SU681528A1 - D-c drive - Google Patents

Description

The invention relates to adjustable DC valve actuators and can be used in electric drives with non-reversible valve converters operating with intermittent currents, as well as in electric drives with reversible converter currents of equalizing currents.

DC electric drives are known that contain a valve converter without equalizing currents with so-called adaptive Topaf / ui current regulators, in which the current regulator is tuned depending on the operating mode of the converter. This adjustment is necessary to provide high quality control of the current and speed of the motor in continuous and intermittent current modes of the converter and is carried out relay (jump) depending on the magnitude of the motor current so that in the mode of intermittent currents, at the moment of a dead time, the regulator current is an integral (I) link, and in continuous current mode it is proportional-integral (PI)

link with transfer function

(-one)

E (j - active

resistance

where gI is the inductance of the engine's korotnaya circuit in total with the internal

o equivalent converter parameters in continuous current mode;

transfer coefficient

5 valve converter;

constant time of the filter installed at the system input

0 ульsulphase-phase control (SIFU) of the converter for providing noise immunity and operability (if the control discreteness is taken into account) of the valve converter. (Hereinafter, all variables and parameters, except constant time, are considered in relative units, the nominal values of the corresponding variables are taken as base values) 1. When the converter converter is intermittent, this adaptive controller operates in the pulse-width modulated switching mode It is essentially a self-adjusting corrective element with correction pagmeters as a function of current with a possible delay in self-tuning for a period of discreteness of the converter. In addition to the delay in self-tuning, electric drives with such regulators have other advantages: low immunity due to the presence of discrete elements in the control system with a very low response threshold, difficulty in setting extremely high bandwidth requirements for current meters and regulators. Therefore, it is very promising to use electric wires with a different class of self-adjusting current regulators — electric drives in which the adjustment of the regulator parameters is performed not as a function of current, but as a control signal, and not discretely, but smoothly. A close technical solution to the invention is an electric drive in which a valve converter without equalizing currents is used, which feeds the main circuit of a DC motor, a speed regulator whose input is connected to the output with a speed sensor proportional to the current regulator, in the feedback circuit of which a nonlinear element is installed, one input of the current regulator connected to the output of the speed regulator, the second input connected to the current sensor, and the output of the proportional current regulator connected with the input of the valve converter. In such an electric water, a nonlinear element is applied to linearize the relationship between the TOKOiri of the valve transformer body and the control voltage. The characteristic of the non-linear element is selected in accordance with the characteristic of the converter 2. It is known that in the discontinuous current mode, when the current is equal to zero during certain time intervals, the equivalent internal resistance of the valve increases and is a function of the control voltage at 84 SIFU and back EMF load. (A valve converter with a load circuit can be represented as an equivalent generator with a constant transmission coefficient K operating on counter-emf, inductance of the core circuit and non-linear resistance, the value of which depends on the control voltage of the converter and on the value of counter-emf). Therefore, the transfer coefficient of the non-linear element must be chosen in accordance with the equality. This drive provides approximately the same quality control speed in both continuous and interruptive current mode. However, a significant disadvantage of this electric drive is that only a proportional current controller can be used here (due to the presence of a nonlinear element in the feedback loop of the controller). The regulator's gain during drive operation with a continuous current of the converter cannot be selected greater than the U-part of the transfer function (1): In the continuous current mode, the motor current control loop will be static with an error in the current defined by the ratio cf- where T is electromagnetic after the time of the engine korotka chain. Error in the current at the real parameters of the electric drive can reach several tens of percent and leads to under utilization of the engine in the stop modes and in the start and braking modes of the drive with the maximum current of the engine, as well as to increase the dynamic error in speed. Ultimately, the presence of such an error in such an electric drive. leads to the deterioration of its static and dynamic characteristics. Such an electric drive has not found application for powerful mechanisms with high demands on the quality of regulation, for example, for the metallurgical industry. The purpose of the invention is to obtain high quality static and dynamic characteristics of an electric drive over the entire range of current and voltage of a valve converter. This goal is achieved by the fact that in an electric drive containing a valve converter, a valve control angle limiter, a current sensor speed controller, an EMF sensor, a non-linear element; and a proportional current controller whose inputs are connected to the outputs of a speed controller, sensors current, the EMF sensor and the nonlinear element, and the output of the proportional current regulator is connected to the input of the valve converter and to the input of the limiter of the angles of control of the valves, an integrated current regulator is additionally introduced the stroke of which is connected to the input of the nonlinear element, and the inputs are connected to the output of the speed regulator and to the output of the current sensor. In addition, the output of the control angle limiter is connected to the third input of the integral current controller. Since in the discontinuous current mode only the active resistance of the root depot changes, in this mode only the integral component of the current regulator needs to be changed, which is achieved by introducing an integral current regulator, the output of which through the nonlinear element is connected to the proportional current regulator.

