JP3982091B2 - Control device for synchronous motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a synchronous motor, and more particularly to prevention of torque loss (step-out) during an overload.
[0002]
[Prior art]
In the vector control of the synchronous motor, the excitation current component and the torque current component of the motor current are controlled using the MT axis of the rotating magnetic field coordinate rotated by the load angle δ from the dq axis of the rotating magnetic pole coordinate as a reference coordinate (FIG. 2). . Here, the T-axis is selected so that the component of the magnetic flux Φ is zero. That is, by selecting the M-axis so as to coincide with the direction of the magnetic flux, the generated torque of the motor is changed to the current IT on the T-axis. It becomes possible to control linearly using. This is the principle of vector control of the synchronous motor.
[0003]
Also, the M-axis component IM of the armature current Is zero, the magnetic flux and current are orthogonal (Φ⊥I), and the motor power factor can be controlled to 1. The relationship of the coordinate axes at this time is as shown in FIG. Magnetic flux Φ is IT And field current If Is present on the M axis with a magnetomotive force equivalent to Iφ. Itself is zero.
[0004]
When the synchronous motor is driven using vector control, the load angle δ changes depending on the magnitude of the load. It is known that the range in which the synchronous motor can be driven stably is such that the load angle δ is −90 degrees <δ <90 degrees. In particular, when the load suddenly changes in the field weakening region, there is a problem that the load angle of the synchronous motor transiently exceeds the stable range and becomes out of control such as step-out.
[0005]
In order to solve this problem, for example, there is one described in JP-A-3-212191. In this method, the load angle δ is set to the set value δMAX during load operation. If it exceeds, it is judged that the limit of the stable operation, and a variable limiter circuit for limiting the torque current set value is provided.
[0006]
[Problems to be solved by the invention]
In the conventional method described above, the set value δMAX If set to a low value, even in the stable region, IT Is limited, and the torque generated by the motor is reduced. Also, δMAX If you set a large value, once you enter an unstable region (δ> δMAX The recovery time until δ returns to the stable region becomes longer. When δ is in the unstable region, it is an abnormal state for the synchronous motor, and it is desired to recover to the stable region as soon as possible.
[0007]
An object of the present invention is to provide a control device that quickly recovers to a stable region when δ enters an unstable region.
[0008]
[Means for Solving the Problems]
When the load angle δ exceeds a preset value, the synchronous motor control device according to the present invention determines that the stable operation limit has been reached, and switches the field current command to a preset large current value or By switching the applied voltage to the circuit to a large value and increasing the field current, it is quickly returned to the stable region.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a synchronous motor variable speed system according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a winding synchronous motor having a field winding on the secondary side, 2 a speed command generator for giving a rotational speed command ωre ^* to the synchronous motor 1, and 3 a speed detection value ωre , to match the speed command? re ^*, speed controller for calculating a torque current command IT ^*, 4 is a torque current command IT ^*, the value of MT coordinate axis relative to the magnetic flux position, the magnetic pole position (rotor position ) Is a coordinate converter that converts the value to the value of the dq coordinate axis, and 5 is a current command value (Id ^* ) in which the detected value (IdFB, IqFB) of the synchronous motor armature current is the output of the coordinate converter 4 ^. , to match the Iq ^*), the voltage command Vd ^*, and the armature current controller for calculating a Vq ^*, 6 is the voltage command Vd ^*, and the Vq ^*, the voltage command on the three-phase alternating current axis (Vu ^* , Vv ^* , Vw ^* ), the coordinate converter 7 is based on the voltage commands Vu ^* , Vv ^* , Vw ^* . Accordingly, a power converter that supplies power to the synchronous motor 1, 8 a current detector that detects an armature current flowing through the synchronous motor, and 9 a voltage detection that detects an armature voltage applied to the synchronous motor 1. 