JP3125889B2 - Control device for synchronous motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

 [Object of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous motor control device for driving a synchronous motor using a permanent magnet as a rotating field at a variable speed.

[0002]

2. Description of the Related Art The field of a rotating field type synchronous motor includes an electromagnet system using a field winding and a permanent magnet system using no field winding. In the electromagnet method, the power loss caused by the field winding causes the efficiency to decrease, and the Joule heat is generated from the field winding, the temperature rises, the rotor thermally expands, the rotational balance is lost, and abnormal vibration occurs. There is a problem. On the other hand, since the permanent magnet method has no power loss, the efficiency is improved accordingly, but there is a great advantage that heat is not generated by the field winding and the rotation balance is not lost due to thermal expansion.

[0003] Conventional permanent magnets have the property that they do not return to the original magnetic flux density when a large demagnetizing field is applied, and their application has been refrained from large-capacity synchronous machines. However, in recent years, the technology for manufacturing permanent magnets has been advanced, and permanent magnets containing rare earths such as samarium, neodymium, and cobalt as main components have come to practical use.

[0004] Since the relative permeability of the rare earth permanent magnet is nearly 1 and close to the permeability of air, it has a stable characteristic that is hardly affected by an external magnetic flux, and has become a motive to be applied to a large capacity machine. On the other hand, there is an armature reaction as a characteristic of the synchronous motor, and the magnetic flux due to the armature current acts to increase or decrease the magnetic flux of the field poles according to the power factor.

A power converter using a thyristor is generally used as a control power supply for driving a large-capacity synchronous motor at a variable speed. In this case, the power converter is usually operated at a leading power factor due to the conditions of a commutation mechanism. In the case of a leading power factor, the force acts in a direction to reduce the magnetic flux of the field due to the armature reaction.

Therefore, when the load increases and the armature current _Ia increases, the air gap flux decreases, and the terminal voltage V ₁ drops as shown in FIG. Since this corresponds to impedance drop due to current, a constant called synchronous reactance is defined and used for analyzing the characteristics of a synchronous motor. This armature reaction can be compensated by increasing the exciting current flowing through the field winding and increasing the field flux in the electromagnet type synchronous motor. However, this cannot be done with a motor using permanent magnets.
Decrease in the terminal voltage V ₁ is inevitable as shown in (A). The terminal voltage V _n at the rated output is therefore the fact that the voltage V _n at the rated current I _n of FIG. 4 (A), the power converter for driving the motor, when the no-load voltage V ₀ and the rated current I Requires the ability to output _n . Therefore, for the required output from the motor rating, the capacity of the power converter is V ₀ /
V _n times (which greater than 1 by the armature reaction) is needed and becomes larger device.

FIG. 4B shows a known vector diagram of the synchronous motor in a leading power factor operation state. The terminal voltages V ₁ is shown to be reduced by the synchronous reactance voltage drop V _x from FIG. Note that Ф ₀ is the magnetic flux of the field pole, and Ф _0
a is _a magnetic flux due to the armature current Ia. It can be seen that the air gap magnetic flux, that is, the effective magnetic flux Φ, is the vector sum of Ф ₀ and Ф _a and is reduced. The angle φ of V ₁ and I _a is the power factor angle, the angle δ of the internal induced voltage E ₀ and V ₁ is the internal phase angle.

Further, in order to make the air gap magnetic flux equivalent to the rated output in a state where the magnetic flux is demagnetized due to the armature reaction, the field magnetic flux Ф ₀ by the permanent magnet needs to be increased in advance. However, in the case of a permanent magnet, the thickness of the magnet is increased, the weight and dimensions are increased, and the magnet is expensive.

[0009]

As described above, there is a problem in that the capacity of a power converter for driving a synchronous motor using a permanent magnet as a rotating field becomes larger than necessary and becomes expensive.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems by compensating for a new armature reaction and controlling a compact and economical synchronous motor without unnecessarily increasing the capacity of a power converter. It is to provide a device. [Configuration of the Invention]

[0011]

To achieve the above object, according to an aspect of the present invention, there is provided an apparatus comprising an inverter for controlling the armature current of the synchronous motor using a permanent magnet to the rotating magnetic field, electric machine synchronous motor The slave voltage detection value and voltage command value
Means for controlling the armature current phase so that the voltage deviation becomes zero in accordance with the deviation of .

[0012]

When the armature current changes in response to the change in the load torque, the reactance voltage due to the armature reaction changes and the voltage of the synchronous motor changes. At this time, the phase of the armature current is controlled by the means according to the voltage change to suppress the voltage change due to the armature reaction.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a main configuration of a synchronous motor control device according to the present invention. In Figure 1, inverter - motor 1 is a three-phase DC voltage V _d which is smoothed by capacitor 1A AC voltage V
_This is a voltage-type inverter which drives the synchronous motor 2 of the permanent magnet type by converting it into ₁ and is composed of a self-extinguishing type switch element such as IGBT or GTO. The current control unit 5 has a current reference I _a ^*
And so that the deviation value by comparing the detected motor current I _a by the current detector 4 becomes zero inverter - controlling the motor 1.

