JP2013192396A - Motor drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reliable motor drive device capable of appropriately controlling a speed of a motor without influence of variation of an inductance of the motor.SOLUTION: A value of an inductance of a motor is selected within a pre-stored selection range. The selected value of the inductance is used for estimation of a rotor speed, and the value of the inductance is sequentially searched and amended within the selection range to reduce a difference between an estimated rotor speed and a target speed.

Description

  Embodiments described herein relate generally to a motor driving apparatus that drives a permanent magnet synchronous motor.

  A motor drive device for driving a permanent magnet synchronous motor (also referred to as a brushless DC motor) comprising a stator having a plurality of phase windings and a rotor having a plurality of permanent magnets includes an inverter for supplying power to each phase winding, At startup, each phase winding is DC-excited to position the rotor, and then the field component current (d-axis current) Id converted to the field axis (d-axis) coordinates on the rotor axis is set for each phase. Apply to the winding to perform forced commutation. After the start-up is completed, the current (phase current) flowing in each phase winding is detected, the rotor speed (= angular speed) is estimated based on the detection result, and the inverter is operated so that the estimated rotor speed becomes the target speed. So-called sensorless vector control is performed.

  In this sensorless vector control, the inductance of a permanent magnet synchronous motor, which is predetermined as a motor constant, is used to estimate the rotor speed and rotor position.

JP 2006-340530 A JP 2003-348899 A

  The inductance of a permanent magnet synchronous motor changes due to the influence of manufacturing variations of individual motors, installation environment, operating conditions, aging, and the like. If this variation in inductance is ignored, the rotor speed cannot be controlled appropriately, and the operation performance of the permanent magnet synchronous motor cannot be fully exhibited.

  An object of an embodiment of the present invention is to provide a highly reliable motor drive device that can appropriately control the speed of a motor without being affected by variations in inductance of the motor.

  The motor driving device according to claim 1 converts an alternating voltage into a direct current, converts the direct current voltage into an alternating current by switching, and outputs it as a driving voltage to the motor, and a field component current and a torque component current in the motor. Detection means for detecting, first control means, and second control means. The first control means estimates the rotor speed of the motor based on at least the detection current of the detection means and the inductance of the motor, and controls switching of the inverter so that the estimated rotor speed becomes a target speed. The second control means is configured to control the inductance corresponding to the detection current of the detection means within a selection range including a selection upper limit value and a selection lower limit value of the inductance value associated with the field component current or the torque component current. An appropriate value is selected, and the selected appropriate value is used as the inductance value for estimation of the rotor speed by the first control means, and the appropriate value used for the estimation is small in deviation between the estimated rotor speed and the target speed. In this direction, the search is sequentially performed within the selected range and corrected.

The block diagram which shows the structure of 1st and 3rd embodiment. The graph for demonstrating the data table of the selection range of the inductance of each embodiment. The flowchart which shows the process of the estimation calculating part of 1st Embodiment. The figure which shows the search of the appropriate value of 1st Embodiment. The figure which shows another example of the search of the appropriate value of 1st Embodiment. The figure which shows the specific example of the search of the downward direction of the appropriate value of 1st Embodiment. The figure which shows another specific example of the search of the downward direction of the appropriate value of 1st Embodiment. The figure which shows the specific example of the search of the raise direction of the appropriate value of 1st Embodiment. The figure which shows the function data showing the selection range of the inductance of each embodiment as a function of an electric current. The block diagram which shows the structure of 2nd Embodiment. The flowchart which shows the process of the estimation calculating part of 3rd Embodiment. The figure which shows the specific example of the search of the downward direction of the appropriate value of 3rd Embodiment. The figure which shows the specific example of the search of the raise direction of the appropriate value of 3rd Embodiment.

[1] A first embodiment will be described below with reference to the drawings.
The motor driving device drives a permanent magnet synchronous motor (also referred to as a brushless DC motor) used as a driving motor for a compressor or a fan, and has the configuration shown in FIG.

