size, weak flux control may be required to adjust the voltage required to drive the motor to the maximum voltage range that can be output from the inverter.

Figure 2 is a diagram for explaining physical limiting conditions for the operation of a permanent magnet synchronous motor.

When following Equation 6 and Equation 7, there may be countless D-Q axis current combinations to obtain a specific size of output torque. However, the controllable current operating area may be flexibly limited depending on the direct current voltage (DC-Link voltage) applied to the inverter and the speed of the motor. Therefore, in order to output a desired target torque within controllable limiting conditions, it is necessary to dynamically move the current operating point according to the driving conditions of the electric motor.

According to one embodiment, the current operating point may be determined by Equation 8.

In Figure 1c , are the D-axis current, Q-axis current, and is the magnetic flux of the permanent magnet, , is the D-axis inductance, Q-axis inductance, , is D-axis magnetic flux, Q-axis magnetic flux, is the magnitude of magnetic flux linked to the stator winding, is the angular velocity of the rotor, is the maximum voltage applied to the motor, and can be determined by the size of the maximum direct current voltage input to the inverter and the inverter PWM switching method.

The voltage limiting condition may take the form of an elliptical (IPMSM) or circular (SPMSM) equation for the D-Q current axis, as shown in FIG. 2. The area where current control is possible when driving the motor may be inside the current limit source or inside the voltage limit source. The current limiting source can be scaled down depending on the thermal rating requirements of the system, but can always be fixed at its maximum size if temperature is not a concern.

In addition, the voltage limiting source may be a combination of DQ axis currents that create an air gap magnetic flux of the same size, and the maximum output voltage may be increased by increasing the angular velocity or decreasing the voltage of the DC power supply. If the size of is reduced, the size of the circle may be reduced.

According to one embodiment, the operating area may be divided into three types depending on the angular speed of the rotor of the electric motor and the size of the direct current power applied to the inverter.

1) Control in the MTPA (Maximum Torque Per Ampere) operating area

When the angular speed of the motor is small and the size of the applied DC power is large and the voltage margin (difference between the voltage applied to the motor and the minimum voltage required for motor operation) is sufficient (MTPA operating area), the current operates within the current limit circle. Points can be selected relatively freely. In this case, in order to minimize copper loss, it may be most appropriate to select the current operating point that can output the highest torque per unit current, and this operating point is referred to as the MTPA (Maximum Torque Per Ampere) operating point. It can be. The MTPA operating point can be determined as the point representing the smallest current magnitude on the constant torque curve, which is a set of current operating points representing constant output torque.

2) Control in constant torque operation area

If the angular speed of the motor increases or the direct current voltage applied to the inverter decreases, the size of the voltage limit source may decrease, thereby reducing the size of the driveable current area. In this case, magnetic flux control must be performed to move the current operating point so that the output voltage of the inverter becomes smaller. More specifically, weak magnetic flux control can be performed to cancel the magnetic flux of the permanent magnet by flowing a negative D-axis current within the same driving conditions. In the process of performing such weak flux control, it is also required to accurately generate the output torque required by the system, so the electric motor is operated so that the current operating point moves along a constant torque curve (a collection of current operating points representing the same output torque). This can be controlled.

3) Control in MFPT (Minimum Flux Per Torque) operating area

The size of the air gap magnetic flux generated by the current operating point on the constant torque curve shows a trend of decreasing and then increasing again as it moves in the negative D-axis direction. The point where the size of the air gap magnetic flux decreases and then increases may be referred to as the MFPT (Minimum Flux Torque) operating point. The MFPT operating point is the point where the voltage limit ellipse and the constant torque curve meet, and may be the minimum magnetic flux operating point on the constant torque curve, and at the same time, the maximum torque operating point on the voltage limit ellipse.

As the angular speed of the motor increases, if the voltage limit ellipse becomes small enough to deviate from the constant torque curve, operating the motor at the MFPT operating point can be a strategy that satisfies the required magnetic flux and generates the largest torque.

Figure 3 is a diagram showing an example of the current operating point moving in the MFPT operating area.

A curve connecting the MFPT operating points of several constant torque curves may be referred to as an MFPT curve.

As the angular speed of the motor increases, if it becomes difficult to drive the motor within the current operating point included in the constant torque curve, the motor may be controlled based on the current operating point within the MFPT curve as shown in (a), As the angular speed of the motor increases, the current operating point may point toward the center of the voltage limiting ellipse.

If the size of the command torque (target output torque of the motor) is large as shown in (b), as the angular speed of the motor increases, the current operating point moves along the current limiting source rather than the MFPT curve, and then the current decreases along the MFPT curve. The operating point can be determined.

Additionally, if the center of the voltage limiting ellipse is outside the current limiting circle, a current operating point that follows the current limiting circle rather than the MFPT curve may be selected.

In the case of SPMSM, since there is no salient polarity in the rotor reluctance, only magnetic torque is generated by the Q-axis current, and the constant torque curve can be given in a form parallel to the Q-axis as shown in (c). It will be understood by those skilled in the art that the current operating point may move in the following direction.

FIG. 4A is a diagram for explaining voltage overmodulation control applied to a motor control method according to an embodiment.

In order to control the current flowing in the armature winding using an inverter, it is necessary to instantaneously adjust the magnitude of the voltage. In general, the PWM (Pulse Width Modulation) voltage switching method is used to output a voltage of the desired size on average. In this case, the range of amplitude that can linearly output the sinusoidal command voltage is half of the amplitude of the DC power supply. doing may be limited to The size of the voltage command is If it exceeds , nonlinearity occurs between the command voltage and the output voltage, and the area where nonlinearity occurs may be referred to as an overmodulation area.

