motor control device

Abstract

This invention provides a motor control device that achieves high-performance torque ripple suppression control through direct voltage control. It includes a voltage command arithmetic unit (15), which calculates the d-axis current command value (i) of the motor (6). d * ) and q-axis current command value (i q * To calculate the d-axis voltage command value (V) d ref ) and q-axis voltage command value (V q ref The feedforward command value calculation unit (23) calculates the q-axis voltage feedforward command value (V) based on the parameters of the spatial higher harmonics and the frequency characteristics of the motor windings to enable the q-axis current ripple to generate the q-axis voltage feedforward command value (V). qff * ); and the subtraction unit (10), which calculates the q-axis voltage command value (V) from the voltage command calculation unit (15). q ref The q-axis voltage feedforward command value (V) calculated by the arithmetic unit 23 is subtracted from the feedforward command value. qff * ).

Description

Technical Field

[0001] This invention relates to a control device for an electric motor. Background Technology

[0002] In the air conditioning compressors used in electric vehicles such as hybrid vehicles and electric vehicles, electric compressors powered by inverters and electric motors are increasingly being used. Because electric compressors used in vehicles need to be miniaturized, there is a tendency for an increase in the proportion of spatial higher harmonic distortion. These spatial higher harmonics contribute to electromagnetic noise caused by current ripple, torque ripple, and radial excitation forces. Therefore, the need for filters and vibration suppression components increases, hindering miniaturization.

[0003] On the other hand, due to mechanical limitations, installing encoders is generally difficult in electric compressors, thus sensorless vector control is used. However, in this sensorless vector control, increasing the current control bandwidth is challenging due to structural issues. Specifically, controlling high-frequency spatial harmonic distortion is not easy.

[0004] For example, in Patent Document 1, information on spatial higher harmonics is used to cause the torque command value of the motor current to vary at high frequencies, thereby suppressing torque ripple. Furthermore, in Patent Document 2, the difference between the detected higher harmonic components of the motor current and their command values ​​is calculated, and feedback control is performed to output a higher harmonic voltage command value. By adding this value to the three-phase voltage command values, the torque ripple of the motor is reduced.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 5262267

[0008] Patent Document 2: Japanese Patent No. 4019842 Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] However, in Patent Document 1, the current control system needs to be set to have a sufficiently high bandwidth relative to the motor speed. In cases where the motor is driven at high speeds, such as an electric compressor, the bandwidth of the current control system becomes too high. Patent Document 2 takes this into account and implements feedback control that only improves the responsiveness of higher harmonic characteristics, but still directly performs PI control on the phase characteristics of the detected actual current.

[0011] However, in reality, there is a phase difference between the current and voltage being controlled, and therefore, this phase difference needs to be considered for voltage control. Therefore, in Patent Document 2, the feedback control bandwidth is reduced, allowing time for the result to converge, so that the PI-dhqh current controller does not operate unstablely. That is, the responsiveness needs to be slowed down, resulting in the following problems: it takes time for the reduced control effect, such as generating torque ripple, to occur, and sometimes convergence is not achieved.

[0012] This invention was made to solve the problems of the prior art, and its purpose is to provide a motor control device that can perform torque ripple suppression control with high following performance by performing direct voltage control.

[0013] Technical means for solving technical problems

[0014] The electric motor control device of the present invention is characterized by comprising: a voltage command calculation unit, which calculates the voltage command based on the d-axis current command value i of the electric motor. d * and q-axis current command value i q * To calculate the d-axis voltage command value V d ref and q-axis voltage command value V q ref The feedforward command value calculation unit calculates the q-axis voltage feedforward command value V based on the parameters of the spatial higher harmonics and the frequency characteristics of the motor windings, to enable the q-axis current ripple to generate the q-axis voltage feedforward command value V. qff * ; and a subtraction unit, which calculates the q-axis voltage command value V from the voltage command arithmetic unit. q ref The q-axis voltage feedforward command value V calculated by the arithmetic unit after subtracting the feedforward command value is... qff * The motor control device compensates for torque ripple caused by spatial high-order harmonics.

[0015] The motor control device of claim 2 is characterized in that, in the above invention, the motor is a three-phase permanent magnet synchronous motor, and the feedforward command value calculation unit calculates the q-axis voltage feedforward command value V for electrical angles 6n times (n is a positive integer). qff * .

[0016] The motor control device of claim 3 is characterized in that, in the aforementioned inventions, the feedforward command value calculation unit calculates the q-axis voltage feedforward command value V based on the spatial higher harmonic value after advancing the phase based on the motor impedance relative to the electrical angle estimation value. qff * .

[0017] The motor control device of claim 4 is characterized in that, in the aforementioned inventions, the feedforward command value calculation unit calculates the q-axis voltage feedforward command value V by multiplying the gain based on the motor impedance by the spatial higher harmonics. qff * .

[0018] The electric motor control device of claim 5 is characterized in that, in the above-described inventions, the electric motor is a three-phase permanent magnet synchronous motor, and the estimated value of the q-axis current of the motor is set to i. q (^), Set the 6th harmonic flux along the q-axis to k 6hq Set the estimated electrical angle value as θ re (^), Set the amplitude of the first component of the armature linkage flux as Set the winding resistance to R and the q-axis winding inductance to L. q Set the electrical angular velocity as ω re hour,

[0019] [Mathematical Expression 1]

[0020]

[0021] The feedforward command value calculation unit uses the above formula (3) to calculate the q-axis voltage feedforward command value V of the sixth electrical angle. qff * .

[0022] The motor control device of claim 6 is characterized in that, in the above-described inventions, the feedforward command value calculation unit further includes an adder, which further calculates the q-axis voltage feedforward command value V. qff * The resulting q-axis current ripple interferes with the d-axis, which is the d-axis voltage feedforward command value V. dff * And the d-axis voltage feedforward command value V calculated by the feedforward command value calculation unit dff * The d-axis voltage command value V calculated by the voltage command arithmetic unit d ref Add them together.

