JP2015133802A - Control device and control method for synchronous motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent step out at synchronous control time, in a synchronous motor which uses both sensorless vector control and synchronous control.SOLUTION: A control device of a synchronous motor includes a control part and a current command generation part. The control part executes synchronous control in a first speed region and performs sensorless vector control in a second region higher than first speed region. At the synchronous control, the current command generation part sets a q axis current command to zero, and sets a d axis current command to a value corresponding to a state of the speed variation. During a fixed speed in the first speed region, the current command generation part sets the d axis current command to a first value which is a fixed value. In at least either of acceleration or deceleration in the first speed region, the current command generation part sets the d axis current command to a second value larger than the first value.

Description

  The present invention relates to a technique for controlling a synchronous motor. In particular, the present invention relates to a control technique for a synchronous motor that uses both sensorless vector control and synchronous control.

  As a drive control method for a synchronous motor, vector control for controlling torque and speed with high accuracy based on the position (phase) of a rotor is known. In recent years, a technique for estimating the position and speed of a rotor by software based on current and voltage without using a position sensor such as an encoder has been put into practical use. Vector control using such position / velocity estimation technology is called “sensorless vector control”.

  Sensorless vector control is advantageous from the viewpoints of low cost, downsizing of the apparatus, and improvement of reliability. However, since the influence of the voltage error becomes large in the low speed region, the position and speed estimation accuracy deteriorates. Therefore, in the low-speed region, a technique for performing “synchronous control” instead of sensorless vector control has been proposed (see Patent Document 1 and Patent Document 2).

  As described in Patent Documents 1 and 2, in synchronous control (synchronous current control), the inverter is controlled with a synchronous phase obtained by integrating the speed command ω *. Therefore, the frequency of the output current of the inverter (that is, the rotational speed of the rotor) matches the speed command ω *. Further, the excitation current command id * is fixed at a constant level, and a current corresponding to the fixed level of the excitation current command id * always flows through the synchronous motor. The maximum torque that can be output in the synchronous control is determined by the fixed level of the excitation current command id *.

  A switching method between the synchronous control in the low speed region and the sensorless vector control in the high speed region is described in Patent Document 2, for example.

JP 2009-247082 A JP 2012-19626 A

  As described above, in the synchronous control, the excitation current command id * is fixed at a constant level, and a current corresponding to the fixed level of the excitation current command id * always flows through the synchronous motor. The maximum torque that can be output in the synchronous control is determined by the fixed level of the excitation current command id *.

  In order to increase the maximum torque, it is conceivable to set the fixed level of the excitation current command id * high. However, in this case, during a constant speed operation, even if the load is light, a large current continues to flow to the synchronous motor, which may cause a thermal trip.

  Conversely, when the excitation current command id * is set at a fixed level that does not cause a thermal trip during constant speed operation, the maximum torque is less than the rated torque. However, in this case, if acceleration / deceleration torque exceeding the rated torque is required during sudden acceleration / deceleration, the step-out occurs due to insufficient torque.

  One object of the present invention is to provide a technique capable of preventing step-out during synchronous control in drive control of a synchronous motor that uses both sensorless vector control and synchronous control.

  In one aspect of the present invention, a control device for a synchronous motor is provided. The control device includes a control unit and a current command generation unit. The control unit performs drive control of the synchronous motor by synchronous control in the first speed region, and performs drive control of the synchronous motor by sensorless vector control in the second speed region higher than the first speed region. The current command generation unit generates a d-axis current command and a q-axis current command for the drive control. More specifically, in the case of synchronous control, the current command generation unit sets the q-axis current command to zero, and sets the d-axis current command to a value corresponding to the state of speed change. At a constant speed in the first speed region, the current command generation unit sets the d-axis current command to a first value that is a fixed value. In addition, at least one of acceleration and deceleration in the first speed region, the current command generation unit sets the d-axis current command to a second value that is larger than the first value.