In order to obtain the desired voltage output in the over-modulation region, harmonics must be appropriately included in the voltage command to maintain the maximum magnitude of the command voltage within the limiting conditions and the magnitude of the effective voltage applied between the motor coil lines must be increased. This control technique requires over-modulation. It may be referred to as modulation control. The degree to which overmodulation control is performed can be expressed as the overmodulation index MI expressed in Equation 9 below.

MI is the overmodulation index; is the phase voltage applied to the motor, may mean a direct current voltage applied to the inverter.

When voltage is applied to the inverter at the maximum output size, the size of the largest phase-inversion fundamental wave is , and the modulation index at this time may be MI = 1.2732.

Since the phase of each winding of a three-phase motor has a phase difference of 120 degrees, the three-phase voltage output also needs to be output with a phase difference of 120 degrees.

As shown in Figure 4a, is the phase voltage of the motor, It can be expressed based on a combination of three-phase voltage vectors. The corresponding voltage may be a vector that can rotate in synchronization with the angular velocity of the field flux generated from the rotor.

Phase-to-phase voltage that can be maximally output from the motor The size of may be limited to the inside of the hexagon shown in the drawing. Depending on the phase of , the maximum amount of voltage that can be output can vary flexibly. The electric motor is inscribed in a hexagon. Up to , the command voltage can be output as is regardless of the phase, but for command voltages larger than that, the output may be limited depending on the phase.

Figure 4b is a diagram for explaining the form of the output phase voltage depending on the size of the command voltage.

Referring to FIG. 4b, for the command voltage corresponding to Part [A], the voltage command may be output as is.

The command voltage corresponding to Part [B] (the command voltage is In the case of (exceeding), the motor cannot generate a phase voltage output with a sinusoidal pole voltage. In this case, a symmetric spatial voltage modulation method may be applied, and in this case, as shown in the figure, the instantaneous maximum magnitude of the phase voltage is Voltage can be controlled so as not to exceed Linear output may be possible up to .

The command voltage corresponding to Part [C] (the command voltage is exceeds) Despite the modulation of the polar voltage command, nonlinearity between the command voltage and the output voltage occurs.

In the motor control method according to one embodiment, the Volognani overmodulation technique can be applied in the above area, and the Volognani overmodulation method is described in Non-Patent Document 1: [Silverio Bolognani, "Novel Digital Continuous Control of SVM Inverters in the Overmodulation Range", IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, 1997, VOL. 33, NO. A person skilled in the art can easily understand through the disclosure of [2].

Regarding the Part [D] area, the maximum voltage that can be output from the inverter is may be limited to Therefore, even if a voltage command higher than the maximum voltage is generated through the control algorithm, this corresponds to a voltage that cannot be actually generated, so the phase of the voltage command is maintained while the size is reduced. There is a need to limit it to . The waveform shown in FIG. 4b may be the result of the voltage command being modulated through the Volognani overmodulation method. As above, the control that outputs the maximum voltage of the motor can be referred to as 6-Step driving, and the size of the fundamental wave voltage of the output phase voltage is It is calculated as , which may be the maximum voltage value that can be physically generated by the inverter.

Figure 4c is a diagram for explaining the Volognani overmodulation method applied in the motor control method according to one embodiment.

Referring to FIG. 4c, the phase voltage corresponding to the Part [C] area described in the previous drawing can be modulated into the voltage inside the hexagon through Equation 10 below.

is the phase voltage modulated through Volognani overmodulation, Is The phase angle of is the magnitude of the direct current voltage applied to the inverter, can represent the phase voltage applied to the motor.

The output voltage and voltage waveform generated according to the overmodulation index may be as shown in the table shown at the bottom of FIG. 4C. In the case of 6-step driving, the overmodulation index MI = 1.3333 is given, but at this time, excluding harmonic components, the magnitude of the voltage effectively applied to the actual motor can be calculated as MI = 1.2732.

FIG. 4D is a diagram illustrating a method of compensating for nonlinearity in the process of performing overmodulation control in a motor control method according to an embodiment.

The computing device according to one embodiment may change the size of the voltage command in the process of performing the motor control method. By modulating the voltage, the magnitude of the voltage command and output voltage can be output to be the same. but, In the case of a larger voltage command, in the process of overmodulation, odd-order harmonics corresponding to 6n+(-)1dp other than the third harmonic are included, which may distort the phase current. Phase current distortion may be a factor that causes vibration within the motor and may not be an effective voltage component that generates the torque of the motor. Since the magnitude of the fundamental wave component of the voltage command given as a sine wave and the polar voltage actually output by overmodulating it are different from each other, nonlinear output characteristics may be as shown in FIG. 4D. More specifically, the phase-to-phase voltage output waveform generated by overmodulation may include many harmonics, and the voltage command may be When input as , the size of the phase voltage fundamental wave applied to the motor is can be reduced. Accordingly, the computing device can prevent performance degradation by compensating the magnitude of the voltage and applying it to the motor so that the fundamental wave component of the output voltage is the same as the voltage command.

FIG. 5 is a diagram illustrating loss trends according to current operating point movement according to one embodiment.

The power loss of a permanent magnet synchronous motor can be divided into no-load loss and load loss. Load loss can include copper loss and stray load loss, and no-load loss can include mechanical loss and iron loss (hysteresis loss, eddy current loss). there is.

Among the above losses, the most important loss factors that affect the efficiency of electric motors include copper loss and iron loss. Copper loss is energy loss due to heat that occurs when current flows through the motor armature coil and can be proportional to the square of the current. Core loss is a loss that occurs when the direction of magnetic flux linking the core of the stator and rotor changes when an electric motor is driven, and may include eddy current loss and hysteresis loss. In the case of iron loss, studies have been conducted to approximate iron loss using various parameters, but it can be very difficult to accurately model iron loss mathematically. In addition, the occurrence of core loss may increase due to harmonic currents included during voltage overmodulation for maximum efficiency control, and it may be very difficult to express mathematically the effect of high-frequency harmonics on core loss.

