JPS6259558B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a commutatorless motor driven by a power converter.

Conventionally, there has been a device of this type as shown in FIG. When a commutatorless motor is required to have a large overload capacity, such as when used in a steel mill, it is usually equipped with a compensating field winding, so FIG. 1 shows a case with a compensating field winding. In the figure, 100 is a forward converter that is connected to a three-phase AC power source P1 and converts AC power into DC power, 150 is a smoothing reactor, and 20
0 is an inverter that converts DC power into variable AC power P2, 300 is a commutatorless motor driven by variable AC power P2, and includes an armature winding 310, a main field winding 350, and a compensation field winding. Consists of 360. 320 is a position detector that is directly connected to the rotor shaft of the electric motor and detects the relative position between the rotor and the stator, and 330 is a speed detector. 210 is an inverse converter 2 that performs logical operations on the signal from the position detector 320.
00 is the firing logic circuit that provides the firing signal. 1
10 is a phase control/ignition circuit of the forward conversion device 100;
111 is a current control circuit, 112 is a speed control circuit,
S1 is a speed command signal, and the speed of the motor is controlled by this signal. 351 is an excitation device that excites the main field winding 350; 352 is the excitation device 351;
353 is a current control circuit for the main field winding, and 354 is a current command signal generation circuit for the main field current. 361 is an excitation device that excites the compensation field winding 360; 362 is the excitation device 361;
363 is a current control circuit for the compensation field current. Also, I _a is the armature current,
I _f is the main field current, and I _c is the compensation field current. The main field current I _f is a constant current in a constant torque region, and is decreased in inverse proportion to the speed ratio when a constant output region is required. The control pattern for I _f and I _c is shown in FIG. FIG. 2A shows a control pattern of I _f and I _c for armature current I _a . In the same figure,
I _cp is a fixed portion of the compensation field current, which will be described later. Figure 2B shows the control pattern of the main field current I _f with respect to the speed N, where N _B is the base speed, N _T is the maximum speed, and the range from N _B to N _T is the constant output region (field weakening region). ). This constant power range is usually 2 to 3 times larger for steel mills. This I _f control pattern is based on the main field current command signal generation circuit 3 in FIG.
54.

Next, the operation of the conventional example will be explained. Since the operation of the commutatorless motor shown in FIG. 1 is well known, a detailed explanation will be omitted, but control of the main field current and the compensation field current will be explained here.

First, FIG. 3 shows a vector diagram of a commutatorless motor. FIG. 3A shows the case of electric operation, and FIG. 3B shows the case of regenerative operation. In the figure, I _a is the armature current fundamental wave vector, _{If is the main field current vector, I c is} the compensation field current vector, E _a is the internal electromotive force vector,
V _t is the terminal voltage fundamental wave vector. Also, β _f
is the mechanically set firing advance angle, and u is the commutation overlap angle.

As is well known, commutation in a commutatorless motor is performed by the internal electromotive force of the motor, so the armature current has a certain phase (generally called γ lead angle) compared to the internal electromotive force. ) it is necessary to proceed. Therefore, the compensation field current cancels the armature reaction caused by the armature current and provides commutating magnetic flux. On the other hand, it is necessary to flow a fixed amount (I _cp ) in the compensation field current in order to ensure a commutation margin angle even when the load is light.

In this way, in the conventional device, since the above-mentioned fixed portion of the compensation field current I _cp was required,
When switching the torque polarity, the polarity of I _cp must be reversed, resulting in dead time when switching the torque polarity. This dead time becomes a problem when fast response is required, such as for steel mills.

Also, depending on the size of the commutation overlap angle, the magnetic axis of the armature current deviates from the q-axis, so the armature reaction cannot be completely canceled with only the compensation field current, and the armature current vs. torque characteristic changes. There was a drawback that it was not linear. In addition, there was also a drawback that the motor power factor decreased during overload, particularly in the constant output region (field weakening region), and the overload withstand capability decreased.

In order to eliminate the above-mentioned drawbacks, this invention speeds up the response when switching torque polarity by controlling the main field current in accordance with the armature current, and improves the armature current vs. torque characteristic. make it linear,
In order to keep the motor power factor constant and to achieve this objective, the present invention has two-axis DC excitation windings: an AC armature winding and electrically orthogonal main field windings and compensation field windings. In a control device for a non-commutated motor, comprising a motor, a power converter device that supplies AC power to the AC armature winding, and an excitation device that supplies DC power to the DC excitation winding, the current in the compensation field winding is proportionally controlled by a reference signal generation circuit for compensation field current based on a current command value that depends on the current of the AC armature winding, and
The current in the main field winding is controlled by a reference signal generation circuit for the main field current based on the current command value and the rotational speed of the motor.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 shows a first embodiment. In the figure, 500 is a reference signal generation circuit for the main field current;
00 is a reference signal generation circuit for compensation field current.
The rest is the same as the conventional configuration diagram in FIG.

