JP6170715B2 - Motor drive device - Google Patents

Description

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

  There is known a permanent magnet synchronous motor (also referred to as a brushless DC motor) including a stator having a plurality of phase windings and a rotor having a plurality of permanent magnets. The motor driving apparatus for driving the permanent magnet synchronous motor includes an inverter that outputs driving power to the motor. When the motor is started, an excitation current is passed through each phase winding through a predetermined path to set the rotor in advance. The so-called initial positioning is performed to rotate the position. After this initial positioning, forcible commutation is performed by applying a field component current (d-axis current) Id converted to the field axis (d-axis) coordinates on the rotor shaft to each phase winding to complete the start-up. . Then, after the start-up is completed, the current (phase current) flowing through each phase winding is detected, and the rotor speed (= angular speed) is estimated based on the detected current, and the inverter speed is set so that this estimated rotor speed becomes the target speed. So-called sensorless vector control for controlling switching is performed.

  As an initial position of the rotor, there is known an example in which one of a position of 240 degrees and a position of 70 degrees is selected based on an electrical angle.

Japanese Patent No. 3695889

  When initial positioning of the rotor is performed, the specific switching elements in the inverter are turned on and the remaining switching elements are turned off so that the excitation current flows through each phase winding in a predetermined path. Flows. For this reason, there exists a problem that the lifetime of a specific switching element becomes short compared with the lifetime of another switching element.

  The objective of embodiment of this invention is providing the motor drive device which can equalize the electric current which flows into each switching element of an inverter.

The motor driving device according to claim 1 includes a series circuit of a pair of switching elements for three phases , an inverter that outputs driving power to the motor by turning these switching elements on and off, Control means for causing a predetermined excitation current to flow through the three phase windings of the motor by PWM controlling the switching element to rotate the rotor of the motor to an initial position represented by a space vector angle reference . Then, the control means determines six positions different by 60 degrees on the basis of the space vector angle as the initial position, and makes a round while switching the six initial positions in a state of one round each time the motor is started. The switching is repeated periodically.

The block diagram of the control circuit of one Embodiment. The flowchart which shows the control of one Embodiment. The figure which shows the rotation of the initial position of the rotor in one Embodiment. The figure which shows the exciting current for initial positioning of one Embodiment matched with the electricity supply pattern by 3 phase modulation. The figure which shows the value of the exciting current in FIG. The figure which shows the relationship between the electric current of IGBT and loss in one Embodiment. The figure which matches the exciting current for initial positioning with the energization pattern by two-phase modulation as a modification of one Embodiment. The figure which shows the specific value of the exciting current in the modification of one Embodiment. The figure which shows the specific value of the exciting current in another modification of one Embodiment.

Hereinafter, an embodiment will be described with reference to the drawings.
As shown in FIG. 1, an AC voltage of a commercial AC power supply 1 is converted into a DC voltage by a rectifier circuit 4 including a diode bridge 2 and a smoothing capacitor 3. The DC voltage is converted into an AC voltage having a predetermined frequency by switching of the switching circuit 10, and the AC voltage is supplied to the permanent magnet synchronous motor 20 as driving power. The rectifier circuit 4 and the switching circuit 10 constitute an inverter.

  The permanent magnet synchronous motor 20 includes an input terminal 21 connected to an output terminal of an inverter, a stator (armature) 22 having a plurality of phase windings Lu, Lv, and Lw, and a plurality of, for example, two permanent magnets M1 and M2 having two poles. As an embedded rotor (rotor) 23. The permanent magnets M1 and M2 are arranged at positions facing each other with the rotor shaft 23a interposed therebetween.

  In the present embodiment, a two-pole rotor 23 having two permanent magnets M1 and M2 is taken as an example so that the position of the rotor 23 can be easily understood.

