JP5648310B2 - Synchronous motor control device and synchronous motor control method - Google Patents

Description

  The present invention relates to a synchronous motor control device and a synchronous motor control method.

  As a driving technique for efficiently operating the brushless synchronous motor, there is a technique for controlling the phase difference between the motor voltage and the motor current to a predetermined angle in accordance with the load and the rotational speed.

  In Patent Document 1, in a synchronous motor control device, a vector phase of a voltage and a vector phase of a current applied to the synchronous motor are obtained, and a power factor that is a phase difference between the voltage vector phase and the current vector phase is calculated. The calculation in real time is described. Specifically, the control device receives the R-phase, S-phase, and T-phase signals (three-phase signal) from the three-phase signal source, and determines the three-phase signal based on the magnitude relationship of the R-phase, S-phase, and T-phase signals. Is in the section “0” to “5”. Then, the control device calculates the converted phase value of the three-phase signal from the determination result, and obtains the vector phase of the voltage and the vector phase of the current from the calculated converted phase value. Thereby, according to patent document 1, it is supposed that the synchronous operation control of a synchronous motor with a simple structure and high precision can be implement | achieved.

  In Patent Literature 2, in a brushless DC motor driving device, a one-phase or three-phase current applied to the brushless DC motor is detected, the phase of the detected current is calculated, and the calculated phase is commanded. It is described that control is performed such that the difference from the current phase (current phase difference) becomes zero. Thereby, according to patent document 2, it is supposed that the phase difference of the electric current with respect to a voltage can be controlled arbitrarily.

JP 2008-199706 A JP-A-5-236789

  In the control device of Patent Document 1, the calculation of the phase difference between the vector phase of the voltage applied to the synchronous motor and the vector phase of the current is performed on a three-phase (R phase, S phase, T phase) fixed coordinate system. The phase difference calculation process becomes complicated. This complicates the configuration of the control device, which increases the manufacturing cost of the control device.

  Patent Document 2 does not describe how to calculate the phase difference between the current and voltage applied to the brushless DC motor.

  The present invention has been made in view of the above, and it is a synchronous motor that can obtain a phase difference between a current vector and a voltage vector applied to the synchronous motor with a simple configuration and can control the phase difference to match a target phase difference. It is an object to provide a control device and a control method of a synchronous motor.

  In order to solve the above-described problems and achieve the object, a synchronous motor control device according to the present invention receives a command rotational speed from the outside, and controls the sensorless synchronous motor to operate at the command rotational speed. A motor control device that converts a current vector in a fixed coordinate system to a current vector in a rotating coordinate system when driving the synchronous motor by the driving unit that drives the synchronous motor, and at least the conversion A phase difference between the current vector and the voltage vector applied to the synchronous motor using the current vector in the rotated coordinate system, and the phase difference obtained by the computation unit matches a target phase difference. Adjust the phase angle of the voltage vector on the rotating coordinate system to adjust the phase angle of the voltage vector on the rotating coordinate system. An estimation unit for estimating a rotation speed of the voltage vector in the fixed coordinate system in the state; and the phase difference and the target phase difference when the voltage vector is rotated at the rotation speed estimated by the estimation unit in the fixed coordinate system. A control unit that controls the magnitude of the voltage vector in the rotating coordinate system so that a deviation from the synchronous motor does not occur, and the driving unit is configured to use the synchronous motor with a voltage corresponding to the voltage vector controlled by the control unit. The synchronous motor is driven so as to operate.

  Further, in the synchronous motor control device according to the present invention, in the above invention, the rotational coordinate system includes a δ axis and a γ axis orthogonal to each other, and the calculation unit calculates a current vector in the fixed coordinate system, The voltage vector controlled by the control unit is converted into a current vector in a rotating coordinate system defined so as to coincide with the δ axis.

Also, in the synchronous motor control device according to the present invention, in the above invention, the calculation unit sets the δ-axis component of the current vector in the rotating coordinate system to i _δ and the γ-axis component to i _γ . Then, the phase difference Δθ between the current vector and the voltage vector applied to the synchronous motor is obtained by the equation tan (Δθ) = i _γ / i _δ .

  The synchronous motor control method according to the present invention is a synchronous motor control method for receiving a command rotational speed from the outside and controlling the sensorless synchronous motor so as to operate at the command rotational speed. Converting a current vector in a fixed coordinate system when driving the synchronous motor into a current vector in a rotating coordinate system, and using at least the converted current vector in the rotating coordinate system, a current vector applied to the synchronous motor And the phase angle of the voltage vector on the rotating coordinate system so that the calculated phase difference matches the target phase difference, and the voltage vector on the rotating coordinate system is adjusted. The rotational speed of the voltage vector in the fixed coordinate system with the phase angle adjusted is estimated, and the estimated speed in the fixed coordinate system is estimated. The magnitude of the voltage vector in the rotating coordinate system is controlled so that a deviation between the phase difference and the target phase difference does not occur when the voltage vector is rotated at a different rotation speed. The synchronous motor is driven so that the synchronous motor operates at a corresponding voltage.

  The synchronous motor control apparatus and synchronous motor control method according to the present invention can obtain a phase difference between a current vector and a voltage vector applied to the synchronous motor with a simple configuration and can control the phase difference to match a target phase difference. There is an effect.