FIG. 1 shows a functional diagram of the proposed DC electric drive; in fig. 2 is a block diagram of the electric drive: a) source, b) transformed; Fig. 3 shows the characteristics of a nonlinear element with different EMF of the converter (the solid line represents the characteristics of an ideal nonlinear element; the dotted line is simplified, with a curve approximating with three lines); in fig. 4 is a schematic diagram of a simplified version of a non-linear element.

The electric drive (see fig.) Contains a valve converter 1 supplying the engine 2 core circuit, speed sensor (tachogenerator) 3, the output voltage of which serves as a feedback signal of speed controller 4, integrated current regulator 5; acting on the nonlinear element 6 (a characteristic of which is shown in Fig. 3), proportional to the current regulator 7, current sensor 8, the output voltage of which serves as a feedback signal from current regulators 5 and 7, the EMF sensor 9, to the input of which The signals of current sensor 8 and voltage sensor 10 on the engine, limiter 11 valve control angles, limiter 12 maximum current and device 13, whose output signal is a reference to the motor speed, act. The output signal of the speed regulator 4 serves as a reference for current regulators 5 and 7, the valve converter operates without equalizing currents,

those. for reversible electric drives, it is performed with separate or with joint mismatched control.

The drive is as follows. The speed reference signal VB is supplied from the output of the driver 13 to the input of the speed regulator 4, where it is summed with the negative feedback signal for the speed Hv, which uses the output voltage of the tachogenerator 3 connected to the engine gear 2. The output voltage of the speed regulator 4 is proportional to the set value of the current i DvIatel and is the task on the current regulators 5 and 7. The maximum value of the current protection is limited by the limiter 12. At the inputs of the integral 5 and proportional 7 regulator The current is compared to the specified ij and the actual 1d current values of the motor. The output voltage of the current sensor 8 is used as a negative current feedback signal of the motor. In addition, the input of the proportional current regulator 7 is connected to a hard positive EMF voltage of the engine, formed by the EMF sensor 9. When the drive is on

0 is ideal idle when the motor current is zero, the voltage at the output of proportional regulator 7 is equal to the motor EMF (in relative units). At the output of the integral current regulator 5, a nonlinear element 6 is installed, which compensates for the nonlinearity of the characteristic of the valve converter. in the area of intermittent currents, therefore, the closed current loop is linear in the entire range of current variation of the converter. To compensate for the nonlinearity of the valve converter accurately, the auxiliary input of the nonlinear element 6 is connected to the output of the EMF sensor 9.

In order to clarify the features of the electric drive, we consider its block diagram shown in Fig. 2a. This scheme of structural transformations of lead, cysts to the form shown in Fig. 26. At the output of the regulating part of the system, a filter with a time constant T is shown. In real systems, the role of this filter can

0 perform the current sensor and regulator filters, and with no-slip elements, this filter can be implemented directly on the proportional current controller 7 (in this case, the latter is performed

in the form of aperiodic link). The speed regulator 4, depending on the requirements for the electric drive, can be applied by AND-PI type. From FIG. 2, it can be seen that in this system there are two current regulators — proportional (PT7) and integral (PT5), the integration constant of which changes (with when the operation mode of the converter changes. The constancy in all modes of the proportional part and the presence of variable the integral part of the current controller is the difference between the electric drive and the known

If we take the transfer functions of current regulators as

 T

(five)

% T7 (P - {GTTG7 (6)

then in the mode of continuous current, when the nonlinear element operates on a gentle part of the characteristic (see fig. 3 with a single transmission coefficient, the sum

 (7)

will give the transfer function (1) of the usual pi-current controller. Thus, in this mode, standard tuning and optimum transients in the drive are provided.

In the discontinuous current mode, the equivalent deceleration of the converter and the transfer coefficient of the non-linear element are determined (at any values of the load back-emf) by the relation (2) and the transfer function of the open-loop motor current control is:

 (eight)

"P -(

V .p

which also corresponds to the type of transfer function of the optimally tuned circuit. The cutoff frequency of the LAFC. Open current loop is determined by the expression

(9)

s, 1

and do not change in the entire range of current of the converter converter.

Thus, the performance of the drive will not depend on whether the valve converter works with intermittent or continuous currents.

In terms of resistance to high-frequency pulsations and interference, the electric drive is no different from conventional electric drives with subordinate control systems and has unconditional advantages: at the input

in this case, the integral current regulator with a large constant integration time Td, which is a strong filter for all high-frequency signals, is installed. In a known electric drive, all interference and pulsations are amplified in a portion of the non-linear element with a high gain factor and are fed to the input of the valve converter.