[0023] The electric motor control device of claim 7 is characterized in that, in the above invention, the electric motor is a three-phase permanent magnet synchronous motor, and the estimated value of the q-axis current of the motor is set to i. q (^), Set the 6th harmonic flux along the q-axis to k 6hq Set the estimated electrical angle value as θ re (^), Set the amplitude of the first component of the armature linkage flux as Set the q-axis winding inductance to Lq Set the electrical angular velocity as ω re hour,

[0024] [Mathematical Expression 2]

[0025]

[0026] The feedforward command value calculation unit uses the above formula (4) to calculate the d-axis voltage feedforward command value V of the sixth electrical angle. dff * .

[0027] The motor control device of claim 8 is characterized in that, in the invention of claim 6 or claim 7, the motor is a three-phase permanent magnet synchronous motor and includes: an inverter circuit that drives the motor; and a phase voltage command calculation unit that calculates the phase voltage command value V from the q-axis voltage command value. q ref Subtract the q-axis voltage feedforward command value V from the middle qff * The subsequent q-axis voltage command value V q * and the d-axis voltage command value V d ref Add d-axis voltage feedforward command value V dff * The subsequent d-axis voltage command value V d * The voltage is converted into a three-phase modulation voltage command value; and a PWM signal generation unit generates a PWM signal for PWM control of the inverter circuit based on the three-phase modulation voltage command value.

[0028] Invention Effects

[0029] The motor control device of the present invention includes: a voltage command calculation unit, which calculates the voltage command based on the d-axis current command value i of the motor. d * and q-axis current command value i q * To calculate the d-axis voltage command value V d ref and q-axis voltage command value V q ref The feedforward command value calculation unit calculates the q-axis voltage feedforward command value V based on the parameters of the spatial higher harmonics and the frequency characteristics of the motor windings, to enable the q-axis current ripple to generate the q-axis voltage feedforward command value V. qff * ; and a subtraction unit, which calculates the q-axis voltage command value V from the voltage command arithmetic unit. q refThe q-axis voltage feedforward command value V calculated by the arithmetic unit after subtracting the feedforward command value is... qff * The motor control device compensates for torque ripple caused by spatial high-order harmonics.

[0030] The q-axis voltage feedforward command value V calculated by the aforementioned feedforward command value calculation unit qff * This is a voltage command value used to generate torque ripple caused by higher harmonics in space. In this invention, the voltage command value V is obtained from the q-axis voltage command value in the subtraction section. q ref This can be directly subtracted. That is, according to the present invention, torque ripple can be canceled or suppressed by the voltage feedforward control involved, without being limited by the current control bandwidth. As a result, the vibration of electromagnetic energy caused by higher harmonics in space can be eliminated or suppressed, and thus, electromagnetic noise can be reduced.

[0031] Specifically, when the motor is a three-phase permanent magnet synchronous motor, spatial higher harmonics are excited at multiples of 6, i.e., electrical angle 6n. Therefore, if, as in the invention of claim 2, the feedforward command value calculation unit calculates the q-axis voltage feedforward command value V at electrical angle 6n (n is a positive integer),... qff * This can effectively reduce torque ripple.

[0032] Here, the phase of the current is delayed based on the motor's impedance relative to the voltage. This delayed phase varies depending on the motor's driving conditions, and the delayed phase of the motor impedance differs with frequency; therefore, it is necessary to make the delayed phase variable at each frequency. Thus, as in the invention of claim 3, if the feedforward command value calculation unit calculates the q-axis voltage feedforward command value V based on the spatial higher harmonic values ​​after advancing the phase based on the motor impedance relative to the electrical angle estimation value... qff * Then, compensation in the voltage dimension can be performed without any obstacles.

[0033] Furthermore, the frequency of spatial higher harmonics varies depending on the motor's driving conditions, and similarly to the delay phase, the attenuation coefficient varies with frequency. Therefore, it is necessary to feed forward the q-axis voltage command value V. qff * The amplitude is variable at each frequency. Therefore, as in the invention of claim 4, if the feedforward command value calculation unit calculates the q-axis voltage feedforward command value V by multiplying the gain based on the motor impedance by the spatial higher harmonics... qff * Then, the torque ripple of spatial high-order harmonics can be appropriately compensated according to the driving conditions of the motor.

[0034] Here, when the motor is a three-phase permanent magnet synchronous motor, it becomes the main component of the spatial higher harmonic torque ripple at the 6th electrical angle. Therefore, for example, as in the invention of claim 5, if the feedforward command value calculation unit uses the above formula (3) to calculate the q-axis voltage feedforward command value V at the 6th electrical angle... qff * This can effectively reduce torque ripple.

[0035] Furthermore, a phenomenon known as velocity electromotive force exists in electric motors where there is mutual interference between the d and q axes. As described in the invention above, if the q-axis voltage command value V... q ref Subtract the q-axis voltage feedforward command value V from the middle qff * This causes q-axis current ripple, which in turn interferes with the d-axis, generating ripple in the d-axis current and in the reluctance torque.

[0036] Therefore, as in the invention of claim 6, the feedforward command value calculation unit is further provided with an adder, which further calculates the q-axis voltage feedforward command value V. qff * The resulting q-axis current ripple interferes with the d-axis, which is the d-axis voltage feedforward command value V. dff * Furthermore, the d-axis voltage feedforward command value V calculated by the feedforward command value calculation unit is... dff * The d-axis voltage command value V calculated by the voltage command arithmetic unit d ref By adding them together, the q-axis voltage feedforward command value V can be suppressed. qff * This results in the excitation of reluctance torque.

