JP2001178174A - Speed control method for synchronous motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily perform a vector control operation by solving the problem that when a synchronous motor is in a low-speed region, the induced voltage in the synchronous motor is dropped, that the estimated accuracy of a magnetic axis is degraded, and that when the vector control is performed in a low-speed region, the magnetic axis is lost making vector control operation impossible. SOLUTION: Sensorless vector control is performed, by using the rotational speed and the rotor position of the synchronous motor 6. While it is assumed that a d-axia as a true magnetic axis exists in a phase which is deviated from a γ-axis by a load angle θe, a positive current is made to flow to the γ-axis. Thereby, a torque which is proportional to iγ sin θe and which advances in the direction of the γ-axis is generated in the magnetic axis. Thereby, errors in a d-q axis as a true magnetic axis and a γ-δ axis as a control axis are eliminated. Even when a load is applied, the γ-δ axis as the control axis is made to coincide with the d-axis as the magnetic axis of the synchronous motor, and the vector control can be performed satisfactorily.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous motor speed control method, and more particularly to a sensorless speed control method for a permanent magnet synchronous motor.

[0002]

2. Description of the Related Art Conventionally, sensorless vector control of a synchronous motor has been performed by calculating a difference between a stator current converted into a γ-δ axis coordinate system set on a magnetic pole of a rotor and a current estimated value previously estimated and γ−δ. The voltage command converted into the δ-axis coordinate system is input, and the current, induced voltage, and rotor speed in the γ-δ axis coordinate system are estimated. Further, from the estimated value of the γ-axis induced voltage and the estimated value of the angular velocity of the rotor estimated by this method,
Dq coordinates set on the permanent magnet of the rotor and the γ-δ
Estimate the angle of deviation from the coordinates and correct the rotor position. Vector control is performed using the angular velocity and magnetic axis position information estimated by the above method.

[0003]

However, according to the above-mentioned conventional technique, as the synchronous motor rotates at a low speed, the synchronous motor induced voltage decreases, and the estimation accuracy of the magnetic axis deteriorates. When the vector control is performed, there is a problem that the magnetic axis is lost and control becomes impossible. Also, when a large load is applied to the synchronous motor in the low-speed range, the load angle becomes too large, and the angle difference between the control axis and the synchronous motor magnetic axis increases, and the control axis and the magnetic axis must be controlled to match. There was a problem that control could not be smoothly shifted to control and control was lost. Therefore, an object of the present invention is to provide a good synchronous motor speed estimation method capable of specifying a magnetic axis with high accuracy even in a low speed range. Still another object of the present invention is to provide a synchronous motor speed control method capable of making the control axis coincide with the magnetic axis and shifting to vector control satisfactorily even when a large load is applied to the synchronous motor in a low speed range.

[0004]

Means for Solving the Problems To achieve the above object,
Therefore, the present invention uses a permanent magnet as a rotor and places it on a magnetic pole of the rotor.
The γ-δ axis assumed on the rotor coincides with the set dq axis.
Sensorless Control Method for Synchronous Motor Controlled to Match
At time k · T_S Time (where k = 0, 1, 2,
3, ..., T_S Is the sampling time) synchronous motor
At least two phases of stator current supplied to the
By converting the stator current to a γ-δ coordinate system,
Deriving γ-axis current iγ (k) and δ-axis current iδ (k)
Γ-axis current iγ (k) and δ-axis current iδ
(K) and the γ-axis current iγ estimated in the previous control loop
_est(K) and δ-axis current iδ_estDifference iγ from (k)
(K) -iγ_est(K) and iδ (k) -iδ
_est(K) is the correction amount, and the voltage converted to the γ-δ axis coordinate system
Command value Vγ^*(K) and Vδ^*(K) as input, synchronous electric
Induced Electricity of γ Axis Generated by Rotating Machine Rotor
Pressure εγ (k) and δ-axis induced voltage εδ (k)
State inference as a disturbance to current response when not rotating
A time constant (k + 1) · T_S Γ-δ axis coordinates of seconds
Current iγ in the system_est(K + 1) and iδ_est(K +
1) and induced voltage εγ_est(K + 1) and εδ_est
(K + 1), and the estimated induced voltage εδ
_estDetermine the sign of the rotor speed from the sign of (k + 1)
And the induced voltage εγ_est(K + 1) and εδ_est(K +
From the sum of squares of 1) and the code determined above, the angular velocity of the rotor
ω_rmThe estimated value ω of (k + 1)_{rme st}Estimate (k + 1)
And the δ-axis direction current command is changed to the synchronous motor speed command ω_rref 
And speed estimate ω_{rm est}Deviation from (k + 1) multiplied by gain
Synchronous motor rotating torque derived from feedback control
And the current command in the γ-axis direction is positive,
To generate torque to restrain the d axis to the γ axis
Features. In addition, sensorless control of synchronous motors
Method, the magnetic axis of the synchronous motor is d-axis, 90 ° from the d-axis.
The advanced axis is the q axis, and the synchronous motor rotation speed ω_rm Rotate with
The coordinate dq axis and the designated magnetic axis of the synchronous motor from γ and γ
Set the axis advanced by 90 ° to δ and set the synchronous motor rotation command speed ω_rm 
^* Set the γ-δ axis to rotate at
γ ^* , Current command iδ in the δ-axis direction^* And the magnetic axis d axis
Generates torque to restrain at an angle advanced from the γ-axis.
And the synchronous motor speed command ω
_rm ^* -Axis current equation as a function of synchronous motor induced voltage disturbance
Speed estimation value ω derived from disturbance observer created
_{rm est}Feedback control that multiplies the deviation from
Δ-axis current command as synchronous motor induced voltage disturbance
Derived from disturbance observer created from the γ-axis current equation
Derived from the estimated disturbance value via the proportional integral controller
Angle correction current command iδθ^* Command speed ω_rm ^* so
The feature is to make the rotating γ axis coincide with the true magnetic axis d axis.
are doing.