  The position of the rotor 23 in which the two-pole permanent magnets M1 and M2 are embedded can be expressed as a position of 0 degree to 359 degrees on an electrical angle basis. That is, when the correspondence between the permanent magnets M1, M2 and the phase windings Lu, Lv, Lw is in the state shown in FIG. 1, the rotor 23 is at an electrical angle of 0 degrees (= 360 degrees). The relationship between the electrical angle and the space vector is 270 degrees when the electrical angle is 0 degrees. Conversely, when the space vector is 0 degrees, the electrical angle is 90 degrees.

  Therefore, the position of the electrical angle of 90 degrees to 150 degrees is the first section (0 degree to 60 degrees) of the space vector, and the section of the space vector advances every 60 degrees thereafter, and the position of the electrical angle of 30 degrees to 90 degrees is the space. Corresponds to the sixth section (300-360 degrees) of the vector.

  The switching circuit 10 includes a series circuit of a pair of switching elements such as insulated gate bipolar transistors (abbreviated as IGBTs) 11u and 12u that are in a relationship between an upstream side and a downstream side along the direction in which a DC voltage is applied. A pair of switching elements having an upstream and downstream relationship along the DC voltage application direction, for example, a series circuit of IGBTs 11v and 12v, and a pair of switching elements having an upstream and downstream relationship along the DC voltage application direction For example, it has a series circuit of IGBTs 11w and 12w. The interconnection point of the IGBTs 11u, 12u is connected to one end of the phase winding Lu of the permanent magnet synchronous motor 20, the interconnection point of the IGBTs 11v, 12v is connected to one end of the phase winding Lv of the permanent magnet synchronous motor 20, and the IGBT 11w, The 12 w interconnection point is connected to one end of the phase winding Lw of the permanent magnet synchronous motor 20. The other ends of the phase windings Lu, Lv, Lw of the permanent magnet synchronous motor 20 are interconnected as a neutral point. Each IGBT has a parasitic diode.

  Current flowing through the phase windings Lu, Lv, and Lw of the permanent magnet synchronous motor 20 in the U-phase energization path, V-phase energization path, and W-phase energization path between the output terminal of the switching circuit 10 and the input terminal 21 of the permanent magnet synchronous motor 20 Current transformers 31, 32, and 33, which are current sensors for detecting (phase current), are arranged. The outputs of the current transformers 31, 32 and 33 are supplied to a control unit 40 which is a control means.

  The control unit 40 includes a main control unit 41, a storage unit 42, and a sensorless vector control unit 50. The storage unit 42 is a nonvolatile memory such as an EEPROM (electrically erasable programmable read-only memory). The control unit 40 and the inverter constitute a motor drive device.

  The sensorless vector control unit 50 includes a current detection unit 51, a speed estimation calculation unit 52, an integration unit 53, a subtraction unit 54, a speed control unit 55, a calculation unit 56, subtraction units 57 and 58, a current control unit (first current control). Unit) 61, a current control unit (second current control unit) 62, and a PWM signal generation unit 63.

  The current detector 51 converts the detected currents of the current transformers 31, 32, and 33 into three-phase to two-phase, and the field axis (d axis) coordinates and the torque axis (q axis) on the rotor axis in the permanent magnet synchronous motor 20. A field component current (also referred to as a d-axis current) Id and a torque component current (also referred to as a q-axis current) Iq converted to coordinates are detected.

  The speed estimation calculation unit 52 estimates the rotor speed ωest of the permanent magnet synchronous motor 20 by calculation based on the field component current Id and the torque component current Iq detected by the current detection unit 51. More specifically, the field component speed in the permanent magnet synchronous motor 20 is calculated by using the field component current Id, the torque component current Iq, the field component voltage Vd obtained by the current control units 61 and 62 described later, and the torque component voltage Vq. An electromotive force (referred to as d-axis speed electromotive force) Ed is estimated, and an estimated rotor speed ωest is obtained based on a proportional / integral control (PI control) calculation of the d-axis speed electromotive force Ed.

