Motor control device and compressor equipped with the same

Abstract

To provide a motor controller and a compressor comprising the same, the motor controller being capable of achieving consistency between a d axis current command and a q-axis current command in accordance with target motor control.SOLUTION: A motor controller 1 comprises an inverter 3 for converting DC voltage to three-phase AC voltage and outputting the three-phase AC voltage to a motor and inverter control means 10 for controlling the inverter, and performs field-weakening control by making negative current flow as d-axis current id. The motor controller comprises current command generation means 24 for generating a first d axis current command id1* on the basis of a line voltage command including a d axis voltage command vd* and a q-axis voltage command vq * of the motor and generating a first q-axis current command iq1* on the basis of the first d axis current command, when the field-weakening control is being executed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a motor control device and a compressor including the same.

Background Art

[0002] Servo systems using motors are used as power sources for various mechanical devices. In a general servo system, speed control and current control are performed in motor control. In general, in power conversion for outputting an AC voltage to a motor, a limit on the maximum output voltage or a limit on the maximum output current is provided.

[0003] Patent Document 1 discloses control for separately generating a d-axis current command and a q-axis current command in motor current control. Further, for the d-axis current command, different d-axis current commands are selected according to whether the motor is operating at low speed or high speed. In this way, by making it possible to select a plurality of d-axis currents according to the driving state of the motor, the operable range of the motor can be extended over a wide range from low speed to high speed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the d-axis current command and the q-axis current command disclosed in Patent Document 1 are generated separately, for example, when performing field weakening control, the d-axis current command and the q-axis current command may not be consistent with each other in the target motor control. And in this case, the behavior of the motor cannot be controlled as desired, or it takes time to perform the target control.

[0006] The present disclosure has been made in view of such circumstances, and an object thereof is to provide a motor control device capable of achieving consistency between a d-axis current command and a q-axis current command corresponding to a target motor control, and a compressor including the same.

Means for Solving the Problems

[0007] A motor control device according to some embodiments of the present disclosure includes an inverter that converts a DC voltage into a three-phase AC voltage and outputs the converted voltage to a motor, and inverter control means for controlling the inverter, and is a motor drive device that performs field weakening control by flowing a negative current through a d-axis current. When the field weakening control is being executed, a first d-axis current command is generated based on a line voltage command including a d-axis voltage command and a q-axis voltage command of the motor, and current command generation means for generating a q-axis current command based on the first d-axis current command is provided.

[0008] A compressor according to some embodiments of the present disclosure includes the above-described motor control device and a motor that is drive-controlled by the motor control device.

Advantages of the Invention

[0009] According to the present disclosure, there is an effect that consistency between a d-axis current command for controlling the rotational speed of a motor and a q-axis current command can be easily achieved.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0011] Hereinafter, an embodiment of a motor control device according to the present disclosure and a compressor including the same will be described with reference to the drawings.

[0012] In the following, for convenience of explanation, the positional relationship of each component described using the expressions "upper" and "lower" based on the paper surface indicates the vertically upper side and the vertically lower side, respectively. Also, in the present embodiment, those having the same effect in the vertical direction and the horizontal direction do not necessarily limit the vertical direction on the paper surface to the vertically vertical direction, and may correspond to, for example, the horizontal direction orthogonal to the vertical direction.

[0013] FIG. 1 is a diagram schematically showing the configuration of a motor control device 1 according to an embodiment of the present disclosure. As shown in FIG. 1, the motor control device 1 includes a converter 2 that converts AC power from an AC power source into DC power, an inverter 3 that converts the DC power output from the converter 2 into three-phase AC power and outputs it to the motor 4, and an inverter control device 10 that controls the inverter 3.

[0014] The inverter 3 includes a switching element of the upper arm and a switching element of the lower arm provided corresponding to each phase, and these switching elements are controlled to be turned on / off by a gate drive signal S given from the inverter control device 10, whereby the motor voltages of the U phase, V phase, and W phase supplied to the motor 4 are controlled. The motor 4 is, for example, a permanent magnet synchronous motor used as a drive source of a compressor.

[0015] In addition, the motor control device 1 includes a current sensor 5 that measures the motor current (currents of the U-phase, V-phase, and W-phase) flowing through the motor 4, and a voltage sensor 6 that measures the input DC voltage Vdc of the inverter 3. Regarding the motor current, it is also possible to detect two phases and obtain the remaining one phase by calculation from the detected two phases. Further, instead of such a measurement method, it is also possible to measure the three-phase motor currents iu, iv, and iw by providing a shunt resistor on the DC bus L. Thus, the method for obtaining the three-phase motor currents iu, iv, and iw is not particularly limited.

