SU1515326A1 - Method of controlling double-supplied motor - Google Patents

Abstract

The invention relates to electrical engineering. The aim of the invention is to simplify the implementation of the dual power motor control method. The method consists in that two windings are supplied separately to the windings 2.3 of the motor 1 by two inverters using the frequency difference setting unit 20, setting the required value of the power supply frequency difference is proportional to the required rotational speed of the motor 1 and the electric reduction ratio . Using frequency controllers 8.9, the current frequencies of the supply voltages are determined, in block 18, the difference between these frequencies is compared, compared to the required frequency, and the frequency of the first supply voltage is changed with the help of a controlled generator 6 to the value obtained the difference between the frequencies of the supply voltage will not be equal to the required one. Using the block 10, the required load angle is set, the actual value is measured by the winding 16 and the load angle sensor 13, and the indicated parameters are compared in magnitude and sign. If the signs of the required and actual load angles coincide, then using a controlled generator 7, the frequency of the second input voltage is increased proportionally to the error, and if the indicated signs are opposite, then the frequency of the second voltage decreases proportionally to the error angle of the load will not be less than the maximum allowable value. In accordance with the method, all increments of the electromagnetic moment are provided by varying the frequency of the supply voltages, not the amplitudes. As a result, it is possible to exclude from the structure of the device the nodes and blocks associated with the regulation of the amplitude of the supply voltages. 3 il.

Description

ate

SP

with to

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frequency, set the desired value of the difference between the frequencies of the supply voltage is proportional to the desired rotational frequency of the rotor of the engine 1 and the coefficient of electrical reduction. Using frequency controllers 8.9, the current frequencies of the supply voltages are determined, in block 18, the difference between these frequencies is compared, compared to the required frequency, and the frequency of the first supply voltage is changed with the help of a controlled generator 6 to the value obtained the difference between the frequencies of the supply voltage will not be equal to the required one. With the help of block 10, the required load angle is set, the actual value is measured by the winding 16 and the load angle sensor 13, and the parameters are compared in magnitude and

sign. If the signs of the required and actual load angles coincide, then using a controlled generator 7 increases the frequency of the second input voltage in proportion to the error, and if the indicated signs are opposite, then the frequency of the second voltage decreases in proportion to the error of the load angles will not be less than the maximum permissible value. In accordance with the method, all increments of the electromagnetic moment are provided by varying the frequency of the power supply zheny rather than amplitude. As a result, it is possible to exclude from the structure of the device the nodes and blocks associated with the regulation of the amplitude of the supply voltages. 3 il.

The invention relates to electrical engineering and can be used, in particular, in the creation of low-speed tracking AC systems with a dual-feed executive motor.

The aim of the invention is to simplify the implementation of the dual power motor control method.

Fig. 1 shows an example of a functional circuit of an electric drive, which is analyzing a dual-feed motor control method, Figures 2 and 3 are vector diagrams illustrating an algorithm for choosing the direction of change in the frequency of the supply voltage depending on the signs of the required load angle and mismatch over the load angle. .

The electric drive that implements the dual-power motor control method comprises a motor 1 (FIG. 1) with two multi-phase (in this case three-phase) windings 2 and 3, which are connected respectively to the outputs of the first 4 and second 5 inverters. The outputs of the frequency control of the first and second inverters 4 and 5 are connected respectively to the outputs of the first and second controlled oscillators 6 and 7, to the inputs of which are connected respectively to the outputs of the first and second frequency controllers 8 and 9. The output of the load angle setting unit 10 is connected to the first input of the second comparison unit 11 and the first input of the switch 12 with a variable sign, the output of which is connected to the input of the second frequency regulator 9. To the second input of the second comparison unit 11, the code of the load angle sensor 13, containing the phase detector 14, the output of which is the output of said sensor 13, and the adder 15, the output of which is connected to the first input of the phase selector 14, is connected to the first input of the adder 15 is connected to the output signal windings 16, and to the second inputs of the adder 15 and phase detector 14, the output of the current sensor 17 included in one of the phases of the second winding 3 of the dual-feed 1 motor. The outputs of the first and second frequency controllers 8 and 9 are additionally connected respectively to the first and second inputs of the frequency difference calculator 18, the output of which is connected to the first input of the first comparison unit 19, the output of which is connected to the input of the first frequency regulator 8, and the second input - the output of block 20 sets the frequency difference. To the input of the frequency difference setting unit 20, the output of the rotation speed setting unit 21 is connected.

