JP2021090285A - Motor control device - Google Patents

Abstract

To quickly and easily place a target current that is outside a voltage limit within a voltage limit.SOLUTION: On the basis of the position of an end point of a current vector obtained by combining a d-axis current command value and a q-axis current command value of an electric motor 15 with respect to a voltage limiting ellipse set in advance on a dq current coordinate plane, a target current is adjusted by correcting either the d-axis current command value or the q-axis current command value. Then, the d-axis voltage command value and the q-axis voltage command value of the electric motor 15 are obtained on the basis of the corrected d-axis current command value or q-axis current command value.SELECTED DRAWING: Figure 1

Description

The present invention relates to, for example, a motor control device that controls an electric motor mounted on a vehicle or the like.

In a multi-phase motor such as a brushless motor that is a power drive source for an electric vehicle or the like, when an excessive current is supplied from the power supply due to an increase in output requirement (motor load), the switching elements constituting the inverter circuit generate heat, break, etc. There is a risk of Therefore, when controlling the drive torque of the electric motor, a current limit is applied in the current control unit in order to protect the inverter, the motor, the vehicle, etc. from overvoltage, overcurrent, temperature rise, and the like.

Patent Document 1 pays attention to the fact that when there is a delay between the output of the angle detector of the motor and the output of the PWM converter, this delay affects the accuracy of the offset adjustment, so that the motor cannot be controlled accurately, and there is no load. With respect to the rotation position of the motor, based on the offset error correction value calculated from the d-axis current command value and the q-axis current command value when the motor in the state is speed-controlled by a constant current command value and rotated at a constant speed. A motor control device that calculates a correction value and controls the current of the motor is disclosed.

Japanese Patent No. 5916342

The conventional motor control device that performs feedback control so that the current flowing through the motor becomes the torque of the input torque command is the d-axis and q-axis from the data measured by tuning in order to obtain the torque output of the torque command. The torque output is controlled by determining the current value and controlling the current. Therefore, in the case of current control, it is necessary to operate within the limits of voltage and current.

The d-axis and q-axis current command values determined from the torque command are values tuned within the limits of voltage and current as described above, but for example, the current indicated values may be different due to temperature characteristics, manufacturing variations, etc. It is assumed that the voltage limit range may be exceeded. In such a case, there is a problem that the current control becomes unstable and oscillating.

Further, in the above-mentioned conventional motor control device, there is a problem that the motor control becomes complicated because the current control using the current command values of both the d-axis and the q-axis is required.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is a motor control device capable of keeping a target current outside the voltage limit range within the voltage limit range in a quick and simple manner. Is to provide.

The following configuration is provided as a means for achieving the above object and solving the above-mentioned problem. That is, the first exemplary invention of the present application is a motor control device that drives a brushless DC motor by vector control in the dq current coordinate plane, and the d-axis current command value and the q-axis current command of the brushless DC motor. A means for calculating a current vector obtained by combining values, a control unit for obtaining a d-axis voltage command value and a q-axis voltage command value of the brushless DC motor from the d-axis current command value and the q-axis current command value, and the above. A drive signal generator that generates a drive signal for the brushless DC motor based on the d-axis voltage command value and the q-axis voltage command value is provided, and the end point of the current vector with respect to the voltage limiting ellipse on the dq current coordinate plane is provided. It is characterized in that either the d-axis current command value or the q-axis current command value is corrected based on the position.

An exemplary second invention of the present application is a brushless DC motor, characterized in that it is driven by a motor control device according to the first exemplary invention.

An exemplary third invention of the present application is an electric vehicle, wherein the brushless DC motor according to the second exemplary invention is used as a traction motor.

An exemplary fourth invention of the present application is a motor control method for driving a brushless DC motor by vector control in the dq current coordinate plane, wherein the d-axis current command value and the q-axis current command value of the brushless DC motor are used. Based on the step of calculating the current vector obtained by synthesizing the above and the position of the end point of the current vector with respect to the voltage limiting ellipse on the dq current coordinate plane, either the d-axis current command value or the q-axis current command value. The step of obtaining the d-axis voltage command value and the q-axis voltage command value to the brushless DC motor from the d-axis current command value and the q-axis current command value, and the d-axis voltage command value and the said It is characterized by including a step of generating a drive signal of the brushless DC motor based on a q-axis voltage command value.

According to the present invention, even if the current command value determined by tuning is outside the voltage limiting ellipse, the current command value is voltage-limited by correcting either the d-axis current command value or the q-axis current command value. Can be easily accommodated in an ellipse.