Referring to FIG. 5, when the current operating point moves in the direction of the MFPT curve on the constant torque curve, the magnitude of copper loss increases as the magnitude of the current increases, but the magnitude of iron loss may decrease as the magnitude of magnetic flux decreases. Conversely, when the current operating point moves in the right MTPA curve direction, the magnitude of the current decreases and the copper loss decreases, but the magnitude of the magnetic flux increases and the magnitude of the iron loss may increase. As such, the two loss components that have the greatest impact on the efficiency of the motor are inversely proportional to each other, so the current operating point needs to be appropriately selected to minimize the integrated loss.

Since voltage overmodulation control is applied to the motor control method according to one embodiment, losses due to changes in overmodulation index (MI) need to be taken into consideration. When the overmodulation index increases, the current applied to the motor decreases and the magnetic flux generated within the motor increases, which may reduce copper loss and increase iron loss. Conversely, when the overmodulation index decreases, the current applied to the motor increases and the magnetic flux generated within the motor decreases, resulting in increased copper loss and decreased iron loss.

The motor control method according to one embodiment can provide a solution to modeling difficulties by determining the current operating point that minimizes loss through a look-up table based on actually measured efficiency.

FIG. 6A is a diagram illustrating a method by which a computing device generates a flux-torque current map according to one embodiment.

According to one embodiment, a computing device may utilize a flux-torque current map to determine a current operating point for motor control. The magnetic flux-torque current map may be data that maps the current operating point (D-axis current and Q-axis current) that causes the motor to be driven with the target magnetic flux-torque (magnetic flux-torque command) with the corresponding magnetic flux-torque.

The magnetic flux-torque current map can be determined by measuring the torque and air gap magnetic flux generated according to the D-Q axis current combination through testing. More specifically, the computing device connects a permanent magnet synchronous motor to a dynamo device (test device) to fix the driving speed, then changes the magnitude/phase of the current and measures magnetic flux (air gap flux) and torque data to determine individual current operation. Magnetic flux and torque data for each point can be obtained. In the process of acquiring magnetic flux and torque data, it is necessary to maintain the driving speed of the dynamo at a certain level. More specifically, the computing device can drive the dynamo at a speed lower than the base RPM at which the dynamo can maintain maximum torque. This means that if the test is performed at a speed higher than the base RPM, current control is not possible due to insufficient voltage margin at the current operating point where the air gap magnetic flux is high, and at a speed that is too low, the inverter output voltage becomes too small and the calculation data of the air gap magnetic flux becomes inaccurate. It may be because of losing.

The computing device performs PI current control using D-Q axis current commands and can obtain magnetic flux/torque data by averaging data for several seconds obtained after reaching a steady state. As the PI current control results are used, the results may fluctuate at a rapid cycle, and errors may occur in the measurement results due to the gain value of the current controller, sensor error, etc., which can generate a distorted magnetic flux-torque current map. there is. The computing device can generate a smoother flux-torque current map by applying a polynomial regression equation to the distorted flux-torque current map (applied independently for flux and torque), and the corrected flux-torque current map. An example of is as shown in Figure 7.

In addition, the computing device can generate a magnetic flux-torque current map with improved resolution that reflects even data for which no actual experiment was performed through interpolation of air gap magnetic flux and torque data.

The computing device according to one embodiment may obtain the following elements by utilizing the magnetic flux-torque current map described above in order to perform the process of determining the current operating point according to the magnetic flux-torque shown in FIG. 6A.

i) constant torque curve, which is a set of current operating points that produce the same torque;

ii) MTPA (Maximum Torque Per Ampere) curve (curve connecting the closest points from the origin to each constant torque curve): A set of current operating points with the lowest current consumption to produce the same torque, or a current representing the same current size. A set of current operating points that generate the greatest torque among the operating points.

iii) MFPT (Minimum Flux Per Torque) curve (a set of current operating points with the minimum magnetic flux size within a constant torque curve)

Due to the previous process of improving resolution, data may tend to oscillate in the process of deriving the MFPT curve. When the size of the DC power source is small and the speed is very high, so that the air gap flux must be maintained smaller than the MFPT operating point, the current operating point is selected along the MFPT curve, and the oscillating tendency described above can interfere with obtaining desirable results. . The computing device can derive a smoother MFPT curve through multiple regression analysis using Equation 11. More specifically, a corrected MFPT curve can be derived by deriving ai by setting the D-Q axis current as input to output the square of the resultant magnetic flux.

is the air gap flux, is the D-axis current, is the Q-axis current, and ai can represent an arbitrary coefficient.

Referring to FIG. 6A, the computing device may receive data for the flux-torque current map with the improved correction and resolution described above in step 610. The computing device provides a torque command through step 620. , and through step 630 A constant torque curve corresponding to can be derived (in this process, the computing device can perform linear interpolation on the constant torque curve.). A constant torque curve can be derived by connecting the current operating points that produce the same torque as previously described.

The computing device may derive the MTPA point (MTPA operating point) and the MFPT point (MFPT operating point) through step 640 (depending on the embodiment) MTPA points and MFPT points corresponding to can be derived.). A person skilled in the art can easily understand that the MTPA point and the MFPT point can be derived as individual points based on the method of deriving the MTPA curve and MFPT curve described above.