All units of the electric drive are typical or executed according to known schemes. Inverters 4 and 3 are conventional bridge inverters (for example, transistor) with corresponding control circuits. Upraap

Generators 6 and 7 are voltage-frequency or code-frequency converters. Blocks 11 and 19 of the comparison and calculator 18 of the difference in frequency in the analog version can be made in the form of adders on operational amplifiers (more precisely, in the form of calculators). As a speed setting unit 21, there is usually a control device of a higher control level (for example, a position controller based on a control computer). The load angle setting unit 10 may be implemented in the form of a resistor voltage divider supplied with a voltage of one or another polarity depending on what sign the required load angle should be. The frequency difference setting unit 20 in analog form is a conventional large-scale amplifier on an operational amplifier with a power factor. transfer volume equal to coefficient

electrical reduction. Switch 12 with a variable sign in the analog version can be an analogue switch that commutes

According to expression (1), in order to provide the required rotational speed of the rotor Lp it is necessary to set the required difference in the frequencies of the supply voltages U), and cuj, proportional to the required rotational frequency of the rotor and the input signal to the output of the direct electrical reduction

but either via an inverter (for example, on an operational amplifier), depending on the combination of the signs of the error signal on the angle of the load and the required angle of the load, for which a logic circuit must perform logic control Equivalence on the control input of the analog key. Frequency controllers 8 and 9 are successive correction devices and are performed, for example, on operational amplifiers with corrective chains, the parameters of which are selected according to known methods of automatic control theory. The sensor 17 current in the simplest case - a resistor with low resistance, I

The essence of the dual power motor control method is as follows.

Powering the first and second motor windings of dual power from separate sources (inverters) with multi-phase AC voltages. In a dual-feed motor based on an induction motor with a phase-rotor, the first winding can be considered as the stator winding, and the second 35

40

45

50

55

the values of the frequencies i) and uJ do not matter, since only their difference is important. The control system has a circuit to maintain (stabilize) the frequency difference between the supply voltages.

Wo (c) W, (t) - u), (t), (2)

where is the frequency difference between the feed

stress

In the engine control system, the dual supply frequency of the second supply voltage is set (may vary), and the frequency from the first supply voltage is automatically selected in accordance with the expression derived from (1):

UJ, (t) KpU) p (t) + oJ.j (t), (3)

where Kp Wp is actually the required difference in the frequencies of the supply voltages.

Condition (3) is fulfilled in all modes of operation of a dual-feed motor using a special frequency control loop. To do this, measure the current frequencies s, the first and the second supply voltage, and calculate their current difference du) by the formula

rotor winding. U. inductor motor bodies of dual power, both windings are located on the stator.

The forced component of the rotational speed of the rotor of the dual-feed motor is defined by the following expression:

Ujp (t)

s, c) (t) K „

(one)

Where

u) p

the rotational frequency poTopaj CA), and the angular frequency, respectively, of the first and third supply voltages; Cr-electric coefficient

reductions (for a dual-feed motor based on a phase-rotor asynchronous motor, is equal to the number of pole pairs, and for a dual-feed inductor motor, to the number of rotor teeth).

According to expression (1), in order to provide the required rotor rotation speed Lp, it is necessary to specify the required frequency difference of the supply voltage U), and cuj, which is proportional to the required rotation frequency of the rotor and the electric reduction factor Kp, and

five

0

five

0

five

the values of the frequencies i) and uJ do not matter, since only their difference is important. The control system has a circuit to maintain (stabilize) the frequency difference between the supply voltages.

Wo (c) W, (t) - u), (t), (2)

where is the frequency difference between the feed

stress

In the engine control system, the dual supply frequency of the second supply voltage is set (may vary), and the frequency from the first supply voltage is automatically selected in accordance with the expression derived from (1):

UJ, (t) KpU) p (t) + oJ.j (t), (3)

where Kp Wp is actually the required difference in the frequencies of the supply voltages.

Condition (3) is fulfilled in all modes of operation of a dual-feed motor using a special frequency difference control loop. To do this, measure the current frequencies s, the first and the second supply voltage, and calculate their current difference du) by the formula

/ 3w (t) uJ, (t) - cJjCt),

.-

compare the current frequency difference with the required one, equal to Kplp, and provide the error signal for the frequency difference to the frequency regulator of the first supply voltage. As a result, the required frequency difference is provided by varying the frequency of the first supply voltage. The magnitude and direction of change in the frequency iW of the first supply voltage is automatically determined by the system itself, as is the case in all closed automatic control systems using the principle of deviation operation, i.e. with negative feedback for an adjustable parameter. Consequently, at any frequency oo-g of the second supply voltage, the frequency difference will be equal to the required one, and therefore the rotational speed of the rotor will be equal to the required one.