10 is a speed / position detector for detecting the rotational speed of the synchronous motor 1 and the magnetic pole position, and 11 is a coordinate converter for converting the detected values of the armature current and the armature voltage into values on the dq axis, 12 is a magnetic flux observer that estimates and calculates the magnetic flux and load angle of the synchronous motor 1 based on the current and voltage detection value of the synchronous motor 1, and 13 is a magnetic flux command Φ ^* based on the rotational speed ωre of the synchronous motor ^. Is a magnetic field command calculator for calculating a field current command If ^* based on a magnetic flux command Φ ^* and a magnetic flux detection value Φc estimated and calculated by the magnetic flux observer 12. Field Flow If is, to match the field current command If ^*, field current controller for calculating a field voltage command Vf, 16, based on the field voltage command Vf, supplies power to the field circuit The field converter 17 is a current detector that detects a field current, 18 is a switch that switches the field current command If ^* by an external signal (F signal), and 19 is a switch 18 The setting device 20 for giving a field current command when switched to the “1” side inputs the load angle δc estimated by the magnetic flux observer 12 and this δc A comparator that outputs “0” when the absolute value of is smaller than a predetermined set value, and outputs “1” when it is larger (outputs as an F signal), 201 is δc An absolute value calculator for calculating the absolute value of 202, 202 is a hysteresis comparator capable of setting a hysteresis width, and 203 is a δc that outputs an F signal. Δon setting device for setting the level (δon) of δc, 204 for setting the F signal to “0” This is a δoff setting device for setting the level (δoff) of.
[0010]
Next, an outline of the operation of this embodiment will be described. First, the rotational speed ωre of the synchronous motor 1 is detected by the speed / position detector 10. The deviation between the speed detection value ωre and the command value ωre ^* from the speed command generator 2 is added to the speed controller 3, and the torque current command IT ^* corresponding to the deviation is calculated. It is controlled to match. A current control loop is provided inside the speed control loop as shown in FIG. 1, and the armature current and the field current are detected by the armature current detector 8 and the field current detector 17, and the armature current is detected. Are controlled by the armature current controller 5 and the field current controller 15 so as to coincide with the command values of the field current. In order to perform vector control using the MT coordinate, it is necessary to detect the load angle δ and the magnetic flux Φ on the M axis. Therefore, in the magnetic flux observer 12, the estimated magnetic flux Φd in the synchronous machine is determined from the armature current and the armature voltage. , Φq Is used to calculate δc And Φc Is calculated (because it is a value in the controller, δ and Φ are represented with the symbol “c”). Calculated δc Is used in the coordinate converter 4. Also, the calculated magnetic flux Φc And the command value Φ ^* from the magnetic flux command calculator 13 are added to the field command calculator 14, and the field current is controlled according to the field current command If ^* which is the output.
[0011]
2 to 4 show the MT and dq axes and the torque current IT. And field current If Is represented by a vector. Low load (IT , And δ are small), the vector relationship is as shown in FIG. Heavy load (IT , And δ are large), the relationship becomes as shown in FIG. Need to be larger. If the armature leakage inductance and saliency of the synchronous motor are ignored, If And δ is
If = Iφ / cosδ (Equation 1)
It becomes. Here, Iφ corresponds to the excitation current required for the magnetic flux Φ (If And IT Composite current).
[0012]
In order to control the magnetic flux Φ to be constant, it is necessary to make Iφ constant, and it is necessary to control If according to IT. However, while IT is controlled at high speed on the armature side, it is impossible to control If as fast as IT. In order to control If at high speed, a field converter having a capacity several times to several tens times the steady value is required. It is uneconomical to introduce a large-capacity field converter only for the transient response, and the field windings of the motor need to be able to withstand the large capacity. In a normal synchronous motor, the rotor is provided with a damper winding, and the magnetic flux is prevented from changing suddenly until the field current reaches a necessary amount. Therefore, when IT changes extremely greatly, the magnetic flux cannot be maintained with only the damper winding, and δ exceeds 90 degrees , resulting in step-out.