FIG. 1 is a diagram illustrating a configuration of a synchronous motor control device according to an embodiment. FIG. 2 is a diagram illustrating a voltage vector and a current vector in the γ-δ coordinate system. FIG. 3 is a diagram illustrating a configuration of the phase difference detector in the embodiment. FIG. 4 is a diagram illustrating the relationship between the γ-δ coordinate system and the dq coordinate system. FIG. 5 is a diagram illustrating a configuration of the speed estimator in the embodiment. FIG. 6 is a diagram illustrating a configuration of the voltage controller in the embodiment. FIG. 7 is a flowchart illustrating the synchronous motor control method according to the embodiment. FIG. 8 is a diagram illustrating a configuration of a synchronous motor control device according to a modification of the embodiment.

  Hereinafter, embodiments of a control apparatus for a synchronous motor according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment.

  A synchronous motor control device 1 according to an embodiment will be described with reference to FIG. The control device 1 receives a command rotational speed from the outside. The control device 1 controls a sensorless synchronous motor (hereinafter referred to as a synchronous motor) M so as to operate at a command rotational speed. The synchronous motor M includes, for example, a brushless permanent magnet motor and a load. FIG. 1 is a block diagram illustrating a configuration of a control device 1 that controls a phase difference in a rotating coordinate system.

  The control device 1 includes a drive unit 10, a detection unit 50, a calculation unit 20, an estimation unit 30, a control unit 40, and an integrator 60.

  The drive unit 10 drives the synchronous motor M by supplying three-phase AC signals U, V, and W to the synchronous motor M. The internal configuration of the drive unit 10 will be described later.

The detection unit 50 detects (picks up) the amplitude of at least two-phase currents. Specifically, the detection unit 50 includes a current sensor 51 and a current sensor 52. The current sensor 51 detects the amplitude of the U-phase current i _U and supplies it to the computing unit 20. The current sensor 52 detects the amplitude of the W-phase current i _W and supplies it to the computing unit 20. Each of the current sensor 51 and the current sensor 52 may AD-convert the current value and supply it to the arithmetic unit 20 as a signal that can be controlled by a digital computer.

The arithmetic unit 20 converts the current vector (i _U , i _W ) in the fixed coordinate system (UVW coordinate system) when the driving unit 10 drives the synchronous motor M into the current vector (γ-δ coordinate system) in the rotational coordinate system (γ-δ coordinate system). i _γ , i _δ ). The rotating coordinate system (γ-δ coordinate system) has a δ axis and a γ axis that intersect each other. Then, the calculation unit 20 obtains a phase difference between the current vector I and the voltage vector V applied to the synchronous motor M by using at least the converted current vector (i _γ , i _δ ) in the rotating coordinate system.

  Specifically, the calculation unit 20 includes a three-phase to two-phase converter (UVW / γ-δ) 21 and a phase difference detector 22.

The three-phase to two-phase converter 21 receives the detected value of the amplitude of the U-phase current i _U from the current sensor 51 and receives the detected value of the amplitude of the W-phase current i _W from the current sensor 52. Further, the three-phase to two-phase converter 21 receives the phase angle θ (voltage vector phase angle −π / 2) of the rotating coordinate system from the integrator 60. For example, the three-phase to two-phase converter 21 converts the current vector (i _U , i _W ) in the fixed coordinate system (UVW coordinate system) into the rotational coordinate system (γ− It is converted into a current vector (i _γ , i _δ ) in the δ coordinate system.

i _γ = (√2) {i _U × cos (θ + 30 °) −i _W × sin (θ)} (1)
i _δ = − (√2) {i _U × sin (θ + 30 °) + i _W × cos (θ)} (2)
The three-phase to two-phase converter 21 uses a current vector (i _U , i _W ) in a fixed coordinate system (UVW coordinate system) and a direction of a voltage vector (v _γ , v _δ ) controlled by the control unit 40 is δ. You may convert into the current vector in the rotation coordinate system (gamma-delta coordinate system) defined so that it might correspond to an axis | shaft (namely, it becomes v ( _gamma ) = 0). The three-phase to two-phase converter 21 outputs the converted current vector (i _γ , i _δ ) in the rotating coordinate system (γ-δ coordinate system) to the phase difference detector 22.

The phase difference detector 22 obtains the phase difference Δθ between the current vector I applied to the synchronous motor M and the voltage vector V using the current vector (i _γ , i _δ ) in the rotating coordinate system. The phase difference detector 22 is, for example, a rotational coordinate defined by the three-phase to two-phase converter 21 so that the current vector (i _U , i _W ) in the fixed coordinate system (UVW coordinate system) becomes v _γ = 0. When converted into a current vector (i _γ , i _δ ) in the system (γ-δ coordinate system), the phase difference between the current vector I and the voltage vector V applied to the synchronous motor M is obtained by the following equation (11). Find Δθ. The phase difference detector 22 supplies the obtained phase difference Δθ to the estimation unit 30.

Note that the detection unit 50 may detect (pick up) the amplitude of the current of three phases (U phase, V phase, W phase) and supply it to the calculation unit 20. In this case, the detection unit 50 detects the amplitude of the current i _V of the V-phase further comprises a current sensor supplies (not shown) to the arithmetic unit 20. 3-phase to two-phase converter 21, for example, the current vector in the formula (1) and amplitude of the current i _V in (2) be used by adding each considering factors wherein the fixed coordinate system (UVW coordinate system) (I _U , i _V , i _W ) is converted into a current vector (i _γ , i _δ ) in the rotating coordinate system (γ-δ coordinate system).