In steady-state mode with a constant rotor rotation frequency and constant load torque on the motor shaft, the load angle is also constant since the electromagnetic torque of the motor is equal to the load torque. When the speed reference changes (when changing to the new rotor speed) or when the load torque changes on the shaft, an imbalance occurs between the electromagnetic torque and the load torque.

A dual-feed motor, like any synchronous machine, has an internal circuit for controlling the electromagnetic moment, under the action of which the angle to the loads begins to change so that eventually the electromagnetic moment becomes equal to the load moment. The presence of this circuit is due to the design of the dual-feed motor itself. If the system did not have a forced external control of the load angle, then the load angle could be beyond the limits of + 90 ° in some modes, the engine would fall out of synchronicity and become uncontrollable. Therefore, in the engine management system there is a closed loop for adjusting the load angle (external loop).

To forcefully adjust the load angle, set the required load angle value and compare it with the measured actual value. Angle mismatch signal

ten

15

5 20

l25 30 35

40 45 jq

a second inverter frequency regulator is supplied to the frequency controller, and the second supply voltage frequency Wj is measured so that ultimately the load angle mismatch is minimal (ideally equal to zero).

The required amount of change in the frequency of the second supply voltage is determined by the system automatically, as is the case in all automatic control systems built using the principle of control based on the deviation of the controlled parameter (in this case, the load angle). It is only necessary that the feedback be always negative in an adjustable parameter.

Two modes of operation are possible for a dual-feed motor: when the load torque on the shaft is braking and the electromagnetic torque of the motor is rotating and when the load torque on the shaft is rotating, and the electromagnetic torque of the motor is braking. In the first case, the load angle in the steady state is negative, therefore the required load angle is set negative, and in the second case, the load angle is positive and the required load angle must be set positive. Both cases are illustrated by the vector diagrams in Fig. 2 (load braking torque) and Fig. 3 (load torque). The charts show:

and - the generalized vector of the feeding stresses; S is the axis associated with the stator, from which all angles are measured) RP is the specified position of the rotor axis corresponding to the required load angle; R and. R is the possible positions of the rotor axis when it deviates from the given position (actual load angle from the required).

The load angle is defined as the angle between the rotor axis and the generalized vector of the supply voltage. If ACCEPT for simplicity, the magnitude of the coefficient of electrical reduction

Cr 1

then the load angle is expressed as:

 P- ,,

where f is the load angle

/ p - the angle of rotation of the rotor; rotation angle of generalized

supply voltage vectors; all angles are measured with respect to a single S axis associated with the stator.

The load angle mismatch is calculated using the following formula:

uJ cf, - s, (6)

where u (f is the angle mismatch nppy3KHj

 - set (required) angle

loads

cf is the actual load angle.

The concept of a generalized supply vector for a dual-feed motor has the following meaning. Since there are two windings fed from separate sources, there are in fact also two supply voltage vectors. However, they can be conditionally replaced with one generalized vector rotating in space with a difference velocity according to expression (2). The angle of rotation of the generalized vector of supply voltages will then be expressed as follows:

1 / n (O L0, (t) - U) 4 (t) t, (7)

where t is the current time.

The physical justification for adjusting the load angle by varying the frequencies of the supply voltages is as follows.

Let, for example, the braking torque of the load acts on the rotor of the dual-feed motor (Fig. 2). Then the rotor of the engine (its axis) will lag behind the generalized vector of supply voltages. This means that the load angle in the steady state is negative. according to expression (5). The position of the rotor axis corresponding to this mode is denoted by R.

 Let us assume that the load moment slightly increased and the rotor axis took up the position R. Then the mismatch calculated according to expression (6) over the load angle ls 0.

To reduce the misalignment of the load angle, it is necessary to increase the electromagnetic moment of the engine so that it becomes equal to the changed / increased load moment,

ten

15

DO 45

: external adjustment account. If the frequencies of the supply voltages are reduced, then the inductive resistances of the windings will proportionally decrease, and at constant amplitudes of the supply voltages, the currents will change inversely (i.e., will increase), which will lead to an increase in the electromagnetic moment. The load angle will begin to decrease until the mismatch over the load angle is minimized (ideally zero).