  The integration unit 53 obtains the estimated rotor position θest by integrating the estimated rotor speed ωest obtained by the speed estimation calculation unit 52. The estimated rotor position θest is supplied to the current detection unit 51 and the PWM signal generation unit 63. The subtracting unit 54 obtains a speed deviation between the target speed ωref and the estimated rotor speed ωest by subtracting the estimated rotor speed ωest from the input target speed ωref.

  The speed control unit 55 calculates a target value Iqref of the torque component current Iq by performing proportional / integral control (PI control) calculation on the speed deviation obtained by the subtracting unit 54. The calculation unit 56 obtains the target value Idref of the field component current Id from the target value Iqref of the torque component current Iq. The subtracting unit 57 obtains a deviation ΔId between the target value Idref and the field component current Id by subtracting the field component current Id from the target value Idref. The subtraction unit 58 obtains a deviation ΔIq between the target value Iqref and the torque component current Iq by subtracting the torque component current Iq from the target value Iqref.

  The current control unit 61 obtains a field component voltage Vd converted into a d-axis coordinate on the rotor axis in the permanent magnet synchronous motor 20 by a proportional / integral control (PI control) calculation of the deviation ΔId. The current control unit 62 obtains a torque component voltage Vq converted into q-axis coordinates on the rotor shaft in the permanent magnet synchronous motor 20 by proportional / integral control (PI control) calculation of the deviation ΔIq.

The PWM signal generator 63 generates a switching pulse width modulation signal (referred to as a PWM signal) for the switching circuit 10 in accordance with the field component voltage Vd, the torque component voltage Vq, and the estimated rotor position θest. By this PWM signal, each switching element of the switching circuit 10 is turned on / off, and driving voltages Vu, Vv, Vw for the respective phase windings of the permanent magnet synchronous motor 20 are output from the switching circuit 10 .

In the sensorless vector control unit 50, 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 angular velocity (electric rotational speed) of the motor shaft, Lq is the q-axis inductance of the stator 22, Ed is the d-axis velocity electromotive force (field component) Speed electromotive force), Ld is the d-axis inductance of the stator 22, and Eq is the q-axis speed electromotive force (torque component speed electromotive force; = ω · φ). As for the armature resistor R, when the output of the inverter is three-phase modulation, a value twice as large as the resistance of one phase winding is used, and the one-phase (lower phase) 100% energization method is used in two-phase modulation. In this case, a value 1.5 times the resistance of one phase winding is used because the lower side is parallel as the energization pattern for the winding.

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 with reference to the field axis (d-axis), so the field component speed electromotive force Ed is basically controlled to be zero. Is done.
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)
In the above equation, φ is an induced voltage coefficient (V · s / rad) which is one of motor constants. The speed estimation calculation unit 52 calculates the estimated rotor speed ωest so that the d-axis circuit equation holds. On the other hand, the d-axis speed electromotive force 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 the actual values. If they are different, the d-axis speed electromotive force Ed does not become zero. The d-axis speed electromotive force Ed can be obtained as an estimated value as follows.
Ed = Vd− (Id · R−ωest · Iq · Lq)
The speed deviation amount ωerr can be estimated by the proportional / integral control (PI control) calculation of the d-axis speed electromotive force Ed. The estimated rotor speed ωest can be obtained by subtracting the speed deviation amount ωerr from the target speed ωref.
ωerr = PI (Ed), ωest = ωref−ωerr
The main control unit 41 has the following means (1) to (4) as main functions.
(1) When the permanent magnet synchronous motor 20 is started, a specific PWM waveform is output for each phase by the PWM signal generation unit 63, and each IGBT of the switching circuit 10 is driven based on this PWM signal. An exciting current is passed through the phase windings Lu, Lv, and Lw of the motor 20 through a predetermined path, and the rotor 23 of the permanent magnet synchronous motor 20 is rotated to the initial position θ represented by the electrical angle reference (or space vector angle reference). 1st control means to make. In the following description, the angle is described on the basis of the space vector angle .