The computing device commands the magnetic flux through step 650. Set the magnetic flux command in step 660 Magnetic flux at this MFPA operating point You can decide whether it is smaller than or not. At step 660 this If it is determined to be greater than or equal to Magnetic flux at this MTPA operating point You can determine whether it is greater than or equal to. The computing device at step 670 this If smaller, step 671 may search for the current operating point within the constant torque curve (a constant torque curve with linear interpolation, depending on the embodiment). The computing device determines the discovered current operating point. and It can be included in the final flux-torque current map by corresponding to .

The computing device is a magnetic flux command This MTPA operating point flux greater than or equal to the MFPT operating point flux If it is smaller, the current operating point can be searched by limiting the current condition to a predetermined range.

More specifically, at step 670 this If determined to be greater than or equal to, the computing device may set the MTPA point as the current operating point through step 672 and include it in the final flux-torque current map. This is because the operating point that generates a larger magnetic flux than the MTPA operating point has a large current and thus reduces efficiency.

At step 660 this If determined to be less than, the computing device directs the magnetic flux command through step 680. You can decide whether this is 0 or not.

At step 680 If it is determined to be non-zero, the computing device searches for a current operating point within the MFPT curve (which may be a linearly interpolated curve, depending on the embodiment) through step 681, and selects the searched current operating point as and It can be included in the final flux-torque current map by corresponding to . This is because a magnetic flux command smaller than the MFPT operating point corresponds to a magnetic flux command that cannot maintain torque due to insufficient voltage. Therefore, the computing device can select the operating point that generates the largest torque among the operating points that can drive the electric motor by selecting the operating point that satisfies the magnetic flux command within the MFPT curve.

At step 680 If is determined to be 0, the computing device proceeds through step 682 to determine the D-axis current operating point. and Q-axis current operating point cast ( is the magnitude of the magnetic flux linked to the stator winding by the rotor permanent magnets, can be set to the D-axis inductance and included as the current operating point of the final magnetic flux torque current map.

FIG. 6B is a diagram illustrating an example of the final magnetic flux-torque current map generated through the procedure of FIG. 6A. The final magnetic flux-torque current map includes the D-axis current operating point and Q-axis current operating point corresponding to the magnetic flux command and torque, and the computing device utilizes the final magnetic flux-torque current map to respond to the magnetic flux command and torque command. The current operating point can be calculated.

Figures 6c and 6d are diagrams exemplarily showing the results of data correction in the process of generating the final magnetic flux-torque current map.

Referring to Figure 6c, it can be seen that data vibration is reduced through data correction. When the motor was allowed to operate on the MFPT curve at a speed above a predetermined threshold and a voltage below a predetermined threshold, and then the same load change was input, it was confirmed that the current command fluctuated very significantly despite the same load change before compensation. In the case of the corrected current map, it can be seen that the change is not large.

As previously described, the computing device can reduce vibration in the data by performing data correction using multiple/polynomial regression in the process of generating the final flux-torque current map.

Referring to FIG. 6d, which shows the variation of the D-Q axis current shown in FIG. 6c over time, when using an uncorrected current map, the D-axis current is controlled to fluctuate up to tens of A, but when using a corrected current map, the D-axis current is controlled to fluctuate up to tens of A. In this case, it is confirmed that only the required amount of current changes depending on the size of the load.

Additionally, referring to the right side diagram of FIG. 6D showing the change in speed according to load over time, when an uncorrected current map is used, the speed waveform is distorted and fluctuates relatively significantly compared to the change in load torque. This may mean that the magnitude of the torque generated when the current operating point moves within the uncorrected MFPT curve exhibits non-linear characteristics. In contrast, when the corrected current map is applied, it can be seen that the waveform of the load torque and the speed change exhibit linear characteristics.

FIG. 8A is a diagram for explaining a method of controlling an electric motor according to an embodiment.

Referring to FIG. 8A, the driving area can be divided into three areas depending on the angular speed of the electric motor rotor.

Part [A], the low-speed area, is a case where the rotor angular speed of the motor is low below Base RPM and the magnitude of the DC voltage applied to the inverter is sufficiently high, and the voltage margin (maximum phase voltage that can be output from the inverter and the voltage induced in the armature coil) is high enough. Because the magnitude difference in back EMF is high, the computing device can control the motor by selecting the MTPA current operating point that produces the maximum torque per unit current. In this case, copper loss can be minimized because the current operating point with the smallest amount of current compared to torque is selected. For Part[A], the overmodulation index is It may be an area where voltage can be output without generating harmonics by setting it to .

In the case of Part[B], where the speed increases beyond Part[A] and the voltage margin becomes insufficient, the optimal current operating point must be selected to secure the voltage margin. To this end, the computing device needs to determine the current operating point at which the integrated loss of the system is minimized by appropriately combining flux weakening control and overmodulation control. Computing devices are The voltage modulation index MI is changed based on the operating point, and the current operating point can be determined by using the optimal MI Table, which databases the voltage modulation index driven at the highest efficiency through the measured efficiency. The motor angular speed condition in Part[B] may be the maximum speed range that can increase speed while maintaining a constant torque. Since the output power calculated as the product of torque and angular velocity always remains the same, by only paying attention to the change in input power due to the change in loss component, the overmodulation index that achieves the highest efficiency and the corresponding current operating point can be determined. In other words, in a situation where the output power remains the same, the optimal MI Table can be created by tabulating the overmodulation index that minimizes the size of the input power. If the angular speed of the motor becomes high enough to deviate from the constant torque curve, additional discussion may be necessary because not only the input power but also the output power itself becomes a variable area. The specific method by which the computing device controls the electric motor using the optimal MI Table in the Part [B] area is explained in more detail through the accompanying drawings.