According to such a speed control method for a synchronous motor, when a positive direct current iγ flows through an arbitrary designated axis γ axis, the true magnetic axis d axis lags the γ axis by the load angle θ _e . if present in the phase, when the load angle theta _e in no load is small, the magnetic axis d-axis torque is generated toward the γ-axis direction that is proportional to iγsinθ _e. Therefore, since the true magnetic axis d-axis is always γ axis and the d-axis under torque as towards the designated axis γ axis coincides, by passing a γ-axis current command i? ^* In the low speed range, magnetic even at low speed The axis can be specified, and excellent vector control can be performed. However, when constraining the magnetic axis d-axis, the d-axis causes a simple oscillation around the γ-axis because the damping factor of a synchronous machine having no braking winding is almost 0. By setting the current command value to the δ-axis current, transient vibration of the d-axis is suppressed. On the other hand, the disturbance estimation value εγ _est derived from the γ-axis current equation estimates ε sin θ _e when the synchronous motor induced voltage is ε. . Therefore, when the load angle is small, εγ _est is a value proportional to the load angle.
Although the magnetic axis d-axis can be constrained by iγ ^* , it cannot be constrained particularly at low speeds when the load angle is large. Therefore, the correction current command iδ obtained by proportionally integrating the disturbance estimation value εγ _est. By adding θ ^* to the δ-axis current command and flowing a constraint current as a correction current also to the δ-axis, the correction current flows until εγ _est is 0, that is, the γ-axis and the d-axis match. Excessive opening of the load angle is suppressed, and γ
The axis and the d-axis can be matched.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a control system to which a speed control method for a synchronous motor according to a first embodiment of the present invention is applied. The first embodiment shown in FIG. 1 is basically, for example, disclosed in Japanese Patent Application Laid-Open No. 9-1916.
98, a sensorless vector control system is constructed using the rotational speed and the rotor position of the synchronous motor estimated by the method of estimating the speed of the permanent magnet type synchronous motor, the method of estimating the rotor shift angle, and the method of correcting the rotor position. However, in this estimation method, since the speed and the rotor position of the synchronous motor are estimated from the induced voltage information, the induced voltage information is small in the estimated low-speed range, and the control axis γ-δ axis and the synchronous motor magnetic field are not used. Error correction between the d and q axes cannot be performed,
Good vector control cannot be performed. Therefore, when a positive current is applied to the γ-axis, if the true magnetic axis d-axis is in a phase shifted from the γ-axis by the load angle, the torque in the γ-axis direction proportional to the magnetic axis is controlled. appear. For this reason, the error between the true magnetic axis dq axis and the control axis γ-δ axis is eliminated, the method is improved by a method that enables good vector control, and the control in the high-speed range is performed based on the above disclosed example. The control system described in Japanese Patent Application Laid-Open No. 9-191698 is improved so that good vector control can be ensured over a high speed / low speed range.