[0016] The three-phase motor currents detected by the current sensor 5 are converted into digital signals by the A / D conversion unit 7, and the input DC voltage Vdc detected by the voltage sensor 6 is converted into a digital signal by the A / D conversion unit 8, and then output to the inverter control device 10.

[0017] The inverter control device 10 is, for example, an MPU (Micro Processing Unit), and has a computer-readable recording medium on which a program for realizing the processing of each part described below is recorded. By the CPU reading out the program recorded on this recording medium to the main storage device such as RAM and executing it, the following processing in each part is realized. Examples of the computer-readable recording medium include a magnetic disk, a magneto-optical disk, and a semiconductor memory.

[0018] The inverter control device 10 generates a gate drive signal S for each phase so as to match the rotational speed of the motor 4 with the motor rotational speed command given from the upper control device (not shown), and controls the inverter 3 by applying these to the switching elements corresponding to each phase of the inverter 3, and supplies a desired three-phase AC voltage to the motor 4.

[0019] Specifically, the inverter 3 includes a three-phase / two-phase conversion unit 11, a speed / position estimation unit 12, a current PI control unit 15, a two-phase / three-phase conversion unit 16, a PWM control unit 17, a first processing unit 21, a second processing unit 22, a selection unit (selection means) 23, a current command generation unit (current command generation means) 24, a voltage saturation determination unit (determination means) 25, and a calculation unit 26.

[0020] The three-phase / two-phase conversion unit 11 converts the three-phase motor currents iu, iv, iw output from the A / D conversion unit 7 into two-phase currents, namely, the q-axis current iq and the d-axis current id, and outputs them to the speed / position estimation unit 12. The speed / position estimation unit 12 uses the q-axis current iq and the d-axis current id from the three-phase / two-phase conversion unit 11 and the two-phase voltage commands calculated by the current PI control unit 15 in the previous clock cycle, namely, the q-axis voltage command vq * and the d-axis voltage command vd * to calculate the estimated position θes of the motor 4 and the estimated rotational speed ωes of the motor 4. The estimated rotational speed ωes of the motor 4 is output to the first processing unit 21.

[0021] The first processing unit 21 generates a torque command τ * based on the deviation Δω between the rotational speed command ω * and the estimated rotational speed ωes. Here, the first processing unit 21 has a limiter function and adjusts the torque command τ * so that it does not exceed a preset upper limit value. Furthermore, the first processing unit 21 outputs the generated torque command τ * to the second processing unit 22 and the current command generation unit 24, respectively.

[0022] The calculation unit 26 calculates a second variable (Cv * ) which is the sum of the squares of the d-axis voltage command vd * based on the previous value of the first d-axis current command id1 * generated by the current command generation unit 24 described later and the q-axis voltage command vq * based on the previous value of the q-axis current command iq 2 , and outputs the calculated second variable (Cv 2 ) to the current command generation unit 24.

[0023] The current command generator 24 generates a d-axis voltage command vd * and q-axis voltage command vq * A first d-axis current command id1 based on a line voltage command * and generates the first d-axis current command id1 * Based on the first q-axis current command iq1 * Here, the current command generator 24 has a limiter function, and generates the first d-axis current command id1 * and the first q-axis current command iq1 * are adjusted so that each of them does not exceed a preset upper limit value.

[0024] Specifically, the current command generator 24 generates a first d-axis current command id1, which is a d-axis current command corresponding to the excitation current component. * Generate. More specifically, first, the current command generating unit 24 calculates a first variable (Cdc 2 ) is calculated. Then, the current command generator 24 calculates the first variable (Cdc 2 ) and the second variable (Cv 2 ) and the third variable, which is the difference between the first d-axis current command id1 * In addition, the first d-axis current command id1 generated by the current command generating unit 24 is generated. * is fed back to the current command generating unit 24 as the previous value, and a new first d-axis current command id1 * It is used to generate

[0025] For example, the current command generator 24 generates a first d-axis current command id1 by the following equation (1): * Generate (k).