Here, the reference signals 500 and 600 are predetermined reference current patterns, and can be formed by calculating according to the following equations (1) to (4) in accordance with the speed and armature current. A vector diagram at this time is shown in FIG.

AT _f = AT _g・cosφ ₁ +AT _a・sinφ ₂ ...(1) AT _c = AT _g・sinφ ₁ +AT _a・cosφ ₂ ...(2) I _f =AT _f /N _f ...(3) I _c = AT _c /N _c ... (4) However, the symbols in equations (1) to (4) and the vector diagram in FIG. 5 are as follows.

AT _g : Air gap magnetomotive force AT _a : Armature winding magnetomotive force AT _f : Main field winding magnetomotive force AT _c : Compensation field winding magnetomotive force N _f : Number of turns in main field winding N _c : Compensation field Number of winding turns β _f : Mechanically set ignition advance angle β ₀ : Ignition advance angle relative to internal electromotive force u: Commutation overlap angle E _a : Internal electromotive force V _t : Terminal voltage E _dc : DC voltage R _{: Armature winding resistance _ _ _} Angle with the shaft When calculating the reference signals of I _f and I _c using equations (1) to (4) above, once the motor and circuit constants and operating pattern (speed vs. torque characteristics) are determined, the speed and armature Reference signals of I _f and I _c corresponding to the currents are determined. Here, I _f and I _c are armature current I _a
In order to quickly follow the
A current command signal of 00 (output signal of 112) may be used. Next, a method of calculating the reference signals of _If and _Ic will be explained. First, a control method for eliminating the fixed portion I _cp of the compensation field current will be explained.
As mentioned above, this I _cp was to ensure a commutation margin angle even at light loads, but β _f was increased by an amount corresponding to this angle, and therefore, the main field current was also affected by the armature. I _cp can be eliminated by sharing the compensation of the reaction. Furthermore, by making the reference signals of I _f and I _c satisfy the following relational expression, the armature current versus torque characteristic can be made linear. Here, to make the armature current vs. torque characteristic linear, I _a vs. (E _dc −I _a・R)
becomes a constant characteristic, and I _a vs. motor power factor (cos
_M ) is also a constant characteristic. Here, (E _dc
-I _a ·R _a ) corresponds to the armature current I _a vector component of the internal electromotive force E _a , is called the effective voltage component, and usually depends on the speed. For example, it has a characteristic that it increases with speed up to the base speed, but remains constant in a constant output region. Such reference signals of I _f and I _c can be obtained from equations (1) to (4) if angles φ ₁ and φ ₂ are determined from the following equations (5) to (9).

E _a・cos(β _p −u/2)=V _t・cosψ _M −I _a・R =E _dc −I _a・R ……(5) _M +θ=β _p −u/2 ……(6) cos (β _p −u) − cos β _p = π/3・I _a・X _c /E _a
...(7) (Here, X _c : Commutation reactance) φ ₂ = β _f - u/2 ... (8) φ ₁ + φ ₂ = β _p - u/2 ... (9) Equation (5) , (6), the armature current vs. torque characteristic is made linear. Also, if the armature current and speed are determined under the condition that the motor power factor cos _M is known (set target value), (E _dc -I _a・R) and (
Since _M + θ) is determined, E _a is determined. Next, u is found from equation (7), and therefore φ ₁ and φ ₂ from equations (8) and (9)
is confirmed. Therefore, the reference signals of I _f and I _c can be found from equations (1) to (4). An example of the reference signals of I _f and I _c determined in this manner is shown in FIG. The _{solid line} indicates the case when the base speed (N _B ) is at If, and the maximum speed (N
The dotted line shows the case when _T : field weakening).

In this way, by having the main field current also share in the compensation of the armature reaction caused by the armature current, the fixed portion I _cp of the compensation field current can be eliminated, and the response when switching torque polarity can therefore be made faster. can do. Furthermore, the armature current vs. torque characteristic can be made linear. Also, the armature current versus motor power factor remains constant.

Here, the reference signals of I _f and I _c may be calculated instantaneously by feeding back the armature current and speed signal, or the reference signals may be created in advance using approximate functions.