In FIG. 1, an angular velocity command ω _rm ^* and an estimated angular velocity ω _{rm est} (hereinafter, the estimated value is represented by est) are input to a speed controller 1, and the speed controller 1 outputs a δ-phase current command iδ ^* . I do. The δ-phase current controller 2 receives iδ ^* and the estimated δ-phase current iδ _{est 2} from the current corrector, and outputs a δ-phase current command Vδ ^* . On the other hand, the positive γ-phase current command iγ ^* and the estimated γ-phase current value iγ _{est 2} are input to the γ-phase current controller 3,
The γ-phase current controller 3 outputs a γ-phase voltage command Vγ ^* . Voltage commands Vδ ^* , Vγ ^*, and γ-δ axis position corrector 11
Is input to the vector control circuit 4, and the absolute value of the voltage value (Vδ ² + Vγ ² ) ^1/2 and the phase tan ⁻¹ (Vδ / Vγ) in the voltage output direction from the γ axis are output. The signal is input to the inverter circuit 5 and firing is performed. On the other hand, γ
The δ-axis current / induced voltage estimator 8 calculates the γ-phase current iγ and the δ-phase current iδ obtained from the stator currents i _U and i _V of the synchronous motor 6 via the phase converter 7 and the position of the γ-δ axis. And the voltage commands Vδ ^* and Vγ ^* , and the γ−δ phase current estimated value iγ
_est, and iδ _est, γ-δ phase induced voltage Ipushironganma _est and ε
Output δ _est . εγ _est and εδ _est are input to the angular velocity deriving unit 9 to derive an estimated angular velocity ω _{rm est} . The ω _{rm est} and the εγ _est are input to the deviation angle θ _{e est} deriving unit 10, and the deviation angle θ between the γ-δ axis and the dq axis is obtained.
_{e est} is derived. This is input to the γ-δ axis position corrector 11 to execute the γ-δ axis position correction, and the current corrector 1
2 is performed. The motor constant identifier 13 is a configuration newly added in the present embodiment, and includes Rs, Lq, Ld
Identify the synchronous motor constants, etc. and detect the d-axis due to the change in inductance, or input the induced voltage estimation value εδ _est as the disturbance estimation value and calculate the deviation angle between the dq axis and the γ-δ axis by the known εcos θ _{e est} , iγ ^*, which is a positive current that is estimated from and is supplied to the γ axis with a positive current appropriate for restraining at low speed, is output.

Next, the operation will be described. First, in the case of a high-speed control operation, at least two phases of current supplied to the synchronous machine at k · T _S seconds, for example, i _U (k),
i _V (k) is detected and converted by the phase converter 7 into the γ-δ axis coordinate system corrected in the previous loop to obtain i γ (k), i δ
(K) is derived. Next, the voltage commands Vγ ^* (k) and Vδ ^* (k) converted into the γ-δ coordinate system are input using the state estimator configured in the γ-δ axis current and induced voltage estimator 8. Then, an estimated value iγ at (k + 1) · T _S seconds is obtained by a known method.
_{est (k + 1), iδ} est (k + 1), εγ est (k +
1) derive εδ _est (k + 1). Angular velocity deriving device 9
, The sign of the angular velocity is determined from the sign of the estimated εδ _est (k + 1), and this sign, εγ _est (k + 1) and ε
ω _{rm est} (k + 1) is derived from the sum of squares of δ _est (k + 1). The deviation angle θ _e derivation unit 10 εγ _est (k +
1) and ω _{rm est} (k + 1) are used to determine θ _{e est} (k + 1), and the γ-δ axis position corrector 11 corrects the γ-axis position. Next, assuming that the γ-axis has been converted by kρθ _{e est} (k + 1), the γ-phase and δ-phase current correctors 12
1) Initial value iγ _est (k + 1), iδ during loop
_est (k + 1), εγ _est (k + 1), εδ _est (k +
Modify 1). Further, in the low speed range, the motor constant identifier 13 outputs iγ ^* for flowing a positive current to the γ-axis to the γ-axis current controller 3 and outputs iγsin to the magnetic pole d-axis.
A torque is generated in the γ-axis direction in proportion to θ _e to eliminate an error between the magnetic axis dq and the control axis γ-δ, thereby enabling excellent vector control.

