Method for controlling an electric motor, and control device for an electric motor.

Abstract

To provide a control method of a motor that improves stability of control in a predetermined operation region, and a motor controller.SOLUTION: A method for controlling an electric motor calculates a voltage command value based on a current command value, converts a DC voltage into an AC voltage based on a PWM signal calculated based on the voltage command value to output it to the electric motor. The voltage command value is calculated by multiplying difference between the current command value and a dq axis current value obtained by converting a current flowing through a motor into a dq coordinates axis with a phase angle of a rotor of the electric motor being a reference. A control gain is calculated based on a compensation inductance value obtained by multiplying an inductance value of the electric motor by a compensation gain for adjusting the inductance value. The compensation gain is set to a value of one or less, and is set so as to become smaller as the number of revolutions or torque of the motor becomes larger.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for controlling an electric motor and a control device for an electric motor. [Background technology]

[0002] Patent Document 1 discloses a motor control device that detects the current value flowing through the armature winding and performs feedback control. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2014-54127 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, in Patent Document 1, a control system is implemented that corrects errors in the inductance value by estimation using feedback control in response to changes in the inductance value of the armature winding due to factors such as changes in current. However, correcting the inductance value of the armature winding may impede the stability of the control depending on the motor's operating range (for example, the high torque range or high rotation range).

[0005] The present invention aims to provide a motor control method and a motor control device that enhance the stability of control in a predetermined operating range. [Means for solving the problem]

[0006] The electric motor control method according to the present invention is a method for controlling an electric motor that calculates a voltage command value based on a current command value, and converts a DC voltage to an AC voltage based on a PWM signal calculated based on the voltage command value and outputs it to the electric motor. In this control method, the voltage command value is calculated by multiplying the difference between the current command value and the dq-axis current value obtained by converting the current flowing through the electric motor into a dq coordinate axis with reference to the phase angle of the electric motor rotor by a control gain. The control gain is calculated based on a compensation inductance value obtained by multiplying the electric motor's inductance value by a compensation gain for adjusting the inductance value. The compensation gain is set to a value of 1 or less, and is set to decrease as the motor's rotational speed or torque increases. The current command value includes the d-axis current command value, which is the d-axis component of the dq coordinate axes, and the q-axis current command value, which is the q-axis component of the dq coordinate axes; the dq-axis current value includes the d-axis current value, which is the d-axis component; the voltage command value includes the d-axis voltage command value, which is the d-axis component, and the q-axis voltage command value, which is the q-axis component; the inductance value includes the d-axis inductance value; the compensation gain includes the d-axis compensation gain; and the compensation inductance value includes the d-axis compensation inductance value. The d-axis inductance value is set to a calculated value based on the d-axis current command value, the q-axis current command value, and the q-axis voltage command value, or to a predetermined fixed value. The control gain includes the d-axis control gain calculated based on the d-axis compensation inductance value obtained by multiplying the d-axis inductance value by the d-axis compensation gain. The d-axis voltage command value is calculated by multiplying the difference between the d-axis current command value and the d-axis current value by the d-axis control gain. The d-axis compensation gain is set to 1 until the absolute value of the rotational speed reaches a predetermined rotational speed, and then set to a value lower than 1 when the predetermined rotational speed is exceeded. The predetermined rotational speed is set to the rotational speed of the motor at which the electrical angular period of the motor corresponding to the predetermined rotational speed approximately matches the dead time of the control loop used to calculate the voltage command value. . [Effects of the Invention]

[0007] According to the present invention, current control can be performed while ensuring the desired stability in a predetermined operating region where control stability tends to be insufficient, namely the high torque region or the high rotation region. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows an example of the basic configuration of the control device for an electric motor according to the first embodiment. [Figure 2] Figure 2 shows the relationship between the motor speed and the d-axis compensation gain in the first embodiment. [Figure 3] Figure 3 is a control flow diagram of the control device for the electric motor according to the first embodiment. [Figure 4] Figure 4 shows an example of the basic configuration of the control device for the electric motor according to the second embodiment. [Figure 5] Figure 5 is a control flow diagram of the control device for the electric motor according to the second embodiment. [Figure 6] Figure 6 shows the relationship between the motor torque and the q-axis compensation gain of the second embodiment. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the attached drawings.

[0010] [First Embodiment] Figure 1 shows an example of the basic configuration of the control device for an electric motor according to the first embodiment.

[0011] The control device (control method) for the electric motor (motor 18) in the first embodiment controls the motor 18 of an electric vehicle. The electric vehicle includes not only electric vehicles that use the motor 18 as a driving force, but also hybrid vehicles and fuel cell vehicles.

[0012] The motor 18 illustrated in Figure 1 has a stator and a rotor. The type of rotor for the motor 18 is not limited; for example, permanent magnet rotors, wound rotors, and cage rotors are applicable.

[0013] The control device for the motor of the first embodiment includes a current command generation unit 1, an interference voltage generation unit 2, an inductance estimation unit 3, a compensation gain calculation unit 4, a P control unit 5, an I control unit 6, an adder / subtractor 7A, an adder 7B, a dq-axis / UVW-phase conversion unit 8, a PWM conversion unit 9, an inverter 10, a voltage sensor 11, a current sensor 12A, a current sensor 12B, a rotor position sensor 13, a UVW-phase / dq-axis conversion unit 14, a subtractor 15A, a subtractor 15B, and a rotational speed calculation unit 16.