[0014] The position detector 3 is rotation angle is coupled to the rotation shaft of the synchronous motor 2 (i.e., the position of the field pole) detecting the theta _r. Differentiator 6 outputs an angular velocity signal omega _a differentiates an angle signal theta _a (t) of time, the function generator 7 in accordance with the omega _a sin omega
to generate a unit sine wave of _a t. The multiplier 8 multiplies the current command I _m and the unit sine wave sin .omega _a t given separately I _m sin omega _a give t, the current reference so I _a ^* And

The current detector 4, the current controller 5, the function generator 7, and the multiplier 8 are each provided in three sets, and each function generator generates a unit sine wave having a phase difference of 120 ° to generate a three-phase current. Control.

The voltage compensation controller 10 comprises a PID controller and the like.
Voltage command V given separately₁ ^* And voltage detector 9
Terminal voltage V of motor 2 output₁Are compared and
The compensation signal θ, and the adder 11 outputs θ_rAnd add
Compensated angle signal θ_a(t) is obtained.

In the embodiment having the above configuration, the current command _Im
When given, the armature current of a magnitude corresponding to I _m I _a
There flows as sinusoidal current synchronized with the rotation angle theta _r of the synchronous motor 2 rotor, the rotor rotates to generate a predetermined torque. When the motor torque and the load torque is in a state rotating at a constant in equilibrium speed is established internal induced voltage E ₀ of the armature, the terminal voltage V ₁ is established in accordance with the reactance voltage V _x by the armature current I _a. This detection voltage V ₁ and voltage command V ₁ ^* Compensation signal theta is output from the voltage compensator 10 reactive current phase is controlled in the armature current I _a as a voltage deviation value is added to the rotation angle theta _r becomes zero is changed according to the deviation value.

In this case, the voltage command V ₁ ^* Is set to a value equal to the terminal voltage at the time of no load (that is, the internal induced voltage E ₀ ), the compensation signal θ becomes the V of the armature current _Ia .
Compensation control is performed so that the delay phase φ with respect to ₁ maintains a value of １ ／ of the internal phase difference angle δ. This state is shown in the vector diagram of FIG. Load size changes and the magnitude of the terminal voltage V ₁ of the changes to the current I _a of the magnitude varies reactance voltage V _x is changed. This change causes V ₁ and V
₁ ^* Deviation when the deviation occurs the phase of the compensation signal θ is controlled current I _a in the direction of reduction is controlled between. Thus, the phase of the current I _a is 1/2 of the delay phase of internal phase angle δ with respect to the terminal voltage V _1.

I _a − in the case where the compensation control is performed as described above.
The V ₁ characteristic shown by the characteristic c ₁ in FIG. 3 (A). In this case, the voltage command V ₁ ^* Is set to V _n . The characteristic c ₂ shown in the figure without voltage compensation control, the phase of the armature current I _a, but merely shows the characteristics of the synchronous motor in the case of fixed to a certain phase lag. FIG. 2 shows a second embodiment according to the present invention.

[0020] This example, inverter - motor 1 is a current type inverter for converting the direct current I _d which is smoothed by the reactor 1B to an alternating current three-phase - a motor. Further, a phase detector 12 for detecting the phase θ ₁ of the terminal voltage V ₁ is provided instead of the position detector 3. In this case, the phase θ _{1 of} V ₁ fluctuates under the influence of the reactance voltage V _x , but the same effect can be obtained because the compensation signal θ compensates for the fluctuation. In addition,
The phase detector 12 can also be configured to compensate for a phase variation due to a reactance voltage.

[0021]

According to the present invention, when a synchronous motor using a permanent magnet as a rotating field is driven at a variable speed by a power converter,
Prevents the terminal voltage from dropping due to the armature reaction (demagnetization effect), without increasing the voltage of the power converter more than necessary.
It is possible to provide a synchronous motor control device having a capacity corresponding to the motor rating and having improved economic efficiency.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment according to the present invention.

FIG. 2 is a configuration diagram of a second embodiment according to the present invention.

FIG. 3 is a characteristic diagram and a vector diagram for explaining the operation of the embodiment.

FIG. 4 is a characteristic diagram and a vector diagram for explaining a problem of the conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Inverter 2 ... Synchronous motor 5 ... Current control part 6 ... Differentiator 7 ... Function generator 8 ... Multiplier 9 ... Voltage detector 10 ... Voltage compensation control part 11 ... Adder 12 ... Phase detection part

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-55-111688 (JP, A) JP-A-49-51520 (JP, A) JP-A-53-30717 (JP, A) 92595 (JP, A) JP-A-1-136597 (JP, A) JP-A-62-217889 (JP, A) JP-A-2-269491 (JP, A) JP-A-4-117198 (JP, A) JP-A-50-114524 (JP, A) JP-A-52-97113 (JP, A) JP-A-63-107484 (JP, A) JP-A-60-1022891 (JP, A) (JP, U) JP-B-59-1077 (JP, B2) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H02P 5/41 303

Claims (1)

(57) [Claims] 1. An apparatus comprising an inverter for controlling an armature current of a synchronous motor using a permanent magnet as a rotating field, comprising: an inverter for detecting an armature voltage of the synchronous motor and a voltage command value;
A control device for a synchronous motor, comprising means for controlling an armature current phase so that a voltage deviation becomes zero according to the difference .