Next, a second embodiment of the present invention will be described.
This will be described with reference to the drawings. FIG. 2 shows a second embodiment of the present invention.
Control system to which the synchronous motor speed control method according to the
It is a block diagram of a stem. FIG. 3 shows the control system shown in FIG.
It is a flowchart of operation | movement of a system. The second shown in FIG.
In this embodiment, the load is further increased compared to the previous embodiment, and the load is reduced.
When the load angle θe is too wide, a positive current is applied to the δ axis
Suppress the transient vibration of the d-axis and the load angle, and
Bundling reduces the error between the magnetic axis dq and the control axis γ-δ axis.
Eliminates and improves control when load increases (especially at low speeds)
It is intended. In FIG. 2, the angular velocity command ω_rm ^*
And the estimated angular velocity ω_{rm est} Input to speed controller 1
And the speed controller 1 outputs the δ-phase current command iδ^* Out
Power. Also, the induced voltage estimated value εγ_estIs the δ-axis current command
Is input to the corrector 14 (proportional-integral controller), and
inθ_{e est} From the deviation angle θ_eΔ axis complement
Positive current command iδθ^* Is output. δ phase current controller
2 is iδ^* And iδθ^* -Phase current estimation from the current and the current compensator
Value iδ_{est 2} And the δ phase voltage command Vδ^* Output
I do. This suppresses the transient vibration of the d-axis,
Positive current iδθ^* Load angle is too wide
Pull and restrain the magnetic axis so that it does not come out. On the other hand, as in FIG.
Phase current command iγ^* And the estimated value of the γ-phase current iγ_{est 2} Is the γ axis
Γ-axis current controller which is input to the current controller 3
3 is a γ-phase voltage command Vγ^* Is output. Voltage command Vδ^* 
And Vγ^* And γ output from the γ-δ axis position corrector 11
The −δ-axis position is input to the vector control circuit 4 and the voltage value
Absolute value (Vδ^Two + Vγ ^Two )^1/2, And voltage output from the γ axis
Phase tan in force direction^-1(Vδ / Vγ) is the number of inverters
It is input to the road 5 and the ignition is performed. On the other hand, γ-δ axis current
The induced voltage estimator 8 calculates the stator current i of the synchronous motor 6
_UAnd i_V Is the γ-phase current iγ obtained via the phase converter 7,
δ-phase current iδ, γ-δ axis position, and voltage command Vδ
^* , Vγ^* Is input, and the calculation of the well-known expression (1) is performed.
γ-δ phase current estimated value iγ_est , Iδ_est And the γ-δ phase
Induced voltage εγ_est , Εδ_est Is output. ε
γ_est, Εδ_estIs input to the angular velocity deriving device 9,
By executing equations (2) and (3), angular velocity estimation
Value ω_{rm est} Is derived. Also, the speed command value ω_rm ^*
Is input to the γ-δ axis position corrector 11, and in the equation (4), γ
The position correction of the -δ axis is executed.

[0010]

(Equation 1)

Next, the basic braking operation will be described with reference to the flowchart of FIG.
This will be explained by a chart. KT_S At the second
Supplied current for at least two phases, for example, i
_U(K), i_V(K) is detected (step S1), and the
Into the γ-δ axis coordinate system corrected by the step, iγ (K),
iδ (K) is derived (step S2). γ-δ coordinate system
Input the converted voltage commands Vγ (K) and Vδ (K)
(Step S3) According to the equation (1), (K + 1) · T_S 
Second estimated value iγ_est(K + 1), iδ_est(K +
1), εγ_est(K + 1), εδ_estLeads to (K + 1)
Issue (Step S4). Estimated εδ_est(K +
The sign of the angular velocity is determined from the sign of 1) (step S).
5), this sign, and the equations (2) and (3), εγ
_est(K + 1) and εδ _estFrom the sum of squares of (K + 1), ω
_{rm est}(K + 1) is derived (step S6).
The position of the γ-axis is corrected by the equation (4) (Step S)
7). In this way, the load is large and the load
θ_e Is too open, iγ^*Of d-axis by
Not only iδθ to the δ axis^* Negative by retraction by
By suppressing the opening of the load angle θe from being too large, the error between the dq axis and the γ-δ axis
Eliminate the difference and perform the control according to the above flowchart
This enables good vector control. In addition,
In Japanese Patent Application Laid-Open No. 10-174499, the range from a low speed range to a high speed range is described.
Γ-δ axis so that the control change
Rotation speed ω_RWhen determining γ, the rotational speed command ω
_RREF So that it decreases as the absolute value of
The distribution gain K1 is set to
Prepare a distribution gain K2 that is set to
In the speed range, the ratio of K2 is designed to be sufficiently larger than K1,
In the speed range, the ratio of K1 is designed to be larger than K2,
The same algorithm from low to high speed with little torque fluctuation
A control method has been proposed. But in this case too
This control method is based on the assumption that the load is
Not applicable when the angle difference between d axis and γ axis is large
If the load angle is large in this case as well,
According to the embodiment, iγ^*, Iδ θ^*A positive current
If the d-axis is retracted and constrained to perform the above control,
Good vector control can be expected over the high-speed range.