At decreasing the moment of load, the axis of the rotor will take the position R. The mismatch on the angle of the load in this case will be / zs / 0.

To reduce misalignment, it is also necessary to reduce the electromagnetic torque of the engine. For this, the frequencies of the supply voltages should be increased, respectively, the currents in the windings and the electromagnetic moment are reduced. The actual load angle remains equal (or close) to that required.

Fig. 3 shows a vector diagram for the case of a torque load, directed along the rotation of the rotor. In this case, the angular position of the rotor is ahead of the angular position of the generalized vector of the supply voltage, therefore, according to (5), the load angle in the steady-state 35 m mode (and the required load angle) will be positive. With an increase in the load moment, the rotor axis will take the position R and the unpowered coordination of the load angle according to (6).

20

25

To reduce the angle error of the load, it is necessary to increase the electromagnetic torque of the engine. Therefore, it is necessary to reduce the frequencies of the supply voltages, which will lead to an increase in the currents in the windings and an increase in the electromagnetic moment.

If the load moment decreases, then the rotor axis will take the position R, and the misalignment according to the load angle according to (6).

To reduce the angle error of the load, it is necessary to reduce the electromagnetic torque of the engine. Therefore, it is necessary to increase the frequencies of the supply voltages, which will lead to a decrease in the currents in the windings and a decrease in the electromagnetic moment.

Thus, if the mismatch signs with respect to the load angle and the required load angle coincide, then in order to stabilize the load angle, the frequency of the second supply voltage should be increased, and if the signs are opposite, decrease.

When the frequency of the second supply voltage changes, the frequency of the first supply voltage also changes according to expression (3), which is provided by the control loop for the difference in frequency of the supply voltages.

Therefore, the difference in the frequencies of the feeds | The desired rotational frequency of the rotations remains unchanged, the non-shifter, which is converted by the unit 20 and the rotor speed remains the target.

In accordance with the method, all the increment of the electromagnetic moment needed to restore the balance from the moment of loading is provided not by changing the angle of the load or the amplitude of the voltage, but by changing the frequencies of the supply voltages. Inverters with only adjustable output voltage frequencies are always simpler than inverters with additional amplitude control. The constancy of the amplitude of the output voltage of the inverters allows them to be fully utilized for voltage in all modes of operation, which reduces the losses on stds5vzh elements and increases the efficiency of inverters.,

The electric drive that implements the dual-feed motor control method works as follows.

The first 2 and second 3 windings of the dual-power motor 1 are powered by multi-phase (in this case three-phase) power supply, respectively, from the first 4 and second 5 inverters. The frequency of the inverter 4 is set using the first controlled generator 6, and the frequency of the second inverter 5 using the second controlled generator 7. The frequency of the output pulses of the first 6 and second 7 controlled generators is adjusted according to the signals received from outputs according to | the first 8 and second 9 frequency controllers. The first 6 and second 7 controlled oscillators are analog-to-frequency or code-to-frequency converters (depending on whether the analog or digital control system). Frequency controllers 8 and 9 are sequential.

corrective devices that implement any of the control laws (proportional, proportional-integral, proportional-integral-differential, etc.) determined from the condition of ensuring stability and accuracy of regulation according to the known methods of the theory of automatic control. The rotational speed setting unit 21, which can be, for example, the position controller of the tracking system, generates a signal corresponding to

nor the difference between the frequencies and the required difference between the frequencies of the supply voltages (the conversion reduces to multiplying the input signal by a scale factor equal to the electrical reduction coefficient Kp). Using the first comparison unit 19, the difference in frequency difference is determined, for which the required difference in supply frequency is subtracted from the required frequency difference of the supply voltage, determined by the frequency difference calculator 18, which performs the operation of subtracting the signal corresponding to the frequency of the second supply voltage from the signal corresponding to the frequency of the first supply voltage. The error signal on the frequency difference is fed to the input of the first frequency regulator 9 and, thus, a closed loop is obtained to control the frequency difference of the power supply voltage with negative feedback. The feedback sensor, which measures the current (actual) frequency difference, is the frequency difference calculator 18. This control loop provides a change in the frequency of the first supply voltage (frequency of the primary voltage of the first inverter A) so that at any frequency of the supply voltage, which is given by the signal from the output of the second frequency regulator 9, the current difference in the frequency of the supply voltages is always (or very close) to the desired difference, therefore, the rotor speed will be equal (or very close) to the desired rotation frequency.