FIG. 1 is a block diagram showing an overall configuration of a motor control device according to an embodiment of the present invention. FIG. 2 is a flowchart showing the current control procedure of the electric motor in the motor control unit in chronological order. FIG. 3 is a diagram schematically showing the correction process of the d-axis current. FIG. 4 is a diagram schematically showing the correction process of the q-axis current. FIG. 5 is a diagram schematically showing another correction process of the d-axis q-axis current.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an overall configuration of a motor control device according to an embodiment of the present invention.

The motor control device 20 of FIG. 1 includes, for example, a motor control unit 10 that functions as a drive control unit of an electric motor 15 that is a three-phase brushless DC motor. The electric motor 15 includes a type in which the motor body and the motor drive device (ECU) are not integrated, and a type in which they are integrated (mechanical and electrical integrated motor).

As will be described later, the motor control device 20 performs current feedback control so that the q-axis current value and the d-axis current value follow the q-axis current command value and the d-axis current command value, and calculates based on the current feedback control. A PWM control signal for each phase is generated from the obtained q-axis voltage command value and d-axis voltage command value, and the electric motor 15 is driven and controlled by an inverter which is a motor driving unit.

The motor control device 10 includes a microprocessor (CPU) that controls the entire motor control device 10, and is a predetermined program based on various input information while referring to data or the like stored in a storage unit (not shown). To execute.

The storage unit 35 includes, for example, an EEPROM (Electrically Erasable and Programmable Read Only Memory) that can be electrically written and erased, an electrically rewritable flash memory, and the like.

The PWM signal generation unit 21 of the motor control unit 10 generates ON / OFF control signals (PWM signals) of a plurality of semiconductor switching elements (FETs) constituting the inverter circuit 23 according to the input voltage command value. The semiconductor switching elements are arranged corresponding to each phase (a phase, b phase, c phase) of the electric motor 15.

The switching element is also called a power element, and for example, a switching element such as a MOSFET (Metal-Oxide Semiconductor Field-Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor) is used.

Power for driving the motor (power supply voltage is + B) is supplied to the inverter circuit 23 from the external battery BT via the power supply relay 27. The power relay 27 is configured to be able to cut off the electric power from the battery BT, and can also be configured by a semiconductor relay.

The motor drive current supplied from the inverter circuit 23 as the motor drive circuit to the electric motor 15 is detected by the current detection unit 25 including current sensors (not shown) arranged corresponding to each phase. The current detection unit 25 detects, for example, an electric signal from a Hall sensor for detecting a motor drive current by using an amplifier circuit including an operational amplifier or the like.

The output signal (current detection signal) from the current detection unit 25 is input to the A / D conversion unit (ADC) 28. The ADC 28 converts an analog current value into a digital value by its A / D conversion function, and inputs the three-phase currents Ia, Ib, and Ic to the coordinate conversion unit (3-phase / 2-phase conversion unit) 29. The coordinate conversion unit 29 calculates the current Id on the d-axis and the current Iq on the q-axis from the rotation angle θ detected by the rotation angle sensor 51 and the three-phase currents (actual currents) Ia, Ib, and Ic. The rotation angular velocity ωm is calculated by performing approximate differentiation or the like based on the rotation angle θ, for example.

The current that can be passed through the electric motor 15 is determined by the rotation speed of the motor and the power supply voltage. Therefore, the target current calculation unit 11 performs an operation to keep the input first target q-axis current Iq ₁ ^* and the first target d-axis current Id ₁ ^* within a predetermined range.

Therefore, the target Iq calculation unit 11a constituting the target current calculation unit 11 calculates the second target q-axis current Iq ₂ ^* by, for example, correcting the calculated or tabulated current value according to the torque command value. To do.

The weakening magnetic flux control unit 11b constituting the target current calculation unit 11 refers to the Id and Iq maps calculated or tabulated and stored in the storage unit (not shown), and then d of the rotating field of the three-phase brushless DC motor. The second target d-axis current Id is controlled by weakening the magnetic flux that causes a negative d-axis current to flow through the motor so as to weaken the magnetic flux in the axial direction, or by controlling the current in the q-axis direction to fluctuate in the direction in which the absolute value becomes smaller. ₂ ^* and the second target q-axis current Iq ₂ ^* are calculated.

The calculated or tabulated current value described above depends on, for example, the design of the motor, and is a value that changes according to each design.