[0037] Specifically, as in the invention of claim 7, the feedforward command value calculation unit uses the above formula (4) to calculate the d-axis voltage feedforward command value V of electrical angle 6. dff * Therefore, the q-axis voltage feedforward command value V, which is 6 times the electrical angle, can be effectively suppressed. qff * This results in the excitation of reluctance torque.

[0038] Furthermore, as in claim 8, each of the above inventions also includes: an inverter circuit that drives a three-phase permanent magnet synchronous motor; and a phase voltage command calculation unit that calculates the phase voltage command value V from the q-axis voltage command value. q ref Subtract the q-axis voltage feedforward command value V from the middle qff * The subsequent q-axis voltage command value Vq * and the d-axis voltage command value V d ref Add d-axis voltage feedforward command value V dff * The subsequent d-axis voltage command value V d * The system converts the three-phase modulation voltage command value into a three-phase modulation voltage command value; and a PWM signal generation unit generates a PWM signal for PWM control of the inverter circuit based on the three-phase modulation voltage command value, thereby constituting a motor control device. This provides a motor control device that effectively reduces electromagnetic noise. Attached Figure Description

[0039] Figure 1 This is a system structure diagram of a motor control device that applies an embodiment of the present invention.

[0040] Figure 2 It is shown Figure 1 A diagram of the rotor flux waveform of an electric motor.

[0041] Figure 3 It is shown Figure 1 A diagram illustrating an embodiment of the driving conditions.

[0042] Figure 4 This is a diagram showing the dq axis current and motor torque involved in the motor control device of the embodiment.

[0043] Figure 5 This is a graph showing the dq-axis current, motor torque, and reluctance torque without implementing the existing method of the present invention.

[0044] Figure 6 This is a graph showing the dq-axis current, motor torque, and reluctance torque when implementing q-axis voltage feedforward control in the embodiment.

[0045] Figure 7 The diagram shows the dq-axis current, motor torque, and reluctance torque when implementing q-axis voltage feedforward control and d-axis voltage feedforward control in the embodiment.

[0046] Figure 8 It is shown Figure 7 The figure shows the FFT analysis results of the motor torque under the given conditions.

[0047] Figure 9 Yes Figures 5 to 7 The graph compares the torque ripple under different conditions. Detailed Implementation

[0048] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0049] (1) Motor control device 1

[0050] Figure 1 This is a system structure diagram of a motor control device 1 according to an embodiment of the present invention. The motor control device 1 of this embodiment is configured to include an inverter circuit 2 and a control unit 3, which converts the DC power supplied from a DC power source 4, such as a vehicle battery, into AC power of a predetermined frequency and supplies it to the motor 6. The motor 6 in this embodiment is a three-phase permanent magnet synchronous motor (IPMSM) that drives the electric compressor used in the air conditioning system of electric vehicles such as electric cars and hybrid vehicles, and is driven by voltage commands generated by the control unit 3.

[0051] (2) Inverter circuit 2

[0052] Inverter circuit 2 is configured such that its input node is connected to DC power supply 4, switches the output of DC power supply 4 to convert it into three-phase AC voltage, and supplies it to the motor (IPMSM) 6. In this embodiment, inverter circuit 2 is configured by bridging multiple (6) switching elements.

[0053] (3) Control Unit 3

[0054] The control unit 3 is based on the estimated mechanical angular velocity ω of the electric motor 6. rm (^) and the mechanical angular velocity command value ω rm * The deviation is used to generate the d-axis voltage command value Vd. * q-axis voltage command value Vq * Based on these d-axis voltage command values ​​Vd * q-axis voltage command value Vq * This generates PWM signals that are ultimately used to switch the various switching elements of the inverter circuit 2, and drives the motor 6 through sensorless vector control.

[0055] The control unit 3 in the embodiment consists of subtraction units 7-10, adder 11, speed controller 12, current controller 13, non-interference controller 14, phase voltage command calculation unit 16, PWM signal generation unit 17, uvw-dq converter 18, electrical angular velocity estimator 19, integrator 21, electrical angle-to-mechanical angle converter 22, and feedforward command value calculation unit 23, which is the subject of this invention.

[0056] U-phase current i of motor 6 u and W phase current i w The inputs are fed into the uvw-dq converter 18 of the embodiment, and the V-phase current i is calculated based on them. vThe estimated electrical angle θ output by integrator 21 re (^) is further input to the uvw-dq converter 18, and based on the U-phase current i u Phase V current i v Phase W current i w and the estimated value of the electrical angle θ re (^) is used to derive the estimated d-axis current value i d (^) and the estimated q-axis current i q (^).

[0057] The electrical angular velocity estimator 19 estimates the d-axis current value i based on the output of the UVW-DQ converter 18. d (^), Estimated q-axis current i q (^), The d-axis voltage command value V output by the non-interference controller 14 d ref and q-axis voltage command value V q ref To derive the estimated electrical angular velocity ω re (^) and output. The estimated electrical angular velocity ω re (^) is input to integrator 21, which estimates the electrical angular velocity ω. re (^) is used to generate the estimated electrical angle θ. re (^) and output.

[0058] The estimated electrical angular velocity ω output by the electrical angular velocity estimator 19 re (^) is further input to the electrical angle-to-mechanical angle converter, and the electrical angle-to-mechanical angle converter 22 estimates the electrical angular velocity ω. re (^) is converted to the estimated mechanical angular velocity ω. rm (^) and output. The estimated mechanical angular velocity ω rm (^) is input into subtraction unit 7. Mechanical angular velocity command value ω rm * The data is further input to the subtraction unit 7, where the mechanical angular velocity command value ω is calculated. rm * Subtract the estimated mechanical angular velocity ω from the middle rm (^) is used to calculate their deviation.