[0014] Furthermore, the motor control device of the first embodiment has a control loop that cycles in the following order: subtractor 15A (subtractor 15B), P control unit 5 (I control unit 6), adder / subtractor 7A (adder 7B), dq axis / UVW phase conversion unit 8, PWM conversion unit 9, inverter 10, current sensor 12A (current sensor 12B), UVW phase / dq axis conversion unit 14, subtractor 15A (subtractor 15B), and a voltage command value (final d axis voltage command value v d * , final q-axis voltage command value v q * ) is feedback controlled.

[0015] The current command generation unit 1 receives the torque command value T *, the rotational speed N of the motor 18 and the DC voltage V of the battery 19 (smoothing capacitor) dc are input. The current command generation unit 1 has a torque command value T * , the rotational speed N, the DC voltage V dc , and a d-axis current command value i corresponding to the temperature of the motor 18 d * , and a q-axis current command value i q * in a table prepared in advance.

[0016] When the torque command value T * , the rotational speed N, the DC voltage V dc , and the temperature of the motor 18 are input, the current command generation unit 1 refers to the table to obtain the d-axis current command value i d * , and the q-axis current command value i q * and outputs them.

[0017] The interference voltage generation unit 2 receives the torque command value T * , the rotational speed N of the motor 18, and the DC voltage V of the battery 19 (smoothing capacitor) dc as input. The interference voltage generation unit 2 has a d-axis interference voltage v corresponding to the torque command value T * , the rotational speed N, the DC voltage V dc , and the temperature of the motor 18 d_dcpl * , and a q-axis interference voltage v q_dcpl * in a table prepared in advance.

[0018] When the torque command value T * , the rotational speed N, the DC voltage V dc , and the temperature of the motor 18 are input, the interference voltage generation unit 2 refers to the table to obtain the d-axis interference voltage v d_dcpl * , and the q-axis interference voltage v q_dcpl * and outputs them.

[0019] The inductance estimation unit 3 receives the d-axis current command value i d * , and the q-axis current command value i q* The following is input. The inductance estimation unit 3 calculates the d-axis current command value i d * Table corresponding to this, and q-axis current command value i q * A corresponding table is provided in advance. The inductance estimation unit 3 receives the d-axis current command value i d * When input, the table for the d-axis is referenced to estimate the d-axis inductance value L. d_est Outputs the q-axis current command value i q * When input is received, the estimated q-axis inductance value L is obtained by referring to the table for the q-axis. q_est Outputs.

[0020] The inductance estimation unit 3 uses the following equation (1) to determine the d-axis inductance value L d_est , and the q-axis inductance value L q_est It is also possible to calculate it using the true value.

number

[0021] Here, ω c ω is the cutoff frequency for current control (vector current control). c (Known), Φ is the induced voltage constant of the armature winding (Known), R a v is the resistance (known) of the armature (stator) winding, dp * This is the P-control d-axis voltage command value v, which will be described later. dp * (Previous value), v qp * This is the P-control q-axis voltage command value v, which will be described later. qp * (Previous value)

[0022] Furthermore, the inductance estimation unit 3 calculates the d-axis inductance value L d_est , and the q-axis inductance value L q_est The d-axis current command value i d * and q-axis current command value i q* Regardless, each may be set to a predetermined fixed value.

[0023] The compensation gain calculation unit 4 receives the d-axis inductance value L d_est , the q-axis inductance value L q_est , and the rotational speed N. The compensation gain calculation unit 4 has a table in advance for calculating the d-axis compensation gain K ω (see FIG. 2) corresponding to the rotational speed N of the motor 18.

[0024] When the compensation gain calculation unit 4 receives the d-axis inductance value L d_est , the q-axis inductance value L q_est , it calculates the d-axis compensation value L d_est that results in the compensated d-axis inductance value L d_est_comp (d-axis compensation inductance value), and the q-axis compensation value L q_est that results in the compensated q-axis inductance value L q_est_comp (q-axis compensation inductance value) as shown in the following equation (2). <{}

Equation

[0025] The subtractor 15A calculates the d-axis difference value (i d * - i d ) by subtracting the d-axis current value i d * described later from the d-axis current command value i d .

[0026] The subtractor 15B calculates the q-axis difference value (i q * - i q ) by subtracting the q-axis current value i q * [[ID=) by subtracting the q-axis current value i -i q described later from the q-axis current command value i

[0027] The P control unit 5 receives the d-axis difference value (i d * - i d ), the q-axis difference value (i <000009{>* -i q ) d-axis compensation value L d_est_comp and q-axis compensation value L q_est_comp are inputted.