[0012]

As described above, according to the present invention,
In the sensorless vector control method, a positive current is applied to the γ-axis to generate torque for restraining the magnetic axis d-axis, so that the speed control of the synchronous motor can be favorably performed even at a low speed. In addition, by controlling the phase in which the magnetic axis is pulled in the control in the low-speed range to the phase leading from the γ axis in accordance with the load angle, the control axis γ axis and the synchronous motor magnetic axis d axis can be controlled even when the load angle increases. By making them match, it is possible to favorably shift to vector control.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control system to which a speed control method for a synchronous motor according to a first embodiment of the present invention is applied.

FIG. 2 is a block diagram of a control system to which a speed control method for a synchronous motor according to a second embodiment of the present invention is applied.

FIG. 3 is a flowchart of an operation of the control system shown in FIG. 2;

[Explanation of symbols]

 Reference Signs List 1 speed controller 2 δ-axis current controller 3 γ-axis current controller 4 vector control circuit 5 inverter circuit 6 synchronous motor 7 phase converter 8 γ-δ-axis current / induced voltage estimator 9 angular velocity deriver 10 deviation angle θe deriver 11 γ −δ axis position corrector 12 γ phase / δ phase current corrector 13 Motor constant identifier 14 Axis current command corrector

Claims (2)

[Claims] A permanent magnet is used as a rotor, and a magnetic pole on the rotor is provided.
The γ-δ axis assumed on the rotor is
Sensorless speed control of synchronous motors controlled to match
In the method, time k · T_S Time (however, k = 0, 1, 2, 3,...,
T_S Is supplied to the synchronous motor at sampling time)
Detecting at least two phases of stator current,
By converting the current into a γ-δ coordinate system, the γ-axis current i
γ (k) and δ-axis current iδ (k) are derived, and these γ-axis
The current iγ (k) and the δ-axis current iδ (k) and the previous control
-Axis current iγ estimated in the loop_est(K) and δ-axis current
iδ_estDifference from (k) iγ (k) −iγ_est(K) and
iδ (k) -iδ_est (K) is the correction amount, γ-δ axis coordinates
Voltage command value Vγ converted to the system^*(K) and Vδ^*(K)
Input, and is triggered by the rotation of the synchronous motor rotor.
The generated γ-axis induced voltage εγ (k) and δ-axis induced voltage εδ
(K) to the current response when the rotor is not rotating
A state estimator is constructed as a disturbance that takes time (k + 1) · T
_SCurrent iγ in the γ-δ axis coordinate system in seconds_est(K + 1)
And iδ_est(K + 1) and induced voltage εγ _est(K +
1) and εδ_est(K + 1), and this estimated
Induced voltage εδ _estFrom the sign of (k + 1), the speed of the rotor
The sign of the induced voltage εγ_est(K + 1) and εδ
_{est (}From the sum of squares of (k + 1) and the determined code,
Trochanter angular velocity ω_rmEstimate the estimated value of (k + 1), δ axis
Direction current command to synchronous motor speed command ω_rrefAnd speed guessing
Constant value ω_{rm est (}k + 1)
Generates synchronous motor rotation torque derived from feedback control
And the current command in the γ-axis direction is positive, and the magnetic axis d-axis is
It is characterized by generating torque for restraining to the γ axis
Speed control method for synchronous motors. 2. A sensorless speed control method for a synchronous motor, wherein the magnetic axis of the synchronous motor is d-axis, and the axis advanced by 90 ° from the d-axis is q.
Axis, and the coordinate d− rotating at the synchronous motor rotation speed ω _rm
The designation magnetic axis of the q-axis and the synchronous motor gamma, the axis leading 90 ° from gamma and [delta] Set the gamma-[delta] axes rotating at synchronous motor rotation command speed ω _{r m} ^*, γ axial current command i? ^* , The current command iδ ^* in the δ-axis direction is positive, a torque for restraining the magnetic axis d-axis at an angle advanced from the γ-axis is generated, and the δ-axis current command includes a synchronous motor speed command ω _rm ^* and the deviation between the synchronous motor induced voltage disturbance and the δ axis current estimated speed value derived from the disturbance observer created from equation omega _Rmest derived from feedback control for gain-multiplied, and the synchronous motor induced voltage disturbance δ-axis current command γ Deviation angle correction current command iδ derived from a disturbance observer derived from a disturbance observer created from the shaft current equation via a proportional integral controller
A speed control method for a synchronous motor, wherein θ ^* is added and a γ axis rotating at a command speed ω _rm ^* is made to coincide with a true magnetic axis d axis.