SU415777A1 - - Google Patents

Description

one

The invention may be used to excite synchronous motors with variable loads on the shaft, for example, the main drives of rolling etans.

Arrangements are known for automatic excitation control (APB) of synchronous motors, made on the sub system of a slave control with excitation, reactive current and voltage controllers.

To increase the use of motor overload capacity and reduce voltage fluctuations in the supply network in the proposed device, the regulators are connected in series when the regulator is operated, the excitation circuit is proportional-integral differential and proportional-voltage regulators. The voltage regulator is closed by an interconnected circuit through a non-linear element with a dead zone and a restricted zone at the bottom.

Additional values of positive feedback to the excitation current and reactive current are attached to the reactive uca controller and the voltage controller, respectively, which increases the speed of the device.

For improved: cost-effective adjustment to the voltage regulator of the output circuit is an additional negative feedback factor for the reactive current of the load node.

To the controller (inactive current of the node. It is supplemented by the last current of a flexible positive connection to the active current, which doesn’t allow the decompression roto) to a shock load.

FIG. 1 shows the structure of the described device; in fig. 2 is a graph of reactive current / p versus voltage Uc at a load node.

The excitation of the synchronous motor 1 is carried out by a thyristor exciter 2. Directly on the input of the thyristor exciter acts proportionally-1 ntralno-differential regulator 3 of the excitation current, to the input of which the proportional-current regulator 4 is reactive. A proportional voltage regulator 5 is connected to the input of the controller 4. In addition, the input of the regulator 4 through the differentiating circuit 6 is affected by a flexible connection to the 1st stator current from the meter 7 active current. ia input of regulator 3 is fed negative feedback 1a over excitation current from) 1: driver 8 excitation current 1i. The doiol is also connected to the input of the regulator 4;

feedback on reactive current from the meter 9 reactive current. The input of the regulator 5 is affected by negative feedback across the voltage at the load node from the measuring device 10 injecting and with positive feedback on the reactive current. Regulator 5 is also covered by negative feedback through two nonlinear elements (diode) 11 and 12. Negative feedback can be applied to the input of controller 5 through nonlinear element 12, but to the reactive current of the load node electrical receivers except synchronous motor. In addition, the device comprises a reactive current meter 13 of the load node, current transformers 14 and 15, and a voltage transformer 16.

Section ab (see Fig. 2) corresponds to the restriction of the output of regulator 5 from below, and section bb to the insensitivity zone of negative feedback covering this regulator. On section V-z, negative feedback encompasses regulator 5. Territory r-d corresponds to the restriction of negative feedback from regulator 4 from above (ceiling excitation current), and the section to restricting the output of this regulator from above.

At a constant voltage of the regulator 4, under the action of negative feedback, the excitation current is maintained at a given constant level in those modes when the regulator 4 is either turned off or is operating in the restricted zone. With a constant output of the regulator 5, the regulator 4 keeps the reactive current of the engine constant.

The feedback of the excitation current is also fed to the input of the regulator 4 so that when the regulator 4 is operated in the linear zone, the resulting feedback of the excitation current is zero. Since the time of the motor is compensated for by the transfer function of the regulator 3, the absence of feedback on the excitation current while the regulator 4 allows the reactive current control circuit to be as fast as the cut-off frequency as the excitation control circuit. For the static regulation of the reactive current, a second static regulator is not required. Astatic regulation is provided by regulator 3.

The voltage of the regulator 5 is limited from below, so that the reactive current is also limited from below. This provides a static overload capacity of the motor at a level determined by the ceiling field current. The set value of reactive current can be negative, i.e. the motor can work with lagging reactive current. To keep even the lagging reactive current at a constant level as the load increases, the device increases the excitation current to the ceiling

value (the voltage of the regulator 4 reaches the upper limit level). However, in order for the dynamic overload capacity to be, but at least not lower than the static one, it is not necessary to work with a large lagging reactive current.

When the regulator 5 is operating, the device tends to keep the voltage at the load node constant. At the same time in the linear zone

the resulting reactive current feedback is zero (just as when regulator 4 is operating, the feedback to the excitation current is zero). The same speed (cut-off frequency) as in the circuits of the excitation current and the reactive current of the engine is provided in the circuit.

The resulting effect of diodes II and 12 provides in the feedback circuit of the regulator 5 of the deadband and the limiter. The voltage regulator is fully open only within the dead band or the span of the spanning linkage, i.e. when the spanning link signal

is changing. Under the same negative feedback, the resulting transfer coefficient of the regulator 5 decreases, the positive feedback on the reactive current becomes weaker than the negative and

ARV system supports

CR & 1P + Kish, 0,

where A / p is the increment of reactive

current; - voltage increment in

load node;

Cr and Ki - coefficients. A constant signal is encompassing, its feedback takes place at an excessively large or excessively small voltage at the load node. At the same time, the device tends to maintain A / 7s 0, and regulator 3 provides astatic regulation.

Due to the non-linear elements 11 and 12, in the normal voltage range, cost-effective regulation is performed, with excessive injection of voltage, the output of the reactive current decreases sharply, and with an excessive decrease in voltage, it increases sharply (boost).

Since the voltage level in the load unit can vary not only due to electrically close electric receivers, but also due to long-distance power consumers or by adjusting the voltage in the power system, the level of the power in the load node does not completely reflect the economical value of the reactive current at each moment of time. Better regulation is provided while maintaining

 + Apci / pc + O

where A / pc is the increment of the reactive current of the load node that powers the engine in question.

To implement this regulation, the negative feedback of the load node from the meter 13 can be fed to the input of the regulator 5 through a nonlinearity in the feedback circuit. In order for the stability margin in the control system not to change, together with the specified link additional positive reactive current connection is applied so that the resulting signal of these feedbacks is proportional to the reactive current of the remaining electrical receivers of the load node.

Thus, the law of regulation is implemented.

 + K ,, (A / Re - A / p) + Ki O, which is equivalent to the previous one

/ Ср ™ Кр - / СрсThe proposed device in various modes (excluding the mode of excitation current limitation at the ceiling level) keeps unchanged either the reactive current or the mains voltage, the changes of which are roughly proportional to the changes of the reactive current or their linear combination. Due to this, the reactive current is maintained independent of the load on the shaft, which significantly reduces the voltage fluctuations in the supply network from the load on the shaft.

The device is made of elements of a universal block system of regulators: operational amplifiers with corresponding input and feedback circuits, a direct current sensor, key phase sensitive active and reactive current sensors, and an alternating alternating current sensor.

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11 p elmet I 3 o b e tein

Claims (4)

1. A device for automatically controlling the excitation of a synchronous motor, made according to a subordinate control system with excitation current, reactive current and voltage regulators, characterized in that, in order to increase the use of motor overload capacity and reduce voltage fluctuations in the supply mains, the regulators connected in series when regulating the excitation current is proportional-integral-differential, and regulators of reactive current and voltage are proportional, In this case, the voltage regulator is closed by a feedback circuit through a non-linear element with a dead zone and a zone of restriction from below. 2. Device but p. 1, characterized in that, in order to increase the speed, additional positive current feedback circuits are connected to the reactive current and voltage regulators excitation and reactive current, respectively. 3. The device according to claim I, characterized in that, in order to increase the efficiency of the regulation, an additional negative feedback circuit is connected to the voltage regulator and to the reactive current of the load node. 4. The device according to claim 1, characterized in that, for the purpose of damping vibrations the rotor under shock load, an additional circuit of flexible positive feedback on the active current is connected to the reactive current regulator.