[0028] The P control unit 5 has a cut-off frequency ω c d-axis compensation value L d_est_comp q-axis compensation value L q_est_comp Based on these, the d-axis proportional gain K dp (control gain), and the q-axis proportional gain K qp (control gain) are calculated as shown in the following equation (3). [Equation]

[0029] Further, the P control unit 5 calculates the P control d-axis voltage command value v d * -i d ) and the d-axis proportional gain K dp as shown in the following equation (4), and calculates the P control q-axis voltage command value v[[ID=,ID=39]] dp * based on the q-axis difference value (i q * -i q ) and the q-axis proportional gain K qp as shown in the following equation (4). qp * [Equation] [Equation] [[ID=,ID=57]]

[0030] The d-axis difference value (i d * -i d ) and the q-axis difference value (i q * -i[[ID=7,ID=70]] q ) are inputted to the I control unit 6.

[0031] The I control unit 6 calculates the d-axis integral gain K a based on the armature (stator) winding resistance R c and the cut-off frequency ω di, and the q-axis integral gain K qi Calculate.

number

[0032] Furthermore, the I control unit 6 controls the d-axis difference value (i) as shown in equation (6) below. d * -i d ) and d-axis integral gain K di Based on this, the I control d axis voltage command value v di * Calculate the q-axis difference value (i q * -i q ) and q-axis integral gain K qi Based on this, the I control q axis voltage command value v qi * Calculate.

number

[0033] Note that the d-axis integral gain K di The above d-axis compensation gain K ω You may also multiply by the q-axis integral gain K. qi The q-axis compensation gain K described later T You can also multiply by it.

[0034] The adder / subtractor 7A controls the P control d-axis voltage command value v as shown in equation (7) below. dp * I control d axis voltage command value v di * d-axis interference voltage v d_dcpl * Based on this, the final d-axis voltage command value v d * Calculate.

number

[0035] The adder 7B controls the P control q axis voltage command value v as shown in equation (8) below. qp* I control q axis voltage command value v qi * , and q-axis interference voltage v q_dcpl * Based on this, the final q-axis voltage command value v q * Calculate.

number

[0036] The dq-axis / UVW phase conversion unit 8 receives the final d-axis voltage command value v d * , final q-axis voltage command value v q * The electrical angle θ detected by the rotor position sensor 13 is input.

[0037] The dq-axis / UVW phase conversion unit 8 calculates the final d-axis voltage command value v according to equation (9) shown below. d * , and the final q-axis voltage command value v q * , to the three-phase voltage command value (v u * ,v v * ,v w * Convert to (and output).

number

[0038] The PWM conversion unit 9 performs dead time compensation and voltage utilization rate improvement processing (both known), and also converts the three-phase voltage command value (v u * ,v v * ,v w * ) Drive signal for power element of inverter 10 corresponding to (D uu * ,D ul * ,D vu * ,D vl * ,D wu* ,D wl * Generates a PWM signal.

[0039] The inverter 10 is connected to a battery 19 and a smoothing capacitor (not shown). The inverter 10 receives a drive signal (D) for the power elements. uu * ,D ul * ,D vu * ,D vl * ,D wu * ,D wl * When a signal is input, it drives a power element (IGBT, etc.) to produce the output voltage (DC voltage V) of the battery 19. dc ) is a pseudo AC voltage (v u ,v v ,v w It is converted to ) and output to motor 18.

[0040] The voltage sensor 11 detects the DC voltage V of the battery 19. dc It detects.

[0041] The current sensor 12A detects, for example, the U-phase current value i of the three-phase current supplied to the motor 18. u , and the current sensor 12B detects the V-phase current value i v It detects the W-phase current value i that is not detected. w In principle, this can be calculated using the following equation (10).

number

[0042] The rotor position sensor 13 detects the electrical angle θ of the rotor of the motor 18.

[0043] The UVW phase / dq axis conversion unit 14 has a U-phase current value i u V-phase current value i v The electric angle θ is input.

[0044] The UVW phase / dq axis conversion unit 14 converts the U phase current value i u V-phase current value i v , the electrical angle θ, and the W-phase current value i calculated by (10) w Based on this, the three-phase current value (i) is calculated using equation (11) shown below. u ,i v ,i w ) d-axis current value i d (dq axis current value), q axis current value i q Convert and output the (dq axis current value).

number

[0045] The rotation speed calculation unit 16 calculates and outputs the rotation speed N of the motor 18 from the rate of change of the electrical angle θ per unit time.

[0046] Figure 2 shows the rotational speed N and d-axis compensation gain K of the motor 18 in the first embodiment. ω This figure shows the relationship (table). As shown in Figure 2, the compensation value shown by the d-axis compensation gain Kω is 1 from zero absolute value of rotational speed N to a predetermined rotational speed N1, but in the range above the predetermined rotational speed N1, it draws a curve that decreases monotonically as the rotational speed N increases.

[0047] Here, the predetermined rotational speed N1 is set based on the current control period of the motor control device of this embodiment. For example, it corresponds to the rotational speed N when the period of rotation of the electrical angle θ of the motor 18 approximately matches the dead time (control delay time) of the control loop that calculates the voltage command value by feedback control. Here, dead time is, for example, the time from when the voltage command value is output until the output of the motor 18 (d-axis current, q-axis current) begins to reflect that voltage command value. In any case, Figure 2 shows the case where the compensation amount is set to ensure stability (phase margin) of a certain value or more, and the compensation value changes depending on the control design criteria.