  In another aspect of the present invention, a method for controlling a synchronous motor is provided. The control method includes (A) a step of performing drive control of the synchronous motor by synchronous control in the first speed region, and (B) a step of controlling the synchronous motor by sensorless vector control in the second speed region higher than the first speed region. Performing drive control. The step (A) of performing the drive control by the synchronous control includes the step of setting the q-axis current command to zero and the d-axis current command to a value corresponding to the state of the speed change. The step of setting the d-axis current command includes (a) a step of setting the d-axis current command to a first value which is a fixed value at a constant speed in the first speed region, and (b) acceleration in the first speed region. Setting the d-axis current command to a second value larger than the first value at least during the time or at the time of deceleration.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to prevent the step-out at the time of synchronous control in the drive control of the synchronous motor which uses sensorless vector control and synchronous control together.

FIG. 1 is a conceptual diagram for explaining conventional synchronous control and sensorless vector control. FIG. 2 is a diagram illustrating a relationship between the d-axis current command and the maximum torque in the synchronous control. FIG. 3 is a conceptual diagram for explaining synchronous control and sensorless vector control according to the embodiment of the present invention. FIG. 4 is a block diagram illustrating a configuration example of the control device for the synchronous motor according to the first embodiment. FIG. 5 is a block diagram showing a configuration of the first current command generation unit in the second embodiment. FIG. 6 is a graph showing the operation of the first current command generator in the second embodiment. FIG. 7 is a block diagram showing a configuration of the first current command generation unit in the third embodiment. FIG. 8 is a graph showing the operation of the first current command generator in the third embodiment. FIG. 9 is a block diagram showing the configuration of the first current command generation unit in the fourth embodiment. FIG. 10 is a graph showing the operation of the first current command generator in the fourth embodiment. FIG. 11 is a block diagram for explaining the fifth embodiment. FIG. 12 is a block diagram showing a configuration of the first current command generator in the sixth embodiment.

  Embodiments of the present invention will be described with reference to the accompanying drawings.

Embodiment 1 FIG.
<Synchronous control and sensorless vector control>
In the embodiment of the present invention, “sensorless vector control” and “synchronous control” are used in combination as drive control of the synchronous motor. In order to facilitate understanding of the present embodiment, first, general concepts of conventional sensorless vector control and synchronous control will be described with reference to FIG.

  As shown in FIG. 1, the sensorless vector control and the synchronous control are switched according to the speed. More specifically, synchronous control is performed in the low speed region R1 (first speed region), and sensorless vector control is performed in the high speed region R2 (second speed region). Here, the low speed region R1 is a region where the speed is equal to or lower than the first threshold value ωt1, and the high speed region R2 is a region where the speed is equal to or higher than the second threshold value ωt2 (> ωt1). In a region between the low speed region R1 and the high speed region R2, switching control between synchronous control and sensorless vector control is performed. Note that any switching control method may be used (see, for example, Patent Document 2).

  In FIG. 1, id * and iq * represent a d-axis current command (excitation current command) and a q-axis current command that are generally used in the drive control of the synchronous motor, respectively. The dq coordinate system is a coordinate system of the rotor of the synchronous motor. The d-axis is the direction of the magnetic axis of the rotor, and the d-axis current corresponds to an excitation current component. The q axis is a direction orthogonal to the d axis.

  In sensorless vector control, the d-axis current command id * and the q-axis current command iq * are controlled by a well-known algorithm, thereby realizing highly accurate speed control and torque control.

  On the other hand, in the synchronous control, the q-axis current command iq * is set to zero (iq * = 0). In the conventional synchronous control, the d-axis current command id * is fixed at a constant level. The fixed level d-axis current command id * is hereinafter referred to as “fixed d-axis current command id0 *”. In this case, a current corresponding to the fixed d-axis current command id0 * always flows through the synchronous motor.