  (2) Second control means for switching the initial position angle θ by rotating the initial position angle θ sequentially by a constant angle Δθ degrees every time the permanent magnet synchronous motor 20 is started. The constant angle Δθ degree is, for example, 60 degrees. At this time, the PWM signal generation unit 63 is instructed to perform the PWM output so that the output of the determined angle is output, and based on this, each IGBT of the switching circuit 10 is turned on / off. To do. Here, the PWM signal generation unit 63 outputs an energization pattern by three-phase modulation.

  (3) After the initial positioning is performed by the first control means, the field component current (d-axis current) Id converted into the field axis (d-axis) coordinates on the rotor shaft 23a is converted into the phase windings Lu, Lv, Third control means for controlling the PWM signal generation unit 63 to turn on / off each IGBT of the switching circuit 10 in order to perform forced commutation to flow through Lw.

  (4) Fourth control means for starting sensorless vector control by the sensorless vector control unit 50 after the forced commutation (after completion of activation).

Next, the control executed by the main control unit 41 will be described with reference to the flowchart of FIG.
[First activation]
When the permanent magnet synchronous motor 20 is started (YES in step 101), the initial position θ (= 30 degrees, for example), the number of switching times N, and the constant angle Δθ (= 60 degrees) in the storage unit 42 are read (step 102). . A new initial position θn of the rotor 23 is obtained by the calculation of the following equation using the initial position θ, the number of times of switching N, and the constant angle Δθ (step 103).
θn = θ + Δθ × N
That is, if the number of times of switching N is the initial value “0”, θ1 (= 30 degrees + 60 degrees × 0 = 30 degrees) can be obtained as the new initial position θn. The PWM signal output by the PWM signal generation unit 63 is supplied to a predetermined IGBT in the switching circuit 10 so that an output corresponding to the initial position θ1 is performed, each IGBT is turned on / off, and the rotor 23 is configured as shown in FIG. Is rotated to an initial position θ1 shown in the upper left part of the screen (step 104).

  After the rotation to the initial position θ1, it is determined whether the switching frequency N has reached “5” (step 105). In this case, since the switching number N is still “0” (NO in step 105), the switching number N is increased by “1” to “1”, and is updated and stored in the storage unit 42 (step 106). Then, forced commutation is performed (step 109). Subsequently, sensorless vector control by the sensorless vector control unit 50 is started (step 110).

  When the first operation is completed and the motor is stopped and then restarted (second startup), the permanent magnet synchronous motor 20 is started for the second time (YES in step 101), and the initial position in the storage unit 42 is stored. θ (= 30 degrees), the number of switching times N (= “1”), and a constant angle Δθ (= 60 degrees) are read (step 102). A new initial position θn of the rotor 23 is obtained by the above calculation using the initial position θ, the number N of switching times, and the constant angle Δθ (step 103). In this case, since the number of times of switching N is “1”, θ2 (= 30 degrees + 60 degrees × 1 = 90 degrees) can be obtained as the new initial position θn.

  The predetermined IGBT in the switching circuit 10 is turned on / off based on the PWM output so that the exciting current flows in the phase windings Lu, Lv, Lw through a predetermined path corresponding to the initial position θ2, and the rotor 23 is turned on the right side of FIG. It is rotated to the initial position θ2 shown in the upper part (step 104). In this case, since the number of times of switching N is still “1” (NO in step 105), the number of times of switching N is increased by “1” to “2” and is updated in the storage unit 42 (step 106).

  Thereafter, step 101 to step 106 are repeated each time the motor is started, the initial position θn is determined, and the motor is controlled.

  And when it becomes the 7th start-up, it becomes the same as the 1st time. When the permanent magnet synchronous motor 20 is started (YES in Step 101), the initial position θ (= 30 degrees), the number of switching times N (= “0”), and the constant angle Δθ (= 60 degrees) in the storage unit 42 are read. (Step 102). In this case, since the number of times of switching N is “5” at the time of the previous sixth activation (YES in Step 105), the number of times of switching N is set to the initial value “0”, which is updated and stored in the storage unit 42. (Step 107). For this reason, since the switching number N is “0” which is the same as the first time, the new initial position θn is θ1 (= 30 degrees + 60 degrees × 0 = 30 degrees), which is the same initial position as that at the first activation. Thereafter, the same initial position is repeated every six activations.