[0048] Incidentally, regarding the frequency characteristics (Bode plot) of the gain and phase of the control loop mentioned above, the gain characteristic curve, which shows the relationship between gain and frequency, decreases monotonically as the frequency increases, but increases monotonically as it approaches the peak frequency (e.g., 1000 Hz), reaching a maximum value at the peak frequency, and then decreases monotonically again as the frequency rises above the peak frequency. At this point, the gain is higher than 0 dB at the peak value.

[0049] Furthermore, the phase characteristic curve, which shows the relationship between phase and frequency, shows that the phase is at its maximum (e.g., around 15 degrees) at frequencies lower than the peak frequency (e.g., 600 Hz), but decreases sharply above that frequency, reaching -180 degrees at the inversion frequency (e.g., 1500 Hz).

[0050] Furthermore, if the peak frequency is close to the control frequency of the control loop (especially the frequency corresponding to the dead time), the stability of the motor control decreases when the rotational speed N of the motor 18 approaches a predetermined rotational speed N1 (e.g., 10,000 [rpm]) at which it converges due to the peak frequency. Also, while the required phase margin (e.g., 40 [deg]) can be secured when the rotational speed N is lower than the equivalent of the peak frequency, it becomes difficult to secure the required phase margin when it exceeds the predetermined rotational speed N1.

[0051] Therefore, in this embodiment, as shown in Figure 2, the q-axis compensation gain K T The motor 18's rotational speed N is set to 1 when it is below a predetermined rotational speed N1, and when it exceeds the predetermined rotational speed N1, it is set to decrease monotonically as the rotational speed N increases. Furthermore, the d-axis compensation value L d_est_comp This is calculated as shown in equation (2). As a result, the gain characteristic curve shifts generally towards lower gain. Therefore, the gain crossover frequency that is higher than the peak frequency of the gain characteristic curve and is 0 [dB] shifts to the lower frequency side.

[0052] On the other hand, the phase characteristic curve is d-axis compensation value L d_est_compThe result does not change even when calculated as in equation (2). Furthermore, as mentioned above, the phase characteristic curve starts at a predetermined frequency lower than the peak frequency and decreases monotonically as the frequency increases above that frequency. Therefore, the phase margin in the phase characteristic curve is taken as the d-axis inductance, and the d-axis inductance value L d_est It can be increased beyond the value set to [value].

[0053] In particular, the d-axis compensation gain K is adjusted so that the gain at the peak frequency in the gain characteristic curve is lower than 0 [dB]. ω By setting this value to a lower value, motor control can be performed more stably.

[0054] In a coordinate space where the horizontal axis represents d-axis inductance and the vertical axis represents phase margin, the characteristic curve representing the relationship between d-axis inductance and phase margin is a curve in which the phase margin monotonically increases as the d-axis inductance decreases. On the other hand, as the rotational speed N increases, the characteristic curve shifts in the direction of decreasing phase margin. Therefore, consider the case where a straight line is drawn in the coordinate space such that the phase margin is a desired constant value (e.g., 40 [dB]). In this case, even when the rotational speed N changes, the d-axis compensation gain K shown in Figure 2 is used so that the d-axis inductance at which the characteristic curve intersects the straight line can be selected. ω Regarding this, the curve shape should be set for the region with a predetermined rotational speed N1 or higher.

[0055] [Control Flow] Figure 3 is a control flow diagram of the control device for the motor of the first embodiment. In step S101, the inductance estimation unit 3 refers to the table and the d-axis current command value i d * Based on this, the d-axis inductance value L d_est The q-axis current command value i is estimated. q * Based on the q-axis inductance value L q_est We estimate this.

[0056] In step S102, the compensation gain calculation unit 4 refers to a table and determines the d-axis compensation gain K for the d-axis inductance based on the rotational speed N. ω Calculate.

[0057] In step S103, the compensation gain calculation unit 4 calculates the q-axis inductance value L based on equation (2). q_est From the q-axis compensation value L q_est_comp In addition to calculating the d-axis compensation gain K ω Based on this, the d-axis inductance value L d_est From the d-axis compensation value L d_est_comp Calculate.

[0058] In step S104, the P control unit 5 controls the d-axis proportional gain K dp The P control d-axis voltage command value v is calculated based on equation (4) above. dp * The P control unit 5 calculates the q-axis proportional gain K. qp Calculate the P control q-axis voltage command value v based on equation (4). qp * Calculate.

[0059] In step S105, the I control unit 6 controls the d-axis integral gain K di The I control d axis voltage command value v is calculated based on equation (6) above. di * The control unit 6 calculates the q-axis integral gain K. qi The I control q axis voltage command value v is calculated based on equation (6). qi * Calculate.

[0060] In step S106, the adder / subtractor 7A controls the P control d-axis voltage command value v as shown in equation (7) above. dp * I control d axis voltage command value v di * d-axis interference voltage v d_dcpl * Based on this, the final d-axis voltage command value v d *The following is calculated. Similarly, the adder 7B calculates the P control q axis voltage command value v as shown in equation (8) above. qp * I control q axis voltage command value v qi * , and q-axis interference voltage v q_dcpl * Based on this, the final q-axis voltage command value v q * Calculate.