Using the setpoint 10 load angle, the working angle of the load is set, which must be maintained.

1315

motor control system. The load sensor 13 measures the actual load angle of the dual-feed motor using, for example, signals received from the signal winding 16 and the current sensor 17.

Other specific embodiments of the angle sensor 13 are possible. The required and actual load angles are compared using the second comparator block 11, at the output of which a mismatch signal is generated from the load angle. The switch 12 with a variable sign of the error signal on the angle of the load is fed to the input of the second regulator of the 9th frequency. Thus, a closed loop controlling the angle of the load is obtained affecting the frequency of the second inverter 5 (the frequency of the second supply voltage). This circuit has a stabilizing effect only when feedback on the load angle is negative. The sign and magnitude of the load angle depends on both the electromagnetic torque of the motor (which is determined by the frequencies of the supply voltages in this case) and the load moment on the shaft. When the sign of the load moment changes, the electromagnetic moment of the engine also changes the sign under the action of the internal control circuit of the torque inherent in the dual-feed motor, as in any synchronous machine. In this case, the sign of the feedback on the load angle also changes. In the electric drive under consideration, there is a forced change in the sign of feedback on the angle of load 1, depending on which sign of the angle of load the engine operates. The sign of the required load angle is set by the load angle setting unit 10 depending on whether the dual power motor is supposed to operate with a rotating or with a braking torque of the load. To switch the sign of the feedback, a switch 12 with a variable sign serves to transmit the error signal through the angle of load to the input of the second frequency regulator 9 with one sign or another. The logic circuitry at the input of the switch 12 with a variable sign determines the combination of mismatch signs on the angle of the power 326

Rules and the required load angle: if the signs coincide, then the input signal of the second frequency regulator Y transmits the error signal at the load angle with a positive sign (and the frequency of the output voltage of the second inverter 5 increases) if signs. opposite, the error signal in the load angle is transmitted with the I negative sign (and the frequency of the output voltage of the second inverter 5 decreases).

When the actual jiarpy3KH deviation deviates from that required in the electric drive control system, two automatic control processes will occur simultaneously: the process of stabilizing the load angle (due to

0 changes in the second supply voltage) and the process of stabilizing the difference in the frequencies of the supply voltages (by changing the frequency of the first supply voltage). Regulatory processes

5 is terminated after the load angle mismatch becomes minimal (ideally equal to zero). Both adjustment processes proceed automatically due to the very principle of regulation of deviation with negative feedback used in this case. Dependencies of the frequency difference of the supply voltage on the frequency of the first supply voltage and the angle of the load on the frequency

- the second supply voltage is nonlinear. However, these non-linearities are within the respective contours of the regu lation and are covered by negative

Q feedbacks, and in that case, as is known from the theory of automatic control, these nonlinearities have practically no effect on the quality of the regulation.

Claims (1)

Thus, in accordance with the proposed dual-power motor control method, there is no need to carry out power sources (inverters) with adjustable output voltage gamma, which, in comparison with the known solution, determines the implementation simplification, increase of cost-effectiveness and reliability of the control system. Invention Formula A dual-feed motor control method with two multi-phase windings in which said windings are connected respectively to five the first and second multi-phase AC supply voltages, set the required frequency difference of the supply voltages in proportion to the required rotor speed and coefficient of electrical reduction, measure the current frequency of the first and second supply voltages, subtract the current frequency of the second supply nar - , from the current value of the frequency of the first supply voltage, and compare the resulting difference with the required difference in the frequency of the supply voltage in proportion to the error they change the frequency of the first supply voltage to the value at which the current difference value frequency of the supply voltage will be equal to the required difference of the supply voltage, thereby providing the required rotor speed of the engine, set the required load angle and the maximum permissible error ratio for the load angle, 20 sriе.2 the actual load angle is drawn, the actual load angle is subtracted from the required load angle, and the resulting error signal is used to adjust the load angle, characterized in that, in order to simplify the implementation, the signs of the required load angle and error mismatch are determined by the load angle, load angle with the sign of the required load angle and, if the indicated signs match, increase for the load angle, the frequency of the second supply voltage, and if indicated, the opposite signs, reduce in proportion to the load angle mismatch the frequency of the second power supply until the load angle mismatch becomes less than the maximum acceptable load mismatch magnitude . ./ srig.Z