  FIG. 2 shows the relationship between the d-axis current command id * and the maximum torque in the synchronous control. The horizontal axis represents the d-axis current command id *, and the vertical axis represents the maximum torque that can be output. As shown in FIG. 2, the maximum torque that can be output in the synchronous control is determined by the magnitude of the d-axis current command id *. Here, the maximum torque when the d-axis current command id * is the rated current im is the rated torque Tm.

  In order to increase the maximum torque, it is conceivable to set the fixed d-axis current command id0 * to be larger than the rated current im. However, in this case, during a constant speed operation, even if the load is light, a large current continues to flow to the synchronous motor, which may cause a thermal trip.

  In order to prevent the occurrence of such a thermal trip, it is necessary to set the fixed d-axis current command id0 * below the rated current im as shown in FIGS. In this case, the maximum torque T0 that can be output is equal to or less than the rated torque Tm. However, during rapid acceleration / deceleration, acceleration / deceleration torque exceeding the rated torque Tm may be required. In this case, in the conventional synchronous control as shown in FIG. 1, the step-out may occur due to insufficient torque.

<Outline of synchronous control according to the present embodiment>
Next, synchronization control according to the present embodiment will be described with reference to FIG. In the present embodiment, the d-axis current command id * and the q-axis current command iq * in the synchronous control are referred to as the first d-axis current command id1 * and the first q-axis current command iq1 *, respectively.

  According to the present embodiment, the first q-axis current command iq1 * is set to zero (iq1 * = 0) as in the case of FIG. On the other hand, unlike the case of FIG. 1, the first d-axis current command id1 * is not fixed only to the fixed d-axis current command id0 *. The first d-axis current command id1 * is set to a value according to the speed change situation.

  More specifically, during a constant speed operation in the low speed region R1, the first d-axis current command id1 * is set to the fixed d-axis current command id0 * (id1 * = id0 *). However, during acceleration / deceleration in the low speed region R1, the first d-axis current command id1 * is appropriately corrected to a value larger than the fixed d-axis current command id0 *. The corrected value is hereinafter referred to as “corrected d-axis current command id0 ′ *”. A difference id ** (= id0 ′ * − id0 *) between the corrected d-axis current command id0 ′ * and the fixed d-axis current command id0 * is a “correction value”.

Formula (1):
(At constant speed) id1 * = id0 *
(At acceleration / deceleration) id1 * = id0 '* = id0 * + id **> id0 *

  The maximum torque that can be output in the case of the fixed d-axis current command id0 * is T0. On the other hand, the maximum torque that can be output in the case of the corrected d-axis current command id0 ′ * is T0 ′ (= T0 + ΔT) that is larger than T0. That is, during acceleration / deceleration, the maximum torque that can be output temporarily increases from T0 to T0 '.

  Thus, according to the present embodiment, during acceleration / deceleration in the low speed region R1, the first d-axis current command id1 * is set to a corrected d-axis current command id0 ′ * that is larger than the fixed d-axis current command id0 *. The As a result, during acceleration / deceleration, the maximum torque that can be output temporarily increases, and torque shortage and thus step-out are prevented.

  In addition, since torque shortage during acceleration / deceleration is resolved, it is not necessary to set the fixed d-axis current command id0 * at a constant speed excessively large. As a result, since the current flowing through the synchronous motor at a constant speed is reduced, excessive power consumption is suppressed and efficiency is improved.

  The corrected d-axis current command id0 '* according to the present embodiment does not necessarily have to be applied in both cases of acceleration and deceleration. The above effect can be obtained even when applied to either acceleration or deceleration. For example, the corrected d-axis current command id0 '* may be applied only at the time of acceleration where a torque shortage tends to be noticeable.

<Example of control device>
Next, a configuration example for realizing sensorless vector control and synchronization control according to the present embodiment will be described. FIG. 4 shows a configuration example of the control device 1 of the synchronous motor SM according to the present embodiment.