For those actuators where the speed control range is limited, the control system can be somewhat simplified: in this case, there may be no communication from the EMF meter to the auxiliary input of the nonlinear element. In this case, the characteristic of the nonlinear element is selected from the conditions for ensuring quality processes at the maximum possible motor emf. However, at low EMF of the engine, this leads to a deterioration in the quality of regulation.

If, however, the electric drive is subject to high quality control requirements in a wide range of speeds, the characteristic of the nonlinear element should vary depending on the motor's electromotive force, as indicated in Fig. 3. Without a noticeable deterioration in the quality of regulation, it is possible not to change the slope of the steep portion of the characteristics of the nonlinear element,

5, the change in the motor EMF is only the magnitude of the voltage UQ. In addition, the characteristic of a non-linear element without noticeable degradation of the regulation quality can be approximated.

0 by a broken line of three straight line segments (see Fig. 3, shown by dotted line).

FIG. Figure 4 shows a schematic diagram of one of the variants of such a simplified version of a nonlinear element. It consists of an operational amplifier 14 with an input resistor 15 and feedback resistors 16 and 17, two transistors 18 and 19, bias circuits - resistors 20-23 and a diode bridge 24. At small output voltages, transistors 18 and 19 are locked and nonlinear the element works with a large K gain, and

(ten)

N R

15

By increasing the input voltage to

pore

(eleven)

and. ate to

open transistor 18 or 19 (depending on the polarity of the input signal) and gain

non-linear element is reduced to the value of K 2, and

J

VV

R,

47

15

where r.f - collector resistance -

emitter in saturation mode

To change the characteristic of a nonlinear element depending on the motor EMF, the input of the diode bridge 24 is connected to the isolated output of the EMF sensor 9 (see Fig. 1). With an emf of motor equal to zero, while increasing the emf of the motor, Uj decreases, which leads to a change in the characteristics of the nonlinear element, as shown (dotted line) in fig 3.

The non-linear element for the non-reversible drive can be made non-reversible, t, e, will have one branch of the characteristic. For this, the output of the nonlinear element is connected to its input by means of a diode, and transistor 18 or 19 can be excluded from the circuit (depending on the desired polarity of the output signal).

To limit the control angles and the voltage of the gate converter in the subordinate control systems, a non-linear element is established in the feedback of the current regulator. A similar problem arises in the proposed drive. However, it is not possible to set the restriction on only one current controller - proportional or integral. The most qualitative regulation of the converter current at the maximum voltage of the converter will be carried out in the electric drive if the limiter of control angles is turned on as shown in Fig. 1, covering both controllers and nonlinear elegance simultaneously with the limiter

The proposed electric drive was studied on an experimental setup over the entire speed range with and and pi-speed controller during loading and dumping of the shaft, during loading and dumping of the speed reference signals, during start-ups, reverse, tsmo electric drive from the tempo generator (intensity sensor) . In all modes in the electric drive, the quality of speed and current control of the engine is high, close to optimal, and is not pecked by the usual for electric drives with separate control.

and continuous current mode limits on speed. By its indicators such an electric drive

(12) practically (with modern systems of logical switching of groups providing a pause in switching groups of not more than 0.001С) is not inferior to an electric drive with a converter with joint coordinated control, retains all the economic advantages of electric drive

0 with razdag5ny. management.

Forg.ula inventions

Claims (2)

1, an electric drive of a direct current, comprising a valve converter, a control angle limiter of the valve mz, a speed controller, the inputs of which are connected to the output of a driver and a sensor 0 speed, current sensor, EMF sensor, non-linear element and proportional current controller, the first input of which is connected to the output of the speed controller, the second input is connected 5 to the output of the current sensor, the third input is connected to the output of the nonlinear element, the output of the proportional current regulator is connected to the input of the gate converter and from 0 input limiter control angles of the valves, and the output of the sensor SDS is connected to the auxiliary input of the nonlinear element 5 ent and to the fourth input of the proportional current regulator, 5 it is also distinguishing with those that, with a cease of improving the dynamic and static characteristics of the drive, an integral current controller is additionally introduced, the first input of which 0 is connected to the output of the speed controller, the second input is connected to the output of the current sensor, and the output is connected to the input of the nonlinear element, 2. The actuator according to claim 1, 1, that is, with 5 in order to obtain high quality static and dynamic characteristics of the drive at the maximum voltage of the converter, the output of the valve control angle limiter 0 is connected to the third input of the integral current regulator, Sources of information taken by the HE in the examination 1. The magazine Technische Mitteilun- 5 gen AES-Telefunken, No. 6, 1969, p. 348-352 -2 The dynamics of the DC valve motor drive. Ed. Poe-day A, D. M ,, Energie, 1975, 0 s. 208-216. Fig1 ns PC f. YAP wa