In the case of Part[C], a high-speed region where the torque magnitude cannot be maintained and the torque magnitude must be reduced, the computing device sets the overmodulation index to the maximum value. The electric motor can be driven by . This may be because the maximum torque and speed range that the motor can output is expanded. On the MFPT curve expressed in green, as the operating point of the current moves downward, the magnitude of the magnetic flux decreases, making it possible to secure voltage margin, but the magnitude of torque also decreases. The computing device sets the voltage modulation index to the maximum value in the high-speed region where the motor operates above the MFPT curve. You can control the motor by setting it to . Through this, the computing device can secure a voltage margin and move the position of the current operating point upward, thereby securing a larger maximum torque that can be output and maximizing efficiency. This is because the rate of increase in output power due to an increase in generated torque is greater than the increase in input power due to an increase in core loss by setting the voltage modulation index to the maximum.

FIG. 8B is a diagram for explaining and comparing the current operating point selection method of the motor control method according to other prior literature and the motor control method according to one embodiment.

The driving angular speed of the electric motor is And the direct current voltage (DC-Link voltage) is In the case given, the voltage limit ellipse for which overmodulation control is not performed may appear as 'B'. In the case of a classical control method that does not perform overmodulation control and only considers copper loss, the motor can be driven at the 'b' current operating point, which is the intersection of the constant torque curve and the voltage limit ellipse. LMC method that considers iron loss within the range of not performing overmodulation control (Non-patent Document 2: [S. Morimoto, "Loss Minimization Control of Permanent Magnet Synchronous Motor Drives", IEEE Transactions on Industrial Electronics, Oct 1994, Volume 41 , Issue 5] and SC method (Non-patent Document 3: [S. Vaez, VI John, and MA Rahman, "An on-line loss minimization controller for interior permanent magnet motor drives", IEEE Transactions on Energy Conversion, In the case of [Vol. 14, No. 4, December 1999]), it is driven at point 'a' to reduce the size of the integrated loss, and at this time, the efficiency can be improved by about 0.2 to 0.7% compared to the method that only considers copper loss. .

When performing overmodulation control under angular velocity conditions, the current operating area can be expanded up to the size of ellipse 'A'. In this case, in the case of the 6-Step motor method that unconditionally maximizes the voltage utilization rate (overmodulation index), the motor can be driven at the 'd' current operating point. In the case of the 'd' current operating point, it is the operating point where the copper loss of the motor is the smallest, and compared to the 'b' current operating point, efficiency can be improved to a maximum of 1.7%.

In the motor control method according to one embodiment, the computing device determines the current operating point using the optimal MI Table, thereby controlling the motor to drive at the 'c' current operating point where the integrated loss is the smallest in the overmodulation control area. . The efficiency of a motor driven at the 'c' operating point is improved by an additional 0.3% compared to the 'd' operating point, and an efficiency improvement of up to 2% compared to the 'b' operating point can be expected.

The angular speed of the motor is In the case where overmodulation control is not performed, the size of the voltage limit ellipse can be given by the 'D' ellipse, and since the current operating point above the constant torque curve cannot be selected, the maximum torque that can be generated above the MFPT curve is The output power can be maximized by generating When the angular velocity of the motor increases, the computing device may perform overmodulation control to expand the size of the current limit ellipse to the size of 'C' and cause the motor to be driven at the 'f' current operating point. In this case, the maximum torque that can be generated can be expanded by 27% compared to the existing 'e' operating point. The 'f' operating point is a current operating point that maximizes the output of the motor in the corresponding area, and may also be a current operating point that maximizes driving efficiency.

In conclusion, the computing device according to one embodiment can achieve maximum efficiency under the same angular velocity, torque, and direct current voltage conditions by utilizing the optimal MI Table in the constant torque curve area, and current operation according to the maximum modulation index in the MFPT curve area. By selecting a point, the same output as the 6-Step method can be displayed, and by operating at the MTPA driving point in the low speed range, the motor can be controlled with high efficiency throughout the angular speed range.

FIG. 9 is a diagram illustrating how a computing device determines a current operating point using an optimal MI Table according to an embodiment.

The computing device can actively maintain the optimal overmodulation index through MI feedback control, marked in red, and enable the motor to generate optimal efficiency. The control method of FIG. 9 may be a case where the electric motor is driven in an angular speed range corresponding to a constant torque curve area as described above.

The computing device provides a first magnetic flux command using Equation 12 through input of the voltage command and the angular velocity command. can be calculated. voltage command can refer to the size of the phase-to-phase voltage to be applied to the motor, and the angular speed command may mean the size of the angular speed at which the electric motor is driven.

Additionally, the computing device is currently and speed command Torque command through PI control with as input can be calculated.

The computing device uses the magnetic flux command correction table (910) to By correcting the actual air gap magnetic flux The second magnetic flux command is a corrected magnetic flux command that calculates the current operating point. can be calculated. Due to error factors that appear in the process of generating the final flux-torque current map described above, the air gap flux of the motor Since it may not be output, the computing device sends the first magnetic flux command through the magnetic flux command correction table 910. The second magnetic flux command It can be corrected. The magnetic flux command correction table 910 is a given direct current voltage ( ) and angular velocity ( ), the actual air gap magnetic flux is from Magnetic flux command to be output as (MI to be 1.1547) may have been tabled in advance through experimentation.

The computing device provides a second magnetic flux command and the third magnetic flux command calculated using the optimal MI Table (920) By adding up the fourth magnetic flux command can be calculated. Third magnetic flux command is a correction value to ensure that the motor is controlled with MI that allows the motor to exhibit maximum efficiency, and is the fourth magnetic flux command through Equation 13. This can be calculated.