In addition, the reference signals of I _f and I _c are determined by equations (1) to (4), but since I _c is almost a straight line with respect to I _a , even if it is controlled to be proportional to I _a , Almost the same characteristics can be obtained.

On the other hand, even in the direct compensation method in which the compensation field winding 360 is inserted directly into the DC circuit in the power converter, the same characteristics can be obtained even if the main field current is controlled using the above-mentioned I _f reference signal. can get.

Next, a second embodiment according to the present invention is shown in FIG. In the figure, 510 is a reference signal generation circuit for the main field current, 511 is a DC voltage detector, and 512 is a voltage detector that detects the motor terminal voltage and forms a voltage signal equivalent to the DC voltage. That is, from the vector diagram in Fig. 5, E _dc −I _a・R=K・V _t cosψ _M −I _a・R
(K: proportionality constant) Therefore, even if the motor terminal voltage is detected, a voltage signal substantially equivalent to the effective voltage component detected from the DC voltage can be obtained. In FIG. 7, the case where DC voltage is detected is shown with a solid line, and the case where motor terminal voltage is detected is shown with a dotted line.

Here, the operation of the second embodiment will be explained. In the first embodiment, the fixed portion current I _cp of the compensation field winding is eliminated by having the main field winding also share the compensation of the armature reaction, and the armature current vs. torque characteristic is made linear. The reference signals of I _f and I _c for the purpose of be.

A block diagram of the main field current reference signal generation circuit 510 is shown in FIG. In the figure, 513 is a circuit that forms a function of speed vs. DC voltage (N vs. E _dc '), 514 is an adder that compensates for the resistance drop, and 51
5 is a subtracter that takes the deviation between the output signal of the adder 514 and the DC voltage detection signal (output signal of the detector 511 or 512), and the output signal of this subtracter 515 is used as the reference current command for the main field current. Become. By controlling the main field current using this reference current command, armature reaction is also compensated for.
The DC voltage is also kept constant (the resistance drop is added). That is, the armature current vs. torque characteristic becomes linear, and the motor power factor also becomes constant. especially,
In the constant output region (field weakening region), the effect is large and the overload resistance is improved.

As described above, according to the present invention, by controlling the main field current in accordance with the armature current, the response at the time of torque polarity switching is made faster, and the armature current vs. torque characteristic becomes linear, resulting in excessive Load capacity can be improved.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a conventional configuration example, Figure 2 is a block diagram showing an example of a conventional configuration.
3 and 3 are explanatory diagrams of the operation of a conventional configuration example, FIG. 4 is a block diagram showing an embodiment according to the present invention, FIG. 5 is a vector diagram explaining the operation of the present invention, and FIG. 6 is an I _f 7 is a block diagram showing another embodiment of the _present invention, and FIG. 8 is a block diagram of a reference signal generating circuit used in FIG. 7. In the figure, 300 is a motor, 310 is an armature winding, 350 is a main field winding, 360 is a compensation field winding, 500 and 510 are reference signal generation circuits for the main field winding, and 600 is a compensation field winding. In the winding reference signal generation circuit, 511 is a DC voltage detector, and 512 is a voltage detector that detects the motor terminal voltage and forms a voltage signal equivalent to the DC voltage. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A motor having two-axis DC excitation windings including an AC armature winding and electrically orthogonal main field windings and compensation field windings, which supplies AC power to the AC armature winding. In a control device for a commutatorless motor, which includes a power conversion device for supplying DC power, and an excitation device for supplying DC power to the DC excitation winding, the current in the compensation field winding is approximately proportional to the current in the AC armature winding. At the same time, the current in the main field winding is controlled so that the voltage drop component of the AC armature winding resistance is added to the reference voltage command signal, which increases with speed up to the base speed and remains constant in the constant output region above it. 1. A control device for a commutatorless motor, characterized in that a deviation signal between a voltage command obtained by adding the voltage commands and an actual voltage feedback signal is generated, and control is performed using the deviation signal. 2. Claim 1, characterized in that the voltage command signal and actual voltage feedback signal used to control the current in the main field winding are obtained by multiplying the motor voltage by a signal equivalent to the motor power factor. A control device for a commutatorless motor as described in . 3. When the power conversion device has a forward converter/inverse converter configuration with a DC circuit section, the voltage command signal and actual voltage feedback signal used to control the current in the main field winding are A control device for a commutatorless motor according to claim 1, characterized in that the voltage is set to the voltage of the circuit.