[0026]

number

[0027] In the mathematical formula (1), k represents the current value, and k-1 represents the previous value. Note that the description of Lmt in the mathematical formula (1) means that the generation of the first d-axis current command id1 is repeatedly performed by this mathematical formula. * Also, Cdc 2 is the first variable derived from the square of the input DC voltage Vdc. Also, Cv 2 is the second variable derived from the sum of the squares of the d-axis voltage command vd * and the q-axis voltage command vq * . Also, γ is the coefficient calculated by the following mathematical formula (2).

[0028] [Number]

[0029] In the mathematical formula (2), φ is the variable derived from the magnetic flux linkage of the motor 4. Also, α is the coefficient for adjusting the magnetic flux linkage φ, for example, a value that varies according to each winding of the U-phase, V-phase, and W-phase. α is adjusted between 0 and 1 according to the response performance required for the first d-axis current command id1, and acts as a coefficient that accelerates convergence to a predetermined value when applied to the above-mentioned mathematical formula (1). Note that the larger α is, the faster it can converge to a predetermined value. Also, Ld is the variable derived from the d-axis inductance of the motor 4. * Also, the current command generation unit 24 generates a first q-axis current command iq1 corresponding to the torque component of the load.

[0030] Specifically, the current command generation unit 24 calculates a fourth variable based on the first d-axis current command id1, the d-axis inductance of the motor 4, the q-axis inductance of the motor 4, and the magnetic flux linkage of the motor 4, and generates the first q-axis current command iq1 based on the fourth variable and a fifth variable based on the torque command τ * of the motor 4. Specifically, the current command generation unit 24 calculates a fourth variable based on the first d-axis current command id1, the d-axis inductance of the motor 4, the q-axis inductance of the motor 4, and the magnetic flux linkage of the motor 4, and generates the first q-axis current command iq1 based on the fourth variable and a fifth variable based on the torque command τ * of the motor 4. * Specifically, the current command generation unit 24 calculates a fourth variable based on the first d-axis current command id1, the d-axis inductance of the motor 4, the q-axis inductance of the motor 4, and the magnetic flux linkage of the motor 4, and generates the first q-axis current command iq1 based on the fourth variable and a fifth variable based on the torque command τ * of the motor 4.

[0031] Here, the current command generation unit 24 generates the first q-axis current command iq1 * (k) according to the following mathematical formula (3).

[0032]

Equation

[0033] In the mathematical formula (3), Ct * is a value derived from the torque command τ * . Also, φ is the magnetic flux linkage of the motor 4. Also, Lm is a variable derived from the d-axis inductance and q-axis inductance of the motor 4. Also, id1 * (k) is the first d-axis current command generated according to the mathematical formula (1).

[0034] In this way, the current command generation unit 24 generates the first d-axis current command id1 2 based on the first variable (Cdc * ) which is the square of the DC voltage and the second variable (Cv * ) which is the sum of the squares of the d-axis voltage command vd 2 and the q-axis voltage command vq * . Also, the current command generation unit 24 generates the first q-axis current command iq1 * based on the newly generated first d-axis current command id1 * . That is, the current command generation unit 24 generates the first d-axis current command id1 * and generates the first q-axis current command iq1 * based on the first d-axis current command id1 * . Therefore, the consistency between the d-axis current command id * and the q-axis current command iq * can be easily achieved.

[0035] Next, the second processing unit 22 outputs a preset second d-axis current command id2 * . Here, the second d-axis current command id2 * is set to zero. Also, the second processing unit 22 outputs the second d-axis current command id2 *When it is zero, the second q-axis current command iq2 is generated based on the above formula (3). * is generated.

[0036] Further, when the line voltage command (the above-described second variable) of the motor 4 exceeds the maximum output voltage of the inverter 3 determined based on the input DC voltage Vdc of the inverter 3, the voltage saturation determination unit 25 determines that the field weakening control is being executed. When the voltage saturation determination unit 25 determines that the field weakening control is being executed, the selection unit 23 selects the first d-axis current command id1 * as the d-axis current command id * and selects the first q-axis current command iq1 * calculated based on the first d-axis current command id1 * as the q-axis current command iq * (selecting the contact S2 in FIG. 1). Also, when it is determined that the field weakening current is not being executed, the second d-axis current command id2 * , that is, zero, is selected as the d-axis current command id * and the second q-axis current command iq2 * corresponding to the case where the d-axis current command is zero is selected as the q-axis current command iq * (selecting the contact S1 in FIG. 1).