In the control of the weakening magnetic flux control unit 11b, in the control of the electric motor 15, a weakening field state that reduces the d-axis current, which is the field current, is used so as not to exceed the upper limit of the applied voltage that can be output by the inverter circuit 23. doing.

In order to regulate the maximum current that can be passed through the electric motor 15 or the like, the current vector limiting unit 12 sets the upper limit of the _second ^{target d-axis current Id 2 *, which is the output (weakened field current) from the target current calculation unit 11.} , The upper limit of the second target q-axis current Iq ₂ ^{* is set.} Therefore, the current vector limiting unit 12 outputs the third q-axis current Iq ₃ ^* for which the upper limit value is set and the third target d-axis current Id ₃ ^* .

Here, the third q-axis current Iq ₃ ^* is the q-axis command current which is a torque component, and the third target d-axis current Id ₃ ^* is the d-axis command current which is a magnetic field component.

The subtractor 13a calculates the difference between the third q-axis current Iq ₃ ^* and the q-axis current Iq calculated by the coordinate conversion unit 29, and the difference is input to the PI control unit 16a. Similarly, the subtractor 13b calculates the difference between the third target d-axis current Id ₃ ^* and the d-axis current Id calculated by the coordinate conversion unit 29, and the difference is input to the PI control unit 16b.

The PI control unit 16a performs PI (proportional + integration) control so as to converge the above-mentioned difference to zero, and calculates the ^{q-axis voltage command value Vq *, which is the command value of the q-axis voltage.} Similarly, the PI control unit 16b also calculates the ^{d-axis voltage command value Vd *} , which is the command value of the d-axis voltage, by performing PI (proportional + integration) control so as to converge the above-mentioned difference to zero.

The non-interference control unit 18 calculates the q-axis non-interference voltage and the d-axis non-interference voltage from the rotation speed of the electric motor 15, the third target q-axis current Iq ₃ ^* , the third target d-axis current Id ₃ ^{*, and the like.} To do. Then, in the adders 19a and 19b, voltage feed forward control is performed in which the q-axis non-interfering voltage and the d-axis non-interfering voltage are added to the ^{q-axis voltage command value Vq *} and the d-axis voltage command value Vd ^{*, respectively.}

The outputs (q-axis voltage command value Vq ^* , d-axis voltage command value Vd ^* ) from the adders 19a and 19b are input to the coordinate conversion unit 17 having a 2-phase / 3-phase conversion function. The coordinate conversion unit 17 converts Vq ^* and Vd ^{* into voltage command values Va *} , Vb ^* , and Vc ^* , which are voltage command values for each of the three phases, based on the rotation angle θ. The converted voltage command values Va ^* , Vb ^* , and Vc ^* are input to the PWM signal generation unit 21.

Next, a current control method for the electric motor in the motor control device according to the present embodiment will be described. FIG. 2 is a flowchart showing the current control procedure of the electric motor in the motor control unit 10 of the motor control device 20 shown in FIG. 1 in chronological order.

In step S11 of FIG. 2, the q-axis current and the d-axis current with respect to the indicated torque (target torque) Tq input from the outside are obtained. Here, as described above, the q-axis current and the d-axis current corresponding to the indicated torque Tq are determined from the q-axis current and the d-axis current calculated in advance or measured on the bench and stored in the storage unit as a table.

^{In step S13, the voltage vector calculation unit 1 obtains the magnitude Vdq *} of the voltage vector based on the above-mentioned q-axis voltage command value Vq ^* and d-axis voltage command value Vd ^* by the following equation (1).

Vdq ^* = √ (Vd ^{* 2} + Vq ^{* 2} )… (1)

In step S15, the phase voltage effective value (+ B × maximum modulation) calculated based on ^{the magnitude Vdq *} of the voltage vector as the voltage command value obtained by the equation (1) and the drive power supply voltage + B of the motor control unit 10. Compare with rate / √2). If Vdq ^* ≦ (+ B × maximum modulation factor / √2), the voltage command value is within the range of the power supply voltage, so that the normal current limiting process is executed (step S17).

On the other hand, ^{when it is determined in step S15 that Vdq *} > (+ B × maximum modulation factor / √2), the voltage command value is out of the limit of the power supply voltage, Vdq ^* is too large, and the motor control device 10 is notified. Assuming that the motor voltage cannot be realized even if the voltage of the supplied drive power supply (battery) is used to the maximum, the process proceeds to the following process.

That is, in step S19, a current vector obtained by combining the q-axis current (q-axis current command value) and the d-axis current (d-axis current command value) obtained in step S11 is calculated. This current vector is a combined current vector of the d-axis current vector and the q-axis current vector starting from the intersection of the d-axis and the q-axis on the dq current coordinate plane.