The estimation unit 30 adjusts the phase angle of the voltage vector (v _γ , v _δ ) on the rotating coordinate system (γ-δ coordinate system) so that the phase difference obtained by the calculation unit 20 matches the target phase difference. . At the same time, the estimation unit 30 rotates the voltage vector in the fixed coordinate system (UVW coordinate system) in a state where the phase angle of the voltage vector (v _γ , v _δ ) is adjusted on the rotational coordinate system (γ-δ coordinate system). Estimate speed.

  Specifically, the estimation unit 30 includes a target phase difference table 31, a comparator 32, and a speed estimator 33.

The target phase difference table 31 is data that provides a target phase difference between voltage and current using a current value (for example, i _U or i _γ , i _δ ) or a rotation speed (for example, a command rotation speed ω ^* ) as a read condition. It is a table. The target phase difference varies depending on the product and the synchronous motor M to be used, such as the environment in which the synchronous motor M is applied, operating characteristics, and startup. For this reason, the target phase difference table 31 preliminarily determines and stores a phase difference that is an optimum value.

The comparator 32 receives the phase difference Δθ between the current vector I and the voltage vector V applied to the synchronous motor M from the phase difference detector 22. The comparator 32 refers to the target phase difference table 31 and acquires the target phase difference Δθ ^* . The comparator 32 sets an error Δθ _d as a result of comparison between the phase difference Δθ between the current vector I and the voltage vector V applied to the synchronous motor M and the target phase difference Δθ ^* . The comparator 32 obtains the error Δθ _d by, for example, the following formula (12) (or formula (13)). The comparator 32 outputs the obtained error Δθ _d to the speed estimator 33.

Speed estimator 33 receives error Δθ _d from comparator 32. The speed estimator 33 adjusts the phase angle of the voltage vector (v _γ , v _δ ) on the rotating coordinate system (γ-δ coordinate system) so that the error Δθ _d becomes zero. At the same time, the speed estimator 33 calculates the voltage vector in the fixed coordinate system (UVW coordinate system) when the phase angle of the voltage vector (v _γ , v _δ ) is adjusted on the rotating coordinate system (γ-δ coordinate system). The rotational speed ωe is estimated as an instantaneous value. The speed estimator 33 outputs the estimated rotational speed ωe to the control unit 40 and the integrator 60, respectively.

The control unit 40 prevents the phase difference Δθ and the target phase difference Δθ ^* from shifting when the voltage vector is rotated at the rotation speed ωe estimated by the estimation unit 30 in the fixed coordinate system (UVW coordinate system). The magnitude of the voltage vector (v _γ , v _δ ) in the rotating coordinate system (γ-δ coordinate system) is controlled.

  Specifically, the control unit 40 includes a converter 41, a command input unit 42, a comparator 43, and a voltage controller 44.

The converter 41 receives the rotation speed ωe of the voltage vector in the fixed coordinate system (UVW coordinate system) from the speed estimator 33. Converter 41 converts the rotational speed ωe of the voltage vector in the fixed coordinate system (UVW coordinate system) to the mechanical rotation speed omega _m of the rotor in a synchronous motor M. That is, the converter 41 divides the rotational speed ωe of the voltage vector in the fixed coordinate system (UVW coordinate system) by the pole pair number P / 2 (P is the number of magnetic poles of the motor) (multiply the reciprocal number 2 / P of the pole pair number). Thus, the mechanical rotational speed ω _m of the rotor in the synchronous motor M is obtained. The converter 41 outputs the obtained mechanical rotation speed ω _m to the comparator 43.

Command rotation speed ω ^* is input to command input unit 42 from the outside (for example, a host device). The command rotational speed ω ^* is a value for designating the synchronous rotational speed of the synchronous motor M. The command input unit 42 outputs the input command rotational speed ω ^* to the comparator 43.

The comparator 43 receives a mechanical rotational speed ω _m corresponding to the rotational speed ωe estimated by the speed estimator 33 from the converter 41 and receives a command rotational speed ω ^* from the command input unit 42. The comparator 43 compares the mechanical rotational speed ω _m corresponding to the estimated rotational speed ωe with the command rotational speed ω ^* as a speed difference Δω.

The voltage controller 44 receives the speed difference Δω from the comparator 43. The voltage controller 44 controls the magnitude of the voltage vector (v _γ , v _δ ) in the rotating coordinate system (γ-δ coordinate system) so that the speed difference Δω becomes zero. The voltage controller 44 sets v _γ to 0 (to redefine the rotating coordinate system so that the direction of the voltage vector (v _γ , v _δ ) coincides with the δ axis) and responds to the speed difference Δω. The value of v _δ is adjusted so as to cancel the surplus reluctance torque generated in the synchronous motor M. Accordingly, the voltage controller 44 generates a voltage vector (v _γ , v _δ ) and supplies it to the drive unit 10.

  The integrator 60 receives the rotation speed ωe of the voltage vector in the fixed coordinate system (UVW coordinate system) from the speed estimator 33. The integrator 60 integrates the rotational speed ωe of the voltage vector, thereby calculating the phase angle θ (the phase angle of the voltage vector −π / 2) of the rotating coordinate system that rotates with the voltage vector. The integrator 60 outputs the calculated phase angle θ to the drive unit 10 and the calculation unit 20, respectively.