[0037] In the present embodiment, when the line voltage command of the motor 4 exceeds the maximum output voltage of the inverter 3, the voltage saturation determination unit 25 determines that the field weakening control is being executed. However, the present invention is not limited to this example. For example, when the line voltage command of the motor 4 exceeds a predetermined ratio of the maximum output voltage of the inverter 3, the voltage saturation determination unit 25 may determine that the field weakening control is being executed. In addition, as a method for determining whether or not the field weakening control is being executed, a known technique may be appropriately adopted. Further, the line voltage command of the motor 4 is not limited to the estimated line voltage command estimated using the two-phase voltage command in the previous clock cycle generated by the current PI control unit 15, and may be a measured value actually measured by a sensor.

[0038] For example, when the selection unit 23 satisfies the condition of the following mathematical formula (4), the first d-axis current command id1 * is selected as the d-axis current command id * and when the following condition is not satisfied, the second d-axis current command id2 * is selected as the d-axis current command id * It may be selected as.

[0039] Vmax 2 =(Vdc 2 / 2)<Cv 2 =vq *2 +vd *2 (4)

[0040] In the above mathematical formula (4), Vmax 2 is the square of the value corresponding to the maximum output voltage of the inverter 3, and Cv 2 is the value corresponding to the square of the line voltage of the motor 4. Here, comparing the square of the line voltage command of the motor 4 with the maximum output voltage of the inverter 3 determined based on the DC voltage input to the inverter 3 is to avoid the calculation load of the microcomputer from increasing by eliminating the need for square root calculation. The d-axis current command id * and the q-axis current command iq * selected by the selection unit 23 in this way are each output to the current PI control unit 15.

[0041] The current PI control unit 15 receives the d-axis current command id * and the q-axis current command iq * selected by the selection unit 23, and the q-axis current iq and the d-axis current id from the three-phase / two-phase conversion unit 11, and further, the estimated position θes of the motor 4 from the speed / position estimation unit 12 are input.

[0042] The current PI control unit 15 calculates the deviation between the q-axis current command iq * and the q-axis current iq and the deviation between the d-axis current command id * and the d-axis current id, and calculates the q-axis voltage command vq * and the d-axis voltage command vd such that these deviations approach 0.* is generated. Specifically, proportional-integral control (PI control) is performed for each deviation. Further, at this time, the estimated position θes of the motor 4 is referred to, so that the q-axis voltage command vq * and the d-axis voltage command vd * are calculated and output to the two-phase / three-phase conversion unit 16. Here, no limiter is provided for the d-axis voltage command vd * , and a limiter is applied to the q-axis voltage command vq * with Vdc / √2.

[0043] The two-phase / three-phase conversion unit 16 refers to the estimated position θes estimated by the speed / position estimation unit 12, so that the q-axis voltage command vq * and the d-axis voltage command vd * are converted into three-phase voltage commands vu * , vv * , vw * and output to the PWM control unit 17. The three-phase voltage commands vu * , vv * , vw * and the input DC voltage Vdc from the A / D conversion unit 8 are input to the PWM control unit 17. The PWM control unit 17 generates a triangular wave (carrier wave) with a predetermined carrier frequency, compares this triangular wave with the three-phase voltage commands vu * , vv * , vw * respectively, and further corrects the duty ratio of the PWM pulse using the input DC voltage Vdc, thereby generating a gate drive signal S corresponding to each phase and outputting it to the inverter 3.

[0044] Thus, when the field weakening control is being executed, the method for generating the first d-axis current command id1 * and the first q-axis current command iq1 * of the motor control device 1 of the present disclosure is different from that of the conventional motor control device. Specifically, when the field weakening control is being executed, based on the line voltage command including the d-axis voltage command vd * and the q-axis voltage command vq * of the motor 4, a new first d-axis current command id1 *while generating the generated first d-axis current command id1 * based on the first q-axis current command iq1 * is generated. As a result, the d-axis current command id * and the q-axis current command iq * It becomes possible to perform motor control that easily achieves the consistency of

[0045] Next, the transition of the motor current in the motor control by the motor control device 1 according to the present disclosure will be described. FIG. 2 shows the d-axis current command id of the motor control device 1 when the field weakening control is being executed * and the first q-axis current command iq1 * is a diagram showing the motor current curve when each is generated individually. FIG. 3 shows the first d-axis current command id1 of the motor control device 1 when the field weakening control is being executed * based on the first q-axis current command iq1 * is a diagram showing the motor current curve when is generated. In both figures, the horizontal axis represents the d-axis current and the vertical axis represents the q-axis current. Also, curve X shows the constant-linkage magnetic flux curve when the rotational speed of motor 4 is ω_A, curve Y shows the constant-linkage magnetic flux curve when the rotational speed of motor 4 is ω_A, and curve Z shows the low torque curve. And the broken line in the figure shows the transition in which the value of the motor current changes from point A to point B.