[0061] In step S107, the dq-axis / UVW phase conversion unit 8 sets the final d-axis voltage command value v d * and the final q-axis voltage command value v q * Based on equation (9) above, a pseudo three-phase AC voltage (v u ,v v ,v w Convert to ).

[0062] In step S108, the PWM conversion unit 9 sets the three-phase voltage command value (v u * ,v v * ,v w * ) is used as a drive signal (D) for PWM control of the inverter 10. uu * ,D ul * ,D vu * ,D vl * ,D wu * ,D wl * Convert to ).

[0063] [Second Embodiment] Figure 4 shows an example of the basic configuration of the control device for the electric motor according to the second embodiment. Figure 5 is a control flow diagram of the control device for the electric motor according to the second embodiment.

[0064] The control device for the electric motor in the second embodiment includes an estimated torque calculation unit 17 that estimates the torque T applied to the motor 18, and the compensation gain calculation unit 4 calculates the estimated torque T estBased on this, the q-axis compensation value L q_est_comp Calculate.

[0065] The control flow of the second embodiment is the same as that of the first embodiment in steps S101 and S104-S108, but as shown in Figure 5, steps S102A and S103A are executed after step S101, and then the process proceeds to step S104.

[0066] In step S102A, the estimated torque calculation unit 17 calculates the d-axis current value i output from the UVW axis / dq axis conversion unit 14. d and q-axis current value i q When input is received, the torque estimate T is calculated by referring to a pre-prepared table. est Outputs.

[0067] In step S103A, the compensation gain calculation unit 4 receives the d-axis inductance value L d_est q-axis inductance value L q_est , and torque estimate T est The following is input. The compensation gain calculation unit 4 calculates the torque estimate T est q-axis compensation gain K corresponding to T (See Figure 6) A table for calculating this is already available.

[0068] The compensation gain calculation unit 4 then calculates the d-axis inductance value L d_est q-axis inductance value L q_est When this is input, the d-axis compensation value L d_est_comp , and the q-axis compensation value L q_est_comp This is calculated as shown in equation (12) below.

number

[0069] Other components are the same as in the first embodiment.

[0070] Figure 6 shows the torque T and q-axis compensation gain K of the motor 18 in the second embodiment. TThis figure shows the relationship. Regarding the frequency characteristics (Bode plot) of the gain and phase of the control loop, the phase characteristic curve does not change with changes in the torque T applied to the motor 18. On the other hand, the gain characteristic curve shifts in the direction where the gain increases as the torque T increases. Therefore, the gain margin at the frequency where the phase is -180 [deg] decreases.

[0071] Therefore, in this embodiment, as shown in Figure 6, the q-axis compensation gain K increases as the torque T increases. T The setting is designed to minimize this. This suppresses the decrease in gain margin even when the torque T changes, and for example, the gain margin can be kept constant (e.g., 12 dB) even when the torque T changes.

[0072] In a coordinate space where the horizontal axis represents q-axis inductance and the vertical axis represents gain margin, the characteristic curve representing the relationship between q-axis inductance and gain margin is a curve in which the gain margin monotonically increases as the q-axis inductance decreases. On the other hand, as the torque T increases, the characteristic curve shifts in the direction of decreasing gain margin. Therefore, consider the case where a straight line is drawn in the coordinate space such that the gain margin is a desired constant value (e.g., 12 [dB]). In this case, even when the torque T changes, the q-axis inductance at which the characteristic curve intersects the straight line can be selected, and the q-axis compensation gain K shown in Figure 6 is used. T You just need to set the curve shape.

[0073] [Effects of this embodiment] According to the control method for the electric motor (motor 18) of this embodiment, the current command value (d-axis current command value i d * , q-axis current command value i q * ) based on the voltage command value (P control d axis voltage command value v dp * P control q axis voltage command value v qp * ) is calculated, and the voltage command value (P control d axis voltage command value v dp * P control q axis voltage command value vqp * The PWM signal (drive signal (D) is calculated based on ) uu * ,D ul * ,D vu * ,D vl * ,D wu * ,D wl * DC voltage V based on )) dc AC voltage (pseudo three-phase AC voltage (v u ,v v ,v w A control method for an electric motor (motor 18) that converts the current command value (d-axis current command value i) to output to the electric motor (motor 18), wherein the current command value (d-axis current command value i) is converted to a current command value (d-axis current command value i) and outputs to the electric motor (motor 18), and d * , q-axis current command value i q * ) and the dq-axis current value (d-axis current value i) obtained by converting the current flowing through the electric motor (motor 18) into a dq coordinate axis with reference to the phase angle of the rotor of the electric motor (motor 18). d q-axis current value i q The difference between ) and is the control gain (d-axis proportional gain K dp q-axis proportional gain K qp ) multiplied by the voltage command value (P control d axis voltage command value v dp * P control q axis voltage command value v qp * ) is calculated, and the control gain (d-axis proportional gain K) is calculated. dp q-axis proportional gain K qp ) is the inductance value (d-axis inductance value L) of the electric motor (motor 18). d_est q-axis inductance value L q_est ) to the inductance value (d-axis inductance value L d_est q-axis inductance value L q_est ) to adjust the compensation gain (d-axis compensation gain K ω q-axis compensation gain K T The compensation inductance value (d-axis compensation value L) obtained by multiplying by ) d_est_comp q-axis compensation value L q_est_comp Calculated based on ) and compensation gain (d-axis compensation gain Kω q-axis compensation gain K T The value of ) is set to 1 or less, and is set to decrease as the rotational speed N or torque T of the electric motor (motor 18) increases.