The drive unit 10 drives the synchronous motor M so that the synchronous motor M operates at a voltage corresponding to the voltage vector (v _γ , v _δ ) controlled by the control unit 40. Specifically, the drive unit 10 includes a two-phase to three-phase converter (γ-δ / UVW) 11 and a driver 12.

The two-phase to three-phase converter 11 receives a voltage vector (v _γ , v _δ ) in the rotating coordinate system (γ-δ coordinate system) from the voltage controller 44. The two-phase to three-phase converter 11 receives the phase angle θ from the integrator 60. For example, the two-phase to three-phase converter 11 converts the voltage vector (v _γ , v _δ ) in the rotating coordinate system (γ-δ coordinate system) into a fixed coordinate system (equation (3) to equation (5)). Conversion into voltage vectors (v _U , v _v , v _W ) in the UVW coordinate system.

_{v U = (√ (2/3)} ) {v γ × cos (θ) -v δ × sin (θ)} ··· (3)
v _v = (√ (1/2) × v _γ + √ (1/6) × v _δ ) × sin (θ) + (√ (1/2) × v _δ− √ (1/6) × v _γ ) × cos (θ) (4)
_{v W = (√ (1/6)} × v δ -√ (1/2) × v γ) × sin (θ) - (√ (1/6) × v γ + √ (1/2) × v δ ) × cos (θ) (5)
The two-phase to three-phase converter 11 outputs the voltage vector (v _U , v _v , v _W ) in the fixed coordinate system (UVW coordinate system) in the converted rotating coordinate system (γ-δ coordinate system) to the driver 12. . Although the above equations (3) to (5) are equations for three-phase demodulation, the two-phase to three-phase converter 11 may perform two-phase modulation to increase the voltage utilization rate.

The driver 12 receives a voltage vector (v _U , v _v , v _W ) in the fixed coordinate system (UVW coordinate system) from the two-phase / three-phase converter 11. The driver 12 performs a power conversion operation such as generating a pulse train (U, V, W) by modulating a voltage vector (v _U , v _v , v _W ) that is a UVW voltage signal by PWM (Pulse Width Modulation). That is, the driver 12 drives the synchronous motor M by supplying the generated three-phase AC signals U, V, and W to the synchronous motor M.

The voltage vector so that the error [Delta] [theta] _d becomes 0 (v _γ, v _δ) and the coefficient in the velocity estimator 33 for adjusting the phase angle of the voltage vector so that the speed difference Δω becomes 0 (v _gamma , V _δ ), the coefficient in the voltage controller 44 for controlling the magnitude is determined in advance so as to have mutually appropriate values. That is, the coefficient in the speed estimator 33 and the coefficient in the voltage controller 44 indicate that the adjustment of the phase angle by the speed estimator 33 and the control of the magnitude of the voltage vector by the voltage controller 44 converge in relation to each other. As described above, it is assumed that it is determined in advance.

  Next, processing in the phase difference detector 22 will be described in detail with reference to FIG.

FIG. 2 shows a voltage vector V = (v _γ , v _δ ) and a current vector I = (i _γ , i _δ ) on the rotating coordinate system (γ-δ coordinate system). In FIG. 2, each component of the voltage vector V can be substituted with the voltages v _γ and v _δ output from the voltage controller 44 ignoring the loss caused by the driver 12. Each component of the current vector I is i _γ and i _δ output from the three-phase to two-phase converter 21.

If the angle formed by the voltage vector V with the δ axis of the rotating coordinate system is θ _v , and the angle formed by the current vector I with the δ axis of the rotating coordinate system is θ _i , the voltage vector V and current obtained by the phase difference detector 22 are obtained. The phase difference Δθ with the vector I is
Δθ = θ _i −θ _v (6)
It is expressed.

At this time, if the tan values of θ _v and θ _i are expressed using v _γ , v _δ , i _γ and i _δ , respectively, tan (θ _v ) = v _γ / v _δ (7)
tan (θ _i ) = i _γ / i _δ (8)
It becomes.

Further, sin (Δθ) and cos (Δθ) are expanded by substituting Equation (6).
sin (Δθ) = sin (θ _i −θ _v ) = sin (θ _i ) × cos (θ _v ) −cos (θ _i ) sin (θ _v )
cos (Δθ) = cos (θ _i −θ _v ) = cos (θ _i ) × cos (θ _v ) + sin (θ _i ) sin (θ _v )
It is.

When the ratio of these two formulas is taken and arranged as tan (Δθ), the following formula (9) is obtained.
sin (Δθ) / cos (Δθ) = tan (Δθ) = {tan (θ _i ) −tan (θ _v )} / {1 + tan (θ _i ) × tan (θ _v )} (9)

Substituting Equation (7) and Equation (8) into Equation (9),
tan (Δθ) = (v _δ × i _γ −v _γ × i _δ ) / (v _δ × i _δ + v _γ × i _γ ) (10)
It becomes.

Here, since the voltage controller 44 sets v _γ = 0 in order to redefine the rotating coordinate system in which the direction of the voltage vector (v _γ , v _δ ) coincides with the δ axis, the equation (10) is tan (Δθ) = i _γ / i _δ (11)
To be simplified.

  Eventually, the phase difference detector 22 calculates and outputs the phase difference Δθ by calculating arctan of the value obtained by the equation (11). At this time, when Δθ is in the vicinity of ± π / 2, the value of tan (Δθ) approaches ± ∞ and tends to diverge. Therefore, a limiter is provided in the calculation result of Equation (11) to prevent divergence.