[0013]
FIG. 4 is a vector diagram when δ exceeds 90 degrees. When δ exceeds 90 degrees, the magnetic flux Φ starts to decrease rapidly as Iφ becomes negative. When Φ decreases, the overall torque becomes insufficient, resulting in IT Δ will increase, and δ will continue to increase. This is the mechanism of step-out.
[0014]
FIG. 5 shows δ, If when the load torque changes suddenly. , IT The operation waveforms of are conceptually shown. IT to follow the change in load torque Is responding fast, but If Since δ changes slowly, δ reaches 90 degrees at a stretch. As a result, IT Diverges and step-out (torque loss) occurs.
[0015]
Therefore, If Needs to be increased quickly and δ must be pulled back within 90 degrees. As shown in Equation 1, if The value of is proportional to 1 / cos δ. Is required. Therefore, when δ reaches 90 degrees (or around 90 degrees), the field current command If ^* is switched to a large value, and If Can be increased.
[0016]
As mentioned above, if Since the value of is proportional to 1 / cosδ, if it is switched at δ = 90 degrees, it is better to switch to as large a value as possible. If this size is set to the maximum value that can withstand the field capacity of the field converter or the synchronous machine, δ is pulled back to the stable region at the maximum speed.
[0017]
This switching is performed because only δ is used as a judgment material regardless of the state of various quantities other than δ (detected value of field current or estimated magnetic flux Φc, etc.). Although there are concerns about shocks (eg, overcurrent , vibrations, etc.), they are not a problem at all. When δ is close to 90 degrees, the influence of the field current on the magnetic flux is small, and problems such as large magnetic flux fluctuations or torque fluctuations do not occur. Rather, keeping the long period δ close to 90 degrees (or more than 90 degrees) causes a fluctuation in magnetic flux, a decrease in torque, and the like, which is a problem. If the value to be switched is set to a value that can be supplied by the field converter as described above, If does not become an overcurrent.
[0018]
The embodiment of the present invention shown in FIG. 1 realizes this step-out prevention function. Δc is monitored in the comparator of reference numeral 20 , and the F signal is switched from 0 to 1 at the moment when the set value δon is exceeded. At this time, the absolute value of δc is calculated, and switching is determined based on that value, so that it can be used as it is even during regeneration. Further, in order to prevent the F signal from flapping near δon, the comparator 202 is a hysteresis comparator. The level for returning the F signal to 0 is set by the value of δoff. For the F signal output from the comparator 202, the switch 18 is normally set to the “0” side, and when the F signal is 1, it is switched to “1” to set If ^* to the maximum value that the field converter can flow. Switch. As described above, the setting unit 19 sets the maximum value that can be flowed by the field converter or the field circuit of the electric motor.
[0019]
FIG. 6 shows an operation waveform of each part of the present invention. Due to changes in load torque, IT Suddenly increases and δ reaches 90 degrees at once, but when δon is reached, If ^* switches to If Increase rapidly. As a result, δ is pulled back within 90 degrees and step-out is prevented.
[0020]
Next, a second embodiment will be described with reference to FIG.
[0021]
In FIG. 7, reference numerals 1 to 18 and 20 are the same as those in the embodiment of FIG. 19A is a voltage command setter that sets a voltage command to the field converter when the switch 18 is switched to the “1” side. The operation of each part in the present invention is almost the same as that of the embodiment of FIG. 1, and the switch 18 is switched when the load angle δc exceeds δon. At this time, if the value of the voltage command setter 19A is set large, the applied voltage to the field converter increases, and If can be increased. In the present embodiment, since the field voltage can be directly increased without using the field current controller 15, the field current increases at a higher speed. If the set value of the voltage setting unit 19A is set to the maximum voltage value that can be applied to the field circuit or the maximum voltage value that can be output from the field converter, If can be increased instantaneously. , Step out can be suppressed.