In the following step S21, the CPU 1 determines the sign of the q-axis voltage command value (referred to as Vq). This is because the position of the end point of the combined current vector with respect to the voltage limiting ellipse is determined based on the sign of the q-axis voltage command value.

Here, the voltage limiting ellipse is a range determined by values that can be output by the motor characteristics such as the power supply voltage (+ B), rotation speed, and phase resistance of the electric motor 15 on the dq current coordinate plane, that is, according to the power supply voltage and the like. It is a range indicating the voltage limit of the composite vector that can be set.

When it is determined in step S21 that Vq <0, it is determined in step S15 that the magnitude of the voltage vector exceeds the phase voltage effective value. Therefore, in step S23, the d-axis current vector calculated in step S19 is described. And the q-axis current vector It is determined that the end point of the current vector is outside the voltage limiting ellipse and is located on the right side of the straight line that passes through the center of the voltage limiting ellipse and extends in the q-axis direction of the voltage limiting ellipse. To do.

Then, in step S25, the weakening magnetic flux control unit 11b of the target current calculation unit 11 performs correction (adjustment of the target current) to change the d-axis current in the negative direction by a method described later.

In step S27, as a result of changing the d-axis current in the negative direction as described above, it is determined whether or not the end point of the combined current vector has reached the voltage limiting ellipse. If the end point of the current vector has not reached the voltage limiting ellipse, the process returns to step S25, and the correction for adjusting the d-axis current in the negative direction is continued until the voltage limiting ellipse is reached.

On the other hand, when it is determined in step S21 that Vq ≧ 0, it is determined in step S15 that the magnitude of the voltage vector exceeds the effective phase voltage value. Therefore, in step S31, it is calculated in step S19. If the end point of the combined current vector of the d-axis current vector and the q-axis current vector is outside the voltage limiting ellipse and is on the left side of the straight line that passes through the center of the voltage limiting ellipse and extends in the q-axis direction of the voltage limiting ellipse. to decide. Then, in step S33, correction (adjustment of the target current) is performed to change the q-axis current in the direction in which the absolute value becomes smaller by the method described later.

In step S35, as a result of changing the q-axis current as described above, it is determined whether or not the end point of the combined current vector has reached the voltage limiting ellipse. If the end point of the current vector has not reached the voltage limiting ellipse, the process returns to step S33, and the correction for adjusting the absolute value of the q-axis current to decrease is continued until the voltage limiting ellipse is reached.

In step S37, the d-axis voltage command value and the q-axis voltage, which are the drive signals of the electric motor 15, are based on the d-axis current command value or the q-axis current command value obtained by the current adjustment in step S25 or step S33. Generate a command value. Then, in step S39, the electric motor 15 is driven and controlled by a PWM signal for ON / OFF control of the semiconductor switching element of the inverter circuit according to the voltage command value generated in step S37.

FIG. 3 schematically shows the processing of steps S25 and S27 of FIG. In FIG. 3, the end point 35a of the combined current vector 35 of the d-axis current vector and the q-axis current vector obtained by tuning in advance is outside the voltage limiting ellipse 30. Further, the end point 35a is located on the right side of a straight line 32 that passes through the center O of the voltage limiting ellipse 30 and extends in the q-axis direction of the voltage limiting ellipse 30.

That is, the combined current vector 35 is not in the range determined by the value that can be output by the power supply voltage (+ B). Therefore, since the weakening magnetic flux control unit 11b of the target current calculation unit 11 causes a negative d-axis current to flow through the electric motor 15, the q-axis current (target q-axis current 33) is as shown by reference numeral 36 in FIG. , The value is maintained, and the end point 35a is moved in the direction along the d-axis to perform correction (adjustment) to change the d-axis current in the negative direction.

Such adjustment of the d-axis current is performed until the end point 35a of the current vector reaches the voltage limiting ellipse 30 (that is, until the point A is reached). As a result, a current 34 including a target d-axis current 31 and a target q-axis current 33 is obtained. Therefore, a current vector (current indicated value) satisfying the voltage limit can be easily and quickly obtained only by maintaining the q-axis current and correcting the d-axis current.

This means that the d-axis current, which is a field current, can be corrected by weakening magnetic flux control so as not to exceed the upper limit of the applied voltage that can be output by the electric motor 15 (brushless DC motor).