That is, as shown in FIG. 3, the phase difference detector 22 includes a phase difference calculation unit 22a and a limiter unit 22b. The phase difference calculation unit 22 a receives the current vector (i _γ , i _δ ) in the rotating coordinate system from the three-phase to two-phase converter 21. The phase difference calculation unit 22a obtains the current vector I and the voltage vector applied to the synchronous motor M by the equation (11), that is, by taking the ratio (i _γ / i _δ ) of the two components of the current vector in the rotating coordinate system. A phase difference Δθ with respect to V is obtained and supplied to the limiter unit 22b. If the supplied value is within a predetermined range, the limiter unit 22b outputs the phase difference Δθ as it is. Thereby, the comparator 32 calculates | requires error (DELTA) (theta) _d using following Formula (12).
Δθ _d = Δθ ^* −Δθ (12)

In consideration of the fact that the speed estimator 33 at the next stage may be calculated so that the error Δθ _d between the phase difference Δθ and the target phase difference Δθ * is zero, the phase difference detector 22 is expressed by the equation (11). The value of tan (Δθ) obtained in step) may be output as it is. In this case, the value stored in the target phase difference table may be stored as tan (Δθ *). Thereby, the comparator 32 calculates | requires error (DELTA) (theta) _d using following Formula (13).
Δθ _d ≡tan (Δθ ^* ) − tan (Δθ) (13)

  Next, the adjustment of the phase angle by the speed estimator 33 and the control of the magnitude of the voltage vector by the voltage controller 44 will be described in detail.

The synchronous motor M is, for example, an IPM (Interior Permanent Mgnet) motor. In this case, in the synchronous motor M, the phase difference Δθ between the applied voltage vector and the current vector becomes the target phase difference Δθ ^* so as to maximize the total torque (power factor) obtained by combining the magnet torque and the reluctance torque. It is necessary to control so that they match (that is, the error Δθ _d becomes zero). In order to control the phase difference, in addition to adjusting the phase angle of the voltage vector applied to the synchronous motor M, it is necessary to control the magnitude of the voltage vector applied to the synchronous motor M.

If the error Δθ _d is positive, the voltage vector (δ axis) is delayed, so it is sufficient to increase the rotation speed. If the error Δθ _d is negative, the voltage vector (δ axis) is advanced. So you can reduce the rotation speed. If Δθ _d is 0, the voltage vector (δ axis) should rotate at the synchronous speed with the phase angle as indicated.

However, even if only the advance angle and delay angle of the voltage vector are corrected, the phase difference Δθ between the voltage vector applied to the synchronous motor M and the current vector cannot be maintained so as to match the target phase difference Δθ ^*. . At the same time, it is necessary to control the magnitude of the voltage vector. This will be described in detail with reference to FIG.

  As shown in FIG. 4, for example, consider a case where the axes of the dq rotation coordinate system and the axes of the γ-δ rotation coordinate system are shifted. In the dq rotation coordinate system, the d-axis indicates the main magnetic flux direction of the rotor in the synchronous motor M, and the q-axis indicates an axis orthogonal to the d-axis.

The phase difference detector 22 detects that the voltage vector V and the current vector I are rotating with a phase difference of Δθ on the γ-δ rotating coordinate system, and the phase difference Δθ is smaller than the target phase difference Δθ ^*. If the comparator 32 finds out, the speed estimator 33 causes the phase angle of the voltage vector (v _γ , v _δ ) on the rotating coordinate system (γ-δ coordinate system) so that the error Δθ _d becomes zero. Advance. As a result, the rotation speed of the voltage vector is increased, and the voltage vector is advanced with respect to the δ axis by the next energization. Here, a γ′−δ ′ rotating coordinate system is introduced as a new coordinate system. It is assumed that the δ ′ axis of this rotating coordinate system coincides with the direction of the voltage vector. A voltage vector in the γ′-δ ′ rotating coordinate system defined in this way is output from the voltage controller 44.

At this time, the induced voltage vector Ec of the rotor in the synchronous motor M generated in the q-axis direction has components of δ-axis and δ′-axis, e _δ and e _δ ′ (e _δ > e _δ ′), respectively. become. Before the voltage vector is advanced (δ axis), in the synchronous motor M,
v _δ -e _δ
The rotor is rotated with a torque of.

On the other hand, in the state where the voltage vector is advanced (δ ′ axis), in the synchronous motor M,
v _δ −e _δ ′ (> v _δ −e _δ )
The rotor is rotated with the increased torque.

Since the steady state is considered now, assuming that the load torque is constant, the increase of the torque due to the advance angle accelerates the rotor. The acceleration of the rotor means that the q-axis is advanced so as to catch up with the δ′-axis that has been accelerated and advanced. That is, if the q axis is accelerated and advanced, the current vector is also accelerated and advanced, so that the increased phase difference Δθ ^* returns to the original phase difference Δθ. Therefore, in order to reduce the torque (cancel the surplus torque), it is necessary to reduce the voltage vector magnitude (v _δ ) by an appropriate method.

On the other hand, when the voltage vector is retarded while the load torque is constant, the above is reversed. That is, the torque reduction due to the retard angle decelerates the rotor. The fact that the rotor is decelerated means that the q-axis is decelerated so as to catch up with the delayed δ′-axis (to coincide with the direction of the voltage vector). That is, when the q axis is decelerated and retarded, the current vector is also decelerated and retarded, so that the reduced phase difference Δθ ^* returns to the original phase difference Δθ. Therefore, in order to increase the torque (make up for the shortage of torque), it is necessary to increase the magnitude of the voltage vector by an appropriate method.