  Reference numeral 10 denotes a commercial AC power supply. The AC voltage of the commercial AC power supply 10 is converted into a DC voltage by the rectifier circuit 11, and the DC voltage is applied to the smoothing capacitor 12. The voltage of the smoothing capacitor 12 is converted into an AC voltage having a predetermined frequency by switching of the switching circuit 13. The output of the switching circuit 3 is supplied as drive power to the permanent magnet synchronous motor 20. The rectifier circuit 11, the smoothing capacitor 12, and the switching circuit 13 constitute an inverter.

  The permanent magnet synchronous motor 20 includes four permanent magnets as an input terminal 21 connected to the output terminal of the inverter, a stator (armature) 22 having a plurality of phase windings Lu, Lv, and Lw, and a plurality of, for example, two-pole motors. Has a rotor (rotor) 23 embedded therein.

  The switching circuit 13 is a circuit in which two switching elements each having a reverse diode connected in reverse parallel are connected in series, and the series circuit is provided for three phases. A connection point between the side switching element and the negative side switching element is connected to each phase winding of the permanent magnet synchronous motor 20. The U-phase energization path, V-phase energization path, and W-phase energization path between the output terminal of the switching circuit 13 and the input terminal 21 of the permanent magnet synchronous motor 20 flow to the phase windings Lu, Lv, and Lw of the permanent magnet synchronous motor 20. Current transformers 31, 32, and 33, which are current sensors for detecting current (phase current), are provided. Outputs of the current transformers 31, 32, and 33 are supplied to the MCU 40 that functions as a motor control unit.

  The MCU 40, which is a control unit, controls the switching of the inverter by sensorless vector control in accordance with a target speed (also referred to as a command speed) ωref commanded from the control unit of the air conditioner. (1) to (3) are included.

  (1) From the current values for the three phases detected by the current transformers 31, 32, 33, to the field axis (d axis) coordinates and the torque axis (q axis) coordinates on the rotor axis in the permanent magnet synchronous motor 20, respectively. Detection means for detecting the converted field component current (also referred to as d-axis current) Id and torque component current (also referred to as q-axis current) Iq.

  (2) The rotor speed ωest of the permanent magnet synchronous motor 20 is estimated based on at least the detection current of the detection means and the inductance of the permanent magnet synchronous motor 20, and the inverter speed is set so that the estimated rotor speed ωest becomes the target speed ωref. First control means for controlling switching.

  (3) With respect to the inductance value of the permanent magnet synchronous motor 20, the detection means is within a preset selection range consisting of a selection upper limit value and a selection lower limit value of the inductance value associated with the field component current or the torque component current. The appropriate value of the inductance corresponding to the detected current is selected, and the selected appropriate value is used as the actual value of the permanent magnet synchronous motor 20 for the estimation of the rotor speed ωest by the first control means, and the appropriate value for the estimation Second control means for successively searching for and correcting the difference between the estimated rotor speed ωest and the target speed ωref within the selected range in a direction in which the deviation is reduced.

  Specifically, the MCU 40 has a current detection unit 41 that functions as the detection unit, and an estimation calculation unit 42, an integration unit 43, a subtraction unit 44, and PI control that function as the first and second control units. A unit 45, a subtracting unit 46, a calculating unit 47, a subtracting unit 48, a PI control unit 49, a PI control unit 50, a PWM signal generating unit 51, and a storage unit 52.

  The current detection unit 41 detects the field component current Id and the torque component current Iq by calculation based on the detected currents of the current transformers 31, 32, 32 and the estimated rotor position θest supplied from the integration unit 43. This detection result is supplied to the estimation calculation unit 42. The estimation calculation unit 42 estimates the rotor speed ωest of the permanent magnet synchronous motor 20 by calculation based on the field component current Id, the torque component current Iq, the field component voltage Vd and the torque component voltage Vq described later. This estimated rotor speed ωest is supplied to the integration unit 43 and the subtraction unit 44.