More specifically, the computing device utilizes the optimal MI Table 920 to determine the given current voltage ( ) and angular velocity ( ) MI command indicating maximum efficiency at can be calculated. The computing device determines the MI feedback value from the DQ axis voltage output as a result of current control through Equation 14. Calculate and Third magnetic flux command by performing MI PI control to match each other can be calculated.

is the D-axis voltage currently output according to current control, may mean the currently output Q-axis voltage according to current control.

Computing device is the fourth magnetic flux command and torque command Command the current by inputting the current into the D-axis current LookUp Table (931) and the Q-axis current LookUp Table (932). and can be calculated. The D-axis current LookUp Table 931 and the Q-axis current LookUp Table 932 may be a table of the final flux-torque current map described above with respect to the D-axis current operating point and the Q-axis current operating point, respectively. Each current command and is the fourth magnetic flux command and torque command It may correspond to the current operating point that causes the motor to be driven. If the magnetic flux command input to the D-axis current LookUp Table (931) and the Q-axis current LookUp Table (932) increases, a current command that generates a larger air gap magnetic flux will be generated, and the magnitude of the voltage applied to the motor will also increase. Accordingly, the current operating point moves in the direction in which the overmodulation index also increases, and the operation of the motor can be controlled correspondingly. When the magnetic flux command decreases, the operation of the motor can be controlled in the direction in which the overmodulation index decreases.

The computing device is a current command , and current current , The first voltage command is provided through the current PI controller (934, 935) with input. , can be calculated. Current PI controllers (934, 935) control the current current , current command , You can actively track the required voltage until it reaches the size of . More specifically, the current is commanded in the direction in which the air gap magnetic flux increases. , When input, the current operating point moves and the back electromotive force increases, and the current PI controllers (934, 935) provide a current command. , In order to achieve, the first voltage command , The size can be increased. At this time, if the back electromotive force becomes large enough to provide insufficient voltage, the computing device may perform overmodulation control to secure the voltage margin. Conversely, the current command is directed in the direction where the air gap magnetic flux decreases. , When this is input, the current PI controllers (934, 935) provide the first voltage command. , By reducing the size of , the overmodulation index decreases.

The computing device provides a first voltage command , 3-phase voltage through overmodulation for , , generates, and the generated three-phase voltage , , can be applied to the motor. 1st voltage command , The size of the combined voltage command go If it exceeds, the computing device provides the first voltage command through the non-linear voltage command compensation table 940. , Second voltage command by compensating for the size of , can be created. As previously explained in Figure 4d, When overmodulating a voltage command that exceeds the size of Because it becomes smaller. Accordingly, the computing device provides a second voltage command for the modulation region in which the overmodulation index exceeds 1.1547. , You can perform the process of creating .

FIG. 10A is a diagram illustrating a method by which a computing device generates an optimal MI Table according to an embodiment.

Referring to FIG. 10A, the computing device can calculate a current operating point representing maximum efficiency by controlling the overmodulation index MI under specific angular velocity, direct current voltage, and output torque conditions. More specifically, the computing device changes the output torque, battery voltage, and angular velocity, and changes the overmodulation index MI based on the overmodulation index MI = 1.1547, and determines the overmodulation index representing the highest efficiency (output power/input power). It can be converted into a table. In the case of FIG. 10A, MI = 1.1547 is indicated by a circle, and the overmodulation index indicating the highest efficiency may be indicated above each circle.

It is best to measure the optimal overmodulation index for all operating points, but this is a task that requires a lot of time and effort. The optimal MI table is created by expanding the data through interpolation or extrapolation based on the optimal MI value measured for a specific point. You can also write, as shown at the bottom of FIG. 10A.

Figure 10b may be a diagram showing the form of an optimal MI Table applied to an electric motor control method according to an embodiment.

When the computing device calculates the air gap magnetic flux based on the current operating point (magnitude of different DC voltages, angular velocity, torque) when controlled at MI = 1.1547, the current operating point where the magnetic flux is greater than or equal to the MTPA curve is the optimal MI. is determined to be 1.1547, and when the air gap magnetic flux is calculated based on the current operating point when controlled at MI = 1.2732, the optimal MI is determined as 1.2732 for the current operating point where the magnetic flux is less than or equal to the MFPT operating point, and the At the current operating point, the MI representing the maximum power efficiency can be implemented to be selected as the optimal MI. More specifically, the computing device is configured such that the magnetic flux command calculated at the current operating point controlled by MI = 1.1547 is smaller than the magnetic flux of the MTPA curve, or the magnetic flux command calculated at the current operating point controlled by MI = 1.2732 is greater than the magnetic flux of MFPT. In this case, the overmodulation index indicating maximum power efficiency may be predetermined as the optimal overmodulation index.

Figure 11a is a diagram showing the results of comparing the efficiency of the present invention applying the optimal MI Table with a case applying another MI.

Referring to the drawing, compared to controlling with MI = 1.1547, when controlling with optimal MI, there was an efficiency improvement of about 2%, and compared to controlling with MI = 1.2732, an efficiency improvement of 0.3% was achieved. can confirm.

Figure 11b is a diagram showing the ripple improvement effect of the present invention using the optimal MI Table according to an embodiment.

Referring to Figure 11b, it can be seen that the present invention, which uses optimal MI in the case controlled through MI = 1.2732 where harmonics other than the fundamental wave are added, has a ripple improvement effect of more than 10%.

Referring to the table below, it can be seen that under various torque and DC voltage conditions, areas with small currents have a ripple improvement effect of up to 20 to 30%, and areas with large currents have a ripple improvement effect of up to 10 to 15%. there is.

Figure 12 is a flowchart for explaining an electric motor control method according to an embodiment.

Referring to FIG. 12, in step 1210, the computing device may receive an angular velocity command and a voltage command of the electric motor.