FIG. 4 schematically shows the processing of steps S33 and S35 of FIG. As shown in FIG. 4, the end point 45a of the combined current vector 45 of the d-axis current vector and the q-axis current vector obtained by tuning in advance is outside the voltage limiting ellipse 30. Further, the end point 45a is located on the left side of a straight line 32 that passes through the center O of the voltage limiting ellipse 30 and extends in the q-axis direction of the voltage limiting ellipse 30.

Even in this case, the combined current vector 45 is not in the range determined by the value that can be output by the power supply voltage (+ B). In such a case, if the weakening magnetic flux control shown in FIG. 3 is performed, the q-axis current continues to increase in the negative direction without the end point 45a of the combined current vector 45 intersecting with the voltage limiting ellipse 30.

Therefore, the target IQ calculation unit 11a of the target current calculation unit 11 maintains the value of the d-axis current and sets the end point 45a as shown by reference numeral 46 in FIG. 4 in order to reduce the q-axis current flowing through the electric motor 15. Adjustment is performed to move in the direction along the q-axis and change the value of the q-axis current so that the value becomes smaller in the negative direction of the q-axis.

Similar to the case of the d-axis current, when adjusting the q-axis current, the adjustment is performed until the end point 45a of the current vector reaches the voltage limiting ellipse 30 (that is, until the point B is reached). As a result, a current 44 including a target d-axis current 41 and a target q-axis current 43 is obtained.

In the above case, the end point 45a of the combined current vector 45 is outside the voltage limiting ellipse 30 and above the d-axis of the voltage limiting ellipse 30, but the end point is as shown in the combined current vector 55 of FIG. When 55a is outside the voltage limiting ellipse 30 and is below the d-axis of the voltage limiting ellipse 30, the same adjustment as above is performed.

That is, as shown by reference numeral 56 in FIG. 4, an adjustment is made to maintain the value of the d-axis current and change the q-axis current until the point C is reached so that the value decreases in the positive direction of the q-axis. Do.

Therefore, a current vector (current indicated value) satisfying the voltage limit can be easily and quickly obtained only by maintaining the d-axis current and correcting the q-axis current.

In this way, the adjustment of the q-axis current differs in the direction of reducing the current depending on the sign of the q-axis current. From this, the adjustment of the q-axis current in the target IQ calculation unit 11a is a correction that changes the absolute value in the direction of decreasing.

In the processes shown in FIGS. 3 and 4, as a result of the above current adjustment, for example, the current vector has dropped to a d-axis current value or a q-axis current value that can be handled within the current battery voltage range. , It is determined that the end point of the combined current vector has reached the voltage limiting ellipse 30.

When the end point 65a of the combined current vector 65 of the d-axis current vector and the q-axis current vector is at the position shown in FIG. 5, the value of the q-axis current is maintained and the end point 65a is indicated by reference numeral 66. The d-axis current is changed in the negative direction by moving until the straight line 32 is reached. Further, as shown by reference numeral 68, the end point 65a is moved along the straight line 32 until the point D is reached, and the value of the q-axis current is adjusted so as to decrease in the negative direction of the q-axis. As a result, a current 64 including the target d-axis current 61 and the target q-axis current 63 can be obtained.

The motor control device and motor control method described above can be used, for example, by mounting them on an electric vehicle that uses a brushless DC motor as a traction motor. Then, in motor control in an electric vehicle, a target current outside the voltage limit range can be quickly and easily set within the voltage limit range. In addition, it is possible to prevent the current control of the traction motor in the electric vehicle from becoming unstable and oscillating.

As described above, the motor control device according to the present embodiment is a current vector obtained by synthesizing the d-axis current command value and the q-axis current command value of the brushless DC motor with respect to the voltage limiting ellipse assumed on the dq current coordinate plane. Either the d-axis current command value or the q-axis current command value is corrected based on the position of the end point of the electric motor (brushless DC motor) based on the corrected d-axis current command value or the q-axis current command value. ), The d-axis voltage command value and the q-axis voltage command value are obtained.

In this way, by correcting either the d-axis current or the q-axis current based on the vector position of the target current, it is possible to easily and quickly perform the process of keeping the current command value within the current limit range. For example, even if the current indicated value is out of the limit range due to variations due to the temperature characteristics of the motor, manufacturing, etc., it can be kept within the current limit range by correction, so that the current control becomes unstable and oscillating. Can be suppressed.

Therefore, the current of a motor such as a permanent magnet embedded synchronous motor (IPMSM) can be controlled within the limited range (maximum range of the current limited region).