[0059] The deviation calculated by the subtraction unit 7 is input to the speed control unit 12. The speed control unit 12 calculates the q-axis current command value i using PI calculation and the relationship between q-axis current and torque. q * The speed controller 12 calculates the q-axis current command value i. q * The estimated q-axis current value i calculated by the UVW-DQ converter 18q (^) is input to the subtraction unit 9, and the subtraction unit 9 extracts the q-axis current command value i q * Subtract the estimated q-axis current i q (^) is used to calculate their deviation.

[0060] On the other hand, the d-axis current command value i d * The estimated d-axis current value i calculated by the UVW-DQ converter 18 d (^) is input to the subtraction unit 8, and the subtraction unit 8 obtains the d-axis current command value i d * Subtract the estimated d-axis current i d (^) is used to calculate their deviation.

[0061] Here, the aforementioned current controller 13 and non-interference controller 14 constitute the voltage command calculation unit 15 in this invention. This voltage command calculation unit 15 uses the deviations output by each of the subtraction units 8 and 9, performs PI calculations using the current controller 13, and uses the non-interference controller 14 to cancel interference between the d and q axes, thereby generating the d-axis voltage command value V. d ref and q-axis voltage command value V q ref And output. Furthermore, the non-interference controller 14 pre-applies the command value with the generator voltage (interference voltage) of the motor 6 to achieve non-interference control. Basically, in the voltage command calculation unit 15, the d-axis current command value id* and the q-axis current estimate value i are calculated. d The deviation between (^) and the q-axis current command value i q * With the estimated value of q-axis current i q The d-axis voltage command value V in the direction of eliminating the deviation between (^) is... d ref and q-axis voltage command value V q ref .

[0062] The voltage command calculation unit 15 calculates the d-axis voltage command value V. d ref The input is fed into the addition unit 11. The feedforward command value V output by the feedforward command value calculation unit 23 is the d-axis voltage feedforward command value. dff * The input is fed into the adder 11, which then feeds forward the d-axis voltage command value V. dff * With d-axis voltage command value V d ref The sums are used as the compensated d-axis voltage command value V. d* To output (V) d * =V d ref +V dff * ).

[0063] In addition, the voltage command calculation unit 15 calculates the d-axis voltage command value V. d ref The input is given to the subtraction unit 10. The feedforward command value V, output by the feedforward command value calculation unit 23, is the q-axis voltage feedforward command value. qff The input is given to the subtraction unit 10, which then extracts the q-axis voltage command value V. q ref Subtract the q-axis voltage feedforward command value V from the middle qff * and used as the compensated q-axis voltage command value V q * to output (V) q * = V q ref -V qff Furthermore, the operation of the aforementioned feedforward instruction value calculation unit 23 will be explained in detail later.

[0064] These compensated d-axis voltage command values ​​V d * and q-axis voltage command value V q *The electrical angle estimation value θ is input to the phase voltage command arithmetic unit 16 and output by the integrator 21. re (^) is input to the phase voltage command calculation unit 16. Then, the phase voltage command calculation unit 16 calculates the d-axis voltage command value V. d * q-axis voltage command value V q *Convert to the three-phase modulation voltage command value, i.e., the U-phase voltage command value V u Phase V voltage command value V v and the W-phase voltage command value V w The PWM signal generator 17 generates the signal based on these U-phase voltage command values ​​V. u Phase V voltage command value V v and the W-phase voltage command value V w This generates PWM signals for switching (PWM control) the various switching elements of inverter circuit 2. This enables sensorless vector control of motor 6.

[0065] (4) Operation of the feedforward instruction value calculation unit 23

[0066] Next, the operation of the feedforward command value calculation unit 23 of the control unit 3 will be explained. The motor control device 1 of the present invention uses sensorless vector control to suppress high-order harmonic electromagnetic distortion, thereby reducing torque ripple. However, in order to suppress this torque ripple, it operates such that a torque ripple in opposite phase is generated at the same frequency as the ripple component.

[0067] (4-1) q-axis voltage feedforward control

[0068] First, the q-axis voltage feedforward control executed by the feedforward command value calculation unit 23 will be explained. First, the torque formula of the motor (IPMSM) 6 of the embodiment is shown in equation (1).

[0069] [Mathematical Expression 3]

[0070] T m =Pφ f i q +P(L d -L q )i d i q +Pi q k hq +Pi d k hd (1)

[0071] Among them, T m Motor torque [Nm], where P is the number of pole pairs. It is the amplitude [Wb] of the first component of the armature linkage flux, k hd It is the d-axis higher harmonic flux [Wb], k hq It is the q-axis higher harmonic flux [Wb], i d It is the d-axis current [A], i q It is the q-axis current [A], L d It is the d-axis winding inductance [H], L q It is the q-axis winding inductance [H].

[0072] In equation (1) above, the first term is the magnet torque, the second term is the reluctance torque, the third term is the torque ripple caused by the q-axis current and spatial harmonics, and the fourth term is the torque ripple caused by the d-axis current and spatial harmonics. The spatial harmonics k of the magnetic flux... hd k hq It is represented by equation (2). Furthermore, equation (2) is a formula for representing the spatial higher harmonic components of the magnetic flux. Since the spatial higher harmonics in the motor (IPMSM) 6 have multiples of 6, the 6th and 12th harmonics are extracted in equation (2).

[0073] [Mathematical Expression 4]

[0074]

[0075] Where, k 6hd It is the 6th harmonic flux [Wb] along the d-axis, k 6hq It is the 6th harmonic flux [Wb] along the q-axis, k 12hd It is the 12th harmonic flux [Wb] along the d-axis, k 12hq It is the 12th harmonic flux [Wb] along the q-axis, ψ sn It is the sinusoidal component of the nth harmonic [Wb], ψ cn It is the cosine component of the nth harmonic [Wb], θ re It is the electrical angle [rad / s].