[0074] By the above method, current control can be performed while ensuring the desired stability in a predetermined operating range where control stability tends to be insufficient, namely the high torque range or high rotation range.

[0075] In this invention, the current command value (d-axis current command value i d * , q-axis current command value i q * ) is the q-axis current command value i, which is the q-axis component of the dq coordinate axes. q * Includes the dq axis current value (d axis current value i d q-axis current value i q ) is the q-axis component, i, which is the q-axis current value. q Includes voltage command value (P control d axis voltage command value v dp * P control q axis voltage command value v qp * ) is the q-axis component, which is the q-axis voltage command value (P control q-axis voltage command value v qp * ) includes the inductance value (d-axis inductance value L d_est q-axis inductance value L q_est ) is the q-axis inductance value L q_est Includes compensation gain (d-axis compensation gain K ω q-axis compensation gain K T ) is the q-axis compensation gain K T Includes the compensated inductance value (d-axis compensation value L d_est_comp q-axis compensation value L q_est_comp ) is the q-axis compensated inductance value (q-axis compensation value L q_est_comp ) includes control gain (d-axis proportional gain K dp q-axis proportional gain K qp ) is the q-axis inductance value L q_est q-axis compensation gain K T The q-axis compensation inductance value (q-axis compensation value L) obtained by multiplying by the value obtained by multiplying by the value Lq_est_comp The q-axis control gain (q-axis proportional gain K) calculated based on ) qp ) includes the q-axis voltage command value (P control q-axis voltage command value v qp * ) to the q-axis current command value i q * and q-axis current value i q The difference between this and the q-axis control gain (q-axis proportional gain K) qp Calculate by multiplying by ), and the q-axis compensation gain K T Set the value to 1 or less, and set it so that it decreases as the torque T increases.

[0076] By setting the q-axis inductance to decrease with increasing torque T using the method described above, the gain in the frequency band where the phase reaches -180 degrees in the Bode plot can be reduced, thereby securing the desired gain margin.

[0077] In this invention, the current command value (d-axis current command value i d * , q-axis current command value i q * ) is the d-axis component of the dq coordinate system, i, which is the d-axis current command value. d * Furthermore, it includes the voltage command value (P control d axis voltage command value v dp * P control q axis voltage command value v qp * ) is the d-axis component, the d-axis voltage command value (P control d-axis voltage command value v dp * ) further includes the q-axis inductance value L q_est The d-axis current command value i d * , q-axis current command value i q * d-axis voltage command value (P control d-axis voltage command value v dp * The calculated value is determined based on ) or set to a predetermined fixed value.

[0078] The above method ensures control performance (control accuracy and control stability) in the low torque range.

[0079] In this invention, the current command value (d-axis current command value i d * , q-axis current command value i q * ) is the d-axis component of the dq coordinate system, i, which is the d-axis current command value. d * Includes the dq axis current value (d axis current value i d q-axis current value i q ) is the d-axis component, i, which is the d-axis current value. d Includes voltage command value (P control d axis voltage command value v dp * P control q axis voltage command value v qp * ) is the d-axis component, the d-axis voltage command value (P control d-axis voltage command value v dp * ) includes the inductance value (d-axis inductance value L d_est q-axis inductance value L q_est ) is the d-axis inductance value L d_est Includes compensation gain (d-axis compensation gain K ω q-axis compensation gain K T ) is the d-axis compensation gain K ω Includes the compensated inductance value (d-axis compensation value L d_est_comp q-axis compensation value L q_est_comp ) is the d-axis compensating inductance value (d-axis compensation value L d_est_comp ) includes control gain (d-axis proportional gain K dp q-axis proportional gain K qp ) is the d-axis inductance value L d_est d-axis compensation gain K ω The d-axis compensation inductance value (d-axis compensation value L) obtained by multiplying by the value obtained by multiplying by the value L d_est_comp The d-axis control gain (d-axis proportional gain K) calculated based on ) dp ) includes the d-axis voltage command value (P control d-axis voltage command value v dp * ) to the d-axis current command value i d * and d-axis current value i d The difference between this and the d-axis control gain (d-axis proportional gain K) dp ) is multiplied to calculate the d-axis compensation gain K ωSet the value to 1 or less, and set it so that it decreases as the rotational speed N increases.

[0080] By setting the d-axis inductance to decrease with increasing rotational speed N using the method described above, the peak gain value generated on the high-frequency side of the Bode plot can be kept below 0 dB, thereby securing the desired phase margin.