[Excitation current]
As shown in FIG. 4, the excitation current for rotating the rotor 23 to the initial positions θ1 to θ6 is the same as the three-phase modulation energization pattern performed by the sensorless vector control after the start-up is completed.

  That is, when the rotor 23 is rotated to the initial position θ1 (= 30 degrees), the same PWM output waveform as during normal vector control operation at the time θ1 is used. Therefore, in the U-phase IGBTs 11u and 12u, the on-duty of the upper-phase IGBT 11u is large, in the V-phase IGBTs 11v and 12v, the on-duty of the upper-phase IGBT 11v is small, and in the W-phase IGBTs 11w and 12w, The on-duty of the IGBT 11w becomes the smallest, and conversely, the on-duty of the lower-phase IGBT 12w becomes large. As shown in FIG. 5, the magnitudes of the currents of the respective phase windings at this time are the excitation current Iu1 = 0.8660 of the phase winding Lu, which is the relative value of each sine wave, and the excitation current Iv1 = 0 of the phase winding Lv. The excitation current Iw1 of the phase winding Lw is −0.8660. The exciting current Iu1 is a current that flows from the positive output terminal of the rectifier circuit 4 to the phase winding Lu through the IGBT 11u of the switching circuit 10. The excitation current Iw1 is a current that flows into the phase winding Lw through the phase winding Lu, and returns from the phase winding Lw to the negative output terminal of the rectifier circuit 4 through the IGBT 12w of the switching circuit 10.

  Similarly, when the rotor 23 is rotated to the initial position θ6 (= 330 degrees), each IGBT is similarly turned on / off according to the PWM signal, and the excitation current shown in FIG. 5 is supplied to each phase winding Lu to Lw. The excitation current Iu6 at the initial position θ6 is a current that flows from the positive output terminal of the rectifier circuit 4 to the phase winding Lu through the IGBT 11u of the switching circuit 10. The current that flows into the phase winding Lv through the phase winding Lu, returns from the phase winding Lv to the negative output end of the rectifier circuit 4 through the IGBT 12v of the switching circuit 10 is an excitation current Iv6.

  At each of the above six initial positions, the sum of the absolute values of the relative values of the excitation currents Iu1 and Iu6 flowing through the IGBT 11u and the excitation currents Iu3 and Iu4 flowing through the IGBT 12u as shown in the bottom row of the table of FIG. 5 is 3.4641. . The sum of the absolute values of the relative values of the excitation currents Iv2 and Iv3 flowing through the IGBT 11v and the excitation currents Iv5 and Iv6 flowing through the IGBT 12v is also 3.4641. Similarly, the sum of the absolute values of the excitation currents Iw4 and Iw5 flowing through the IGBT 11w and the relative values of the excitation currents Iv1 and Iv2 flowing through the IGBT 12w is 3.4641, which are all the same.

  Thus, by rotating and switching the initial position of the rotor 23 to the initial positions θ1 to θ6 in order every time the permanent magnet synchronous motor 20 is started, the current flowing through each IGBT of the switching circuit 10 can be made uniform. Thereby, the lifetime of each IGBT can be equalized, and stable and highly reliable motor driving can be achieved.

  In addition, by selecting 30 degrees, 90 degrees, 150 degrees, 210 degrees, 270 degrees, and 330 degrees as the initial positions θ1, θ2, θ3, θ4, θ5, and θ6 on the basis of the space vector angle, The excitation current can be minimized. That is, as shown in the uppermost stage of FIG. 4, the change in the sum of the absolute values of the excitation current at each angle becomes the minimum value at 30 degrees, 90 degrees, 150 degrees, 210 degrees, 270 degrees, and 330 degrees. The current value can be lowered as compared with the case where other angles are used.