  Further, when the load increases, the direction of the difference between the axis of the dq rotation coordinate system and the axis of the γ-δ rotation coordinate system widens, so the phase difference Δθ between the voltage vector V and the current vector I is controlled. Therefore, the voltage vector (δ axis) is retarded. The magnitude of the voltage vector is increased. Conversely, when the load decreases, the voltage vector is advanced to reduce the magnitude of the voltage vector.

Adjustment to advance or retard the voltage vector is performed by a speed estimator 33 (see FIG. 1). The speed estimator 33 includes a PI controller 33a as shown in FIG. The PI controller 33a performs the P control and the I control so that the error Δθ _d becomes zero, so that the phase angle of the voltage vector (v _γ , v _δ ) on the rotating coordinate system (γ-δ coordinate system). Adjust.

Also, the PI controller 33a uses, for example, the error Δθ _d received from the comparator 32,
ωe = K _p × Δθ _d + K _I ∫Δθ _d dt (14)
From this equation, the rotational speed ωe of the voltage vector in the fixed coordinate system (UVW coordinate system) can be estimated as an instantaneous rotational speed. In Expression (14), K _p and K _I are coefficients that are determined in advance so that the operation of the control device 1 is stabilized.

This is because, as shown in FIG. 5 (b), when the output of the PI controller 33a is integrated by the integrator 60, a conversion angle θ to the rotating coordinate system is obtained, which is a three-phase to two-phase converter 21, a phase difference detector. 22, and comparator 32 is fed back to the PI controller 33a as an error [Delta] [theta] _d via is sequentially controlled. Thereby, when the error Δθ _d converges to 0, the rotational speed ωe in a state where the detected phase difference Δθ matches the target phase difference Δθ ^* can be obtained.

The integrator 60 time-integrates the rotational speed ωe estimated by the PI controller 33a as shown by the following equation (15).
θ = ∫ωedt (15)
That is, the integrator 60 can determine the conversion angle θ to the rotating coordinate system. The output of the integrator 60 becomes the estimated phase angle of the voltage vector to be output next.

On the other hand, control for decreasing or increasing the magnitude of the voltage vector is performed by the voltage controller 44 (see FIG. 1). Specifically, the output speed estimator (104) rotational speed ωe estimated is converted by the transducer 41 to the mechanical rotation speed omega _m by the comparator 43, comparator 43, mechanical rotary Compare the speed ω _m with the command speed ω ^*
Δω = ω ^* −ω _m (16)
Is obtained and output to the voltage controller 44. The voltage controller 44 controls the magnitude of the voltage vector according to the output speed difference Δω.

For example, if the speed difference Δω is positive, the voltage controller 44 advances the voltage vector (δ axis) to generate a surplus torque, and thus reduces the magnitude (v _δ ) of the voltage vector. If the speed difference Δω is negative, the voltage controller 44 increases the voltage vector magnitude (v _δ ) because the voltage vector (δ axis) is delayed and a torque shortage occurs. That is, the voltage controller 44 controls the magnitude of the voltage vector so that the speed difference Δω becomes 0, assuming that the speed difference Δω is proportional to the surplus torque with respect to the advance angle. In other words, in order to generate a voltage vector that matches the target phase difference, the voltage controller 44 controls the magnitude of the voltage vector so that the torque is converged with the command rotational speed as a target.

As shown in FIG. 6, the voltage controller 44 includes a generation unit 44a and a PI controller 44b. The generation unit 44a outputs v _γ = 0 in order to redefine the rotating coordinate system in which the direction of the voltage vector (v _γ , v _δ ) coincides with the δ axis. The PI controller 44b performs the P control and the I control so that the speed difference Δω becomes 0, whereby the magnitude of the voltage vector (v _γ , v _δ ) on the rotating coordinate system (γ-δ coordinate system). That is, v _δ is determined and output.

  Next, the control flow of the synchronous motor M will be described with reference to FIG. FIG. 7 is a flowchart showing a method for controlling the synchronous motor M.

In step S1 (first step), the detection unit 50 detects (picks up) amplitudes of at least two-phase currents applied to the synchronous motor M. Specifically, the current sensor 51 detects the amplitude of the U-phase current i _U and outputs it to the computing unit 20. The current sensor 52 detects the amplitude of the W-phase current i _W and outputs it to the computing unit 20. Then, the calculation unit 20 uses the current vector (i _U , i _W ) in the fixed coordinate system (UVW coordinate system) when the driving unit 10 drives the synchronous motor M as the current in the rotational coordinate system (γ-δ coordinate system). Convert to vector (i _γ , i _δ ).

In step S2 (second step), the calculation unit 20 uses the current vector (i _γ , i _δ ) in at least the converted rotational coordinate system to use the current vector I and the voltage vector V applied to the synchronous motor M. Is obtained.

In step S3 (third step), the estimation unit 30 compares the phase difference Δθ between the current vector I and the voltage vector V applied to the synchronous motor M with the target phase difference Δθ ^* . If the phase difference Δθ is larger than the target phase difference Δθ ^* (error Δθd <0) by the feedback control operation of the estimation unit 30, the process proceeds to step S4, where the phase difference Δθ is smaller than the target phase difference Δθ ^* (error). If Δθd> 0), the process proceeds to step S5. If the phase difference Δθ is equal to the target phase difference Δθ ^* (error Δθd = 0), the process proceeds to step S6.