[0076] The spatial harmonics of magnetic flux are functions of the electrical angle; therefore, the motor torque becomes a function of current and electrical angle. Figure 2 The figure shows the magnetic flux waveform of the rotor. Figure 2 The solid lines in the upper column represent the magnetic flux waveform of the U phase, the thick dashed lines represent the magnetic flux waveform of the V phase, and the thin dashed lines represent the magnetic flux waveform of the W phase. The dashed lines in the lower column represent the magnetic flux waveform of the d-axis, and the solid lines represent the magnetic flux waveform of the q-axis.

[0077] Due to the point symmetry of its waveform, the rotor flux containing spatial higher harmonics cannot excite even-order higher harmonics. Furthermore, there is no 3n-order higher harmonic component in a three-phase connection; therefore, the higher harmonic components of the rotor flux become 6n ± 1 components. In the experiment, it is known that the IPMSM6 has 6 ± 1 and 12 ± 1 higher harmonic components as principal components. If a coordinate transformation is performed on the dq axis, the 6 ± 1 becomes the 6th harmonic, and the 12 ± 1 becomes the 12th harmonic.

[0078] Therefore, the feedforward command value calculation unit 23 of the embodiment calculates the 6th order q-axis voltage feedforward command value V, which becomes the principal component of the torque ripple, as described later. qff * And output. Here, according to the above equations (1) and (2), it can be seen that the frequency of the torque ripple depends on the electrical angle and the amplitude depends on the current. When the torque ripple is compensated by current control, the current control frequency band needs to be set to a frequency band that can fully follow the 6th order frequency of the electrical angle. However, the sensorless vector control includes phase estimation, so it is difficult to improve the current control frequency band.

[0079] To address this issue, the feedforward command value calculation unit 23 calculates and directly outputs a voltage command value that cancels out the torque ripple caused by higher harmonics in the space, thereby performing torque ripple compensation in sensorless vector control. In this case, the feedforward command value calculation unit 23 in this embodiment uses equation (3) to calculate the q-axis voltage feedforward command value V. qff *Then, the subtraction unit 10 feeds forward the q-axis voltage command value V. qff * From the q-axis voltage command value V q ref Subtract from the middle. This is q-axis voltage feedforward control.

[0080] [Mathematical Expression 5]

[0081]

[0082] Among them, i q (^) is the estimated value of the q-axis current, k 6hq It is the 6th harmonic flux along the q-axis, θ re (^) is the estimated value of the electrical angle. R is the amplitude of the first component of the armature linkage flux, R is the winding resistance, and L is the amplitude of the first component of the armature linkage flux. q It is the q-axis winding inductance, ω re It is electrical angular velocity.

[0083] That is, as can be seen from the above equation (3), the q-axis voltage feedforward command value V qff * The q-axis voltage feedforward command value V is calculated based on the parameters of spatial higher harmonics and the frequency characteristics of the motor windings. qff * It is the value that generates 6 q-axis current ripples.

[0084] When torque ripple is compensated by current control, the torque is a function of the current; therefore, the phase of the torque ripple is in phase with the phase of the ripple superimposed on the current. On the other hand, when torque ripple is compensated in the voltage dimension, the stator winding is equivalent to the LR circuit; therefore, the motor current has a phase delay relative to the applied voltage and exhibits attenuation characteristics relative to higher harmonics.

[0085] Therefore, as in this invention, in voltage-dimensional compensation, the phase delay and amplitude attenuation in the LR circuit need to be considered. In the first-order delay circuit of LR, the current has a phase delay relative to the voltage. Therefore, in the q-axis voltage feedforward control, the spatial higher harmonic value after advancing the phase based on the impedance of motor 6 relative to the electrical angle estimate of the spatial higher harmonic in equation (2) is used, where k in equation (3) is... 6hq The values ​​in parentheses following it represent the higher harmonic values ​​of that space, tan -1 The term corresponds to the phase advancing based on the impedance of motor 6. Here, in the medium-to-high speed domain, tan -1 The term can be approximated as π / 2. Therefore, in the embodiment, tan in equation (3) is used. -1 The term is considered as π / 2.

[0086] Furthermore, the frequency of the 6th electrical angle varies depending on the driving conditions of the motor 6. Since the attenuation coefficient differs with frequency, the q-axis voltage feedforward command value V needs to be adjusted. qff The amplitude of * is variable at each frequency. In the embodiment, the stator is equivalent to the LR circuit, therefore, the gain is multiplied by the impedance of the motor 6, taking into account the gain characteristics of the first delay system of LR. The square root term in Equation (3) corresponds to this gain, thus amplifying the amplitude by an amount equivalent to the attenuated amplitude.

[0087] The following uses a mathematical formula to describe the q-axis voltage feedforward command value V as explained above. qff The meaning of * will be explained in detail. In the above equation (3), the 6th harmonic flux k along the q-axis... 6hq It is the electrical angle θ re The function of . In the above equation (1), the d-axis current is stably controlled at 0A, so the torque ripple caused by the d-axis current and the higher harmonics of the magnetic flux is not considered. In addition, the main component of the higher harmonics of the magnetic flux is the 6th electrical angle component. Therefore, if the 12th harmonic component is ignored, equation (1) becomes the following equation (3A).

[0088] [Mathematical Expression 6]

[0089] T m =Pφ f i q +Pi q k 6hq (6θ re (3A)

[0090] Here, if we define the motor torque without ripple as T... mDC And set the ripple component of the motor torque as T mrip Then they can be represented by the following formula (3B).

[0091] [Mathematical Expression 7]

[0092] T mDC +T mrip =Pφ f i q +Pi q k 6hq (6θ re (3B)

[0093] If we consider the q-axis current component i from which the torque ripple of equation (3B) is controlled to zero. qrip Subtract i from the middle q Then equation (3B) becomes equation (3C) as follows.

[0094] [Mathematical Expression 8]

[0095]

[0096] Here, the motor torque T excluding ripple is... mDC Depend on To control this, the two are equal. Furthermore, if T is set to zero to reduce torque ripple... mrip =0, then i qrip * It becomes like the following formula (3D).