  The control device 1 performs drive control of the synchronous motor SM. More specifically, the control device 1 includes an inverter 10, a current detector 20, a coordinate converter 30, a voltage command generation unit 40, a coordinate converter 50, a PWM control unit 60, a position / speed estimation unit 70, and a switching control unit 80. , Θ calculator 90, and current command generator 100.

  The inverter 10 includes a switching element and is switching-controlled by a gate signal SG supplied from the PWM control unit 60. The inverter 10 converts the DC voltage into a three-phase AC voltage by the switching control, and supplies it to the synchronous motor SM. The motor currents iu, iv and iw flow due to the AC voltage supplied to the synchronous motor SM, and the synchronous motor SM rotates.

  The current detector 20 is arranged between the inverter 10 and the synchronous motor SM, and is configured to detect the motor currents iu, iv, iw. Here, the current detector 20 may detect two phases of the motor currents iu, iv, iw. This is because the remaining one phase can be calculated from the detected two phases. The detected current (eg, iu, iv) detected by the current detector 20 is input to the coordinate converter 30.

  The coordinate converter 30 performs coordinate conversion from the uvw coordinate system to the dq coordinate system on the detected current detected by the current detector 20. By this coordinate conversion, a d-axis detection current id that is a d-axis component of the detection current and a q-axis detection current iq that is a q-axis component of the detection current are obtained. Note that the phase θ (rotor position) used in this coordinate conversion is calculated by a θ calculator 90 described later.

  The voltage command generator 40 receives a d-axis current command id * and a q-axis current command iq * output from a current command generator 100 described later. The voltage command generator 40 generates a d-axis voltage command Vd * and a q-axis voltage command Vq * from the d-axis current command id * and the q-axis current command iq *. More specifically, the voltage command generation unit 40 receives the d-axis detection current id and the q-axis detection current iq output from the coordinate converter 30 described above. Then, the voltage command generation unit 40 performs the d-axis voltage command by proportional integral control so that the d-axis detection current id and the q-axis detection current iq match the d-axis current command id * and the q-axis current command iq *, respectively. Vd * and q-axis voltage command Vq * are calculated.

  The coordinate converter 50 performs coordinate conversion from the dq coordinate system to the uvw coordinate system on the d-axis voltage command Vd * and the q-axis voltage command Vq * output from the voltage command generation unit 40. By this coordinate conversion, voltage commands Vu *, Vv *, Vw * in the uvw coordinate system are obtained. Note that the phase θ (rotor position) used in this coordinate conversion is calculated by a θ calculator 90 described later.

  The PWM control unit 60 generates a gate signal SG for controlling the switching element of the inverter 10 according to the voltage commands Vu *, Vv *, Vw * output from the coordinate converter 50. At this time, the PWM control unit 60 generates the gate signal SG by PWM (Pulse Width Modulation) control. The gate signal SG is supplied to the inverter 10.

  The position / speed estimation unit 70 is a functional block that estimates the position and speed of the rotor by software based on current and voltage in sensorless vector control. More specifically, the position / velocity estimation unit 70 receives the d-axis detection current id and the q-axis detection current iq output from the coordinate converter 30 described above. Further, the position / speed estimation unit 70 receives the d-axis voltage command Vd * and the q-axis voltage command Vq * output from the voltage command generation unit 40 described above. Then, the position / speed estimation unit 70 determines the rotor position (phase) by a known algorithm based on the d-axis detection current id, the q-axis detection current iq, the d-axis voltage command Vd *, and the q-axis voltage command Vq *. And estimate the speed. The position of the rotor estimated by the position / speed estimation unit 70 is hereinafter referred to as “estimated phase θe”. The rotor speed estimated by the position / speed estimation unit 70 is hereinafter referred to as “estimated speed ωe”.