As shown in FIG. 6, the IGBT used as the switching element has a characteristic that the conduction loss is proportional to the energization current (excitation current). Therefore, by suppressing the excitation current value at each initial position to the minimum, the IGBT The effect that the conduction loss can be reduced is obtained .
[Modification]
In the above embodiment, the initial positions θ1, θ2, θ3, θ4, θ5, and θ6 are 30 degrees, 90 degrees, 150 degrees, 210 degrees, 270 degrees, and 330 degrees on the basis of the space vector angle. May be.

  In the above embodiment, the excitation current for rotating the rotor 23 to the initial positions θ1 to θ6 is output by the PWM signal generation unit 63 by the PWM energization pattern using the three-phase modulation, but as shown in FIG. The PWM signal generation unit 63 may output a two-phase modulation PWM energization pattern.

Further, as the initial positions θ1 to θ6, if the IGBT loss is not considered so much, as shown in FIG. 8, the space vector angle reference is 60 degrees, 120 degrees, 180 degrees, 240 degrees, 300 degrees, 0 degrees, and so on. As shown in FIG. 9, it may be set to 40 degrees, 100 degrees, 160 degrees, 220 degrees, 280 degrees, and 340 degrees on the basis of the space vector angle . Incidentally, as shown in FIG. 9, the space vector angle reference 40 degrees, 100 degrees, 160 degrees, 220 degrees, 280 degrees, and 340 degrees are 130 degrees, 180 degrees, 250 degrees, 310 degrees, and 10 degrees on the electrical angle basis. This corresponds to 70 degrees.

  In the above embodiment, the permanent magnet synchronous motor having two permanent magnets M1 and M2 as two poles has been described as an example, but the present invention can be similarly applied to a permanent magnet synchronous motor having four permanent magnets as four poles.

  In addition, the 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 1 ... Commercial AC power supply, 2 ... Diode bridge, 3 ... Smoothing capacitor, 4 ... Rectifier circuit, 10 ... Switching circuit, 11u, 12u, 11v, 12v, 11w, 12w ... IGBT (switching element), 20 ... Permanent magnet synchronous motor , 21 ... input terminal, 22 ... stator, Lu, Lv, Lw ... phase winding, 23 ... rotor, 23a ... rotor shaft, M1, M2 ... permanent magnet, 31, 32, 33 ... current sensor, 40 ... control unit, DESCRIPTION OF SYMBOLS 41 ... Main control part, 42 ... Memory | storage part, 50 ... Sensorless vector control part, 51 ... Current detection part, 52 ... Speed estimation calculation part, 53 ... Integration part, 54 ... Subtraction part, 55 ... Speed control part, 56 ... Calculation unit 57, 58... Subtraction unit 61 Current control unit 62 Current control unit 63 PWM signal generation unit

Claims (3)

An inverter which has a series circuit of a pair of switching elements for three phases , and outputs driving power to the motor by turning these switching elements on and off;
When the motor is started, the switching elements are PWM controlled so that a predetermined excitation current is passed through the three phase windings of the motor to rotate the rotor of the motor to an initial position represented by a space vector angle reference. Control means for causing
With
The control means determines six positions differing by 60 degrees on the basis of a space vector angle as the initial position, and switches the six initial positions in a state of one round each time the motor is started. Is repeated periodically,
The motor drive device characterized by the above-mentioned. The control means determines positions of 30 degrees, 90 degrees, 150 degrees, 210 degrees, 270 degrees, and 330 degrees that are different by 60 degrees on the basis of a space vector angle as the initial position.
The motor driving apparatus according to claim 1. Each of the switching elements is an insulated gate bipolar transistor.
When the motor is started, the control means turns on and off each switching element with a pulse width modulation signal generated by three-phase modulation to cause a predetermined excitation current to flow through the three phase windings of the motor. Rotate the rotor of the motor to the initial position represented by the space vector angle reference;
The motor driving apparatus according to claim 1 or 2, wherein the motor driving apparatus is provided.

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