[0046] Comparing FIGS. 2 and 3, the broken line in FIG. 3 follows curve Z more than the broken line in FIG. 2, and the path when the motor current changes from point A to point B is shorter. That is, it can be understood that the condition illustrated in FIG. 3 can reach the control target more quickly. Therefore, the d-axis current command id * and the q-axis current command iq * When the first d-axis current command id1 is generated based on the method disclosed in the present embodiment rather than when each is generated individually * based on the first q-axis current command iq1 * results in stable control with suppressed vibration.

[0047] Further, FIGS. 4 and 5 are waveform diagrams for comparing the transitions of each parameter of the motor 4 when field weakening control is being executed. FIG. 4 shows the transitions of each parameter of the motor 4 when the motor control device 1 individually generates the d-axis current command id * and the q-axis current command iq * respectively. FIG. 5 is a waveform diagram showing the transitions of each parameter of the motor 4 when the motor control device 1 generates the first q-axis current command iq1 * based on the first d-axis current command id1 * . FIGS. 4(a) and 5(a) are waveform diagrams showing the transitions of the rotational speed of the motor 4. FIGS. 4(b) and 5(b) are waveform diagrams showing the transitions of the d-axis current id. FIGS. 4(c) and 5(c) are waveform diagrams showing the transitions of the q-axis current iq. FIGS. 4(d) and 5(d) are waveform diagrams showing the transitions of the motor torque.

[0048] From FIG. 4(a), when the motor control device 1 individually generates the d-axis current command id * and the q-axis current command iq * , the rotational speed of the motor 4 has an overshoot when reaching the target rotational speed ω_B from the rotational speed ω_A, and after decaying and oscillating for a certain period of time, it converges to the rotational speed ω_B. This indicates that in the motor control corresponding to FIG. 4(a), since the d-axis current command id * and the first q-axis current command iq1 * are not generated considering each other's command values, the decaying oscillation of the rotational speed occurs during the period when the correction of the d-axis current command id * and the q-axis current command iq * is repeatedly performed.

[0049] On the other hand, from FIG. 5(a), when the motor control device 1 generates the first q-axis current command iq1 * based on the first d-axis current command id1 * , the rotational speed of the motor 4 does not have an overshoot when reaching the target rotational speed ω_B from the rotational speed ω_A, and quickly transitions to the rotational speed ω_B. This is because in the motor control corresponding to FIG. 5(a), based on the first d-axis current command id1 * , the first q-axis current command iq1* is generated, the d-axis current command id * and the q-axis current command iq * are made consistent. Therefore, comparing the two figures, when the field weakening control is being executed, the motor control device 1 can more quickly stabilize the rotational speed of the motor 4 to the target value when generating the first q-axis current command iq1 * based on the first d-axis current command id1 * .

[0050] Also, from FIG. 4(b), when the motor control device 1 individually generates the d-axis current command id * and the q-axis current command iq * , an overshoot occurs when the d-axis current reaches the target current value id_B from the current value id_A, and after decaying and oscillating for a certain period of time, it converges to the current value id_B. This indicates that in the motor control corresponding to FIG. 4(b), during the period when the correction of the d-axis current command id * and the q-axis current command iq * is repeatedly performed, the decaying oscillation of the d-axis current occurs because the d-axis current command id * and the q-axis current command iq * are not generated considering each other's command values.

[0051] On the other hand, from FIG. 5(b), when the motor control device 1 generates the first q-axis current command iq1 * based on the first d-axis current command id1 * , no overshoot occurs when the d-axis current id reaches the target current value id_B from the current value id_A, and it quickly transitions to the current value id_B. This is because in the motor control corresponding to FIG. 5(b), since the first q-axis current command iq1 * is generated based on the first d-axis current command id1 * , the d-axis current command id * and the q-axis current command iq * are made consistent. Therefore, when comparing the two figures, in the case where the field weakening control is executed, the motor control device 1 can more quickly stabilize the current value of the d-axis current id to the target value when generating the first q-axis current command iq1 * based on the first d-axis current command id1 * .