  The integrating unit 43 obtains the estimated rotor position θest by integrating the estimated rotor speed ωest. The estimated rotor position θest is supplied to the current detection unit 41 and the PWM signal generation unit 51. The subtracting unit 44 subtracts the estimated rotor speed ωest from the target speed ωref input from the outside. This subtraction result is supplied to the PI control unit 45 as the speed deviation amount ωerr. The PI control unit 45 obtains a target value Iqref of the torque component current Iq by performing a proportional / integral calculation on the speed deviation amount ωerr. This target value Iqref is supplied to the subtraction unit 46 and the calculation unit 47.

  The computing unit 47 converts the target value Iqref to the target value Idref of the field component current Id. This target value Idref is supplied to the subtraction unit 48. The subtraction unit 48 subtracts the field component current Id from the target value Idref. A current difference ΔId obtained by this subtraction is supplied to the PI control unit 49. The PI control unit 49 obtains a field component voltage Vd converted into a d-axis coordinate on the rotor axis in the permanent magnet synchronous motor 20 by performing a proportional / integral calculation on the current difference ΔId. This field component voltage Vd is supplied to the estimation calculation unit 42 and the PWM signal generation unit 51. The subtracting unit 46 subtracts the torque component current Iq from the target value Iqref. A current difference ΔIq obtained by this subtraction is supplied to the PI control unit 50. The PI control unit 50 obtains a torque component voltage Vq converted to a q-axis coordinate on the rotor shaft in the permanent magnet synchronous motor 20 by performing a proportional / integral calculation on the current difference ΔIq. This torque component voltage Vq is supplied to the estimation calculation unit 42 and the PWM signal generation unit 51.

  The PWM signal generation unit 51 generates drive voltages Vu, Vv, and Vw for the respective phase windings of the permanent magnet synchronous motor 20 based on the input estimated rotor position θest, field component voltage Vd, and torque component voltage Vq. The PWM signal necessary for output from the is generated. With this PWM signal, each switching element of the switching circuit 13 is driven on and off.

In such sensorless vector control of the MCU 40, the field component voltage Vd and the torque component voltage Vq are expressed by the following equations.
Vd = (R + PLd) · Id−ω · Lq · Iq + Ed
Vq = ω · Ld · Id + (R + PLq) · Iq + Eq
R is the armature resistance, P is the differential (= d / dt), ω is the electric rotational speed of the motor shaft, Lq is the q-axis inductance of the stator 22, Ed is the induced voltage of the d-axis, and Ld is the d-axis of the stator 22. The inductance, Eq, is an induced voltage (= ω · φ) on the q axis. Note that the armature resistance is twice the value of the resistance of one phase winding when the output of the inverter is three-phase modulation, or in the case of a one-phase (lower phase) 100% energization method with two-phase modulation, Since the lower side is parallel as the energization pattern for the winding, a value 1.5 times the resistance of one phase winding is used.