In step 1220, the computing device may calculate a first magnetic flux command based on the angular velocity command and the voltage command, and calculate a predetermined optimal overmodulation index in response to the value of the first magnetic flux command. The computing device may determine the overmodulation index based on an optimal MI (Modulation Index) Table including the optimal overmodulation index corresponding to the torque command and the first magnetic flux command. The method of determining the overmodulation index may be the same as described above with reference to FIG. 9. In the optimal MI Table, if the magnetic flux command calculated at the current operating point controlled by MI = 1.1547 is greater than or equal to the magnetic flux of the MTPA (Maximum Torque Per Ampere) curve, the optimal overmodulation index is predetermined to be 1.1547, and MI = 1.2732. If the magnetic flux command calculated at the current operating point controlled by is less than or equal to the magnetic flux of MFPT (Minimum Flux Per Torque), the optimal overmodulation index is predetermined to be 1.2732 and calculated at the current operating point controlled by MI = 1.1547. If the calculated magnetic flux command is smaller than the magnetic flux of the MTPA (Maximum Torque Per Ampere) curve, or the magnetic flux command calculated at the current operating point controlled by MI = 1.2732 is larger than the magnetic flux of MFPT (Minimum Flux Per Torque), the maximum power efficiency is The indicated overmodulation index may be predetermined as the optimal overmodulation index. The method of calculating the optimal MI Table is as described above in FIGS. 10A and 10B.

The computing device converts the first magnetic flux command into a third magnetic flux command based on a magnetic flux command correction table including a magnetic flux command measured in advance so that the actual overmodulation index of the electric motor is calculated to be 1.1547, and based on the third magnetic flux command Thus, the optimal overmodulation index can be determined. The method of converting the third magnetic flux command is the same as described above in the method of using the magnetic flux command correction table of FIG. 9.

Through step 1230, the computing device may calculate a second magnetic flux command based on the optimal overmodulation index and calculate a current operating point based on the second magnetic flux command and the received torque command.

The computing device may control the electric motor based on the current operating point through step 1240. The computing device may control the motor based on a first voltage command calculated based on the current operating point, and perform compensation for the first voltage command when the magnitude of the first voltage command exceeds a predetermined threshold. there is. The method of performing compensation for the first voltage command may be the same as the method described above with reference to FIGS. 4D and 9.

Figure 13 is a conceptual diagram schematically showing the configuration of a computing device according to an embodiment.

The computing device 1300 according to one embodiment may include a communication interface 1330, a processor 1320, and a memory 1310 that communicate with an external entity.

The communication interface 1330 may operate under the control of the processor 1320. The communication interface 1330 may transmit signals through wired communication or wireless communication according to instructions from the processor 1320. The communication interface 1330 can communicate with an external device through wireless or wired communication. The communication interface 1330 is capable of sending and receiving requests and responses to and from other computing devices that are linked to it. As an example, such requests and responses may be made through the same transmission control protocol (TCP) session, but are not limited to this. However, for example, it may be transmitted and received as a UDP (user datagram protocol) datagram.

The processor 1320 may execute program commands stored in the memory 1310. The processor 1320 may refer to a dedicated processor, such as a central processing unit (CPU), on which methods according to the present invention are performed. Memory 1310 may be comprised of volatile and/or non-volatile storage media. For example, the memory 1310 may be comprised of read only memory (ROM) and/or random access memory (RAM). Additionally, the processor 1320 may include hardware components such as a micro processing unit (MPU), central processing unit (CPU), or tensor processing unit (TPU), cache memory, and data bus. . In addition, it may further include an operating system and software configuration of an application that performs a specific purpose.

The processor 1320 may control a series of operations of the computing device 1300 described above.

The configuration of the computing device 1300 described with reference to FIG. 13 is merely illustrative, and the embodiment is not limited thereto. For example, the computing device 1300 may further include other configurations in addition to those shown in FIG. 13 . For example, the computing device 1300 may further include an input interface unit, an output interface unit, etc.

Based on the description of the above embodiments, those skilled in the art will understand that the method and/or processes of the present invention, and the steps thereof, can be realized with hardware, software, or any combination of hardware and software suitable for a specific application. The point can be clearly understood. The hardware may include general-purpose computers and/or dedicated computing devices or specific computing devices or special features or components of specific computing devices. The processes may be realized by one or more microprocessors, microcontrollers, embedded microcontrollers, programmable digital signal processors, or other programmable devices, with internal and/or external memory. Additionally, or alternatively, the processes may be configured as an application specific integrated circuit (ASIC), programmable gate array, programmable array logic (PAL), or to process electronic signals. It can be implemented with any other device or combination of devices. Furthermore, the subject matter of the technical solution of the present invention or the parts contributing to the prior art may be implemented in the form of program instructions that can be executed through various computer components and recorded on a machine-readable recording medium. The machine-readable recording medium may include program instructions, data files, data structures, etc., singly or in combination. Program instructions recorded on the machine-readable recording medium may be specially designed and configured for the present invention or may be known and usable by those skilled in the computer software field. Examples of machine-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical recording media such as CD-ROMs, DVDs, and Blu-rays, and magneto-optical media such as floptical disks. (magneto-optical media), and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, etc. Examples of program instructions include storing and compiling or interpreting them for execution on any one of the foregoing devices, as well as a heterogeneous combination of processors, processor architectures, or combinations of different hardware and software, or any other machine capable of executing the program instructions. machine code, which may be created using a structured programming language such as C, an object-oriented programming language such as C++, or a high- or low-level programming language (assembly language, hardware description languages, and database programming languages and techniques); This includes not only bytecode but also high-level language code that can be executed by a computer using an interpreter.