[0052] Also, from FIG. 4(c), when the motor control device 1 individually generates the d-axis current command id * and the q-axis current command iq * , an overshoot occurs when the q-axis current iq reaches the target current value iq_B from the current value iq_A, and it converges to the current value iq_B after decaying and oscillating for a certain period of time. This indicates that in the motor control corresponding to FIG. 4(c), since the d-axis current command id * and the q-axis current command iq * are not generated considering each other's command values, the decaying oscillation of the q-axis current iq occurs during the period when the corrections of the d-axis current command id * and the q-axis current command iq * are repeatedly performed.

[0053] On the other hand, from FIG. 5(c), when the motor control device 1 generates the first q-axis current command iq1 * based on the first d-axis current command id1 * , no overshoot occurs when the q-axis current iq reaches the target current value iq_B from the current value iq_A, and it quickly transitions to the current value iq_B. This is because in the motor control corresponding to FIG. 5(c), since the first q-axis current command iq1 * is generated based on the first d-axis current command id1 * , the consistency of the d-axis current command id * and the q-axis current command iq * is achieved. Therefore, when comparing the two figures, in the case where the field weakening control is executed, the motor control device 1 can more quickly stabilize the current value of the d-axis current id to the target value when generating the first q-axis current command iq1 * based on the first d-axis current command id1 * . *The current value can be quickly stabilized to the target value.

[0054] Also, from FIG. 4(d), when the motor control device 1 individually generates the d-axis current command id * and the q-axis current command iq * respectively, the motor torque decays and oscillates for a certain period with the changes in the d-axis current command id * and the q-axis current command iq * and converges to the torque τm again. This indicates that in the motor control corresponding to FIG. 4(d), since the d-axis current command id * and the q-axis current command iq * are not generated considering each other's command values, the attenuation oscillation of the motor torque occurs during the period when the corrections of the d-axis current command id * and the q-axis current command iq * are repeatedly performed.

[0055] On the other hand, from FIG. 5(d), when the motor control device 1 generates the first q-axis current command iq1 * based on the first d-axis current command id1 * , the motor torque quickly converges to the torque τm again without attenuation oscillation. This is because in the motor control corresponding to FIG. 5(d), since the first q-axis current command iq1 * is generated based on the first d-axis current command id1 * , the consistency of the d-axis current command id * and the q-axis current command iq * is achieved. Therefore, comparing the two figures, when the field weakening control is being executed, when the motor control device 1 generates the first q-axis current command iq1 * based on the first d-axis current command id1 * , the motor torque can be quickly stabilized to the target value.

[0056] From the above, according to the motor control device of the present disclosure, when the field weakening control is being executed, the first q-axis current command iq1 *is generated based on the first d-axis current command id1 by the current command generation unit 24 * Thus, the first q-axis current command iq1 * changes corresponding to the change amount of the first d-axis current command id1 * so that it is possible to easily achieve the consistency between the d-axis current command id * and the q-axis current command. Furthermore, by generating the first q-axis current command iq1 * in this way, it is possible to promptly stabilize the behavior of the motor 4 corresponding to the target motor control.

[0057] According to this embodiment, the following effects can be obtained. According to the motor control device 1 of the present disclosure, when the field weakening control is being executed, the current command generation unit 24 generates the first q-axis current command iq1 * for controlling the motor 4 based on the first d-axis current command id1 * Thereby, it is possible to easily achieve the consistency between the first d-axis current command id1 * for controlling the rotational speed of the motor and the first q-axis current command iq1 * Furthermore, by improving the consistency between the d-axis current command id * and the q-axis current command iq * the vibration of the motor 4 can be reduced, and the behavior of the motor 4 can be stabilized.

[0058] Also, according to the motor control device 1 of the present disclosure, depending on whether the field weakening control is being executed, it is possible to switch and select either the first d-axis current command id1 * or the second d-axis current command id2 * as the d-axis current command id * Specifically, when the field weakening control is being executed, the first d-axis current command id1 * is selected as the d-axis current command id * and when the field weakening control is not being executed, the second d-axis current command id2 * is selected as the d-axis current command id * Thereby, it is possible to reduce the arithmetic processing amount of the d-axis current command id * ​