Since PLd and PLq are differential terms, they are zero in a steady state. In sensorless vector control, each phase winding current (armature current) is controlled on the basis of the field axis (d-axis), so the induced voltage Ed on the d-axis is basically controlled to be zero. The
Vd = R · Id−ω · Lq · Iq
ω = (R · Id−Vd) / (Lq · Iq)
Vq = ω · Ld · Id + R · Iq + ω · φ
Vq−R · Iq = ω · Ld · Id + ω · φ
ω · (Ld · Id + φ) = Vq−R / Iq
ω = (Vq−R · Iq) / (Ld · Id + φ)
The estimated rotor speed ωest is calculated in the estimated calculation unit 42 so that the d-axis circuit equation holds. On the other hand, the d-axis induced voltage Ed is basically controlled to be zero, but the q-axis inductance Lq and the d-axis inductance Ld of the stator 22 which are parameters for calculating the estimated rotor speed ωest are actual values. The induced voltage Ed on the d axis does not become zero. The d-axis induced voltage Ed can be obtained as the estimated value Ed ^ as follows.
Ed ^ = Vd− (Id · R−ωest · Iq · Lq)
The speed deviation amount ωerr can be estimated by PI control of the estimated value Ed ^.
ωerr = PI (Ed ^)
The storage unit 52 is, for example, a rewritable nonvolatile memory, and stores the initial values Lq and Ld of the q-axis inductance Lq and the d-axis inductance Ld inherent to the permanent magnet synchronous motor 20 as motor constants. The correspondence between the initial appropriate value Lq-ref of the shaft inductance Lq and the torque component current Iq and the correspondence between the initial appropriate value Ld-ref of the d-axis inductance Ld and the field component current Id are stored as motor constants. The selection range of inductance shown in 2 is stored. The selection range of this inductance is the selection upper limit value Lq-high (= initial appropriate value Lq-ref + Lqa) and the selection lower limit value Lq-low (= initial appropriate value) of the appropriate value Lq-ref of the q-axis inductance Lq of the permanent magnet synchronous motor 20. Value Lq−ref−Lqb) is associated with torque component current Iq, and upper limit Ld−high (= initial appropriate value Ld−ref + Lda) and selection of appropriate value Ld−ref of d-axis inductance Ld of permanent magnet synchronous motor 20 and selection It is a data table in which the lower limit value Ld-low (= the initial appropriate value Ld-ref-Ldb) is associated with the field component current Id. That is, the appropriate value Lq-ref of the q-axis inductance Lq is selected between the selection upper limit value Lq-high and the selection lower limit value Lq-low determined by the torque component current Iq. Similarly, the appropriate value Ld-ref of the d-axis inductance Ld is selected between a selection upper limit value Ld-high and a selection lower limit value Ld-low determined by the field component current Id. The initial appropriate value Lq-ref of the q-axis inductance Lq is the center value of the selection upper limit value Lq-high and the selection lower limit value Lq-low, and the initial appropriate value Ld-ref of the d-axis inductance Ld is the upper limit of selection. The center value of the value Ld-high and the selection lower limit Ld-low is used.

  Initially, the operation using the initial values Ld and Ld in the storage unit 52 as the q-axis inductance Lq and the d-axis inductance Ld is started, and then the initial appropriate value Lq-ref in the storage unit 52 as the first appropriate value. Ld-ref is selected, but during operation, an appropriate appropriate value Lq-ref is selected within the selection range of the selection upper limit value Lq-high and the selection lower limit value Lq-low, as will be described later. An appropriate appropriate value Lq-ref is selected within the selection range of the upper limit value Ld-high and the selection lower limit value Ld-low. The initial value Lq-ref is naturally between the selection upper limit value Lq-high and the selection lower limit value Lq-low, and the initial value Ld-ref is naturally the selection upper limit value Ld-high and the selection lower limit value Ld-low. It is between low.

  Selection range of appropriate values of q-axis inductance Lq, that is, correspondence between values of selection upper limit value Lq-high and selection lower limit value Lq-low and torque component current Iq, and selection range of appropriate value of d-axis inductance Ld, In other words, the correspondence between the selection upper limit value Ld-high and the selection lower limit value Ld-low and the field component current Id is not based on an experiment based on the variation range of elements such as variations in the drive motor and operating temperature range. Is confirmed in advance.

  Comparing the q-axis inductance Lq and the d-axis inductance Ld, the q-axis inductance Lq is generally larger than the d-axis inductance Ld in a motor having reverse saliency, such as an embedded permanent magnet synchronous motor. Further, the q-axis inductance Lq has a larger change due to the current than the d-axis inductance Ld. Accordingly, it can be said that the influence on the sensorless vector control in the embedded permanent magnet synchronous motor is greater in the q-axis inductance Lq than in the d-axis inductance Ld. For this reason, it is desirable to give priority to selecting the optimum value of the q-axis inductance Lq.