[0022]
Next, a third embodiment will be described with reference to FIG.
[0023]
In FIG. 8, reference numerals 1 , 2, and 4 to 20 are the same as those in the embodiment of FIG. 3A is a speed controller, 31 is a proportional compensator, 32 is an integral compensator, 33 is the same switcher as 18 and 34 is a setter set to zero. Since the operating principle of the present embodiment is the same as that of FIG. 1, the characteristic part 3A will be described.
[0024]
3A is a speed controller basically comprising proportional integral compensation. However, when the F signal which is the output of the comparator 20 is “1”, the switch 33 is switched to the “1” side, and the input of the integral compensator is made zero. As a result, it is possible to prevent the torque current command IT ^* from continuing to increase while δ exceeds δon. Since the increase in IT ^* is only the component of the proportional compensator 31, the effect of pulling δ back within 90 degrees becomes stronger, and faster recovery to the stable region becomes possible.
[0025]
Next, a fourth embodiment will be described with reference to FIG.
[0026]
In the fourth embodiment, the speed controller 3A in FIG. 8 is replaced with a speed controller 3B shown in FIG. The speed controller 3B shown in FIG. 9 is provided with the above-described switch 33 based on the F signal on the output side of the speed controller. Reference numeral 35 is a memory over holding the past torque current command. In FIG. 9, when the F signal is “1”, the input of the integral compensator is made zero, and at the same time, the torque current command IT ^* at that time is continuously maintained. As a result, when the load angle δ exceeds δon, IT ^* is fixed, and there is no element that increases δ. Therefore, δ recovers to the stable region at a higher speed than in the previous embodiment.
[0027]
In each of the above embodiments, instead of the speed / position detector, speed / position estimation means for estimating the speed and position from the current / voltage of the motor winding may be used. Furthermore, instead of estimating the magnetic flux by the magnetic flux observer, the detected value of the magnetic flux detected by the magnetic flux sensor may be used.
[0028]
【The invention's effect】
As described above, according to the present invention, the load angle increases due to a sudden load change, and even when the unstable angle region is reached or is likely to reach the unstable region, the load angle δ is quickly stabilized within 90 degrees. It becomes possible to pull back to the area. As a result, step-out due to overload can be prevented.
[Brief description of the drawings]
FIG. 1 is a block diagram of a synchronous motor variable speed control system showing an embodiment of the present invention.
FIG. 2 is a vector diagram for explaining the operation of the synchronous motor (at light load).
FIG. 3 is a vector diagram for explaining the operation of the synchronous motor (at the time of overload).
FIG. 4 is a vector diagram for explaining the operation of the synchronous motor (at the time of abnormality of δ> 90 °).
FIG. 5 shows operation waveforms at the time of sudden change in load torque in the conventional method.
FIG. 6 shows operation waveforms at the time of sudden change in load torque in the embodiment.
FIG. 7 is a block diagram of a synchronous motor variable speed control system showing a second embodiment of the present invention.
FIG. 8 is a block diagram of a synchronous motor variable speed control system showing a third embodiment of the present invention.
FIG. 9 is a block diagram of a synchronous motor variable speed control system showing a fourth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Winding type synchronous motor, 2 ... Speed command generator, 3 ... Speed controller, 4 ... MT-dq coordinate converter, 5 ... Armature current controller, 6 ... dq-three-phase coordinate converter, 7 ... Electric power Converter, 8 ... armature current detector, 9 ... voltage detector, 10 ... speed / position detector,
DESCRIPTION OF SYMBOLS 11 ... Three-phase-dq coordinate converter, 12 ... Magnetic flux observer, 13 ... Magnetic flux command calculator, 14 ... Field command calculator, 15 ... Field current controller, 16 ... Field converter, 17 ... Field current Detector: 18 ... Switcher, 19 ... Setter, 20 ... Comparator, 201 ... Absolute value calculator, 202 ... Hysteresis comparator, 203 ... δon setter, 204 ... δoff setter.