[0059] Also, according to the motor control device 1 of the present disclosure, when field weakening control is being executed, the current command generation unit 24 calculates a difference between a first variable, which is the square value of the DC voltage, and a third variable, which is the sum of the squares based on the previous values of the d-axis voltage command vd * based on the first d-axis current command id1 * and the q-axis voltage command vq * based on the first q-axis current command iq1 * to generate the first d-axis current command id1 * . Then, based on the newly generated first d-axis current command id1 * , the first q-axis current command iq1 * is generated. As a result, the d-axis current command id * and the q-axis current command iq * can be made into commands that take into account changes in the DC voltage command, the d-axis voltage command vd * and the q-axis voltage command vq * . Therefore, the consistency between the d-axis current command id * and the q-axis current command iq * can be easily achieved. Also, by the current command generation unit 24 using the second variable based on the previous values of the d-axis voltage command vd * and the q-axis voltage command vq * to generate the first d-axis current command id1 * and the first q-axis current command iq1 * , it is possible to suppress the d-axis current command id * and the q-axis current command iq * from overshooting the target value and to stabilize the behavior of the motor more quickly.

[0060] Also, according to the motor control device 1 of the present disclosure, when field weakening control is being executed, the current command generation unit 24 generates the first q-axis current command iq1 * based on a fourth variable that varies according to the first d-axis current command id1 * and a fifth variable based on the torque command of the motor. As a result, considering each parameter when driving the motor 4, the q-axis current command iq *It can be generated. That is, it becomes possible to further stabilize the behavior of the motor 4 in consideration of the actual operation of the motor 4.

[0061] (Supplementary Note) As described above, the present disclosure has been described using embodiments. However, the technical scope of the present disclosure is not limited to the scope described in the above embodiments. Various changes or improvements can be made to the above embodiments without departing from the gist of the present disclosure, and the forms with such changes or improvements are also included in the technical scope of the present disclosure. Also, the above embodiments may be combined as appropriate.

[0062] The motor control device described in the above-described embodiment and the compressor including the same can be understood as follows, for example. The motor control device (1) according to the first aspect of the present disclosure includes an inverter (3) that converts a DC voltage into a three-phase AC voltage and outputs it to a motor, and an inverter control means (10) that controls the inverter. It is a motor drive device that performs field weakening control by flowing a negative current through the d-axis current (id). When the field weakening control is being executed, based on the line voltage command including the d-axis voltage command (vd * ) and the q-axis voltage command (vq * ), a first d-axis current command (id1 * ) is generated, and current command generation means (24) that generates a first q-axis current command (iq1 * ) based on the first d-axis current command is provided.

[0063] According to the motor control device of the present disclosure, when field weakening control is being executed, the current command generation means generates a first d-axis current command based on the line voltage command including the d-axis voltage command and the q-axis voltage command of the motor, and generates a first q-axis current command based on the first d-axis current command. In other words, instead of calculating the q-axis current command independently from the d-axis current command, it is calculated based on the d-axis current command. Thereby, it becomes possible to easily achieve the consistency between the d-axis current command for controlling the rotational speed of the motor and the q-axis current command. Furthermore, by improving the consistency between the d-axis current command and the q-axis current command, the vibration of the motor is reduced, and it becomes possible to stabilize the behavior of the motor.

[0064] The motor control device according to the second aspect of the present disclosure, in the first aspect, when the line voltage command of the motor exceeds a predetermined output value of the inverter determined based on the DC voltage input to the inverter, determination means (25) for determining that field weakening control is being executed, and when it is determined by the determination means that the field weakening control is being executed, the first d-axis current command is selected, and when it is determined that the field weakening control is not being executed, a second d-axis current command id2 * is provided with selection means (23) for selecting.

[0065] According to the motor control device of the present disclosure, it is possible to select whether or not to generate a first d-axis current command and a first q-axis current command based on the first d-axis current command according to whether or not field weakening control is being executed. That is, when field weakening control is not being executed, by using the second d-axis current command which is a predetermined value set in advance, it becomes possible to reduce the calculation processing amount of the d-axis current command. Also, for example, it becomes possible to use an inexpensive microcomputer as the inverter control means, and cost reduction can be achieved.

[0066] In the motor control device according to the third aspect of the present disclosure, in the first aspect or the second aspect, when the field weakening control is being executed, the current command generation means calculates a third variable, which is the difference between a first variable that is the square value of the DC voltage and a second variable that is the sum of the squares of a d-axis voltage command based on the previous value of the first d-axis current command and a q-axis voltage command based on the previous value of the first q-axis current command, and generates the first d-axis current command based on the third variable, and generates the first q-axis current command based on the generated first d-axis current command.