  The estimation calculation unit 42 executes the process shown in the flowchart of FIG.

  That is, when the permanent magnet synchronous motor 20 is started (YES in Step 101), the rotor speed is calculated by using the initial value Lq of the q-axis inductance Lq and the initial value Ld of the d-axis inductance Ld, which are motor constants in the storage unit 52. ωest is estimated (step 102). Subsequently, the initial appropriate value Lq-ref of the q-axis inductance Lq of the permanent magnet synchronous motor 20 is obtained by referring to the selection range of the inductance in the storage unit 52 based on the torque component current Iq that is the detection current of the current detection unit 41. Is selected (step 103), and the estimation calculation of the rotor speed ωest is continued using the selected initial appropriate value Lq-ref as the actual value of the q-axis inductance Lq (step 104). For the d-axis inductance Ld necessary for the estimation calculation, the motor constant in the storage unit 52 is used as it is.

Subsequently, the field component voltage Vd, the field component current Id, the armature resistance R, the estimated rotor speed ωest, the torque component current Iq, and the appropriate value Lq-ref (the initial appropriate value and then the updated value) are used. An estimated value Ed ^ of the induced voltage Ed is obtained by the calculation of the following equation (step 105).
Ed ^ = Vd- (Id.R-.omega.est.Iq.Lq-ref)
Then, as shown in FIGS. 4 and 5, the appropriate value Lq-ref is so-called hill-climbed in the direction in which the obtained estimated value Ed ^ decreases, that is, in the direction in which the difference ωerr between the estimated rotor speed ωest and the target speed ωref decreases. The search is sequentially performed in the manner of the law (step 106). Specifically, the appropriate value Lq-ref (= the appropriate value Lq-ref + Δl at that time), which is a value increased by a slight value (Δl) with respect to the appropriate value Lq-ref at that time, is output, and the result When the estimated value Ed ^ becomes smaller, the output of Lq-ref (= the appropriate value Lq-ref + Δl at that time) further increased by Δl is repeated. On the other hand, when Ed ^ increases, the output of the appropriate value Lq-ref (= the appropriate value Lq-ref-Δl at that time) decreased by Δl is repeated. By repeating this, it is possible to find an appropriate value Lq-ref that minimizes the estimated value Ed ^. That is, the appropriate value Lq-ref is slightly changed in either the + or − direction, and as a result, if the speed deviation amount ωerr (Ed ^) is reduced, the appropriate value Lq-ref is further changed in that direction. Conversely, if the speed deviation amount ωerr (Ed ^) increases, the appropriate value Lq-ref is changed in the reverse direction, and finally the appropriate value Lq− where the speed deviation amount ωerr (Ed ^) becomes the smallest. Repeatedly change the inductance value until ref.

  4 and 5, search results in the same torque component current Iq current and field component current Id state are indicated as Lqx, and the transition of the search result Lqx is indicated by an arrow. FIG. 4 shows an example in which the search result Lqx moves to a lower side than the initial appropriate value Lq-ref, and FIG. 5 shows an example in which the search result Lqx moves to a higher side than the initial appropriate value Lq-ref.

  In the inductance selection range of FIG. 2, the selection upper limit value Lq-high and the selection lower limit value Lq-low of the appropriate value Lq-ref are, as shown in an enlarged view in FIG. 6, for each predetermined width Iqa of the torque component current Iq. It is set stepwise, and a rectangular selection range is formed for each predetermined width. Similarly, the selection upper limit value Ld-high and the selection lower limit value Ld-low of the appropriate value Ld-ref are set stepwise for each predetermined width Ida of the field component current Id, and a rectangular shape is selected for each predetermined width. Form a range.