[0081] In this invention, the current command value (d-axis current command value i d * , q-axis current command value i q * ) is the q-axis current command value i, which is the q-axis component of the dq coordinate axes. q * Furthermore, it includes the voltage command value (P control d axis voltage command value v dp * P control q axis voltage command value v qp * ) is the q-axis component, which is the q-axis voltage command value (P control q-axis voltage command value v qp * ) further includes the d-axis inductance value L d_est The d-axis current command value i d * , q-axis current command value i q * , q-axis voltage command value (P control q-axis voltage command value v qp * The calculated value is determined based on ), or set to a predetermined fixed value, and the d-axis compensation gain K ω This is set to 1 until the absolute value of the rotational speed N reaches a predetermined rotational speed N1, and then set to a value lower than 1 once it exceeds the predetermined rotational speed N1.

[0082] The above method ensures control performance (control accuracy and control stability) in the range where the rotational speed N is in the low to medium speed range.

[0083] In the above method, the predetermined rotational speed N1 is set such that the electrical angular period (period over which the electrical angle θ revolves) of the electric motor (motor 18) corresponding to the predetermined rotational speed N1 is equal to the voltage command value (P control d axis voltage command value v dp *P control q axis voltage command value v qp * The rotational speed N of the electric motor (motor 18) is set to approximately match the dead time of the control loop used to calculate the result.

[0084] By the above method, the d-axis compensation gain K is limited to the high-speed range where the effect of insufficient phase margin is significant, based on the current control period in the control loop. ω is the d-axis gain (d-axis proportional gain K dp This compensates for the loss of rotational speed N, thus ensuring control performance (control accuracy, control stability) in the low to medium speed range.

[0085] According to the control device for the electric motor (motor 18) of this embodiment, the current command value (d-axis current command value i d * , q-axis current command value i q * ) based on the voltage command value (P control d axis voltage command value v dp * P control q axis voltage command value v qp * ) is calculated, and the voltage command value (P control d axis voltage command value v dp * P control q axis voltage command value v qp * The PWM signal (drive signal (D) is calculated based on ) uu * ,D ul * ,D vu * ,D vl * ,D wu * ,D wl * DC voltage V based on )) dc AC voltage (pseudo three-phase AC voltage (v u ,v v ,v w A control device for an electric motor (motor 18) that converts the current command value (d-axis current command value i) to output to the electric motor (motor 18), wherein the current command value (d-axis current command value i) is converted to output to the electric motor (motor 18), and the control device for the electric motor (motor 18) is a control device for an electric motor (motor 18) that converts the current command value (d-axis current command value i) to output to the electric motor (motor d * , q-axis current command value i q *Based on this, the inductance value of the electric motor (motor 18) (d-axis inductance value L d_est q-axis inductance value L q_est An inductance estimation means (inductance estimation unit 3) that estimates the inductance value (d-axis inductance value L) and an inductance value (d-axis inductance value L d_est q-axis inductance value L q_est ) to the inductance value (d-axis inductance value L d_est q-axis inductance value L q_est ) to adjust the compensation gain (d-axis compensation gain K ω q-axis compensation gain K T Multiply by ) to obtain the compensation inductance value (d-axis compensation value L d_est_comp q-axis compensation value L q_est_comp A compensation gain calculation means (compensation gain calculation unit 4) that calculates the compensation inductance value (d-axis compensation value L d_est_comp q-axis compensation value L q_est_comp ) based on the voltage command value (P control d axis voltage command value v dp * P control q axis voltage command value v qp * ) to calculate the control gain (d-axis proportional gain K dp q-axis proportional gain K qp ) is calculated, and the current command value (d-axis current command value i d * , q-axis current command value i q * ) and the dq-axis current value (d-axis current value i) obtained by converting the current flowing through the electric motor (motor 18) into a dq coordinate axis with reference to the phase angle of the rotor of the electric motor (motor 18). d q-axis current value i q The difference between ) and is the control gain (d-axis proportional gain K dp q-axis proportional gain K qp ) multiplied by the voltage command value (P control d axis voltage command value v dp * P control q axis voltage command value v qp * The system includes a voltage command value generation means (P control unit 5) that calculates the compensation gain (d-axis compensation gain K), and a compensation gain calculation means (compensation gain calculation unit 4) that calculates the compensation gain (d-axis compensation gain K ω q-axis compensation gain K TSet it to a value of 1 or less, and set it so that it becomes smaller as the rotational speed N or torque T of the electric motor (motor 18) increases.

[0086] With the above configuration, in a predetermined operation region where control stability is likely to be insufficient, that is, in a high-torque region or a high-rotation region, current control can be performed while ensuring desired stability.

[0087] The present invention aims to adjust the compensation gain by focusing on the control signal in the high-rotation region or the high-torque region. Therefore, the signals used in the compensation gain calculation unit 4 shown in the embodiment are the rotational speed N and the torque estimated value T est is not limited thereto, and it is also possible to use a control signal that changes in accordance with the rotational speed N and torque T other than the above. Note that the torque estimated value T in FIG. 4 est As an alternative to, the same effect can be obtained by referring to the q-axis compensation gain K T based on the actual current value or the current command value.

[0088] As described above, the embodiments of the present invention have been described. However, the above embodiments merely show a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments. Also, the above embodiments can be combined as appropriate.