Further, when the current is corrected, the voltage can be limited by a simple process that eliminates the variation due to the motor parameter by performing the correction without using the motor parameter including the inductance, the resistance, the magnetic flux and the like.

1 Voltage vector calculation unit 10 Motor control unit 11 Target current calculation unit 11a Target Iq calculation unit 11b Weak magnetic flux control unit 12 Current vector limiting unit 15 Electric motor 16a, 16b PI control unit 17, 29 Coordinate conversion unit 18 Non-interference control unit 20 Motor control device 21 PWM signal generation unit 23 Inverter circuit 25 Current detection unit 27 Power supply relay 28 A / D conversion unit (ADC)
51 Rotation angle sensor BT external battery

Claims (13)

A motor control device that drives a brushless DC motor by vector control on the dq current coordinate plane.
A means for calculating a current vector obtained by combining the d-axis current command value and the q-axis current command value of the brushless DC motor, and
A control unit that obtains the d-axis voltage command value and the q-axis voltage command value of the brushless DC motor from the d-axis current command value and the q-axis current command value.
A drive signal generator that generates a drive signal for the brushless DC motor based on the d-axis voltage command value and the q-axis voltage command value.
With
A motor control device that corrects either the d-axis current command value or the q-axis current command value based on the position of the end point of the current vector with respect to the voltage limiting ellipse on the dq current coordinate plane. The position of the end point of the current vector with respect to the voltage limiting ellipse is based on the magnitude of the voltage vector calculated based on the d-axis voltage command value and the q-axis voltage command value, and the sign of the q-axis voltage command value. The motor control device according to claim 1. When the end point of the current vector is outside the voltage limiting ellipse and the q-axis voltage command value is Vq, Vq ≧ 0, passing through the center of the voltage limiting ellipse and in the q-axis direction of the voltage limiting ellipse. The motor control device according to claim 2, wherein when the current is on the left side of the straight line to be stretched, correction is performed to change the q-axis current in a direction in which the absolute value becomes smaller. The correction maintains the value of the d-axis current of the current vector and reduces the absolute value of the q-axis current in the q-axis direction until the end point of the current vector reaches the elliptical line of the voltage limiting ellipse. The motor control device according to claim 3, which moves. When the end point of the current vector is outside the voltage limiting ellipse and the q-axis voltage command value is Vq, Vq <0, passing through the center of the voltage limiting ellipse and in the q-axis direction of the voltage limiting ellipse. The motor control device according to any one of claims 2 to 4, wherein a correction for changing the d-axis current in a negative direction is performed when the current is on the right side of the straight line to be stretched. The correction maintains the value of the q-axis current of the current vector and increases the value of the d-axis current in the negative direction until the end point of the current vector reaches the elliptical line of the voltage limiting ellipse. The motor control device according to claim 5, which moves in a direction. The motor control device according to any one of claims 1 to 6, wherein the correction corrects the d-axis current command value so as to weaken the field magnetic flux of the brushless DC motor. The correction according to any one of claims 1 to 7, wherein the correction is performed at least independently of the inductance, resistance, and magnetic flux of the brushless DC motor, and the current command value is kept within the current limit range by the voltage limiting ellipse. Motor control device. The motor control device according to any one of claims 1 to 8, wherein the brushless DC motor is an embedded permanent magnet synchronous motor (IPMSM). A brushless DC motor driven by the motor control device according to any one of claims 1 to 9. An electric vehicle that uses the brushless DC motor according to claim 10 as a traction motor. A motor control method that drives a brushless DC motor by vector control on the dq current coordinate plane.
A step of calculating a current vector obtained by combining the d-axis current command value and the q-axis current command value of the brushless DC motor, and
A step of correcting either the d-axis current command value or the q-axis current command value based on the position of the end point of the current vector with respect to the voltage limiting ellipse on the dq current coordinate plane.
A step of obtaining a d-axis voltage command value and a q-axis voltage command value for the brushless DC motor from the d-axis current command value and the q-axis current command value.
A step of generating a drive signal of the brushless DC motor based on the d-axis voltage command value and the q-axis voltage command value, and
A motor control method comprising. In the correction step, the value of the q-axis current of the current vector is maintained, and the value of the d-axis current is increased in the negative direction until the end point of the current vector reaches the elliptical line of the voltage limiting ellipse. Until the end point of the current vector reaches the elliptical line of the voltage limiting ellipse by moving in the axial direction or maintaining the value of the d-axis current of the current vector and reducing the absolute value of the q-axis current. The motor control method according to claim 12, which moves in the q-axis direction.

Images