  When the search result Lqx moves in the downward direction simultaneously with the increase of the torque component current Iq as shown in FIG. 6, if the new search result Lqx exists in any of the selection ranges (YES in step 107), the new The current search result Lqx is used as the current search result as it is, and is used as the updated value of the appropriate value Lq-ref (step 108), and the current search result Lqx is used as the start point of the next search (step 109).

  However, when the search result Lqx moves in the downward direction, as shown in FIG. 7, when the new search result Lqx exceeds the selection upper limit Lq-high of another selection range (NO in step 107). In step 111, the selection upper limit Lq-high in the vicinity of the new search result Lqx is used as the current search result, and this is used as the updated value of the appropriate value Lq-ref (step 112). The selection upper limit Lq-high as a result is set as the start point of the next search (step 113).

  As shown in FIG. 8, when the search result Lqx moves in the upward direction simultaneously with the decrease of the torque component current Iq, the new search result Lqx is below the selection lower limit value Lq-low of the other selection range. (NO in step 107, NO in step 111), the selection lower limit Lq-low in the vicinity of the new search result Lqx is used as the current search result and is used as the updated value of the appropriate value Lq-ref (step 114). The selection lower limit Lq-low, which is the current search result, is set as the start point of the next search (step 115).

  If the permanent magnet synchronous motor 20 continues to be driven (NO in step 110), the estimation calculation using the updated value of the appropriate value Lq-ref is continued (step 104). Then, when the permanent magnet synchronous motor 20 is stopped (YES in Step 110), the processing is ended.

  The q-axis inductance Lq and the d-axis inductance Ld of the permanent magnet synchronous motor 20 change due to the influence of individual motor manufacturing variations, installation environment, operating conditions, aging, and the like. If the variations in the q-axis inductance Lq and the d-axis inductance Ld are ignored, the rotor speed of the permanent magnet synchronous motor 20 cannot be appropriately controlled, and the operation performance of the permanent magnet synchronous motor 20 cannot be fully exhibited. Things will happen.

  As described above, the proper value Lq-ref of the q-axis inductance Lq is sequentially searched in the direction in which the estimated value Ed ^ of the induced voltage Ed decreases, that is, in the direction in which the deviation between the estimated rotor speed ωest and the target speed ωref decreases. However, even if the q-axis inductance Lq varies, the optimum q-axis inductance Lq can be selected and the rotor speed of the permanent magnet synchronous motor 20 can be controlled appropriately. Thereby, the operation performance of the permanent magnet synchronous motor 20 can be fully exhibited. Reliability as a motor drive device is also improved. In addition, since the upper limit and lower limit are set in the selection of appropriate values, the inductance value is selected within the range of the upper limit and lower limit, and some abnormality or the like has occurred in this motor or winding. Sometimes an inductance with an abnormal value is not selected.

  Since the initial appropriate value Lq-ref and the selection range of the inductance in the storage unit 52 can be rewritten, the permanent magnet synchronous motor can be adapted to any changes such as repair or replacement of the permanent magnet synchronous motor 20 as a load. A high driving performance of 20 can be maintained.

  In the above embodiment, only the appropriate value Lq-ref of the q-axis inductance Lq that has a great influence on the sensorless vector control is selected, searched, and corrected. An appropriate value Ld-ref of the d-axis inductance Ld may be selected, searched, and corrected. When both the q-axis and d-axis inductances are corrected simultaneously, convergence becomes difficult. First, in the state where the torque component current Iq is within the range, an appropriate value Lq-ref of the q-axis inductance Lq is searched and this is appropriate. When the q-axis inductance Lq is fixed to the appropriate value Lq-ref after the convergence to a certain range and then the appropriate value Lq-ref of the d-axis inductance is searched, the search can be performed stably.