[0097] [Mathematical Expression 9]

[0098]

[0099] here, Therefore, equation (3D) can be set as shown in equation (3E).

[0100] [Mathematical Expression 10]

[0101]

[0102] By subtracting equation (3E) from the q-axis current command value, torque ripple of the 6th order of the electrical angle caused by higher spatial harmonics can be suppressed. However, when given by the q-axis current command, a high-speed current controller that follows the frequency of the torque ripple is required. In sensorless vector control systems, the bandwidth of the current controller is limited, making it difficult to construct a high-speed current controller. Therefore, in order to suppress torque ripple in the voltage dimension, it is necessary to reduce the frequency of the q-axis current command to 6E. qrip * Convert to voltage command value.

[0103] In this case, the motor windings are represented by an LR circuit, therefore, the voltage and current have phase and gain characteristics at each frequency. To compensate in the voltage dimension, a voltage compensation value needs to be calculated, taking into account the phase and gain characteristics of the motor windings. The phase characteristics of the motor windings are shown in the following equation (3F).

[0104] [Mathematical Expression 11]

[0105]

[0106] Furthermore, the gain characteristics of the motor windings are shown in the following formula (3G).

[0107] [Mathematical Expression 12]

[0108]

[0109] Considering equations (3F) and (3G) above, by implementing forward phase compensation equivalent to the phase delay and amplifying the amplitude equivalent to the attenuated amplitude, a q-axis voltage feedforward command value V in response to the desired current can be obtained.qff * q-axis voltage feedforward command value V qff * Output in the following formula (3H).

[0110] [Mathematical Expression 13]

[0111]

[0112] In sensorless vector control, when equation (3H) is applied, the q-axis current and electrical angle become assumed values. Furthermore, for the electrical angular velocity, when the speed controller operates stably and is in a stable state, the speed command value can be used instead of the assumed value. Therefore, equation (3H) becomes equation (3) above.

[0113] Furthermore, in the medium-to-high speed domain, tan in equation (3) -1 The terms with the square root can also be approximated as π / 2 and 6ω, respectively. re L q Therefore, equation (3) can also be expressed by the following equation (3I).

[0114] [Mathematical Expression 14]

[0115]

[0116] Therefore, the q-axis voltage feedforward command value V calculated by the feedforward command value calculation unit 23 qff * In the subtraction section 10 described above, the q-axis voltage command value V is obtained. q ref The value is subtracted from the middle value and used as the compensated q-axis voltage command value V. q * The torque ripple of the sixth electrical angle caused by the higher harmonics of space, along with the torque ripple of the opposite phase, is output as the magnet torque, and the torque ripple is canceled out.

[0117] (4-2) d-axis voltage feedforward control

[0118] On the other hand, in the IPMSM6 motor, there exists a phenomenon called velocity electromotive force that causes mutual interference between the d and q axes, and the current flowing through each axis appears as an interference component in the other axis. In order to independently control the current of each axis, Figure 1 The non-interference controller 14 performs non-interference control by pre-applying a voltage command value to cancel the amount of interference voltage as described above. However, as mentioned above, if a feedforward voltage is applied to the q-axis voltage through q-axis voltage feedforward control and a q-axis current ripple is generated, the q-axis current ripple will interfere with the d-axis, thereby generating ripple in the d-axis current and in the reluctance torque.

[0119] In order to suppress or eliminate this, the feedforward command value calculation unit 23 of the embodiment performs d-axis voltage feedforward control as described below, and calculates the d-axis voltage feedforward command value V. dff * And output, and through adder 11 and the d-axis voltage command value V d ref Add them together. Here, the q-axis current ripple interferes with the d-axis in the voltage dimension; therefore, the phase of the d-axis current ripple caused by the q-axis current ripple is delayed by π / 2 phase relative to the q-axis current. Therefore, the d-axis voltage feedforward command value V... dff * The phase of the current is in phase with the ripple phase of the q-axis current.

[0120] The feedforward command value calculation unit 23 in the embodiment uses equation (4) to calculate the d-axis voltage feedforward command value V. dff * .

[0121] [Mathematical Expression 15]

[0122]

[0123] Among them, i q (^) is the estimated value of the q-axis current, k 6hq It is the 6th harmonic flux along the q-axis, θ re (^) is the estimated value of the electrical angle. It is the amplitude of the first component of the armature linkage flux, L q It is the q-axis winding inductance, ω re This refers to the electrical angular velocity. In sensorless vector control, the q-axis current and electrical angle are assumed values. For the electrical angular velocity, when the speed control operates stably and is in a steady state, the speed command value can be used instead of the assumed value.

[0124] That is, as can be seen from the above equation (4), the d-axis voltage feedforward command value V dff * represents the interference term that causes the q-axis current ripple generated by the q-axis voltage feedforward control to interfere with the d-axis. It is derived from the current superimposed on the q-axis current. Since the interference term is in the voltage dimension, there is no need for phase-advancing processing as required in the case of q-axis voltage feedforward control.

[0125] The mathematical formula is used to describe the d-axis voltage feedforward command value V as explained above. dff The meaning of * will be explained in detail. According to the above equation (3), when a certain ripple component flows through the q-axis current, due to the aforementioned inter-axis interference, the ripple component appears as an interference voltage on the d-axis. The ripple component appearing as an interference voltage excites ripple in the d-axis current. This ripple component also appears in the reluctance torque. That is, due to the q-axis voltage feedforward control, as a reluctance torque, an unexpected ripple is excited.

[0126] To suppress the ripple of the reluctance torque, the q-axis voltage feedforward command value V... qff * This requires the same non-interference processing as the non-interference controller 14. The interference voltage E of the q-axis current on the d-axis. d It can be represented by the following formula (4A).