  The switching control unit 80 outputs a switching signal SW for switching the drive control method by the control device 1. More specifically, the switching control unit 80 changes the switching signal SW according to the motor speed. For example, the switching control unit 80 refers to the speed command ω *. When the speed command ω * is in the low speed region R1, the switching control unit 80 outputs a switching signal SW (for example, H level) that designates “synchronous control”. On the other hand, when the speed command ω * is in the high speed region R2, the switching control unit 80 outputs a switching signal SW (for example, L level) that designates “sensorless vector control”.

  The θ calculator 90 calculates a phase θ used in coordinate conversion. In the present embodiment, the method of calculating the phase θ differs depending on whether the control is synchronous or sensorless vector control. Therefore, the above-described switching signal SW is input to the θ calculation unit 90. When the switching signal SW designates synchronous control, the θ calculator 90 calculates the phase θ by integrating the speed command ω *. On the other hand, when the switching signal SW designates sensorless vector control, the θ calculation unit 90 calculates the phase θ by a known algorithm based on the estimated phase θe obtained by the position / velocity estimation unit 70 described above. .

  The current command generation unit 100 generates a d-axis current command id * and a q-axis current command iq * based on the speed command ω *. More specifically, the current command generation unit 100 includes a first current command generation unit 110, a second current command generation unit 120, and a selector 130.

  The first current command generator 110 generates the d-axis current command id * and the q-axis current command iq * for synchronous control, that is, the first d-axis current command id1 * and the first q-axis current command iq1 * described above. The first current command generator 110 sets the first q-axis current command iq1 * to zero (iq1 * = 0).

  According to the present embodiment, the first d-axis current command id1 * is set as in the above equation (1). That is, the first current command generation unit 110 sets the first d-axis current command id1 * to a value corresponding to the speed change (dω * / dt). More specifically, at a constant speed, the first current command generation unit 110 sets the first d-axis current command id1 * to the fixed d-axis current command id0 * (id1 * = id0 *). On the other hand, at the time of acceleration / deceleration, the first current command generation unit 110 sets the first d-axis current command id1 * to a corrected d-axis current command id0 ′ * larger than the fixed d-axis current command id0 * (id1 * = id0). '*).

  The corrected d-axis current command id0 ′ * may be applied only to one of acceleration or deceleration. For example, the first current command generation unit 110 may set the first d-axis current command id1 * to the corrected d-axis current command id0 ′ * only during acceleration.

  The second current command generation unit 120 generates a d-axis current command id * and a q-axis current command iq * for sensorless vector control. The d-axis current command id * and the q-axis current command iq * in the sensorless vector control are referred to as a second d-axis current command id2 * and a second q-axis current command iq2 *, respectively. The second current command generation unit 120 generates a second d-axis current command id2 * and a second q-axis current command iq2 * by a known algorithm based on the speed command ω *.

  In particular, the second current command generation unit 120 includes a speed controller 125. The speed controller 125 generates the second q-axis current command iq2 * based on the “estimated speed ωe” obtained by the position / speed estimation unit 70 described above. More specifically, the speed controller 125 calculates the second q-axis current command iq2 * by proportional integral control so that the estimated speed ωe matches the speed command ω *. Thus, in sensorless vector control, speed control and torque control are performed based on the estimated speed ωe.

  The selector 130 switches between the d-axis current command id * and the q-axis current command iq * output from the current command generation unit 100 according to the switching signal SW (that is, the speed command ω *). Specifically, when the switching signal SW designates synchronous control, the selector 130 selects the first d-axis current command id1 * and the first q-axis current command iq1 * generated by the first current command generation unit 110, Select and output as d-axis current command id * and q-axis current command iq *. On the other hand, when the switching signal SW designates sensorless vector control, the selector 130 sets the second d-axis current command id2 * and the second q-axis current command iq2 * generated by the second current command generation unit 120 to d, respectively. Select and output as axis current command id * and q-axis current command iq *.