Explanation of Reference Numerals

[0089] 3 Inductance estimation unit, 4 Compensation gain calculation unit, 5 P control unit, 18 Motor

Claims

1. A method for controlling an electric motor, which involves calculating a voltage command value based on a current command value, and converting a DC voltage to an AC voltage based on a PWM signal calculated based on the voltage command value and outputting it to the motor, The voltage command value is calculated by multiplying the difference between the current command value and the dq-axis current value obtained by converting the current flowing through the motor into a dq coordinate axis with reference to the phase angle of the motor's rotor by the control gain. The control gain is calculated based on the compensated inductance value obtained by multiplying the inductance value of the electric motor by a compensation gain for adjusting the inductance value. The compensation gain is set to a value of 1 or less, and is set to decrease as the rotational speed or torque of the electric motor increases. The current command value includes a d-axis current command value which is the d-axis component of the dq coordinate axes, and a q-axis current command value which is the q-axis component of the dq coordinate axes. The dq-axis current value includes the d-axis current value which is the d-axis component. The voltage command value includes the d-axis voltage command value which is the d-axis component and the q-axis voltage command value which is the q-axis component. The inductance value includes the d-axis inductance value. The compensation gain includes the d-axis compensation gain, The aforementioned compensation inductance value includes the d-axis compensation inductance value. The d-axis inductance value is set to a calculated value obtained based on the d-axis current command value, the q-axis current command value, and the q-axis voltage command value, or to a predetermined fixed value. The control gain includes a d-axis control gain calculated based on the d-axis compensation inductance value obtained by multiplying the d-axis inductance value by the d-axis compensation gain. The d-axis voltage command value is calculated by multiplying the difference between the d-axis current command value and the d-axis current value by the d-axis control gain. The d-axis compensation gain is set to 1 until the absolute value of the rotational speed reaches a predetermined rotational speed, and then set to a value lower than 1 when the predetermined rotational speed is exceeded. A method for controlling an electric motor, wherein the predetermined rotational speed is set to the rotational speed of the electric motor at which the electrical angular period of the electric motor corresponding to the predetermined rotational speed substantially coincides with the dead time of the control loop used to calculate the voltage command value.

2. The dq-axis current value includes the q-axis current value which is the q-axis component, The inductance value includes the q-axis inductance value. The compensation gain includes the q-axis compensation gain. The aforementioned compensation inductance value includes the q-axis compensation inductance value. The control gain includes a q-axis control gain calculated based on the q-axis compensated inductance value obtained by multiplying the q-axis inductance value by the q-axis compensation gain. The q-axis voltage command value is calculated by multiplying the difference between the q-axis current command value and the q-axis current value by the q-axis control gain. The method for controlling an electric motor according to claim 1, wherein the q-axis compensation gain is set to a value of 1 or less, and is set to decrease as the torque increases.

3. The method for controlling an electric motor according to Claim 2, wherein the q-axis inductance value is set to a calculated value obtained based on the d-axis current command value, the q-axis current command value, and the d-axis voltage command value, or to a predetermined fixed value.

4. A motor control device that calculates a voltage command value based on a current command value, and converts a DC voltage to an AC voltage based on a PWM signal calculated based on the voltage command value and outputs it to the motor, An inductance estimation means for estimating the inductance value of the electric motor based on the current command value, A compensation gain calculation means calculates a compensated inductance value by multiplying the inductance value by a compensation gain for adjusting the inductance value, The system includes a voltage command value generation means that calculates a control gain for calculating the voltage command value based on the compensation inductance value, and calculates the voltage command value by multiplying the difference between the current command value and the dq-axis current value obtained by converting the current flowing through the motor into a dq coordinate axis with reference to the phase angle of the rotor of the motor by the control gain, The compensation gain calculation means is The compensation gain is set to a value of 1 or less, and is set to decrease as the rotational speed or torque of the electric motor increases. The current command value includes a d-axis current command value which is the d-axis component of the dq coordinate axes, and a q-axis current command value which is the q-axis component of the dq coordinate axes. The dq-axis current value includes the d-axis current value which is the d-axis component. The voltage command value includes the d-axis voltage command value which is the d-axis component and the q-axis voltage command value which is the q-axis component. The inductance value includes the d-axis inductance value. The compensation gain includes the d-axis compensation gain, The aforementioned compensation inductance value includes the d-axis compensation inductance value. The inductance estimation means sets the d-axis inductance value to a calculated value obtained based on the d-axis current command value, the q-axis current command value, and the q-axis voltage command value, or to a predetermined fixed value. The control gain includes a d-axis control gain calculated based on the d-axis compensation inductance value obtained by multiplying the d-axis inductance value by the d-axis compensation gain. The voltage command value generation means calculates the d-axis voltage command value by multiplying the difference between the d-axis current command value and the d-axis current value by the d-axis control gain. The compensation gain calculation means sets the d-axis compensation gain to 1 until the absolute value of the rotational speed reaches a predetermined rotational speed, and sets it to a value lower than 1 when the predetermined rotational speed is exceeded. A motor control device that sets the predetermined rotational speed to the rotational speed of the motor at which the electrical angular period of the motor corresponding to the predetermined rotational speed substantially coincides with the dead time of the control loop used to calculate the voltage command value.

Images