[0127] [Mathematical Expression 16]

[0128] E d =-i q L q ω re (4A)

[0129] The q-axis voltage feedforward command value V in equation (3) qff *From q-axis voltage command value V q ref The value of V is subtracted from the value and used as the compensated q-axis voltage command value. q * is output; therefore, the current flowing through the q-axis through q-axis voltage feedforward control is obtained by reversing the sign of equation (3E). Therefore, the interference voltage E d It is represented by the following formula (4B).

[0130] [Mathematical Expression 17]

[0131]

[0132] The interference voltage shown in equation (4B) is pre-combined with the d-axis voltage command value V. d ref Add them together and set them as the compensated d-axis voltage command value V. d * This enables q-axis voltage feedforward control and d-axis non-interference control. In sensorless vector control, the q-axis current and electrical angle become estimated values. Furthermore, for the electrical angular velocity, when the speed controller operates stably and is in a stable state, the speed command value can be used instead of the estimated value. Therefore, equation (4B) becomes equation (4) above.

[0133] Therefore, the d-axis voltage feedforward command value V calculated by the feedforward command value calculation unit 23 dff * In the addition section 11 described above, the d-axis voltage command value V is... d ref The sums are used as the compensated d-axis voltage command value V. d * The output is thus suppressed or eliminated, thereby suppressing or eliminating the excitation of reluctance torque caused by q-axis voltage feedforward control.

[0134] (4-3) The effects of q-axis voltage feedforward control and d-axis voltage feedforward control

[0135] To verify the effectiveness of the q-axis feedforward control and d-axis feedforward control described above, simulation experiments were conducted. The driving conditions under this condition are... Figure 3 As shown in the diagram. When the rotational speed follows the commanded value of 3000 rpm, the mechanical angular frequency becomes 50 Hz, and the electrical angular frequency becomes 200 Hz. At this time, the frequency of the torque ripple becomes 1200 Hz (7540 rad / s) of the 6th order of the electrical angle. Figure 3 The frequency that becomes uncontrollable in the current control band shown.

[0136] exist Figures 4-7 The simulation results are shown in the figure. Figure 8 The figure shows the FFT analysis results of the motor torque using existing methods and the present invention. Furthermore, Figure 9 The diagram shows the improvement in torque ripple. Figure 4 The top segment represents the d-axis current value i d * The second segment from the top represents the d-axis current i. d The third segment from the top represents the q-axis current command value i. q * The fourth segment from the top represents the q-axis current i. q The bottom segment indicates the output torque of the motor (at a speed of 3000 rpm).

[0137] Figure 5 The results obtained by the existing method are shown, with the top section representing the d-axis current value i. d * and d-axis current i d The second segment from the top represents the q-axis current command value i. q * and q-axis current i q The third segment from the top represents the motor output torque, and the bottom segment represents the reluctance torque.

[0138] also, Figure 6 The results are shown when only q-axis voltage feedforward control is implemented. Similarly, the topmost segment represents the d-axis current value i. d * and d-axis current i d The second segment from the top represents the q-axis current command value i. q * and q-axis current i q The third segment from the top represents the motor output torque, and the bottom segment represents the reluctance torque.

[0139] also, Figure 7This shows the results of implementing both q-axis voltage feedforward control and d-axis voltage feedforward control. Similarly, the topmost segment represents the d-axis current value i. d * and d-axis current i d The second segment from the top represents the q-axis current command value i. q * and q-axis current i q The third segment from the top represents the motor output torque, and the bottom segment represents the reluctance torque.

[0140] also, Figure 8 The dashed lines represent the FFT analysis results of the motor torque obtained by the existing methods, the thin solid lines represent the FFT analysis results of the motor torque obtained by only q-axis voltage feedforward control, and the thick solid lines represent the FFT analysis results of the motor torque when both q-axis voltage feedforward control and d-axis voltage feedforward control are implemented.

[0141] from Figure 4 q-axis voltage feedforward control starts at 0.6s (using V) q (represented by FeedForward), d-axis voltage feedforward control starts at 0.8s (using V). d (Represented by Feedforward). Based on experimental results, by controlling the q-axis voltage feedforward, the ripple current of the 6th electrical angle flows through the q-axis, thus confirming a 76.3% reduction in the ripple of the motor's output torque. Figure 9 ).

[0142] On the other hand, by performing q-axis voltage feedforward control, a ripple component flowing through the q-axis appears on the d-axis interference voltage, exciting the d-axis current ripple. The phase of the d-axis current ripple is delayed by π / 2 compared to the phase of the q-axis current ripple. Therefore, the torque ripple excited as a reluctance ripple is delayed by π / 2 relative to the magnet torque ripple, reducing the torque ripple suppression effect of q-axis voltage feedforward. To suppress the voltage interference caused by q-axis voltage feedforward control, d-axis voltage feedforward control is performed to cancel the ripple component (starting from 0.8s).

[0143] Experiments confirm that the ripple component amplified by the q-axis voltage feedforward control is suppressed through this d-axis voltage feedforward control. Furthermore, the reduction in ripple of the reluctance torque caused by shaft interference confirms a reduction in motor torque ripple as well. Additionally, it is also confirmed that by implementing d-axis voltage feedforward control, compared to q-axis voltage feedforward control alone, the torque ripple at electrical angle 6 is reduced by 83.1%, a reduction compared to existing methods. Figure 9 Furthermore, the ripple component at the 12th order of the electrical angle (2400Hz) will not change due to control, as it is not subject to suppression control.

[0144] As detailed above, by implementing q-axis voltage feedforward control and d-axis voltage feedforward control applicable to electric motors driven using sensorless vector control (IPMSM), the vibration of electromagnetic energy caused by spatial high-order harmonics can be suppressed, thereby achieving the reduction of electromagnetic noise.