[0067] According to the motor control device of the present disclosure, when the field weakening control is being executed, the current command generation means calculates a third variable, which is the difference between a first variable that is the square value of the DC voltage and a second variable that is the sum of the squares of a d-axis voltage command based on the previous value of the first d-axis current command and a q-axis voltage command based on the previous value of the first q-axis current command, and generates the first d-axis current command based on the third variable, and generates the first q-axis current command based on the newly generated first d-axis current command. Thereby, the first d-axis current command and the first q-axis current command can be made into commands that take into account changes in the DC voltage command, the d-axis voltage command, and the q-axis voltage command. Therefore, the consistency between the d-axis current command and the q-axis current command can be easily achieved. Further, by the current command generation unit 24 generating the first d-axis current command and the first q-axis current command using the second variable based on the previous values of the d-axis voltage command and the q-axis voltage command, it is possible to suppress the first d-axis current command and the first q-axis current command from overshooting the target value, and to more quickly stabilize the behavior of the motor.

[0068] In the motor control device according to the fourth aspect of the present disclosure, in any one of the first aspect to the third aspect, when the field weakening control is being executed, the current command generation means calculates a fourth variable based on the first d-axis current command, the inductance of the d-axis of the motor, the inductance of the q-axis of the motor, and the mutual flux linkage of the motor, and generates the first q-axis current command based on the fourth variable and a fifth variable based on the torque command (τ * ) of the motor.

[0069] According to the motor control device of the present disclosure, when field-weakening control is being executed, the current command generation means generates a first q-axis current command based on a fourth variable that varies with the first-axis current command and a fifth variable based on the torque command of the motor. Thereby, the q-axis current command can be generated in consideration of each parameter when driving the motor. That is, it becomes possible to further stabilize the behavior of the motor in consideration of the actual operation of the motor.

[0070] The compressor according to the first aspect of the present disclosure includes any one of the motor control devices of the first aspect to the fourth aspect and a compressor motor (4) that is drive-controlled by the motor control device.

Description of Signs

[0071] 1 Motor control device 2 Converter 3 Inverter 4 Motor 5 Current sensor 6 Voltage sensor 7 A / D conversion unit 8 A / D conversion unit 10 Inverter control device 11 Three-phase / Two-phase conversion unit 12 Speed / Position estimation unit 15 Current PI control unit 16 Two-phase / Three-phase conversion unit 17 PWM control unit 21 First processing unit 22 Second processing unit 23 Selection unit 24 Current command generation unit 25 Voltage saturation determination unit (50) Arithmetic unit id * d-axis current command id1 * First d-axis current command id2 * Second d-axis current command iq * q-axis current command iq1 * First q-axis current command iq2 * Second q-axis current command vd * d-axis voltage command vq * q-axis voltage command τ * Torque command

Claims

1. An inverter that converts a DC voltage into a three-phase AC voltage and outputs it to a motor, and inverter control means for controlling the inverter, and is a motor drive device that performs field weakening control by flowing a negative current through the d-axis current, A motor control device including current command generation means for generating a first d-axis current command based on a line voltage command including a d-axis voltage command and a q-axis voltage command of the motor when the field weakening control is being executed, and generating a first q-axis current command based on the first d-axis current command.

2. Determination means for determining that field weakening control is being executed when the line voltage command of the motor exceeds a predetermined output value of the inverter determined based on the DC voltage input to the inverter; Selection means for selecting the first d-axis current command when it is determined by the determination means that the field weakening control is being executed, and selecting a preset second d-axis current command when it is determined that the field weakening control is not being executed The motor control device according to claim 1, comprising:

3. When the field weakening control is being executed, the current command generation means generates the first d-axis current command based on a third variable that is a difference between a first variable that is a value of the square of the DC voltage and a second variable that is a sum of the squares of a d-axis voltage command based on the previous value of the first d-axis current command and a q-axis voltage command based on the previous value of the first q-axis current command, and generates the first q-axis current command based on the generated first d-axis current command. The motor control device according to claim 1.

4. When the field weakening control is being executed, the current command generation means calculates a fourth variable based on the first d-axis current command, the inductance of the d-axis of the motor, the inductance of the q-axis of the motor, and the mutual magnetic flux of the motor, and generates the first q-axis current command based on the fourth variable and a fifth variable based on the torque command of the motor. The motor control device according to claim 1.

5. A compressor comprising the motor control device according to claim 1, and a compressor motor driven and controlled by the motor control device ​

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