  In addition, although a data table was used as the inductance selection range, the initial appropriate value Lq-ref, the selection upper limit value Lq-high, the selection lower limit value Lq-low, the initial appropriate value Ld-ref, and the selection upper limit value in the inductance selection range. The function data of FIG. 9 representing the correspondence between Ld-high, the selection lower limit Ld-low and the currents Iq, Id as a function of the currents Iq, Id may be held instead of the database. This function is configured by an approximate curve equation that connects points plotted with appropriate values Lq-ref of appropriate q-axis inductance Lq obtained as a result of testing under standard conditions in accordance with changes in torque component current Iq. That is, the function of the initial appropriate value Lq-ref of the q-axis inductance Lq is a curve connecting the intersection of the torque component current Iq1 and the initial appropriate value Lq-ref2, and the intersection of the torque component current Iq2 and the initial appropriate value Lq-ref1. The selection upper limit value Lq-highn and the selection lower limit value Lq-lown in the specific torque component current Iqn are the initial appropriate value Lq-refn in the specific torque component current Iqn calculated by the function of the initial appropriate value Lq-ref. Can be calculated and held as a value obtained by adding a predetermined value Lqa and reducing production by Lqb, a selection upper limit value Lq-highn = Lq-refn + Lqa, and a selection lower limit value Lq-lown = Lq-refn-Lqb. Similarly, the initial appropriate value Ld-ref of the d-axis inductance Ld is also plotted as the appropriate value Ld-refn of the appropriate d-axis inductance Ld obtained as a result of testing under standard conditions according to the change in the field component current Id. Consists of approximate curve formulas connected. On this curve, the intersection of the field component current Id1 and the appropriate value Ld-ref2 and the field component current Id2 and the appropriate value Ld-ref1 are also located. Also in this case, the selection upper limit value Ld-highn and the selection lower limit value Ld-lown in the specific field component current Idn are the initial appropriate values in the specific field component current Idn calculated by the function of the initial appropriate value Ld-ref. The value Ld-refn is calculated and held at a value obtained by adding a predetermined value Lda and reducing production by Ldb. Note that these addition / subtraction values may be changed depending on the magnitudes of the currents Id and Iq.

[2] A second embodiment will be described.
In the second embodiment, the calculation parameter of the speed deviation amount which is an index of response by the hill-climbing method is changed from the first embodiment, and other configurations are the same as those of the first embodiment.

  As shown in FIG. 10, the current difference ΔIq (= target value Iqref−detected value Iq of torque component current) obtained by the subtraction of the subtraction unit 46 is supplied to the estimation calculation unit 42. The current difference ΔIq corresponds to the amount of deviation between the estimated rotor speed ωest and the target speed ωref.

  As shown in FIGS. 11 and 12, the estimation calculation unit 42 uses the current difference ΔIq instead of the estimated value Ed ^ of the first embodiment, and the direction in which the current difference ΔIq decreases, that is, the estimated rotor speed ωest and the target The appropriate value Lq-ref is sequentially searched in the manner of the so-called hill-climbing method so that the deviation from the speed ωref becomes smaller.

Except for the high-speed operation range where field-weakening control is required, only a small amount of field component current Id is injected in the normal low-speed to medium-speed operation range. Therefore, it is more convenient to use the current difference ΔIq between the target value Iqref and the torque component current Iq as an index of the motor speed deviation amount than to use the current difference ΔId between the target value Idref and the field component current Id. Is good.
Other configurations, controls, and effects are the same as those in the first embodiment. Therefore, the description is omitted.

[3] A third embodiment will be described.
The third embodiment is different from the first embodiment in a method of determining an initial appropriate value for starting a search in a situation where the torque component current Iq or the field component current Id is changing.

In the third embodiment, as shown in the flowchart of FIG. 11, the estimation calculation unit 42 performs the processes of steps 201 to 203 instead of the process of step 109 of the first embodiment.
That is, as shown in FIGS. 12 and 13, the new search result Lqx is set as the starting point of the next search within the same selection range (step 201), and the new search result Lqx is set as the final search result for each selection range. Lqxn is updated and stored in the storage unit 52 (step 202). If a torque component current Iq large enough to shift the selection range is generated, the final search result Lqxn already stored in the storage unit 52 in the new selection range is used as a search shift to the new selection range. The initial search value is selected as the initial appropriate value selected in step 103 when the permanent magnet synchronous motor 20 is started next time (step 203).