  In step S4 (third step), the estimation unit 30 retards the phase angle of the voltage vector on the rotating coordinate system (γ-δ coordinate system).

  In step S5 (third step), the estimation unit 30 advances the phase angle of the voltage vector on the rotating coordinate system (γ-δ coordinate system).

  Note that the processing in steps S3 to S5 conceptually shows the feedback control operation (for example, by the PI controller 33a) of the estimation unit 30, and is automatically performed by the estimation unit 30 (for example, the PI controller 33a). Done.

In step S6 (third step), the estimation unit 30 adjusts the phase angle of the voltage vector (v _γ , v _δ ) on the rotational coordinate system (γ-δ coordinate system) (UVW coordinates). The rotation speed ωe of the voltage vector in the system) is estimated. Control unit 40 converts the rotational speed ωe of the voltage vectors estimated by the estimation unit 30 to the mechanical rotation speed omega _m of the rotor in a synchronous motor M.

In step S7 (fourth step), the control unit 40 compares the mechanical rotational speed ω _m corresponding to the estimated rotational speed ωe with the command rotational speed ω ^* . If the rotation speed ω _m is greater than the command rotation speed ω ^* (speed difference Δω <0, that is, the voltage vector (δ axis) is advanced) by the feedback control operation of the control unit 40, the process proceeds to step S8. When the rotational speed ω _m is smaller than the command rotational speed ω ^* (speed difference Δω> 0, that is, the voltage vector (δ axis) is delayed), the process proceeds to step S9, where the rotational speed ω _m is the command rotational speed ω. ^If it is equal to ^* (speed difference Δω = 0), the process proceeds to step S10.

In step S8 (fourth step), the control unit 40 decreases the magnitude (v _δ ) of the voltage vector on the rotating coordinate system (γ-δ coordinate system).

In step S9 (fourth step), the control unit 40 increases the magnitude (v _δ ) of the voltage vector on the rotating coordinate system (γ-δ coordinate system).

  Note that the processing in steps S7 to S9 conceptually shows the feedback control operation (for example, by the PI controller 44b) of the control unit 40, and is automatically performed by the control unit 40 (for example, the PI controller 44b). To be done.

In step S10 (fifth step), the driving unit 10 drives the synchronous motor M so that the synchronous motor M operates at a voltage corresponding to the voltage vector (v _γ , v _δ ) controlled by the control unit 40. To do.

  Steps S1 to S10 are repeated. That is, by repeatedly performing the processing of step S3 to step S5, the estimation unit 30 adjusts the phase angle of the voltage vector on the rotating coordinate system so that the phase difference obtained in step S2 matches the target phase difference. . By repeatedly performing the processes in steps S7 to S9, the control unit 40 controls the magnitude of the voltage vector in the rotational coordinate system so that the rotational speed estimated in step S6 becomes a value corresponding to the command rotational speed. To do.

  As described above, according to the embodiment, the phase difference between the voltage vector and the current vector applied to the synchronous motor M is obtained by the ratio of the two components of the current vector in the rotating coordinate system (γ-δ coordinate system). be able to. That is, since phase control can be performed using a direct current amount (amount in which the alternating current component is effectively canceled), the phase difference between the voltage vector and the current vector applied to the synchronous motor M can be obtained by simple processing. . As a result, the configuration of the control device can be simplified. That is, the phase difference between the current vector and the voltage vector applied to the synchronous motor can be obtained with a simple configuration and can be controlled to match the target phase difference.

  In addition, by converting to a rotating coordinate system, each of the voltage vector and current vector, which are originally AC quantities, can be controlled as a DC quantity (a quantity in which the AC component has been effectively canceled), so instantaneously and sequentially It becomes easy to correct the phase. That is, the phase difference can be instantaneously corrected, and the phase can be adjusted more finely.

  Further, on the rotating coordinate system, the phase difference between the voltage vector and the current vector can be expressed by a tan function that takes a value obtained by using each component of the voltage vector and the current vector (see Expression (10)). . Then, by redefining the rotational coordinate system so that the direction of the voltage vector coincides with the δ axis and using it for the control, the equation (10) becomes a simpler equation (11), and the γ axis current and the δ axis current Therefore, it is easy to obtain the phase difference without using a complicated calculation.

  In order to perform instantaneous phase adjustment, PI control is performed so that the error between the target phase difference and the detected phase difference becomes zero, so that the rotational speed of the γ-δ axis is estimated and the rotational speed is integrated. If the phase of the γ-δ axis is used, the voltage vector can be output at an optimum position (with a current and an arbitrary phase difference angle). Thereby, phase correction can be performed sequentially.

  In addition, in order to determine the magnitude of the voltage vector that is instantaneously phase-adjusted, by correcting the voltage value of the δ axis so that the output of the speed estimator of the γ-δ axis and the synchronous command rotational speed match, Continuous synchronous operation can be maintained with any voltage-current phase difference.