  The inverter 10, the current detector 20, the coordinate converter 30, the voltage command generation unit 40, the coordinate converter 50, the PWM control unit 60, the position / speed estimation unit 70, the switching control unit 80, the θ calculation unit 90, and the current The command generation unit 100 constitutes a “control unit” as a whole. This control unit performs drive control of the synchronous motor SM by synchronous control in the low speed region R1. In the case of synchronous control, the frequency of the output current of the inverter 10 (that is, the rotational speed of the rotor) matches the speed command ω *. On the other hand, in the high-speed region R2, the control unit performs drive control of the synchronous motor SM by sensorless vector control.

  With the configuration described above, the drive control shown in FIG. 3 is realized. During acceleration / deceleration in the low speed region R1, the first d-axis current command id1 * is set to a corrected d-axis current command id0 '* that is larger than the fixed d-axis current command id0 *. As a result, the maximum torque that can be output temporarily increases, and torque shortage and thus step-out are prevented.

Embodiment 2. FIG.
In the second embodiment, an example of the first current command generation unit 110 will be described. FIG. 5 is a block diagram showing a configuration of first current command generation unit 110 in the second embodiment. FIG. 6 is a graph showing the operation of the first current command generator 110 in the second embodiment.

  The first current command generator 110 shown in FIG. 5 includes an adder 111 and a correction value generator 112. The adder 111 generates the first d-axis current command id1 * by adding the correction value id ** to the fixed d-axis current command id0 *. The correction value id ** is generated by the correction value generation unit 112.

  The correction value generation unit 112 shown in FIG. The selector 113 outputs zero or a fixed value as a correction value id ** according to the acceleration / deceleration (dω * / dt).

  Specifically, at a constant speed (dω * / dt = 0), the selector 113 outputs zero (id ** = 0). This means that no correction is performed. That is, the first current command generation unit 110 outputs the fixed d-axis current command id0 * as the first d-axis current command id1 * (id1 * = id0 *).

  On the other hand, at the time of acceleration / deceleration, the selector 113 outputs a fixed value larger than zero as the correction value id **. In this case, the correction value id ** (fixed value> 0) is added to the fixed d-axis current command id0 *, and the corrected d-axis current command id0 '* is calculated. That is, the first current command generation unit 110 outputs a corrected d-axis current command id0 '* larger than the fixed d-axis current command id0 * as the first d-axis current command id1 * (id1 * = id0' *).

  The fixed value used as the correction value id ** is determined in advance in consideration of the insufficient torque that can be generated.

Embodiment 3 FIG.
In the third embodiment, another example of the first current command generation unit 110 will be described. FIG. 7 is a block diagram showing a configuration of first current command generation unit 110 in the third embodiment. FIG. 8 is a graph showing the operation of the first current command generator 110 in the third embodiment.

  Compared to the above-described second embodiment, the third embodiment differs in the function of the correction value generation unit 112. In the third embodiment, the correction value generation unit 112 sets the correction value id ** to a calculated value corresponding to the acceleration / deceleration torque, instead of a fixed value. More specifically, as illustrated in FIG. 7, the correction value generation unit 112 includes an acceleration / deceleration torque calculator 114 and a converter 115.

  The acceleration / deceleration torque calculator 114 calculates the acceleration / deceleration torque Ta according to the following equation (2). Here, the parameter J is the moment of inertia of the stator of the synchronous motor SM. The parameter dω * / dt is a time differential value of the speed command ω *, that is, “acceleration / deceleration”. The acceleration / deceleration torque calculator 114 calculates the acceleration / deceleration torque Ta based on the acceleration / deceleration and the moment of inertia J.

  Formula (2): Ta = | J × (dω * / dt) |

  The converter 115 converts the acceleration / deceleration torque Ta into a correction value id ** according to the following equation (3). Here, Tm is a rated torque and im is a rated current. The parameter Ta / Tm is the ratio of the acceleration / deceleration torque Ta to the rated torque Tm, that is, the “torque load factor”. The converter 115 calculates a correction value id ** corresponding to the acceleration / deceleration torque Ta by multiplying the rated current im by a torque load factor.