Accordingly, in one aspect according to the present disclosure, when the above-described methods and combinations thereof are performed by one or more computing devices, the methods and combinations of methods may be implemented as executable code that performs the respective steps. In another aspect, the method may be practiced as systems that perform the steps, the methods may be distributed in several ways across devices, or all functions may be integrated into one dedicated, standalone device or other hardware. In another aspect, the means for performing steps associated with the processes described above may include any of the hardware and/or software described above. All such sequential combinations and combinations are intended to be within the scope of this disclosure.

For example, the hardware device may be configured to operate as one or more software modules to perform processing according to the present disclosure, and vice versa. The hardware device may include a processor such as an MPU, CPU, GPU, or TPU coupled with a memory such as ROM/RAM for storing program instructions and configured to execute instructions stored in the memory, and external devices and signals. It may include a communication unit capable of sending and receiving. In addition, the hardware device may include a keyboard, mouse, and other external input devices to receive commands written by developers.

In the above, the present invention has been described with specific details such as specific components and limited embodiments and drawings, but this is only provided to facilitate a more general understanding of the present invention, and the present invention is not limited to the above embodiments. Anyone skilled in the art to which the present invention pertains can make various modifications and variations from this description.

Accordingly, the spirit of the present invention should not be limited to the above-described embodiments, and the scope of the patent claims described below as well as all modifications equivalent to or equivalent to the scope of the claims fall within the scope of the spirit of the present invention. They will say they do it.

Such equivalent or equivalent modifications will include, for example, logically equivalent methods that can produce the same results as performing the method according to the present disclosure, and the spirit of the present invention and The scope should not be limited by the foregoing examples, but should be understood in the broadest sense permissible by law.

Claims (10)

In an electric motor control method performed by a computing device,
Receiving an angular velocity command and a voltage command of an electric motor;
calculating a first magnetic flux command based on the angular velocity command and the voltage command;
calculating a predetermined optimal overmodulation index in response to the value of the first magnetic flux command;
calculating a second magnetic flux command based on the optimal overmodulation index;
calculating a current operating point based on the second magnetic flux command and the received torque command; and
Controlling the electric motor based on the current operating point
Including,
The step of calculating the overmodulation index is,
Determining the overmodulation index based on an optimal MI (Modulation Index) Table including an optimal overmodulation index corresponding to the torque command and the first magnetic flux command,
In the above optimal MI Table,
If the magnetic flux command calculated at the current operating point controlled by MI = 1.1547 is greater than or equal to the magnetic flux of the MTPA (Maximum Torque Per Ampere) curve, the optimal overmodulation index is predetermined to be 1.1547, and the current controlled by MI = 1.2732. If the magnetic flux command calculated at the operating point is less than or equal to the magnetic flux of MFPT (Minimum Flux Per Torque), the optimal overmodulation index is predetermined to be 1.2732,
The magnetic flux command calculated at the current operating point controlled by MI = 1.1547 is smaller than the magnetic flux of the MTPA (Maximum Torque Per Ampere) curve, or the magnetic flux command calculated at the current operating point controlled by MI = 1.2732 is MFPT (Minimum Flux) Per Torque), a motor control method in which the overmodulation index indicating maximum power efficiency is predetermined as the optimal overmodulation index.
delete delete According to paragraph 1,
The step of calculating the overmodulation index is,
Converting the first magnetic flux command into a third magnetic flux command based on a magnetic flux command correction table including a pre-measured magnetic flux command so that the actual overmodulation index of the electric motor is calculated to be 1.1547; and
Determining the optimal overmodulation index based on the third magnetic flux command
Including, an electric motor control method.
According to paragraph 1,
The step of controlling the electric motor is,
Controlling the electric motor based on a first voltage command calculated based on the current operating point,
When the magnitude of the first voltage command exceeds a predetermined threshold, the electric motor control method further includes performing compensation for the first voltage command.
A machine-readable recording medium containing a program including instructions implemented to cause a computing device to perform the electric motor control method of claim 1.
In a computing device that performs an electric motor control method,
Memory; and
processor
Including,
The processor,
Receives the angular velocity command and voltage command of the electric motor,
Calculating a first magnetic flux command based on the angular velocity command and voltage command,
Calculating a predetermined optimal overmodulation index in response to the value of the first magnetic flux command,
Calculating a second magnetic flux command based on the optimal overmodulation index,
Calculating a current operating point based on the second magnetic flux command and the received torque command,
Controlling the electric motor based on the current operating point,
The processor,
Determining the overmodulation index based on an optimal MI (Modulation Index) Table including an optimal overmodulation index corresponding to the torque command and the first magnetic flux command,
In the above optimal MI Table,
If the magnetic flux command calculated at the current operating point controlled by MI = 1.1547 is greater than or equal to the magnetic flux of the MTPA (Maximum Torque Per Ampere) curve, the optimal overmodulation index is predetermined to be 1.1547,
If the magnetic flux command calculated at the current operating point controlled by MI = 1.2732 is less than or equal to the magnetic flux of MFPT (Minimum Flux Per Torque), the optimal overmodulation index is predetermined to be 1.2732,
The magnetic flux command calculated at the current operating point controlled by MI = 1.1547 is smaller than the magnetic flux of the MTPA (Maximum Torque Per Ampere) curve, or the magnetic flux command calculated at the current operating point controlled by MI = 1.2732 is MFPT (Minimum Flux) Per Torque), a computing device in which the overmodulation index indicating maximum power efficiency is predetermined as the optimal overmodulation index.
delete delete In clause 7,
The processor,
Converting the first magnetic flux command to a third magnetic flux command based on a magnetic flux command correction table including a magnetic flux command measured in advance so that the actual overmodulation index of the motor is calculated to be 1.1547,
A computing device that determines the optimal overmodulation index based on the third flux command.