8 uses the converted current vector in the rotating coordinate system (γ-δ coordinate system) and the voltage vector in the rotating coordinate system controlled by control unit 140. The phase difference between the current vector applied to the synchronous motor M and the voltage vector may be obtained. Specifically, the voltage controller 144 of the control unit 140 also outputs the voltage vector (v _γ , v _δ ) in the rotating coordinate system (γ-δ coordinate system) to the phase difference detector 122 of the calculation unit 120. At this time, the voltage controller 144 may control v _γ to a value other than zero. The phase difference detector 122 obtains the phase difference Δθ between the current vector and the voltage vector applied to the synchronous motor M by Expression (10).

  Even in this case, on the rotating coordinate system, the phase difference between the voltage vector and the current vector can be expressed by a tan function that takes a value obtained by using each component of the voltage vector and the current vector (formula Therefore, if a target phase difference is prepared as a tan value, an error component of the phase difference can be generated without using arctan calculation. That is, the phase difference can be obtained without using complicated calculations.

  As described above, the synchronous motor control device according to the present invention is useful for controlling a synchronous motor, and is particularly suitable for controlling a sensorless synchronous motor.

DESCRIPTION OF SYMBOLS 1,100 Control apparatus 10 Drive part 20,120 Operation part 30 Estimation part 40,140 Control part 50 Detection part 60 Integrator

Claims (8)

A control device for a synchronous motor that receives a command rotational speed from outside and controls a sensorless synchronous motor to operate at the command rotational speed,
A drive unit for driving the synchronous motor;
A current vector in a fixed coordinate system when driving the synchronous motor by the drive unit is converted into a current vector in a rotating coordinate system, and applied to the synchronous motor using at least the converted current vector in the rotating coordinate system. An arithmetic unit for obtaining a phase difference between a current vector and a voltage vector to be
The phase angle of the voltage vector is adjusted on the rotating coordinate system so that the phase difference obtained by the calculation unit matches the target phase difference, and the phase angle of the voltage vector is adjusted on the rotating coordinate system. An estimation unit for estimating a rotation speed of a voltage vector in the fixed coordinate system;
When the voltage vector is rotated at the rotation speed estimated by the estimation unit in the fixed coordinate system according to the difference between the rotation speed according to the estimated rotation speed and the command rotation speed, the phase difference and the A control unit for controlling the magnitude of the voltage vector in the rotating coordinate system so that a deviation from the target phase difference does not occur;
With
The drive unit drives the synchronous motor so that the synchronous motor operates at a voltage corresponding to a voltage vector controlled by the control unit.   When the rotation speed according to the estimated rotation speed is greater than the command rotation speed, the control unit decreases the magnitude of the voltage vector, and the rotation speed according to the estimated rotation speed is the command rotation. If smaller than speed, increase the magnitude of the voltage vector
The synchronous motor control device according to claim 1.   The controller obtains the difference by subtracting a rotational speed corresponding to the estimated rotational speed from the command rotational speed, and when the difference is positive, cancels a surplus of torque according to the difference. The magnitude of the voltage vector is decreased, and if the difference is negative, the magnitude of the voltage vector is increased so as to compensate for the torque shortage according to the difference.
The control apparatus for a synchronous motor according to claim 2.   The estimation unit increases the rotation speed to be estimated when the calculated phase difference is smaller than the target phase difference, and decreases the rotation speed to be estimated when the calculated phase difference is larger than the target phase difference.
The synchronous motor control device according to any one of claims 1 to 3, wherein the control device is a synchronous motor control device.   The estimation unit obtains a phase error by subtracting a value corresponding to the obtained phase difference from a value corresponding to the target phase difference, and advances the phase angle of the voltage vector when the phase error is positive. If the phase error is negative, the rotational speed to be estimated is decreased so as to retard the phase angle of the voltage vector.
The synchronous motor control device according to claim 4, wherein The rotating coordinate system is composed of a δ axis and a γ axis orthogonal to each other,
The arithmetic unit converts the current vector in the fixed coordinate system into a current vector in a rotating coordinate system defined so that a direction of a voltage vector controlled by the control unit coincides with the δ axis. The control apparatus of the synchronous motor of any one of Claim 1 to 5 . The arithmetic unit is configured such that the δ-axis component of the current vector in the rotating coordinate system is iδ, and the γ-axis component is iγ.
tan (Δθ) = i _γ / i _δ
The synchronous motor control device according to claim 6 , wherein a phase difference Δθ between a current vector and a voltage vector applied to the synchronous motor is obtained by the following equation. A control method for a synchronous motor that receives a command rotational speed from outside and controls a sensorless synchronous motor to operate at the command rotational speed,
Converting a current vector in a fixed coordinate system when driving the synchronous motor by the drive unit into a current vector in a rotating coordinate system;
Using at least the converted current vector in the rotating coordinate system to determine a phase difference between a current vector and a voltage vector applied to the synchronous motor;
The fixed coordinates in a state where the phase angle of the voltage vector is adjusted on the rotating coordinate system and the phase angle of the voltage vector is adjusted on the rotating coordinate system so that the obtained phase difference matches the target phase difference. Estimate the rotational speed of the voltage vector in the system,
The rotational speed according to the estimated rotational speed and the rotational speed so as not to cause a deviation between the phase difference and the target phase difference when the voltage vector is rotated at the estimated rotational speed in the fixed coordinate system. According to the difference in the command rotational speed, the magnitude of the voltage vector in the rotating coordinate system is controlled,
A method for controlling a synchronous motor, wherein the synchronous motor is driven so that the synchronous motor operates at a voltage corresponding to the controlled voltage vector.

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