  Formula (3): id ** = im × (Ta / Tm)

  As described above, in the third embodiment, the correction value generation unit 112 calculates the correction value id ** by calculation based on the generated acceleration / deceleration torque. As a result, the maximum torque is corrected by a necessary amount according to the acceleration / deceleration torque. That is, the efficiency of torque correction is improved.

Embodiment 4 FIG.
In the fourth embodiment, still another example of the first current command generation unit 110 will be described. FIG. 9 is a block diagram showing a configuration of first current command generation unit 110 in the fourth embodiment. FIG. 10 is a graph showing the operation of the first current command generator 110 in the fourth embodiment.

  As in the case of the third embodiment described above, the correction value generation unit 112 of the fourth embodiment sets the correction value id ** to a calculated value corresponding to the acceleration / deceleration torque. However, in the calculation of acceleration / deceleration torque, the correction value generation unit 112 of the fourth embodiment uses a model of the synchronous motor SM. More specifically, as illustrated in FIG. 9, the correction value generation unit 112 includes a subtractor 116, a model speed controller 117, a model speed calculator 118, and a converter 115.

  The subtractor 116 calculates a difference (ω * −ωmdl) between the speed command ω * and the model speed ωmdl. The difference (ω * −ωmdl) is input to the model speed controller 117.

  The model speed controller 117 calculates the acceleration / deceleration torque Ta according to the following equation (4). Here, the parameter J is the moment of inertia of the stator of the synchronous motor SM. The parameter Kp is the gain of the model.

  Formula (4): Ta = Kp × J × (d (ω * −ωmdl) / dt)

  The model speed calculator 118 calculates the model speed ωmdl from the acceleration / deceleration torque Ta according to the following equation (5).

  Formula (5): ωmdl = ∫ (| Ta | / J)

  The calculated model speed ωmdl is fed back to the subtractor 116 to form a speed loop. Thus, the acceleration / deceleration torque Ta is calculated by inputting the speed command ω * to the model of the synchronous motor SM. The calculated acceleration / deceleration torque Ta is input to the converter 115. The function of converter 115 is the same as that in the third embodiment.

  Thus, in the present embodiment, the motor model is used for calculating the acceleration / deceleration torque Ta. Therefore, as shown in FIG. 10, the corrected d-axis current command id0 '* is not a step shape but a first-order lag command. As a result, the strength of speed fluctuation due to current change is alleviated.

Embodiment 5 FIG.
In the fourth embodiment, the model speed ωmdl is calculated. At this time, as shown in FIG. 11, the model speed ωmdl may be used for calculation of the phase θ in the θ calculation unit 90 instead of the speed command ω *. Similar to the corrected d-axis current command id0 ′ *, the model speed ωmdl is also a first-order lag system, so the strength of the speed fluctuation is further reduced.

Embodiment 6 FIG.
FIG. 12 is a block diagram showing a configuration of first current command generation unit 110 in the sixth embodiment. The first current command generation unit 110 shown in FIG. 12 is a modification of the above-described second to fifth embodiments, and can be applied to any of the second to fifth embodiments.

  As shown in FIG. 12, a mask circuit 119 is provided between the output of the correction value generation unit 112 and the adder 111. The mask circuit 119 outputs the correction value id ** to the adder 111 only when designated by the designation signal DES, that is, validates the correction process (id1 * = id0 ′ *). In other cases, the mask circuit 119 does not output the correction value id **, that is, invalidates the correction process.

  The designation signal DES designates “only during acceleration”, “only during deceleration”, or “both during acceleration and deceleration”. For example, when the designation signal DES designates “only during acceleration”, the mask circuit 119 validates the correction process only during acceleration, and invalidates the correction process otherwise. Determination at the time of acceleration or deceleration can be made based on the speed command ω *.

  For example, the content of the designation signal DES may be fixed by using a fuse circuit or the like at the initial setting. Alternatively, the contents of the designation signal DES may be changeable from the outside as necessary. In either case, flexible mounting according to the usage environment of the synchronous motor SM is possible.