  FIG. 12 shows the search transition in the downward direction, and FIG. 13 shows the search transition in the upward direction of the search result Lqx.

  By using the final search result Lqxn, which is the final appropriate value selected in the past search for each selection range, as the starting point (initial appropriate value) of the first search when the search transition between the selection ranges is performed, The search after the search result Lqx shifts to another selection range is accelerated.

  By determining Lqxn as the initial appropriate value to be selected first when the permanent magnet synchronous motor 20 is started next time, the final search result for each selection range is determined as the appropriate value when the permanent magnet synchronous motor 20 is started next time. The time required for searching can be reduced.

Further, if the final search result Lqxn for each selected range is stored with the passage of time, it can also be used for detecting secular changes and abnormalities of the permanent magnet synchronous motor 20 based on the changes over time.
Other configurations, controls, and effects are the same as those in the first embodiment. Therefore, the description is omitted.

  In addition, each said embodiment and modification are shown as an example, and are not intending limiting the range of invention. The novel embodiments and modifications can be implemented in various other forms, and various omissions, rewrites, and changes can be made without departing from the spirit of the invention. In these embodiments and modifications, the scope of the invention is included in the gist, and is included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 10 ... Commercial AC power source, 11 ... Rectifier circuit, 12 ... Smoothing capacitor, 13 ... Switching circuit, 20 ... Permanent magnet synchronous motor, 22 ... Stator, 23 ... Rotor, 31, 32, 33 ... Current sensor, 40 ... MCU (motor Control unit), 41 ... current detection unit, 42 ... estimation calculation unit, 43 ... integration unit, 44 ... subtraction unit, 45 ... PI control unit, 46 ... subtraction unit, 47 ... calculation unit, 48 ... subtraction unit, 49 ... PI Control unit 50 ... PI control unit 51 ... PWM signal generation unit 52 ... Storage unit

Claims (4)

An inverter that converts alternating current voltage into direct current, converts the direct current voltage into alternating current by switching, and outputs it as a drive voltage to the motor;
Detecting means for detecting a field component current and a torque component current in the motor;
First control means for estimating a rotor speed of the motor based on at least a detection current of the detection means and an inductance of the motor, and controlling switching of the inverter so that the estimated rotor speed becomes a target speed;
Selecting an appropriate value of the inductance corresponding to the detection current of the detection means within a selection range consisting of a selection upper limit value and a selection lower limit value of the inductance value associated with the field component current or the torque component current; The selected appropriate value is used as the inductance value for estimation of the rotor speed by the first control means, and the appropriate value used for the estimation is set in the direction in which the deviation between the estimated rotor speed and the target speed is reduced. A second control means for sequentially searching and correcting within,
A motor drive device comprising: The selection range of the second control means is a data table in which the selection upper limit value and the selection lower limit value are associated with the field component current or the torque component current, or the correspondence is the field component current or the Function data expressed as a function of torque component current,
The motor driving apparatus according to claim 1. The selection upper limit value and the selection lower limit value of the inductance value are set stepwise for each predetermined width of the field component current or the torque component current, and form a rectangular selection range for each predetermined width. ,
When the search result exceeds the selection upper limit value, the second control means sets the selection upper limit value as the start point of the current search result and the next search, and when the search result falls below the selection lower limit value, the selection lower limit value. Is the search result of this time and the starting point of the next search,
The motor driving apparatus according to claim 1. The second control means stores a final search result in each of the selection ranges, and uses the stored final search result as a starting point of an initial search upon a search transition between the selection ranges. The initial appropriate value to be selected first at the next start of the motor
The motor driving device according to any one of claims 1 to 3, wherein the motor driving device is provided.

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