[0145] Furthermore, in this embodiment, the feedforward command value calculation unit 23 uses equation (3) to calculate the q-axis voltage feedforward command value V. qff * And using the subtraction unit 10 to obtain the q-axis voltage command value V q ref However, it is also possible to subtract the q-axis voltage feedforward command value V calculated by equation (3), but it is also possible to set the value to be the same as the value calculated by equation (3). qff * Alternatively, the feedforward command value calculation unit 23 sets the calculated value of equation (3) to be inverse phase, and sets an addition unit to replace the subtraction unit 10, by comparing the value set to this inverse phase with the q-axis voltage command value V. q ref Add them together to feed forward the q-axis voltage command value V. qff * From the q-axis voltage command value V q ref Subtract from the middle.

[0146] In this case, the unit described above as being in the opposite phase and the addition unit or feedforward command value calculation unit 23, along with the addition unit, constitute the subtraction unit in this invention. This is related to feeding forward the d-axis voltage command value V. dff * and d-axis voltage command value V d ref The relationship between the control-related feedforward command value calculation unit 23 and the addition unit 11 is of course the same (setting the d-axis voltage feedforward command value V). dff * The unit and subtraction section are for anti-phase operation, replacing the addition section 11.

[0147] Furthermore, in the embodiment, q-axis voltage feedforward control and d-axis voltage feedforward control are implemented for the 6th spatial harmonic of the electrical angle, but this is not limited to these (inventions other than those of claims 5 and 7). Alternatively, this can also be implemented for the 12th spatial harmonic of the electrical angle and spatial harmonics that are multiples of 6. Implementing this for multiple spatial harmonics can be expected to yield better results.

[0148] Label Explanation

[0149] 1. Motor control device

[0150] 2 Inverter Circuit

[0151] 3. Control Department

[0152] 4 DC power supply

[0153] 6. Electric Motor (IPMSM)

[0154] 10 Subtraction Section

[0155] 11. Addition Department

[0156] 15 Voltage Command Calculation Unit

[0157] 16-phase voltage command processing unit

[0158] 17 PWM signal generation unit

[0159] 23 Feedforward instruction value arithmetic unit.

Claims

1. An electric motor control device, which is a control device for an electric motor. The motor is a three-phase permanent magnet synchronous motor, and the motor control device is characterized by comprising: The voltage command calculation unit calculates the voltage command based on the d-axis current command value i of the motor. d * and q-axis current command value i q * To calculate the d-axis voltage command value V d ref and q-axis voltage command value V q ref ; The feedforward command value calculation unit calculates the q-axis voltage feedforward command value V based on the parameters of the spatial higher harmonics and the frequency characteristics of the motor windings. qff * ;as well as The subtraction unit calculates the q-axis voltage command value V from the voltage command arithmetic unit. q ref The q-axis voltage feedforward command value V calculated by the feedforward command value calculation unit is subtracted from the value of the feedforward command. qff * , Let the estimated q-axis current of the motor be i q (^), Set the 6th harmonic flux along the q-axis to k 6hq Set the estimated electrical angle value as θ re (^), Let the amplitude of the first component of the armature linkage flux be φ f Set the winding resistance to R and the q-axis winding inductance to L. q Set the electrical angular velocity as ω re hour, [Mathematical Expression 18] The feedforward command value calculation unit uses the above formula (3) to calculate the q-axis voltage feedforward command value V at electrical angle 6. qff * , The motor control device compensates for torque ripple caused by spatial high-order harmonics.

2. The motor control device as described in claim 1, characterized in that, The motor is a three-phase permanent magnet synchronous motor. The feedforward command value calculation unit calculates the q-axis voltage feedforward command value V by electrical angle 6n times. qff * , where n is a positive integer.

3. The motor control device as described in claim 1 or 2, characterized in that, The feedforward command value calculation unit calculates the q-axis voltage feedforward command value V based on the spatial higher harmonic values ​​after advancing the phase relative to the electrical angle estimation value based on the motor impedance. qff * .

4. The motor control device as described in claim 1 or 2, characterized in that, The feedforward command value calculation unit calculates the q-axis voltage feedforward command value V by multiplying the gain based on the impedance of the motor by the spatial higher harmonics. qff * .

5. The motor control device as described in claim 1 or 2, characterized in that, The feedforward command value calculation unit also includes an adder, which further calculates the q-axis voltage feedforward command value V. qff * The resulting q-axis current ripple interferes with the d-axis, which is the d-axis voltage feedforward command value V. dff * , And the d-axis voltage feedforward command value V calculated by the feedforward command value calculation unit dff * The d-axis voltage command value V calculated by the voltage command arithmetic unit d ref Add them together.

6. The motor control device as described in claim 5, characterized in that, The motor is a three-phase permanent magnet synchronous motor. Let the estimated q-axis current of the motor be i q (^), Set the 6th harmonic flux along the q-axis to k 6hq Set the estimated electrical angle value as θ re (^), Let the amplitude of the first component of the armature linkage flux be φ f Set the q-axis winding inductance to L q Set the electrical angular velocity as ω re hour, [Mathematical Expression 19] The feedforward command value calculation unit uses the above formula (4) to calculate the d-axis voltage feedforward command value V of electrical angle 6. dff * .

7. The motor control device as described in claim 5, characterized in that, The motor is a three-phase permanent magnet synchronous motor. The motor control device includes: an inverter circuit that drives the motor; The phase voltage command calculation unit will calculate the phase voltage command value V from the q-axis voltage command value V. q ref Subtract the q-axis voltage feedforward command value V from the middle qff * The subsequent q-axis voltage command value V q * and the d-axis voltage command value V d ref Add the d-axis voltage feedforward command value V dff * The subsequent d-axis voltage command value V d * Convert to three-phase modulated voltage command value; and The PWM signal generation unit generates a PWM signal for PWM control of the inverter circuit based on the three-phase modulation voltage command value.

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