  The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above-described embodiments, and can be appropriately changed by those skilled in the art without departing from the scope of the invention.

  DESCRIPTION OF SYMBOLS 1 Control apparatus, 10 inverter, 20 Current detector, 30 Coordinate converter, 40 Voltage command production | generation part, 50 Coordinate converter, 60 PWM control part, 70 Position / speed estimation part, 80 Switching control part, 90 (theta) calculating part, 100 current command generation unit, 110 first current command generation unit, 111 adder, 112 correction value generation unit, 113 selector, 114 acceleration / deceleration torque calculator, 115 converter, 116 subtractor, 117 model speed controller, 118 model Speed calculator, 119 mask circuit, 120 second current command generator, 125 speed controller, 130 selector, DES designation signal, R1 low speed area (first speed area), R2 high speed area (second speed area), SG gate Signal, SM synchronous motor, SW switching signal.

Claims (10)

A control device for a synchronous motor,
A controller that performs drive control of the synchronous motor by synchronous control in a first speed region, and that performs drive control of the synchronous motor by sensorless vector control in a second speed region that is higher than the first speed region;
A current command generation unit included in the control unit for generating a d-axis current command and a q-axis current command for the drive control;
In the case of the synchronous control, the current command generation unit sets the q-axis current command to zero, sets the d-axis current command to a value according to the state of speed change,
At a constant speed in the first speed region, the current command generator sets the d-axis current command to a first value that is a fixed value,
The control device, wherein at least one of acceleration and deceleration in the first speed region, the current command generation unit sets the d-axis current command to a second value larger than the first value. The current command generator is
A first current command generator for generating the d-axis current command and the q-axis current command in the case of the synchronous control;
A second current command generator for generating the d-axis current command and the q-axis current command in the case of the sensorless vector control;
Based on the speed command, the d-axis current command and the q-axis current command generated by the first current command generation unit are selected in the case of the first speed range, and the second speed range is selected in the case of the second speed range. A selector that selects the d-axis current command and the q-axis current command generated by a current command generation unit;
At a constant speed in the first speed region, the first current command generator sets the d-axis current command to the first value,
2. The control according to claim 1, wherein the first current command generation unit sets the d-axis current command to the second value during at least one of acceleration and deceleration in the first speed region. apparatus.   The control device according to claim 2, wherein the first current command generation unit generates the second value by adding a correction value to the first value.   The control device according to claim 3, wherein the correction value is a predetermined value.   The control device according to claim 3, wherein the first current command generation unit sets the correction value to a magnitude corresponding to acceleration / deceleration torque.   The control according to claim 5, wherein the first current command generation unit calculates the acceleration / deceleration torque based on a time differential value of the speed command and an inertia moment of a rotor of the synchronous motor. apparatus.   The control device according to claim 5, wherein the first current command generation unit calculates the acceleration / deceleration torque by inputting the speed command to a model of the synchronous motor.   The control device according to any one of claims 1 to 7, wherein the current command generation unit sets the d-axis current command to the second value at least during acceleration in the first speed region. . A designation signal that designates either only during acceleration, only during deceleration, or both during acceleration and deceleration is input to the current command generation unit,
The control device according to any one of claims 1 to 7, wherein the current command generation unit sets the d-axis current command to the second value when designated by the designation signal. . A control method for a synchronous motor,
Performing drive control of the synchronous motor by synchronous control in a first speed region;
Performing drive control of the synchronous motor by sensorless vector control in a second speed region higher than the first speed region,
The step of performing the drive control by the synchronous control includes a step of setting a q-axis current command to zero and a d-axis current command to a value according to a state of speed change,
The step of setting the d-axis current command includes:
Setting the d-axis current command to a first value which is a fixed value at a constant speed in the first speed region;
And a step of setting the d-axis current command to a second value larger than the first value at least during acceleration or deceleration in the first speed region.

Images