Claims (6)

Means for detecting or estimating the rotating magnetic pole position of the synchronous motor and means for detecting or estimating the magnetic flux of the synchronous motor, and based on the detected value or estimated value of the magnetic pole position and the magnetic flux position, the armature of the synchronous motor Coordinate conversion of current into torque current component and excitation current component, means for controlling the armature current, means for calculating a magnetic flux command of the synchronous motor, and the detected magnetic flux value or the estimated value as the magnetic flux command value A field command calculator for giving a field current command to the field circuit of the synchronous motor so as to match, and the field current of the synchronous motor matches the field current command. In a synchronous motor control device having a field current controller for controlling a magnetic current,
The control device provides means for giving a rotational speed command to the synchronous motor, means for detecting or estimating the rotational speed of the synchronous motor, the detected rotational speed value or the estimated value, and the deviation of the rotational speed command. An integral compensator, and a speed controller that uses the output of the compensator as a command value of the torque current,
The load angle δ estimated or detected based on the magnetic pole position and the magnetic flux position is compared with a preset set value δMAX, and when the load angle δ exceeds the set value δMAX, the synchronous motor A control apparatus for a synchronous motor , wherein a field current is increased and simultaneously an input of an integral compensator in the speed controller is switched to zero . In the synchronous motor control device according to claim 1,
When the load angle δ exceeds the set value δMAX, the maximum value that can flow the field current command value of the synchronous motor to the field circuit of the synchronous motor, or power to the field circuit A control apparatus for a synchronous motor, wherein the field current is increased by switching to a maximum current value that can be output by a power converter to be supplied. In the synchronous motor control device according to claim 1,
When the load angle δ exceeds the set value δMAX, the field voltage applied to the field circuit of the synchronous motor is the maximum value that can be applied to the field circuit, or the field circuit A control apparatus for a synchronous motor, wherein the field current is increased by switching to a maximum voltage value that can be output by a power converter that supplies power. Means for detecting or estimating the rotating magnetic pole position of the synchronous motor and means for detecting or estimating the magnetic flux of the synchronous motor, and based on the detected value or estimated value of the magnetic pole position and the magnetic flux position, the armature of the synchronous motor Coordinate conversion of current into torque current component and excitation current component, means for controlling the armature current, means for calculating a magnetic flux command of the synchronous motor, and the detected magnetic flux value or the estimated value as the magnetic flux command value A field command calculator for giving a field current command to the field circuit of the synchronous motor so as to match, and the field current of the synchronous motor matches the field current command. In a synchronous motor control device having a field current controller for controlling a magnetic current ,
The control device includes means for giving a rotational speed command for the synchronous motor and means for detecting or estimating the rotational speed of the synchronous motor, and the detected rotational speed value or the estimated value matches the rotational speed command. Equipped with a speed controller to control
The load angle δ estimated or detected by the magnetic pole position and the magnetic flux position is compared with a preset set value δ MAX ,
When the load angle δ exceeds the δMAX, at the same time as increasing the field current of the synchronous motor, the output of the speed controller is set to a value immediately before the load angle δ exceeds the δMAX. A control device for a synchronous motor, which is fixed and maintains the value until the load angle δ falls below δMAX again or falls below another set value different from δMAX. In the synchronous motor control device according to claim 4,
The load angle δ is equal to the set value δ. MAX The maximum value that can be supplied to the field circuit of the synchronous motor, or the maximum value that can be output by the power converter that supplies power to the field circuit. The synchronous motor control device is characterized in that the field current is increased by switching to a current value of. In the synchronous motor control device according to claim 4,
When the load angle δ exceeds the set value δMAX, the field voltage applied to the field circuit of the synchronous motor is the maximum value that can be applied to the field circuit, or the field circuit A control apparatus for a synchronous motor, wherein the field current is increased by switching to a maximum voltage value that can be output by a power converter that supplies power.

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